calculation of changes in radiation exposure due to prostate displacement in permanent prostate brachytherapy

background : limited studies are available on the calculation of radiation exposure and its associated risks for people in contact with patients who have been treated with permanent prostate brachytherapy. in this study the changes in the radiation exposure were calculated in different stages of the bladder fullness in prostate seed brachytherapy. methods :magnetic resonance images of three patients with full and empty bladders and different prostate sizes (32-71 ml; mean 54.6 ml) were used for monte-carlo dose calculations. dose rate to skin for each patient was calculated using mcnp4c, mcnpx. results : there were no significant differences between dose distribution in the skin relative to the changes in the prostate position due to bladder filling (p=0.05). conclusion : our results showed a negligible change in radiation exposure around the patient due to prostate displacement after bladder filling.