Whole-body distribution of radioactivity after intraperitoneal administration of 32P colloids

The whole-body distribution of radioactivity after intraperitoneal instillation of 32P-labelled chromic hydroxide particles has been studied in patients operated for early-stage ovarian cancer. Gamma-camera imaging of the abdominal 32P-distribution revealed that the administration procedure was critical for obtaining a homogeneous plating of the radiocolloids on the serosal surface. Dose calculations based on a uniform distribution of 32P in a capillary layer covering the intraperitoneal surface gave an estimated tissue surface dose of about 30 Gy per 370 MBq of 32P administered. The amount of 32P in peripheral blood increased for seven days after instillation followed by a continuous decrease. Bone marrow concentration was from two to five times as high as that in blood, but the total amounts were too small to give significant radiation doses. Gel chromatography showed that 33% of the activity in blood consisted of high molecular weight material, probably colloids. The remainder of the activity (67%) was attached to material of very low molecular weight, appearing as a consequence of physiological degradation of the colloids.