Cortical Thickness Measurements from 1.5T vs. 3T MRI in Healthy Subjects and Patients with Multiple Sclerosis (P4.179)

Objective: To evaluate differences in cortical thickness from 1.5T vs. 3T MRI in multiple sclerosis (MS) patients vs. normal controls (NC). Background: Cortical thinning on MRI is an early feature in MS and is related to neurologic impairment. The measurement of cortical thickness is challenging due to the complex anatomy involved. The growing availability of 3T and higher field strength MRI brings the potential to provide more reliable cortical segmentation. Methods: We studied 15 MS patients [11 relapsing and 4 progressive types, 12 (80[percnt]) women, age (mean±SD) 50.3±8 years, disease duration 18.5±10.4 years, Expanded Disability Status Score 3.0±2.1, timed 25-foot walk 6.1±2.6 seconds] and 15 NC [age 37.7±9.7 years, 10 (67[percnt]) women]. All subjects underwent cerebral MRI at 1.5T (GE Signa) and 3T (Siemens Skyra) using 3D-T1-weighted high resolution sequences. Cortical thickness (CTh) was measured in 68 regions across both hemispheres using the fully automated FreeSurfer pipeline. Agreement between 1.5T and 3T data was compared by estimated mean differences, standard deviation of differences, Bland-Altman plots, and Pearson9s correlation coefficients. MS vs. NC group comparisons were age-adjusted. Results: 1.5T-derived CTh showed a low agreement with 3T-derived CTh measures (Pearson’s correlations averaged 0.543). At 1.5T, the left paracentral cortex was thinner in MS vs. NC (mean 2.08 vs. 2.29 mm, p=0.045). At 3T, two cortical regions were significantly thinner in MS vs. NC [right temporal pole (mean 3.55 vs. 3.69 mm, p=0.028), left fusiform (mean 2.70 vs. 2.80 mm, p=0.047)]. Conclusion: Field strength plays a role in measuring regional cortical atrophy. 1.5T-derived CTh measures are not interchangeable with those derived from 3T MRI. 3T scans detected more areas of cortical thinning than 1.5T in patients with MS vs. healthy subjects. Disclosure: Dr. Tummala has nothing to disclose. Dr. Chu has nothing to disclose. Dr. Khalid has nothing to disclose. Dr. Dupuy has nothing to disclose. Dr. Tauhid has nothing to disclose. Dr. Healy has received research support from Merck Serono, Novartis and Genzyme. Dr. Bakshi has received research support from Biogen, EMD Serono, Novartis, Questcor, Sanofi/Genzyme, and Teva Neuroscience.