In vitro and in vivo studies of 17O NMR sensitivity at 9.4 and 16.4 T.

In vivo 17O magnetic resonance spectroscopy has been successfully applied for imaging the cerebral metabolic rate of oxygen consumption through the detection of metabolically produced H2(17)O from the inhaled 17O-labeled oxygen in animals at high field. In this study, we compared the 17O sensitivity for detecting natural abundance H2(17)O signals from a phantom solution and rat brains at 9.4 and 16.4 T. The 17O signal-to-noise ratio measured at 16.4 T was 2.9- and 2.7-2.8-fold higher than that at 9.4 T for the phantom and rat brain studies, respectively. Similarly, three-dimensional 17O magnetic resonance spectroscopy imaging data showed a more than 2.7-fold higher signal-to-noise ratio in the central rat brain region at 16.4 T than that at 9.4 T. The substantial 17O signal-to-noise ratio gain at ultrahigh field significantly improved the reliability for imaging the cerebral metabolic rate of oxygen consumption and will provide an opportunity for in vivo assessment of altered oxidative metabolism associated with brain functions and neurological diseases.