Magnetic Resonance Imaging Evaluation of Acute Cardiovascular Disease

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Myocardial perfusion imaging continues to be an area of interest for the group. A clinical study of 25 normal subjects and 25 patients with coronary artery disease was completed this year. This study indicated the dipyridamole stress MRI studies have clinically relevant sensitivity and specificity for detection of coronary artery disease. This methodology appears to be the first clinically available approach capable of routinely differentiating endocardial from epicardial perfusion abnormalities. Patients with hypertrophic cardiomyopathy also have perfusion abnormalities that localize to the endocardium. In subjects with apparent left ventricular cavity dilatation on thallium, the MRI perfusion abnormality is primarily endocardial in the most severely hypertrophic regions rather than diffusely distributed. A validation study was completed comparing myocardial blood flow determinations by MRI and fluorescent microspheres. Myocardial contrast enhancement ratio at a fixed time interval after contrast arrival correlates well with subendocardial microsphere measurements both spatially and in terms of relative perfusion. Faster cine MRI applications have been developed using the same principles developed to accelerate MRI perfusion imaging. One technical study this year describes the principle of using short segmented echoplanar readouts to increase the efficiency of cine MRI (magnetic resonance imaging). A second technical study characterizes the optimization of imaging parameters for this methodology. These studies indicate that there is an optimal readout duration for cardiac imaging at 1.5 Tesla. On one side readout duration is bounded by signal-to-noise and scan efficiency. At longer readout durations, blood flow related artifacts and geometric distortion dominate. Experience with these faster imaging methods has allowed us to acquire volumetric data of the heart with real-time imaging and to freeze cardiac motion in immediately after bicycle exercise. We are studying vascular inflammation associated with atherosclerosis. We developed an MRI methodology designed to detect inflammation in the vascular wall. We have also determined that hypertrophic myocardium in some patients with hypertrophic cardiomyopathy is in a 3-dimensional spiral. - Magnetic resonance imaging, ischemic heart disease, myocardial ischemia, myocardial infarction, myocardial perfusion, atherosclerosis - Human Subjects