Cervical Spinal Cord Lesions in Multiple Sclerosis: T1-weighted Inversion-Recovery MR Imaging with Phase-Sensitive Reconstruction

This magnetic resonance (MR) imaging study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained from all participants. The purpose of the study was to prospectively compare T1-weighted inversion recovery with short inversion time inversion recovery (STIR) and dual fast spin echo (FSE) for imaging cervical spinal cord lesions in patients with multiple sclerosis (MS). Twelve patients (eight men, four women; median age, 44 years) were imaged by using T1-weighted inversion recovery, STIR, and FSE. Contrast between lesions and normal cervical cord was measured for each sequence, and generalized estimating equation analysis was used to test statistical significance of the results. Normalized contrast between lesion and normal-appearing spinal cord was significantly higher for T1-weighted inversion recovery than for the other sequences (P < .0001). Use of phase-sensitive reconstruction improved lesion localization and boundary definition. These advantages of T1-weighted inversion recovery over STIR and dual-echo FSE suggest that it has potential in cervical spinal cord imaging of MS. (c) RSNA, 2007.     

Comparison of Sagittal FSE T2, STIR,and T1-Weighted Phase-Sensitive Inversion Recovery in the Detection of Spinal Cord Lesions in MS at 3T

BACKGROUND AND PURPOSE:Determining the diagnostic accuracy of different MR sequences is essential to design MR imaging protocols. The purpose of the study was to compare 3T sagittal FSE T2, STIR, and T1-weighted phase-sensitive inversion recovery in the detection of spinal cord lesions in patients with suspected or definite MS.MATERIALS AND METHODS:We performed a retrospective analysis of 38 patients with suspected or definite MS. Involvement of the cervical and thoracic cord segments was recorded on sagittal FSE T2, STIR, and T1-weighted phase-sensitive inversion recovery sequences independently by 2 readers. A consensus criterion standard read was performed with all sequences available. Sensitivity, specificity, and interobserver agreement were calculated for each sequence.RESULTS:In the cervical cord, the sensitivity of T1-weighted phase-sensitive inversion recovery (96.2%) and STIR (89.6%) was significantly higher (P < .05) than that of FSE T2 (50.9%), but no significant difference was found between T1-weighted phase-sensitive inversion recovery and STIR. In the thoracic cord, sensitivity values were 93.8% for STIR, 71.9% for FSE T2, and 50.8% for T1-weighted phase-sensitive inversion recovery. Significant differences were found for all comparisons (P < .05). No differences were detected in specificity. Poor image quality and lower sensitivity of thoracic T1-weighted phase-sensitive inversion recovery compared with the other 2 sequences were associated with a thicker back fat pad.CONCLUSIONS:The use of an additional sagittal sequence other than FSE T2 significantly increases the detection of cervical and thoracic spinal cord lesions in patients with MS at 3T. In the cervical segment, both STIR and T1-weighted phase-sensitive inversion recovery offer high sensitivity and specificity, whereas in the thoracic spine, STIR performs better than T1-weighted phase-sensitive inversion recovery, particularly in patients with a thick dorsal fat pad.

MR imaging of the spinal cord is an important diagnostic technique in MS because the prevalence of spinal cord abnormalities in patients with clinically isolated syndrome is as high as 42%.¹ In clinically diagnosed MS, spinal cord involvement reaches 75%–92%, depending on the series.^2–4 The presence of asymptomatic cord lesions contributes to the demonstration of dissemination in space in the McDonald 2010 criteria for MS, and imaging of the spinal cord allows an increase of 18.3% in the number of patients meeting the diagnostic criteria.⁵ The presence of spinal cord lesions not only facilitates diagnosing MS but is also predictive of conversion to clinically definite MS, especially in patients with nonspinal clinically isolated syndrome who do not fulfill brain MR imaging criteria.⁶ Moreover, spinal cord lesions in MS can occur in isolation in 5% of patients, particularly in primary-progressive MS.⁷Spinal cord imaging is challenging because the spinal cord is a small and mobile structure.⁸ In addition, its anatomic location makes it prone to ghosting artifacts caused by the heart and great vessels as well as truncation artifacts. 3T MR imaging compared with 1.5T is more prone to artifacts caused by B₁ field inhomogeneity,⁹ susceptibility, vascular pulsation, and chemical shift.^10,11 In addition, 3T MR imaging has a higher energy deposit within the tissue, resulting in a higher specific absorption rate than lower field scanners. These problems can be partially solved with various technical adjustments and fast (parallel) imaging.¹²Traditionally, the spinal cord in patients with MS has been imaged by using sagittal and axial FSE T2/proton density sequences. Additional sequences, including STIR^13,14 and T1 inversion recovery,¹⁵ have shown promise by increasing lesion visibility, particularly at 3T, in which conventional FSE T2 and proton density images are frequently unsatisfactory.¹⁶ STIR has proved very useful as a complementary sequence in the detection of MS lesions but cannot be used in isolation due to its lower specificity.^13,14 Numerous studies have demonstrated the superiority of STIR over T2 at 1.5T,^{13,14,17–19} and 1 study¹⁵ also showed the advantages of STIR at 3T in the cervical cord. To our knowledge, no studies have been performed in the thoracic cord comparing sagittal FSE T2 and STIR. A recent publication showed the advantages of T1-weighted phase-sensitive inversion recovery (PSIR) for the detection of cervical spinal cord lesions in MS at 3T.¹⁶ PSIR has been shown to improve lesion localization and boundary definition over STIR in the cervical spinal cord, but it has not been tested in the thoracic cord.¹⁶The aim of our study was to compare the sensitivity and specificity of sagittal STIR, PSIR, and FSE T2 in the detection of MS spinal cord lesions at 3T, in both the cervical and thoracic segments.