Nederlandse Commissie voor Stralingsdosimetrie Netherlands Commission on Radiation Dosimetry

Draft publications

Code of practice for personal dosimetry of professionals wearing protective clothing during radiological procedures

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This report addresses the radiological protection of professionals who use a lead apron when being exposed to scattered X rays. High exposure concerns mainly medical staff. Observed differences in the current processing of their personal dose before registration in the national database are the report’s immediate cause. For purpose of harmonization of personal monitoring, the report contains a Code of Practice (Chapter 5), which tries to balance the correctness of the dosimetric method and the extra effort it takes to fulfil corresponding requirements.

Support of the Code of Practice by all parties involved in personal monitoring is considered very important for smooth nationwide implementation. Therefore, before finalizing the report, expert opinion is being requested. In particular, there are two important issues.

1) The values of the recommended correction factors.

It is proposed to wear a single personal dosemeter at a central position high on the chest outside the apron. The dosemeter reading should be divided by a correction factor to yield the personal dose. The correction factor depends on the thickness of the lead apron and the presence or absence of a thyroid collar. The thus obtained personal dose is a conservative estimate of effective dose. The correction factor is chosen rather low, therefore may overestimate effective dose considerably, especially for low tube voltages (e.g. 50 kV). This is a consequence of applying, for the sake of simplicity, the same value of correction factor to low and high (140) kV radiation. It is a pragmatic solution, at least for the time being, as in spite of the overestimation this correction factor will make it improbable that the recorded dose to an exposed professional will reach or exceed the annual dose limit (20 mSv/y).

A more realistic estimate of effective dose can be obtained by allowing higher values of the correction factor for lower tube voltages. Making the correction factor depend on tube voltage, however, requires extra quality control / assurance as a record of tube voltage settings must be kept. So, more correct dosimetry goes at the expense of higher administrative burden on the shop floor. Is it worth the effort?

Which choice would be preferable for the Code of Practice?

2) Will any part of the Code of Practice lead to insurmountable difficulties when implemented?

Is the proposed Code of Practice reasonable? Does it put any unjustified burden on one or more of the parties involved? Are there omissions, things unaccounted for or possibly unforeseen effects?

Please submit your comments, remarks, suggestions with conclusive arguments by e-mail to Frank Schultz, f.w.schultz@tudelft.nl, before 15 December 2007