Electron Beam Colonography Bowel Preparation

Transcription

Electron Beam Colonography Bowel Preparation Instructions**
.:. Two (2) days before procedure
Eat a low residue (low fiber) diet. Please refer to the list of foods and eat only the foods that are allowed. Do not eat any foods that
are listed as foods you should avoid.
.:. One (I) day before the procedure
Breakfast: Drink a clear liquid breakfast. Please refer to the list of fluids and drink only the fluids that are allowed.
Noon: Drink a clear liquid lunch
.:. Day of Procedure
**Preparation courtesy ofMedical College ofVirginia
Low Residue Diet
List of Foods YOu CAN EAT
.......
All milks or milk-based products
Well-cooked vegetables (potatoes and tomatoes without skins) Canned and cooked fruit White bread, crackers Eggs
Boiled, baked, or broiled chicken, beef, fish, or pork
Ice cream, sherbet, cake or pie without seeds, nuts, raisins, or coconut
Foods TO A VOW
...........
Raw or deep fried vegetables Fried meats, chicken, or fish Cold cuts, salami, sausage Dried peas and beans Skins, seeds and corn
Raw fruits All nuts
Any product that contains whole grain or bran (breads, cereals, crackers) Tough, cured, BBQ or pickled meats
Any deserts with seeds, nuts, raisins or coconut Popcorn
Clear Liquid Diet
Fluids YOu CAN DRINK
.......
Sodas (7-UP , Sprite, Orange Soda, Cola} Gatorade or Powerade
Apple, cranberry or white grape juice Ice tea
Black coffee, plain tea
Clear soups (i.e. Bouillon) Jello (not red or orange)
Fluids TO A vom
...
Milk, chocolate milk or cream Orange juice Tomato juice
Electron Beam Colonography Imatron EBT Protocol*
I. Insert rectal tube and distend the colon using room air. About 2 liters of air is required. Air is inserted until the patient reports
discomfort.
2. Acquire CT Scout film in the supine position to ensure adequate bowel distention over the entire length. The patient should be
asked to hold their breath during the scout. The same breathing instructions should be used throughout the study. The
Scout film should cover from the diaphragm through the symphysis pubis.
3. Once the bowel is adequately distended, scan the patient with a single breathold using the following parameters.
4.
a.
cvs Mode
b. 3.0 mm slice thickness
c. 3.0 mm table travel (pitch 1:1)
d. 0.2 second scan time
e.
f.
Up to 140 levels as required to cover the colon
Normal reconstruction kernel
Turn the patient over into the prone position. Reregister the patient in the prone position and perform the scout. Repeat the above
protocol using the same parameters.
5. Once the scans are completed, the images will be transferred to the Acculmage workstation for the Radiologist to review.
6.
The AccuA viator module may be used to view the 2D images in the original axial and multi-planar coronal and sagittal views.
During review, the Radiologist may choose areas to interrogate further and jump directly to that position for a full color 3D
volume rendering inside the colon. A movie of any length may be generated at any time during this process.
7. Heartscan technicians will prepare four tly-through movies of the colon. For each of the prone and supine positions a forward
and reverse movie will be prepared using standard rendering settings. The four movies plus the DICOM original image files will
be placed on a CD-ROM. A copy of this CD may optionally be shared with the patient.
8. A Radiologist report will be prepared that gives colon findings and other abdominal findings. According to the literature, up to
30% of the patients may have additional findings of significant abdominal abnormalities. The report will contain a statement that
explains we are searching for polyps of l-cm size or
~
cNEARJSCAN.
larger, which is the size that would nonnally be considered for therapeutic removal. Recent literature suggests that our sensitivity
will be around 90% for l-cm polyps and greater, but falls to 60- 70% for 5-mm polyps.
~
~
*Protocol courtesy Heartscan San Francisco
From: Sent: To: Subject:
Heartsl:8nYCprep andprotoco
Douglas Boyd [doug@imatron.com] Tuesday, March 06, 2001 3:52 PM
John Leal; applications@imatron.com; sales@imatron.com; Dave Hill RE: Colonoscopy
John,
Very impressive piece of work. I thought it was very creative to separate the two studies with into
rectum-sigmoid and the rest-of-the-colon. This allows you to use 2.5mm steps which is more competitive
with what MS-Spiral is doing.
And you only have 3 studies, not 4. So it is tempting to think about doing this.
At Heartscan we are doing 3x3 acquisition without cone-beam, 0.2sec. This allows coverage of the entire
colon and rectum for most patients in one scan with 140 slices. The image quality is very good, and I
doubt there is much to gain from going to 2.5 mm steps, especially if you are also blurring the z-axis
resolution by using cone-beam. I don't think overlapped scans helps the workstation to do 3D-- at least in
the Accuimage case, the z-axis is resampled with subslices using cubic interpolation, so this will not
help.
I attended the sessions at the ECR on CT-colonoscopy last week, and didn't see anything done by MS-Spiral
that we don't do just as well. Most of the speakers are not using CO2, just air. They fill the colon until
the patient reports some discomfort. The ECR papers showed that scanning prone and supine allowed more
segments of the colon to be inflated. Those that are not inflated supine show up in prone, etc. Further,
residue stool may fall to the other side. So I guess we are stuck with the two scans.
John, I do have one question. prone position??
--Doug
What do you do for very tall patients, especially in the
P.S.
I am attaching the Heartscan Protocol.
Email: doug@imatron.com Efax: 603-737-8330 Tel: 650-827-7703 Cell: 650-218-9405 Home: 650-347-2390 Web:
dboyd.com
Original Message From: John Leal [mailto:jeleal@surfside.net] Sent: Tuesday, March 06, 20011:53 PM
To: applications@imatron.com; sales@imatron.com; Dave Hill; Doug Boyd Subject: Colonoscopy
Greetings,
Last Saturday Philip Chang and I had the opportunity to perform colon
1
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studies with the group at Irvine. I think we were very successful overall, although there are still some
issues that will need to be addressed. Here is the written result of what we did. I would like to
standardize this protocol for colon studies and any responses and or concerns would be appreciated. Thanks
John
~
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~
~
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~
2
From: Sent: To: Subject:
John:
David Hill [dgh@imatron.com]
Wednesday. March 07. 2001 9:23 AM
John Leal; applications@imatron.com; sales@imatron.com; Doug Boyd Re: Colonoscopy
I thought that this was an excellent write-up; thanks for doing it
If you still have some of the raw data, it might be useful to re-process the 5 mm cone beam as non-cone
beam and compare the quality of the resulting scans. They will be 3 mm slices every 2.5 mm but should be
noisier than the original cone beams. I believe in cone beam as a matter of principle, but I don't really
know how much the image quality in the colon is affected.
I attended at ECR some colon talks other than the ones Doug heard, and agree with his assessment that we
are doing much the same thing. I also heard both supine and prone scans for every patient. One person who
does a lot of colons suggested doing fly-throughs only in regions where there is
confusion; he and his radiologists were comfortable reading the original scans and doing some MPR's
Dave
Original Message From: John Leal <jeleal@surfside.net>
To: <applications@imatron.com>; <sales@imatron.com>; Dave Hill <dgh@imatron.com>; Doug Boyd
<doug@imatron.com> Sent: Tuesday, March 06, 20011:53 PM Subject: Colonoscopy
> Greetings,
> Last Saturday Philip Chang and I had the opportunity to perform colon > studies with the group at Irvine. I think we
were very successful > overall, although there are still some issues that will need to be
> addressed. Here is the written result of what we did. I would like to > standardize this protocol for colon studies
and any responses and or > concerns would be appreciated. > Thanks > John >
1
Colonoscopy
Recent review ofvarious study protocols:
Colonography
CVS Cone Beam 3mm Collimation
5mm Slice Thickness 2.5mm Table Motion 140 slices
Exposure time 0.2 -0.4 seconds Table d irection OUT Reconstruction Normal FOV = 40 -45
Sigmoid
3mm Slice Thickness 1.5mm Table Motion 70-100 slices
Exposure time 0.2- 0.4 seconds Table direction OUT Reconstruction Normal FOV= 35 -40
Four patient studies were performed. Each patient was in the 45 to 55 year old age group. 3 males and 1 female patient. Patients were at moderate risk by ACS
guidelines with only one patient complaining of changes in bowel habits. There were no histories of polyps or cancers reported. One patient had recently
undergone a Barium Enema, but the results were not available at this time.
Patient 1 received EZ-Em 24 hour prep Patient 2 received Go-Lytly prep Patient 3 received EZ-Em 24 hour prep Patient 4 received Go-Lytly prep
Both preps prepared the patients adequately for the exam with little to no residual material. Patient # 4 had a difficult time with the Go -Lytly and was not able
to complete the prep. The patient complained of vomiting and cramping after drinking the first half of the prep. This is not uncommon with this prep. The
patient was given a suppository the morning of the exam. Using the newer versions of Go -Lytly that are flavored and have lower salt content, Nu-Lytly is one
such product, is recommended.
Each patient received a variation of Co2 or Room Air as the colon contrast for the exam. For the Co2, a small tank was connected to a standard double contrast
Barium Enema bag with a "Y" connector tube. The "Y" tubing was then connected to a blue EZ -Em Insuftlator pump so that hand pumping could be employed
to introduce the Co2 into the patient. The blue pump was connected to a standard balloon enema tip. The Co2 tank was used to fill the Enema bag with Co2.
After clamping off the Co2 tank, the pump was used to move the Co2 from the bag into the patient.
Patient 1 : The patient was placed on his left side while the enema tip was inserted into the rectum and the balloon was inflated. In this position the patient
received 20 blue Insufflator pumps of Co2. The patient was then rolled to the right and 20 more pumps were performed. The patient was placed on his back
(supine) and a Preview scout was performed. The Preview was marked for position and the study was performed using the protocol listed above using the 0.2second exposure time. Just prior to scanning, 10 more pumps of Co2 were given to the patient. After the first image set was acquired, the patient was rolled
onto his stomach (prone) and another scout was performed. The scout was landmarked and the study was performed again using the above protocol. Finally a
third study was performed in the prone position imaging the Rectum and Distal Sigmoid Colon using the 3 x 1.5 mm ConeBeam protocol.
Although this patient was the most anxious of all the patients, he tolerated the exam very well with complaints of moderate cramping. Coincidentally, he was
also the only patient to exhibit colon spasming on both the prone and supine images. The Co2 absorbs relatively quickly and did not provide as much distention
as we would have liked for the study. It is unknown if the patient would have responded better to a mixture of Co2 and air. Both the patients who received a
mixture of air and Co2 tolerated the exam better than the patients who received either pure Co2 or room air. This may also be due to other factors including the
anxiety level of these patients.
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Patient 2: This patient received the same general study as patient 1, with a couple of changes. A combination ofCo2 and Room Air was used to insufflate the
patient. Initially, as with patient 1, patient 2 received 40 pumps ofCo2. The tubing was then disconnected from the Co2 tank and 10 more pumps of room air
were introduced into the patient. The supine portion of the exam was perfo rm using the protocol listed above, as this patient was considerably larger than
patient 1, the 0.4 second exposure time was used. Prior to scanning the patient in the supine position the balloon on the enema tip was deflated, but the tip was
left in the p atient. The balloon was re -inflated prior to turning the patient onto his stomach for the prone series. In the prone position, as with patient 1, Patient
2 received an additional 20 pumps of room air after the Preview scout was performed. Just prior to scanning the patient in the prone position the balloon was
deflated, but the tip remained in the patient. The same protocol was used for the prone study. Finally for the rectum and sigmoid study the patient was also
scanned using a Cone Beam 3xl.5mm protocol. Just prior to scanning the patient received 10 more pumps of room air and then the enema tip was removed
entirely.
The patient tolerated the study very well with no cramping or spasming reported. There was adequate distention of the bowel for the exam.
Patient 3: This study was perfonned similar to Patient's land 2. The patient receive primarily Co2 prior to being scouted and then another 20 pumps of room air
prior to scanning in the supine position. The balloon tip was also deflated prior to scanning. The patient was turned into the prone position and did not receive
more room air. The tip was removed prior to the prone exam. The resulting prone study was not adequately distended and the Co2 was almost complete
absorbed by the time the prone study was done. Both studies were perfonned using the above protocol with the 0.2second exposure time.
The patient tolerated the study and the prep very well with no complaints of cramping or abnormal discomfort. The supine study was adequately distended
using the combination ofCo2 and room air, but the prone study was inadequately distended and the resulting exam was sub-optimal.
Patient 4: This patient had the most difficult time with the prep and the exam overall. The patient was insufl:lated with only room air. The patient received 50
pumps of room air prior to scouting. The supine exam was performed with the above protocol using the 0.4-second exposure time. Colon distention was
excellent and the balloon tip was deflated just prior to scanning. In this patient the splenic flexure was
quite high and rather than increase the slice thickness and table motion, we opted to begin the study in the mid sigmoid area, cutting off most of the rectum in
this position. Once the patient was turned and scouted for the prone study, 20 more pumps ofroom air were introduced and the tip was removed. The prone
study was performed with the same protocol and a rectum and sigmoid 3xl.5mrn study was also performed at the end of the exam.
This patient had a difficult time with the p rep and although there was no cramping or spasming exhibited on the images, the patient felt very full following the
exam. The room air does not absorb like the Co2 and while it provided much better distention of the colon than the Co2 did, but there appears to be more
discomfort associated with the room air.
All the images were reviewed by a group of 3 experienced radiologists from the Moran Rowan and Dorsey group in Orange California and 1 gastroenterologist
who regularly performs colonoscopy. All the radiologists felt the image quality and slice thickness was more than adequate for the exam. This particular group
of radiologists is very experienced with the Siemens multi-detector Volume Zoom system. They have recently begun to review EBT images for the Irvine
facility and have remarked on the excellent image quality of the EBT system for lung and abdominal imaging. This group will also be reading for the new
Orange facility operated by Vital Imaging. There are some issues that came up with regards to the interpretation of the colonography studies. These issues will
need to be addressed by all facilities performing this exam.
?
I.
The data set for the colonography includes images of most of the abdomen. This includes parts of the liver and spleen and well as kidneys, pancreas etcetera.
The responsibility for these images rests with the radiologists, who will be required to read, not only the colonography, but also the axial abdominal images as
well. Since the entire abdomen is not completely visualized, a separate abdominal screening study will need to be performed prior to the colonography exam
and read as a separate study. This requires a separate charge that ultimately goes to the patient. Each facility will have to decide whether to bill this
independently or include it in the overall price of the colonography. Ifbilled separately, the 2 exams will cost a total of about $1400, $600 for the abdomen and
$800 for the colon. If you decide to include the abdomen in the overall price of say $800-900 dollars, the radiologists will still want to be paid for 2 separate
studies. Some centers will opt to inform the patient and have them sign a waiver for the abdominal images, but historically the waivers do not hold up in court
and the radiologist may still insist on reading the abdominal images. Ultimately it will be up to each individual center to decide how to handle this issue.
