Estimation of multicomponent flow in the kidney with multi-b-value spectral diffusion

Area of Science:

• Diffusion MRI
• Renal Physiology
• Medical Imaging

Background:

• Kidney allograft dysfunction is a significant clinical challenge.
• Accurate assessment of perfusion, tubular flow, and tissue diffusion is crucial for monitoring allograft health.
• Current diffusion MRI techniques may not fully capture the complex intravoxel microenvironment.

Purpose of the Study:

• To examine the theory and clinical application of estimated intravoxel "flow" using multi-b-value diffusion-weighted imaging (DWI) in kidney allografts.
• To evaluate spectral diffusion MRI with multi-Gaussian fD as a flow proxy for separating perfusion, tubular flow, and tissue diffusion components.
• To compare the performance of spectral diffusion MRI against biexponential and triexponential models.

Main Methods:

• Simulated multi-b-value DWI data with anisotropic and non-Gaussian components representing vascular, tubular, and tissue elements.
• Analysis using Bayesian biexponential, least-squares triexponential, and spectral diffusion MRI models.
• Application of these models in a two-center study of 54 kidney allograft patients, correlating fD with fibrosis, kidney function (eGFR), and proteinuria.

Main Results:

• Spectral diffusion fD strongly correlated with simulated input fD for anisotropic and anomalous diffusion components.
• Spectral diffusion fD showed good agreement with both three-component (R²=0.74) and two-component (R²=0.88) diffusion models.
• In kidney allografts, higher fibrosis scores correlated with increased tissue fD (fD_tissue), impaired function with reduced tubular fD (fD_tubule), and vascular fD (fD_vasc) negatively correlated with proteinuria.

Conclusions:

• Spectral diffusion MRI with multi-Gaussian fD effectively separates distinct diffusion components in the kidney allograft microenvironment.
• The fD metric derived from spectral diffusion MRI demonstrates potential clinical utility in assessing kidney pathophysiology.
• This advanced diffusion MRI approach may offer valuable insights into transplant outcomes.