Visualization of central nerve tracts using a non-EPI, non

Visualization of central nerve tracts using a non-EPI, nonDWI method
Poster No.:
C-0108
Congress:
ECR 2013
Type:
Scientific Exhibit
Authors:
M. Yamazaki, S. Naganawa, K. Bokura, H. Kawai; Nagoya/JP
Keywords:
Tissue characterisation, Technical aspects, Comparative studies,
Neural networks, MR, Neuroradiology brain, CNS, Anatomy
DOI:
10.1594/ecr2013/C-0108
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Purpose
Heavily T2-weighted three-dimensional fluid-attenuated inversion recovery (hT2w-3DFLAIR) imaging of the inner ear 4 h after intravenous gadolinium injection has been
reported to separately visualize perilymph and endolymph fluid and to identify the
presence of endolymphatic hydrops in patients with Ménière's disease (Fig. 1) [1, 2].
Fig. 1: Axial heavily T2-weighted imaging (a: the vestibular level, b: the cochlear level)
for anatomical reference and hT2w-3D-FLAIR (c: the vestibular level, d: the cochlear
level) of a single patient with suspected Ménière's disease are presented. All images
were obtained 4 h after single-dose intravenous gadolinium injection. On hT2w-3DFLAIR, the perilymph of the cochlea shows high intensity. The endolymphatic hydrops
in the vestibules (arrows on c) and the cochleae (arrows on d) can be recognized as
areas of low signal intensity.
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
The central nervous system, including the brain stem, is also included in these images,
and some central nerve tracts are visualized as high-intensity regions with strong
contrast between the surrounding brain parenchyma. Therefore, hT2w-3D-FLAIR has
the potential to become a novel non-echo-planner imaging (EPI), non-diffusion-weighted
imaging (DWI) neurographic modality if particular central nerve tracts can be clearly
visualized.
Page 2 of 21
Consequently, the purpose of the present study was to elucidate the central nerve tracts
clearly visualized on hT2w-3D-FLAIR and to confirm that those central nerve tracts
correspond to those visualized on diffusion tensor imaging (DTI) for affirmation of the
validity of the novel imaging technique.
Images for this section:
Fig. 1: Axial heavily T2-weighted imaging (a: the vestibular level, b: the cochlear level) for
anatomical reference and hT2w-3D-FLAIR (c: the vestibular level, d: the cochlear level)
of a single patient with suspected Ménière's disease are presented. All images were
obtained 4 h after single-dose intravenous gadolinium injection. On hT2w-3D-FLAIR,
the perilymph of the cochlea shows high intensity. The endolymphatic hydrops in the
vestibules (arrows on c) and the cochleae (arrows on d) can be recognized as areas of
low signal intensity.
Page 3 of 21
Methods and Materials
Study population:
The records of seven consecutive adult patients (1 male, 6 female; aged 22-69 years;
mean age, 48.1 years) who underwent hT2w-3D-FLAIR and DTI of the head at our
hospital on January 2012 were analyzed retrospectively. All patients were clinically
suspected of having Ménière's disease, and they underwent magnetic resonance
imaging (MRI) for detailed examination in order to determine whether endolymphatic
hydrops was present.
All patients underwent intravenous administration of a single-dose (0.2 mL (0.1 mmol)/kg)
body weight) of gadolinium-diethylenetriamine pentaacetic acid-bis (methylamide) (GdDTPA-BMA) (Omniscan, Daiichi Sankyo Co., Ltd., Tokyo, Japan) and underwent MRI 4
h after intravenous gadolinium injection. This delay was chosen because a delay of 4 h
between intravenous gadolinium injection and MRI has been reported to be optimal to
allow wide distribution of gadolinium in the lymphatic space of the labyrinth in healthy
subjects [3].
Written informed consent was obtained from all patients, and the study was approved by
the Ethics Review Committee of our institution.
MRI protocol:
All scans were performed at 3 Tesla MRI (Magnetom Verio; Siemens AG, Erlangen,
Germany) using a receive-only, 32-channel, phased-array coil. The hT2w-3D-FLAIR and
DTI for anatomical reference were obtained at the same visit.
hT2w-3D-FLAIR images were obtained using sampling perfection with applicationoptimized contrast using different flip angle evolution (SPACE)-based sequences with
frequency-selective fat-suppression pre-pulse. The parameters for hT2w-3D-FLAIR are
shown in Table 1.
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Page 5 of 21
Table 1: The parameters for hT2w-3D-FLAIR
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
DTI images were obtained using less distortion readout-segmented multi-shot EPI
(RESOLVE)-based sequence [4]. The parameters for DTI are shown in Table 2. The
trace images, apparent-diffusion-coefficient (ADC) map, fractional-anisotropy (FA) map,
and color map were automatically produced on the scanner console. In the present color
assignment, green represents anterior-posterior, red represents lateral-lateral, and blue
represents superior-inferior orientations.