2. Reading the colon studies right now is a time consuming process. Even the most experienced readers may spend 30 minutes on one colonography exam. We
can have the technologists provide much of the pre -processing of the images, but first we have to know what the interpreting radiologist wants to see, and right
now they don't know what they want. This makes is impossible to reduce the reading time to a more appropriate 10 minutes. It is apparent that a workstation
must be available for the reading of these exams. For centers with only one workstation, they will be hard pressed to allow this amount of time for the
workstation to be unavailable for image processing.
3
In the AccuImage workstation neither the Projector program nor the Scope program is exactly perfect for reading the colonography studies. The projector
provides the 3 standard reconstruction planes, but not at the same time. The Scope program provides the 3 planes, but the camera gets in the way and additional
keystrokes are required to view the same area in all 3 planes. The Axial Sagittal and Coronal planes must be presented in large windows with the corresponding
area of interest projected and tracked in all three planes simultaneously. Fly throughs can be generated
for suspected lesions. A program that would segment the colon into, say 6 segments, straightening and then splitting the colon in halves may be one way of
speeding up the reading process.
Impression:
Our protocol utilizing the ConeBeam with 3mm collimation and Smm slice thickness provides excellent image quality with adequate coverage for the
colonography exams. Co2 alone seems to absorb to fast and does not provide better distention than room air. Pure Co2 may not be more comfortable for the
patients and appears to require more volume than room air. Pure Co2 also seems to h ave a greater potential for providing a sub-optimal exam. Room air alone
or in combination with Co2 may provide the best solution with a 2 to 1 mix of air to Co2. The exam requires at least 2 acquisitions, one prone and one supine.
This will provide covera ge for areas obscured by air fluid levels in the colon and will help to define spasms versus apple core tumors. The balloon on the
enema tip should be deflated prior to acquiring the images in both views if possible and removed entirely if there is to be a separate sigmoid study. The inflated
balloon blocks the view of the rectum where the incidence of polyps is statistically higher. The colon in the prone view is foreshortened and may require fewer
images than the supine view. The slice thickness in the prone view may be decreased to 4mm in some cases. The total patient time is about 30 minutes. A
bathroom close by is needed and if possi\>le it should be well away from the center population. One patient expressed self-consciousness while using the
restroom where he thought others might hear, there is a lot of gas being released and patients don't want to walk out of the bathroom and into a room full of
people. The biggest obstacle will be the reading of the exams and providing a report in a timely manner. The radiologists reading these studies will require a
second workstation with the proper plugins.
1
Colonography Recommendation:
PROTOCOL: Colonography
5mm Slice Thickness 2.5mm Table Motion 140 slices
Exp osure time 0.2 -0.4 seconds Table direction OUT Reconstruction Normal FOV = 40 -45
Sigmoid
3mm Slice Thickness 1.5mm Table Motion 70-100 slices
Exposure time 0.2- 0.4 seconds Table direction OUT Reconstruction Normal FOV = 35 -40
Patient Preparation:
Either the 24-hour EZ -Em or Fleets kits will provide adequate bowel cleansing. Go -Lytly and Nu-Lytly are very effective bowel preps, although somewhat of a
harsher experience. This prep is started in the late afternoon the day before the exam and may be more convenient for some patients.
Colonography should be scheduled in the morning, if at all possible, as the patients are required to be NPO prior to the exam. Small amounts of water
consumed the morning of the exam will not affect the exam and the patients can take their normal medications the morning of the exam. Non-prescription
medication and vitamins should not be taken the morning of the exam.
Patient gowns will need to be provided, as the patients must completely disrobe for the exam.
Patients should expect to spend at least 1 hour at the facility and may not feel up to returning to their regular schedule for 1 to 4 hours after the exam. Some
cramping is to be expected and since the laxatives in their systems will still be in affect, they should have immediate access to a restroom for the rest of the day.
Unless otherwise directed patients can resume normal eating after to the exam.
Supplies:
Prep kits are noffilally provided by the facility perfomIing the exam. Prep kits are available from many suppliers and pharmacies.
Single contrast Balloon enema tips are recommended. Blue Insufllation pump
5/16th Tubing or GI barium straws Christmas tree adaptors
Double contrast enema bag or other reservoir if Co2 is used Y connector for Co2 tank to enema bag. Clamps KY jelly
Patient gowns
Glucagon does not appear to be necessary for the exam and should not be part of the regular procedure. In instances of extreme cramping Glucagon can be
used, but this will cause the small bowel to fill as well and may obscure the large colon.
Exam:
With patient lying on right side, insert the enema tip and inflate colon with 20 pumps of room air from the insuffiator. Roll patient to left side and perform
another 20 pumps ofroom air. Place the patient in the supine position and center in the scanner for a Preview scout. Move the patient all the way into the
scanner with the table height at 175 or above. The patient's head should be within a couple of inches of the beam stop. Perform the Preview with the table
moving out. Preview the patient to include from pubic symphysis
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to diaphragm, approximately 400mrn. Landmark the Preview and set up the protocol for the first study. The study is acquired imaging from the pubis to the
flexures moving the table out. Be sure to check the scout for adequate distention of the colon. At this time another 10 pumps of room air or Co2 can be
performed. Prior to the supine acquisition the enema tip balloon should be deflated. In some cases while imaging the patient in the supine position it will not be
possible to cover the entire colon with the 2.5mrn table motion and the 140 slice limit. In this case one of two things can be done:
2.
Increase the table increment to 3mm; this will change the slice thickness to 6mm. ConeBeam is not absolutely necessary for performing the exam, but it does
provide advantages in image quality so it is desirable to use it, however overla pping 4 by 3mm non-ConeBeam could also be used if the 6mm slice thickness is
an issue. In all cases, overlapping slices will provide better rendering than non-overlapping or contiguous slices.
Start the scan in the mid rectum or sigmoid and be sure to cover splenic flexure. The sigmoid and rectum can then be imaged separately in the prone position
using thinner slices with the tip removed. There may be an issue with fluid levels in the rectum so be sure to check with the radiologist before performing the
exam this way. Typically the rectum is imaged in the prone position because fluid should run away from the rectum and distal sigmoid in this position; fluid
obscuring small polyps should not be an issue. Another option is to perform the rectal sigmoid study in the supine view after the prone study, but fluid will
accumulate in the rectal-sigmoid junction is this position. In this case the rectum must be included in the prone position study.
After the supine study is finished, re -inflate the balloon tip prior to turning the patient over, this will kept the tip from coming out while the patient is moving.
Once the patient is in the prone position set up to Preview the patient, don't forget to change the patient orientation in the scan menu. This will be done the
same as the supine study, starting at the pubis and moVing out. Perform the Preview and landmark the
study. Check the image for bowel distention. At this point another 10 to 20 pumps of room air or Co2 may be required. IfCo2 is being used then another 10 to
20 pumps will definitely be needed, room air may require less pumps. After re -inflating the patient, set up the scanner for the next run. Prior to this acquisition.
remove the enema tip entirelyand instruct the patient to try not to let any of the gas out. Perform the prone study and then immediately set up for the last run.
Move the patient all the way back into the starting position and image the rectum and sigmoid using the 3xl.5mm protocol.
The patient can now be removed from the table and sent to the restroom. You can expect the patient to spend the next 5 to 15 minutes in the restroom;
don't forget to check on them, as a Vaso-Vagal reaction is still a possibility at this point.
Interpretation:
Colon images are read using the Axial, Sagittal and Coronal views. Edited VRT images presented in a standard Barium Enema sequence may be of some use.
Fly through images of the entire colon in both supine and prone positions will need to be generated and saved as A VI files for later review. Fly through images
of specific areas of interest may also be required.
~
Electron Beam Colonography Imatron EBT Protocol*
1
Insert rectal tube and distend the colon using room air.
2. Acquire CT Scout film in the supine position to ensure adequate bowel distention. The patient should be asked to hold their
breath during the scout. The same breathing instructions should be used throughout the study. The Scout film should cover from
the diaphragm through the symphysis pubis.
4.
a.
cvs Mode
c. 3.0 mm table travel (pitch 1:1)
d. 0.2 second scan time (optional 0.1 seconds for lower dose)
eo
f.
Up to 140 levels as required to cover the colon
Normal reconstruction kernel
Turn the patient over into the prone position. Reregister the patient in the prone position and perfOml the scout. Repeat the above
protocol using the same parameters.
5. Once the scans are completed, the images will be transferred to the AccuImage workstation for the Radiologist to review.
6.
The AccuA viator module may be used to view the 2D images in the original axial and multi-planar coronal and sagittal views.
*Protocol courtesy Heartscan San Francisco
Virtual Colonoscopy Spiral CT Protocol**
7.
Insert rectal tube and distend the colon using room air.
8. Acquire CT Scout film in the supine position to ensure adequate bowel distention. The patient should be asked to hold their
breath during the scout. The same breathing instructions should be used throughout the study. The Scout film should cover from
the diaphragm through the symphysis pubis.
a. Helical or Spiral mode
c. 3.0 mm table travel (1:1 pitch; increase if necessary for coverage)
d. 120 kVp
e.
f.
120-150 mA
1.0 second scan time (or less ifsub-second scanning is available)
g. 1.5 mm reconstruction for overlap
10. Turn the patient over into the prone position. Reregister the patient in the prone position and perform the scout. Repeat the
above protocol using the same parameters.
11. Once the scans are completed, the images will be transferred to the Acculmage workstation for the Radiologist to review.
12. The AccuAviator module may be used to view the 2D images in the original axial and multi-planar coronal and sagittal views.
** Protocol courtesy Medical College ofVirginia
Comparison: EBT vs. Spiral
EBT
Slice Thickness
3mm
Slice Spacing
3mm (CVS)
Scan Time (slice)
0.1-0.2
Number of slices
140
Distance covered
42cm
Scan Time procedure (breath-holding)
14-28 seconds
Tube Technique
130kV 640mA 64-128mAs
A vg. Skin Dose
0.6-1.2 Rad
Spiral-Helical
3mm
3mm (pitch 1: 1 )
.5-1.0 sec
140
42cm
70-140 seconds*
120kV 150mA 75-150mAs
1.0-2.0 Rad
*Newer quad-spiral scanners are up to 4X faster and can complete the study in a realistic breath-hold. Older spiral scanners
require several breathing intervals.
Scientjfic Sessions 10:30-12:00
~~m~a~;d ~astrointestinal / I % 7 ( D Jr- , CT/MR colonography -./' -q
Chairpersons: ~ J 71 b J f".i ""'- A.R. Gil/ams (London/GB) I ,- / J
D. zur Nedden (Innsbruck/A1) 7 O J 6 C; i-"'--
eff.thk 1.4 mm) -the volumes were calculated with manual contouring from crura of fornix to the level of mammillary bodies. All patients underwent at least one EEG.
Results: Conventional MRI revealed relevant findings in 10 patients (26.3 %). MR volumetry revealed asymetry of hippocampi greater than 5 % in 22 cases (57.9 %). In patients with normal MRI (28 cases) asymetry of
hippocampi greater than 5 % was revealed in 18 cases (64.3 %). The combination of conventional MR and volumetry revealed changes in 28 patients (73.7%).
Conclusion: Results of this study show that sensitivity of MRI completed with measurment of hippocampal volume is greater than only conventional MRI.lt seems that in many cases slightly decreased volume of
specific cortical region is the only manifestation of epileptic lesion. Combination of hippocampal volumetry, MRI and other neurodiagnostic methods (EEG, SPECT, PET) allow to evaluate etiology of epilepsy and to
lokalise epileptic lesions more precisely.
B-0324 11 ;40
Lateralization with MRSI in patients with temporal lobe epilepsy S.E. ~, B. Vikhoff-Baaz, K. Malmgren; GofhenburglSE
Purpose: 'H MA spectroscopy ('H MAS) may contribute to the lateralization of
the epileptic focus in temporal lobe epilepsy (TLE). The aim of this study was to investigate if metabolite concentration images from MASI measurements could be used for lateralization of TLE patients.
Materials and methods: Nine consecutive TLE patients evaluated for epilepsy surgery, and nine neurologically healthy, age-matched volunteers were examined with MASI. The volume-of-interest (VOI) was angled
along the temporal horns in transverse and sagittal images, and symmetrically over the temporal lobes in coronal images. The metabolite concentration images of NAA and Cho + Cr were used for lateralization. Two
methods for evaluation were compared: visual analysis of the images, and analysis from AOls located in different positions, where the side-to- side differences of the NAA/(Cho + Cr) ratios were used for lateralization.
The results from lateralization were compared with findings from the presurgical evaluation.
Results and conclusion: The metabolite concentration images were found useful for lateralization of TLE. Visual analysis can with high accuracy be used as routine evaluation. AOI analysis provides a useful tool to
quantify the changes, which gives more quantitative information about the spatial distribution and the degree of signal loss.
B-0325 11 :50 Amobarbital uptake (AmU) in the hippocampus is not critical for memory performance during Wada test. 94 hemispheres evaluated with ""TcHMPAO SPECT and angiography (DSA) A. Piotrowski', H. Klemm2, H. Urbach2, M. Kurthen2, H.J. Biersack2, C.E. Elger2, L. Krolicki'; 'Warsaw/PL. 2Bonn/DE
Objectives: Amobarbital uptake (AmU) in the whole hippocampus was considered to be a precondition for transient memory impairment during Wada test. Its grade has a prognostic importance for patients
undergoing panial temporallobec- tomy. This study aimed to investigate both with DSA and SPECT study the rela- tionship between AmU in the hippocampus ('fetal' configuration of PCA) and grade of memory deficit
during non-selective intracarotid amobarbital procedure (IAP). Methods: 94 hemispheres in forty-seven patients (mean age: 29.9 a) were investigated. After completing of DSA study 200 mg amobarbital and 1 mCi
""Tc-HMPAO were co-injected without catheter repositioning. SPECT study was performed with high-resolution y-camera. Memory assessment included 'pre-intra' and 'intra-post' memory testing.
Results: The hippocampal AmU was revealed with SPECT study only in 13/94 (13.8 %) hemispheres. DSA study disclosed 'fetal' configuration of PCA in 17/94 hemispheres. Both methods did not reveal any correlation
between AmU in the hippocampus (or 'fetal' configuration of PCA) and grade of verbal and non-verbal memory impairment irrespective of the side of amobarbital injection. It was true both for 'pre-intra' (p > 0.26) and
'intra-post' memory testing (p > 0.24).
