No abstract

Some activities of EURADOS Working Group 9 (WG9) are presently funded by the European Commission (CONRAD project). The objective of WG9 is to promote and co-ordinate research activities for the assessment of occupational exposures to staff at workplaces in interventional radiology (IR) and nuclear medicine. For some of these applications, the skin of the fingers is the limiting organ for individual monitoring of external radiation. Therefore, sub-group 1 of WG9 deals with the use of extremity dosemeters in medical radiation fields. The wide variety of radiation field characteristics present in a medical environment together with the difficulties in measuring a local dose that is representative for the maximum skin dose, usually with one single detector, makes it difficult to perform accurate extremity dosimetry. Sub-group 1 worked out a thorough literature review on extremity dosimetry issues in diagnostic and therapeutic nuclear medicine and positron emission tomography, interventional radiology and interventional cardiology and brachytherapy. Some studies showed that the annual dose limits could be exceeded if the required protection measures are not taken, especially in nuclear medicine. The continuous progress in new applications and techniques requires an important effort in radiation protection and training.

Sealed and unsealed beta radiation sources come into use to a greater extent in radiation therapy, e.g. for treating inflammatory joint diseases by radiosynoviorthesis (RSO), by injecting 90Y, 186Re or 169Er-solutions. Sealed 90Sr/90Y and 32P-sources or 188Re-liquid-filled balloon catheter are applied in vascular brachytherapy. Recently, 90Y-labelled antibodies are being successfully used in radioimmunotherapy (RIT) of malign lymphoma. Such practices require handling of high activities at small distances to the skin. Thus, the medical staff may be exposed to high beta doses. Investigations of the extremity exposure were performed at several workplaces, in particular during RSO treatments. The local skin dose (LSD), Hp(0,07), was measured with thin-layer TLD (LiF:Mg,P,Cu) fixed to the fingers (TLD-tapes). The findings indicate that the exposure of the staff can exceed the annual dose limit of 500 mSv when working at low protection standard. Routine monitoring of the extremity exposures with ring dosemeters appropriate to beta radiation and provided by the approved German dosimetry services was found to be needed. But even monitoring with these official 'beta-dosemeters' does mostly not give suitable results to demonstrate compliance with the dose limit. A study was conducted at RSO-workplaces in order reveal a correlation between doses measured with ring dosemeters and the maximum LSD obtained from the TLD-tapes. The results are discussed and conclusions for routine monitoring are drawn.

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The Work Package 4 of the ORAMED project, a collaborative project supported by the European Commission within its seventh Framework Programme, is concerned with the optimisation of the extremity dosimetry of medical staff in nuclear medicine. To evaluate the extremity doses and dose distributions across the hands of medical staff working in nuclear medicine departments, an extensive measurement programme has been started in 32 nuclear medicine departments in Europe. This was done using a standard protocol recording all relevant information for radiation exposure, i.e. radiation protection devices and tools. This study shows the preliminary results obtained for this measurement campaign. For diagnostic purposes, the two most-used radionuclides were considered: 99m Tc and 18 F. For therapeutic treatments, Zevalin w and DOTATOC (both labelled with 90 Y) were chosen. Large variations of doses were observed across the hands depending on different parameters. Furthermore, this study highlights the importance of the positioning of the extremity dosemeter for a correct estimate of the maximum skin doses.