Bell Lauren, Holloway Lois, Bruheim Kjersti, Petrič Primož, Kirisits Christian, Tanderup Kari, Pötter Richard, Vinod Shalini, Lim Karen, Pogson Elise, Metcalfe Peter, Hellebust Taran Paulsen
Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia.
Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia; Liverpool & Macarthur Cancer Therapy Centres, Liverpool, Australia; Ingham Institute for Applied Medical Research, Liverpool, Australia; South Western Sydney Clinical School, University of New South Wales, Liverpool, Australia; Institute of Medical Physics, University of Sydney, Sydney, Australia.
Brachytherapy. 2020 Mar-Apr;19(2):146-153. doi: 10.1016/j.brachy.2020.01.002. Epub 2020 Feb 14.
To examine the variability in prescribed dose due to contouring variations in intracavitary image-guided adaptive brachytherapy for cervical cancer. To identify correlations between dosimetric outcomes and delineation uncertainty metrics.
A data set from an EMBRACE sub-study on contouring uncertainties was used, consisting of magnetic resonance images of six patients with cervical cancer delineated by 10 experienced observers (target volumes and organs at risk). Two gold standard contours were generated, an expert consensus and the simultaneous truth and performance level estimation. Plans were individually optimised to all of the contour sets (12 in total). Plans were applied to the gold standard contour sets, and dose volume histogram parameters including D, D and D were determined. The variability between plans was assessed. Dose volume histogram parameters and delineation uncertainty metrics were correlated using the Spearman's non-parametric rank correlation.
There is a dosimetric variability between observers, patients and the gold standard contour used for analysis. Approximately 3 Gy D EQD2 variability (SD) was observed for the CTVHR and 1.2-3.6 Gy D EQD2 for the organs at risk. The maximum geometric dimensions of the delineations are most commonly correlated with dosimetry changes. Although the correlations are similar across gold standards, the direction of these correlations differs, indicating that the dosimetric outcomes are dependent on the contour that the plan is optimised to.
This study highlights the dosimetric differences interobserver uncertainty in contouring can have for cervical cancer brachytherapy. The importance of carefully choosing a gold standard from which to benchmark is reiterated.
研究宫颈癌腔内图像引导自适应近距离放射治疗中由于轮廓勾画差异导致的处方剂量变异性。确定剂量学结果与勾画不确定性指标之间的相关性。
使用了来自EMBRACE关于轮廓勾画不确定性的子研究的数据集，该数据集由10名经验丰富的观察者勾画的6例宫颈癌患者的磁共振图像（靶区体积和危及器官）组成。生成了两个金标准轮廓，一个是专家共识轮廓，另一个是同步真相与性能水平估计轮廓。对所有轮廓集（共12个）分别进行计划优化。将计划应用于金标准轮廓集，并确定包括D、D和D在内的剂量体积直方图参数。评估计划之间的变异性。使用Spearman非参数秩相关分析剂量体积直方图参数与勾画不确定性指标之间的相关性。
观察者、患者以及用于分析的金标准轮廓之间存在剂量学变异性。CTVHR观察到约3 Gy D EQD2的变异性（标准差），危及器官为1.2 - 3.6 Gy D EQD2。勾画轮廓的最大几何尺寸最常与剂量学变化相关。尽管不同金标准下的相关性相似，但这些相关性的方向不同，表明剂量学结果取决于计划所优化的轮廓。
本研究强调了轮廓勾画中观察者间不确定性对宫颈癌近距离放射治疗剂量学差异的影响。重申了仔细选择用于基准的金标准的重要性。
