Diffusion in Sephadex Gel Structures: Time Dependency Revealed by Multi-Sequence Acquisition over a Broad Diffusion Time Range

Guangyu Dan, Weiguo Li, Zheng Zhong, Kaibao Sun, Qingfei Luo, Richard L. Magin, Xiaohong Joe Zhou and M. Muge Karaman
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Guangyu Dan: Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA
Weiguo Li: Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
Zheng Zhong: Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA
Kaibao Sun: Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA
Qingfei Luo: Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA
Richard L. Magin: Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
Xiaohong Joe Zhou: Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA
M. Muge Karaman: Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA

Mathematics, 2021, vol. 9, issue 14, 1-13

Abstract: It has been increasingly reported that in biological tissues diffusion-weighted MRI signal attenuation deviates from mono-exponential decay, especially at high b -values. A number of diffusion models have been proposed to characterize this non-Gaussian diffusion behavior. One of these models is the continuous-time random-walk (CTRW) model, which introduces two new parameters: a fractional order time derivative ? and a fractional order spatial derivative ? . These new parameters have been linked to intravoxel diffusion heterogeneities in time and space, respectively, and are believed to depend on diffusion times. Studies on this time dependency are limited, largely because the diffusion time cannot vary over a board range in a conventional spin-echo echo-planar imaging sequence due to the accompanying T2 decays. In this study, we investigated the time-dependency of the CTRW model in Sephadex gel phantoms across a broad diffusion time range by employing oscillating-gradient spin-echo, pulsed-gradient spin-echo, and pulsed-gradient stimulated echo sequences. We also performed Monte Carlo simulations to help understand our experimental results. It was observed that the diffusion process fell into the Gaussian regime at extremely short diffusion times whereas it exhibited a strong time dependency in the CTRW parameters at longer diffusion times.

Keywords: continuous-time random-walk; diffusion MRI; diffusion time; Sephadex gel phantom (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2021
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