Evaluation of Focal Cervical Spinal Cord Lesions in Multiple Sclerosis: Comparison of White Matter–Suppressed T1 Inversion Recovery Sequence versus Conventional STIR and Proton Density–Weighted Turbo Spin-Echo Sequences

BACKGROUND AND PURPOSE:Conventional MR imaging of the cervical spinal cord in MS is challenged by numerous artifacts and interreader variability in lesion counts. This study compares the relatively novel WM-suppressed T1 inversion recovery sequence with STIR and proton density–weighted TSE sequences in the evaluation of cervical cord lesions in patients with MS.MATERIALS AND METHODS:Retrospective blinded analysis of cervical cord MR imaging examinations of 50 patients with MS was performed by 2 neuroradiologists. In each patient, the number of focal lesions and overall lesion conspicuity were measured in the STIR/proton density–weighted TSE and WM-suppressed T1 inversion recovery sequence groups. Independent side-by-side comparison was performed to categorize the discrepant lesions as either “definite” or “spurious.” Lesion contrast ratio and edge sharpness were independently calculated in each sequence.RESULTS:Substantial interreader agreement was noted on the WM-suppressed T1 inversion recovery sequence (κ = 0.82) compared with STIR/proton density–weighted TSE (κ = 0.52). Average lesion conspicuity was better on the WM-suppressed T1 inversion recovery sequence (conspicuity of 3.1/5.0 versus 3.7/5.0, P < .01, in the WM-suppressed T1 inversion recovery sequence versus STIR/proton density–weighted TSE, respectively). Spurious lesions were more common on STIR/proton density–weighted TSE than on the WM-suppressed T1 inversion recovery sequence (23 and 30 versus 3 and 4 by readers 1 and 2, respectively; P < .01). More “definite” lesions were missed on STIR/proton density–weighted TSE compared with the WM-suppressed T1 inversion recovery sequence (37 and 38 versus 3 and 6 by readers 1 and 2, respectively). Lesion contrast ratio and edge sharpness were highest on the WM-suppressed T1 inversion recovery sequence.CONCLUSIONS:There is better interreader consistency in the lesion count on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density–weighted TSE sequences. The focal cord lesions are visualized with better conspicuity due to better contrast ratio and edge sharpness. There are fewer spurious lesions on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density–weighted TSE. The WM-suppressed T1 inversion recovery sequence could potentially be substituted for either STIR or proton density–weighted TSE sequences in routine clinical protocols.

The cervical spinal cord is commonly affected in multiple sclerosis, which is often associated with an increase in clinical disability.^1–3 A focal form of involvement is more common in the relapsing-remitting variant of MS compared with the other less common MS subtypes.⁴ MS lesions undergo complex cycles of inflammation, followed by variable extent of repair and, therefore, have heterogeneity in the prolongation of T1 and T2 relaxation times, which influence their conspicuity on the standard MR imaging sequences such as STIR and proton density–weighted TSE (PDWTSE).The PDWTSE sequence with a lower TE is better than the longer TE T2-weighted sequences in the detection of focal MS lesions in the spinal cord.^5,6 STIR has intrinsic sensitivity to T1 shortening effects in addition to T2 prolongation effects and improves the lesion contrast compared with T2-weighted sequences, translating to a better interreader agreement in the assessment of the extent of disease.⁷ Nevertheless, artifacts and lower lesion conspicuity prevalent on these sequences may cause variability in the clinical evaluation of lesion burden, which is difficult to resolve in the absence of a true reference standard.⁸ Reliable characterization of the lesion burden on follow-up examinations is therefore important for assessing treatment efficacy and optimizing treatment strategies.Many novel sequences have been devised attempting to improve imaging quality and lesion conspicuity with fewer artifacts and with a reasonable acquisition time. In a smaller study population, the WM-suppressed T1 inversion recovery (WMS) sequence has shown improvement in lesion conspicuity over STIR and dual-echo fast spin-echo.⁹ While the principles of the contrast mechanism on WMS are similar to those on STIR, the sequence parameters of WMS are optimized for better intramedullary imaging. In WMS, the section-selective inversion pulse is applied at 385 ms to suppress the background signal from white matter, whereas in STIR, it is applied at 160 ms to optimize fat suppression.¹⁰ A shorter TE is used in WMS compared with STIR or PDWTSE, which further increases the T1-weighting of the sequence, which acts as the main contrast mechanism in this long TR/short TE sequence.^11,12 MS lesions have increased T1 relaxation times and thus are not suppressed with a white matter selective inversion recovery suppression pulse. There is a need for larger scale evaluation of WMS for clinical utility in routine practice against the standard sequences (STIR and PDWTSE) in the detection of MS cord lesions. The purpose of this retrospective study was to compare the utility of WMS compared with routinely used STIR and PDWTSE sequences in the evaluation of focal cervical cord lesions is MS.