Evaluating delivered radiation dose in intraoperative radiotherapy for breast cancer using TLD

Abstract

The extra radiation that it delivers has been questioned by patients, physicians, and the public for early breast cancer patients of intraoperative radiotherapy (IORT). This investigation concerns a left breast Rando phantom with a lumpectomy cavity of 30 cm3 of left breast of Rando phantom made of polymethylmethacrylate (PMMA). Thermoluminescent dosimetry (TLD) was used to evaluate the extra radiation dose or air kerma (kair) rate under IORT from 20 Gy, 50 kV of an Xoft Axxent system. TLDs were first calibrated using 50 kV photons, and then inserted at phantom positions that were close to the positions of the represented organs and tissues. Equivalent doses (DT) delivered to the organ at risks (OAR) were evaluated according to ICRP 103. Entrance surface doses (ESD) or skin doses (Dskin) varied markedly among positions close to the lumpectomy cavity. The dose was 20 Gy at the surface of a balloon applicator and kair varied from 6.40 ± 0.92 Gy down to 1.20 ± 0.30 mGy along the left-right axis of the 17th slice of Rando. These experimental results are compared with those in the literature. The shielding effect of the tungsten-impregnated rubber was also evaluated. This study supports recommendations to patients, relatives, physicians and radiologists concerning IORT.