Department of Radiation Oncology, Washington University, St Louis, Missouri.
Radiation Oncology Services, Riverdale, Georgia.
Pract Radiat Oncol. 2012 Apr-Jun;2(2):97-105. doi: 10.1016/j.prro.2011.06.013. Epub 2011 Jul 30.
Accelerated partial breast irradiation is an emerging treatment option for early stage breast cancer. With accelerated partial breast irradiation, patient setup, and target registration accuracy is vital. The current study compared various methods for isocenter placement accuracy.
Twenty-three patients treated on an institutional-approved partial breast irradiation protocol were monitored at each treatment fraction. All patients included in this study underwent clip placement at the time of surgery. Patients underwent computed tomographic simulation and surface contours were used to reconstruct a reference surface map. At the treatment machine, patients were initially positioned by laser alignment to tattoos. Orthogonal kilovoltage imaging of the chest wall, followed by video surface mapping of the breast, was performed. This video surface map was matched to the reference surface map to adjust the couch position. Verification orthogonal chest wall imaging and video surface mapping was again performed. The accuracy of setup by laser, orthogonal imaging of the chest wall, and surface alignment was retrospectively compared using the centroid clip position as the reference standard. The impact of setup error by surface alignment and by orthogonal kilovoltage imaging on planning target volume coverage was then calculated.
Laser-based positioning resulted in a residual setup error of 3.9 ± 3.7 mm, 4.6 ± 3.9 mm, and 4.3 ± 4.5 mm in the posterior-anterior (P-A), inferior-superior (I-S), and left-right (L-R) directions, respectively, using clips as the reference standard. Setup based on bony anatomy with orthogonal imaging resulted in residual setup error of 3.2 ± 2.9 (P-A), 4.2 ± 3.5 (I-S), and 4.7 ± 5.3 mm (L-R). Setup with video surface mapping resulted in a residual setup error of 1.9 ± 2.2, 1.8 ± 1.9, and 1.8 ± 2.1 mm in the P-A, I-S, and L-R directions, respectively. Vector spatial deviation was 8.8 ± 4.2, 8.3 ± 3.8, and 4.0 ± 2.3 mm with laser, chest wall on board imaging, and video surface mapping based setup, respectively. Setup by video surface mapping resulted in improved dosimetric coverage of the planning target volume when compared with orthogonal imaging of the chest wall (V100 96.0% ± 0.1% vs 89.3% ± 0.2%; V95 99.7% ± 0.01% vs 98.6% ± 0.01%, P < .05).
Video surface mapping of the breast is a more accurate method for isocenter placement in comparison to conventional laser-based alignment or orthogonal kilovoltage imaging of the chest wall.
加速部分乳房照射是早期乳腺癌的一种新兴治疗选择。在加速部分乳房照射中，患者的设置和靶区注册准确性至关重要。本研究比较了各种确定等中心位置的方法。
对 23 例在机构批准的部分乳房照射方案中接受治疗的患者，在每次治疗时进行监测。本研究中所有患者在手术时均进行夹片放置。患者接受计算机断层扫描模拟，并使用表面轮廓重建参考表面图。在治疗机上，患者首先通过激光对准纹身进行定位。然后对胸壁进行正交千伏成像，并对乳房进行视频表面映射。将此视频表面图与参考表面图匹配，以调整治疗床位置。再次进行验证性正交胸壁成像和视频表面映射。使用夹片作为参考标准，回顾性比较激光、胸壁正交成像和表面对准的设置精度。然后计算表面对准和正交千伏成像设置误差对计划靶区覆盖的影响。
使用夹片作为参考标准，激光定位的结果为后前（P-A）、上下（I-S）和左右（L-R）方向的残余设置误差分别为 3.9 ± 3.7、4.6 ± 3.9 和 4.3 ± 4.5mm。基于骨性解剖结构的正交成像的设置结果为 P-A、I-S 和 L-R 方向的残余设置误差分别为 3.2 ± 2.9、4.2 ± 3.5 和 4.7 ± 5.3mm。视频表面映射的设置结果为 P-A、I-S 和 L-R 方向的残余设置误差分别为 1.9 ± 2.2、1.8 ± 1.9 和 1.8 ± 2.1mm。使用激光、胸壁在线成像和视频表面映射进行设置时，矢量空间偏差分别为 8.8 ± 4.2、8.3 ± 3.8 和 4.0 ± 2.3mm。与胸壁正交成像相比，视频表面映射的设置可改善计划靶区的剂量覆盖（V100 96.0% ± 0.1% 比 89.3% ± 0.2%；V95 99.7% ± 0.01% 比 98.6% ± 0.01%，P <.05）。
与传统的基于激光的对准或胸壁正交千伏成像相比，乳房的视频表面映射是一种更准确的等中心定位方法。
