Magnetic resonance imaging of progressive cardiomyopathic changes in mice using a clinical 3-T MR scanner

Abstract

Objective: Due to the small size of mice hearts of less than 10mm, magnetic field strengths between 4.7-T and 11.7-T and dedicated animal scanners are recommended for cine experiments. The purpose of our study was to evaluate if a clinical 3-T MR scanner can be applied for noninvasive assessment of cardiomyopathic changes in mice. Methods: C57/BL6 mice (6w of age) underwent transverse aortic constriction (TAC, n=8) and were compared with age-matched controls (n=8). Progression of left-ventricular hypertrophy was assessed serially using a clinical 3-T MR-scanner (Achieva, Philips) applying a dedicated RF-mouse-coil once a week. Gated gradient echo sequences were used to obtain cineographic short-axis slices from apex to base with a reconstructed voxel size of 0.16×0.16×1.00mm. From these images left ventricular mass (LVM), wall thickness (WT), and ejection fraction (LVEF) were determined. MR-images were analyzed independently by two experienced radiologists. Results: In all animals changes of LVM, WT, LVEDV and LVEF could be quantified precisely with a consistent high image quality. TAC reduced the cross-sectional area of the aorta and caused pressure overload of the heart. Indicative for progressive hypertrophy MR imaging yielded higher values for LVM, WT and reduced values for LVEF in mice with TAC. Conclusion: MR imaging of mice is feasible using a clinical 3-T MR scanner in combination with a dedicated RF-mouse-coil in order to quantify progressive cardiomyopathic changes caused by TAC. This method, therefore, can be used in further studies to monitor therapeutic effects.