胸部肿瘤不同参考标记的摆位误差研究

目的：采用不同的解剖标记，定量的分析胸部肿瘤患者分次内器官移动和分次间放疗摆位误差，为胸部肿瘤调强放疗时计划靶区（planning target volume，PTV）和危及器官计划靶区（planning organ at risk volume，PRV）确定其外放边界。方法：拟行调强放疗的胸部肿瘤患者共11例，用电子射野影像装置（electronic portal imaging device，EPIDs）获取数字重建图像（digital reconstruction radiographs，DRRs），分别以胸椎、胸骨、肺尖、气管为解剖标记，分别计算出分次内和分次间摆位误差，并据此计算出危及器官和肿瘤临床靶区（clinic target volume，CTV）-PTV的外放边界。结果：胸部肿瘤的系统摆位误差（Σ-INTER）的平均标准差范围在L-R、A-P和C-C方向上范围分别为0.45~0.72、0.58~0.85和0.68~1.13 mm；器官移动的（Σ-intra）为0.27~0.42、0.39~0.48和0.37~0.58 mm。胸部肿瘤的随机摆位误差（δ-INTER）的平均标准差在L-R、A-P 和C-C 方向上范围分别为2.24~2.29、2.09~2.22和2.53~2.87 mm；器官移动的（δ-intra）为2.08~2.26、1.97~2.10和2.27~2.48 mm。据此计算出的CTV-PTV边界和PRV边界，以胸椎为准，在L-R、A-P和C-C方向上为3.68/2.53、3.60/2.48和4.93/3.38 mm；以胸骨为准，为3.47/2.40、3.72/2.55、5.00/3.42 mm；以肺尖为准，为3.65/2.52、3.73/2.56和4.45/3.05 mm；以气管为准，为3.34/2.31、3.98/2.72和4.03/2.78 mm。结论：采用不同的解剖标记对摆位误差进行纠正时，肿瘤CTV外扩的PTV边界和危及器官PRV，应采用不同的外边界，但总体而言，CTV外放5 mm， PRV外放3.5 mm基本上可以涵盖各个方向上由于摆位和呼吸动度引起的位移偏差。

The study of set-up errors for patients with thoracic tumors by different anatomical landmarks

Objective： Based on different anatomical landmarks for patients with thoracic tumors, the interfractional set-up errors and intrafractional organ motions were analyzed to define appropriate planning target volume（PTV）- and planning or-gans at risk volume（PRV）-margins in intensity-modulated radiotherapy（IMRT）. Methods： Eleven patients with thoracic tumors who were treated with IMRT were Enrolled. Digital reconstruction radiographs（DRRs） were generated as the reference image by electronic portal imaging device（EPID）. Based on the different anatomical landmarks as follows： vertebral column , pul-monary apices, the trachea, the interfractional set-up errors and intrafractional organ motions were calculated to find the de-fine appropriate PTV-and PRV-margins. Results： The standard deviations（SDs） of the systematic set-up errors（Σ-INTER） a-long left-right（L-R）, anterior-posterior（A-P） and cranial-caudal（C-C） direction ranged from 0.45-0.72, 0.58-0.85 and 0.68-1.13 mm respectively. The SDs of organ motions（Σ-intra） ranged from 0.27-0.42, 0.39-0.48 and 0.37-0.58 mm re-spectively. The SDs of the random set-up errors（δ-INTER） along left-right（L-R）, anterior-posterior（A-P） and cranial-caudal （C-C） direction ranged from 2.24-2.29, 2.09-2.22 and 2.53-2.87 mm respectively. The standard deviations （SDs） of organ motions（δ-intra） ranged from 2.08-2.26, 1.97-2.10 and 2.27-2.48 mm. Based on these data as above, appropriate PTV-margins and PRV-margins for vertebral column along left-right（L-R）, anterior-posterior（A-P） and cranial-caudal（C-C） were 3.68/2.53, 3.60/2.48 and 4.93/3.38 mm;3.47/2.40, 3.72/2.55, 5.00/3.42 mm;3.65/2.52, 3.73/2.56 and 4.45/3.05 mm for pulmonary apices;3.34/2.31, 3.98/2.72 and 4.03/2.78 mm for the trachea respectively. Conclusion： The set-up errors were corrected based on the different landmarks, a PTV-margin of 5 mm and a PRV-margin of 3.5 mm for thoracic IMRT were adopted at our department.