BRAGG PEAK LOCALIZATION BY RADIOACTIVE BEAMS

重荷电粒子对癌症患者的布拉格峰治疗 需要精确定位肿瘤体积上的布拉格峰。一个 轻微的错误会导致肿瘤区域剂量严重不足，并 附近关键器官服药过量。 对于布拉格峰的精确定位，人们需要和实验 入口点之间水当量厚度的实测值 和目标音量。在这两个端点之间可能存在未知的 骨、组织、鼻窦、空气等的数量。 目前使用的CT技术可能不像预期的那样可靠，特别是 当有大量粗骨或气道时。我们有一个 使用高能放射性束流和灵敏正电子的技术 相机，我们预计，这将达到预期的精度。 在这项技术中，使用了19Ne或11C等放射性粒子。 这两个粒子都通过发射正电子而衰变，然后正电子湮灭。 中间的电子产生两条伽马射线，间隔180 学位。然后，这些伽马射线可以在符合模式下通过 用正电子相机在太空中定位它们的原点。 通过调节放射性粒子(主要是19Ne)的能量 将被使用)，它们将被停在肿瘤的位置， 可以通过正电子相机进行验证。这种方法提供了一种直接的测量方法 所需的水当量厚度。这项技术将被应用于 在治疗位置(在线)和就在实际治疗之前。 与X射线(用于CT)不同，放射性粒子具有穿透性 与重带电粒子性质非常相似的性质 用于布拉格峰疗法。水当量厚度的取值 由放射性束流测量，然后直接用于治疗 用重带电粒子进行计划。布拉格峰值剂量的精确传递 在肿瘤体积上，同时保留正常细胞和临界值 评价的机构、构成和极其重要的组成部分 重颗粒治疗模式。这是中国政府的长期目标。 实验室。

The Bragg peak therapy of cancer patients with heavy charged particles requires precise localization of the Bragg peak on a tumor volume. A slight error can cause severe underdosing of the tumor region and overdosing of the nearby critical organs. For precise localization of the Bragg peak, one requires and experimentally measured value of the water equivalent thickness between the point of entry and the target volume. Between these two end points there can be unknown amounts of bone, tissue, sinus, air etc. Presently used CT techniques may not be as reliable as desired, especially when there is a large amount of thick bone or air path. We have a technique which uses high energy radioactive beam and a sensitive positron camera, which, we expect, will achieve the desired accuracy. In this technique, radioactive particles such as 19Ne or 11C are used. Both of these particles decay by emitting positrons, which then annihilate with the medium electrons to produce two gamma rays, separated by 180 degrees. These gamma rays can then be detected in coincidence mode by a positron camera to locate their origin in space. Through adjustment of the energy of the radioactive particles (mostly 19Ne will be used), they will be stopped on the location of the tumor, verifiable by the positron camera. This method provides a direct measure of the required water equivalent thickness. This technique will be applied in the treatment position (on-line) and just before the actual therapy. Unlike X-rays (used in CT), radioactive particles have penetration properties that are very similar to those of the heavy charged particles used in Bragg peak therapy. the value of the water equivalent thickness measured by a radioactive beam is then directly applicable for treatment planning with heavy charged particles. Precise delivery of Bragg peak dose on a tumor volume, while sparing the normal cells and hearby critical organs, constitutes and extremely important component of the evaluation of heavy particle treatment modality. This is a long term goal of the laboratory.