Jennifer Lefeuvre1,2, Qi Duan1, Jacco A de Zwart1, Peter van Gelderen1, Stéphane Lehericy2, Steven Jacobson1, Daniel S Reich1, and Govind Nair1
1NINDS, NIH, Bethesda, MD, United States, 2INSERM U1127/CNRS UMR7225, CENIR, Brain and Spine Institute, Paris, France
Synopsis
MRI of the thoracic spinal cord (t-spine) is
challenging especially due to motion, flow, and susceptibility artifacts. Improving
the image quality and resolution in t-spine has the potential to improve
visualization of anatomy, as well as lesions in neurodegenerative diseases such
as multiple sclerosis (MS). Towards this end, we have developed high-resolution
t-spine imaging techniques at 7T with a custom built RF transmit-receive coil
and navigator based frequency correction. Purpose
Imaging the t-spine at high field in
neurodegenerative disease
Introduction
MRI of the thoracic spinal cord (t-spine) is
challenging not only because of the small cross-sectional area compared to its
length, but also due to motion, flow, and susceptibility artifacts from
surrounding tissue and cerebrospinal fluid (CSF). While patients with a variety
of central nervous system diseases, such as multiple sclerosis (MS) and
HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), show
clinical symptoms originating in the t-spine, routine imaging studies generally
underestimate the extent of corresponding damage, particularly when it takes
the form of focal lesions. This may be a factor in the well described
clinico-radiological paradox, wherein clinical disability cannot be completely
explained by the imaging study
1. Improving the image quality and
resolution in t-spine has the potential to improve lesion visualization in these
diseases. We have previously reported the design of a spine array coil with an electric
dipole transmitter and 8 receive channels
2. Here we report its
application in imaging persons with MS.
Method
T-spine was imaged in one healthy volunteer (25
y.o. M) and two persons clinically diagnosed with relapsing-remitting MS (30
y.o., M and 39 y.o., F) on 3T (Siemens or Philips) and 7T MRI systems (Siemens)
for comparison. At 3T, t-spine was imaged using the spine array coil (product coil) with optimized
protocols
3 such as T1-MPRAGE in the sagittal plane (Siemens:
3D TFL,
TR/TE/TI/FA: 3000/6.8/900 ms/9°, 1 mm isotropic)
and T2*-GRE (Siemens: TR/TE/FA
= 775/11 ms/20°, in-plane resolution 0.58 mm or Philips: 2D-GRE, TR/TE/FA
= 700-804/3.2-6.4 ms/28°, in-plane resolution 0.3 mm) in the axial plane. At 7T, t-spine was imaged
using a custom-built spine array coil with T1-MPRAGE (3D TFL, TR/TE/TI/FA = 2300/1.8/950 ms/7°, 1 mm isotropic) in
the sagittal plane and both multislice T2*-GRE (TR/TE/FA = 33/9.3ms/35°, in-plane resolution of
0.31 mm, with and without navigator correction) and 3D-T2*-radial-GRE
(Siemens WIP 528L, TR/TE/FA = 20/9.2ms/10-13°, in-plane
resolution 0.27mm) in the axial plane.
Results and Discussion
The custom-built coil was found to have a
suitable excitation and receive profile to obtain good signal from the t-spine
without exceeding SAR limits in both subjects. Figure 1 A and B show comparison
of sagittal T1-MPRAGE images obtained from the 3T and 7T scanners,
respectively, in a MS patient. While MS lesions are clearly identified at both
field strengths (red arrows), they appear more conspicuous at 7T, with at least
one additional lesion only visible at the higher field strength. Anatomical
structures, including the gray and white matter, were more clearly identified at
7T (Fig 1D) than at 3T (Fig 1C) in the axial T2* images from the
healthy volunteer. Similarly, the MS lesion was better delineated, and its
location more clearly identified, on the axial T2* images from 7T (Fig
1F) compared to 3T (fig 1E).
Acknowledgements
No acknowledgement found.References
1. Barkhof, Curr Opin Neurol. 2002 Jun;15(3):239-45.
2. Duan et. al. Magn Reson Med. 2015 Oct;74(4):1189-97
3. Nair
et. al. Am J Neuroradiol. 2013 Nov-Dec; 34(11): 2215–22.