Evaluation of internal exposure of nuclear medicine staff through in vivo and in vitro bioassay techniques

Abstract

The manipulation of a wide variety of unsealed sources in Nuclear Medicine results in a significant risk of internal exposure of the workers. 131I should be highlighted among the most frequently used radionuclides because of its large application for diagnosis and therapy of thyroid diseases. The increasing use of radionuclides for medical purposes creates a demand for feasible methodologies to perform occupational control of internal contamination. Currently in Brazil, there are approximately 300 nuclear medicine centres in operation but individual monitoring is still restricted to the control of external exposure. This work presents the development of in vivo and in vitro bioassay techniques aimed to quantify incorporation of radionuclides used in Nuclear Medicine. It is also presented the results of a preliminary survey of internal exposure of a group of workers involved in the preparation of therapeutic doses of 131I. Workers were monitored with a gamma camera available in the Nuclear Medicine Service of the University Hospital of Rio de Janeiro and at the Institute of Radiation Protection and Dosimetry Whole-Body Counter (IRD-WBC). The in vivo detection systems were calibrated with a neck-thyroid phantom developed in IRD. Urine samples from radiopharmacy workers were collected after preparation and administration of therapeutic doses (10-250 mCi) of 131I and measured with a HPGe detection system available in the Bioassay Laboratory of IRD. The results show that the bioassay methods developed in this work present enough sensitivity for routine monitoring of nuclear medicine workers. All workers monitored in this survey presented positive results for 131I in urine samples and two workers presented detectable activities in thyroid when measured at the IRD-WBC. The highest committed effective dose per preparation was estimated to be 17 microSv.

A Mobile Bioassay Laboratory for the Assessment of Internal Doses Based on in Vivo and in Vitro Measurements

“…(Fig. 2, right) (Lucena et al 2007). The neck-thyroid phantom is positioned on the monitoring chair of the truck using a Lawrence Livermore thorax phantom as a base.…”

Avaliação das Exposições Ocupacionais Internas em Medicina Nuclear – Dificuldades e Alternativas

“…A Posição Regulatória do Comissão Nacional de Energia Nuclear (CNEN) nº 3.01/005/2011 6 estabelece que o critério para determinar a necessidade de implantação de planos de monitoração tem como base o Safety Guide RS-G-1.2 da Agência Internacional de Energia Atômica (IAEA) 2 . A aplicação desse regulamento levaria à exigência de realização rotineira de monitoração interna em todos os trabalhadores que manipulam 131 I em medicina nuclear, criando uma grande demanda por serviços de monitoração interna 7 .…”

Simulação de uma gama-câmara para medidas de atividade de 99mTc com o código monte carlo gate

“…Diversos trabalhos desenvolvidos na Suíça [9,10,11], Brasil [12,13,14] e Polônia [15] levaram a cabo pesquisas de medições realizadas nos SMN, usando instrumentos de laboratório comumente disponíveis e que, portanto, não requerem equipamentos complexos e caros para análises quantitativas precisas, como contadores de corpo inteiro.…”