Patient dosimetry in diagnostic radiology-some practical considerations in an NHS region

The requirement to monitor the doses received by patients undergoing diagnostic X-ray examinations is discussed and reviewed in the context of the implementation and coordination of patient dosimetry services within an NHS Region by a regionally managed medical physics department. Four aspects of the dosimetry programme are described. Following installation of dose-area-product (DAP) meters, a region-wide data collection programme and associated database has been established, together with regular dosimetry reports. Thermoluminescence techniques are also widely employed and a complementary automated dosimetry system has been developed. Agreement between calculated and measured doses is generally within 15%. A survey of doses from or scanners in the region has resulted, in some cases, in changes in technique, in order to reduce doses. In mammography, regular assessment of 18 X-ray units has shown that mean glandular doses are consistently less than 2 mGy. An important consideration arising from the entire programme is the need to use the collected dose data to implement changes in technique if dose reduction is indicated or if NRPB reference levels are exceeded. The regionally managed programme ensures that a large database of relevant information, covering a comprehensive range of techniques and equipment, is available to a wide audience of physicists, radiographers and radiologists.