宫颈癌三维自适应腔内放疗的剂量学研究

发布时间：2018-04-14 21:02

本文选题：CBCT + 宫颈癌　；参考：《北京协和医学院》2014年博士论文

【摘要】：背景：腔内放疗(intracavitary brachytherapy, ICBT)是局部进展期宫颈癌根治性放疗的重要组成部分。传统的二维腔内放疗以正交X片为基础,通过参考点的剂量估计靶区和危及器官的剂量。三维腔内放疗则以MRI或CT等扫描技术为基础,可以充分了解靶区和危及器官的位置和空间形状,能更加精确地评估这些组织和结构的剂量,从而提高靶区剂量和降低危及器官剂量,以获得更加理想的局部控制率并降低并发症的发生率。CT是三维腔内放疗常用的影像学手段,依据CT图像能够进行高危临床靶区(high-risk clinical target volume, HR CTV)和危及器官(organs at risk, OARs)的勾画并制定计划和实现剂量优化过程。相比于二维腔内放疗,这一过程耗时明显延长,通常需要数小时时间。在这一时间内存在着HR CTV和OARs空间位置和形态变化,因此依据CT图像所制定的治疗计划并不能真实地反映剂量传递过程中HR CTV和危及器官的实际受照剂量,二者之间存在一定程度的差异。研究这一分次内剂量学差异的大小和可能导致的结果可以对临床实践提供有意义的指导。材料和方法：本研究纳入2013年12月至2014年6月之间9位在北京协和医院放疗科进行根治性放疗的宫颈癌病人进行CT引导下的腔内放疗,分割次数为5次,单次分割处方剂量为6Gy。在完成施源器放置后进行CT扫描,并以此图像勾画HRCTV和危及器官,随后制定计划并完成剂量优化。在开始治疗之前数分钟内完成锥形束CT(cone beam computed tomography, CBCT)扫描,在CBCT图像上重新勾画HRCTV和危及器官,将实际治疗所依据的CT计划中放射性源的驻留位置和驻留时间模拟至CBCT图像。对这9位病人完成了38次高剂量率(high-dose-rate, HDR)三维腔内放疗,一共获取了76个图像系列,包括38个CT图像系列和38个CBCT图像系列。运用统计学方法比较着两种图像系列下HR CTV和OARs相关DVH(dose-volume histogram,剂量体积直方图)参数变化,并分析这种剂量变化对整个腔内治疗带来的影响。结果：在平均间隔时间为55±10min的情况下,HR CTV的体积、D90、D50和V100在两组图像系列中变化(平均值士标准差)分别为-2.00±3.26%、-1.18±4.47%、-0.02±4.51%、-3.83±8.23%和-9.0±2.77%,其中HR CTV的体积和D100发生了显著统计学减小(p值分别为0.000和0.006)。各个危及器官包括膀胱、直肠、乙状结肠和小肠的D2cc变化分别为-0.6±17.05%、9.34±14.59%、7.15%±20.49%和1.52±12.57%,直肠D2cc发生了显著统计学增加(p=0.001)。结论：平均不到1小时的时间间隔内,单次分割内HR CTV的剂量学变化很小,D90的不确定性水平(1个标准差)约为5%,大约70%的单次治疗内HR CTV D90(EQD2)变化不超过±0.5Gy。但对某一次的治疗而言这一变化可以到达1.5Gy。这种单次分割内的剂量不确定水平在6Gy×5f的HDR分割模式下,可使某一病人的实际总EQD2最大减少3Gy。危及器官的剂量变化更加明显,大部分危及器官的D2cc变化无统计学差异,其系统性变化(平均值)10%,而随机变化(标准差)可达到15～20%水平。大部分治疗中至少有1个危及器官的剂量变化超过10%,可能会引起某一次治疗的剂量超过单次限量或者使其在整个治疗中(含外照射)的受照剂量超过累计限量。通过方法上的改进可能会减少这种不确定性并降低临床并发症的风险。
[Abstract]:Background: intracavitary radiotherapy (intracavitary brachytherapy ICBT) is an important part of radical radiotherapy for locally advanced cervical carcinoma. The traditional two-dimensional intracavitary radiotherapy based on orthogonal X, through reference point dose estimation of the target area and oar dose. Radiotherapy with intracavitary three-dimensional scanning technology based MRI or CT etc. and we can fully understand the target and organs at the location and spatial shape, can be more accurate assessment of the organization and structure of the dose, so as to improve target dose and reduce the doses to the organs at risk, to obtain the local control rate is more ideal and reduce the incidence of complications of.CT is commonly used means of 3D radiotherapy, on the basis of CT images can be high-risk clinical target (high-risk clinical target volume, HR CTV) and organs at risk (organs at risk, OARs) the outline and plan and achieve optimized dose . compared to the two-dimensional radiotherapy, the process takes significantly longer, usually takes a few hours. At this time in the memory of HR CTV and OARs spatial location and morphological changes, so the basis for the formulation of the CT image treatment plan can not reflect the actual dose in the transfer process of HR CTV and organs under actual dose, there is a difference between the two. This study dosimetric differences in two times the size and that the results can provide meaningful guidance for clinical practice.
