Code of practice for personal dosimetry of professionals wearing protective clothing during radiolog

Dutch legislation implementing the EU Council Directive 96/29/Euratom, requires record keeping of the effective dose to employees who may be exposed to more than 1 mSv of ionising radiation per year. In practice, readings from personal dosemeters (H_P(10)) are recorded in the national database (NDRIS) as an estimator of effective dose. However, the effective dose to professionals who wear protective clothing during exposure will be appreciably lower than H_P(10) measured outside the apron. It is not unusual that individual employees of certain highly exposed categories apparently exceed the annual dose limit when the effective dose is based on such measurements. To improve the estimation of effective dose some national dosimetric services in the Netherlands apply a conversion factor to the readings before registration in NDRIS whereas others do not. This impairs comparison of recorded doses. Hence it is highly desirable to apply safe standard protocols to harmonise the interpretation of measured dose values. An important condition is that such protocols should balance correctness and simplicity to promote their acceptance and application by fieldworkers, local radiation safety officers, dosimetric services and the government.

The purpose of the research project that the NCS subcommittee “Loodschorten” (lead aprons) has carried out for the Dutch Ministry of Social Affairs and Employment was to derive protocols for proper personal dosimetry when protective clothing is worn. Questions that were to be answered comprise the current situation in the Netherlands and abroad; how to estimate effective dose best from the dosemeter reading; which categories of professionals and activities are involved; under which circumstances correction of dose values should be allowed and what conversion factor should then be applied; and, finally, what is the optimal wearing position of the dosemeter.

Concisely, the following is recommended in NCS Report 19. One group of professionals is identified with a high risk of exceeding the annual dose limit when personal dosemeters are not corrected. This is the group of health care workers in interventional radiology/cardiology. When performing routine medical procedures it would be sufficient to wear a single personal dosemeter. That dosemeter should be worn at a central position high on the chest and outside the apron. Depending on the thickness of the lead apron, and the presence or absence of a thyroid collar, a conversion factor in the range of 5 to 15 can be selected, dependent on specified conditions. The dosemeter reading must be divided by this factor to yield a reasonable estimate of effective dose. Both the converted and original dose are to be recorded in NDRIS.

For the use of composite shielding material, we added an addendum to the report. 

https://doi.org/10.25030/ncs-019