Abstract #3463

Water exchange as measured by diffusion MRI with free gradient waveforms: A potential biomarker of dendritic spine morphology

Arthur Chakwizira¹, Kadir Şimşek^2,3, Marco Palombo^2,3, Filip Szczepankiewicz¹, Linda Knutsson^1,4,5, and Markus Nilsson⁶

¹Medical Radiation Physics, Lund, Lund University, Lund, Sweden, ²Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom, ³School of Computer Science and Informatics, Cardiff University, Cardiff, United Kingdom, ⁴F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ⁵Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁶Department of Clinical Sciences Lund, Radiology, Lund University, Lund, Sweden

Synopsis

Keywords: Microstructure, Microstructure, Exchange

Motivation: Time-dependent diffusion MRI reveals fast exchange in grey matter, but it remains unclear whether permeative or non-permeative exchange explains these findings.

Goal(s): We set to investigate the effect of non-permeative exchange induced by dendritic spines on the time-dependence of the diffusion-weighted signal and the exchange estimates obtained from the signal.

Approach: Monte Carlo simulations were performed in synthetic dendrites with varying spine densities and signals were generated using free gradient waveforms. The intracellular signals were analysed using a restriction-exchange framework from previous work.

Results: Dendritic spines give the same signal time-dependence as permeative exchange. Estimated exchange rates increase with spine density.

Impact: Dendritic spines may explain the exchange rates observed with diffusion MRI in grey matter. Furthermore, exchange measurements provide a potential biomarker of dendritic spine morphology, which is important because spine density is implicated in, for example, learning and psychiatric disorders.

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