INTRAOPERATIVE DETECTION OF PHEOCHROMOCYTOMA WITH I-125 LABELED METAIODOBENZYLGUANIDINE - A FEASIBILITY STUDY

We evaluated the feasibility of intraoperative detection of pheochromc tcytoma sites after injection of meta-iodobenzylguanidine labelled wit h iodine-125. Six patients with multiple or recurrent pheochromocytoma were injected for intraoperative detection. During surgery, all count rates were recorded using a CdTe detector diode. Tumour foci were fou nd in all cases. Tumour count rates ranged from 50 to 1000 counts per second (mean almost-equal-to 400). Blood activity, used as a reference level, ranged from 10 to 50 counts per second (mean almost-equal-to 3 5). In all patients, the intraoperative probe was helpful to the surge on and facilitated the discovery of the pathological foci even when th ey were small (less-than-or-equal-to 1 cm). Complete resection under p robe control was correlated with postoperative normalization of urinar y normetanephrine excretion. The use of a probe designed to detect low -energy gamma-ray radionuclides bound to a highly specific molecule pr ovides an accurate detection tool which is well adapted for ectopic lo calizations and for small foci.