Background and purpose. Accurate volume delineation plays an essential role in radiotherapy. Contouring is a potential source of uncertainties in radiotherapy treatment planning that could affect treatment outcomes. Therefore, reducing the degree of contouring uncertainties is crucial. The role of utilized imaging modality in the organ delineation uncertainties has been investigated. This systematic review explores the influential factors on inter-and intra-observer uncertainties of target volume and organs at risk (OARs) delineation focusing on the used imaging modality for these uncertainties reduction and the reported subsequent histopathology and follow-up assessment. Methods and materials. An inclusive search strategy has been conducted to query the available online databases (Scopus, Google Scholar, PubMed, and Medline). ‘Organ at risk’, ‘target’, ‘delineation’, ‘uncertainties’, ‘radiotherapy’ and their relevant terms were utilized using every database searching syntax. Final article extraction was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Included studies were limited to the ones published in English between 1995 and 2020 and that just deal with computed tomography (CT) and magnetic resonance imaging (MRI) modalities. Results. A total of 923 studies were screened and 78 were included of which 31 related to the prostate 20 to the breast, 18 to the head and neck, and 9 to the brain tumor site. 98% of the extracted studies performed volumetric analysis. Only 24% of the publications reported the dose deviations resulted from variation in volume delineation Also, heterogeneity in studied populations and reported geometric and volumetric parameters were identified such that quantitative synthesis was not appropriate. Conclusion. This review highlightes the inter- and intra-observer variations that could lead to contouring uncertainties and impede tumor control in radiotherapy. For improving volume delineation and reducing inter-observer variability, the implementation of well structured training programs, homogeneity in following consensus and guidelines, reliable ground truth selection, and proper imaging modality utilization could be clinically beneficial.

背景和目的。准确的体积描绘在放射治疗中起着至关重要的作用。轮廓是放射治疗计划中可能影响治疗结果的不确定性的潜在来源。因此，降低轮廓不确定性的程度至关重要。已经研究了利用的成像方式在器官描绘不确定性中的作用。本系统评价探讨了目标体积和风险器官 (OAR) 描绘的观察者间和观察者内不确定性的影响因素，重点是用于减少这些不确定性的成像方式以及报告的后续组织病理学和后续评估。方法和材料。已采用包容性搜索策略来查询可用的在线数据库（Scopus、Google Scholar、PubMed 和 Medline）。“处于风险中的器官”、“目标”、“描绘”、“不确定性”、“放射治疗”及其相关术语被使用每个数据库搜索语法来使用。最终文章提取是按照系统评价和元分析 (PRISMA) 指南的首选报告项目进行的。纳入的研究仅限于 1995 年至 2020 年间以英文发表的研究，并且仅涉及计算机断层扫描 (CT) 和磁共振成像 (MRI) 模式。结果。共筛选了 923 项研究，包括 78 项，其中 31 项与前列腺有关，20 项与乳房有关，18 项与头颈部有关，9 项与脑肿瘤部位有关。98% 的提取研究进行了体积分析。只有 24% 的出版物报告了剂量偏差是由体积描绘的变化引起的。此外，研究人群的异质性以及报告的几何和体积参数被确定，因此定量合成不合适。结论。这篇综述强调了观察者之间和观察者内部的变化，这些变化可能导致轮廓不确定性并阻碍放射治疗中的肿瘤控制。为了改善体积描绘和减少观察者间的变异性，实施结构良好的培训计划、遵循共识和指南的同质性、可靠的地面实况选择以及适当的成像方式利用可能在临床上是有益的。