Conclusion: AmU in the whole hippocampus seems to be not necessary condi- tion for valid assessment of memory during IAP. Most of the entorhinal and perirhinal conex and the anterior part of the hippocampus
are irrigated by ICA injection via anterior choroidal artery. Recent neuroanatomic studies have emphasized that not only the hippocampus but also related conical stuctures (e.g. perirhinal, parahippocampal and
entorhinal cortex) are critical for memory performance.
8-032610:30
Protocol optimization for multislice CT colography A.R. ~, R. Bhardwaj, W.R. Lees; London/GB
Purpose: Recent published figures for sensitivity of virtual colonoscopy were 75 0/0 for polyps > 10 mm, 660/0 for polyps 6- 9 mm, 450/0 for < 5 mm. Multislice technology with improved spatial and temporal
resolution should improve accuracy. This study aims to identify the optimal protocol whilst keeping radiation dose to a minimum.
Methods and materials: Multiple polyps ranging in size from 4- 13 mm were created within a fresh, cleaned, ex-vivo segment of pig's colon. Surgical sutures were used to produce polyps of different size and shape.
The colon was distended and anchored within a water bath and multislice CT (Lightspeed Advantage, GE) performed. Acquisitions were made at 1.25, 2.5, 3.75 and 5 mm collimation using pitch from 1.5 -6 and both
HS and Ha algorithms. The water bath was rotated through 900 and 4 acquisitions repeated. Overlapping slices were reconstructed and 3D data sets interrogated using commercially available virtual colonoscopy
software.
Results: The best compromise between dose and image quality lay with HS acquisition of 2.5 mm with table speed of 15 mm (pitch 6) or an Ha acquisition with 3.75 mm collimation at table speed 11.25 (pitch 3). The
reduced pitch lessens Z directional. All polyps were detected on all sequences, but the 3- 4 mm polyps were hard to identify on the 5 mm acquisitions even at pitch 1.5 and Ha mode. 1.25 mm collimation was optimal
but not necessary.
i
Conclusion: The optimal balance between accuracy, artifact and rad
.~ion dos71 -A was a 3.75 mm collimation with pitch 3 a"J~ H?l::!Orithm. IL. f / (/V~ ~~"'D n.o. 7>
8-032710:40 ..,-~ ~
CT colonography-bowel wali visualisation and impact of scanning In supine and prone positions
M.H. Svensson, E. Svensson, M. Hellstrom; GothenburglSE Purpose: The aim was to evaluate the impact of supine and prone scanning on the degree of bowel wall visualisation at CT colonography.
Methods and materials: After bowel preparation, 111 patients underwent CT colonography in the supine and prone positions. The quality of air-distension, degree of fluid redistribution between supine and prone
scans, possible influence of stool and degree of overall colon visualisation were evaluated using scales. The depth of fluid levels was also measured.
Results: The entire colon was air-filled in the supine and prone positions for 18 0/0 and 46 0/0 of the patients, respectively. All patients had intraluminal fluid and 70 patients had residual stool. On combination of supine
and prone datasets, for all colon segments except the sigmoid, 95 -99 0/0 of the patients had complete air- filling, and except in the ascending colon and caecum, intraluminal fluid was completely redistributed in at
least 90 0/0 of the patients. On overall evaluation, 30 patients (270/0, n = 110) had complete visualisation of the colon wall and 52 (470/0) had subtotal visualisation affecting one or two colon segments and/or "partly
dis- turbing" stool.
Conclusion: Supine and prone scanning allowed redistribution of intraluminal fluid and air, which was necessary for complete visualisation.
B-0328 10:50
CT colonography (virtual colonoscopy) is preferred to conventional colonoscopy
M.H. Svensson, E. Svensson, M. Hellstrom; GothenburglSE
Purpose: The aim was to prospectively evaluate patient-acceptance of CT
colonography and conventional colonoscopy concerning the factors of impor1ance in the patients' preference for examination.
,
Scientific Sessions
Methods and materials: Questionnaires were administered to 111 patients undergoing CT colonography followed by colonoscopy. Problems associated with each examination were evaluated on self-rated scales, and
after completion of both examinations the preference for examination was evaluated by comparative questions.
Results: Of the patients with a preference, 69% (p = 0.002) considered the colonoscopy to be the most difficult examination in overall terms, and 82 % would prefer CT colonography (p < 0.0001 ).
Among 108 patients with an opinion on both examinations, 54 % graded pain higher after the colonoscopy than after the CT colonography (p < 0.0001 ). The CT colonography was not painful according to 62 patients
and fairly or very painful according to six. Most patients (86 %) reported discomfort from air-filling during CT colonography and 80 % preferred scanning in the supine position.
Conclusion: CT colonography was less painful than colonoscopy and was the preferred examination. Discomfort from air-filling of the colon was the major problem associated with CT colonography, but pain seemed
to be decisive in the choice of examination.
8-033111:20
3D MR colonography after exclusive Intravenous administration of a hepatoblliary contrast agent
M. V. JSllQpp'2, F.L. Giesel', H. von Tengg-Kobligk', J. Radeleff'; 'HeidelberglDE, 2Bethesda, MD/US
Purpose: Cross-sectionallmaging of the colon has been recently introduced as CT or MR colonography. All methods rely on the aboral or oral administration of a contrast agent, which does change the physiological
function of the colon.
Method/materials: While performing studies using a panlally hepatobiliary ex- creted contrast agent (reponed 2- 4 %), Gd-BOPTA (Multihance, Bracco) we noted substantial colonic contrast 24 h pi. We subsequently
performed a prospective study at 0.1 mmoVkg bw In six volunteers to determine the intensity and extend of hepatoblliary excretion and detectable gastro-Intestinal enhancement at 1, 12, 24, 36, 48,70, and 105 h post
Injection. No funher preparation of the subjects was done.
Results: Intense, homogenous contrast enhancement within the colon was observed within 24 h in all subjects. The bowel stools revealed homogenous en8 0329 hancement within the lumen indicating thorough mixing of content comparable to
-11 :00 bile acids. The signal intensity of the liver parenchyma and within the gallbladder Assessment of colorectal cancer with contrast-enhanced CT colonoscopy decreased after the first hour with an Initial halftime of
10 -15 h. The highest sig- after an incomplete flberoptic colonoscopy nal intensity in the colon was detected at 16 -50 h post injection. The quality of E. ~, P. Giusti, L. Battolla, P. Boraschi, P. Rondlne, P. Vagli, F.
Falaschi, enhancement was sufficient to enable 3D processing for vinual colonoscopy.
D. Caramella, C. Banolozzl; PisallT Conclusions: We established the feasibility of MR colonography using only an Purpose: We aimed to evaluate the Impact of pre-operative contrast-enhanced intravenous MR
contrast agent with partial hepatobiliary excretion. This new diag- CT colonoscopy (CE-CTC) after Incomplete flbreoptic colonoscopy (FC) In the nostic procedure will enable not only morphologic assessment of the
colon, but assessment of patients with clinical suspicion of colorectal cancer. also patho-/physiological studies on the transport kinetics of bile and stool without Method and materials: Thirty-four patients presenting with
distal occlusive any preparation of the patient.
colorectal carcinoma identified at FC, were prospectively evaluated with CE-CTC. In all cases FC failed to explore the proximal colon. All patients underwent surgery. 8-0332 11.30 Contrast enhanced CT study was
performed after pneumocolon in the prone and .
supine position and CE-CTC was obtained with perspective surface rendering. Fecal tagging In MR-colonography Results: CE-CTC demonstrated 39 colorectal neoplasms, located in the sigmoid T. Lauenstein, S.G.
Ruhm, D. Schoenfelder, S. Bosk, J.F. Debatin; Essen/DE colon (n = 16), descending colon (n = 13), splenic flexure (n = 3), transverse colon Purpose: Colon cancer continues to be the second most common cancer.
The (n = 3), hepatic flexure (n = 2) and ascending colon (n = 2). Five lesions were syn- apparent failure of colonoscopy screening reflects limited patient acceptance. Pa- ~hronous cancers and contrast enhanced
abdominal CT allowed the detection of tients are fearful of the pain associated with colonoscopy, and are put-off by the hepatic metastases in 9 cases. CE-CTC findings were all confirmed at surgery. On unpleasant
protocols required to clean the colon. We evaluated different means to the basis of CE-CtC findings, the surgical approa<;h was changed to a total colec- obviate the need for colonic cleansing prior to MRcolonography.
tomyjn the 5 cases with synchronous cancer and intra-operative metastasis re- Materials and methods: Three volunteers received standardized low fiber meals section was performed in 7 cases, by hepatic
segmentectomy in 5 and thermal laced with 15 ml 0.5 molar Gd-DOTA, 2 g lactulose and 0.4 g dimeticon. As a con- ablation in 2. trol a fourth volunteer ingested the same meals without the paramagnetic con-
Conclusion: CE-CTC is superior to FC in the pre-operative assessment of trast. All volunteers were imaged the following morning. Stool samples were col- colorectal cancer, since in a single session it detects
synchronous cancers and lected before and up to two days after the experiment. Subsequently 5 volunteers provides a liver study for accurate mapping of metastases.
Jwere assessed after filling the colon with unenhanced water. These volunteers r ~ 1 ~ :1 ~ had been given an oral contrast agent (Micropaque, Guerbet) to assure dark stool.
8-0330 .6-t7 G? "\( .~ / r ~ ~ , ' The colon of all examined volunteers was examined with a fast T1-weighted 3D 11.10 ~.'#J L, ., I' ". GRE sequence. The second set of volunteers were
examined following the adVirtual colonoscopy In detection of colorectal potyps and ca~lIoma: A ministration of intravenous contrast paramagnetic contrast (Gd-BOPTA, comparison with conventional colonoscopy
0.2 mmol/kg).
A. Q!Q, A. Deger, V. Gelebek, B. Oguz, B. Sivrl, E. Ozarslan, A. Baykal, Results: Both methods resulted in the ability to assess the colonic lumen without 0. Akhan, A. Beslm; AnkaralTR
prior colonic cleansing. Administration of Gd caused bright stool, which was indis- Purpose: To compare the efficacy of vinual colonoscopy in detection of colorectal tinguishable from the
Gd-containing enema, thus permitting an unhibited fiy -through. polyps with conventional colonoscopy in patients at high risk of developing colorectal The administration of Micropaque on
the other hand caused dark stool, which cancer. became indistinguishable from the water enema on T1-weighted images. Method and material: Virtual colonoscopy was performed on the
same day fol- C.Onclusion: Vir.tual colonoscopy without p:ior COIOni~ cleansing is feasible. Tag- lowing conventional colonoscopy in 29 patients at high risk of developing colorectal glng
the feces wIth oral Gd-DOTA or oral Mlcropaque IS well tolerated. cancer. Patients were scanned both prone and supine. Intravenous contrast was administered prior to prone scan.
Axial, 2D MPR and 3D colonoscopic images were Interpreted by two radiologists for localization, number and size of detected polyps. Results of vinual colonoscopy and conventional
colonoscopy were com - pared individually for each polyp.
Results: Seventeen of 21 endoscopically proved polypoid lesions were detected in vinual colonoscopy. Sensitivity of vinual colonoscopy for all polyps was 81 %, for polyps greater than
10 mm was 92 %, for polyps between 6 and 9 mm in diam - eter was 75 % and for polyps smaller than 5 mm in diameter was 50 %. In adenomatous polyps, sensitivity of virtual
colonoscpy was 81 %, in adenocarci- noma it was 100 % and in hyperplastic polyps it was 66 %. Proximal colon of two patients, which could not be evaluated with conventional
colonoscopy due to distal obstructing lesion could be successfully evaluated by virtual colonoscopy.
Conclusion: Vinual colonoscopy is found to be a sensitive and comparable method to conventional colonoscopy in detecting polypoid lesions In patients at greatest risk of developing
colorectal cancer especially for the polyps greater than 10 mm. Virtual colonoscopy also provides evaluation of proximal colon in distally obstructing lesions.
B-0333 11"40
Multi-planar MA colonography for assessment of colo-rectallesions W. ~, H. Ringl, C. Osterreicher, A. Ferlitsch, E. Schober, A. Maier, A. Schoefl, R. Poetzi; Vienna/AT
Purpose: To evaluate the diagnostic yield of multi-planar MR colonography (MRC) for detection of colorectallesions.
Method and materials: MRC was performed in 15 patients following an enema with 21itresof Ringer's solution, spiked with Gd-DTPA-BMA (1 :100). Aflerfillingto the caecum, a breath-hold T1 w 3D-GRE sequence (TR
4.6, TE 1.8, matrix 200 x 512) was performed in the coronal plane in supine and prone positions and in the axial plane, covering only the rectum and sigmoid colon. Results were cor-
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Results: MAC detected 80 0/0 of polyps > 10 mm, and 33 0/0 of the polyps 6 - 10 mm, but none of the polyps S 5 mm. Assessment of coronal supine images alone revealed in 93 0/0 of patients colonic segments which
could not be evaluated due to stool and/or air bubbles. Combination of supine and prone acquisitions allowed evaluation of all colonic segments in all patients. Addition of axial MAC images improved assessment of
the sigmoid colon in 53 0/0.
Conclusion: Multi-planar MA colol'1ography performed in supine and prone positions improves the confidence and accuracy of the reader for detection ofcolorectal abnormalities.
8-0334 11'50
Magnetic resonance colonography vs. virtual colonoscopy for the detection of colonic polyps
E. ~, G. Gualdi, E. Polettini, G. Pappalardo, F:M. Frattaroli; Rome/IT
Purpose: Prompted by the disadvantages of conventional colonoscopy (CC), we compared the diagnostic ability of MA Colonography (MAC) only, Virtual Colonoscopy (VC) only, and a combination of MAC and VC for
detecting polyps. Material and methods: Seventy consecutive patients referred for CC underwent preliminary MAC using a 3D TFFE sequence with spoiling gradients. For the VC reconstruction, the MAC data were
downloaded to a voxel workstation. The diagnostic ability of these techniques in detecting colonic polyps was determined, compared with that of CC, and related to the findings from histologic examination.
Results: No statistically significant differences in the detection of polyps were found between the three techniques, However, the combination of MAC and VC resulted in polyps detection rates that were greater than
those MAC orVC alone, In detecting polyps, the combination of MAC and VC achieved good diagnostic ability (53 true-positive; 2 false-negative; 14 true-negative, and 1 false-positive). This yielded high sensitivity (96
%) and specificity (93 %), a good positive predictive value (98 %) and a negative predictive value of 87.5 %,
Conclusion: The combination of MAC and VC provides the greatest rates of detection of polyps and VC improves the specificity helping to distinguish normal folds from fixed raised lesions that are suggestive of
polyps.
