Radiation protection in inhomogeneous beta-gamma fields and modelling of hand phantoms with MCNPX.
The usage of beta-radiation sources in various nuclear medicine therapies is increasing. Consequently, enhanced radiation protection measures are required, as medical staff more frequently handle high-activity sources required for therapy. Inhomogeneous radiation fields make it difficult to determine absorbed dose reliably. Routine monitoring with dosimeters does not guarantee any accurate determination of the local skin dose (LSD). In general, correction factors are used to correct for the measured dose and the maximum absorbed dose received. However, strong underestimations of the maximum exposure are possible depending on the individual handling the process and the reliability of dose measurements. Simulations can be used as a tool for a better understanding of the maximum possible exposure depending on the individual-related handling. While measurements reveal the overall dose during the entire irradiation time of the dosimeter, simulations help to analyse sequences of action. Hence, simulations allow for tracking the points of highest absorbed dose received during the handling process. In this respect, simulations were performed using the MCNPX software. In order to investigate the LSD, two hand phantoms were used, a model based on geometrical elements and a voxel hand. A typical situation of radiosynoviorthesis, i.e. handling a syringe filled with (90)Y, was simulated. The results of the simulations show that the annual dose limit may be exceeded within minutes at the position of maximum absorbed dose received and that finger-ring dosimeters measure significantly different doses depending on their wearing position. It is of essential importance to wear the dosimeter properly and to use suitable correction factors with respect to the individual. Simulations are a suitable tool for ensuring reliable dose determination and may help to derive recommendations regarding radiation protection measures.
Blunck
Ch
Ch
Forschungszentrum Karlsruhe GmbH, Central Safety Department, KES, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
Becker
F
F
Hegenbart
L
L
Heide
B
B
Schimmelpfeng
J
J
Urban
M
M
D001610:Beta Particles; D003198:Computer Simulation; D005720:Gamma Rays; D006225:Hand / Q000528:radiation effects*; D006801:Humans; D008953:Models, Anatomic; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011834:Radiation Monitoring; D011835:Radiation Protection; D012867:Skin / Q000528:radiation effects; D012984:Software