Compressed sensing (CS) MP2RAGE versus standard MPRAGE: A comparison of derived brain volume measurements.

PURPOSE: T1 Magnetization Prepared Two Rapid Acquisition Gradient Echo (MP2RAGE) with compress sensing (CS) has been proposed as an improvement of the standard MPRAGE sequence with multiple advantages including reduced acquisition time needed to provide a quantitative 3D anatomical image coupled with T1-map. Here we investigated the agreement between FreeSurfer-derived volume measurements obtained from MPRAGE and CS MP2RAGE acquisitions. METHODS: MPRAGE and CS MP2RAGE images of 37 subjects (14 patients with neurodegenerative disorders and 23 healthy controls) were acquired on a 3 T MR scanner and grey matter volumes were extracted using standard FreeSurfer parcellation. Lin's concordance correlation coefficient (Lin's CCC), Bland-Altman analysis, Passing-Bablok regression and DICE similarity coefficient were calculated to assess the agreement between the two. RESULTS: We found a good correspondence for most of the regions examined, with 93.5 % of them showing a mean DICE index >0.70. Poorer results were found with Lin's CCC especially for subcortical labels across patients. The Bland-Altman analysis showed CS MP2RAGE tended to measure lower cortical volumes compared to MPRAGE but in most cases the difference wasn't statistically relevant. The Passing-Bablock regression indicated overall an absence of systematic constant and proportional bias when CS MP2RAGE was used instead of MPRAGE. CONCLUSIONS: We found a good concordance for volumes obtained from MPRAGE and CS MP2RAGE images using FreeSurfer, suggesting a possible role of CS MP2RAGE for structural analysis with significant advantages like shorter acquisition time and the possibility to simultaneously obtain quantitative T1-maps of the brain enriching the diagnostic power of this technique.

18F-FDG-PET correlates of aging and disease course in ALS as revealed by distinct PVC approaches.

PURPOSE: The partial volume effect (PVE) complicates PET studies of neurodegenerative diseases, since a decreased 18F-FDG retention might be influenced by atrophy-related changes of cortical regions. Multiple partial volume correction (PVC) methods have been therefore developed, but their application in amyotrophic lateral sclerosis (ALS) is still rare. Additionally, even if metabolic changes have been established in ALS, no study yet has investigated how these may be influenced by aging and disease course. The aim of the present study was therefore to apply and compare multiple PVC approaches to explore aging and disease course-related hypometabolism in ALS. METHODS: PET and MRI data from 15 ALS patients were analyzed using PETSurfer to implement 4 distinct PVC methods: noPVC, Meltzer (MZ), Müller-Gärtner (MG) and Symmetric Geometric Transfer Matrix (SGTM). For each method and Region of Interest (ROI), the 18F-FDG value was regressed against subject age and disease duration. RESULTS: MG/SGTM application almost halved the number of regions showing a significant age-related hypometabolism, while the same effect was not observed for disease course, where only the distribution of identified regions varied. Three distinct patterns emerged: regions showing a significant age/disease course-related effect across all the different methods, regions yielding significance only with MG/SGTM application, and regions maintaining significance only with noPVC/MZ application. CONCLUSIONS: Significant changes in the distribution of aging and disease course-related hypometabolism were observed when the effect of the underlying structural status was considered, supporting the need for investigate the impact of PVE on PET-assessed metabolic changes in clinical and research settings.

CSF oligoclonal bands and normal appearing white matter periventricular damage in patients with clinically isolated syndrome suggestive of MS.

BACKGROUND: A periventricular gradient of normal appearing white matter (NAWM) damage has been described in multiple sclerosis (MS), including subjects with clinically isolated syndrome (CIS). The pathological mechanisms underlying this gradient is not currently understood. METHODS: 34 CIS subjects were enrolled and underwent cerebrospinal fluid oligo-clonal bands (CSF-OCB) evaluation. Moreover, all CIS subjects and 24 healthy controls underwent a brain MRI scan. Diffusion weighted imaging was used to compute mean diffusivity (MD) values in periventricular and deep NAWM for all groups. RESULTS: CSF-OCB were present in 24 CIS subjects (CSF-OCB+) out of 34 tested. Periventricular NAWM MD values were significantly higher in CIS subjects with than in those without CSF-OCB (0.78 ± 0.06 mm3/10-3 vs. 0.72 ± 0.06 mm3/10-3; p = 0.01), while there was no difference between groups in deep NAWM MD values. The periventricular gradient of damage, expressed in z score based on healthy controls data, was more marked in CSF-OCB+ than in CSF-OCB- (0.65 ± 0.05 vs. 0.17 ± 0.04 p < 0.001). There was no difference in periventricular lesion load between the two groups. CONCLUSIONS: In CIS, the presence of CSF-OCB is associated with the severity of periventricular NAWM damage gradient. Intrathecal inflammation could play a role in NAWM damage distribution.