自适应放疗（ART）决策在评估解剖变化的重要性时，辅助图像检查需要剂量信息的支持。本研究评估了一种基于剂量测量的ART临床决策工作流程，利用变形配准将原始计划计算机断层扫描（CT）图像与日常锥束CT（CBCT）图像对准，以替代重新计划CT来估计剂量。我们使用12个头颈部患者病例进行回顾性研究，这些病例有一个地面真相-根据每日CBCT中明显的解剖变化制定的重新计划CT（rCT），以评估通过将原始计划CT的Hounsfield单位变形为每日CBCT解剖的合成CT（sCT）上进行的剂量评估的准确性。原始计划应用于sCT，并通过分析目标和风险器官的计划目标与地面真相rCT上的计算进行比较，评估了sCT的剂量准确性。比较了三种商用DIR算法。对于表现最佳的算法，大多数在sCT上计算的剂量指标与地面真相rCT上的计算相差不超过4 Gy（70 Gy处方剂量的5.7%）。推荐在头颈部sCT的剂量指标评估中使用±2.5 Gy（70 Gy处方的3.6%）的保守公差不确定度。合成CT对于自适应放疗工作流程是一项有价值的补充，合成CT剂量估计可以有效地与当前的观察评估结合使用，评估解剖变化的重要性。© 2023 The Authors.

Adaptive radiotherapy (ART) decision-making benefits from dosimetric information to supplement image inspection when assessing the significance of anatomical changes. This study evaluated a dosimetry-based clinical decision workflow for ART utilizing deformable registration of the original planning computed tomography (CT) image to the daily Cone Beam CT (CBCT) to replace the need for a replan CT for dose estimation.We used 12 retrospective Head & Neck patient cases having a ground truth - a replan CT (rCT) in response to anatomical changes apparent in the daily CBCT - to evaluate the accuracy of dosimetric assessment conducted on synthetic CTs (sCT) generated by deforming the original planning CT Hounsfield Units to the daily CBCT anatomy.The original plan was applied to the sCT and dosimetric accuracy of the sCT was assessed by analyzing plan objectives for targets and organs-at-risk compared to calculations on the ground-truth rCT. Three commercial DIR algorithms were compared.For the best-performing algorithms, the majority of dose metrics calculated on the sCTs differed by less than 4 Gy (5.7% of 70 Gy prescription dose). An uncertainty of ±2.5 Gy (3.6% of 70 Gy prescription) is recommended as a conservative tolerance when evaluating dose metrics on sCTs for head and neck.Synthetic CTs present a valuable addition to the adaptive radiotherapy workflow, and synthetic CT dose estimates can be effectively used in addition to the current practice of visually inspecting the overlay of the planning CT and CBCT to assess the significance of anatomical change.© 2023 The Authors.