Diagnostic reference level: an important tool for reducing radiation doses in adult and pediatric nuclear medicine procedures in Brazil.

OBJECTIVES: This study aimed to establish a concise method for determining a diagnostic reference level (DRL) for adult and pediatric nuclear medicine patients on the basis of diagnostic procedures and administered radioisotope as a means of controlling medical exposure. METHODS: A screening was carried out in all Brazilian Nuclear Medicine Service (NMS) establishments to support this study by collecting the average activities administered during adult diagnostic procedures and the rules applied to adjust these according to the patient's age and body mass. Percentile 75 was used in all the activities administered as a means of establishing DRL for adult patients, with additional correction factors for pediatric patients. Radiation doses from nuclear medicine procedures on the basis of average administered activity were calculated for all diagnostic exams. RESULTS AND DISCUSSION: A total of 107 NMSs in Brazil agreed to participate in the project. From the 64 nuclear medicine procedures studied, bone, kidney, and parathyroid scans were found to be used in more than 85% of all the NMSs analyzed. There was a large disparity among the activities administered, when applying the same procedures, this reaching, in some cases, more than 20 times between the lowest and the highest. Diagnostic exams based on Ga, Tl, and I radioisotopes proved to be the major exams administering radiation doses to patients. On introducing the DRL concept into clinical routine, the minimum reduction in radiation doses received by patients was about 15%, the maximum was 95%, and the average was 50% compared with the previously reported administered activities. CONCLUSION: Variability in the available diagnostic procedures as well as in the amount of activities administered within the same procedure was appreciable not only in Brazil, but worldwide. Global efforts are needed to establish a concise DRL that can be applied in adult and pediatric nuclear medicine procedures as the application of DRL in clinical routine has been proven to be an important tool for controlling and reducing radiation doses received by patients in medical exposure.

Dose Calibrator Linearity Testing: Radioisotope (99m)Tc or (18)F? An Alternative for Reducing Costs in Nuclear Medicine Quality Control.

Dose calibrator linearity testing is indispensable for evaluating the capacity of this equipment in measuring radioisotope activities at different magnitudes, a fundamental aspect of the daily routine of a nuclear medicine department, and with an impact on patient exposure. The main aims of this study were to evaluate the feasibility of substituting the radioisotope Fluorine-18 ((18)F) with Technetium-99m ((99m)Tc) in this test, and to indicate it with the lowest operational cost. The test was applied with sources of (99m)Tc (62 GBq) and (18)F (12 GBq), the activities of which were measured at different times, with the equipment preadjusted to measuring sources of (99m)Tc, (18)F, Gallium-67 ((67)Ga), and Iodine-131 ((131)I). Over time, the average deviation between measured and expected activities from (99m)Tc and (18)F were, respectively, 0.56 (±1.79)% and 0.92 (±1.19)%. The average ratios for 99(m)Tc source experimental activity, when measured with the equipment adjusted for measuring (18)F, (67)Ga, and (131)I sources, in real values, were, respectively, 3.42 (±0.06), 1.45 (±0.03), and 1.13 (±0.02), and those for the (18)F source experimental activity, measured through adjustments of (99m)Tc, (67)Ga, and (131)I, were, respectively, 0.295 (±0.004), 0.335 (±0.007), and 0.426 (±0.006). The adjustment of a simple exponential function for describing (99m)Tc and (18)F experimental activities facilitated the calculation of the physical half-lives of the radioisotopes, with a difference of about 1% in relation to the values described in the literature. Linearity test results, when using (99m)Tc, through being compatible with those acquired with (18)F, imply the possibility of using both radioisotopes during linearity testing. Nevertheless, this information, along with the high potential of exposure and the high cost of (18)F, implies that (99m)Tc should preferably be employed for linearity testing in clinics that normally use (18)F, without the risk of prejudicing either the procedure itself or the guarantee of a high-quality nuclear medicine service.