Volume Selection Strategies for In Vivo Biological Spectroscopy

Abstract

In addition to the inherently low sensitivity of the NMR technique and low metabolite concentration, a major problem of in vivo spectroscopy has been the accurate assignment of the acquired spectrum to a specific region within the sample. Surface coils have provided one method of limiting the field of view of an NMR spectrometer, although frequently in the past in an ill-defined manner. Improvements in the use of surface coils have resulted from the introduction of multipulse techniques, the incorporation of imaging capabilities in biological spectrometers, and the use of multiple RF coils in conjunction with “depth pulses”. For most RF coil designs localization can be achieved also by the use of selective excitation in the presence of magnetic field gradients. These techniques offer complementary advantages and often can be combined to suit a particular application. There follows a brief description of several methods which use these basic volume selection techniques in various combinations.