COMPARISON OF MR PERFUSION IMAGING AND MICROSPHERE MEASUREMENTS OF REGIONAL CEREBRAL BLOOD-FLOW IN A RAT MODEL OF MIDDLE CEREBRAL-ARTERY OCCLUSION

The purpose of this investigation was to correlate magnetic resonance (MR) perfusion measurements with absolute regional cerebral blood flow (rCBF) in a rat model of focal ischemia, The MR perfusion measurement s were made using dynamic first-pass bolus tracking of a susceptibilit y contrast agent, whereas rCBF was measured using radioactive microsph eres, Two simple MR perfusion parameters, the maximum change in R(2) (m Delta R(2)) and time delay to m Delta R(2)* (t Delta R(2)*), were derived from the signal intensity versus time curves on a pixel-to-pix el basis, without applying curve-fitting procedures or tracer kinetic theory; In each hemisphere, m Delta R(2) and t Delta R(2)* were compa red with the rCBF measurements in four selected regions of interest, S ixteen MR bolus tracking series were performed in 12 rats with occlusi on of the middle cerebral artery, In all of the individual series ther e was a significant correlation (.0001 less than or equal to p less th an or equal to .02) between m Delta R(2) and the microsphere rCBF mea surements, with correlation coefficients ranging from .784 to .983. Po oling the m Delta R(2) data resulted in a correlation coefficient of .809 (p = .0001), There was a nonlinear correlation between the t Delt a R(2) and rCBF, For both parameters there was considerable variation between different measurements regarding both the slope of the regres sion line and its intercept with the y-axis, Our results justify the u se of m Delta R(2) as a relative measure of perfusion during acute ce rebral ischemia, Because of the interindividual variation, calibration of MR perfusion measurements for the estimation of absolute how value s must be considered unreliable, The t Delta R(2) may have physiologi cal relevance as a marker of collateral flow. Copyright (C) 1996 Elsev ier Science Inc.