PRELIMINARY Nom JOURNAL OF NUCLEAR MEDICINE 5:883-886, 1964 Beta Radiation of Circulating Blood by an Implanted Shielded Y°°Source, A Preliminary Report of Technique

Several reports have appeared describing extracorporeal ionizing radiation of circulating blood of mammals ( 1-4). Because extracorporealization demands immobilization of the subject, precluding chronic irradiation, an attempt was made to irradiate only the circulating blood by replacing a portion of a large ar tery with a plastic graft. Around this graft was placed a metal shield containing commercially obtained Y9@'ceramic beads shielded in all directions excepting through the graft wall into the blood. TECHNIQUE With 13-15 kg dogs under general anesthesia, the abdominal aorta is ex posed below the renal arteries and a 6 cm section resected. This is replaced by a 6 cm length of 14 mm flexible woven “teflon―graft, using standard surgical technique. After blood pressure is reestablished within the graft, the shield ( shown in Fig. 1) is slipped over the graft. Twenty-five Y1@ceramic beads (approximately 1.2 mm diameter) are glued (with a quick setting epoxy), just before placement in the animal, into a groove at the crest of a longitudinal ridge of acrylic adhering to the inside wall of the stainless steel tubing opposite the opening. This ridge in dents the graft, increasing the solid angle of blood exposed to the beta source. The shield is constructed from a piece of standard stainless steel tubing from which a longitudinal section wide enough to allow placement over the graft is removed opposite the row of beads. The I.D. is 10 mm and the wall thickness 1.2 mm, just sufficient to absorb the maximum beta of @9O(226 mev). (See Fig. 1). All adjacent tissue radiation is from bremsstrahlung originating in the shield wall with lesser amounts originating in plastic and blood. If this became a prob lem with extremely large amounts of beta emitter it could be minimized b