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目的探究摆位系统误差对乳腺癌患者实施调强放射治疗的剂量学影响。方法 2012年10月对一典型乳腺癌改良根治术后患者分别设计常规三维适形切线野(CRT)、多野静态调强(s-IMRT)、旋转调强(VMAT)3种不同治疗技术的计划,在计划中将治疗中心点向患者左、右、腹、背、头、脚方向分别平移3、6 mm模拟2种不同程度的系统误差,共计39个计划与原计划进行比较,观察不同治疗技术间、不同平移距离,不同方向上的靶区及主要危及器官患侧肺和心脏的剂量变化。结果对于3 mm摆位系统误差,靶区D95%于向背侧s-IMRT降低4.0%,VMAT降低3.5%,向右(患侧)s-IMRT降低3.0%,VMAT降低2.8%,其余均方向降低且<1.6%。对于主要危及器官,系统误差对s-IMRT技术的患侧肺接受20 Gy剂量的体积影响大,对VMAT技术的患侧肺接受10 Gy剂量的体积影响大。除此外,对主要危及器官患侧肺及其他剂量参数影响均小(3 mm<3%,6 mm<6%)。系统误差对3D-CRT技术的影响小(3 mm<3%,6 mm<6%)。6 mm的系统误差对靶区及危及器官的影响与3 mm趋势一致,仅变化程度更大,两种调强技术的靶区D95%降低>5%。结论对乳腺癌改良根治术后的呈弧段状、位于胸廓表面的放射治疗靶区,s-IMRT和VMAT方式的调强治疗技术对治疗摆位系统误差的影响程度相当,但较CRT技术更敏感,其中以向患者背侧、健侧方向偏移影响最大。改良根治术后乳腺癌调强治疗的实施需要有较三维治疗更高的位置精度保证。
Objective To investigate the dosimetric effects of setting system errors on intensity modulated radiation therapy in patients with breast cancer. Methods In October 2012, we planned to design three kinds of three-dimensional conformal tangent field (CRT), multi-field static intensity-adjusting (s-IMRT) and rotational tonometry (VMAT) In the plan, the center of treatment was shifted to the left, right, abdomen, back, head and foot by 3,6 mm respectively to simulate two kinds of systematic errors of different degrees. A total of 39 plans were compared with the original plans to observe different treatments Technology, different translational distances, target areas in different directions, and changes in the dose of the lungs and heart that predominantly affect the affected organs. Results For 3 mm positioning system error, target D95% decreased s-IMRT to the dorsal side by 4.0%, VMAT decreased by 3.5%, right (ipsilateral) s-IMRT decreased by 3.0% and VMAT decreased by 2.8% And <1.6%. Systematic errors have a large impact on the volume of the i-lung affected by s-IMRT in the 20 Gy dose and the volume affected by the 10 Gy dose in the affected lung of the VMAT technique. In addition, there was little effect on the affected lungs and other dose parameters (3 mm <3%, 6 mm <6%). System error has little effect on 3D-CRT technology (3 mm <3%, 6 mm <6%). The systematic error of 6 mm has the same tendency as the 3 mm trend but only a greater degree of change in the target area and the organ endangered organ. The target area D95% of the two intensity modulation techniques is reduced by> 5%. CONCLUSIONS: The modified technique of s-IMRT and VMAT has the same effect on the system error of positioning but is more effective than the CRT technique in the treatment of breast cancer after radical mastectomy. Sensitive, which to the patient’s dorsal, contralateral direction offset the most affected. Modified radical mastectomy breast cancer treatment needs more than three-dimensional treatment of higher position accuracy assurance.