Measuring cardiomyocyte cellular characteristics in cardiac hypertrophy using diffusion-weighted MRI

Area of Science:

• Cardiovascular Imaging
• Biophysics
• Medical Physics

Background:

• Cardiac hypertrophy is a significant pathological condition.
• Accurate measurement of cardiomyocyte dimensions is crucial for understanding cardiac function and disease.
• Diffusion-weighted MRI (DWI) offers a non-invasive approach to probe tissue microstructure.

Purpose of the Study:

• To develop and validate a hierarchical modeling approach using DWI for estimating cardiomyocyte major and minor diameters and intracellular volume fraction (ICV).
• To assess the utility of these parameters as biomarkers for cardiac hypertrophy.

Main Methods:

• Acquired ex vivo mouse heart DWI data with a bespoke scheme including multiple diffusion times and q-shells.
• Fitted a bi-exponential tensor model to disentangle diffusion time and b-value dependencies.
• Extrapolated ICV at zero diffusion time using linear regression.
• Estimated cardiomyocyte diameters using a cylinder model with an elliptical cross-section (ECS).
• Validated parameters against high-resolution 3D synchrotron X-ray imaging (SRI).

Main Results:

• Estimated major diameters: 17.4-18.0 μm (control) vs. 19.0-19.2 μm (TAC).
• Estimated minor diameters: 9.4-10.2 μm (control) vs. 12.8-13.4 μm (TAC).
• Estimated ICV: 62% (control) vs. 47-68% (TAC).
• DWI-derived parameters showed consistency with SRI measurements.

Conclusions:

• The proposed hierarchical DWI modeling accurately estimates cardiomyocyte biophysical parameters.
• Cardiomyocyte diameters derived from DWI are sensitive biomarkers for detecting cardiac hypertrophy.