Moseley Douglas J, White Elizabeth A, Wiltshire Kirsty L, Rosewall Tara, Sharpe Michael B, Siewerdsen Jeffrey H, Bissonnette Jean-Pierre, Gospodarowicz Mary, Warde Padraig, Catton Charles N, Jaffray David A
Radiation Medicine Program, Princess Margaret Hospital, Toronto, ON, Canada.
Int J Radiat Oncol Biol Phys. 2007 Mar 1;67(3):942-53. doi: 10.1016/j.ijrobp.2006.10.039.
The aim of this work was to assess the accuracy of kilovoltage (kV) cone-beam computed tomography (CBCT)-based setup corrections as compared with orthogonal megavoltage (MV) portal image-based corrections for patients undergoing external-beam radiotherapy of the prostate.
Daily cone-beam CT volumetric images were acquired after setup for patients with three intraprostatic fiducial markers. The estimated couch shifts were compared retrospectively to patient adjustments based on two orthogonal MV portal images (the current clinical standard of care in our institution). The CBCT soft-tissue based shifts were also estimated by digitally removing the gold markers in each projection to suppress the artifacts in the reconstructed volumes. A total of 256 volumetric images for 15 patients were analyzed.
The Pearson coefficient of correlation for the patient position shifts using fiducial markers in MV vs. kV was (R2 = 0.95, 0.84, 0.81) in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively. The correlation using soft-tissue matching was as follows: R2 = 0.90, 0.49, 0.51 in the LR, AP and SI directions. A Bland-Altman analysis showed no significant trends in the data. The percentage of shifts within a +/-3-mm tolerance (the clinical action level) was 99.7%, 95.5%, 91.3% for fiducial marker matching and 99.5%, 70.3%, 78.4% for soft-tissue matching.
Cone-beam CT is an accurate and precise tool for image guidance. It provides an equivalent means of patient setup correction for prostate patients with implanted gold fiducial markers. Use of the additional information provided by the visualization of soft-tissue structures is an active area of research.
本研究旨在评估对于接受前列腺外照射放疗的患者，基于千伏（kV）锥形束计算机断层扫描（CBCT）的摆位校正与基于正交兆伏（MV）门静脉图像的校正相比的准确性。
为有三个前列腺内基准标记物的患者摆位后，每日采集锥形束CT容积图像。将估计的治疗床移动与基于两张正交MV门静脉图像（我们机构当前的临床护理标准）的患者调整进行回顾性比较。还通过在每个投影中数字移除金标记物以抑制重建容积中的伪影，来估计基于CBCT软组织的移动。共分析了15名患者的256幅容积图像。
在左右（LR）、前后（AP）和上下（SI）方向上，使用MV与kV基准标记物的患者位置移动的Pearson相关系数分别为（R2 = 0.95、0.84、0.81）。使用软组织匹配的相关性如下：LR、AP和SI方向上的R2分别为0.90、0.49、0.51。Bland-Altman分析显示数据无显著趋势。在±3毫米容差（临床行动水平）内的移动百分比，基准标记物匹配分别为99.7%、95.5%、91.3%，软组织匹配分别为99.5%、70.3%、78.4%。
锥形束CT是一种准确且精确的图像引导工具。对于植入金基准标记物的前列腺患者，它提供了等效的患者摆位校正方法。利用软组织结构可视化提供的额外信息是一个活跃的研究领域。
