Nuclear Medicine (NM) is a medical specialty divided into diagnostic and therapeutic applications. The doses resulting from procedures in this practice come from activities administered to patients and contribute to the exposure of the population to ionizing radiation. Therefore, the optimization of radiological protection aims to balance the image quality of medical exams and the amount of radiation received by the patient, which should be optimized to the minimum value necessary for the diagnostic. The International Commission on Radiological Protection (ICRP) provides guidance on the establishment of reference levels for procedures in various modalities. In MN, diagnostic reference levels (DRLs) are based on the administered activities to patients and are considered an important tool for optimizing procedures. The objective of the present study was to estimate the typical values of administered activities resulting from Nuclear Medicine procedures performed in a private service located in the South region of Brazil. The applied methodology consisted of using secondary data retrospectively collected from the procedures registration systems in a nuclear medicine service performed in 2020. The data collected were: procedures type, radionuclide, date of the exam, administered activity (Bq), weight (kg), height (m), age (years), and gender of the patients, as well as the imaging equipment used by the service. The result obtained was average height: 1.7 m; standard deviation: 0.1; average age: 64.4 y; standard deviation 10.7; agemax. 88.0 y and agemin. 37.0 y; average weight: 79.5 kg; standard deviation:
13.5. The typical values, based on the median of administered activity (MBq) distribution of ^99mTc, on myocardial scintigraphy in the stress phase was 1,221.0 MBq and for the rest 407.0 MBq. Based on the results of the present study, we expect to encourage the establishment of an efficient routine for recording and organizing data in Santa Catarina. In addition, we would like to emphasize the benefit of optimizing the administered activities and radiation protection practices for population and individuals. Through studies like this one, we hope to contribute to the estimation of DRLs in NM in Brazil and to stimulate the creation of a culture of recording doses and activities; to help optimize the administered activities and the practices involved; as well as to contribute with the provision of data for the estimation of collective effective dose from NM examinations.

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