Beta radiation exposure of medical staff and implications for extremity dose monitoring

Abstract

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.

Spatial distribution of beta extremity doses in nuclear medicine: A feasibility study with thin α-Al2O3:C TLDs

“…The application of small and thin thermoluminescent dosimeters (TLDs) to the fingertips may aid to provide basic information on dose distribution across the extremities [12]. In particular, the TLDs based on a-Al 2 O 2 :C have shown to be promising thanks to their constant radiation response and good tissue equivalence at typical beta energies used in the nuclear medicine applications [14,15].…”

Comparison of Two Different Types of Lif:mg,cu,p Thermoluminescent Dosimeters for Detection of Beta Rays (Beta-Tlds) From 90sr/90y, 85kr and 147pm Sources

“…The plastic holder significantly influences the beta particle range, especially at the low energy of 147 Pm. In fact a thickness of 0.5 mm of plastic material is sufficient to completely stop beta particles with an average energy of 60 keV (Rimpler and Barth 2007). In this case, the ratio E mi /C for 147 Pm is less than 0.1 for both type A and type B.…”

“…The high workload and the small number of people involved in this practice can potentially lead to high absorbed dose to the skin. In fact, if the radiation protection standard in beta-emitter handling is low and staff are unaware of the local skin dose absorbed when handling such materials, the exposure may potentially exceed the annual threshold of 500 mSv (Rimpler and Barth 2007).…”

An overview on extremity dosimetry in medical applications

“…In Germany, over 60 000 RSO therapies are performed annually (35,36) . All these studies revealed that even with RSO, the highest dose is to be expected on the top of the left forefinger or thumb.…”