外科的手技を伴う非血管性IVRでの術者の手指の被ばく : Under-table tube方式とOver-table tube方式の比較

Abstract

In non-vascular interventional radiology (IVR) such as percutaneous transhepatic cholangio-drainage (PTCD) and nerve block, the operator’s hands are irradiated in primary x-ray field. In Over-table tube fluoroscopy system, operator’s hands inevitably are exposed excessively to intensive primary radiation, whereas in the Under-table tube fluoroscopy system, they are irradiated weakly by attenuated radiation through the patient’s body. For this reason, the dose to the operator’s hands in Under-table tube fluoroscopy is less than in Over-table tube fluoroscopy. This paper proposes general formulas for estimating the absorbed dose on the operator’s hands in two types of fluoroscopy. The formulas include factors affecting the absorbed dose on the operator’s hand; distance from source to the operator’s hands, x-ray transmittance of the patient and patient’s bed, and back-scatter factor of the patient. Absorbed dose to imitated operator’s hand was measured and estimated by formulas in two types of fluoroscopy for various phantom thicknesses and two field sizes using an ionization chamber. The difference between estimated absorbed dose and measured absorbed dose was less than 10%.