In vivo 31P magnetic resonance spectroscopy using a needle microcoil.

Batch fabrication methods have been used to produce low-cost microcoils for magnetic resonance spectroscopy (MRS) that could be discarded after applications such as insertion into tissue during interventional surgery. Needle-shaped microcoils were constructed using electroplated conductors buried in shafts formed with different combinations of silicon and plastic and used to acquire in vivo (31)P spectra of rat thigh muscle at 81 MHz. The designs in this study achieved a maximum signal-to-noise ratio (SNR) for phosphocreatine (PCr) of 10.4 in a 10-min acquisition, with the three adenosine triphosphate (ATP) multiplets also clearly visible. An average 20% reduction in PCr occurred over a 60-min period, and intracellular pH was estimated to be 6.6, which are both evidence of ischemia. A needle microcoil design could have applications in real-time MRS of tumors or in evaluating pathology in general during surgical investigations.