Proton Dose Distribution and its Biological Effect Distribution

为了应用于剂量分布测量，用常规用于放射治疗的质子束研究了成像板(IP)的响应。IP系统可测量的质子剂量上限几乎受扫描仪读数范围的控制。在此限度内，IP对水中质子剂量的合理线性响应保持不变。衰变曲线对室温的微小变化或质子剂量的某种变化(0.0108-0.132 GY)不是很敏感。如果仔细考虑每个激电的衰落特性和灵敏度的批次相关性，则PSL强度的重现性相当好。在Bragg曲线的不同位置测量了激电响应的停止功率依赖关系。在PMRC中，质子束轴线和垂直于水模的线上的剂量分布具有…在与患者治疗相同的条件下，用扫描硅半导体探测器进行了更多的测量，目的是验证SOBP给出的高剂量区(一般为靶区中束轴上最大值的90%~95%)与计划治疗靶区的宽度一致。现在，我们测试了可在水中使用的二维剂量分布探测器，以代替现有的探测系统。为此，采用了一种由X射线照相增强屏和CCD摄像机组成的系统。垂直放置在水模中的屏幕设置为：1)小角度测量其闪烁光在深度上的光强分布；2)垂直测量给定深度的二维光强分布。在后一种情况下，将设置为与质子束方向成45度角的密勒连接到水模的远端边缘。在用硅半导体探测器测量剂量的基础上，研究了该屏的吸收剂量-光强转换效率特性。作为实验和分析结果，我们在海报上展示了屏幕产生的光强的LET依赖关系以及硅剂量计的剂量分布与屏幕的光强分布之间的关系。较少

For an application to the dose-distribution measurement, response of an imaging plate (IP) has been studied with proton beams, which are routinely utilized for the radiation therapy. The upper limit of measurable proton dose by an IP system is almost controlled by the readout range of scanner used. Within this limit, reasonable linear response of an IP to proton dose to water is maintained. Fading curves are neither so sensitive to a small change of room temperature nor to a certain variation of proton dose (0.0108-0.132 Gy). Reproducibility of the PSL intensity is fairly good if both the fading characteristics and the lot-dependence of the sensitivity of each IP are taken into account carefully. Stopping power dependence of IP response has been measured at different positions in a Bragg curve. Tolerance of IP to radiation damage by proton irradiation has been examined.In PMRC, dose distributions on the axis of proton beam and on the lines perpendicular to that in the water phantom hav … More e been measured by scanning Si semiconductor detector, under the same condition of a beam delivery system including bolus and patient collimator as that of patient treatment.The purpose of this measurement is to verify that the width of high dose region (90%-95% to maximum on beam axis in the target volume in general) given by SOBP beam is coincident to that of planned target region as a result of the treatment planning. Now, we test the two dimensional dose distribution detector usable in water in place of the present detection system. For this purpose, a system composed of intensifying screen used for X-ray radiography and CCD camera was used. The screen stood vertically in water phantom was set to the axis of proton beam as 1) at small angle to mainly measure intensity distributions of its scintillation light on depth and 2) perpendicularly to measure 2-D light intensity distribution at given depth. In latter case, a miller set at 45 degrees to the proton beam direction was attached to the distal edge of the water phantom. Characteristics of the screen about efficiency converting the absorbed dose to light intensity were investigated on the basis of dose measured by Si semiconductor detector. We show LET dependency of light intensity generated from the screen and relationships between dose distributions by silicon dosimeter and light intensity distributions by the screen as experimental and analytical results on a poster. Less