Comparison of MRI sequences for evaluation of multiple sclerosis of the cervical spinal cord at 3 T

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Abstract

Purpose

Debate remains regarding the utility of the traditional STIR (short inversion time recovery) sequence in aiding MRI diagnosis of spinal cord lesions in patients with multiple sclerosis (MS) and this sequence is not included in the current imaging guidelines. A recent study proposed a T1 weighted STIR as a superior alternative to the traditional STIR and T2 fast spin echo (FSE). Thus, the aim of this study was to compare the sensitivity of T2, standard STIR and T1 weighted STIR sequences in the evaluation of MS plaques on our 3 T system.

Methods and materials

A retrospective analysis of patients with multiple sclerosis who presented to our institution over a period of 5 months and who had cervical cord lesions was undertaken. Patients had been examined with our institutional protocol which included T2 FSE, STIR and the recommended T1 STIR. Quantitative analysis of the lesions versus background cord using sample T-tests was performed for each sequence, and comparative analysis of the lesion contrast:background cord ratios of the 3 sequences (using two-way ANOVA tests) was performed.

Results

The T2 sequence was not as sensitive in detecting lesions versus the traditional STIR and T1 weighted STIR, with 10% of lesions not detected using statistical analysis (p < 0.05). The traditional STIR also demonstrated greater contrast ratios than the T2 sequence (p < 0.05) suggesting increased sensitivity. However, the T1 STIR demonstrated even greater contrast ratios than both the traditional STIR and T2 sequences (p < 0.05).

Conclusion

This study confirms earlier findings of the traditional STIRs increased sensitivity versus the T2 sequence. However, the new “T1 weighted STIR” appears to be even more sensitive than both these sequences showing potential promise as an alternative method to monitor demyelinating plaques of MS.

Introduction

MRI plays a pivotal role in the early diagnosis of multiple sclerosis (MS) in patients who present with a clinically isolated syndrome. Modified Barkhof criteria, based on MRI findings, form part of the Revised McDonald's International Panel (IP) criteria when proving lesion dissemination in space and time, and were selected for their high specificity (78%) and sensitivity (73%) [1], [2]. Spinal cord imaging often forms part of the initial assessment, and is specifically recommended when presenting symptoms which occur at the level of the spinal cord do not resolve or brain MRI results are equivocal [3] as cord lesions are felt to be more specific for MS. A cervical cord lesion can substitute for one of the brain lesions when proving dissemination of lesions in space and time [4] (Table 1). Given the high prevalence (up to 90% [5], [6]) of cervical cord lesions, MRI is also used to monitor progress of disease, particularly in patients undergoing treatment with newer immunomodulatory drugs, particularly those enrolled in Phase II and III drug trials.

The current Consortium of MS Consensus Guidelines 2006 MRI cervical spine imaging protocol (Table 2) does not include the short tau inversion recovery sequence (STIR), despite earlier reports of increased sensitivity of this sequence for lesion detection [6], [7], [8], [9] and its frequent use in many centres.

The greatest criticisms of this sequence have largely arisen from 1.5 T imaging, and include increased noise, flow and movement artefact [5], [7], [8]. Recently, a so-called “TI weighted STIR” (T1STIR) with a shorter time to echo (TE) and longer time to invert (TI) than the traditional STIR, was proposed as a more sensitive inversion recovery (IR) sequence to evaluate MS plaques of the spinal cord at 3 T [10]. We therefore include this sequence in our protocol when time permits.

The aim of our study was therefore to evaluate the sensitivities of our routine protocol, which includes a traditional STIR sequence, and the “T1 weighted STIR” (T1STIR) sequence with the currently recommended T2 sequence in detecting demyelinating lesions on our 3 T system.

Section snippets

Patients

A retrospective analysis of all patients with multiple sclerosis who presented for assessment to our institution between May and October 2009 and who had visible cervical cord lesions was undertaken.

MR image acquisition

All imaging was performed with a 3.0 T Siemens imager (Trio™; Siemens Medical Solutions, Germany) equipped with a Quasar gradient system (45 mT/m with slew rate of 200 T/m/s) and a 13 element phased-array coil. All patients had been examined with the routine departmental protocol of sagittal and axial

Results

25 patients were included in this study. All 25 had been imaged with the T2 and STIR sequence, with a total of 104 ROIs from 87 lesions. Just under half of these patients (11) were imaged with all three sequences (T2, STIR and the additional TISTIR), with a total of 43 ROIS from 32 lesions.

All lesions on the STIR and T1 STIR sequence were statistically significantly different from background cord and were also all readily visible. We found approximately 10% of lesions (9/87) were not

Discussion

We found the traditional STIR sequence was 8 times more likely to show superior lesion:cord contrast ratios when compared with the FSE T2 sequence, which is consistent with the recent study which also examined these sequences at 3 T in 12 patients [10]. Our findings are also consistent with Campi et al. [7] and Hittmair et al. [8], both studies in which contrast noise ratios were calculated for 17 lesions at 1.5 T and STIR was found to be superior.

The greater statistical lesion detection rate of

Conclusion

The traditional STIR sequence shows statistically significant superior contrast ratios and superior lesion detection rate when compared with the T2 sequence at 3 T. The TISTIR sequence also shows potential as a “new” sequence to evaluate demyelinating plaques of MS at 3 T, given its statistically significant superior contrast ratios when compared with both traditional STIR and T2 sequences. These findings are consistent with those of earlier smaller studies. We propose that the current guidelines

Acknowledgements

We would like to thank A/Prof Julie Pascoe, Epidemiology and Biostatistics Unit, Department of Clinical and Biomedical Sciences, Barwon Health Campus, University of Melbourne, for her advice regarding statistical analysis.

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