Department of Radiation Oncology, London Regional Cancer Program, London, Ont., Canada.
Radiother Oncol. 2010 May;95(2):166-71. doi: 10.1016/j.radonc.2009.12.028. Epub 2010 Feb 1.
To investigate inter-observer and intra-observer target volume delineation (TVD) error in 4D-CT imaging of thoracic tumours.
Primary and nodal gross tumour volumes (GTV) of 10 lung tumours on the 10 respiratory phases of a 4D-CT scan were contoured by six radiation oncologist observers. Inter-observer and intra-observer variability were assessed by the coefficient of variation (COV) and the volume overlap index (VOI). ANOVA was performed to assess differences in inter-observer and intra-observer variability based on patient case difficulty, respiratory phase, physician seniority, and physician observer.
VOI analysis determined that inter-observer was a more significant source of error than intra-observer variability. VOI improved with the use of 4D-CT as compared to conventional CT. ANOVA analysis for COVs found case difficulty (easy versus difficult) to be significant for inter-observer primary tumour and intra-observer nodal disease delineation. Physician seniority, respiratory phase, and individual physician were not found to be significant for TVD error.
Variability in TVD is a major source of error in 4D-CT treatment planning. Development of measures to reduce inter-observer and intra-observer TVD variability are necessary in order to deliver high quality radiotherapy.
研究在胸部肿瘤的 4D-CT 成像中，观察者间和观察者内靶区勾画（TVD）的误差。
在 4D-CT 扫描的 10 个呼吸时相中，对 10 个肺部肿瘤的原发肿瘤和淋巴结大体肿瘤体积（GTV）进行勾画，由 6 名放射肿瘤学家观察者进行勾画。通过变异系数（COV）和体积重叠指数（VOI）评估观察者间和观察者内的变异性。采用方差分析（ANOVA）评估基于患者病例难度、呼吸时相、医生资历和医生观察者的观察者间和观察者内变异性的差异。
VOI 分析表明，观察者间的误差比观察者内变异性更为显著。与常规 CT 相比，使用 4D-CT 可改善 VOI。对 COV 的 ANOVA 分析发现，对于原发性肿瘤的观察者间和淋巴结疾病的观察者内勾画，病例难度（简单与困难）是一个显著的影响因素。医生资历、呼吸时相和个别医生并不是 TVD 误差的显著因素。
TVD 的变异性是 4D-CT 治疗计划中的一个主要误差源。为了提供高质量的放射治疗，有必要制定措施来减少观察者间和观察者内的 TVD 变异性。
