Lutetium-177 (DOTATATE) (177Lu; T1/2 6.7 days), a labelled β- and Auger-electron emitter, is widely used in treatment of neuroendocrine tumours. During performance of the procedure, staff and other patients can potentially receive significant doses in interception of the gamma emissions [113 keV (6.4%) and 208 keV (11%)] that are associated with the particle decays. While radiation protection and safety assessment are required in seeking to ensure practices comply with international guidelines, only limited published studies are available. The objectives of present study are to evaluate patient and occupational exposures, measuring ambient doses and estimating the radiation risk. The results, obtained from studies carried out in Riyadh over an 11 month period, at King Faisal Specialist Hospital and Research Center, concerned a total of 33 177Lu therapy patients. Patient exposures were estimated using a calibrated Victoreen 451P survey meter (Fluke Biomedical), for separations of 30 cm, 100 cm and 300 cm, also behind a bed shield that was used during hospitalization of the therapy patients. Occupational and ambient doses were also measured through use of calibrated thermoluminescent dosimeters and an automatic TLD reader (Harshaw 6600). The mean and range of administered activity (in MBq)) was 7115.2 ± 917.2 (4329-7955). The ambient dose at corridors outside of therapy isolation rooms was 1.2 mSv over the 11 month period, that at the nursing station was below the limit of detection and annual occupational doses were below the annual dose limit of 20 mSv. Special concern needs to be paid to comforters (carers) and family members during the early stage of radioisotope administration.
This study has sought to evaluate patient exposures during the course of particular diagnostic positron emission tomography and computed tomography (PET/CT) techniques. A total of 73 patients were examined using two types of radiopharmaceutical: 18F-fluorocholine (FCH, 48 patients) and 68Ga-prostate-specific membrane antigen (PSMA, 25 patients). The mean and range of administered activity (AA) in MBq, and effective dose (mSv) for FCH were 314.4 ± 61.6 (462.5-216.8) and 5.9 ± 1.2 (8.8-4.11), respectively. Quoted in the same set of units, the mean and range of AA and effective dose for 68Ga-PSMA were 179.3 ± 92.3 (603.1-115.1) and 17.9 ± 9.2 (60.3-11.5). Patient effective doses from 18F-FCH being a factor of two greater than the dose resulting from 68Ga-PSMA PET/CT procedures. CT accounts for some 84 and 23% for 18F-FCH and 68Ga-PSMA procedures, accordingly CT acquisition parameter optimization is recommended. Patient doses have been found to be slightly greater than previous studies.
Worldwide, thyroid cancer accounts for some 10% of total cancer incidence, most markedly for females. Thyroid cancer radiotherapy, typically using 131I (T1/2 8.02 days; β- max energy 606 keV, branching ratio 89.9%), is widely adopted as an adjunct to surgery or to treat inoperable cancer and hyperthyroidism. With staff potentially receiving significant doses during source preparation and administration, radiation protection and safety assessment are required in ensuring practice complies with international guidelines. The present study, concerning a total of 206 patient radioiodine therapies carried out at King Faisal Specialist Hospital and Research Center over a 6-month period, seeks to evaluate patient and occupational exposures during hospitalization, measuring ambient doses and estimating radiation risk. Using calibrated survey meters, patient exposure dose-rate estimates were obtained at a distance of 30-, 100- and 300 cm from the neck region of each patient. Occupational and ambient doses were measured using calibrated thermoluminescent dosimeters. The mean and range of administered activity (AA, in MBq) for the thyroid cancer and hyperthyroidism treatment groups were 4244 ± 2021 (1669-8066), 1507.9 ± 324.1 (977.9-1836.9), respectively. The mean annual occupational doses were 1.2 mSv, that for ambient doses outside of the isolation room corridors were found to be 0.2 mSv, while ambient doses at the nursing station were below the lower limit of detection. Exposures to staff from patients being treated for thyroid cancer were less compared to hyperthyroidism patients. With a well-defined protocol, also complying with international safety requirements, occupational exposures were found to be relatively high, greater than most reported in previous studies.