Using a 'vector rotation' technique and 'parallel geometry' utility to calculate the equivalent dose rate from a patient undergoing nuclear medicine procedures

摘要

A dose calculation for a person who has been in contact with a patient undergoing Nuclear medicine procedures can be performed by using Merged Phantom Tool (MPT). In this study, we are upgrading the MPT to help users easily merge phantoms at any axis and with any angle using the "vector rotation" technique. The segmented structure information of the contact's phantom is also included in the calculation using the GEANT4 "parallel geometry" utility. The calculation is applied to a case of a male cancer patient lying on a bed who has used I-131, and a caregiver standing beside the patient. The equivalent dose to the thyroid of the caregiver is calculated at 0.3, 0.5, 0.8 and 1m away from the patient, as the caregiver is standing near the patient's abdomen, chest and neck area. The results show that the dose to the thyroid of the contact greatly depends on his standing position and that there are clear differences between the results calculated with the point source and those calculated with the patient source. In summary, using activity distributions in the patient's body as well as the right communication circumstance helps to calculate the optimal dose for people who have been in contact with patients.