Nella Francesca, Tanadini-Lang Stephanie, Dal Bello Riccardo
Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland.
Phys Imaging Radiat Oncol. 2025 Apr 4;34:100764. doi: 10.1016/j.phro.2025.100764. eCollection 2025 Apr.
In a magnetic resonance (MR) only planning workflow, MR image is the sole dataset acquired. In order to calculate the dose deposition, a synthetic CT (sCT) is generated to substitute the planning computed tomography (CT). This study aimed to establish acceptance criteria for the clinical implementation of patient-specific quality assurance (PSQA) for sCT.
A retrospective study was conducted on 60. 30 patients underwent a CT scan in treatment position and an MR in diagnostic position. 30 patients had both CT and MR images acquired in treatment position. For the latter group, a sCT for dose calculation was generated and compared against three PSQA methods: recalculation on (A) water override of the body, (B) tissue classes with bulk density overrides and (C) planning CT. The relative dose differences (ΔD [%]) between the sCT and the PSQA methos were evaluated.
ΔD for PTV Dmean for method (A) were within 3% for pelvis and 4% for brain cohorts, with standard deviations below 1%. Methods (B) and (C) remained within 2% and 1%, respectively, with deviations up to 1%.
The present study proposes a robust PSQA method for MR-only planning. Method (A) is a valuable tool for identifying potential large outliers for Dmean deviations (> 5 %) and it is proposed as the routine PSQA. Method (B) can be used for pelvis cases to improve detection to the 2 % level if method (A) fails. If both (A) and (B) fail, method (C) can be used as a fall-back.
在仅使用磁共振（MR）的计划流程中，MR图像是唯一获取的数据集。为了计算剂量沉积，需生成合成CT（sCT）以替代计划计算机断层扫描（CT）。本研究旨在为sCT的患者特异性质量保证（PSQA）临床应用建立验收标准。
对60例患者进行回顾性研究。30例患者在治疗体位进行了CT扫描，在诊断体位进行了MR扫描。另外30例患者在治疗体位同时获取了CT和MR图像。对于后一组患者，生成用于剂量计算的sCT，并与三种PSQA方法进行比较：（A）在身体水替代物上重新计算，（B）具有体密度替代物的组织类别，以及（C）计划CT。评估了sCT与PSQA方法之间的相对剂量差异（ΔD [%]）。
方法（A）对于盆腔PTV Dmean的ΔD在盆腔队列中在3%以内，在脑队列中在4%以内，标准差低于1%。方法（B）和（C）分别保持在2%和1%以内，偏差高达1%。
本研究提出了一种用于仅MR计划的稳健PSQA方法。方法（A）是识别Dmean偏差（> 5%）潜在大异常值的有价值工具，建议作为常规PSQA。如果方法（A）失败，方法（B）可用于盆腔病例以将检测提高到2%水平。如果（A）和（B）都失败，方法（C）可作为备用方法。
