Feasibility of magnetic resonance elastography in the healthy rat heart

Purpose Develop a MR elastography (MRE) protocol to detect in vivo cardiac stiffness in rats. Methods This study was approved by the National Animal Research Authority. A healthy, adult, male Sprague-Dawley rat underwent cardiac MRE. A specialized direct shaking cardiac MRE setup and MRI protocol were designed. Stiffness was measured at 15 cardiac phases. A single midventricular slice was acquired, and intrasession variability was measured. A direct inversion of the Helmholtz equation was used to calculate the stiffness from MRE images. Results In the healthy rat, the early systolic stiffness was 2.90 kPa. The stiffness increased to the end systole (3.81 kPa), followed by a reduction during diastole to 2.61 kPa. The intrasession correlation was rho = 0.88 (p < 0.001). Conclusion This study demonstrates the feasibility of cardiac MRE in rats. Our results confirm that cardiac stiffness increases from early systole to end systole, followed by a decrease in diastole.