a Department of Radiotherapy , University Medical Center Utrecht , Utrecht , The Netherlands.
b Department of Radiation Oncology , University Medical Center Utrecht , Utrecht , The Netherlands.
Acta Oncol. 2018 Jul;57(7):941-949. doi: 10.1080/0284186X.2018.1438655. Epub 2018 Feb 19.
To assess intra- and inter-fraction motion uncertainties, due to displacements of the tumor bed (TB) and organs at risk (OAR), as well as intra- and inter-fraction patient set-up uncertainties, due to positioning variations, during image-guided radiation therapy (IGRT) in children with Wilms' tumor.
Four-dimensional computed tomography (4D-CT) and daily pre- and post-treatment cone-beam CT (CBCT)-scans of 15 patients (average 4, range 1-8 years) undergoing flank irradiation after nephrectomy were analyzed. TB (marked by four surgical clips) and OAR motion uncertainties were quantified by displacements of the center of mass in all orthogonal directions. Translational and rotational bone off-sets were recorded for patient set-up uncertainties assessment in all orthogonal directions. The average results, systematic and random errors were computed.
Average intra- and inter-fraction motion uncertainties were ≤1.1 mm (range: [-6.9;7.9] mm) for the TB and ≤3.2 mm (range: [-9.1;9.6] mm) for the OAR. Average intra- and inter-fraction patient set-up uncertainties were ≤0.1 mm (range: [-3.3;4.8] mm) and ≤0.9° (range: [0.0;2.8°]). Both motion and patient set-up uncertainties were larger for the cranio-caudal direction. Calculated systematic and random errors were ≤2.4 mm for the motion uncertainties and ≤0.8 mm/0.7 for the patient set-up uncertainties.
Average motion and patient set-up uncertainties during radiotherapy treatment were found to be limited. However, uncertainties were larger for the cranio-caudal direction and outliers were found in all orthogonal directions. When having available 4D-CT and CBCT information, the use of patient-specific and anisotropic safety margin expansions is advised for both target volume and OAR.
评估由于肿瘤床（TB）和危及器官（OAR）的位移以及由于定位变化引起的分次内和分次间患者摆位不确定性，导致接受肾切除术后接受侧部照射的儿童在图像引导放射治疗（IGRT）期间的 TB 和 OAR 运动不确定性。
对 15 名（平均年龄 4 岁，范围 1-8 岁）接受肾切除术后接受侧部照射的患者的 4D-CT 和每日治疗前和治疗后锥形束 CT（CBCT）扫描进行了分析。通过在所有正交方向上的质心位移来量化 TB（由四个手术夹标记）和 OAR 运动不确定性。记录了用于所有正交方向上的患者摆位不确定性评估的平移和旋转骨偏移。计算了平均结果、系统误差和随机误差。
TB 的平均分次内和分次间运动不确定性为≤1.1 mm（范围：[-6.9；7.9] mm），OAR 的平均分次内和分次间运动不确定性为≤3.2 mm（范围：[-9.1；9.6] mm）。TB 的平均分次内和分次间患者摆位不确定性为≤0.1 mm（范围：[-3.3；4.8] mm）和≤0.9°（范围：[0.0；2.8°]）。无论是运动还是患者摆位不确定性，头脚方向都更大。计算出的系统误差和随机误差对于运动不确定性≤2.4 mm，对于患者摆位不确定性≤0.8 mm/0.7。
在放射治疗过程中，平均运动和患者摆位不确定性被发现是有限的。然而，头脚方向的不确定性更大，并且在所有正交方向上都发现了异常值。当有 4D-CT 和 CBCT 信息时，建议为靶体积和 OAR 使用患者特异性和各向异性安全裕度扩展。
