Prospective synchronization of small animal cardiac MRI: a quantitative comparison of an optical device, pressure sensor and ECG

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. 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 (1-4). For respiratory motion, an air cushion associated to a pressure sensor is commonly used and suffer from its relatively large dimension compared to mouse. By contrast with ECG and pressure, light propagation in thin optical fibers is free of any electromagnetic perturbations. In this context, this study aims to compare three different measures of heart beats and breathing using three types of sensors: (1) ECG, (2) pressure sensor via air cushion, (3) modulation of reflected light using optical fibers. Comparisons were assessed based on mouse cardiac MRI.