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目的:制作乳腺癌调强放疗计划时,采用分段逆向调强优化方法以达到更好的靶区剂量和保护肺、心脏等危及器官。方法:应用Eclipse8.6计划系统针对10例乳腺癌患者(肿瘤原发部位左右侧各5例)分别制定T1,T2模式调强放疗计划,处方剂量均为DT50Gy/25次。T1模式采用左乳300°、330°、0°、30°、60°、90°和120°方向射野,右乳60°、30°、0°、330°、300°、270°和240°方向射野,设置优化参数进行逆向优化和剂量运算。T2模式采用与T1模式相同的角度方向设野,第一段总剂量24Gy,分次剂量2Gy,分12次治疗,设置优化参数进行逆向优化和剂量运算;第二段总剂量26Gy,分次剂量2Gy,分13次照射,设置优化参数,采用“Base dose plan”功能选择基于第一段治疗计划以总量50Gy来逆向优化和剂量运算。将两段计划相加作为T2模式的治疗计划,通过剂量体积直方图比较两种模式下计划的靶体积和危及器官剂量分布。结果:T1、T2模式调强放疗计划的靶体积均满足临床剂量要求,对于左侧乳腺癌,适形指数分别为0.727±0.034、0.751±0.034(t=-6.20,P=0.003);对于右侧乳腺癌,适形指数分别为0.691±0.058、0.729±0.048(t=-5.39,P=0.006)。对左侧乳腺癌,T2模式的左肺V10(%)、左肺V20(%)、左肺V30(%)、全肺V10(%)、全肺V20(%)、全肺V30(%)和心脏V10(%)均大于T1模式,分别增大5.0%、2.7%、3.7%、4.6%、2.6%、3.8%和4.4%。对于右侧乳腺癌,无充分证据说明危及器官各指标有差别。结论:与T1模式相比,采用分段逆向调强优化方法能更好的优化靶区的剂量分布,但对左侧乳腺癌而言,会略微增加左肺、全肺和心脏剂量受量。
OBJECTIVE: To make a better target dose and to protect the lungs, heart and other organs from endangering organs in the preparation of IMRT plans for breast cancer. Methods: The plans of intensity-modulated radiation therapy of T1 and T2 mode were made respectively in 10 cases of breast cancer patients (5 cases on the left and right sides of the tumor) using Eclipse8.6 program system. The prescription dose was DT50Gy / 25 times. The T1 mode was based on left breasts at 300 °, 330 °, 0 °, 30 °, 60 °, 90 ° and 120 ° radiographs and 60 °, 30 °, 0 °, 330 °, 300 °, 270 ° and 240 ° ° direction field, set the optimization parameters for reverse optimization and dose calculation. The T2 mode uses the same angle as the T1 mode to set up a field, the first paragraph of the total dose of 24Gy, sub-dose 2Gy, divided into 12 treatments, set the optimization parameters for reverse optimization and dose calculation; the second paragraph of the total dose of 26Gy, 2Gy, in 13 exposures, set optimization parameters, use “Base dose plan” function selection based on the first treatment plan with a total of 50Gy to reverse optimization and dose calculation. The two-stage plan was added as a T2-based treatment plan, and the planned target volume and endangered organ dose distribution were compared by dose-volume histogram. Results: The target volume of T1 and T2 mode IMRT all met the clinical dose requirement. For the left breast cancer, the conformal indices were 0.727 ± 0.034 and 0.751 ± 0.034, respectively (t = -6.20, P = 0.003) Side breast cancer, conformal index were 0.691 ± 0.058,0.729 ± 0.048 (t = -5.39, P = 0.006). Left lung V10 (%), left lung V20 (%), whole lung V10 (%), whole lung V20 (%), whole lung V30 And heart V10 (%) were greater than the T1 mode, increased by 5.0%, 2.7%, 3.7%, 4.6%, 2.6%, 3.8% and 4.4%. For right breast cancer, there is insufficient evidence that there are differences between the indicators of organ damage. CONCLUSIONS: Compared with T1 mode, the use of piecewise reverse power optimization method can better optimize the target dose distribution, but left breast cancer, will slightly increase the left lung, whole lung and cardiac dose by the amount.