Development of Monte Carlo techniques for radiation transport simulations and application to radiotherapy physics and dosimetry

在北美，每年有60多万癌症患者接受放射治疗。每种治疗的一个关键方面是准确地向肿瘤提供已知剂量的辐射。因此，临床剂量学，即确定照射到肿瘤和患者其他部位的辐射剂量，在这些治疗中起着核心作用。本研究项目涉及临床剂量学的两个独立组成部分。其中一个目标是提高我们测量水箱辐射剂量的准确度，因为这可以校准可能是加速器或小放射性种子的辐射源的输出。另一个目标是提高我们获取“参考剂量”知识的能力，并计算暴露在同一辐射源下的真实患者体内的剂量分布。本研究项目中使用的核心工具是一套由首席研究员及其同事开发的计算机代码。这些代码使用所谓的蒙特卡罗技术来模拟辐射穿过物质的过程，包括测量设备和病人。这项研究是由CFI资助的一个强大的计算机集群支持的。这些计算机代码用于研究测量辐射的仪器是如何工作的，最近的突破意味着可以第一次计算出实际和准确的校正，从而改善临床辐射测量。结果显示，目前的方法在1%到5%的水平上存在问题，但由于这些错误可能影响数十万患者，因此效果可能很重要。在该研究项目的另一个组成部分，将利用另一项突破性技术，快速计算放置在体内杀死肿瘤的放射源周围的剂量分布。人们已经开发出精密的技术，对所使用的非常复杂的源进行精确的计算，而计算所需的时间已从几天缩短到几分钟。现在的目标是使程序更容易使用，以便临床物理学家可以在常规基础上使用它们，从而改善癌症放疗。

Over 600,000 cancer patients a year are treated by radiation in North America. A critical aspect of each treatment is the accurate delivery of a known dose of radiation to the tumour. Thus clinical dosimetry, the determination of the radiation dose delivered to the tumour and elsewhere in the patient, plays a central role in these treatments. This research program involves two separate components of clinical dosimetry. One goal is to improve our ability to measure the radiation dose in a water tank with a high degree of accuracy since this calibrates the output of the source of radiation which may be an accelerator or a small radioactive seed. Another goal is to improve our ability to take a knowledge of that "reference dose", and calculate the dose distribution inside a real patient exposed to the same source of radiation. The central tool used in this research program is a suite of computer codes developed by the principal investigator and colleagues. These codes use what are called Monte Carlo techniques to model the passage of radiation through matter, including measuring devices and patients. This research is supported by a powerful cluster of computers funded by CFI. These computer codes are used to study how the instruments which measure radiation are working and recent breakthroughs mean practical and accurate corrections can be calculated for the first time, thereby improving clinical radiation measurement. The results show problems with current methods at the 1 to 5% level, but since the errors can affect hundreds of thousands of patients, the effects can be important. In another component of the research program, use will be made of another breakthrough to rapidly calculate the dose distributions around radioactive sources placed in the body to kill tumours. Sophisticated techniques have been developed to do accurate calculations of the very complex sources used, while the time taken for the calculations has been reduced from days to minutes. The goal now is to make the programs easier to use so that clinical physicists can make use of them on a routine basis and thereby improve cancer radiotherapy.