8-033610:40
Optimisation of treatment strategy using cooled-tip radiofrequency electrodes In ex-vlvo liver
A.R. Gillams, W.R. ~; LondonlGB Purpose: Rises in impedance, restrict energy deposition and efficacy of radiofrequency ablation. Different techniques have been tried to circumvent this. We performed multiple
treatments in ex-vivo pig liver to optimise treatment strategy.
Methods and materials: Treatments were performed with both single and triple cluster, cooled tip electrodes. We compared pulsing, incremental step down and cessation of treatment at the first impedance rise.
Incremental step down involves re-introduction of power following impedance changes but to progressively lower power levels. Initial power settings were 40, 50, 75, 100, 150 and 180 W. Treat- ment times varied from
55 -600 s.ln another experiment a radiofrequency splitter was employed to allow simultaneous activation of 4 single electrodes. Different electrode configurations and electrode distances were studied. The diameter of
induced necrosis was measured.
Results: The majority of induced necrosis occurs during peak power prior to impedance rise. Maximal necrosis was produced by maximum power >170 W, for < 600 s. Pulsing alter impedance changes produced only
a small increment in necrosis. Incremental step down was more beneficial. An alternative strategy of moving the electrode to a new position alter the first impedance rise will maxi mise necrosis, but may not be the
preferred technique. Using the Rf splitter, maximal necrosis was obtained with four electrodes spaced at 1 cm intervals in a square configuration.
Conclusion: The incremental step down technique maximised necrosis. and is preferable if electrode repositioning is undesirable. Cluster electrodes with 1 cm spacing are optimal but the practicalities of easy
deployment require smaller spacing.
10:30-12:00 Room H Interventional Radiology SS 60ga
Percutaneous tumor ablation
Chairpersons:
R.D. Garcia-Monaco (Buenos Aires/AR) K. Hiramatsu (TokyolJP)
8-033510:30
Should thermal ablation be offered to patients with colorectalliver metastases who have been down staged by chemotherapy? A.R. Gillams, W.R. ~; LondonlGB
Purpose: < 25 % of patients with colorectalliver tumors respond to chemotherapy but the response is temporary < 6 months. We studied outcome in chemotherapy responders who subsequently underwent thermal
ablation.
Materials and methods: Since 1995 we have performed thermal ablation in 101 patients of whom 31 had responded to chemotherapy by a reduction in the size and/or number of liver metastases on CT. 29/31 received
systemic and 2 intra- arterial chemotherapy. 30 received 5 FU, 25 with folinic acid and 5 with Irinotecan, Mitomycin or Oxaliplatin. The other patient received Tomudex, Irinotecan and Oxaliplatin sequentially. All
subsequently underwent thermal ablation to their re- sidualliver metastases. 9/31 patients had optimal disease ex1ent < 5, < 5 cm tu- rnors and no extra-hepatic disease. Patients were followed at regular intervals Until
death. Survival analysis was performed stratified for disease extent at the start of thermal ablation. Survival statistics were compared to the 70 other pa- tienls.
Results: Median survival from diagnosis of liver metastases was 44 months for Chemotherapy responders with optimal extent of disease (n = 9) and 32 months brlhose with more ex1ensive disease (n = 22). There was
no significant difference 11 Survival between chemotherapy responders and the remainder, allowing strati- ~tion for disease ex1ent. Median survival for the remainder was 49 months in the OPtimal disease group (n =
36) and 21 months for the others (n = 34).
Conclusion: Thermal ablation should be offered to patients who respond suffi- ciently well to chemotherapy to fulfill standard thermal ablation acceptance crite- 1Ia.
8-033710:50
Radiofrequency (RF) ablation of liver tumors with the Le Veen probe: Is roll off predictive of response?
P. ~, R. Cuomo, R. Piazza, F. Simeone, L. Grazioli, L. Matricardi; BresciallT
Purpose: The purpose of this study was to determine the relation of roll-off (the dramatic rise in impedance that occurs following the application of sufficient power for an appropriate period of time during RF ablation) to
local control of hepatic tumors.
Methods and materials: 20 patients (16 M, 4 F) with hepatic tumors (16 HCC and 4 metastases) were treated. Lesions ranged from 1.6- 7.5 cm in maximum diameter. The 15 gauge Le Veen needle electrode
(Radiotherapeutics, Mt View, Ca) was inserted percutaneously or during laparotomy with the use of sonographic guidance. Tumours larger than 3 cm were treated with overlapping burns. Patients were followed with
contrast-enhanced, triple-phase CT. Contrast enhancement within the tumour on arterial phase scanning was considered consistent with residual tumour.
Results: Roll-off was achieved in 12/20 lesions (60 %). No local failures occurred when roll-off was achieved. 418 lesions without roll-off were completely ablated. There were four residual tumors at treated sites. In all
four of these lesions none of the burns resulted in roll-off.
Conclusion: Local failure occurred in 50% of lesion without roll-off. Therefore the lack of roll-off during RF ablation does not necessarily represent a failure and does not reliably predict treatment outcome.
8-0338 11.00
Radiofrequency ablation of liver metastases: Ultrasound or CT guidance? D. pj!;!s.Yth, C. Achilles, W. Weiwad, J. Richter, S. Heywang -Kobrunner, R. Spielmann; Hal/e a. d. Saale/DE
Purpose: Radiofrequency ablation of liver neoplasms is usually performed by using US guidance. The purpose of this study was to prospectively evaluate the potential benefit of CT-guided treatment.
Patients and methods: 18 patients with metastatic tumours of the liver received a single treatment of both US- and CT-guided percutaneous radiofrequency ablation to 32 lesions (lesion size 1 -4.5 cm; median 2.5
cm). For follow-up purposes, contrast enhancement of liver metastases was measured with CT by digitally sub- tracting tumour data acquired during a non-enhanced phase from data acquired in
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10:30-12:00 Room I -~
Abdominal and Gastrointestinal SS 1001c
CT colonography Chairpersons:
C.I. Bartram (Ha"ow/GB) B. Marincek (ZOrichlCH)
B-058310.30
Unravelling the colon using multirow detecor-CT:Technique and first experiments with technical and cadaveric phantoms
E. SQrg.n1in', E. Balogh2, G. Werkgartner', E. Spuller', K. Palagy2, S. Loncaric3, M. Subasic3, R. Fotter'; 'GrazlA7; 2SzegedlHU, 3Zagreb/HA
Virtual colonoscopy represents a challenging imaging modality for colonic polyp detection. A software tool, which enables, similar to the pathologist's table, a virtual cut along the colons's axis, would allow to
inspectlhe oral and aboral side of folds simultaneously.
Purpose: To present a technique for unrevealing the colon as well as the appear- ance of colonic polyps on artificial and cadaveric phantoms on those views.
Material and methods: Two phantoms were created. Phantom A consisted of a plastic tube and polyps were simulated by knobs of plastilin. Phantom B was 50 cm long cadaveric colon, where 13 artificial polyps were
created. Alter scanning the following steps were necessary lor unrevealing: (1) segmentation of the inner surface, (2) extraction of the central axis using a skeletonisation algorithm, (3) computation of the cross
sectional cuts orthogonal to the central axis, (4) remapping of the cross sectional cuts into a new orthogonal 3D data volume, (5) shaded surface rendering of the remapped data. The whole inner surface of the
phantoms was displayed at one view, investigated for polyp occurrence and findings compared to real dissection of the phantom.
Results: Human interaction took less than 10 minutes for the segmentation step. Computation time was 2 hours. Simulated polyps appeared as bumps on phantom A and as bumps or as asymmetric broadening of
the colon folds on phantom B.
Conclusion: Simulated polyps on artificial and cadaveric phantoms could be demonstrated on virtual views alter unrevealing. Thus making these views a feasible display technique for virtual colonoscopy.
8-058410:40
Evaluation of patient acceptability for CT virtual colonoscopy after retrograde CQ2 Insufflation
M.G.J. ~, D. Vanbeckevoort, D. Bielen, A. Gevers, Po Rutgeerts, G. Marchal; LeuvenlBE
Purpose: To evaluate patient acceptability for virtual colonoscopy (VC) using CO2 in comparison with sedated colonoscopy (SC).
Methods and materials: 52 patients referred for SC underwent a virtual VC prior lo the SC. All patients received a routine bowel preparation. Retrograde insuffla- lion of CO2 was performed to a degree the patient could
tolerate. Buscopan was injected intravenously prior to the VC. Patient acceptability for the bowel prepara- lion, VC en CC was assessed using a 10 point scale (0... highly acceptable, 10... not acceptable). Patient
tolerance at different times (0 minutes, 10 minutes, 20 minutes) after CO2 insufflation was also investigated with the same type of Scale. Patients were also asked which procedure (VC, SC) they preferred if re- peating
would be necessary.
Results: Patients found VC (median score 10 vs 0: 2.4) more acceptable then SC (median score 10 vs 0: 3.4) and bowel preparation (median score 10 vs 0: 4.1) was clearly the most uncomfortable procedure though
not unbearable. VC was the less pleasant directly after the CO2 insufflation though the embarrassment decreased exponential over the first 20 minutes. 73 % of the patients preferred VC when they were asked which
procedure they would choose in the future.
Conclusions: VC is likely more acceptable then SC when retrograde CO2 insufflation is used.
8-058510:50
Fecal tagging in virtual CT colonoscopy
E. t!.ejn, P. Rogalla, F. Vogel, 8.8. Hamm; Berlin/DE
Purpose: To evaluate the diagnostic gain of fecal tagging for detection of colonic polyps.
Materials and methods: 132 patients (semi-screening population) underwfjnt a virtual CT colonoscopy after standard bowel preparation using phosphosoda. 12 - 16 h before the CT examination, the patients were given
30 mi of iodined oral contrast material, and again 1 -2 hours before scanning. Images were obtained in supine position only with 3 mm slice thickness. 5 mm/s table feed, and 2 mm reconstruction interval, and colonic
distension with CO2-gas rectally. Resulting virtual endoscopic fiy-throughs were calculated: first with single thresholding (re- maining fluid levels were seen as such, method 1 ), second, with dual thresholding (for air
and contrast medium, method 2). The number of polyps detected were compared between both groups. If polyps or other intraluminal findings were seen, patients underwent subsequent coionoscopy.
Results: A total of 17 polyps (sizes: 5-13 mm) and 2 cancers (stage T2NO and T3N1) were detected in 13 patients. all were confirmed on subsequent flexible colonoscopy. A total of 2 polyps were missed (4 and 5 mm)
on both methods. 1 polyp was submerged under a contrast fluid level thus not seen with method 1. but seen with method 2. Fecal residue was selectively contrasted and thus did not carry the risk of being
misinterpreted as vital tissue.
Conclusion: Fecal tagging with iodinated oral contrast medium is feasible and effective. However. in combination with optimal patient preparation, the additional diagnostic gain may be little.
8-058611'00
Optimization of multislice spiral computed tomography colonography: Study on a colonic phantom model
A. !.a.ghi, C. Catalano, R. lannaccone,V. Panebianco, I. Baeli, F. lafrate, R. Passariello; Rome/IT
Purpose: To optimize scanning parameters for CT colonography using a multislice spiral CT scanner in a study on a colonic phantom model.
Materials and methods: A home-made colonic phantom, represented bya plastic tube containing 27 simulated lesions (12 polyps, 9 depressed lesions, and 6 flat lesions) was scanned in transverse, oblique (45°), and
coronal planes in a water- filled plastic box. Four scanning protocols were tested using different collimation, slice width, and reconstruction index values. Each protocol was tested three times using different rotation
feed values. Milli-Ampere/s values were set to 80. Images were interactively reviewed on a dedicated workstation using a software with volume-rendering capabilities (Vitrea 2.0, Vital Images, USA).
Results: Image quality was optimal for any protocol when evaluating axial 2D images. Three-dimensional endoluminal images were optimal for protocol nr 1, good for protocol nr 2, fair for protocol nr 3, and poor for
protocol nr 4. Evaluation based on simultaneous assessment of 2D and 3D images demonstrated an average sensitivity for protocols nr 1, 2, 3 and 4 of respectively 100 %, 98 %, 94 %, and 85 %. The evaluation of
three different rotation feed values tested for each of the lour protocols did not show statistically significant differences in terms of sensitivity. In the assessment of 3D images, average sensitivity was 92 % for protocol
nr 1, 85% for protocol nr 2, 77% for protocol nr 3 and 58% for protocol nr 4.
Conclusions: The introduction of multislice technology in CT colonography pr o- vides improved spatial resolution and better image definition.
8-058711:10
Multislice spiral CT colonography: Initial clinical study with a high- resolution protocol
A. J.ag!Ji, G. Gatalano, V. Panebianco, I. Baeli, J. Garbone, R. lannaccone, R. Passariello; Rome/IT
Purpose: To evaluate the sensitivity detection rate of GT colonography for colorectal
disorders using a multislice spiral GT scanner. Materials and methods: Thir1y-five patients (20 males; 15 females) with clinical indication for conventional colonoscopy or after unsuccessful performance of conventional colonoscopy were selected. Spiral GT (Somatom Plus 4, Siemens, G) examination was performed after standard oral colonoscopy preparation and colonic distension with room air. Images were obtained
using 1 mm collimation, 1 mm reconstruction index, 8 mm/s rotation feed, and mAs 80. Supine and prone acquisitions were obtained in all patients. Images were interactively reviewed on a dedicated workstation
using a software with volume-rendering capabilities (Vitrea 2.0, Vital Images, USA).
Results: Images of the distended colon were judged as optimal in all the cases, although artifacts were evident in 2D images due to low mAs value. Dose exposure never exceeded 9.12 mGy for each scan. All
colorectal cancers were identified. Sensitivity for detecting polyps was 89 %, with 100 % for lesions larger than 10mm.
Scientific Sessions
Conclusions: The introduction of multislice technology in CT colonography has improved image quality and simultaneously reduced dose exposure. Larger clinical studies are necessary to assess its improvements
in terms of diagnostic accuracy.
8-058811:20
Virtual colonoscopy: A painful procedure D.A. Nicholson, R. Mehan, H. Burnett; SalfordlGB Purpose: Virtual colonoscopy (VC) is a new CT based method of large bowel visualisation. For VC to become established as
a diagnostic test for colorectal polyp/cancer detection it must be well tolerated and accepted by patients.
Methods: Patients undergoing evaluation of colonic symptoms underwent VC prior to fibreoptic colonoscopy (FC). All patients had standard colonic cleansing/preparation. To perform VC a rectal tube is inserted
followed by air insufflation after intravenous Buscopan in order to minimise colonic spasm. A spiral CT of the abdomen and pelvis is then performed. The whole examination generally takes less than 15 minutes. FC
was performed using standard intravenous sedatives and muscle relaxants. Before and after both tests patients completed a questionnaire concerning their symptoms of discomfort/pain, abdominal bloating, anxietY
and overall preference of techniques. The patients were asked to score each variable on a 100 point scale.
