Xiao-Hong Zhu1, Yi Zhang1, Hannes Wiesner2, Kamil Ugurbil1, Wei Chen1
1Center for Magnetic Resonance Research, Department of Radiology,, Minneapolis, MN, United States; 2High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tbingen, Germany
In vivo 17O MRS imaging (MRSI) approach at high/ultrahigh field has been used to non-invasively mapping the cerebral metabolic rate of oxygen (CMRO2) in small animals. However, imaging the cerebral blood flow (CBF) using the same 17O MR approach requires invasive procedures for introducing the NMR-visible H217O as exogenous tracer. In the present study, we demonstrate that the decay rate of the metabolic H217O water following a brief 17O2 gas inhalation in the CMRO2 measurement, although does not directly reflect the CBF value, is closely related to brain perfusion. A linear relationship between CBF and corresponding metabolic H217O decay rate has been determined experimentally from combined CBF and CMRO2 measurements in rat brains under varied physiological conditions. The outcomes of the study indicate that in vivo 17O MRS/MRSI approach is a useful tool for noninvasively assessing not only CMRO2 but also CBF simultaneously in the rat brain; and it provides new utilities for studying the cerebral oxygen metabolism and tissue perfusion associated with brain function and dysfunction.