Petillion Saskia, Verhoeven Karolien, Weltens Caroline, Van den Heuvel Frank
University Hospitals of Leuven.
J Appl Clin Med Phys. 2015 Jan 8;16(1):4796. doi: 10.1120/jacmp.v16i1.4796.
Image-guided position verification in breast radiotherapy is accurately performed with kilovoltage cone beam CT (kV-CBCT). The technique is, however, time-consuming and there is a risk for patient collision. Online position verification performed with orthogonal-angled mixed modality paired imaging is less time-consuming at the expense of inferior accuracy compared to kV-CBCT. We therefore investigated whether a new tangential-angled single modality paired imaging technique can reduce the residual error (RE) of orthogonal-angled mixed modality paired imaging. The latter was applied to 20 breast cancer patients. Tangential-angled single modality paired imaging was investigated in 20 breast and 20 breast cancer patients with locoregional lymph node irradiation. The central lung distance (CLD) residual error and the longitudinal residual error were determined during the first 5 treatment fractions. Off-line matching of the tangential breast field images, acquired after online position correction, was used. The mean, systematic, and random REs of each patient group were calculated. The systematic REs were checked for significant differences using the F-test. Tangential-angled single modality paired imaging significantly reduced the systematic CLD residual error of orthogonal-angled mixed modality paired imaging for the breast cancer patients, from 2.3 mm to 1.0 mm, and also significantly decreased the systematic longitudinal RE from 2.4 mm to 1.3 mm. PTV margins, which account for the residual error (PTVRE), were also calculated. The PTVRE margin needed to account for the RE of orthogonal-angled mixed modality paired imaging (i.e., 8 mm) was halved by tangential-angled single modality paired imaging. The differences between the systematic REs of tangential-angled single modality paired imaging of the breast cancer patients and the breast cancer patients with locoregional lymph node irradiation were not significant, yielding comparable PTVRE margins. In this study, we showed that tangential-angled single modality paired imaging is superior to orthogonal-angled mixed modality paired imaging to correct the position errors in whole breast radiotherapy.
在乳腺癌放射治疗中，千伏级锥形束CT（kV-CBCT）能够准确地进行图像引导的位置验证。然而，该技术耗时较长，且存在患者碰撞风险。与kV-CBCT相比，采用正交角度混合模态配对成像进行的在线位置验证耗时较短，但准确性较低。因此，我们研究了一种新的切线角度单模态配对成像技术是否能够减少正交角度混合模态配对成像的残余误差（RE）。将后者应用于20例乳腺癌患者。对20例乳腺癌患者以及20例接受局部区域淋巴结照射的乳腺癌患者进行了切线角度单模态配对成像研究。在前5个治疗分次期间测定中心肺距离（CLD）残余误差和纵向残余误差。使用在线位置校正后获取的切线乳腺野图像进行离线匹配。计算每个患者组的平均、系统和随机RE。使用F检验检查系统RE是否存在显著差异。对于乳腺癌患者，切线角度单模态配对成像显著降低了正交角度混合模态配对成像的系统CLD残余误差，从2.3毫米降至1.0毫米，同时也显著降低了系统纵向RE，从2.4毫米降至1.3毫米。还计算了考虑残余误差（PTVRE）的计划靶体积（PTV）边界。切线角度单模态配对成像使考虑正交角度混合模态配对成像RE所需的PTVRE边界（即8毫米）减半。乳腺癌患者与接受局部区域淋巴结照射的乳腺癌患者的切线角度单模态配对成像的系统RE之间的差异不显著，产生了相当的PTVRE边界。在本研究中，我们表明切线角度单模态配对成像在纠正全乳放疗中的位置误差方面优于正交角度混合模态配对成像。