Results: To date 76 patients have been evaluated. Regarding symptoms of discomfort and pain; 35 % of patients experienced no difference with either technique. 48 % found FC more comfortable than VC with only
17 % tolerating VC better than FC. Regarding patient preference scores 21 % patients had no preference, only 21 % preferred FC whereas 54% would prefer a VC in the future. These preliminary results from
thisstudy has shown that patients experience more dis- comforVpain with VC compared to FC. However patients prefer VC when asked to choose between these two techniques of colonic imaging. Full results from this
on-going trial will be presented.
8-058911:25
Spiral CT colonography in postoperatory surveillance after colorectal- cancer: A preliminar study
A. bggill, C. Catalano, I. Baeli, J. Carbone, R. lannaccone,V. Panebianco, R. Passariello; RomellT
Purpose: To assess the role of spiral CT colonography in the postoperatory follow-up of patients with colorectal cancer.
Materials and methods: 15 patients, 7 women and 8 men, aged between 49 and 76 years, one with total colectomy and 14 with emicolectomy were selected. Multislice spiral CT (Somatom Plus 4 Volume Zoom,
Siemens, G) examination of the abdomen and pelvis after regular colonoscopy bowel preparation and colonic distension with air was performed. Patients were scanned in supine and prone position with the following
parameters: 1 mm collimation, 1 mm reconstruction index. 8 mm/s rotation feed, and mAs 80. Supine scans were acquired after administration of iodine contrast medium for liver evaluation. Images were elaborated
and examined on a dedicated workstation. Correlation with conventional colonoscopy was obtained in all patients.
Results: Thirteen patients presented with negative findings at both spiral CT colonography and conventional colonoscopy.ln one case a recurrence at the level of the anastomosis was observed. In one patient 8 mm
polyp in the descending colon was detected and removed at conventional colonoscopy. In three cases liver metastases were detected.
Conclusion: In patients who have undergone surgical removal of a colorectal cancer, virtual CT colonoscopy could be an effective method of surveillance alternative to conventional colonoscopy. The use of contrast
medium injection can be useful in order to evaluate liver metastases which are the main cause of death in patients with surgically treated colorectal cancer.
B-0590 11:35
Virtual colonoscopy as a screening post-operative method: Work-in- progress
P. Leonardou,V. Maniatis, S. Kavadias, N. Tsavaris, A. Papadopoulos, K. Stringaris, G. Zois, G. Zois; AthenslGR
Purpose: To evaluate virtual colonoscopy (VG) as a screening method in patients who have been operated for colon cancer.
Materials and methods: VG has been performed in 18 patients during post-operative screening. Six of them had permanent colostomy, 3 had underwent right hemicolectomy, 4low-anterior colon resection and 5
sigmoidectomy. They were 7 women and 11 men (29-84 years old). 17118 patients were examined during regular follow-up while in one case there was a strong suspic!o-~!el~se. All
these patients could not have a complete follow-up study by other methods because of post-operative adhesions/permanent colostomy or patient's refusal to have a conventional colonoscopy. CT protocol consisted
of: slice thickness: 5 mm, table feed: 10 mm/s, reconstruction index: 5 mm, in both supine and prone position after distending the colon with air. VC images were created in an Easy Vision (Philips) workstation.
Results: Relapse was confirmed with VC in the suspicious case. In the rest of Our cases no findings of relapsing were depicted and that came to agreement with the clinical/laboratory evaluation and the course of the
disease.
Conclusion: VC is a well-tolerated imaging method for the evaluation of the colon. The absence of false negative results in our study leads to the conclusion that VC can be a reliable diagnostic tool for screening
patients who have underwent an operation for colon cancer.
8-059111:40
CT colonography in Crohn's disease
Z. Thrjg.r), T. ZBgoni, Z. Eles, E.K. Mak6; Budapest/HU
Purpose: To evaluate CT colonography in patients with colonic Crohn's disease. Material and methods: Five patients with known (4) or suspected (1) Crohn's disease of the colon underwent fiberoptic colonoscopy and
CT colonography in the same day or in a weeks period. The images were evaluated with zoomed axial slice movie technique and in some region intra. and extraluminal surface shaded and volume rendered images
were generated on a separate workstation. The re. sults were compared to those of colonoscopy.
Results: The final diagnosis was Crohn's disease in four patients and Colitis ulcerosa in one. Total examination was possible by colonoscopy in two cases, with CT colonography in all the five cases. The wall of those
segments severely affected by the disease were depicted by the axial CT scans to be thickened. The thick walled, segments with narrow lumen seen on CT colonography corresponded to the regions where
colonoscopy was failed to pass. Air filled sinus tracts, thicken. ing of the wall of the terminal ileum, loss of haustration pseudopolyps and deep ulcers were seen in CT colonography. Three dimensional endoluminal
views dem. onstrated pseudopolyps similar to endoscopic images None of the colonoscopically reported shallow ulcerations or aphtoid ulcerations or granular mucosal surface were observed on two. or threedimensional CT colonographic images.
Conclusion: CT colonography by depicting colonic wall thickening seems to be a useful tool in the diagnosis of Crohn's colitis, which could be a single examination depicting the intraluminal, and transmural extent of
the disease.
B-0592 11 ;50
Virtual colonography. Space resolution Vs. radiation dose in search for polyps: An experimental study
P. ~, M. Zavoral, J. Lacman, P. Kubikova, M. Vasicek, M. Heissler; PraguelCZ
Purpose: The aim of this study was to experimentally evaluate the space resolu. tion of CT virtual colonography (CTC) using different scan parameters and calcu. late the accordant skin dose.
Material and methods: Ten artificial polyps of a diameter from 2 to 7 mm have been investigated by CTC using Somatom Plus 4. Power with single slice Ultra Fast Ceramic detectors and workstation VIRTUOSO.
Constant parameters of the protocol were: 120 kV; 50 mA; kernel 4.5 and 2 mm increment of reconstruction. Variable parameters were: slice 5 mm, pitch from 1 to 1.5; slice 3 mm, pitch from 1 to 2.33; slice 2 mm, pitch
from 1.5 to 2.5. The space resolution has been assessed and skin dose has been calculated.
Results: The increase of the slice thickness results in the increase of mAs. The decrease of the slice thickness improves the shape of polyp's surface. The in. crease of pitch reduces the radiation dose. The average
skin dose of CTC was 7.2 mSv, the range of the observed values based on different parameters of both the slice and the pitch was from 94.9to 157.08 percent.
Conclusion: Our CTC protocol made by 5 mm slice, pitch 1.4 is associated with very low radiation dose. The decrease of slice thickness improves the space reso. lution. The increase of pitch allows further reduction of
skin dose. The practical benefits of this experiment will have to be proved by clinical trial.
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Scientific Sessions
8-059311:55
The accuracy of computed tomographic colography (CTC) in polyp and cancer detection
D.A. Nicholson', R. Mehan'. H. Burnett', C. Summerton'; 'SalfordlGB, 2Manchester/GB
Purpose: CTC is a new technique allowing minimally invasive imaging of the co- Ion. We are conducting a clinical trial which has been funded by the North West R&D NHS scheme to determine the accuracy of CTC
compared to fibreoptic colonoscopy (FC) in detecting colonic polyps and cancer
Methods: To date, 96 patients of 200 have been recruited. Patients undergo CTC on the same day as FC. Standard bowel cleansing is given to patients. CTC is performed in both supine and prone positions using a
single breath hold, spiral CT following intravenous Buscopan and air Insufflation. The findings of CTC are being correlated with the findings of FC in each patient.
Results: To date 76 patients have been analysed, A total of 37 polyps in 28 patients were detected by FC (28 of these polyps were < 1 cm in diameter). CTC detected all polyps greater than 1 cm but only 15 of the 28
polyps < 1 cm in diameter. In addition 4 false positives on CT were identified. 4 cancers seen at FC wer~ all detected by CTC. Additionally CTC det~ct~d a further canc~r in the right side of the colon not reached at
FC and a renal cell carcinoma in another patient. FC was completed to the ceacum in only 65 patients (84 %) whereas CTC was completed in all.
Discussion: Initial results show that CTC is a sensitive method of detecting colonic cancer and polyps > 1 cm in size. This abstract will present the up to date figures of this on-going trial.
Pediatric
ss 1012
Genitourinary and central nervous system
Chairpersons:
G. Enriquez (BarcelonalES) R. Fotter (GrazlAT)
B-0594 10:30
MR-urography in neonates and infants with dilated upper urinary tract: Preliminaryexperience
M. Riccabona, J. Simmbrunner, E. Ring, R. EQt!.e.r; GrazlAT
Purpose: To evaluate the feasibility and diagnostic potential of dynamic MR-urography (MRU) in neonates and infants with sonographically detected dilatation of the upper urinary tract.
Patients and methods: 20 infants (age: 5 days -18 months, mean: 1.5 months, male:female = 16:4) underwent MRU after oral sedation using T2 and contrast enhanced dynamic T1 weighted sequences. The results
were compared to the findings of ultrasound (US, 20), intravenous urography (IVU, 12) and/or scintigra- phy (16) based on the criteria suggestive of obstructive uropathy.
Results: Oral sedation was sufficient to perform MRU with diagnostic image qual - ity in 19 patients. Diagnosis of the 40 kidneys included: normal system (7), duplex
system (6), vesicoureteral reflux (8), megaureter (7), uretero-pelvic junction obstruction of various degrees (15), and dysplastic/cystic kidney (4), with complex pathologyin 7 kidneys. MRU demonstrated anatomy
better than by IVU, particu- larly concerning the parenchyma, the ureter, and pelvic dilatation -on T2 weighted sequences in 3 patients with non- or poorly functioning systems. MRU was superior to ultrasound in
showing ureteral pathology. Tiny cysts in dysplastic kidneys were better shown by US. Gadolinium enhanced dynamic MRU allowed assessment of obstruction applying IVU criteria with equal quality. The results
matched IVU results and/or scintigraphic findings.
Conclusion: MRU can be performed in infants and neonates with sufficient image quality using oral sedation. MRU properly depicts anatomy and allows assessment of urinary tract obstruction better than US and NU.
It additionally provides functional information and therefore has the potential to replace IVU.
B-059510:40
Gadolinium enhancedT1-weighted vs. T2-weighted MR urography in children with abnormalities of the upper urinary tract
G. ~, C.C.A. Nolte-Ernsting, D. Rohrmann, C. Stollbrink, P. Haage, J. Tacke, R. W. Gunther; AachenlDE
Purpose: To evaluate gadolinium enhanced T1-weighted MR urography (GMRU)
versus T2-weighted MR urography in children with upper urinary tract abnormalities.
Methods and materials: 65 children, aged 3 weeks to 15 years, with upper urinary tract disorders underwent MR urography in a 1.5 T scanner. After an i. v. injection of low dose furosemide (0.05 mg/kg/bw), GMRU
was performed with respiratory-gated, coronal 3D-gradient-echo sequences, using maximum-intensity pro- jections for postprocessing. Respiratory-triggered Half-Fourier RARE images (HASTE) were obtained for T2weighted MR-urography. MR-urography findings were compared to the final consensus diagnosis.
Results: MR urography was successfully performed in all cases, with only 3 of 65 children needing sedation. Gd-enhanced MR urography revealed a superior diagnostic accuracy compared to T2-weighted MR
urography in non-dilated collecting systems (horseshoe kidneys, ectopic kidneys, duplex systems, single ectopic ure- ters, ureteroceles). GMRU and T2-weighted MAU were equivalent in the assessment of an
obstructed but normal functioning urinary tract (UPJ-obstructions, megaureters). Non-functioning dilated collecting systems and multicystic dysplastic kidneys were best visualized by T2-weighted MA urography.
Conclusion: Aespiratory-gated T1-weighted MAU allows accurate and sufficient evaluation of urinary tract abnormalities. T2-weighted MRU complements GMRU in the evaluation of non-functioning renal units and
cystic diseases of the kidney.
B-0596 10:50
Radiological monitoring of tumor response to medical treatment in children with Wilm's tumor
A. AQlgmy.y!S, V. Zhelow, Z. Stadnyk; Lviv/UA
Purpose: It is well known, assessment of treatment efficacy is of great importance to patient management. The aim of our study was to analyse dynamics of US, CT findings in children with Wilm's tumor during
preoperative chemotherapy (PCT).
Methods and materials: 21 children with Wilm's tumor in late stages of disease (9 boys and 12 girls) were examined by ultrasonography and computed tomography with bolus contrast-enhancement (CE) (Ultravist, 2
mVkg) before and 24- 48 hours after course of PCT. All children were considered good respondents to treatment, confirmed by the pathologic examination. The evaluation of tumor volume. tumor composition,
vascularity and contrast-enhancement was made.
Results: 17 patients (81 %) showed gradual decrease of tumor volume, increase of heterogeneity with some growth of Resistive index (RI) in 2 of them and reduced CE in 6 of them. In the 3 patients (14 %) tumor
volume remained unchanged, but there was some increase internal heterogeneity in all of them, growth of Resis- tive index and reduction of CE in 1 of them. 1 patient (4 %) demonstrated slight enlargement of tumor
volume with marked cystic degeneration without measur- able change of RI, patchy CE.
Conclusion: Although volume is most significant indicator of tumor response, other criteria such as tumor composition and vasculariiy also can be used in as- sessing tumor sensitivity to medical treatment.
8-059710:55
Echo-enhanced color Doppler sonography of vesico-ureteral reflux in children
M. Riccabona, E. Ring, F. Lindbichler; GrazlAT
Purpose: To evaluate the potential of echo-enhanced color Doppler sonography ( ee-CDS) in the diagnosis of vesicoureteral reflux (VUR) in children in a prospective study.
Patients and method: 30 children (0 -10 years) with suspicion of or known VUR were submitted for echo-enhanced ultrasound (ee.US), ee-CDS and conventional voiding cystourethrography (VCU). Ee-CDS was
performed alter instillation of Leveovist into the catheterized urinary bladder that had been filled with saline solution. Therealter VCU was performed in the same session. The results of ee. US and ee.CDS were
compared to VCU findings.
Results: Levovist was safe and easy to administer. Sonography detected VUR into 2 renal units (grade II and 111) not seen by VCU, but missed VUR grade I in all 3 cases. Demonstration ofVUR grade II and III was
better by ee-CDSthan ee-US. Conclusion: Levovist is a safe sonographic contrast material for use in the pedi. atric bladder. It enables relaible visualization of VUR into the renal collecting sys-
tgm I"g.rn~ onh~n~o~ ~~n+.n~+ .~.,. .~ ---+,-. .,--,. .,- ---~"-."- -, .
