Glide-Hurst Carri K, Shah Mira M, Price Ryan G, Liu Chang, Kim Jinkoo, Mahan Meredith, Fraser Correen, Chetty Indrin J, Aref Ibrahim, Movsas Benjamin, Walker Eleanor M
Department of Radiation Oncology, Henry Ford Health Systems, Detroit, Michigan.
Department of Radiation Oncology, Henry Ford Health Systems, Detroit, Michigan.
Int J Radiat Oncol Biol Phys. 2015 Mar 1;91(3):604-11. doi: 10.1016/j.ijrobp.2014.11.003. Epub 2015 Jan 30.
To evaluate intrafraction variability and deformation of the lumpectomy cavity (LC), breast, and nearby organs.
Sixteen left-sided postlumpectomy and 1 bilateral breast cancer cases underwent free-breathing CT (FBCT) and 10-phase 4-dimensional CT (4DCT). Deformable image registration was used for deformation analysis and contour propagation of breast, heart, lungs, and LC between end-exhale and end-inhale 4DCT phases. Respiration-induced motion was calculated via centroid analysis. Two planning target volumes (PTVs) were compared: PTV(FBCT) from the FBCT volume with an isotropic 10 mm expansion (5 mm excursion and 5 mm setup error) and PTV(4DCT) generated from the union of 4DCT contours with isotropic 5 mm margin for setup error. Volume and geometry were evaluated via percent difference and bounding box analysis, respectively. Deformation correlations between breast/cavity, breast/lung, and breast/heart were evaluated. Associations were tested between cavity deformation and proximity to chest wall and breast surface.
Population-based 3-dimensional vector excursions were 2.5 ± 1.0 mm (range, 0.8-3.8 mm) for the cavity and 2.0 ± 0.8 mm (range, 0.7-3.0 mm) for the ipsilateral breast. Cavity excursion was predominantly in the anterior and superior directions (1.0 ± 0.8 mm and -1.8 ± 1.2 mm, respectively). Similarly, for all cases, LCs and ipsilateral breasts yielded median deformation values in the superior direction. For 14 of 17 patients, the LCs and breast interquartile ranges tended toward the anterior direction. The PTV(FBCT) was 51.5% ± 10.8% larger (P<.01) than PTV(4DCT). Bounding box analysis revealed that PTV(FBCT) was 9.8 ± 1.2 (lateral), 9.0 ± 2.2 (anterior-posterior), and 3.9 ± 1.8 (superior-inferior) mm larger than PTV(4DCT). Significant associations between breast and cavity deformation were found for 6 of 9 axes. No dependency was found between cavity deformation and proximity to chest wall or breast surface.
Lumpectomy cavity and breast deformation and motion demonstrated large variability. A PTV(4DCT) approach showed value in patient-specific margins, particularly if robust interfraction setup analysis can be performed.
评估保乳手术腔（LC）、乳房及附近器官的分次内变异性和变形情况。
16例左侧保乳术后患者及1例双侧乳腺癌患者接受了自由呼吸CT（FBCT）和10期四维CT（4DCT）检查。采用可变形图像配准技术对呼气末和吸气末4DCT相位之间乳房、心脏、肺和LC的变形情况及轮廓传播进行分析。通过质心分析计算呼吸诱导的运动。比较了两个计划靶区（PTV）：来自具有各向同性10mm扩展（5mm偏移和5mm摆位误差）的FBCT容积的PTV(FBCT)，以及由具有各向同性5mm摆位误差余量的4DCT轮廓联合生成的PTV(4DCT)。分别通过百分比差异和边界框分析评估容积和几何形状。评估了乳房/腔、乳房/肺和乳房/心脏之间的变形相关性。测试了腔变形与距胸壁和乳房表面的距离之间的关联。
基于群体的三维矢量偏移，腔为2.5±1.0mm（范围0.8 - 3.8mm），同侧乳房为2.0±0.8mm（范围0.7 - 3.0mm）。腔的偏移主要在前后方向（分别为1.0±0.8mm和 - 1.8±1.2mm）。同样，对于所有病例，LC和同侧乳房在头侧方向产生中位数变形值。在17例患者中的14例中，LC和乳房的四分位间距倾向于前方向。PTV(FBCT)比PTV(4DCT)大51.5%±10.8%（P<.01）。边界框分析显示，PTV(FBCT)在横向比PTV(4DCT)大9.8±1.2mm，在前后方向大9.0±2.2mm，在上下方向大3.9±1.8mm。在9个轴中的6个轴上发现乳房和腔变形之间存在显著关联。未发现腔变形与距胸壁或乳房表面的距离之间存在相关性。
保乳手术腔和乳房的变形及运动表现出较大的变异性。PTV(4DCT)方法在患者特异性边界方面显示出价值，特别是如果能够进行稳健的分次间摆位分析。
