In vivo measurement of CBF using ¹⁷O NMR signal of metabolically produced H₂¹⁷O as a perfusion tracer

The cerebral metabolic rate of oxygen of small animals can be reliably imaged using the in vivo ¹⁷O magnetic resonance approach at high field. However, a separate measurement is required for imaging the cerebral blood flow in the same animal. In this study, we demonstrate that the ¹⁷O NMR signal of metabolically produced H₂¹⁷O in the rat brain following an ¹⁷O₂ inhalation can serve as a perfusion tracer and its decay rate can be used to determine the absolute values of cerebral blood flow across a wide range of animal conditions. This finding suggests that the in vivo ¹⁷O magnetic resonance approach is capable of imaging both cerebral metabolic rate of oxygen and cerebral blood flow simultaneously and noninvasively; and it provides new utilities for studying the cerebral oxygen metabolism and perfusion commonly associated with brain function and diseases.