Room: AAPM ePoster Library
Purpose: carry out treatment verification and in vivo dose measurements in intraoperative breast radiotherapy patients, treated with the Axxent (Xoft Inc.) equipment with 50 kVp of energy with XR-RV3 radiochromic films model.
Methods: measurements were performed in vivo with XR-RV3 radiochromic films in 20 patients to determine the skin dose in IORT with Axxent.Gafchromic XR-RV3 radiochromic films are specific for measurements in the low energy and high dose range, the films were calibrated following the 3-channel method (Radiochromic.com) to measure dose in vivo in patients with breast IORT. The tratment prescription is 20 Gy on the balloon surface following the TARGIT study.
Four pieces of properly oriented films were placed on each patient to obtain skin doses at different points. The pieces were placed progressively from the area closest to the applicator to the furthest The process of converting the result into dose was carried out with an Epson Expression 12000XL scanner. The films were scanned before and after irradiation with five consecutive scans in both cases, in the case of those irradiated, 24 hours after irradiation.
Results: skin doses obtained for all patients are shown in Fig 2, these doses are lower than those estimated by the TPS (Eclipse, Varian Inc.) calculated with the Axxent specific parameters of TG-43.
The doses of the film pieces placed on the balloon surface match the expected, i.e. 20 Gy, the prescribed dose.
Conclusion: skin doses are sufficiently low, which explains why in the 480 patients treated, less than 1 per cent of the cases presented early toxicity of acute grade 3 dermatitis and no case of a higher grade.The in vivo dosimetry procedure initiated will be performed with all patients measuring doses in other areas of interest from now on.