Page 1 of 1
Douglas Boyd
From: Juergen Scheidler [scheidler@ikra.med.uni- Sent: Wednesday, February 07, 2001 8:23 AM To: doug@imatron.com Subject: Mr. Deike
Dear Dr. Boyd:
Mr. Oeike called me today regarding virtual endoscopy with EBT and he gave me your email address. We have published our results in the
journal "Radiologe" in German with an English abstract. Please find attached the article as .pdf file.
As you know the EBT unfortunately is non existing anymore in our hospital. You were so kind to borrow me a PC to do the reconstructions. The
demo licence of Acculmage is long expired (I think after publishing the paper in 1998) and the PC is still sitting around (P200 pro, 256MB EOO
RAM, one HO crashed, the other one has tons of bad sectors (both are Quantum 6 GB 5.25 harddisks, seemed to be not the most durable).
Anyway, what should I do with the PC? Shipping to the US may not be worthwhile. However, there is still a Windows NT server (!) included,
which may be useful for you and your company. \NI1ere do you want me to send the software?
Thank you very much for providing me with the Acculmage soft- and hardware to perform the study. The bottomline is that EBT colonoscopy is
working very well and with the new version of accuimage the rendering results will be great. The major problem here in Germany is that the
patients are seen at first by gastroenterologists and they don't want to give up colonoscopy
Sincerely yours,
Juergen Scheidler
Juergen Scheidler, MD Assistant Professor
Section Chief, Magnetic Resonance Imaging Dept. of Diagnostic Radiology University of Munich D-81366 Munich Germany
Ph.: +49-89-7095-3250 Fax: +49-89-7095-8822
e-mail: scheidler@ikra:med.uni-muenchen.de
3/8/01
Radiologe
1998 .38:824-831 @Springer -Verlag 1998
Zusammenfassung
Ziel: Ais virtuelle Koloskopie bezeichnet man eine neue Methode, die aus Bilddaten der ra- diologischen Schnittblldverfahren, CT, Elek- tronenstrahl-a (EBT) und MRT mittels com- puterunterst(jtzter
Bildnachverarbeitung si- mulierte dreidimensionale (3D-),endosko- pieahnliche Bilder des Kolons erzeugt. Ziel unserer Untersuchung war die Bestimmung der Wertigkeit der virtuellen EBT Koloskopie zum Nachweis von kolorektalen Polypen und Tumoren in vitro am Tumormodell und in Pa- tientenstudien.Anhand publizierter Studien der virtuellen Koloskopie mit Spiral-CT und MRT
sollen die verschiedenen Untersu- chungstechniken dargestellt und verglichen werden.
Material und Methode: 6 Polypen mit einem Durchmesservon 3-12 mm wurden nac h Abheben und Umstechen der Mukosa in Schweinekolon gebildet. Nach Distension mit Raumluft wurde dieses
Tumormodell mit EBT im"continuous volume scanning (CVS)- Mode" mit 3-mm-Kollimation und 3 verschiedenen Pitchverh~ltnissen (0,4; 0,8; 1,5) gescannt; 20 Patienten mit positivem Hamocculttest wurden nach rektaler CO2-lnsuf- flation und i. v.-Gabe von 1 mg Glucagon in Atemanhaltetechnik mit einem den ganzen Kolonrahmen abdeckenden CVS-Scan
(13 s Untersuchungsdauer) untersucht.En- doskopische 3D-Durchflugsrekonstruktionen wurden von 2 unabhangigen Radiologen hinsichtlich des Vorliegens von Polypen oder Tumoren beurteilt. Die
zu erwartende effektive Dosis f(jr die EBT -Koloskopie wurde (jber Messungen mit einem Alderson-Phantom, welches mit Thermolumines zenzdosimetern best(jckt war, berechnet.
824 I DerRadiologe 10.98
J.Scheidlerl .(.Frankl .(.Becker1. H.Feist2 .G.Michalski2 .M.Schatzr .A.Baumr A.F.Heuck1. M.F.Reiser1
llnstitut fur Radiologische Diagnostik (Direktor: Prof. Dr. M. F. Reiser), Klinikum GroBhadern, Ludwig-Maximilians -Universitat M(jnchen
2 Abteilung Medizinische Physik, Klinikum GroBhadern, Ludwig-Maximilians -Universitat M(jnchen 3 Bundesamt fOr Strahlenschutz, Neuherberg bei M(jnchen
Ergebnisse: schon bei einem Pitch von 1,5 wurden alle Polypen im Tumormodell erkannt. Die Reduzierung des Pitch auf 0,8 oder 0,4 verbesserte nicht die Erkennbarkeit der
Polypen auf den endoskopischen 3D-Re- konstruktionen.AlleTumoren (n = 4) und Polypen (n = 3) der Patientenuntersuchun- gen wurden korrekt identifjziert.2 falsch-positive
Befunde wurden erhoben. Die effektive Dosis pro Scan errechnete sich zu maximal 3,2 msv.
SchluBfolgerungen: Unsere vorlaufjgen Er- gebnisse deuten darauf hin, daR die virtuelle EBT -Koloskopie eine vielversprechende Me- thode zum Nachweis von kolorektalen
Tu- moren ist. Der stellenwert der verschiedenen Techniken der virtuellen Koloskopie (spiral- a,EBT,MRT) muR erst noch bestimmtwer- den.
Schliisselworter
Koloskopie .Spiral -CT . Elektronenstrahltomographie .MRT . virtuelle Realitat
"Virtuelle Endoskopie" bezeichnet eine neue Methode, die aus Bilddaten radiologischer Schnittbildverfahren simulier- te 3D-endoskopieiihnliche Bilder rnittels
computerunterstfitzter Bildnachverar- beitung erzeugt. Grundvoraussetzung sind Bilddaten aus Volumenakquisitio- nen, die mit Spiral-CT, Elektronenstrahl- CT (EBT) oder MRT
gewonnen werden konnen.
Die Nichtinvasivitat der Methode macht die Anwendung dieser Technik zur Erkennung von Kolontumoren und Kolonpolypen besonders interessant. Im folgenden sollen die
verschiedenen Untersuchungstechniken der virtuellen Koloskopie auf Basis der Schnittbild- verfahren CT und MRT dargestellt werden. Anhand unserer eigenen Erfah- rungen
und publizierter Studien sollen die Perspektiven und Limitationen der Methode kritisch beleuchtet weden.
Methoden
Patientenvorbereitung
Die virtuelle Koloskopie mit CT oder MRT erforde rt die vollst~ndige Reini- gung des Kolons von Stuhlresten. Prinzi- piell kann dies durch abftihrende MaB- nahmen wie zur
Vorbereitung fiir einen Kolonkontrasteinlauf geschehen. Eine zus~tzliche orale Darmsp1ilung wie zur Koloskopievorbereitung ist nach unse- ren Erfahrungen nicht erforderlich
und ftihrt h~ufig zu ausgedehnten Flftssig- keitsresten im Darm,die fiir 3D-Rekon- struktionen aus CT -Datensiitzen von Nachteil sind. Die Applikation von Bus- copan (20 mg i.
v.) oder Glucagon (1 mg langsam i. v.) unmittelbar vor Untersu- chungsbeginn ist zur Vermeidung von Spasmen und zur optimalen KolondiDr.J.Scheidler
Institut fur Radiologische Diagnostik, Klinikum GroBhadern,LMU Munchen, MarchioninistraBe 1 S, (}-81377 Munchen
Radiologe
1998.38:824-831 e Springer-Verlag 1998
J. Scheidler .C. Frank. C. Becker .H. Feist G. Michalski .M. Schatzl. A. Bauml A. F. Heuck .M. F. Reiser
Virtual colonoscopy using a and MR imaging
Summary
Purpose: To evaluate experimentally and in patients the sensitivity and effective dose of virtual electron-beam tomography (EBT) colonoscopy for detecting small colon tumors
and to compare the methods and results with virtual colonoscopy using spiral a and MR imaging in a review of the literature. Materials and methods: Six polyps with di- ameters
between 3 and 12 mm were created and randomly placed in resected pig colon. After distension with air, the pig colon was scanned with continous volume scanning (CVS,3
mm collimation) and a pitch of 0.4, 0.8 and 1.5. Twenty patients positive for the fecal blood test were examined after rectal CO2 insufflation and i.v.administration of
1 mg glucagon. A 13 s CVS scan was used to cover the entire colon within one breath- hold. 3D volume-rendered fly-throughs were evaluated by two independent radiologists.
Effective dose equivalent was estimated using an Alderson phantom equipped with thermoluminescence dosimeters.
Results: In the tumor model, all polyps were detectable at a pitch of 1.5.A further reduction of the pitch ratio did not improve the conspicuity of the polyps. In patient studies, all
tumors (n = 4) and polyps (n = 3) were correctly identified on 3D fly-throughs. Two false positive results were obtained. Effective dose equivalent was calculated at 3.2 mSv per
scan.
Conclusions: Our preliminary results indica- te that virtual EBT colonoscopy holds promi- se for fast screening for colon polyps. The best technique for virtual colonoscopy (Spiral a, EBT, MRI) has not yet been determined and the future role of virtual colonoscopy must still be defined.
Key words
Spiral computed tomography. Electron beam tomography -EBT .
Magnetic resonance imaging -MRI. Colonoscopy .Virtual reality
stension obligat. Buscopan wie Glu- cagon haben bei i. v.-Injektion einen ra- schen Wirkungseintritt (unter 1 min) und eine kurze Wirkungsdauer (ca. 15 min).
Wahrend Glucagon eine starkere relaxierende Wirkung auf die glatte Muskulatur hat, ist Buscopan deutlich kosteng1instiger und wird daher bevor- zugt
eingesetzt. Anticholinerge Neben- wirkungen von Buscopan und daraus resultierende Kontraindikationen zur Anwendung bei Patienten mit Glau- kom,
Prostatahypertrophie und kardio- vaskularen Erkrankungen miissen aber beachtet werden. In diesen Fanen kann auf Glucagon ausgewichen werden, welches
nur bei Phaochromozytomen und Insulinomen kontraindiziert ist.
CT-Untersuchungstechnik
Hochwertige intraluminale 3D-Rekon- struktionen gelingen nur bei guter Di- stension des Kolons und hohem Kon- trast zwischen Lumen und Darmwand. In aIlen bisher
publizierten Studien wurde Raumluft oder CO2 als Kontrast- und Distensionsmedium verwendet. Nach dem Nachlassen der Buscopan- Wirkung kann die Luftfiillung des Darms
Spasmen verursachen. Mit CO2 traten diese Beschwerden in unserem PatientenkolIektiv nicht auf. Die rasche Resorption von CO2 ist ft1r diesen posi- tiven Effekt verantwortlich,
ft1hrt aber auch zu einer suboptimalen Distension, wenn die Untersuchung nicht unmittelbar nach der Insufflation durchgef6hrt wird.
Die rektale Insufflation von Luft oder CO2 erfolgt bei uns direkt auf dem CT - Tisch. Wahrend der Insufflation wird der Patient umgelagert, urn eine gleichmaBige Gasverteilung
zu gewahr- leisten. Die Distension wird anhand des Topogramms kontrolIiert, So daB vor dem eigentlichen Scan ggf. noch etwas Luft nachgegeben werden kann. Die
Untersuchung wird zunachst in Riickenlage durchgeft1hrt. SoIIten die axialen Schichten eine unvolIst andige Distension oder Stuhl- und Fliissig- keitsreste zeigen, schlieBen wir
einen 2. Scan in Bauchlage an.
Idealerweise solIte der gesamte Ko- 10nrahmen in einer Atemanhaltephase erfaBt werden, damit m6glichst geringe Atem- und Peristaltikartefakte auftre- ten.Bei einer
kraniokaudalen Ausdeh- nung des Kolonrahmens zwischen 30
und 40 cm und maxima125 s Atemstill- stand laBt sich dies auch mit modern- steD SubsekundeD-Spira1-CT -GerateD Dur danD erreicheD, wenn eiDe groBe Schichtdicke (z. B. 8
mm bei eiDem Pitch VOD 1,5) gewahlt wird. Die Auf1()- sung iD LoDgitudinalrichtung liegt dann aber uber dem anzustrebeDdeD Wert VOD unter 10 mm. UDterschiedli- che
AtemlageD st()reD die DatenfusioD und ft1hreD zur RekoDstruktioD VOD "PseudopolypeD" und"Wchern" iD der Darmwand. Dennoch ist es vorteilhaft, deD gesamteD
KoloDrahmeD mit Dur ei- Der Spira1e abzudeckeD. Dabei wird der PatieDt Dach eiDer initia1eD Atemanha1- tephase wahreDd des Scans zu laDgsa- meD AusatmeD und
tlachem Weiterat - meD angeha1teD. Die Atemartefakte werdeD dadurch reduziert und SiDd eher vertretbar a1s die obeD geDannteD RekoDstrukti oDsfehler.
Die UDtersuchung so1lte mit einer Ko1limatioD VOD 5 mm und eiD Pitch VOD Dicht weseDtlich uber 1,5 erfolgeD. ID vitro StudieD zeigeD eiDe gute Er- keDDbarkeit VOD
PolypeD bei dieser KollimatioD und einem Pitch zwischeD 1 und 1,6 [2, 6]. Die Vergr()BeruDg des Pitch auf deD Faktor 2 oder das Kolli- matioD auf 7 mm verschlechterte die
ErkeDDbarkeit VOD PolypeD unter 8 mm Durchmesser [2]. Durch die Reduzie- ruDg des R()hreDstroms VOD 280 auf 70 mA kommt es zu eiDer deutlicheD Do- siseinsparung,
wahreDd eiD hoher KoD- trast zwischeD dem LumeD und Darm- wand erha1ten bleibt [5]. Bei 5 mm Kol- limatioD, 1,0 Pitch und 70 mAs betragt die effektive
Gesamtk()rperdosis zwi- scheD 4,23 und 5,82 mSv [ 6].
