Dose measurement outside of radiotherapy treatment field (Peripheral dose) using thermoluminesent dosimeters

In radiation therapy, peripheral dose or the dose outside the radiotherapy field, is important when anatomical structures with very low dose tolerances are involved. One of these critical organs in pelvic irradiation is testis. The amount of radiation delivered to the testes in radiotherapy must be kept as small as possible, consistent with the limit dose of this organ. The threshold doses for temporary and permanent sterility are 0.15 Gy and 6-8 Gy, respectively. Therefore, in pelvic irradiation, protecting testis from these doses and also scattered radiation which could escalate testis dose should be considered. In order to determine the possibility of using testicular shield for high and low energies, TLD dosimetry was done on phantom and 27 patients involved with bladder, rectum and prostate cancers. Dosimetric results showed that the ability of testicular shield in reducing testes absorbed dose is approximately the same (about 7 cGy) for low and high energy photon beams. a testicular shield with a fixed thickness of 1.27cm can be used as testis protection for either high and low energies.