摘要目的 探讨保乳术后部分乳腺外照射(EB-PBI)自主呼吸控制(ABC)不同呼吸状态体积重合度及其差异,从靶区体积重合的角度,表述ABC辅助呼吸运动对EB-PBI分次内靶区位移的影响.方法 对术腔放置银夹拟行EB-PBI的患者行乳腺托架固定ABC辅助CT模拟定位,同时采集适度深吸气呼吸控制(mDIBH)状态、自由呼吸(FB)状态、深吸气呼吸控制(DEBH)状态各2套CT图像.应用Pinnacle3治疗计划系统,进行2套mDIBH图像间、2套FB图像间、2套DEBH图像间及mDIBH与DEBH图像间自动融合,计算融合图像.选定进行融合的2套图像的大体肿瘤体积(GTV)、临床靶区体积(CTV)、计划靶区体积(PTV)的重合度,比较同一配准中3种靶区各自重合度间及不同配准中同一种靶区重合度间的差异.结果 mDIBH/mDIBH配准中,GTV/GTV、CTV/CTV和PTV/PTV重合度分别为(83.54±11.41)%、(93.00±6.49)%和(95.26±4.90)%,GTV/GTV与CTV/CTV、GTV/GTV与PTV/PTV重合度间差异均有统计学意义(P＜0.05),而CTV/CTV与PTV/PTV重合度间差异无统计学意义(P＞0.05).FB/FB配准中,GTV/GTV、CTV/CTV、PTV/PTV重合度分别为(72.55±29.10)%、(89.36±9.53)%和(92.47±7.25)%,GTV/GTV与CTV/CTV、CTV/CTV与PTV/PTV重合度间差异均无统计学意义(均P＞0.05),而GTV/GTV与PTV/PTV重合度间差异有统计学意义(P＜0.05).DEBH/DEBH配准中,GTV/GTV、CTV/CTV、PTV/PTV重合度分别为(79.48±22.31)%、(92.83±6.77)%和(95.05±4.81)%,3组靶区两两间重合度差异均有统计学意义(均P＜0.05).mDIBH/mDIBH与DEBH/DEBH间、mDIBH/mDIBH与FB/FB间、FB/FB与DEBH/DEBH间的GTV、CTV和PTV重合度差异均无统计学意义(均P＞0.05),而mDIBH/mDIBH与mDIBH/DEBH间、FB/FB与mDIBH/DEBH间的GTV、CTV和PTV重合度差异均有统计学意义(均P＜0.05).结论 ABC辅助实施EB-PBI,两次mDIBH间、两次FB间和两次DEBH间各靶区体积重合度差异不明显,且三者的PTV/PTV重合度均达到较高水平.因此,从靶区重合度的角度,若施照前进行在线摆位误差校正,EB-PBI实施进行呼吸控制的必要性值得商榷.

abstractsObjective To explore the overlap ratio of the target volume in different respiratory statuses of active breath control(ABC)and their differences during external-beam partial breast irradiation (EB-PBI), and from the perspective of target volume overlap to determine the influence of the ABC-assisted breathing condition on intra-fractional target movement of EB-PBI. Methods The patients, who received breast-conserving surgery with silver clips marked at the margins of the cavity and were suitable for EB-PBI,were immobilized on the breast bracket to undertake CT simulation assisted by ABC device, six sets of CT simulation images including two sets of image in state of moderate deep inspiration breathing control (mDIBH), two sets of images in state of free breath(FB)and two sets of images in state of deep expiration breathing control(DEBH)were obtained. The six sets of images were transferred to Piunacle3 treatment planning system(TPS), then automatic fusion and registration between two sets of mDIBH images, two sets of FB images, two sets of DEBH images and mDIBH image and DEBH image were achieved separately.Thereafter, the overlap ratios of GTV with GTV, CTV with CTV, PTV with PTV were calculated by the Pinnacle3 TPS. The differences between the overlap ratios of the three kinds of targets in the same registered image and the difference between the overlap ratios of the same kind of target in the different registered images were statistically analyzed using statistical package of SPSS 11.5. Results Based on mDIBH/mDIBH registration, the overlap ratios of GTV/GTV, CTV/CTV and PTV/PTV were(83.54 ± 11.41)%,(93.00 ±6.49)% , and(95.26 ± 4.90)% , respectively, and the differences of the overlap ratios between GTV/GTV and CTV/CTV, GTV/GTV and PTV/PTV were all statistically significant(P ＜ 0.05), but statistically not significant between CTV/CTV and PTV/PTV(P ＞ 0. 05). Based on FB/FB registration, the overlap ratios of GTV/GTV, CTV/CTV and PTV/PTV were(72.55 ±29. 10)%,(89.36 ±9.53)% and(92. 47 ±7.25)% , respectively, and the differences of the overlap ratios between GTV/GTV and CTV/CTV, CTV/CTV and PTV/PTV were all not statistically significant(P ＞ 0. 05), but statistically significant between GTV/GTV and PTV/PTV(P ＜ 0.05). Based on DEBH/DEBH registration, the overlap ratios of GTV/GTV, CTV/CTV and PTV/PTV were(79.48 ± 22.31)%,(92.83 ± 6.77)% and(95.05 ± 4. 81)%,respectively, and the differences of the overlap ratios between GTV/GTV and CTV/CTV(P =0.000),CTV/CTV and PTV/PTV(P = 0. 037), GTV/GTV and PTV/PTV(P = 0. 000)were statistically all significant(P=0.000). The differences of the overlap ratios of GTV/GTV, CTV/CTV, and PTV/PTV(P=0.000)between mDIBH/mDIBH and DEBH/DEBH, mDIBH/mDIBH and FB/FB, FB/FB and DEBH/DEBH were all statistically significant(P = 0. 000), and not statistically significant between mDIBH/mDIBH and mDIBH/DEBH, FB/FB and mDIBH/DEBH. Conclusions During the delivering of EB-PBI assisted by ABC, the intra-fractional overlap ratios of the target volume between the same breathing state is increasing in the order of GTV/GTV → CTV/CTV → PTV/PTV. The difference of the overlap ratios of the target volumes between mDIBH and mDIBH, FB and FB, DEBH and DEBH is not significant, and the overlap ratios of PTV/PTV in the three breathing statuses of mDIBH, FB and DEBH reaches a higher level. Therefore, from the perspective of target volume overlap, if the setup error is corrected online before delivering, the necessity of breathing control during delivering of EB-PBI is worthy discussing.