高能光子放疗的PET剂量验证研究

发布时间：2018-04-27 05:36

本文选题：高能光子 + 剂量验证　；参考：《苏州大学》2013年硕士论文

【摘要】：精确放疗是现代肿瘤放射治疗的发展趋势，是提高肿瘤放疗治愈率与减少放疗副作用或并发症的关键技术。而照射剂量的精确验证是制定精确放疗计划、提高放疗增益比及实施精确放疗的重要环节。目前基于透射剂量分布的验证方法尚不成熟，且无法实现三维实时剂量验证。随着新一代医用跑道式电子回旋加速器MM50的出现，以及PET在重离子加速器治疗过程的应用，使得利用PET成像技术开展剂量实时验证成为可能。项目利用MM50电子回旋加速器和PET装置开展了高能光子放射治疗的三维剂量验证实验，并模拟计算了高能扫描光子束的性能和剂量分布，系统地研究了高能光子在模体材料中产生正电子核素的光核反应产额、正电子核素活度分布与剂量分布，分析讨论了利用正电子核素断层成像开展剂量验证验证的临床可行性。论文根据新一代跑道式电子回旋加速器MM50的机头构造和射束特点，利用Monte Carlo程序模块建立MM50加速器机头结构模型，通过模拟计算和水箱测量，，分析了不同类型射野的射束特征和剂量分布。结果表明MM50高能扫描射线均整性和对称性良好，均在5%以内，半影为8mm，模拟和测量结果相符。根据高能光子产生~(11)C和~(15)O正电子核素的光核反应相关理论及光中子反应的反应截面数据，制作了水凝胶、聚乙烯和不均匀模体等三种实验模体。利用TPS及模拟软件计算了MM50加速器的高能X射线束在不同模体中的剂量分布。在25MV和50MV两种X线能量条件下开展剂量的PET三维剂量验证实验，利用MM50所产生的X射线分别照射三种模体并即时进行PET扫描，通过对比模体中正电子活度分布及剂量分布研究PET剂量验证的可行性。实验结果表明，对于高能光子放疗，50MV X线照射2Gy产生的正电子活度可达MBq数量级，可实现PET清晰成像；50MV X线产生的~(11)C和~(15)O正电子数量分别为25MV的3.86和3.88倍；三种模体中正电子三维分布和剂量分布相似。另外对小动物和病例开展了实验，并与模体进行了对比分析，结果表明高能光子放疗的PET剂量验证是准确可行的。
[Abstract]:Accurate radiotherapy is the development trend of modern tumor radiotherapy. It is the key technology to improve the cure rate and reduce the side effects or complications of radiotherapy. The accurate verification of radiation dose is an important step in making accurate radiotherapy plan, improving the gain ratio of radiotherapy and carrying out accurate radiotherapy. At present, the verification method based on transmission dose distribution is not mature, and can not realize 3D real-time dose verification. With the emergence of a new generation of medical racetrack electron cyclotron (MM50) and the application of PET in the treatment process of heavy ion accelerator, it is possible to use PET imaging technology to carry out real-time dose verification. The three dimensional dose verification experiment of high energy photon radiation therapy was carried out by using MM50 electron cyclotron and PET device, and the performance and dose distribution of high energy scanning photon beam were simulated and calculated. The photoreaction yield, activity distribution and dose distribution of positron nuclides produced by high-energy photons in motifs are systematically studied. The feasibility of dose verification using positron radionuclide tomography is analyzed and discussed. According to the configuration and beam characteristics of the new generation racetrack electron cyclotron (MM50), the model of the MM50 accelerator's head structure is established by using the Monte Carlo program module. The model is simulated and measured by water tank. The beam characteristics and dose distribution of different types of field are analyzed. The results show that the uniformity and symmetry of MM50 high energy scanning rays are all within 5% and the penumbra is 8 mm. The simulation results are in good agreement with the measured results. According to the theory of photonuclear reaction and the cross section data of photoneutron reaction, three experimental motifs, hydrogel, polyethylene and inhomogeneous motifs, have been prepared according to the theory of photo-nuclear reaction of high-energy photonic radionuclides (11 ~ (11) C) and ~ (15) O ~ (15) O positron nuclides. The dose distribution of high energy X-ray beam of MM50 accelerator in different motifs was calculated by TPS and simulation software. Three dimensional dose verification experiments of PET were carried out under the condition of 25MV and 50MV X-ray energy. The three kinds of motifs were irradiated by X ray produced by MM50 and PET scanning was carried out immediately. The feasibility of PET dose verification was studied by comparing positron activity distribution and dose distribution in motifs. The experimental results show that the positron activity of 2Gy irradiated by 50MV X-ray of high energy photon radiation can reach the order of MBq, and the positron number produced by 50 MV X-ray of PET imaging can be 3.86 times and 3.88 times of that of 25MV, respectively. The three-dimensional distribution and dose distribution of positron in the three kinds of motifs are similar. In addition, experiments were carried out on small animals and cases, and the results were compared with those of motifs. The results show that the PET dose verification of high energy photon radiation is accurate and feasible.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：R730.55

【参考文献】