Abstract #4328

Restriction-induced time-varying transcytolemmal exchange rate: Revisiting diffusion MRI-based Kӓrger exchange model

Diwei Shi¹, Fan Liu², Sisi Li², Li Chen¹, Quanshui Zheng¹, Hua Guo², and Junzhong Xu^3,4,5,6

¹Center for Nano and Micro Mechanics, Department of Engineering Mechanics, Tsinghua University, Beijing, China, ²Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, ³Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ⁴Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁵Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ⁶Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States

Synopsis

Keywords: Signal Modeling, Microstructure, water exchange, quantitative microstructure imaging

Motivation: The diffusion MRI (dMRI) based two-compartmental Kӓrger exchange model is widely used to characterize transcytolemmal water exchange, but the influence of diffusion restriction remains unclear.

Goal(s): To investigate how diffusion restriction and other acquisition and microstructural parameters impact the estimation of transcytolemmal water exchange rate constants in the Kӓrger model.

Approach: Finite-difference-based numerical simulations were performed to quantitatively investigate time-varying transcytolemmal exchange rates of magnetization.

Results: When the compartmental size is large, e.g. 15 μm (close to typical cancer cell sizes), Kӓrger-model-derived exchange rate constants will be significantly dependent on time, diffusion gradient waveforms and microstructural features, resulting in overestimation of water exchange.

Impact: This work elucidates the influence of diffusion restriction on the estimation of transcytolemmal water exchange rate constants in the two-compartmental Kӓrger model, revealing that water exchange is overestimated in large compartmental sizes such as in tumors.

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