Henke Lauren E, Fischer-Valuck Benjamin W, Rudra Soumon, Wan Leping, Samson Pamela S, Srivastava Amar, Gabani Prashant, Roach Michael C, Zoberi Imran, Laugeman Eric, Mutic Sasa, Robinson Clifford G, Hugo Geoffrey D, Cai Bin, Kim Hyun
Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, United States.
Department of Radiation Oncology, Emory University, Atlanta, GA, United States.
Radiother Oncol. 2023 Jan;178:109428. doi: 10.1016/j.radonc.2022.11.017. Epub 2022 Nov 28.
A kV imager coupled to a novel, ring-gantry radiotherapy system offers improved on-board kV-cone-beam computed tomography (CBCT) acquisition time (17-40 seconds) and image quality, which may improve CT radiotherapy image-guidance and enable online adaptive radiotherapy. We evaluated whether inter-observer contour variability over various anatomic structures was non-inferior using a novel ring gantry kV-CBCT (RG-CBCT) imager as compared to diagnostic-quality simulation CT (simCT).
MATERIALS/METHODS: Seven patients undergoing radiotherapy were imaged with the RG-CBCT system at breath hold (BH) and/or free breathing (FB) for various disease sites on a prospective imaging study. Anatomy was independently contoured by seven radiation oncologists on: 1. SimCT 2. Standard C-arm kV-CBCT (CA-CBCT), and 3. Novel RG-CBCT at FB and BH. Inter-observer contour variability was evaluated by computing simultaneous truth and performance level estimation (STAPLE) consensus contours, then computing average symmetric surface distance (ASSD) and Dice similarity coefficient (DSC) between individual raters and consensus contours for comparison across image types.
Across 7 patients, 18 organs-at-risk (OARs) were evaluated on 27 image sets. Both BH and FB RG-CBCT were non-inferior to simCT for inter-observer delineation variability across all OARs and patients by ASSD analysis (p < 0.001), whereas CA-CBCT was not (p = 0.923). RG-CBCT (FB and BH) also remained non-inferior for abdomen and breast subsites compared to simCT on ASSD analysis (p < 0.025). On DSC comparison, neither RG-CBCT nor CA-CBCT were non-inferior to simCT for all sites (p > 0.025).
Inter-observer ability to delineate OARs using novel RG-CBCT images was non-inferior to simCT by the ASSD criterion but not DSC criterion.
与新型环形机架放射治疗系统耦合的千伏成像仪可改善机载千伏锥形束计算机断层扫描（CBCT）的采集时间（17 - 40秒）和图像质量，这可能会改善CT放射治疗图像引导并实现在线自适应放射治疗。我们评估了与诊断质量的模拟CT（simCT）相比，使用新型环形机架千伏CBCT（RG - CBCT）成像仪时，不同解剖结构上观察者间轮廓变异性是否不劣于前者。
材料/方法：在一项前瞻性成像研究中，对7例接受放射治疗的患者在屏气（BH）和/或自由呼吸（FB）状态下使用RG - CBCT系统对不同疾病部位进行成像。7名放射肿瘤学家分别在以下图像上对解剖结构进行轮廓勾画：1. SimCT；2. 标准C形臂千伏CBCT（CA - CBCT）；3. FB和BH状态下的新型RG - CBCT。通过计算同时真值和性能水平估计（STAPLE）一致性轮廓来评估观察者间轮廓变异性，然后计算个体评估者与一致性轮廓之间的平均对称表面距离（ASSD）和骰子相似系数（DSC），以比较不同图像类型。
在7例患者中，对27组图像上的18个危及器官（OARs）进行了评估。通过ASSD分析，对于所有OARs和患者，BH和FB状态下的RG - CBCT在观察者间轮廓勾画变异性方面均不劣于simCT（p < 0.001），而CA - CBCT则不然（p = 0.923）。在ASSD分析中，与simCT相比，RG - CBCT（FB和BH）在腹部和乳腺亚部位也同样不劣（p < 0.025）。在DSC比较中，对于所有部位，RG - CBCT和CA - CBCT均不劣于simCT（p > 0.025）。
根据ASSD标准，使用新型RG - CBCT图像时观察者间勾画OARs的能力不劣于simCT，但根据DSC标准则不然。
