Estimating Aggregate Cardiomyocyte Strain Using In Vivo Diffusion and Displacement Encoded MRI

Area of Science:

• Cardiovascular imaging
• Cardiac mechanics
• Biomedical engineering

Background:

• Left ventricular (LV) cardiomyocyte orientation and deformation are critical for cardiac function.
• Existing methods lack established techniques for measuring in vivo aggregate cardiomyocyte myofiber strain.

Purpose of the Study:

• To develop and validate a pipeline for computing in vivo myofiber strain using MRI data.
• To assess the feasibility and accuracy of this pipeline in phantom and experimental settings.

Main Methods:

• Integration of multi-slice Displacement ENcoding with Stimulated Echoes (DENSE) MRI for LV motion.
• Incorporation of cardiac Diffusion Tensor Imaging (cDTI) for in vivo LV microstructure.
• Validation using an analytical deforming heart-like phantom and experimental data from healthy swine.

Main Results:

• A DENSE MRI signal-to-noise ratio (SNR) of ≥20 is required for accurate myofiber strain computation (bias < 0.06).
• Circumferential and longitudinal strains are accurately measured; radial strain shows bias.
• In vivo myofiber strain exhibits decreased transmural variability compared to radial and circumferential strains.

Conclusions:

• The validated pipeline enables accurate in vivo myofiber strain measurement.
• Myofiber strain's spatial uniformity and mechanistic significance suggest its utility for early cardiac dysfunction detection.