Materials and methods: the study included between December 2013 and June 2014 9 in Peking Union Medical College Hospital Department of radiotherapy for cervical cancer patients with radical radiotherapy for brachytherapy guided by CT, division 5 times, a single partition, the prescription dose was 6Gy. CT scan in finish applicator after placement, and the images HRCTV and organs then, make a plan to do the optimal dose before beginning treatment. The number of minutes to complete the cone beam CT (cone beam computed tomography, CBCT) scan in the CBCT image to draw the outline of HRCTV and organs, the dwell time to simulate the actual treatment of radioactive source CBCT image will be based on the CT plan on. The 9 patients who completed the 38 high dose rate (high-dose-rate, HDR) 3D brachytherapy, a total of 76 series of image acquisition, including 38 CT and 38 CBCT image image series A statistical method is used to compare the changes in parameters of HR CTV and OARs related DVH (dose-volume histogram, dose volume histogram) under two kinds of image series, and analyze the effect of this dose change on the whole endovascular treatment.
Results: the average interval was 55 + 10min, HR CTV D90, D50 V100 and volume changes in the two groups of image series (mean + standard deviation) were -2.00 + 3.26%, -1.18 + 4.47%, -0.02 + 4.51%, -3.83 + 8.23% and -9.0 + 2.77%, the volume and D100 HR CTV had a significant decrease (P = 0 and 0.006). Various organs including bladder, rectum, sigmoid colon and small intestine D2cc changes were -0.6 + 17.05%, 9.34 + 14.59%, 7.15% + 20.49% and 1.52 + 12.57%, rectal D2cc had significant statistically increased (p=0.001).
Conclusion: the average less than 1 hours interval, single dose variation in HR CTV segmentation is very small, the level of uncertainty in D90 (1 standard deviation) is about 5%, about 70% of the single treatment of HR CTV D90 (EQD2) of less than 0.5Gy. but for a this change can reach 1.5Gy. this single dose in the segmentation uncertainty level segmentation in 6Gy * 5F HDR mode, can make a patient's actual total EQD2 maximum reduction of 3Gy. organs dose change is more obvious, there was no significant difference in most organs of D2cc changes, the system changes (average 10%), and random variation (standard deviation) can reach 15 to 20% levels. Most of the treatments in at least 1 oars dose changes more than 10%, may cause a dose more than a single limit or in the entire treatment (including external radiation exposure) The dose exceeds the cumulative limit. Improvement through methods may reduce this uncertainty and reduce the risk of clinical complications.

【学位授予单位】：北京协和医学院
【学位级别】：博士
【学位授予年份】：2014
【分类号】：R737.33

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