Radiation Quality and Relative Biological Effectiveness of Proton Beams

根据质子辐照生物材料的实验数据，对质子束的辐射质量和辐射效应的精确终点进行了关联，并对质子束在扩展布拉格峰(SOBP)处的线性能量传递(LET)进行了评估，这些因素包括初始能量、SOBP的宽度和辐照位置以及场整形装置。对于质子束的质量要求，初始能量应分为100 MeV以下、100-200 MeV和200 MeV以上三类，标准辐照位置建议在4-5 cm宽SOBP的中段。建议在这样的限制条件下开展质子束径向效应的对比研究。此外，对于标准辐射，如~(60)Co伽马射线或3~4MVX射线，生物效应的终点应确定，小动物的剂量学应在3%以内。对于这些谨慎的限制，质子束应用于深层肿瘤治疗的RBE值可以从1.0到1.2。

Correlation of a wide range of published data from proton irradiation experiments on several biological materials has been achieved in terms of the radiation quality of proton beam and the precice end point of radiation effects.Linear energy transfer (LET) of proton beams at the spread out bragg peak (SOBP) has been evaluated for several quality factors such as the initial energies, the width and irradiation position of SOBP and the field shaping devices. For the quality specification of proton beam, the initial energy should be categorized into three classes, below 100MeV, 100-200 Mev and above 200 MeV.The standard irradiation position is suggested to be the middle of 4-5cm width SOBP.The contamination of secondary radiations including neutrons should be estimated. Comparative study on RBE of proton beams is suggested to carry out under such limited conditions. In addition, the end point of biological effects should be definite and the dosimetry in small animal should be made within 3% for the standard radiations such as ^<60>Co gamma rays or 3-4 MVX rays. For these careful limitations, RBE value of proton beams applied to the deep seated tumor therapy is obtainable from 1.0 to 1.2.