Dose and dose rate measurements for radiation exposure scenarios in nuclear medicine

摘要

Radiation exposure for the staff in nuclear medicine departments is inevitable. After application of radiopharmaceuticals the patient himself becomes a radioactive source. Consequently, we need detailed information on the extent of radiation exposure for each single person dealing with radioactive sources and patients in nuclear medicine. In this work, dose rates of a variety of radioactive sources - radiopharmaceuticals and patients - in nuclear medicine were investigated. For this purpose different detectors (dosimeters, survey-meters) were used and different sources were measured for several distances between source and detector. The "radioactive patient" as a source can be considered as uncritical. However, this assumption only holds if members of the personnel keep a sufficient distance to the patient of at least 1 m. If treatments in the vicinity of the patient become necessary, the time spent in a closer distance should be limited. The handling of radiopharmaceuticals often involves close contact to the radioactive source. For the β-radiation or in the mixed β,γ-radiation field of several high energy beta emitters (~(32)P, ~(68)Ga, ~(90)Y, ~(188)Re) the ambient dose equivalent rate at 10 mm depth together with the directional dose equivalent rate at 0° and 0.07 mm depth have to be determined. Especially for the beta emitters mentioned above these dose rates are very high. For instance the specific dose rate for ~(90)Y yields 4.6 Sv/(GBqh) when dose rate measurements were performed in the closest distance to a glass vial that was practicable. Survey-meters that are only capable of measuring photons fail to provide even a rough approximation of the actual dose rate. Preparations of radiopharmaceuticals with these nuclides may consequently cause a high extremity exposure of laboratory staff. This requires measurements, demands training and a strict compliance with the established radiation safety standards.