Characterization of Normal Myocardial Microstructure for Healthy Women and Men Cohorts using cDTI with Ultra-High-Performance Gradient MRI Scanner

Abstract

Background: Women and men have been found to display differences in their cardiovascular anatomy and physiology, including differences in their cellular composition. While studies have shown cellular and molecular changes across sexes, few have performed sex-based studies of myocardial microstructure for healthy subjects. The purpose of this study was to quantify the myocardial microstructure in large healthy cohorts across sexes using in-vivo cardiac diffusion tensor imaging (cDTI) based on a second order motion compensated (M2) single shot spin echo sequence performed on a commercial ultra-high-performance gradient system.

Methods: In this single-centered and cross-sectional study, free breathing cDTI with a 2^nd order motion compensated spin echo diffusion-weighted imaging scheme was evaluated in 103 healthy adult subjects (mean age 33.0 years, 52 women) scanned using an MR system with maximum gradient strength of 200 mT/m. The diffusion tensor model was fit to obtain cDTI parameters including mean diffusivity (MD), fractional anisotropy (FA) and helix angle transmurality (HAT).

Results: Women and men did not show significantly different distributions of cDTI parameters (MD, FA, and HAT). Healthy subjects scanned with cDTI protocols performed on an MR system with ultra-high performance gradients have an average of 1.51±0.08 µm²/ms for MD, 0.30±0.02 for FA, and -0.77±0.09 °/% for HAT. Furthermore, women were reported to have an average MD 1.52±0.08 µm²/ms, FA 0.30±0.02, HAT -0.76±0.09 °/%. Men presented an average of MD 1.50±0.08 µm²/ms, FA 0.30±0.02, and HAT -0.77±0.09 °/% (p > 0.05 for all cDTI parameters between sexes).

Conclusion: This is the first and largest single-center study to investigate cDTI in a large cohort (N>100) of healthy subjects performed with an ultra-high-performance gradient MR system. No significant difference was discovered in MD, FA and HAT between men and women, suggesting biological sex does not impact myocardial microstructure in healthy subjects. Future work using ultra-high performance systems should focus on the evaluation of microstructural changes in patients with cardiovascular disease.

Keywords: Cardiac MRI; Diffusion Tensor Imaging; Motion Compensation; Sex Differences.