摘要目的 了解左侧乳腺癌保乳术后采用深吸气屏气(DIBH)技术行全乳放疗(WBI)的治疗时间与放疗计划的相关性,明确放疗分次间重复性,观察治疗时心脏位置及剂量学变化,计算DIBH技术对左侧乳腺癌术后WBI摆位误差的影响.方法 前瞻性人组15例左侧乳腺癌保乳术后行WBI的患者,符合DIBH控制要求.比较治疗时间与计划射野数和跳数的关系,采用CBCT计算放疗分次间的摆位误差及PTV外放边界.将CBCT与计划CT图像融合,以验证放疗时心脏位置和剂量的准确性.组间数据行非参数Firedman检验.结果 采用DIBH技术放疗的平均单次治疗时间为4.6min,治疗时间与调强野最大子野数、总子野数和总跳数相关.平均心脏位移体积为19.1 cm3(3.8％),CBCT与计划CT的心脏Dmean相差5.1 cGy,心脏V5-V30差异无统计学意义(P＞0.05).摆位误差的系统误差(∑)和随机误差(σ)在左右、头脚、前后方向上分别为1.9、2.1、2.0 mm和1.3、1.3、1.4 mm.三维外扩的最小边界左右、头脚、前后方向上分别为5.7、6.2、6.0 mm.结论 左侧乳腺癌保乳术后采用DIBH技术行WBI未明显延长治疗时间,且治疗时间与放疗计划相关.DIBH技术各治疗分次间重复性良好,起到了保护心脏的作用.

abstractsObjective To analyze the correlation between treatment time and radiotherapy plan of deep inspiration breath-hold (DIBH) technique for the whole breast irradiation (WBI) in the left breast cancer after breast-conserving surgery,verify the inter-fractional reproducibility of radiotherapy,observe the heart location and dosimetric changes and calculate the effect of DIBH upon the WBI setup error after the surgery.Methods We prospectively enrolled 15 patients with left breast cancer undergoing WBI after breast-conserving surgery,who met the requirement of D1BH.Treatment time was recorded,its correlation with the number of field and monitor unit was analyzed.Inter-fractional setup errors and PTV delineation were calculated using cone beam CT (CBCT).The accuracy of the position and dose of the heart during radiotherapy was verified by the imaging fusion of CBCT and CT images.The variables among groups were analyzed by non-parametric Firedman test.Results The average treatment time of DIBH radiotherapy was 4.6 minutes.The treatment time was correlated with the maximal and total number of sub-fields and total monitor units.During DIBH treatment,the mean cardiac displacement volume was 19.1 cm3(3.8％).The mean cardiac dose difference between CBCT and planning CT was 5.1 cGy,and there was no significant difference in the heart V5-V30.The mean inter-fractional system setup error (∑) and random setup error (σ) in the left-right (x),superior-inferior (y) and anterior-posterior (z) direction were ∑x 1.9 mm,∑y 2.1 mm,∑z 2.0 mm,σx 1.3 mm,σy 1.3 mm,σz 1.4 mm,respectively.The corresponding minimal margins for setup error were 5.7 mm,6.2 mm and 6.0 mm,respectively.Conclusion DIBH for WBI after breast-conserving surgery does not significantly prolong the treatment time.Treatment time is related to treatment plan.DIBH yields high inter-fractional reproducibility and protects the heart.