Quantitative Susceptibility Mapping: Initial Experience for Multiple Sclerosis Lesion Characterization (P03.058)

Abstract

Objective: To assess whether quantitative susceptibility mapping (QSM) can function as a biomarker in patients with multiple sclerosis (MS) and provide an independent characterization of lesions commonly seen on T2-weighted images (T2WI). Background Although T2WI are used to support and confirm the clinical diagnosis of MS, T2 hyperintensity may indicate demyelination and/or edema. Previous studies have shown that iron deposition is associated with demyelination, but usually not appreciated on T2WI. Because QSM is sensitive to iron deposition, we hypothesize that QSM may provide a novel and independent biomarker in MS lesion characterization. Design/Methods: We retrospectively reviewed 181 white matter lesions in 16 consecutive confirmed MS patients (age=41±7, M/F=4/12) acquired with a protocol including T2W and QSM sequences. Lesions were identified on both T2W and QSM images with their sizes and signal intensities assessed. Differences were evaluated with a t-test. Results: A total of 181 lesions were detected on T2WI, 130(72%) of which presented on QSM. Lesion size on QSM was significantly smaller than that on T2WI(p 0.05ppm) compared to cortical gray matter. The size discrepancy was expected, since edema is hyperintense on T2WI but not on QSM. The increased signal on QSM lesions may be explained by the loss of myelin, whose susceptibility is usually negative. However, demyelination alone is unable to explain the strong paramagnetism seen in type (b) lesions, whose susceptibility is higher than cortical gray matter. In these lesions, iron may be responsible for the signal change. Further investigation may include correlation with clinical symptoms, spatial distribution of lesions, and global alternation in susceptibility value. Conclusions: MS lesions are smaller in size and demonstrate two distinct patterns on QSM when compared to routine T2WI. Disclosure: Dr. Chen has nothing to disclose. Dr. Comunale has nothing to disclose. Dr. Gauthier has received personal compensation for activities with Teva Neuroscience, Biogen Idec, Pfizer Inc, and Serono, Inc. as consultant. Dr. Gauthier has received research support from Biogen Idec, Pfizer Inc, and Serono, Inc. Dr. Heier has nothing to disclose. Dr. Liu has received personal compensation for activities with MedImageMetric LL as an employee. Dr. Tsiouris has nothing to disclose. Dr. Wang holds stock and/or stock options in MedImageMetric LLC.