Aufgrund der obeD geDannten Li- mitatioDeD der Spiral-CT fiihreD wir die virtue1le Koloskopie am EBT durch. Mit der EBT k6nneD bis zu 140 SchichteD bei
koDtiDuierlichem Tischvorschub iD- Derha1b VOD 13 s akquiriert werdeD. Da- durch kann der gaDze KoloDrahmen iD eiDer Atemanha1tephase gescanDt werden. Dariiber
hinaus kanD die Kollimati - OD bei der EBT kleiDer a1s bei der Spi- ra1-CT gewahlt werdeD, was die Bild- qua1itat giinstig beeintluBt. Bewahrt hat sich bei uns die
UDtersuchung im CVS- Mode mit 3 mm KollimatioD, 3 mm Tischvorschub, 100 ms ExpositioDSzeit und uberlappeDdem RekoDstruktioDs- modus (Pitch 1,5). Daraus resultiert
eine effektive Schichtdicke von 6 mm bei einem RekoDstruktioDsiDtervall VOD
DerRadiologelO.98 I 825
3 mm. Ein k1eineres Pitchverhiiltnis Von 0,4 oder 0,8 fiihrte im 1\1mormodell in vitro nicht zu einer verbesserten Er- kennbarkeit von Polypen mit einem Durchmesser von 3-12
mm [19]. Die effektive DoSis dieses Protoko11s un ter Einschlu6 des Topogramms betrug ma- xima1 3,2 mSv (eigene, noch nicht pu- blizierte Messungen).
MRT -Untersuchungstechnik
Die einzige bisher erprobte Technik der virtuellen MRT -Koloskopie beruht auf dem Prinzip der schnellen kontrastver- starkten 3D-MR-Angiographie in Atemanhaltetechnik.
Ahnlich wie beim arteriellen GefiiBsystem wird der Ko- lonrahmen mit Kontrastmittel gefiillt, das gleichzeitig als Distensionsmedium dient. Dazu werden 1,5-21 Wasser, versetzt mit 1% einer 0,5 mol/L Gadolini- uml()sung rektal instilliert [9] .Der Pati- ent wird dazu in Bauchlage auf dem MRT - Untersuchungstisch positioniert und in
Untersuchungsposition gefah- ren. Die Filllung wird mit einer nicht schichtselektiven 2D-Gradientenecho- sequenz kontrolliert. Sobald die ver- dilnnte Gadoliniuml()sung das
Z()kum erreicht hat, erfolgt die Datenakquisiti- on in Atemanhaltetechnik. Wir verwen- den auf einem 1,5T MRT -Geriit (Magne- tom VISION, Siemens) eine FISP -3D
Angiographiesequenz mit ultrakurzen Echo- und Repetitionszeiten und fre- quenzselektiver Fettunterdrilckung [TR = 4,5 ms, TE = 1,5 ms, Flipwinkel 25°,162 x 512 Matrix, 500
mm 518 Recht- eck, Field-of-View (FoV), 80 Schichten mit 2 mm Schichtdicke, Akquisitions- zeit 26 s].
Um ein ausreichend hohes Signal- Rausch-Verhiiltnis zu erzielen, ist bei diesem Protokoll eine Phased-array- Spule erforderlich. Bei Verwendung der K()rperspule muB die
Matrix auf 256 Frequenzkodierschritte reduziert und die Schichtdicke erh()ht werden [10]. Der Schichtstapel wird auf der Lokali- sationssequenz schriig koronar und parallel zum
Verlauf des Kolonrahmens eingeneigt. Um T2-gewichtete Bilder zu erzeugen, erfolgt anschlieBend eine HASTE (half foUrier single Shot turbo- SE)-Sequenz (TR = 4A ms, eff.
TE = 64 ms, 192 x 256 Matrix, 400 mm 718 Rechteck-FoV, 17 Schichten, 8 mm Schichtdicke, 20 s Akquisitionszeit). Der Patient wird danach in Riickenlage
826 I Der Radiologe 10.98
Abb.l .2D -MPR eines EBT -Datensatzes nach rektaler Insufflation von C~. Kein Nachweis von Poly - pen oder Tumoren. Aufgrund von Kontraindikationen gegen Buscopan und Glucagon
konnte bei diesem Patienten keine Peristaltikhemmung erfolgen. Segmentale Kontraktion im Colon transversum
(...) ohne Anhalt fiir stenosierende Raumforderung (( = Zokum, s = Sigma, r = rektum)
gebracht und die Angiographiesequenz nach i. v.-Gabe von 0,1 mmol Gd- DTPA/kg KG wiederholt.
Bildrekonstruktion
Die CT -Bildrekonstruktion sollte in m()glichst engen Abstanden (z. B. 1 mm) erf01gen, um optimale 3D-Rekon- struktionen ohne st()rende Treppenar- tefakte zu erhalten. Die
resultierende Menge Von 350-400 Bildern ist selbst von leistungsf!ihigen Computern nur schwer zu handhaben. McFarland et al. konnten jedoch zeigen, daB sich die Qualitat von
Rekonstruktionen mit 50-60% Oberlappung nicht von der mit 90% Oberlappung unterscheidet [12]. Dies bestatigte sich bei eigenen Versu- chen mit EBT -Datensitzen [19], So
daB von uns standardmiiBig fiir die CT -Ko- 10Skopie ein Rekonstruktionsintervall von 50% der Schichtdicke gewahlt wird.
Die 3D-MRT -Sequenz erlaubt die Rekonstruktion weiterer Schichtebe- nen aus dem Datensatz. Zur Befunder- stellung werden von uns grundsatzlich aus dem parakoronaren
Schichtstapel der 3D-Angiographiesequenz axiale Schichten mit einer Schichtdicke von 5 mm rekonstruiert.
Bildnachverarbeitung
Prinzipiell kOnnen aus den Datensatzen 2.D- und 3D-Projektionen erzeugt werden. Mit gekriimmten multiplanaren Rekonstruktionen (curved MPR) entlang der Mittellinie des
Kolons kann der Kolonrahmen zu einer iibersichtli- chen tubuliren Struktur gestreckt werden (Abb. 1). Wie fiir die Erzeugung von 3D-endoskopischen Durchf1(igen erfordert
diese Technik eine Pfaddefmition entlang der Mittellinie des Kolons. die je nach verwendeter Software zeitaufwendig manuell oder ha1bautomatisch [13 ] erfolgt. Die Arbeitsgruppe der Mayo- Klinik hat eine eigene Software ent- wickelt,die semiautomatisiert die Strek- kung des
Kolonrahmens mit 2D- und 3D-Bilderzeugung bewerkstelligt [8].
Zur endoskopischen 3D-Rekon- struktion werden von den CT/MR-Ge- rateherstellern (Navigator von GE; Prominence und Virtuoso von Siemens; VoxelQ von Picker; EasyVision
von Phi- lips) und unabhangigen Softwareent- wicklern (Voxe1View und Vitrea von Vi- ta1 Images, Fairfield, IA, USA; Maxi- mum Impact von Silicon Graphics, Mo- untain
View, CA, USA; AIDP und AccuView von Acculmage, South San Francisco, CA, USA) eine Vielzahl von Hard- und Softwarepaketen angeboten. Diese Liste erhebt keinen
Anspruch auf Vollstandigkeit ( eine ausfiihrliche Liste von 3D-Softwarepaketen kann im Inter- net unter http://biocomp.arc.nasa.gov/ 3dreconstruction/software/ eingesehen
werden). Teilweise stellen Arbeitsgrup- pen auch selbstentwickelte Software kostenfrei zur Verfugung (z. B. Free- Flight, Bowman Gray School of Medici- ne,
http://indigo2.rad.bgsm.edu).
Allen Softwarepaketen gemeinsam ist die perspektivische Bilddarstellung, die erst den endoskopischen Tiefenein - druck ermoglicht, d. h. nahe Objekte werden groBer dargestellt
a1s weiter entfernte Strukturen. Zur Bilderzeu- gung werden entweder Obert1achen- (surface shaded display-SSD) oder Vo- lumenrekonstruktionstechniken (volume rendering)
angewandt. Obert1l- chenrekonstruktionsa1gorithmen stellen geringere AnsprUche an die Hard- ware und sind schneller a1s "volume rendering", da nur ungefahr 10% der
Datenmenge, namlich die der obert1a- chenbildenden Voxel zur Rechenarbeit eingesetzt werden muB. Die Entwick-
Abb.2a-e ...Kolonpolyp. Die 2D-MPR des EBT -Datensatzes zeigt den Polypen Im Colon slgmoideum (a,s,hwQrzer Pfei/). Zusatzlich scheint ein weiterer, kleinerer Polyp vorzullegen (a, wei8er Pfei/).ln
der 3D endoskopischen Rekonstruktion (retrograde Flugrichtung) vor (b) und in der xhicht des Polypens (() erkennt man das AusmaB der Lumenelnengung durch den groBen Polypen und in elnerwelteren
Projektion (d) dessen Beziehung zu den Haustrierungen. Der Weiterflug laBt 2 cm proximal des Poly- pens eine relatlv kraftlge Haustrierung erkennen (e,Pfeilspitze),dle In der 2D MPR einen welteren
Polypen vorgetluscht hat
lung leistungsfahiger Computersyste- me fiihrt zunehmend zum Einsatz von "volume rendering", das Bildinformati- on aus a1len Voxeln zur Rekonstruktion nutzt. Dabei werden
nicht feste Schwell- werte vorgegeben, sondern es wird anhand eines Histogramms der Houns- field- oder Signa1werte die Transparenz bzw. Dichte der interessierenden Strukturen fiir die Rekonstruktion festgelegt, d. h. die Dichte- oder Signalintensitits- information bleibt zumindest teilweise erhalten.
Wichtig ist die Wahl geeigneter Pa- rameter fiir die 3D.Rekonstruktion, da diese maBgeblich die Realitatsnahe der Rekonstruktionen beeinfluBen. Je nach Software kann f{1r
SSD-Rekonstruktio- nen ein (unterer) Schwellwert oder bes- ser 2 (unterer und oberer) Schwellwerte vorgegeben werden. Bewahrt hat sich bei dem von uns verwendeten Programm (AccuView von Acculmage) ein unterer Schwellenwert von -700 HU und ein oberer Schwellenwert von -300 HU. Beim Volume-rendering- Verfahren wird empfohlen,
unter -700 HU 100% Transparenz zu wiih1en und zu hoheren HU-Werten hin dann die Transparenz mit einer sigmoidalen Anstiegsfunkti- on zu vermindern [12].
Die 3D-Rekonstruktion erfolgt je nach Programm entweder direkt interaktiv in Echtzeit oder es werden, nach- dem ein Flugpfad festgelegt wurde, zeit- verzogert serielle
endoskopische 3D- Rekonstruktionen erzeugt und zu einem Video zusammengefiigt. Mit der Echtzeitmethode kann an jedem Stop- punkt interaktiv der Betrachtungswin- kel und
Ausschnitt festgelegt werden. Je nach Rechenleistung der verfiigbaren Computerplattform kann dies aber sehr zeitaufwendig sein. Die Erzeugung
eines zeitverz6gerten Videodurchflugs hat den Nachteil, daB man nicht direkt eingreifen kann. Andererseits erfolgt dieser Vorgang automatisiert und erfordert keinen zusatzlichen Zeitauf- wand des Untersuchers. Meist wird eine retrograde Flugrichtung vom Anus zum ZOkum gewahlt. Einige Program- me
unterstiitzen auch einen automati- schen antegraden "Riickflug".
Bildauswertung
und Befundinterpretation
Da die Erfahrungen mit der virtuellen Koloskopie bisher noch begrenzt sind, haben sich noch keine allgemein akzep- tierten Kriterien fiir die Bildinterpreta- tion etablieren
kOnnen. Fiir die virtuelle CT -Koloskopie hat es sich bewahrt, grundsatzlich 2D-gekr{immte multipla- nare Rekonstruktionen ( curved MPR) und 3D- Videos zu erzeugen (Abb. 2,
3) und diese kombiniert mit den axialen Ausgangsschichten in die Befundung einzubeziehen. Zun~chst werden die "curved MPRu und das 3D-Video darauf analysiert, ob ein
polyposer Tumor oder eine Stenose vorliegt und das be - troffene Darmsegment wird notiert.
DerRadiologe 10.98 I 827
Abb.3a-c ..Kolonkarzinom. Untersuchung mittel5 EBT. 3D.endo5kopiscbe Rekonstruktionen Yor (a) und in der xhicht des Tumors (b) mit korrespondierendem endo5kopiS(hen Bild (c). Retrograde Flugrlchtung mit Lagede5Tumors im Colon tran5Yersum (7) in der Nahe derlinken Kolonflexur.Dadurch An5chnitt und Rlickblick in da5 Colon de5cenden5 (D) auf den endo5kopiscben Rekonstruktionen
Die Position eines auffalligen Befunds wird als Distanz ab ano gemessen (curved MPR) bzw. sie wird auf dem 3D- Vi- deo direkt als zuriickgelegte Flug- strecke in Zentimetern
angegeben. Die "curved MPR" und die endoskopischen 3D-Darstellungen erleichtern die Be- fundung erheblich, da bei Betrachtung der axialen Einzelschichten angeschnit- tene
Haustrierungen leicht fiir Polypen gehalten und Polypen als DarnUalten fehlgedeutet werden konnen [6]. Unse- re eigenen Erfahrungen bestatigen die SchluBfolgerungen von
Hara et al., die ebenfa11s 2D- wie auch 3D-Rekonstruk - tionen ftir erforderlich halten [8].
Endoskopische 3D-Rekonstruktio- nen a11ein sind andererseits keinesfalls ausreichend. Stuhl- und Fliissigkeitsre- ste konnen Polypen und Raumforde - rungen und eine
ungeniigende Disten- sion kann Pseudostenosen vortau- schen. Dies kann vermieden werden, wenn die axialen Ausgangsbilder und die 2D-MPR beriicksichtigt werden. Stuhlreste
kOnnen anhand kleiner Luft - einschliisse sowie durch die Lageiinde- rung zwischen der Untersuchung in Bauch- und Riickenlage von Polypen und Tumoren unterschieden werden
[3]. Pseudostenosen sind von tumorbe- dingten Stenosen durch das Fehlen einer Raumforderung auf den axialen Schichten zu unterscheiden. Die Mitbe- wegung des Kolons bei
Atemexkursio - nen fiihrt zu erheblichen Unschirfen und Verwacklungsartefakten, die die 3D-Beurtei1ung des betroffenen Darm- segments unmOglich machen k(Snnen.
Falsch-positive Befunde auf den 3D-endoskopischen Rekonstruktionen entstehen, wenn die Untersuchung mit Spiral-CT in mehreren Atemanhalte- phasen durchgefiihrt wird.
Durch un- terschiedliche Atemlage kommt es zu u>chern oder Pseudopolypen beim An- schnitt von Haustrierungen [7]. Diese Feh1befunde lassen sich meist durch Vergleiche mit
der 2D-MPR vermeiden.
