Hybrid pencil beam model based on photon characteristic line algorithm for lung radiotherapy in small fields
Cui Fengjie,
Gu Shaoxian,
Wang Ningyu,
Yin Chuou,
Zhang Shengyuan,
Hu Jinyou,
Cai Yunzhu,
Wu Zhangwen,
Gou Chengjun,
Wang Jun
Affiliations
Cui Fengjie
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Gu Shaoxian
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Wang Ningyu
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Yin Chuou
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Zhang Shengyuan
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Hu Jinyou
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Cai Yunzhu
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Wu Zhangwen
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Gou Chengjun
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Wang Jun
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
Hybrid pencil beam model (HPBM) based on photon characteristic line algorithm has been presented to get accurate three-dimensional (3D) dose distribution for lung radiotherapy in small fields. In the model, we introduced a scattering factor to accurately describe the transport behavior of scattered photons and secondary electrons, combined with the equivalent depth correction and the weighted density correction. The pencil beam kernels of heterogeneous lung phantoms were redefined by the scattering factor and depth dose for a reference field by photon characteristic line algorithm. Subsequently, the 3D dose distribution in lung phantoms with density of 0.1, 0.26, and 0.4 g/cm3, was calculated by the Finite-size pencil beam algorithm in five regular fields and an irregular field for 6 MV photon beam. The dose distributions obtained by the HPBM are in agreement with those obtained by the MC simulations, with a relative error of less than 3% in most of the cases. However, there are apparent discrepancies at media interfaces and lung anterior portion. Moreover, at media interfaces, relative dose errors of the two methods decrease with the increase in field size and lung density. The depth range in which relative errors is greater than 3% increases with the increase in field size at lung anterior portion. In these examples, maximum relative errors are between 5 and 29%. Nevertheless, it is shown that the HPBM based on photon characteristic line algorithm has potential research values in lung dose calculation under conditions of small fields.
