Dose rate from patients after bone and myocardial perfusion scintigraphies

Aim/Introduction: Our Nuclear Medicine (NM) department follows good practice recommendations, in particular regarding administered activities to patients The aim of this study is to ascertain whether after administering recommended activities of Technetium-99m agents, the dose rate from patients leaving the unit is below the limit suggested in the literature (50μSv/h at 1 meter) The dose rate values were obtained from patients that underwent Bone Scintigraphy (BS) with 99mTc-HMDP and Myocardial Perfusion Scintigraphy (MPS) 1 day protocol with 99mTc-Sestamibi, since these two are the most commonly performed conventional studies The study was abruptly suspended by the COVID-19 pandemia, in which only absolutely necessary tasks were performed For this reason the number of patients included is less than initially planned Nonetheless, the study will soon resume, as the unit gradually returns to its normal workflow Materials and Methods: The dose rate (μSv/h) was measured in 68 patients (BS:31;MPS:37) just before leaving the department Measurements were made with a geiger-muller detector at 1 meter from the patient anteriorly at the level of the urinary bladder, always after micturition The administered activity, time of administration, dose rate values adjusted to the background and time of measurement were registered Renal function was verified, whenever available, to better understand higher than expected values Results: As expected, dose rate values were was lower with longer intervals between injection and dose rate measurement After Bone Scintigraphy, the majority of patients left the unit more than 3h after radiopharmaceutical injection and the mean dose rate was measured at 5 6μSv/h Following Myocardial Perfusion Scintigraphy, the majority of patients left 1-2h after the second injection of 99mTc-Sestamibi with an average dose rate of 14 2μSv/h Conclusion: Keeping in mind the most recent concerns regarding administered activities to patients, as well as reducing the environmental impact factor of NM clinical practice, the data obtained demonstrates that the patients evaluated were well below the established dose-rate limits Our aim is to continue to verify the dose rate from patients leaving the department for these procedures and extend it to the rest of the procedures that we normally perform, as a standard of good clinical practice