Quantitative susceptibility mapping of the motor cortex: a comparison of susceptibility among patients with amyotrophic lateral sclerosis, cerebrovascular disease, and healthy controls

Abstract

Purpose: The purpose of this study was to investigate the differences in motor cortex susceptibility among patients with amyotrophic lateral sclerosis (ALS), cerebrovascular disease (CVD), and healthy controls using quantitative susceptibility mapping (QSM).

Methods: We retrospectively reviewed 78 QSM images from 26 patients with ALS, 26 age- and sex-matched patients with CVD, and 26 healthy controls. A region of interest was drawn in the hand lobule of both the motor cortexes and subcortical white matter. The relative susceptibility (RS) of the motor cortex was obtained by subtracting the susceptibility of the subcortical white matter from that of the motor cortex. We compared the cortex_mean, cortex_max, subcortical white matter_mean, RS_mean, and RS_max values among the three groups using analysis of variance and Tukey's post hoc test. Receiver operating characteristic (ROC) curve analysis was also performed.

Results: There were significant differences in the cortex_mean, cortex_max, RS_mean, and RS_max among the three groups, with higher values in patients with ALS (p = 0.01, p = 0.004, p < 0.001, and p < 0.001, respectively). Subcortical white matter_mean was significantly lower in patients with ALS compared with patients with CVD and healthy controls (p = 0.04). ROC curve analysis showed that the area under the curve of RS_mean was 0.70, the highest among the measured parameters.

Conclusion: Quantitative measurements of susceptibility of the motor cortex with QSM demonstrate its potential as an imaging biomarker in ALS patients.

Keywords: Amyotrophic lateral sclerosis; Iron; MRI; Motor cortex; Quantitative susceptibility mapping.