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doi:10.11889/j.1000-3436.2015.rrj.33.030203

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- Journal of Radiation Research and Radiation Processing Vol. 33, Issue 3, Pages: 30203-030203(2015)
- 作者机构：
  
  1. 1（浙江大学医学院附属第二医院放疗科）,杭州,310009
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- DOI：10.11889/j.1000-3436.2015.rrj.33.030203
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[J]. Journal of Radiation Research and Radiation Processing 33(3):30203-030203(2015)
DOI：

[J]. Journal of Radiation Research and Radiation Processing 33(3):30203-030203(2015) DOI： 10.11889/j.1000-3436.2015.rrj.33.030203.

摘要

通过对定位CT和KV-CBCT制定的左侧乳腺癌根治术后调强计划的比较，探讨调强放疗过程中的靶区和危及器官的剂量学变化特点。选取18例左侧乳腺癌根治术患者，按照定位CT制定治疗计划(PCT)并执行治疗，同时获取第1、6、11、16和21次治疗时的KV-CBCT图像。复制一套定位CT图像和所有结构，再进行容积密度分配(BDA)和计划的复制，形成BDA计划(PBDA)，处方剂量50 Gy/25次/5周，90%的靶区达到处方剂量。将获取的5组KV-CBCT图像导入计划系统，并与定位CT进行图像配准、结构复制和BDA，分别制定5组KV-CBCT的移植计划(PREP)和5组全新KV-CBCT计划(PCBCT)。PREP的各项计划参数与PCT相同，但PCBCT是在KV-CBCT图像上完全重新制定的调强计划。每组PREP和PCBCT均给予5 Gy，90%的靶区达到处方剂量。5组PREP和PCBCT计划各自叠加合成为P∑REP和P∑CBCT，两种计划的总处方剂量均为50 Gy/25次/5周。根据剂量体积直方图(DVH)比较PCT、PBDA、P∑REP和P∑CBCT的剂量分布差异，计划间的剂量比较行配对t检验。结果显示，PBDA与PCT具有相似的靶区适形性和剂量均匀性(p>0.05)。P∑.05靶区的均匀性与适形性均显著差于PCT的相应值(t=−2.96、−3.57，p<0.05)。而P∑CBCT的适形性与均匀性则显著优于P∑形性与均(t=−4.01、−6.24，p<0.05)，但与PCT相比，并无显著差异(p>0.05)。与PCT相比，PBDA有相似的危及器官受量，计划间无显著差异(p>0.05)。P∑.05中的右侧乳腺Dmax、左侧肺V5、左侧肺V30、左侧肺Dmean和心脏V30均显著高于PCT的相应结构(t=−5.32、−3.57、−2.81、−2.99、−4.06，p<0.05)。与P∑.05相比，P∑CBCT中的所有危及器官受量均得到显著下降(t=4.65、3.88、5.32、3.16、4.95、2.79、4.55，p<0.05)。因此，在左侧乳腺癌改良根治术调强放疗过程中，由于受心肺运动等多因素影响，靶区和危及器官受量变化显著，需要通过KV-CBCT图像引导和BDA方法实时或自适应来调整治疗计划，以达到更高的治疗增益比。

Abstract

The aim is to investigate the dosimetric characteristics of planning target volume (PTV) and organs at risk (OAR) during the radiotherapy of left-sided breast cancer treated with modified radical mastectomy by comparing IMRT plans based on CT images and kilo-voltage cone beam computed tomography (KV-CBCT) images. 18 patients with left-sided breast cancer treated with radical mastectomy were selected. Treatment plans (PCT) based on CT images were designed and performed. KV-CBCT images were also acquired on the 1st day, 6th day, 11th day, 16th day, and 21st day of radiotherapy. All structures on planning CT images including PTV and OAR were applied by bulk density assignment (BDA) and plan parameters of PCT were replanted to a copy of planning CT images, which generated a new plan (PBDA). The prescription dose of PBDA was 50 Gy with conventional fractionation: 2 Gy per fraction, 5 fractions per week, total 25 fractions. The prescription dose was 50 Gy/25 F/5 week, 90% of the target area were covered by the prescription dose. The 5 series of KV-CBCT images acquired were imported into the planning system and matched with the planning CT for the same treatment position. The same structures of planning CT images were copied and applied by BDA on 5 series of KV-CBCT images. 5 replanted plans (PREP) and 5 new KV-CBCT plans (PCBCT) were designed based on these KV-CBCT images. Radiation parameters of PREP were same to those of PCT, but all parameters of PCBCT were new. 5 Gy given to each PREP and PCBCT covered 90% PTV. Two composite plans (P∑REP and P∑CBCT) were compounded of the five PREPs and five PCBCTs, respectively. Total prescription dose of P∑REP and P∑CBCT were 50 Gy/25 F/5 week. According to dose volume histograms (DVHs), dose distribution of PCT, PBDA, P∑REP and P∑CBCT were compared and analyzed by t-test. The results showed that PBDA has similar conform index (CI) and inhomogeneity coefficient (HI) to PCT(p>0.05). HI and CI of P∑REP were significantly worse than those of PCT(t=−2.96, −3.57, p<0.05). HI and CI of P∑CBCT were significantly better than those of P∑REP (t=−4.01, −6.24, p<0.05), but no significant difference with PCT(p>0.05). Comparing to PCT, PBDA gave similar dose indexes of OAR(p>0.05). Several parameters with P∑REP were significantly higher than with PCT: breast_R Dmax, lung_L V5, lung_L V30, lung_L Vmean and heart V30(t=−5.32, −3.57, −2.81, −2.99, −4.06, p<0.05). Compared with P∑REP, all OARs dose indexes of P∑CBCT were significantly decreased(t=4.65, 3.88, 5.32, 3.16, 4.95, 2.79, 4.55, p<0.05). In a conclusion, due to many factors such as the impact of cardiopulmonary exercise and significant dose changes of PTV and OARs, it is necessary that a real-time or adaptive treatment plan based on KV-CBCT images guided and BDA method should be designed to achieve the higher therapeutic gain ratio for IMRT radiotherapy of modified radical mastectomy for left-sided breast cancer.Cited

关键词

容积密度分配KV-CBCT改良根治术剂量学

Keywords

Bulk density assignmentKilo-voltage cone beam computed tomographyModified radical mastectomyDosimetry

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Cancer Clinical Medical Center, Radiation Oncology Center, the First People Hospital of Zunyi/ the Third Affiliated Hospital of Zunyi Medical University

Department of Radiotherapy, Gansu Provincial Hospital

Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University; Shanghai Key Laboratory of Radiation Oncology

Department of Radiotherapy, Gansu Provincial Cancer Hospital

Tianjin Key Laboratory of Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College

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DOI：10.11889/j.1000-3436.2015.rrj.33.030203

摘要

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关键词

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