乳腺癌保乳术后锥形束CT引导全乳精确放疗的最佳配准模板选择

目的 筛选乳腺癌保乳术后锥形束CT(CBCT)图像引导全乳精确放疗的最佳配准模板。 方法 2006年4月到2009年7月在我院行乳腺癌保乳术后全乳精确放疗的12例患者入组。应用Varian 23EX直线加速器机载锥形束CT获取CBCT图像。在计划CT图像的乳腺术腔及周围腺体标注6个易辨认的点(直径为1 mm)作为参考。分别以乳腺轮廓、手术银夹、乳腺腺体、乳腺相邻肋骨以及乳腺同侧肺外轮廓为模板进行手动配准并记录配准时间。配准后立即在CBCT图像上对应标注上述6个参考点,并测量计划CT与CBCT图像上所标注对应参考点之间的距离,计算每位患者每种配准模板下的配准误差。应用SPSS 13.0统计软件对配准误差进行单项方差分析。结果 以乳腺轮廓、手术银夹、乳腺腺体、乳腺相邻肋骨以及乳腺同侧肺外轮廓为模板,配准误差分别为(0.60 ± 0.20)、 (0.43 ± 0.15)、 (0.49 ± 0.19)、(0.69 ± 0.36)和(0.94 ± 0.49)cm, 配准所需要的时间分别为(3.8 ± 1.1)、 (3.0 ± 0.9)、 (4.7 ± 1.7)、 (4.3 ± 1.3)和(4.5 ± 1.3) min。单因素方差分析显示,乳腺轮廓、乳腺腺体、手术银夹3种配准模板的配准误差之间差异无统计学意义(t = 0.48~1.36,P＞0.05),乳腺相邻肋骨与乳腺同侧肺外轮廓两种配准模板之间差异也无统计学意义,手术银夹与后两者之间差异有统计学意义(t = 2.08~4.08,P＜0.05)。结论 以乳腺相邻肋骨与乳腺同侧肺外轮廓两种模板配准准确性差,应综合考虑患者的个体情况以手术银夹、乳腺腺体或乳腺轮廓为模板进行配准。若同时考虑时间及准确性,以手术银夹配准最佳。

Optimization of registration template of cone-beam CT guided whole breast irradiation after lumpectomy of breast cancer

Objective To optimize the registration template of kilovohage cone-beam CT (CBCT) guided radiotherapy in whole breast irradiation(WBI)after lumpectomy of breast cancer.Methods From April 2006 to July 2009,twelve patients undergoing WBI with intensity-modulated radiotherapy (IMRT)were recruited in this study.All patients were performed with both conventional planning CT and CBCT integrated on Varian 23 EX.Six distinguishable referenee points(the diameter 1 mm)around the lumpectomy cavity and the surrounding gland on the planning CT image were marked.The images were manually registered offline based on the breast surface,surgical clips,breast gland,contiguous rib,ipsilaterai lung and its external contours,respectively.The same six reference points were then marked on the CBCT image.The performance of the five registration templates was compared using the concept of registration error,while the registration time was taken into account.The registration error was calculated based on the six reference points'translations between the planning CT image and CBCT image,and analyzed with SPSS 13.0 software using one-way ANOVA.Results The values of the registration error for the breast surface,surgical clips,breast gland, contiguous rib,ipsilateral lung and its external contours were(0.60±0.20),(0.43±0.15),(0.49±0.19),(0.69±0.36)and(0.94±0.49)cm,respectively,and the registration time were(3.8±1.1),(3.0±0.9),(4.7±1.7),(4.3±1.3)and(4.5±1.3)min,respectively.There was no statistical difforence between the breast surface,surgical clips and breast gland registration template(t=0.48-1.36,P>0.05),the same result trend to contiguous rib compared with ipsilateral lung(t=2.00,P=0.055),however,there was significant difference between surgical clips and the last two registration methods(t=2.08-4.08,P<0.05).Conclusion In this initial study with a modest number of patients,surgical clips show a best registration template from the standpoint of accuracy and efficiency,whereas contiguous rib and ipsilateral lung are not an ideal method.