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目的比较乳腺癌放疗中应用动态楔形板和物理楔形板对健侧乳腺和肺受量的影响。方法把实际治疗使用的计划加动态楔形板和物理楔形板分别计算13例患者,得出健侧乳腺(CB)、全肺和患侧肺的剂量分布。CB1和CB2是从内切野边缘算起两个长分别为4、10cm,内侧边界从皮肤表面标记铅丝至皮下3cm处的区域,用来代表健侧乳腺的受量情况。比较CB1和CB2所用指标为平均值,比较肺所用指标为患侧肺平均剂量及双肺V20。所用计划系统为CadPlan治疗计划系统。利用水模、电离室进行实际测量,并对比CadPlan和Eclipse计划系统的计算结果。结果在靶区覆盖率相同情况下,采用30°动态楔形板时,CB1和CB2的剂量百分比分别为1.5%～3.9%和1.1%～2.6%,患侧肺为4.1%～14.7%。采用30°物理楔形板时,CB1和CB2的剂量百分比分别为1.5%～4.4%和1.2%～3.0%,患侧肺为4.4%～15.2%。两种情况下全肺V20基本相同。采用15°动态楔形板时,CB1和CB2的剂量百分比也有所降低,但比30°楔形板时小得多;患侧肺的剂量百分比、全肺V20基本相同。实际测量结果说明采用动态板可以使正常组织受量降低。结论采用动态楔形板减少了健侧乳腺的剂量百分比,肺受量也有所减少或基本相同,从而可能使二次乳腺癌、放射性肺炎及肺纤维化等副作用的发生概率下降。
Objective To compare the effects of dynamic wedge plate and physical wedge plate on the contralateral breast and lung volume in radiotherapy of breast cancer. Methods According to the plan of actual treatment and the dynamic wedge plate and the physical wedge plate, 13 patients were calculated, and the dose distribution of the contralateral breast (CB), whole lung and ipsilateral lung was obtained. CB1 and CB2 are from the edge of the cut two long, respectively, 4,10 cm, the inner boundary from the skin surface marking the lead wire to 3cm subcutaneous area, used to represent the contralateral breast by the amount of the situation. Comparison of CB1 and CB2 indicators used for the average, compared with lung indicators used for the average ipsilateral lung dose and lung V20. The planning system used was the CadPlan treatment planning system. Actual measurements were made using a water phantom, ionization chamber and compared to the calculated results of the CadPlan and Eclipse planning systems. Results With 30% dynamic wedges, the percentages of CB1 and CB2 were 1.5% ~ 3.9% and 1.1% ~ 2.6%, respectively, while the ipsilateral lungs were 4.1% ~ 14.7% at the same target coverage. The dose percentage of CB1 and CB2 were 1.5% -4.4% and 1.2% -3.0% respectively in the 30 ° physical wedge plate and 4.4% -15.2% in the ipsilateral lung. V20 in both lungs is basically the same. With the 15 ° dynamic wedge, the dose percentage of CB1 and CB2 also decreased, but much less than the 30 ° wedge; the dose percentage of ipsilateral lungs was almost the same for whole lung V20. The actual measurement results show that the use of dynamic plate can reduce the amount of normal tissue. CONCLUSION: The dynamic wedge plate reduces the dose percentage of contralateral mammary gland and reduces or substantially reduces the amount of lung exposure, which may lead to the decrease of the incidence of secondary breast cancer, radiation pneumonitis and pulmonary fibrosis.