Page 6 of 21
Table 2: The parameters for DTI
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
Page 7 of 21
Imaging evaluation:
The coronal and sagittal hT2w-3D-FLAIR (7-mm slice thickness, 1-mm slice gap) images
were reconstructed from axial images.
Two neuroradiologists observed the hT2w-3D-FLAIR in three directions and determined
that the central nerve tracts were visualized clearly and continuously as highintensity areas with consensual decision making for all patients. In addition, the two
neuroradiologists also determined the anatomical points that the central nerve tracts ran
through on axial hT2w-3D-FLAIR images in all patients.
The third neuroradiologist then determined the central nerve tracts running through those
anatomical points on axial DTI color maps without reference to the hT2w-3D-FLAIR
images.
The correspondence of the detected central nerve tracts between hT2w-3D-FLAIR and
DTI was assessed as affirmation that those central nerve tracts were identical structures.
Images for this section:
Page 8 of 21
Page 9 of 21
Table 1: The parameters for hT2w-3D-FLAIR
Table 2: The parameters for DTI
Page 10 of 21
Results
The two neuroradiologists determined that the corticospinal tract (CST), medial lemniscus
(ML), and superior cerebellar peduncle (SCP) were clearly and continuously visualized
as high-intensity areas on hT2w-3D-FLAIR in all patients (Fig. 2-4).
Fig. 2: Axial (a-c: from the pontine to thalamic levels) hT2w-3D-FLAIR images of a
single patient are presented. The corticospinal tract (CST), medial lemniscus (ML),
and superior cerebellar peduncle (SCP) are visualized clearly and continuously as
high-intensity areas. The decussation of superior cerebellar peduncles (DSCP) is also
clearly visualized at the mesencephalic level.
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
Fig. 3: Coronal (a-c: from the pontine to cerebellar levels) hT2w-3D-FLAIR images of
a single patient are presented. The corticospinal tract (CST), medial lemniscus (ML),
and superior cerebellar peduncle (SCP) are visualized clearly and continuously as
high-intensity areas. The decussation of superior cerebellar peduncles (DSCP) is also
clearly visualized at the mesencephalic level.
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
Page 11 of 21
Fig. 4: Sagittal (a-c: from the left cerebellar hemisphere to median levels) hT2w-3DFLAIR images of a single patient are presented. The corticospinal tract (CST), medial
lemniscus (ML), and superior cerebellar peduncle (SCP) are visualized clearly and
continuously as high-intensity areas. The decussation of superior cerebellar peduncles
(DSCP) is also clearly visualized at the mesencephalic level.
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
In addition, those central nerve tracts ran through the following anatomical points on axial
hT2w-3D-FLAIR in all patients (Fig. 5 a, b): CST, 20 mm lateral from the lateral margin of
the third ventricle at the thalamic level (point A); ML, 6 mm anterior to the anterior margin
of the fourth ventricle at the trigeminal nerve level (point B); and SCP, just lateral to the
fourth ventricle at the trigeminal nerve level (point C).
The third neuroradiologist determined that the following central nerve tracts ran through
those anatomical points on axial DTI color maps of all patients without referring to
hT2w-3D-FLAIR (Fig. 5 c, d): (point A) CST; (point B) ML; and (point C) SCP.
The central nerve tracts determined on hT2w-3D-FLAIR and DTI thus completely
corresponded and were considered to be identical structures.
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Fig. 5: Axial hT2w-3D-FLAIR (a: the thalamic level, b: the trigeminal nerve level) and
DTI color maps (c: the thalamic level, d: the trigeminal nerve level) of a single patient
are presented. The corticospinal tract (CST), medial lemniscus (ML), and superior
cerebellar peduncle (SCP) are clearly visualized as high-intensity areas on hT2w-3DFLAIR images (a, b). These central nerve tracts run through the following anatomical
points on axial hT2w-3D-FLAIR: CST, 20 mm lateral from the lateral margin of the third
ventricle (3rd V) at the thalamic level (point A on a); ML, 6 mm anterior to the anterior
margin of the fourth ventricle (4th V) at the trigeminal nerve level (point B on b); and
SCP, just lateral to the 4th V at the trigeminal nerve level (point C on b). The following
Page 13 of 21
central nerve tracts run through these anatomical points on the axial DTI color maps:
(point A on c) CST; (point B on d) ML; and (point C on d) SCP. The central nerve tracts
observed on hT2w-3D-FLAIR and DTI color maps completely correspond, and these
central nerve tracts are considered to be identical structures.
