Magnetic resonance spectroscopy of the heart

MRS has clearly established itself as an important investigative tool for the study of cardiac metabolism and energetics. In animal models, it can provide insight into basic metabolic processes in both health and disease. Its nondestructive nature and capacity for serial measurements in the same system have given scientists the ability to monitor changes in biologic systems over time, while its ability to measure different nuclei, and hence different metabolic processes, gives it immense flexibility. In relative contrast to animal studies, human cardiac MRS is in its infancy. To date, cardiac 31P spectroscopy has been successfully implemented in only a few centers. These studies have primarily examined normal subjects to establish the feasibility of such examinations with a variety of techniques. The few reports of metabolic abnormalities detected by 31P NMR have been limited by problems of accurate spatial localization and large sample volumes. The ultimate utility of human spectroscopy, with phosphorus or any other nucleus, will depend on the success of efforts to increase the sensitivity and spatial selectivity of the NMR experiment. These efforts include utilizing systems of higher field strength and homogeneity, as well as improving pulse sequences and radio frequency coil designs. In addition, demonstration of some degree of sensitivity and specificity of metabolic abnormalities in disease states will be necessary before clinical use is indicated. If these requirements are met, human cardiac spectroscopy may provide useful information about cardiac metabolic processes and, combined with proton NMR imaging, may enable complete noninvasive evaluation with one technology. The rapid advances over the past few years attest to the feasibility of this goal.