Tomographic measurement of cerebral blood flow by the 68Ga-labelled-microsphere and continuous-C15O2-inhalation methods.

The measurement of cerebral blood flow (CBF) by continuous C15O2 inhalation has only been validated previously by indirect experimental protocols. In the present study using baboons, these measurements were compared directly with those obtained by injection of 68Ga-labelled serum-albumin microspheres in the left cardiac ventricle. Using a modified labelling technique, no elution of 68 Ga occurred in vivo. Both methods provided similar regional CBF values, which could be described by a significant linear correlation (CBFCO2 = 0.82 CBFmicrospheres + 5.7; P less than 0.001). The validity of the labelled-microsphere-injection method was verified. The feasibility of stable in vivo labelling of 68Ga to serum-albumin microspheres provides a reference method for organ blood-flow measurements using positron-emission tomography.