Evaluation of Photoneutron by Hypofractionated Radiotherapy

Abstract

Hypofractionated radiotherapy prescribes high dose once. Due to this there's a bad point that patients are exposed much dose in normal organ. But recently the study making up for a limit is continuing. Cause of preference of this kind of development of therapy technic and high-energy photon beam, patients can be exposed to additional radiation. Because photoneutron is created by photonuclear reaction. So, in this study I measured photoneutron and analyzed by DVH amounts of radiation from the treatment plan that was used to acute, metastatic pelvis cancer patients who was treated by hypofractionated radiotherapy applied IMRT. As a result, incidence of photoneutron based on the hypofractionated radiotherapy was not a big difference in proportion to the dose fractionation. Protective effects of normal organ by hypofractionated radiotherapy applying IMRT is relatively high compared to 3D CRT but also photoneutron was in created. So a proper treatment plan and a best therapy should be considerated.■ keyword :|Hypofractionated radiotherapy|IMRT|Photonuclear reaction|Photoneutron|

Evaluation of Photon and Photoneutron Using High Energy X-ray in Radiation Therapy Room

“…[1] 또한 방사선 치료의 주를 이루는 선형가속기(Linear accelerator, LINAC)의 발달로 고 에 너지의 사용이 증가하였으며, 이로 인해 심부에 위치한 종양의 치료효율을 높이고 있다. [2] 하지만 고에너지의 광자는 주변 물질과 상호작용을 일으키며 광핵반응(Ph otoneuclear effect)으로 인한 광중성자(Photoneutron)를 발생시킨다. [3][4][5][6] 이렇게 생성된 광중성자는 환자 및 시 술자에게 2차적인 피폭을 야기 시키며, 광자에 비해 선 에너지부여(Linear energy transfer, LET) 및 생물학적 효과비(Relative biological effectiveness, RBE)가 상대적 으로 높아, 적은 선량으로도 인체의 위해도가 높다.…”