The symmetry of I 131 4‐iodoantipyrine uptake by brain after intravenous injection

Abstract

Following abrupt intravenous injection of I131 4-iodoantipyrine, its subsequent appearance in the cranium was monitored by a paired, external, collimated detection system. The symmetry of the amount of intravenous tracer appearing in each hemicranium was used as an index of the symmetry of cerebral capillary blood flow, Results in 313 cases are presented. Although uptake symmetry approximated the changes anticipated, based upon clinical evaluation, this index of hemisphere blood flow symmetry correlated poorly with clinical deficits. In 3 studies of brain isotope content in normals following carotid injection of antipyrine, the washout rates approximated those of Kr85 and Xe133. However, largely because of recirculation of antypyrine, this tracer could not easily be substituted for the gaseous radioisotopes whose recirculation is negligible following arterial injection.