With the advent of mouse models to investigate cardiac physiology and pathophysiology, there is a strong need for magnetic resonance imaging (MRI) of mouse hearts. The goal of this Core is to provide a resource for measurement of cardiac function and perfusion in mice. A Core Resource is needed due to the current high cost of an MRI unit which precludes each project from obtaining its own instrumentation. In addition, A core service ensures that the experience gained from imaging one set of animals in one project will be applied to all projects. Our group was one of the first to demonstrate cardiac imaging in rats. However, there are several modifications which need to be addressed when imaging mouse hearts, due mainly to the small size of the animals (requiring better ECG acquisitions and higher image resolution) and the faster heart rates which affect the gated imaging sequences and the relative time of systole and diastole. Therefore, we have implemented and demonstrated the utility of several modifications: A specialized 3 cm diameter receive only surface radio-frequency coil was tapped onto the bottom of a plexiglass plate with three foil plates connected to ECG wires. The two front mouse paws and one back paw were taped onto the foil. Several of these were built such that one animal could be positioned and stabilized while the first was being imaged. For neonatal mouse imaging, a solenoid coil was build with ECG plates on either side for the front and back paws. High quality multi-slice images were obtained at systole and diastole, excellent correlation (r=0.97) was found between MR measurements of heart mass and mass determined at autopsy. Both diastolic and systolic images were obtained, from which ejection fractions were computed. The general methodology for the Core will flow that used previously for cardiac MRI studies in small animals. A coronal scout will be obtained from which short axis views will be prescribed. A multi-slice series of images will be obtained to cover the entire heart at 8 different time points in order to cover the heart through the cardiac cycle. From these data sets, cardiac mass, and end-diastolic/end-systolic volumes will be computed, from which ejection fractions will be derived. In order to obtain perfusion- weighted images of the myocardium, T1 weighted images will be obtained during the passage of a bolus of Gd-DTPA. In addition, magnetization prepared perfusion imaging will be implemented.
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