Results of extremity dosimetry based on the measurements at laboratory of individual and environmental dosimetry at IFJ PAN.

Laboratory of Individual and Environmental Dosimetry (LADIS) at the Institute of Nuclear Physics is the largest dosimetry service in Poland. Extremity ring dosimetry measurements are performed at LADIS laboratory for ˃20 years, with accredited procedure since 2002. According to the quality system based on PN-EN ISO/IEC 17025:2018-02 standard, Hp(0.07) personal dose equivalent is measured over the range of doses from 0.1 mSv to 1 Sv. Years of experience allow the laboratory to analyse the levels of doses received by workers in medical and industrial institutions cooperating with LADIS laboratory. Yearly, ˃30 000 of extremity measurements have been performed for about 1000 institutions in Poland on the quarterly basis. According to the internal classification, the radiation workers under radiation protection control have been divided into a few groups. The analysis indicated that most of the doses received by exposed workers were on the level of the natural radiation background, but some of them exceeded the dose limit. The results show that ˃60% of Hp(0.07) doses were below 0.1 mSv/quarter; however, some very high doses were also registered. The highest number of doses above 125 mSv was observed in nuclear medicine and interventional radiology. The percentage of overdoses was relatively small but looking at individual cases the risk of unexpected irradiation was noticeable. Therefore, constant monitoring is always necessary.

HOW DO HOSPITAL STERILISATION PROCEDURES AFFECT THE RESPONSE OF PERSONAL EXTREMITY RINGS AND OF EYE LENS TL DOSEMETERS?

Stringent standards of hygiene must be applied in medical institutions, especially at operating blocks or during interventional radiology procedures. Medical equipment, including personal dosemeters that have to be worn by medical staff during such procedures, needs therefore to be sterilised. In this study, the effect of various sterilisation procedures has been tested on the dose response of extremity rings and of eye lens dosemeters in which thermoluminescent (TL) detectors (of types MTS-N and MCP-N, respectively) are used. The effects of medical sterilisation procedures were studied: by chemicals, by steam or by ultraviolet (UV), on the dose assessment by extremity rings and by eye lens dosemeters. Since it often happens that a dosemeter is accidentally machine-washed together with protective clothing, the effect of laundering on dose assessment by these dosemeters was also tested. The sterilisation by chemicals is mostly safe for TL detectors assuming that the dosemeters are waterproofed. Following sterilisation by water vapour, the response of these dosemeters diminished by some 30 %, irrespectively of the period of sterilisation; therefore, this method is not recommended. UV sterilisation can be applied to EYE-D™ eye lens dosemeters if their encapsulation is in black. The accidental dosemeter laundry in a washing machine has no impact on measured dose.