Abstract
To develop a fast and robust method for measuring T1 in the whole cervical spinal cord in vivo, and to assess its reproducibility. A spatially nonselective adiabatic inversion pulse is combined with zonally oblique-magnified multislice echo-planar imaging to produce a reduced field-of-view inversion-recovery echo-planar imaging protocol. Multi- inversion time data are obtained by cycling slice order throughout sequence repetitions. Measurement of T1 is performed using 12 inversion times for a total protocol duration of 7 min. Reproducibility of regional T1 estimates is assessed in a scan-rescan experiment on five heathy subjects. Regional mean (standard deviation) T1 was: 1108.5 (±77.2) ms for left lateral column, 1110.1 (±83.2) ms for right lateral column, 1150.4 (±102.6) ms for dorsal column, and 1136.4 (±90.8) ms for gray matter. Regional T1 estimates showed good correlation between sessions (Pearson correlation coefficient = 0.89 (P value < 0.01); mean difference = 2 ms, 95% confidence interval ± 20 ms); and high reproducibility (intersession coefficient of variation approximately 1% in all the regions considered, intraclass correlation coefficient = 0.88 (P value < 0.01, confidence interval 0.71-0.95)). T1 estimates in the cervical spinal cord are reproducible using inversion-recovery zonally oblique-magnified multislice echo-planar imaging. The short acquisition time and large coverage of this method paves the way for accurate T1 mapping for various spinal cord pathologies. Magn Reson Med 79:2142-2148, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Highlights
The longitudinal relaxation time T1 is one of the most fundamental quantitative parameters in MRI
We introduce an inversion recovery (IR)-based T1 mapping method for the spinal cord, making use of the sliceshuffling scheme initially developed for application to the brain [22,23]
Because a TR constraint (TR > > T1) is inherently in place with zonally oblique-magnified multislice (ZOOM)-echo-planar imaging (EPI) to avoid cross-contamination from the oblique excitation pulse, the use of such an inversion pulse has a limited time penalty compared with the normal spin-echo sequence
Summary
The longitudinal relaxation time T1 is one of the most fundamental quantitative parameters in MRI. Several studies have investigated the biological correlates of T1 It is well-established that T1 is dependent on myelin content [1]. T1 has been shown to depend on additional microstructural features with a constant total myelin volume, such as water content [2], axonal size in white matter [3], and iron concentration in gray matter [4]. Despite the lack of specificity to a single particular biological feature, T1 is sensitive to changes in tissue microstructure caused by pathologies and inflammatory events. It provides a quantitative measure comparable across subjects and centers, which is more informative than visual examination of conventional T1weighted images. The accurate knowledge of T1 serves as the basis for other quantitative MR methods (e.g., perfusion and quantitative magnetization transfer imaging) and in the optimization of imaging sequence parameters
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