Enhanced radiobiological effects at the distal end of a clinical proton beam: in vitro study

• DOI: 10.1093/jrr/rrt230
• Publication Date: 2014-05-14T03:24:05Z
• Authors: Yoshitaka Matsumoto; Taeko Matsuura; Mami Wada; Yusuke Egashira; Teiji Nishio; Yoshiya Furusawa
• Keywords: Sobp; Relative biological effectiveness; Pencil-beam scanning

In the clinic, relative biological effectiveness (RBE) value of 1.1 has usually been used in relation to whole depth spread-out Bragg-peak (SOBP) proton beams. The aim this study was confirm actual effect SOBP at very distal end clinical beams using an vitro cell system. A human salivary gland tumor line, HSG, irradiated with (accelerated by 190 MeV/u) and examined different depths part center SOBP. Surviving fractions were analyzed colony formation assay. Cell survival curves parameters obtained fitting linear–quadratic (LQ) model. RBE each compared that for X-rays calculated equivalent dose, dose distribution from absorbed position. Although physical flat SOBP, values significantly higher (up 1.56 times) than Additionally, range isoeffective extended beyond 4.1 mm). From a point view, may cause unexpected side effects normal tissues position beam. It is important beam design treatment planning take into consideration distribution.