A comparison of in vivo MRI based cortical myelin mapping using T1w/T2w and R1 mapping at 3T

Abstract

In this manuscript, we compare two commonly used methods to perform cortical mapping based on myelination of the human neocortex. T1w/T2w and R1 maps with matched total acquisition times were obtained from a young cohort in randomized order and using a test–retest design. Both methodologies showed cortical myelin maps that enhanced similar anatomical features, namely primary sensory regions known to be myelin rich. T1w/T2w maps showed increased robustness to movement artifacts in comparison to R1 maps, while the test re-test reproducibility of both methods was comparable. Based on Brodmann parcellation, both methods showed comparable variability within each region. Having parcellated cortical myelin maps into VDG11b areas of 4a, 4p, 3a, 3b, 1, 2, V2, and MT, both methods behave identically with R1 showing an increased variability between subjects. In combination with the test re-test evaluation, we concluded that this increased variability between subjects reflects relevant tissue variability. A high level of correlation was found between the R1 and T1w/T2w regions with regions of higher deviations being co-localized with those where the transmit RF field deviated most from its nominal value. We conclude that R1 mapping strategies might be preferable when studying different population cohorts where cortical properties are expected to be altered while T1w/T2w mapping will have advantages when performing cortical based segmentation.

Effects of MP2RAGE B1+sensitivity on inter-site T1reproducibility and morphometry at 7T

“…Interestingly, we detected a similar offset between left and right hemispheric T 1 across acquisition sites, with higher values observed for the left hemisphere. This follows the inter-hemispheric differences with lower R 1 (i.e., higher T 1 ) values for the left hemisphere observed by Shams et al (2019), across different field strengths (Kim et al, 1994;Marques et al, 2017;Wansapura et al, 1999), and which could not solely be explained by the asymmetric B 1 + field. In fact, our results show that this difference intensifies after cleaning up remaining B 1 + residuals.…”

Overlooked tertiary sulci serve as a meso-scale link between microstructural and functional properties of human lateral prefrontal cortex

“…To test this, we first extracted and compared average MRI T1w/T2w ratio values from each sulcus. The T1w/T2w ratio is a tissue contrast enhancement index that is correlated with myelin content (Figure 3a; (Glasser and Van Essen, 2011;Shams et al, 2019). We chose this index because myeloarchitecture is a classic criterion used to separate cortical areas from one another (Vogt and Vogt, 1919;Flechsig, 1920;Hopf, 1956;Dick et al, 2012).…”

Macromolecular tissue volume mapping of lateral geniculate nucleus subdivisions in living human brains

“…In both cases, we found that coordinates for the centers of the M and P subdivisions in the majority of subjects were inconsistent with those obtained using the histological data (BigBrain), suggesting that these maps were not sufficient for parcellating the M and P subdivisions in the LGN. This most likely occurred because these values are prone to measurement biases (Shams et al, 2019). The unsuccessful parcellation of the M and P subdivisions using the PD weighted images or T1w/T2w maps indicated the advantage of acquiring MTV data for…”