A Headband Dosemeter for Measuring Occupational Radiation Dose to the Lens of the Eye in Terms of Hp(3)

Abstract

Abstract: The forthcoming European Basic Safety Standards directive will require member states to enforce, within four or five years, a much-reduced dose limit for the lens of the eye. The limit will be reduced from 150 millisieverts (mSv) to 20 mSv per annum (with some flexibility for averaging over five years). This change will be important for applications in the medical sector, particularly those of interventional cardiology/radiology (IC/IR). In anticipation of this, the Personal Dosimetry Service of the UK's Health Protection Agency has worked with customers from NHS Trusts and other medical-sector colleagues to produce a simple and inexpensive headband dosemeter. This paper reports on a type test of the new dosemeter. Use was made of conversion coefficients from air kerma that have recently been developed by the European ORAMED group (http://www.oramed-fp7.eu), as well as of a simple cylindrical phantom recommended by the same group. Performance was judged against the published international standard for extremity and eye dosemeters, ISO 12794, as augmented by new, tighter ORAMED recommendations. The dosemeter was found to accurately measure the required operational quantity, Hp(3), in any photon or beta fields. Because of its tissue-equivalent design, the dosemeter will also respond correctly in any mixture of such fields. The new dosemeter will provide a useful tool to assess the scale of doses to IC/IR practitioners and their teams. Because the headband dosemeter can be positioned close to the eyes, its performance relies far less on uniformity of the radiation field than would, for example, a whole body dosemeter worn on the trunk. Thus, if monitoring by means of whole body dosemeters is preferred, the headband dosemeter can be used to validate that approach.