Contributions
Abstract: P474
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - MRI and PET
Introduction: The corpus callosum connects the two hemispheres and is resistant to age-related change. In multiple sclerosis (MS), however, it is affected by both focal lesions and Wallerian degeneration, making it a strategic biomarker for neurodegeneration in MS. While manual delineation is the gold standard for corpus callosum measurements, there are now promising automated methods, but their robustness compared to manual measurements remains to be studied.
Aim: To compare the precision of FreeSurfer's automated volumetric corpus callosum measurements, both cross-sectional and longitudinal, against manual measurements.
Methods: A cohort of 9 MS patients (6 females, age 38±13 years, disease duration 7.3±5.2 years, 6 RR, 2 SP, 1 PP) was scanned twice with repositioning using 3D T1-weighted MRI on 3 scanners (Siemens Aera 1.5 T, Avanto 1.5 T, Trio 3.0 T), a total of 6 scans per patient, on the same day. For every scan, the normalized corpus callosum area was measured independently by two raters, a medical student and a neuroradiologist, in a randomized order. FreeSurfer's cross-sectional and longitudinal processing streams were used to measure the corpus callosum volume.
Results: For the manual measurements, there was high intra-rater (medical student 0.96, neuroradiologist 0.99) and inter-rater agreement (0.91), as measured by the intra-class correlation coefficient (all P< 0.001). The coefficient of variation of the neuroradiologist was 2.3% within scanners and 2.4% between scanners, as compared to FreeSurfer's cross-sectional method (3.7%, P=0.20; 3.8%, P=0.27) and FreeSurfer longitudinal (0.96%, P=0.025; 2.0%, P=0.48), by paired t-test. Expanded disability status scale scores were correlated with measurements from both the neuroradiologist (-0.36, P< 0.01) and longitudinal FreeSurfer (-0.36, P< 0.01) by Spearman rank. Age/sex-normalized single digit modality test scores showed similar results (neuroradiologist 0.60, P< 0.001, longitudinal FreeSurfer 0.65, P< 0.001) by Pearson correlation. Cross-sectional FreeSurfer only provided spurious or non-significant clinical correlations.
Conclusions: The manual method performs well, but FreeSurfer's longitudinal stream is significantly more precise than the manual method for within-scanner measurements. These initial results indicate that, even in a small cohort, FreeSurfer's longitudinal method outperforms manual gold standard measurements and could thus be suitable to study corpus callosum atrophy in MS.
Disclosure: Michael Platten: Nothing to disclose
Katarina Fink: KF has received an unrestricted research grant from Biogen and served on advisory boards for Teva, Roche and Merck. KF has held lectures for Merck and Biogen.
Juha Martola: Nothing to disclose
Tobias Granberg: Nothing to disclose
Abstract: P474
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - MRI and PET
Introduction: The corpus callosum connects the two hemispheres and is resistant to age-related change. In multiple sclerosis (MS), however, it is affected by both focal lesions and Wallerian degeneration, making it a strategic biomarker for neurodegeneration in MS. While manual delineation is the gold standard for corpus callosum measurements, there are now promising automated methods, but their robustness compared to manual measurements remains to be studied.
Aim: To compare the precision of FreeSurfer's automated volumetric corpus callosum measurements, both cross-sectional and longitudinal, against manual measurements.
Methods: A cohort of 9 MS patients (6 females, age 38±13 years, disease duration 7.3±5.2 years, 6 RR, 2 SP, 1 PP) was scanned twice with repositioning using 3D T1-weighted MRI on 3 scanners (Siemens Aera 1.5 T, Avanto 1.5 T, Trio 3.0 T), a total of 6 scans per patient, on the same day. For every scan, the normalized corpus callosum area was measured independently by two raters, a medical student and a neuroradiologist, in a randomized order. FreeSurfer's cross-sectional and longitudinal processing streams were used to measure the corpus callosum volume.
Results: For the manual measurements, there was high intra-rater (medical student 0.96, neuroradiologist 0.99) and inter-rater agreement (0.91), as measured by the intra-class correlation coefficient (all P< 0.001). The coefficient of variation of the neuroradiologist was 2.3% within scanners and 2.4% between scanners, as compared to FreeSurfer's cross-sectional method (3.7%, P=0.20; 3.8%, P=0.27) and FreeSurfer longitudinal (0.96%, P=0.025; 2.0%, P=0.48), by paired t-test. Expanded disability status scale scores were correlated with measurements from both the neuroradiologist (-0.36, P< 0.01) and longitudinal FreeSurfer (-0.36, P< 0.01) by Spearman rank. Age/sex-normalized single digit modality test scores showed similar results (neuroradiologist 0.60, P< 0.001, longitudinal FreeSurfer 0.65, P< 0.001) by Pearson correlation. Cross-sectional FreeSurfer only provided spurious or non-significant clinical correlations.
Conclusions: The manual method performs well, but FreeSurfer's longitudinal stream is significantly more precise than the manual method for within-scanner measurements. These initial results indicate that, even in a small cohort, FreeSurfer's longitudinal method outperforms manual gold standard measurements and could thus be suitable to study corpus callosum atrophy in MS.
Disclosure: Michael Platten: Nothing to disclose
Katarina Fink: KF has received an unrestricted research grant from Biogen and served on advisory boards for Teva, Roche and Merck. KF has held lectures for Merck and Biogen.
Juha Martola: Nothing to disclose
Tobias Granberg: Nothing to disclose