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目的:利用4D锥形束CT研究肺癌放疗的靶区外扩范围。方法:随机选取2013年10月8日至2014年6月26日南京医科大学第一附属医院20例肺癌患者,热塑体膜固定,平静呼吸下CT螺旋扫描定位,治疗前利用4D锥形束CT进行靶区位置验证,根据公式MPTV=2.5Σ总+0.7σ总,分别计算只考虑摆位扩边、考虑摆位扩边和内扩边及考虑修正摆位扩边系统误差后3种情况下不同部位PTV在3个方向的外扩范围。结果:第1种情况只考虑摆位扩边,X方向4.185 mm,Y方向6.590 mm,Z方向4.117 mm。第2种情况考虑摆位扩边和内扩边,肺上叶组:X方向4.454 mm,Y方向7.108 mm,Z方向4.476 mm;肺中下叶组:X方向5.052 mm,Y方向13.511 mm,Z方向5.053 mm。第3种情况摆位扩边系统误差被修正,考虑内扩边,肺上叶组:X方向2.790 mm,Y方向4.797 mm,Z方向2.982 mm;肺中下叶组:X方向3.869 mm,Y方向12.809 mm,Z方向3.969 mm。结论:肺癌的PTV外扩范围必须考虑肿瘤运动,修正摆位扩边系统误差对肺上叶组肿瘤更有意义。
OBJECTIVE: To study the extent of target area radiotherapy for lung cancer using 4D cone beam computed tomography. METHODS: Twenty patients with lung cancer from the First Affiliated Hospital of Nanjing Medical University from October 8, 2013 to June 26, 2014 were enrolled in this study. They were fixed by CT and scanned by CT helical scanning under tranquilous breathing. Before treatment, CT to verify the location of the target area, respectively, according to the formula MPTV = 2.5Σ total + 0.7σ total, respectively, only consider the placement and expansion edge, consider the placement and extension and edge expansion, Under different parts of the PTV in 3 directions outside the expansion range. Results: In the first case, only the expansion and placement was considered. The X direction was 4.185 mm, the Y direction was 6.590 mm and the Z direction was 4.117 mm. In the second case, the placement of dilation and dilatation of the margin was considered. In the upper lobe group, the X-direction was 4.454 mm, the Y-direction was 7.108 mm, and the Z-direction was 4.476 mm. The middle and lower lobe group was 5.052 mm in X direction and 13.511 mm in Y direction, Z direction 5.053 mm. In the third case, the system error of setting the edge expanding system was corrected. In the upper lobe group, the upper lobe group was 2.790 mm in X direction, 4.797 mm in Y direction and 2.982 mm in Z direction. The middle and lower lobe group was 3.869 mm in X direction, Direction 12.809 mm, Z direction 3.969 mm. CONCLUSIONS: The movement of PTV in lung cancer must be considered in the range of tumor expansion. It is more meaningful to correct the error of setting and expanding system to the tumor of upper lobe group.