Li Yu, Sun Wuji, Liu Shilong, Xia Wenming, Yang Xu, Wang Libo, Ge Chao, Chen Kunzhi, Shi Yinghua, Wang Huidong
Department of Radiation Oncology & Therapy, The First Hospital of Jilin University, Changchun, China.
Jilin Provincial Key Laboratory of Radiation Oncology & Therapy, Department of Radiation Oncology & Therapy, The First Hospital of Jilin University, Changchun, China.
Front Oncol. 2024 Sep 2;14:1392741. doi: 10.3389/fonc.2024.1392741. eCollection 2024.
The body contour of patients with cervical cancer is prone to change between radiotherapy sessions. This study aimed to investigate the effect of body contour changes on the setup and dosimetric accuracy of radiotherapy.
15 patients with cervical cancer after surgery were randomly selected for retrospective analysis. The body contours on the once-per-week cone-beam computed tomography (CBCT) were registered to the planning CT (pCT) for subsequent evaluation. A body contour conformity index (CI) was defined to quantify the variation of body changes. The body volume measured by CBCT was collected, and its relative difference in reference with the first CBCT was calculated and denoted by ΔV. The relative setup errors, denoted by ΔSE, ΔSE, ΔSE, and ΔSE for left-right, anterior-posterior, superior-inferior, and vectorial shifts, respectively, were defined as the difference in measured setup errors between the reference and following CBCTs. The planned dose was calculated on the basis of virtual CT generated from CBCT and pCT by altering the CT body contour to fit the body on CBCT without deformable registration. The correlations between body contour changes and relative setup errors as well as dosimetric parameters were evaluated using Spearman's correlation coefficient .
CI was found to be negatively correlated with the superior-inferior and vectorial relative setup errors ΔSE ( = -0.448, = 0.001) and ΔSE ( = -0.387, = 0.002), and no significant correlation was found between relative setup errors and ΔV. Moreover, ΔV was negatively correlated with ΔD ( = -0.829, < 0.001), ΔD ( = -0.797, < 0.001), and ΔTV ( = -0.819, < 0.001). ΔD, ΔD, and ΔTV were negatively correlated with ΔV ( < 0.005). No correlation was found for other examined dosimetric parameters.
The body contour change of patients could be associated with the setup variability. The effect of body contour changes on dose distribution is minimal. The extent of body change could be used as a metric for radiation therapists to estimate the setup errors.
宫颈癌患者的身体轮廓在放疗疗程之间容易发生变化。本研究旨在探讨身体轮廓变化对放疗摆位及剂量准确性的影响。
随机选取15例宫颈癌术后患者进行回顾性分析。将每周一次的锥形束计算机断层扫描（CBCT）上的身体轮廓与计划CT（pCT）进行配准，以便后续评估。定义身体轮廓一致性指数（CI）来量化身体变化的差异。收集CBCT测量的身体体积，并计算其相对于首次CBCT的相对差异，记为ΔV。左右、前后、上下和矢量位移的相对摆位误差分别记为ΔSE、ΔSE、ΔSE和ΔSE，定义为参考CBCT和后续CBCT之间测量的摆位误差差异。通过改变CT身体轮廓以拟合CBCT上的身体，在不进行可变形配准的情况下，根据从CBCT和pCT生成的虚拟CT计算计划剂量。使用Spearman相关系数评估身体轮廓变化与相对摆位误差以及剂量学参数之间的相关性。
发现CI与上下和矢量相对摆位误差ΔSE（ = -0.448， = 0.001）和ΔSE（ = -0.387， = 0.002）呈负相关，相对摆位误差与ΔV之间未发现显著相关性。此外，ΔV与ΔD（ = -0.829， < 0.001）、ΔD（ = -0.797， < 0.001）和ΔTV（ = -0.819， < 0.001）呈负相关。ΔD、ΔD和ΔTV与ΔV呈负相关（ < 0.005）。其他检查的剂量学参数未发现相关性。
患者的身体轮廓变化可能与摆位变异性有关。身体轮廓变化对剂量分布的影响最小。身体变化程度可作为放射治疗师估计摆位误差的指标。
