基于锥形线束CT图像剂量计算准确度的实际测量验证研究  

Actual measurement verification of dose calculation accuracy based on cone-beam CT images

作　　者：陈黎 周钢[1] 孙彦泽[1] 彭啟亮 韩杰冠 田野[1] Chen Li;Zhou Gang;Sun Yanze;Peng Qiliang;Han Jieguan;Tian Ye(Department of Radiotherapy Oncology,the Second Affiliated Hospital of Soochow University,Institute of Radiotherapy Oncology,Soochow University,Suzhou Key Laboratory for Radiation Oncology,Suzhou 215004,China)

机构地区：[1]苏州大学附属第二医院放疗科,苏州大学放射肿瘤学研究所,苏州市肿瘤放射治疗重点实验室,苏州215004

出　　处：《中华放射肿瘤学杂志》2023年第6期539-545,共7页Chinese Journal of Radiation Oncology

基　　金：国家自然科学基金(82003219);苏州市放射治疗学临床医学中心项目(Szlcyxzx202103)。

摘　　要：目的采用实际测量的方法探讨CBCT图像用于剂量计算的准确度。方法回顾性分析苏州大学附属第二医院自2021年9月至2022年5月60位患者的锥形线束CT(CBCT)图像。利用Varian OBI系统获取模体的头部全扇面、头部半扇面、胸部半扇面、盆腔半扇面4种扫描模式的CBCT图像, 以CIRS电子密度模体建立对应扫描条件的CT值-电子密度(HU-ED)曲线, 在CBCT图像上设计放疗计划并对检测点的剂量计算结果与电离室测量结果进行比较, 分析剂量误差。然后利用三维剂量验证系统对60名患者基于CBCT图像放疗计划实施过程的准确度进行检测, 根据靶区D99%、Dmean、D1%和危及器官Dmean、D1%, 以及γ通过率来验证剂量计算的准确性。结果在模体点剂量检测中, 上述4种扫描模式CBCT图像的剂量计算误差分别为-1.06%±0.87%、-1.67%±0.86%、0.91%±0.73%、-1.54%±0.90%。患者基于CBCT图像治疗计划剂量学验证中, 各扫描模式下靶区(PTV)的Dmean、D99%及D1%差异均值均不超过2%, 除头部患者的晶状体外, 其他危及器官的Dmean和D1%差异不超过3%。各计划的靶区PTV及危及器官平均γ值在3%/2 mm标准下均<0.5。结论在正确建立HU-ED曲线的条件下, 基于CBCT图像的调强放射治疗(IMRT)/容积弧形调强放射治疗(VMAT)计划, 可用于适应性放射治疗(ART)中对靶区和危及器官实际受照剂量的估算与安全监控。对于头部患者, 采用全扇面扫描模式来获取图像能进一步提高剂量计算的准确度。Objective To evaluate the dose calculation accuracy of cone-beam CT(CBCT)image by actual measurement method.Methods CBCT images of 60 patients in the Second Affiliated Hospital of Soochow University from September,2021 to May,2022 were retrospectively analyzed.CBCT images of full-fan and half-fan scanning of the head,half-fan scanning of the chest and pelvis were obtained by the Varian OBI system.Hounsfield unit-electron density(HU-ED)curves corresponding to the scanning conditions were established with CIRS electron density phantom.The radiotherapy plans were designed on the CBCT images,and the dose calculation results of the detection point were compared with the ionization chamber measurement results to analyze the dose error.Then,three-dimensional dose verification system was adopted to detect the accuracy of the CBCT image radiotherapy plans implementation process in 60 patients,and the accuracy of dose calculation was verified according to the D99%,Dmean,D1%of target volume,Dmean and D1%of organs at risk(OAR),and theγpass rate.Results In point dose detection in phantom,the dose calculation errors of CBCT images in the above four scanning patterns were-1.06%±0.87%、-1.67%±0.86%,0.91%±0.73%,-1.54%±0.90%,respectively.In dosimetric verification based on patients'CBCT image treatment plan,the mean difference of Dmean,D99%,and D1%of planning target volume(PTV)in all scanning modes were not higher than 2%,and the Dmean and D1%differences of other OAR were not higher than 3%,except for the lens of patients in the head.The averageγvalues of target volume and OAR were less than 0.5 under the criteria of 3%/2 mm.Conclusions Under the condition of correctly establishing HU-ED curves,intensity-modulated radiation therapy(IMRT)/volumetric-modulated arc therapy(VMAT)planning based on CBCT images can be employed to estimate and monitor the actual dose to target volume and OAR in adaptive radiotherapy.Full-fan scanning patterns can further improve the accuracy of dose calculation for the head of patients.

关 键 词：锥形线束CT 剂量计算 准确度 实际测量 

分 类 号：R814.2[医药卫生—影像医学与核医学]