ABSOLUTE CEREBRAL BLOOD-FLOW AND BLOOD-VOLUME MEASURED BY MAGNETIC-RESONANCE-IMAGING BOLUS TRACKING - COMPARISON WITH POSITRON-EMISSION-TOMOGRAPHY VALUES

The authors determined cerebral blood flow (CBF) with magnetic resonan ce imaging (MRI) of contrast agent bolus passage and compared the resu lts with those obtained by O-15 labeled water ((H2O)-O-15) and positro n emission tomography (PET). Six pigs were examined by MRI and PET und er normo- and hypercapnic conditions. After dose normalization and int roduction of an empirical constant Phi(Gd), absolute regional CBF was calculated from MRI. The spatial resolution and the signal-to-noise ra tio of CBF measurements by MRI were better than by the (H2O)-O-15-PET protocol. Magnetic resonance imaging cerebral blood volume (CBV) estim ates obtained using this normalization constant correlated well with v alues obtained by O-15 labeled carbonmonooxide ((CO)-O-15) PET. Howeve r, PET CBV values were approximately 2.5 times larger than absolute MR I CBV values, supporting the hypothesized sensitivity of MRI to small vessels.