Mouse cardiac MRI: comparison of prospective synchronization using optical and ECG signals with a retrospective technique

Introduction Prospective synchronization on living organisms of MRI acquisitions to reduce the motion artifacts involves the monitoring of both respiratory and heart motions in the thorax and abdominal region. The signal conventionally used to measure cardiac cycle is the electrocardiograph (ECG) signal. Respiratory motion can be derived from low frequency modulation of ECG signal [1]. Because of the weak amplitude of the ECG signal recorded on small animals, to obtain an uncorrupted ECG (RF pulses and gradient switching) is challenging [2-4]. By contrast with ECG, light propagation in thin optical fibers is free of any electromagnetic perturbation. On another hand, retrospective techniques based on navigated-echoes do not require sensors and are well suited with CINE FLASH sequences. In this context, this study aims to compare the prospective techniques of heart beats and breathing monitoring using two types of sensors: (a) modulation of reflected light using optical fibers and (b) ECG with (c) a retrospectives technique. Comparisons were assessed based on mouse cardiac CINE FLASH MRI.