Clinical Institute, Aarhus University, Aarhus, Denmark.
Acta Oncol. 2011 Aug;50(6):918-25. doi: 10.3109/0284186X.2011.577806.
Daily organ motion occurring during the course of radiotherapy in the pelvic region leads to uncertainties in the doses delivered to the tumour and the organs at risk. Motion patterns include both volume and shape changes, calling for deformable image registration (DIR), in approaches involving dose accumulation and adaptation. In this study, we tested the performance of a DIR application for contour propagation from the treatment planning computed tomography (pCT) to repeat cone-beam CTs (CBCTs) for a set of prostate cancer patients.
The prostate, rectum and bladder were delineated in the pCT and in six to eight repeat CBCTs for each of five patients. The pCT contours were propagated onto the corresponding CBCT using the Multi-modality Image Registration and Segmentation application, resulting in 36 registrations. Prior to the DIR, a rigid registration was performed. The algorithm used for the DIR was based on a 'demons' algorithm and the performance of it was examined quantitatively using the Dice similarity coefficient (DSC) and qualitatively as visual slice-by-slice scoring by a radiation oncologist grading the deviations in shape and/or distance relative to the anatomy.
The average DSC (range) for the DIR over all scans and patients was 0.80 (0.65-0.87) for prostate, 0.77 (0.63-0.87) for rectum and 0.73 (0.34-0.91) for bladder, while the corresponding DSCs for the rigid registrations were 0.77 (0.65-0.86), 0.71 (0.55-0.82) and 0.64 (0.33-0.87). The percentage of propagated contours of good/acceptable quality was 45% for prostate; 20% for rectum and 33% for bladder. For the bladder, there was an association between the average DSC and the different scores of the qualitative evaluation.
DIR improved the performance of pelvic organ contour propagation from the pCT to CBCTs as compared to rigid registration only. Still, a large fraction of the propagated rectum and bladder contours were unacceptable. The image quality of the CBCTs was sub-optimal and the usability of CBCTs for dose accumulation and adaptation purposes is therefore likely to benefit from improved image quality and improvements of the DIR algorithm.
在盆腔区域放射治疗过程中，每天发生的器官运动导致肿瘤和危险器官的剂量输送存在不确定性。运动模式包括体积和形状的变化，这就需要进行可变形图像配准（DIR），以便在涉及剂量积累和适应的方法中进行。在这项研究中，我们测试了一种 DIR 应用程序在从治疗计划计算机断层扫描（pCT）到重复锥形束 CT（CBCT）的前列腺癌患者集上进行轮廓传播的性能。
在五个患者的每一个患者的 pCT 和六到八次重复 CBCT 中对前列腺、直肠和膀胱进行了描绘。使用多模态图像配准和分割应用程序将 pCT 轮廓传播到相应的 CBCT 上，总共进行了 36 次配准。在进行 DIR 之前，进行了刚性配准。用于 DIR 的算法基于“恶魔”算法，并通过使用 Dice 相似系数（DSC）进行定量检查以及由放射肿瘤学家进行的视觉切片评分来定性检查其性能，根据形状和/或距离相对于解剖结构的偏差对其进行分级。
对于所有扫描和患者，DIR 的平均 DSC（范围）分别为前列腺为 0.80（0.65-0.87），直肠为 0.77（0.63-0.87），膀胱为 0.73（0.34-0.91），而刚性配准的相应 DSCs 分别为 0.77（0.65-0.86），0.71（0.55-0.82）和 0.64（0.33-0.87）。前列腺可接受质量的传播轮廓百分比为 45%；直肠为 20%；膀胱为 33%。对于膀胱，平均 DSC 与定性评估的不同分数之间存在关联。
与仅进行刚性配准相比，DIR 提高了从 pCT 到 CBCT 的盆腔器官轮廓传播的性能。尽管如此，仍有很大一部分传播的直肠和膀胱轮廓是不可接受的。CBCT 的图像质量较差，因此，为了进行剂量积累和适应的目的，CBCT 的可用性可能受益于提高图像质量和改进 DIR 算法。
