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Abstract: 37-1

37-1

Individual occupational radiation dose monitoring at multiple facilities

Authors:
Andrea Marcela Castillo Arias ((CIF-RAM) UNAN-MANAGUA - Centro de Investigación de Física de Radiaciones y Metrología) ; Norma Alejandra Roas Zúniga (NA - No afiliado) ; Gustavo Ríos (NA - No afiliado)

Abstract:

Introduction: The occupational dose limit according to the international recommendations of the ICRP and adopted by the regulatory body in Nicaragua is 20 mSv per year, not to exceed 50 mSv of effective dose in a single year and 500 mSv per year for equivalent dose in skin and extremities(1-2). Regarding dose restrictions, section II of the guide for the implementation of the technical regulations for protection against ionizing radiation in the practice of conventional and interventional radiology establishes that 10 mSv per year is applied for Occupationally Exposed Workers (OEW) with working hours of 8 hours per day for 5 days per week considering 50 weeks per year. Therefore, to ensure that regulatory levels are not exceeded, it is a requirement that all OEW are under an individual monitoring program. The objective of this work is to evaluate the estimated personal equivalent dose of Hp (10) for the whole body in diagnostic imaging departments and Hp (0,07) for extremities in nuclear medicine during the year 2021 among occupational workers at multiple facilities. 

Material and methods: Information of dosimetry records of OEW of industry, diagnostic and therapeutic medicine, research, and regulation from the monitoring service provider of Nicaragua. In 2021, 155 institutions were covered between 115 private and 40 public institutions. This constitutes around 2,041 workers. Institutions in Managua (the capital city) and three provinces closest to the capital were taken into account to compare and identify occupationally exposed workers performing in two or more institutions simultaneously. The public and private diagnostic radiology departments of small and large facilities which use whole body dosimeters in Hp(10) and the nuclear medicine facilities using extremity ring dosimeters Hp(0.07), were considered.

Results and discussion: In the diagnostic imaging departments with workers using Hp(10) whole body dosimetry, 20 OEW were found in two facilities at the same time with annual Hp (10) personal equivalent doses not exceeding 3 mSv, except for one OEW with 3,45 mSv.  Furthermore, only 2 workers were found in three facilities, reporting annual personal equivalent doses Hp (10) of 2,39 mSv and 2,10 mSv. The total of institutions involved are 21, with 19 facilities located in the capital, Managua, one in the province of Masaya and two facilities in the province of Leon. 

With only two nuclear medicine facilities in the country, the service provides both Hp(10) whole body dosimetry and Hp(0,07) extremities with ring dosimeter type. Eight nuclear medicine workers were found working at both facilities, one OEW is the nuclear medicine physician, two radiopharmacy technicians, three nurses and two radiotherapy technicians with training in nuclear medicine. 75% of these OEW are female. It was found that the highest annual extremity personal dose equivalent Hp (0,07) was 181,76 mSv, corresponding to one of the radiopharmacy technicians. 

Conclusions: It was observed that the personal dose equivalent doses Hp (10) and Hp (0,07) in general do not exceed the regulatory limits. The radiation protection procedures in the facilities are considered adequate in compliance with the ALARA principle. Nevertheless, a broader study could be interesting at national level. For instance, here we only considered the provinces near the capital.

 

Keywords:
 Dose limit, Individual monitoring, Occupationally exposed workers