Die Beurtei1ung der MRT -Kolonun- tersuchung erfolgt zunachst anhand der parakoronaren Einzelschichten. Zur besseren (lbersicht werden die axialen Rekonstruktionen
herangezogen. Sehr hiflreich ist auch die interaktiv gesteuer- te simu1tane Darstellung a11er 3 Ebenen (,,3D-Cursor") am Scanner oder an einer Workstation. Maximumintensity- Projektionen (MIP) werden von uns rekonstruiert, um den Darmverlauf iihn- 1ich wie im Kolonkontrastein1auf in Mo- nokontrasttechnik darzustenen und
Stenosierungen zu erkennen. K1einere, nicht stenosierende Lasionen sind auf dem MIP -Bi1dern nicht immer erkennbar. Polypose Lasionen konnen von dem Kontrastmittel
iiberlagert werden, wenn die Polypen nicht randstlindig loka1isiert sind. 3D-endoskopische Rekonstruktio - nen aus MRT -Daten haben im Verg1eich zur CT eine geringere
Aufll>sung, ein sch1echteres Schichtprofi1 und infolge der feh1enden iiberlappenden Schich- tung eine deut1ich sch1echtere Qua1itat. Wir ftihren daher keine routinemaBigen
Durcht1ugsrekonstruktionen durch und beschriinken uns auf die gezielte endo - skopische Darstenung pathologischer Befunde in der MRT (Abb. 4).
Da immer Luftiiberschichtungenn iiber der Kontrastmittelsiule vorliegen. konnen in der MRT leicht polypose Schleimhautlisionen iibersehen werden. Es muB daher unbedingt
eine sorgfaltige Durchsicht beider Untersu- chungen -in Bauch- und Riickenlage - erfolgen. Polypen und Thmoren konnen von Stuhlresten anhand des Aspekts. der i. v.Kontrastmittelaufnah- me und der fehlenden Lageinderung bei der Untersuchung in Bauch- und Riickenlage unterschieden werden.
Ergebnisse
Die zukUnftige Bedeutung der virtuellen CT - und MR-Koloskopie kann anhand der bisher publizierten Daten nicht ausreichend abgeschatzt werden. Die grOBte Studie zur
virtuellen Kolos- kopie unter Einsatz der Spiral-CT an 70 Patienten ergab eine Sensitivitat der Methode Von 75% und ein e Spezifitat von 90% im Nachweis von Polypen und
Thmoren ?; 10 mm [7]. Die Sensitivitat fiel aber bei Lasionen unter 5 mm GroBe signifikant ab (45%). Die Sensitivitat (58%) und Spezifitat (74%) der Metho- de war bei der
alleinigen Beurteilung der axialen Ausgangsbilder geringer als wenn zusatzlich 2D- und 3D-Rekon- struktionen herangewgen wurden.
In einer weiteren Studie zur virtuellen Koloskopie mit Spiral-CT wurden iihnliche Ergebnisse an einem allerdings deutlich kleinerem Patientenk01. lektiv erhoben [17]. Bei 20
Patienten wurden alle Thmoren und 14 der 15 P01y- pen (GroBe unter 2 cm) auf 2D-Rekon- struktionen erkannt. Auf den endoskopischen 3D-Bildern lieBen sich 19/20
Thmoren und 13h5 P01ypen diagnosti- zieren. In 17/20 Patienten konnte eine virtuelle 2D- und 3D-Endoskopie des
828 I Der Radioloae 10.98
Abb.4a-d A KolonpolyplmZ6kum.MRT.Untersuchung nad \Elnlaufvon 1,5 lelner1%Gd.DTPA Losung. Koronare Einzelschicht {a), axiale Rekonstruktion (b), MIP-Rekonstruktion (c) und 3D endoskopische
Rekonstruktion (d). Die koronaren (a) und axialen (b) Schichten zeigen klar den gestielten Polypen {-+). Die MIP-Rekonstruktlon (c) eignet sich gut zur Darstellung des Darmverlaufes, Polypen sind aber
h~ufig darauf nlcht erkennbar. Gute r~umllche Darstellung des Polypens {-+) Im 3D endo. skopischen Biid in Oberflachenrekonstruktionst8(hnik (d)
gesamten K010nrahmens erf01gen, wahrend der K010nrahmen in der konventionellen Koloskopie nur bei 12/20 Patienten v011stmdig einsehbar war. Die Autoren betonen
ebenfalls die Notwendigkeit der kombinierten Be- fundung von 2D- und 3D-Rekonstruk - tionen.
Die vorlaufigen Ergebnisse unserer eigenen prospektiven Studie mit der virtuellen EBT -K010Skopie an bisher 20 Patienten ergaben keine falsch- negativen Resultate [19]. Im
Vergleich zum G01dstandard K010Skopie wurden
alle Tumoren (n ; 4) und Polypen (n ; 3) erkannt. Es wurden allerdings 2 falsch-positive Befunde erhoben. Bei einem Patienten wurde eine Pseudoste- nose als reeller Befund
gewertet. Bei einem weiteren Patienten wurde ein of- fensichtlicher Polyp in der virtuellen EBT -Koloskopie gesehen. Beide Befun- de waren endoskopisch nicht verifi- zierbar; 2
Patienten konnten wegen schlechter Vorbereitung nicht beurteilt werden. Die Endoskopie konnte aus diesem Grunde aber ebenfalls nicht durchgeftihrt werden.
Zur virtuelleD K010Skopie mit MRT existiert erst eiDe prospektive Studie, in der 23 PatieDteD vor K010skopie untersucht wurdeD [11]. Alle ThmoreD und P01ypeD ~ 10 mm
wurdeD erkanDt (n = 9); 8 VOD 10 P01ypeD mit eiDer Gr(}Be VOD 5-10 mm wurdeD ebenfalls diagDO- stiziert. AllerdiDgs wurdeD alle Lasio- DeD bis 5 mm Gr(}Be
iiberseheD uDd 3 falsch-positive Befunde erhobeD.
Perspektiven
Das K010nkarzinom ist der zweithau- figste Tumor in Europa und entsteht in mehr als 90% der Fane aus adenomattl- sen Polypen [15]. Der Zeitraum bis zur karzinomattlsen
Transformation be - tragt ungefahr 5 Jahre [21]. Polypen un - ter 6 mm GrO6e sind lediglich in 0,1% maligne [22], wahrend Adenome iiber
Der Radiologe 10-98 I 829
10 mm GroBe in 10% ein invasives Kar- zinom beherbergen [14]. Die derzeit 1iblichen Fr1iherkennungsprogramme sind nicht geeignet, um diese Polypen zu erfassen. Der
Nachweis von okkul- tem Blut im Stuhl (Hamocculttest) ist unspezifisch und die Sensitivitat dieses Tests ist ebenfalls gering. Polypen 1iber 1 cm GroBe konnen nur mit einer
Sensi- tivitit von 13% erkannt werden und nur '13 der Karzinome werden durch den Hamocculttest erfaBt [1]. Da jahrliche Koloskopien sehr aufwendig und bela- stend sind und
1iberdies hohe Kosten verursachen, k6nnte die virtuelle Ko- loskopie in Zukunft eine sinnvolle Al- ternative zur Fr1iherkennung des Ko- lonkarzinoms sein.
Die Untersuchungsmodalitaten und Zeitintervalle zukiinftiger Screening- programme sind derzeit Gegenstand heftiger Kontroversen. Sigmoidoskopien oder Koloskopien in
zeitlichen Abstan- den von 1,3,5 oder 10 Jahren, teilskombi- niert mit dem Hamocculttest werden diskutiert. Kiirzlich wurde alternativ zur Sigmoido- und Koloskopie der Kolonkontrasteinlauf (Kolon-KE) von einer Expertengruppe im Auftrag der "US Agency for Health Care Policy" in die Empfeh1ungen zum Screening aufge - nommen [24].
Wie eine soeben erschienene Ko- steneffektivititsstudie zeigen konnte, ist der Kolon-KE trotz dessen geringe- rer Sensitivitat f1ir Polypen der Kolos- kopie als
Screeningsverfahren mit 6,02 gegen1iber 5,93 gewonnenen Lebensjah- ren pro 100000 untersuchten Personen ebenb1irtig [4].
F1ir den Kolon-KE in Doppelkon- trasttechnik wurde in mehreren prospektiven Studien eine Sensitivitat von mindestens 81% und eine Spezifitat von 96% bei Polypen von 1iber
1 cm GroBe ermittelt [18,20, 23], wahrend die Sensi- tivitat der Koloskopie bei dieser Poly - pengroBe 94% betrigt [16]. Diese sch1echtere Performance wird durch deutlich
niedrigere Kosten ($131 vs. $284) mehr als kompensiert, so daB das Screening mit dem Kolon-KE im 5-Jah- res-Intervall statt wie bei der Kolosko- pie in 10-jahrigen Intervallen
durchgefiihrt werden kann. Wenn sich die bis- herigen Ergebnisse der virtuellen CT - und MR-Koloskopie an groBeren Pati- entenkollektive bestatigen,ist zu erwar- ten, daB
Karzinome und Polypen 1iber 1 cm GroBe mit einer dem Kolon-KE ver-
830 I DerRadiologel0.98
gleichbaren oder besseren Treffsicher- heit erkannt werden.
Dem Einsatz der virtuellen Kolosko- pie in Screeningprogrammen stehen aber bisher die fehlende Validisierung sowie die hohe Kosten der Methode ent- gegen. Mit Hilfe des
"Nationallnstitutes of Health" (NIH) ist in den USA eine prospektive Multicenterstudie zur Ober- prUfung der Wertigkeit der virtuellen CT -Koloskopie im Vergleich zur Koloskopie in Planung. Die hohen Kosten der Methode sind in erster linie durch die lange Gesamtuntersuchungszeit bedingt. Ff1r die eigentliche Untersuchung ("in room-time")
werden nur ca. 20 min (EBT oder Spiral-CT) bzw. ca. 40-45 min (MRT) benotigt. Problematisch sind die langen Nachverarbeitungszeiten von bis zu 2 h pro Patient, die einer
weiten Ver- breitung der Methode entgegenstehen. Durch die standig steigende Rechenlei- stung der Computer und die Entwick- lung von automatisierten Rekonstruk- tions- und
Dokumentationsprogram- men sind hier bald Fortschritte zu er- warten.
AIs Hauptlimitation der Methode im Vergleich zur Koloskopie muB die fehlende Moglichkeit angesehen werden, entdeckte Lasionen in gleicher Sit - zung zu entfernen und
Biopsien zur weiteren Abklarung zu entnehmen. Auch ist die raumliche Auflosung und der Kontrast von CT und MRT zu ge - ring, um z. B. entziindliche Veranderun- gen der
Mukosa auf endoskopischen Rekonstruktionen zu erkennen. Es wire jedoch falsch, sich nur auf das virtuell endoskopische Bild zur Diagnostik zu beschranken und den
wesentlichen Vorteil der Schnittbildverfahren gegen- iiber der Endoskopie, der Blick iiber die Mukosa hinaus, nicht zu nutzen. Die Einbeziehung der Ausgangsbilder in die
Diagnostik erlaubt auf einfache Weise den Blick ~inter die Kulissen" und damit auch die Diagnostik von Pathologi- en auBerhalb des Darms. Die Niedrig- dosistechnik der CTKoloskopie und der Verzicht auf i. v.-Kontrastmittel re- duzieren zwar das Signal-Rausch-Ver- haltnis und den Bildkontrast auf den axialen CT -Schichten. Eine orientieren- de
Diagnostik von Lymphknoten oder Metastasen ist abe r dennoch moglich. Dagegen sind die MRT -Ausgangsbilder durch den hohen Weichteilkontrast der Methode diagnostisch gut
verwertbar und erganzende T2-gewichtete Schich-
ten und kontrastverstarkte Studie kOn- nen ohne Strah1enbelastung durchgefiihrt werden.
Zukiinftig werden mit Volumenre- konstruktionsverfahren (volume rendering) extraluminale Strukturen dreidimensional dargestellt werden, so daB im
Vergleich zur konventionellen Ko- loskopie ganz neue Bildeindri1cke ver- mittelt werden konnen. Da beim volume rendering die Bilddaten nicht auf die
wandbildenden Strukturen reduziert, sondern in ihrer Gesamtheit zur dreidimensional-Rekonstruktion ge- nutzt werden, kann die Transparenz der Darmwand
so gewahlt werden, daB extraluminale Strukturen und Patholo- gien dreidimensional durch die Darm- wand hindurch wahrgenommen werden konnen.
Die virtuellen endoskopischen Tech- niken befinden sich derzeit noch im Anfangsstadium der Entwicklung. Die Weiterentwicklung und Standardisie- rung von
Hard- und Software werden schnelle, automatisierte Rekonstruktio- nen ermoglichen. Wenn es dadurch ge- 1ingt, virtuelle Koloskopien zu Preisen anzubieten,
die deutlich unter denen der Koloskopie liegen, werden sich virtuelle koloskopische Verfahren in der medizinischen Versorgung etablieren konnen.
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C.-RAdler
Knochenkrankheiten
Diagnostik makroskopischer, histoiogischer und radiologischer Strukturveranderungen des Skeletts
2. Auf1.; Berlin, Heidelberg, New York: Springer, 1998.591 S., 980Abb.,6 Tab., (ISBN 3-540-62836-3), geb., DM 248,In der nunmehr
2.Auf1age des erst- mals 1983 mit
groBem Erfolg auf- gelegten Buches werden auch die neueren Untersu- chungstechniken des Knochens wie Magnetresonanz- tomographie und Computertomo- graphie erlautert.
Auch diese Auf1age besticht durch viele Abbildungen von makroskopischen und mikro- skopischen Knochenschnitten zurVeranschauli- chung der jeweiligen pathologischen Veranderun- gen.
Dariiber hinaus werden in anschaulichen Schemata die zum Teil komplexen Knochenstoff- wechselvorgange erklart.
Nach einer kurzen Einleitung iiber physiolo- gische Anatomie und Histologie des Knochens werden die zum Teil sehr seltenen Entwicklungs- sttirungen des skeletts, aber auch stoffwechselsttirungen und Entziindungen des Knochens um- fangreich beschrieben. Den grtiBten Raum neh- men naturgemaB die gutartigen und btisartigen Knochentumoren ein. Hier iiberzeugt vor allem die
klare Gliederung entsprechend dem jeweiligen Herkunftsgewebe. Leider fjnden sich lediglich im AbschluBkapitel iiber Untersuchungstechni- ken auch farbige Abbildungen der histologischen
schnitte. Bei Durchsicht der umfangreichen Lite- raturquellen wiirde man sich in manchen Ab- schnitten auch aktuelle Zitate wiinschen.
Gesamthaft hat auch die 2. Auf1age des Bu- ches gute Aussichten,sich als Nachschlagewerk fiir an Knochenerkrankungen interessierte Arzte (vor allem Chirurgen, Orthopaden, Radiologen) zu
etablieren.
c. Flamme (Hannover)
DerRadiologel0.98 I 831

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