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Application of double scattering method using a dual-ring to formation of irradiation field for proton cancer therapy

双环双散射法在质子癌治疗照射场形成中的应用

基本信息

批准号：
09670915
负责人：
TAKADA Yoshihisa
金额：
$ 1.54万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09670915/
关键词：
Cancer therapy Proton therapy Double scattering Dual-ring Beam delivery Radiotherapy range-shifter range modulator リッジフィルター

项目摘要

A method of applying the efficient double scattering method using a dual-ring 2nd scatterer to proton cancer therapy has been clarified. Since insertion of beam modifying devices such as a range shifter and a range modulator (a bar ridge filter) modifies the lateral dose distribution, it is impossible to cover the whole depth range used for cancer treatment by a single scatterer combination. It is shown that we can obtain the uniform lateral dose distribution for the whole depth region if the covered depth of irradiation is divided into eight ranges and for each range, the appropriate combination of the first and the second scatterers are used.The method of applying the method to beam with relatively large emittance has been clarified. The six parameters specifying the lateral dose distribution are approximately optimized by changing three free parameters so that those six parameters are near to those which are optimum solution of the zero-emittance case. It is also shown that the dose distribution is rather sensitive to the selection of beam phase space parameters even if the emittance is the same. Namely focused, or diverging, or converging beams will produce different dose distributions.Since the method is sensitive to the beam misalignment, it is necessary to monitor the flatness of the distribution. For that purpose, we manufactured an ionization chamber with four identical collection electrodes placed at four quadrants of a single plane, each of them was electrically isolated from others. We tested the monitor chamber for the pulsed proton beam (5Onsec FWHM) and found that it can be used to monitor the inhomogeneity of less than 1 %.By the research, we clarified that this method can be used for proton cancer therapy effectively.

阐明了一种利用双环二阶散射体的高效双散射方法用于质子治癌的方法。由于插入射束修改装置（诸如范围移位器和范围调制器（条形脊滤波器））修改了横向剂量分布，因此不可能通过单个散射体组合覆盖用于癌症治疗的整个深度范围。研究表明，将照射覆盖深度分为八个范围，并对每个范围采用适当的第一和第二散射体组合，可以获得整个深度区域均匀的横向剂量分布，并阐明了将该方法应用于发射度较大的束流的方法。通过改变三个自由参数，使这六个参数接近于零发射度情况下的最优解，从而近似优化了指定横向剂量分布的六个参数。它还表明，剂量分布是相当敏感的束流相空间参数的选择，即使发射度是相同的。即聚焦、发散或会聚的射束会产生不同的剂量分布，由于该方法对射束失准很敏感，因此需要监测分布的平坦性。为此，我们制造了一个电离室，其中四个相同的收集电极放置在一个平面的四个象限，每个电极都与其他电极电隔离。通过对脉冲质子束（50nsec FWHM）的监测室的测试，发现该监测室可以监测到小于1%的非均匀性，说明该方法可以有效地用于质子治癌。