Luo Huanli, He Yanan, Jin Fu, Yang Dingyi, Liu Xianfeng, Ran Xueqi, Wang Ying
Department of Radiation Oncology, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Chongqing Cancer Hospital, Chongqing, 400030, China,
Cancer Manag Res. 2018 Sep 20;10:3679-3686. doi: 10.2147/CMAR.S174240. eCollection 2018.
Accurate delineation of targets and organs at risk (OAR) is required to ensure treatment efficacy and minimize risk of normal tissue toxicity with radiotherapy. Therefore, we evaluated the impacts of computed tomography (CT) slice thickness and reconstruction methods on the volume and dose evaluations of targets and OAR.
Eleven CT datasets from patients with thoracic cancer were included. 3D images with a slice thickness of 2 mm (2-CT) were created automatically. Images of other slice thickness (4-CT, 6-CT, 8-CT, 10-CT) were reconstructed manually by the selected 2D images using two methods; internal tumor information and external CT Reference markers. Structures and plans on 2-CT images, as a reference data, were copied to the reconstructed images.
The maximum error of volume was 84.6% for the smallest target in 10-CT, and the maximum error (≥20 cm) was 10.1%, 14.8% for the two reconstruction methods, internal tumor information and external CT Reference, respectively. Changes in conformity index for a target of <20 cm were 5.4% and 17.5% in 8-CT. Changes on V and V of the heart were considerable. In the internal tumor information method, volumes of hearts decreased by 3.2% in 6-CT, while V and V increased by 18.4% and 46.6%.
The image reconstruction method by internal tumor information was less affected by slice thickness than the image reconstruction method by external CT Reference markers. This study suggested that before positioning scanning, the largest section through the target should be determined and the optimal slice thickness should be estimated.
为确保放射治疗的疗效并将正常组织毒性风险降至最低，需要准确勾画靶区和危及器官（OAR）。因此，我们评估了计算机断层扫描（CT）层厚和重建方法对靶区和OAR体积及剂量评估的影响。
纳入11例胸段癌患者的CT数据集。自动创建层厚为2mm的三维图像（2-CT）。使用两种方法通过选定的二维图像手动重建其他层厚（4-CT、6-CT、8-CT、10-CT）的图像；内部肿瘤信息和外部CT参考标记。将2-CT图像上的结构和计划作为参考数据复制到重建图像上。
10-CT中最小靶区的体积最大误差为84.6%，两种重建方法（内部肿瘤信息和外部CT参考）中最大误差（≥20cm）分别为10.1%、14.8%。8-CT中＜20cm靶区的适形指数变化分别为5.4%和17.5%。心脏的V和V变化显著。在内部肿瘤信息方法中，6-CT中心脏体积减少3.2%，而V和V分别增加18.4%和46.6%。
与外部CT参考标记的图像重建方法相比，内部肿瘤信息的图像重建方法受层厚的影响较小。本研究表明，在定位扫描前应确定穿过靶区的最大层面并估计最佳层厚。
