Spatial mapping of the concentrations of phosphocreatine in the human myocardium in vivo

The energy requirements for cardiac function are supplied almost entirely through oxidative phosphorylation in the mitochondria. Therefore, the consequences of ischemic heart disease are manifested in metabolic changes which are immediately detectable following an ischemic episode and occur long before anatomical changes become detectable. Specifically, a decrease in the concentration of PCr, as detected by magnetic resonance spectroscopy, is an early change due to the onset of ischemia in the myocardium. Magnetic resonance spectroscopy (MRS) is a technique which can directly measure the levels of the individual phosphorus metabolites. However, MRS is limited in spatial and temporal resolution for in vivo applications. For example, a chemical shift imaging (CSI) acquisition with a matrix size of 8 x 16 x 16 can take more than 50 minutes to acquire. We have developed a method for creating spatial maps of the levels of phosphocreatine in the human myocardium in vivo based on a fast magnetic resonance kraging technique. Two-dimensional and a three-dimensional versions were developed based on the rapid acquisition with relaxation enhancement (RARE) pulse sequence. The response of the phosphorus spin system to a series of radio frequency excitation and refocusing pulses was analyzed through simulations and verified by experiment. Several radio frequency probes were also developed for nuclear magnetic resonance (NMR) excitation of phosphorus nuclei and for the detection of the excited magnetization. An in vivo scanning protocol was developed to acquire phosphocreatine images of the myocardium of healthy volunteers. It has been demonstrated that the technique described in this dissertation can produce phosphocreatine NMR images of the human myocardium in vivo with a voxel size of 4 cm3 and a total scan time of under 10 minutes. Verification is also made by registration with proton images. The images depict anatomical features of the myocardium which have a minimum width of between 5 mm and 10 mm. The SNR within these structures ranges from 3 to 6