References: Department of Radiology, Nagoya University Graduate School of
Medicine - Nagoya/JP
Images for this section:
Fig. 2: Axial (a-c: from the pontine to thalamic levels) hT2w-3D-FLAIR images of a
single patient are presented. The corticospinal tract (CST), medial lemniscus (ML), and
superior cerebellar peduncle (SCP) are visualized clearly and continuously as highintensity areas. The decussation of superior cerebellar peduncles (DSCP) is also clearly
visualized at the mesencephalic level.
Fig. 3: Coronal (a-c: from the pontine to cerebellar levels) hT2w-3D-FLAIR images of
a single patient are presented. The corticospinal tract (CST), medial lemniscus (ML),
and superior cerebellar peduncle (SCP) are visualized clearly and continuously as highintensity areas. The decussation of superior cerebellar peduncles (DSCP) is also clearly
visualized at the mesencephalic level.
Page 14 of 21
Fig. 4: Sagittal (a-c: from the left cerebellar hemisphere to median levels) hT2w-3DFLAIR images of a single patient are presented. The corticospinal tract (CST), medial
lemniscus (ML), and superior cerebellar peduncle (SCP) are visualized clearly and
continuously as high-intensity areas. The decussation of superior cerebellar peduncles
(DSCP) is also clearly visualized at the mesencephalic level.
Page 15 of 21
Fig. 5: Axial hT2w-3D-FLAIR (a: the thalamic level, b: the trigeminal nerve level) and DTI
color maps (c: the thalamic level, d: the trigeminal nerve level) of a single patient are
presented. The corticospinal tract (CST), medial lemniscus (ML), and superior cerebellar
peduncle (SCP) are clearly visualized as high-intensity areas on hT2w-3D-FLAIR images
(a, b). These central nerve tracts run through the following anatomical points on axial
hT2w-3D-FLAIR: CST, 20 mm lateral from the lateral margin of the third ventricle (3rd V)
at the thalamic level (point A on a); ML, 6 mm anterior to the anterior margin of the fourth
ventricle (4th V) at the trigeminal nerve level (point B on b); and SCP, just lateral to the
Page 16 of 21
4th V at the trigeminal nerve level (point C on b). The following central nerve tracts run
through these anatomical points on the axial DTI color maps: (point A on c) CST; (point
B on d) ML; and (point C on d) SCP. The central nerve tracts observed on hT2w-3DFLAIR and DTI color maps completely correspond, and these central nerve tracts are
considered to be identical structures.
Page 17 of 21
Conclusion
The present study revealed that the CST, ML and SCP were visualized clearly and
continuously on high-resolution hT2w-3D-FLAIR images. The results of the present
study are considered reliable because the central nerve tracts determined on hT2w-3DFLAIR completely corresponded to those visualized on DTI using less distortion readoutsegmented multi-shot EPI.
Previous studies reported that the central nerve tracts such as CST are visualized as highintensity regions on two-dimensional (2D)-spin-echo (SE)-FLAIR or 2D-SE-T2-weighted
imaging [5, 6]. In those reports, the high signals of particular central nerve tracts were
thought to arise from structural features of central nerve tracts such as unmyelinated
or sparsely myelinated fibers within the tracts [5] or the presence of large fibers with
thick myelin sheaths [6]. In addition, recent reports suggest that it is unlikely that the
visualization of central nerve tracts on 3D-FLAIR using varying flip angles is related
to noticeable inherent diffusion sensitivity [7]. In the present study, the CST, ML, and
SCP were visualized clearly and continuously on hT2w-3D-FLAIR, although the other
central nerve tracts, such as the middle cerebellar peduncle, were not clearly visualized.
Considering the descriptions in the above-mentioned literature, the results of the present
study should be due to T2 differences attributable to the structural features of particular
central nerve tracts rather than the effect of diffusion related to the direction of the nerve
fibers.
