Perfusion imaging

Measurement of tissue perfusion is important for the functional assessment of organs in vivo. Here we report the use of ¹H NMR imaging to generate perfusion maps in the rat brain at 4.7 T. Blood water flowing to the brain is saturated in the neck region with a sliceselective saturation imaging sequence, creating an endogenous tracer in the form of proximally saturated spins. Because proton T₁ times are relatively long, particularly at high field strengths, saturated spins exchange with bulk water in the brain and a steady state is created where the regional concentration of saturated spins is determined by the regional blood flow and regional T₁. Distal saturation applied equidistantly outside the brain serves as a control for effects of the saturation pulses. Average cerebral blood flow in normocapnic rat brain under halothane anesthesia was determined to be 105 ± 16 cc. 100 g⁻¹. min⁻¹ (mean ± SEM, n = 3), in good agreement with values reported in the literature, and was sensitive to increases in arterial _pCO₂. This technique allows regional perfusion maps to be measured noninvasively, with the resolution of ¹H MRI, and should be readily applicable to human studies. © 1992 Academic Press, Inc.