Biology subjects

Feinberg, D. A.

Publications and source records attributed to Feinberg, D. A..

3 recordsLinked to original sources

bioRxiv2025

Advancing High-Resolution 7T Diffusion MRI: Evaluating Phase-Encoding Correction Strategies for Distortion Correction from Basic to Four-Way Acquisitions

PurposeHigh-resolution 7T diffusion MRI (dMRI) is limited by image artifacts that compromise anatomical accuracy. The purpose of this study was to systematically evaluate phase-encoding (PE) acquisition and correction strategies to determine which methods best mitigate geometric distortions and improve data reproducibility. MethodsFive healthy adults were each scanned twice on a 7T MRI scanner (0.9 mm isotropic resolution), using a highly oversampled dMRI protocol with four PE directions (AP, PA, RL, LR). From this dataset, we created and processed eleven time-equivalent, 10-minute acquisitions, ranging from uncorrected single-PE data to comprehensive 4-way PE schemes. These strategies were quantitatively compared on their geometric alignment with T1-weighted images and on the scan-rescan reproducibility of DTI-derived metrics. Results(1) All distortion-corrected schemes significantly improved geometric accuracy over uncorrected data; (2) Strategies correcting with a full set of reversed-PE (2-way) diffusion weighted images (DWIs) outperformed the common approach of using only a single reversed b=0 image; and (3) a 4-way PE acquisition consistently provided the highest image fidelity and reproducibility. The optimized acquisition enabled high-quality reconstruction of both long-range and fine-scale superficial white matter pathways. ConclusionFor high-resolution 7T dMRI, multi-PE acquisition is essential to achieve accurate geometry and stable microstructural estimates (i.e., less residual EPI distortion and better scan-rescan agreement). A 4-way PE scheme provides the most accurate and reproducible results for microstructural and connectivity modeling. Data statementData will be made available in BIDS format upon acceptance of the manuscript. To be updated with DOI.

neuroscience↗

bioRxiv2025

Functional imaging of hippocampal layers using VASO and BOLD on the Next Generation (NexGen) 7T Scanner

Spatial accuracy and venous biases are a central concern in mesoscale fMRI, with subcortical brain regions facing additional challenges due to lower sensitivity, high physiological noise, and complicated vasculature. Here, we optimized CBV VASO on the NexGen 7T scanner for layer-specific investigations of the human hippocampus. Both VASO and BOLD (from the same acquisition) detected significant hippocampal activation during an established autobiographical memory task. At the macroscale, activation patterns converged, showing pronounced memory task activation in the anterior hippocampus and consistent engagement across the frontoparietal neocortex. At the laminar scale, however, differences in depth-dependent profiles emerged within the subiculum: BOLD exhibited a pronounced bias toward the inner layers, consistent with the known venous drainage pattern in the subfield. Finally, the optimized effective TR of 3.2 s allowed exploratory study of retrieval stages and neocortical functional connectivity, which both supported hippocampal anterior-posterior dissociation using both VASO and BOLD. Thus, hippocampal fMRI allows mapping layer function with high accuracy and can provide deeper insights into a number of neuropsychological phenomena and disorders. Key pointsO_LIOptimized CBV VASO on NexGen 7T for layer-specific hippocampal imaging C_LIO_LIVASO mitigates structural venous bias in subiculum present in BOLD C_LIO_LILong-axis mapping dissociates retrieval stages and neocortical connectivity patterns C_LI

neuroscience↗

bioRxiv2019

Comparison of BOLD and CBV using 3D EPI and 3D GRASE for cortical layer fMRI at 7T.

PurposeFunctional MRI (fMRI) at the mesoscale of cortical layers and columns requires both sensitivity and specificity, which can be compromised if the imaging method is affected by vascular artifacts, particularly cortical draining veins at the pial surface. Recent studies have shown that cerebral blood volume (CBV) imaging is more specific to the actual laminar locus of neural activity than BOLD imaging when using standard gradient-echo (GE) EPI sequences. Gradient and Spin Echo (GRASE) BOLD imaging has also shown greater specificity when compared with GE-BOLD.\n\nMethodsHere we directly compare CBV and BOLD contrasts in high-resolution imaging of the primary motor cortex for laminar fMRI in four combinations of signal labeling, VASO (CBV) and BOLD with 3D GE-EPI and zoomed 3D GRASE image readouts.\n\nResultsWe find that both CBV imaging using EPI-VASO and BOLD imaging using GRASE-BOLD, show similar specificity and sensitivity and are thus useful tools for mesoscopic fMRI in the human cortex.\n\nConclusionThese techniques demonstrate sufficient sensitivity and specificity to allow layer-fMRI to be used by neuroscientists in a wide range of investigations of depth-dependent neural circuitry in the human brain.

neuroscience↗