质子治疗的物理与生物学基础  

Physical and radiobiological properties of proton beams for therapy

作　　者：马秋峰[1] 李文建[1] 魏怀鹏[2] 

机构地区：[1]中国科学院近代物理研究所,甘肃兰州730000 [2]河北工业大学物理系,天津300130

出　　处：《基础医学与临床》2005年第2期102-111,共10页Basic and Clinical Medicine

基　　金：国家自然科学基金重点项目 (10 335 0 5 0 )

摘　　要：近几十年来质子治疗在临床上取得了巨大成就,这是因为质子束在物理学和生物学上具有独特的优势。在肿瘤治疗学上质子比常规射线(60 Co、X射线、电子)有两个主要优势:(1)可根据肿瘤在体内的深度,使质子束精确地定位在肿瘤病灶处,以使肿瘤受到最大的照射剂量而不伤害健康组织,从而达到适形治疗。(2 )可根据肿瘤的形状改变质子在微观尺度能量沉积的形状,实现辐射生物学效应的改变。基于此,对于形状较复杂的大实体瘤,质子治疗比常规治疗有更高的精度。质子的这些在治疗学上特异的可能性是由其剂量学和辐射生物学特性决定的。剂量学的性质与能量在宏观尺度的沉积特征有关,作为带电粒子,质子在介质中有确定的射程和相对小的散射歧离,此外在射程前端剂量相对较小,而到射程末端剂量达到最大,形成一个尖锐的Bragg峰,基于这些特点使得肿瘤受到高剂量的照射而周围的健康组织受到很小的伤害;相对生物学效应与能量在微观尺度的沉积特征有关,与重离子相比虽然质子属于低LET射线,但就其能量在微观尺度沉积的性质与常规射线相比质子是致密电离辐射,因此目前已有实验证实质子治疗比常规射线治疗增加了相对生物学效应,然而目前对能量的微观沉积与生物学效应关系的原理仍需要进一步从理论上和实验上研究证明。文中分析了质?The therapeutical advantages of proton beams as compared with photon and electron beams come from: (1)the possibility of focusing to the tumor in a physically selective way at the macroscopic scale ('conformal therapy') and so to reduce the dose burden to the surrounding healthy tissues.(2)the possibility of varying the radiobiological effects of the radiation by influencing the pattern of the energy deposition at the microscopic scale. For this reason proton is expected to produce superior results in the treatment of large tumors of complex shape.These novel therapeutical possibilities follow from the different dosimetric and radiobiological properties of proton beams with respect to conventional therapy.The dosimetric properties are related to the energy deposition at the macroscopic scale. As charged particles, protons have a well-defined range of penetration in materials and the relatively low scattering which allow a well defined dose distribution. Moreover the pronounced dose maximum in the region where the beam stops ensures that a great part of the dose is delivered in depth. Due to these facts the tumor can be irradiated with high doses while sparing the surrounding normal tissues. The possibility of varying the radiobiological properties is due to the fact that the biological effects are correlated with the microscopic distribution of the energy deposited and that this distribution is influenced by the energy and atomic number of the impinging protons. For this reason one often speaks of proton as 'densely ionizing' radiation in contrast to the 'sparsely ionizing' radiation such as X-and γ-rays. By now, the correlation between LET and RBE is so much studied but not clear. The development of a comprehensive theory of radiation action needs further studies both on the experimental and on the theoretical side. The physics process of proton in medium and some general concepts of medical radiation physics (such as LET, RBE and OER), are introduced in this paper. Based on these facts the physical and radiob

关 键 词：肿瘤 质子治疗 辐射生物学效应 剂量学 改变 伤害 健康 辐射生物学 LET 末端 

分 类 号：R730.55[医药卫生—肿瘤] R816.7[医药卫生—临床医学]