Measurement of ipsilateral lung and heart dose in radiotherapy of left sided mastectomy patients in common different clinical techniques: A phantom study

The aim of this study was to compare the radiation dose to ipsilateral lung and heart for different radiotherapy (RT) techniques including; two tangential photon beams, electron therapy and combined photon-electron. Treatment planning of the mentioned techniques on the CT images of a chest phantom was done using treatment planning system (TiGRT, Lina Tech, China). According to the plans, the phantom was irradiated with 6 MV photon and 10 MeV electron beams of Siemens Primus linac. Radiation dose was also measured using LiF Thermo Luminescence Dosimeter (TLD) which was placed inside 3 mm depth holes of ipsilateral lung and heart on the phantom. The mean (± SD) radiation dose to the ipsilateral lung of the combined photon-electron was 66.12 ± 5.16% of prescribed dose. Whereas for the heart, it was 64.05 ± 2.62%. Mean (± SD) dose of ipsilateral lung and heart for electron irradiation was 54.51 ± 3.88 % and 34.21 ± 3.41%, respectively. The mean (± SD) radiation dose to ipsilateral lung and heart of the tangential was 50.73 ± 3.01 % and 31.36 ± 3.13%, respectively. The mean (± SD) radiation dose to the chest wall-lung interface for electron therapy (72.44 ± 2.01 %) was significantly different in comparison with tangential (65.23± 4.20%; p = 0.045) and combined photon-electron (68.14± 3.53 %; p = 0.032). Tangential beams is more suitable for treating mastectomy patients compared to the other techniques such as electron therapy and combined photon-electron, due to lower radiation dose to patient's ipsilateral lung and heart.