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Objective:To design a drum-shaped applicator through Monte Carlo simulation for breast intraoperative radiotherapy.Methods:Applicator designing process is as follows: first, determined the shape of the applicator based on the geometric characteristics of the breast tumor bed closed to the chest wall; second, calculated the scattering angle and dose rate of the electron beam after passing through a series of scattering foils of different thicknesses to determine the thickness of the scattering foil; thrid, modeled the layer according to the applicator′s geometric characteristics where modulator located, and designed the modulator through the relationship between the geometric characteristics of the layer and the surface dose of the applicator. EGSnrc/BEAMnrc and EGS4/DOSXYZ were employed to model the head of the Mobetron, the layer, the applicator, and to calculate the dose distributions.Results:The applicator has two components. The upper component is a 3cm-diametre cylindrical collimator with 0.5cm wall made of 0.3cm steel and 0.2cm water equivalent material (WEM), a 0.13cm-foil made of tansgen. The lower component is a 4cm-diametre drum made of 0.2cm WEM and a 0.14cm maximum thickness hill-shaped modulator made of steel. When the energy of electron beam was 12MeV, the dose rate was about 90.44 cGy/min, and the depth of the 50% isodose curve was 1cm.Conclusion:The applicator is successfully designed, and can obtain a drum-shaped dose distribution.
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Objective To investigate the short?term complications and cosmetic outcomes of radiotherapy in breast conserving surgery for early?stage breast cancer. Methods A retrospective analysis was performed on clinical data from 30 patients with early?stage breast cancer from 2013 to 2015. All patients underwent breast conserving surgery combined with intraoperative low?energy X?ray radiotherapy. The prescribed dose was 20 Gy at the surface of the applicator. Local complications, radiation injury, and cosmetic outcomes were observed after surgery. Results No grade 3?4 adverse reactions were found in patients. In terms of short?term complications, four patients (13%) had seroma, two of whom needed suction treatment;three patients ( 10%) had grade 1?2 skin erythema. Half of the patients had excellent cosmetic outcomes. None of the patients had local recurrence or distant metastasis. Conclusions Intraoperative low?energy X?ray radiotherapy is safe and feasible in breast conserving surgery for breast cancer. It can be considered as an optional approach for tumor bed boost in some patients with early?stage low?risk breast cancer.