A Noninvasive Approach to Quantitative Functional Brain Mapping with H 2 15 O and Positron Emission Tomography

Positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) with intravenously administered 15 O-labeled water and an adaptation of the Kety autoradiographic model are well suited to the study of functional-anatomical correlations within the human brain. This model requires arterial blood sampling to determine rCBF from the regional tissue radiotracer concentration ( C r ) recorded by the tomograph. Based upon the well-defined, nearly linear relation between C r and rCBF inherent in the model, we have developed a method for estimating changes in rCBF from changes in C r without calculating true rCBF and thus without arterial sampling. This study demonstrates that quantitative functional brain mapping does not require the determination of rCBF from C r when regional neuronal activation is expressed as the change in rCBF from an initial, resting-state measurement. Patterned-flash visual stimulation was used to produce a wide range of increases in rCBF within the striate cortex. Changes in occipital rCBF were found to be accurately estimated directly from C r over a series of 56 measurements on eight subjects. This adaptation of the PET/autoradiographic method serves to simplify its application and to make it more acceptable to the subject.