碳离子放射治疗靶区PET-CT剂量验证的SUV值范围研究

发布时间：2018-06-02 13:35

本文选题：碳离子 + 放射治疗　；参考：《清华大学》2016年硕士论文

【摘要】：精确放射治疗是现代肿瘤放射治疗学的发展趋势,也是减少治疗并发症以及副作用和提高肿瘤放疗治愈率的先进技术。其中剂量验证这一环节对放疗计划制定和治疗实施的精确性以及提高治疗增益比起着十分重要的作用。但是目前对靶区三维剂量分布的实时验证很难通过基于采集透射剂量分布的这一常用方法来实现。随着PET-CT成像技术与质子重离子放疗技术的不断发展结合,使得采用这项技术进行粒子放疗实时剂量验证成为可能。可以利用高能碳离子轰击物质组织后在剂量沉积位置会产生一定数量正电子并与物质内负电子湮灭释放出伽马光子的特性,采用碳离子放疗计划CT图像与实际照射后采集的靶区位置PET-CT图像进行融合配准,在照射后靶区体积内活性元素衰变时间相对固定的情况下以不同靶区体积和不同单次靶区照射剂量分别测量对应PET-CT图像中相应位置靶区体积的SUV值,找出该体积相应SUV值的范围,为临床治疗中采用PET-CT图像准确验证评价治疗计划靶区剂量与实际照射靶区剂量的相关性和一致性提供参考和帮助。本研究选用仿真头部体模为研究对象,经模拟CT扫描生成计划图像后,在粒子治疗计划系统中勾画体积分别为10cc、4cc以及1cc的三组规则立方体,以模拟颅内脊索瘤患者临床靶区,采用粒子放疗系统以固定90度单射野对三组虚拟靶区分别进行高能碳离子照射,单次相对平均等效剂量分别给予2.5Gy、5Gy和8Gy,模拟常规分割和大分割剂量放射治疗。照射后即时应用正电子发射计算机断层成像系统对模体进行扫描,采用MIM医学图像处理软件对治疗计划CT图像与实际照射后的PET-CT图像进行刚性配准融合,通过计划CT图像中虚拟靶区体积位置确定相应PET-CT图像中该范围内SUV最大、最小、中位以及平均值等一系列数据,并分析不同靶区体积和不同照射剂量条件下各次PET-CT图像中SUV数据组的规律和异同。结果显示对于相同体积靶区,相应SUV值与照射剂量大小存在一定线性相关性;而对于不同体积靶区,在照射剂量完全相同的情况下,对应SUV值大小范围均保持一致,无显著性差异。所以针对模拟人体头部颅内靶区碳离子治疗计划,应用照射后一定时间内扫描得出的PET-CT图像与计划CT图像进行融合配准,通过分析靶区体积SUV值来评价验证靶区剂量沉积准确性的这一方法是可行的。对于碳离子照射后不同衰变时间下靶区体积剂量大小与SUV值范围的对应关系,也可以进一步采用类似方法进行探索和研究。
[Abstract]:Accurate radiotherapy is the development trend of modern tumor radiotherapy. It is also an advanced technology to reduce the complications and side effects and improve the cure rate of tumor radiotherapy. It is important to verify the accuracy of radiotherapy planning and treatment implementation and to improve the therapeutic gain. But at present, the real-time verification of the 3D dose distribution in target area is difficult to be realized by this common method based on the acquisition transmission dose distribution. With the development of PET-CT imaging technology and proton heavy ion radiotherapy technology, it is possible to use this technology to verify the dose of particle radiotherapy in real time. It is possible to produce a certain number of positron at the position of dose deposition by bombarding the tissue with high energy carbon ions and release gamma photons by annihilation with negative electrons in the matter. The PET-CT images of the target area were fused with the CT images of the plan of carbon ion radiotherapy and the actual irradiated images, and the fusion registration was carried out. Under the condition that the decay time of active elements in the target volume is relatively fixed after irradiation, the SUV values of the target volume corresponding to the corresponding position in the PET-CT image are measured with different target volume and different single target irradiation dose. To find out the range of the corresponding SUV value of the volume, and to provide reference and help for the accurate verification and evaluation of the correlation and consistency between the planned target dose and the actual irradiation target dose in clinical treatment by using PET-CT images. In this study, the simulated head phantom was selected as the research object. After simulated CT scanning, three sets of regular cubes with volumes of 10 ccD 4cc and 1cc were drawn in the particle therapy planning system to simulate the clinical target area of the patients with intracranial chordoma. The three groups of virtual targets were irradiated with high energy carbon ion with a fixed 90 degree single field with particle radiotherapy system. The relative average equivalent dose was given to 2.5 Gy 5Gy and 8 Gy, respectively. The conventional fractionation and large fraction dose radiotherapy were simulated. Positron emission computed tomography system was used to scan the motifs immediately after irradiation, and MIM medical image processing software was used to perform rigid registration fusion between CT images of therapeutic plan and PET-CT images after actual irradiation. By planning the volume position of virtual target area in CT images, a series of data such as maximum, minimum, median and average value of SUV in the corresponding PET-CT images are determined. The regularity and difference of SUV data group in each PET-CT image under different target volume and different irradiation dose were analyzed. The results showed that there was a linear correlation between the corresponding SUV value and the irradiation dose for the same volume target region, but for the different volume target region, the range of the corresponding SUV value remained the same when the irradiation dose was the same. There was no significant difference. Therefore, aiming at the carbon ion therapy plan of simulated human head intracranial target area, the PET-CT image obtained by scanning within a certain time after irradiation is fused with the planned CT image. It is feasible to evaluate the accuracy of target dose deposition by analyzing the SUV value of target volume. The relationship between the volume dose of target area and the range of SUV value under different decay time after carbon ion irradiation can also be further explored and studied by similar methods.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP391.41;R730.55

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