Gammex RMI CT Phantom, 438

Transcription

Gammex RMI CT Phantom, 438
Gammex RMI CT Phantom, 438
(ACR CT Accreditation phantom, 464)
S. Edyvean, Jim Weston
Imaging Performance Assessment of CT Scanners
St. Georges Hospital, London
www.impactscan.org
Some images courtesy of Cynthia McCullough
Mayo Clinic, Rochester, USA
CT Users Oct 2007
ImPACT
Gammex RMI CT Phantom, 438
• David Aikman
– Gammex RMI Ltd.,Nottingham
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CT Users Oct 2007
Gammex RMI CT Phantom
Head
20 cm
4
High
contrast
resolution
Foot
3
Uniformity
& noise
Distance
accuracy
2
Low
contrast
resolution
1
Alignment
CT #
Image
width
SSP
4 cm
CT Users Oct 2007
3
Gammex RMI CT Phantom
4
CT Users Oct 2007
Documentation
Manual, also ACR (American
College of Radiology) website
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https://www.gammex.com
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ACR CT Accreditation Program
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ACR documentation
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Setting up
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Module 1: alignment, image thickness, CT number
Polyethylene
≈ -97 HU
“Bone” ≈
+910 HU
Water ≈
0 HU
Acrylic ≈
+120 HU
Air ≈
-1000 HU
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CT Users Oct 2007
Module 1: alignment, image thickness, CT number
High-resolution
chest technique
Must see all four BBs
(in Modules 1 & 4)
Longer wire must
have same number of
lines above and
below (±1)
Wires are 0.5 mm
apart in z-direction
WW = 1000
WL = 011
CT Users Oct 2007
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CT Users Oct 2007
Module 1: alignment, image thickness, CT number
Adult
abdomen
technique
Wires are 0.5
mm width
apart in zScan
direction
measured
at several
scan
widths
11 / 2 = 5.5 mm
10 / 2 = 5 mm
WW = 400
WL = 0
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CT Users Oct 2007
Module 1: alignment, image thickness, CT number
Adult
abdomen
technique
Polyethylene
-97 HU
CT≈number
measured in
5 materials
Water ≈
0 HU of
CT number
water
measured at
Acrylic
≈
several
scan
+120
widths
andHU
kVps
“Bone” ≈
+910 HU
Air ≈
-1000 HU
WW = 400
WL = 0
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CT Users Oct 2007
ACR documentation: module 1
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CT Users Oct 2007
Module 2: Low contrast detectability
• Low contrast = 6 HU ± 0.5 HU
– (cf Catphan 10, 5, 3 HU single object of each size)
25 mm
2 mm
6
mm
3 mm
5 mm
4 mm
CT Users Oct 2007
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Phantoms for low contrast detectability (LCD)
• Catphan 500
2-15 mm diameter
10 HU contrast
5 HU
contrast
3 HU
contrast
• Catphan is closest to a ‘standard’ phantom
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CT Users Oct 2007
Module 2: Low contrast detectability
• Low contrast = 6 HU ± 0.5 HU
– (cf Catphan 10, 5, 3 HU single object of each size)
25 mm
2 mm
6
mm
3 mm
5 mm
4 mm
CT Users Oct 2007
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CT Users Oct 2007
Module 3: uniformity, noise, distance, mtf & ssp
Adult abdomen
and head
techniques
0.3 mm
Measure
tungsten
uniformity
and
carbide beads
noise
Assess for
artifacts
Measure
distance
accuracy
(optional)
CT Users Oct 2007
100
mm
WW = 100
WL = 0
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Module 4: high contrast spatial resolution
Adult abdomen,
Barhead
patterns:
adult
and
lp/cm
high-resolution
chest techniques
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10
4
Aluminium in
Record the first
solid water
highest
frequency bar
pattern for which
the bars and
spaces merge
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5
6
8
7
WW = 100
WL ≅ 1100
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CT Users Oct 2007
Gammex RMI CT Phantom
•
•
•
•
•
•
Nicely designed phantom
Excellent phantom stand
Good additional documentation from ACR
Slightly limited for axial MSCT? (40 mm modules)
Bar pattern doesn’t go to maximum resolution
LCD of 6HU different from manufacturers spec. (use 3HU
from Catphan)
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CT Users Oct 2007
https://www.gammex.com
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CT Users Oct 2007
Gammex RMI CT Phantom
• David Aikman
– Gammex RMI Ltd.,Nottingham
– 01159850808, daa@gammex.com
• Cost
– List price £5589 (not including stand),
– Discount for early sales ~10%
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CT Users Oct 2007
Incidental Findings
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Incidental Findings
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CT Users Oct 2007
Incidental Findings
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CT Users Oct 2007
Gammex RMI CT Phantom, 438
(ACR CT Accreditation phantom, 464)
S. Edyvean, Jim Weston
Imaging Performance Assessment of CT Scanners
St. Georges Hospital, London
www.impactscan.org
Some images courtesy of Cynthia McCullough
Mayo Clinic, Rochester, USA
CT Users Oct 2007
ImPACT

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