At the present moment, the methodologies of visualization or analysis of central nerve
tracts are generally based on DWI or EPI techniques [8-11]. However, DTI (which
applies DWI) is limited regarding analysis of nerve crossings. In addition, EPI is affected
strongly by magnetic susceptibility, and less distortion readout-segmented multi-shot
EPI techniques (such as RESOLVE-based sequences) have the dilemma of scan time
prolongation. hT2w-3D-FLAIR is a high-resolution and isotropic 3D-sequence that has
the possibility of becoming a novel analytic or diagnostic method for investigation of
nerve tracts; the present study revealed that particular central nerve tracts such as
the CST, ML, and SCP can be visualized continuously and clearly with strong contrast
between the surrounding structures on hT2w-3D-FLAIR. The superiority of visualization
of central nerve tracts of the brain stem on 3D-FLAIR compared to 2D-FLAIR and 2DT2-weighted imaging was recently reported [12]. Compared to this previous report, the
spatial resolutions of images in the present study were higher and had less distortion with
the readout-segmented multi-shot EPI (RESOLVE)-based sequence used in the present
study. In addition, the coronal and sagittal hT2w-3D-FLAIR images were reconstructed
from axial images, and the hT2w-3D-FLAIR images in three directions were evaluated
to investigate the continuity of the central nerve tracts in the present study. The
visibility of central nerve tracts or of the contrast between the surrounding structures on
Page 18 of 21
hT2w-3D-FLAIR may surpass those on conventional 3D-FLAIR; these are the important
comparative research issues which must be elucidated in future investigations.
The present study has some limitations. The study population of the present investigation
consisted of patients with clinically suspected Ménière's disease and did not include
healthy volunteers. The effect of delayed enhancement cannot be excluded because all
images were obtained 4 h after intravenous gadolinium injection, although it is unlikely
that the apparently normal brain parenchyma would be enhanced. These problems must
be validated in future investigations. In addition, affirmation of the validity of the central
nerve tracts with those determined to be clearly visualized on hT2w-3D-FLAIR was
performed by confirmation of correspondence with central nerve tracts visualized on DTI
obtained at the same scanning session based on anatomical knowledge, and not by
comparison with tissue specimens. However, direct real-time comparison of in vivo MRI
with histological specimens is not realistic.
In conclusion, the present study revealed that the CST, ML, and SCP were visualized
clearly and continuously on high-resolution hT2w-3D-FLAIR. hT2w-3D-FLAIR has the
possibility to become a novel and useful analytic or diagnostic method for the investigation
of nerve tracts. hT2w-3D-FLAIR offers a non-EPI, non-DWI neurographic imaging
modality.
References
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low concentration gadolinium contrast by optimized heavily T2-weighted 3D-FLAIR to
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2. Naganawa S, Yamazaki M, Kawai H, Bokura K, Sone M, Nakashima T
(2010) Visualization of endolymphatic hydrops in Meniere's disease with single-dose
intravenous gadolinium-based contrast media using heavily T(2)-weighted 3D-FLAIR.
Magn Reson Med Sci 9:237-242
3. Naganawa S, Komada T, Fukatsu H, Ishigaki T, Takizawa O (2006) Observation of
contrast enhancement in the cochlear fluid space of healthy subjects using a 3D-FLAIR
sequence at 3 Tesla. Eur Radiol 16:733-737
4. Porter DA, Heidemann RM (2009) High resolution diffusion-weighted imaging
using readout-segmented echo-planar imaging, parallel imaging and a two-dimensional
navigator-based reacquisition. Magn Reson Med 62:468-475
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5. De Coene B, Hajnal JV, Pennock JM, Bydder GM (1993) MRI of the brain stem using
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the internal capsule at MR imaging. Radiology 191:455-460
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Reson Med 67:1528-1537
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in the pontine base on T2- and multishot diffusion-weighted images in spinocerebellar
ataxia type 1. Neuroradiology 48:8-13
9. Yasmin H, Aoki S, Abe O et al (2009) Tract-specific analysis of white matter pathways
in healthy subjects: a pilot study using diffusion tensor MRI. Neuroradiology 51:831-840
10. Takahara T, Hendrikse J, Kwee TC et al (2010) Diffusion-weighted MR
neurography of the sacral plexus with unidirectional motion probing gradients. Eur Radiol
20:1221-1226
11. Naganawa S, Yamazaki M, Kawai H, Sone M, Nakashima T, Isoda H
(2011) Anatomical Details of the Brainstem and Cranial Nerves Visualized by High
Resolution Readout-segmented Multi-shot Echo-planar Diffusion-weighted Images using
Unidirectional MPG at 3T. Magn Reson Med Sci 10:269-275
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Personal Information
Masahiro Yamazaki MD, Shinji Naganawa MD, Kiminori Bokura RT, Hisashi Kawai MD
Department of Radiology,
Nagoya University Graduate School of Medicine,
Page 20 of 21
Nagoya, Japan
Address for correspondence
Masahiro Yamazaki, MD
Department of Radiology,
Nagoya University Graduate School of Medicine,
65 Tsurumai-cho, Showa-ku,
Nagoya, 466-8550,
Japan.
Telephone: +81-52-7442327
Fax: +81-52-7442335
E-mail: yamazaki@med.nagoya-u.ac.jp
Page 21 of 21