Analysis of Position Verifi cation Result of Intensity Modulated Radiotherapy in Thoracic Tumors by Simulator
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摘要: 目的 统计胸部肿瘤调强放射治疗时，利用模拟机测量的左右(X)、前后(Y)、头脚(Z)方向的摆位误差值。方法 190例行调强放射治疗的胸部肿瘤患者行体位验证，其中男150例，女40例；153例患者验证1次，37例患者验证2次。应用真空垫固定体位，行增强CT扫描，生成0度、45度、90 度射束方向数字重建图像，与模拟机采集的射束方向图配准，测量X、Y、Z方向摆位误差。统计分析摆位误差值，计算胸部肿瘤内靶区（internal target volume，ITV）生成计划靶区（planning target volume,PTV）需外放边界。结果 所有患者在X、Y、Z方向摆位误差分别为（1.3±1.8）mm、（1.3± 1.9）mm、（1.7±2.3）mm，在X、Y、Z方向的最大摆位误差分别为7 mm、7 mm、8mm。根据测量结果胸部肿瘤由ITV生成PTV在X、Y、Z方向上外放边界分别需要3.9 mm、3.9 mm、5.0mm。男女患者在X、Y、Z方向摆位误差分别为（1.2±1.8）mm和（1.6±1.9）mm（P=0.18）、（1.3±1.8）mm和（1.4±2.0）mm（P=0.50）、（1.6±2.2）mm和（1.9±2.5 ）mm（P=0.81）。结论 根据上述模拟机下体位验证数据，可以为ITV生成PTV外放边界提供依据。模拟机下体位验证同时可以观察呼吸活动对靶区的影响，为由GTV生成ITV提供参考依据。Abstract: Objective To evaluate set-up errors at the directions of right-left(X), anterior-posterior(Y) and superior-inferior(Z) of thoracic tumors treated with intensity modulated radiotherapy(IMRT) by simulator. Methods One hundred and ninety patients with thoracic tumors, 150 males and 40 females, were treated with IMRT in the prone position and verifi ed with simulator. Position verifi cation was performed once in 153 patients and twice in 37 patients. Patients were detected by enhanced computer tomography after vacuum pad fi xing. Then Digital reconstructed radiographies (DRR) of 0, 45 and 90 degree were generated. DRR of each patient was compared with portal images and set-up errors were recorded and analyzed. The shift margin from internal target volume(ITV) to planning target volume(PTV) was calculated according to set-up error data analysis. Results The mean and standard deviations of set-up errors of all patients at the directions of right-left (X), anterior-posterior (Y) and superior-inferior (Z) were (1.3±1.8)mm, (1.3±1.9)mm and (1.7± 2.3)mm, respectively. The maximum set-up error at the directions of X, Y and Z was 7mm, 7mm and 8mm respectively. And the margins from ITV to PTV were 3.9mm, 3.9mm and 5.0mm, respectively. The mean and standard deviation of set-up errors of male and female patients at X, Y and Z directions were (1.2±1.8)mm vs. (1.6±1.9)mm(P=0.18), (1.3±1.8)mm vs. (1.4±2.0)mm(P=0.50) and (1.6±2.2)mm vs.( 1.9±2.5)mm(P=0.81), respectively. Conclusion It was recommended that shift margin from ITV to PTV should be calculated according to set-up error data. The effects of respiratory activities on the target area could be observed under posture validation at simulator, which provided reference during GTV to generate ITV.
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Key words:
- Thoracic tumor /
- Intensity modulated radiotherapy(IMRT) /
- Set-up error
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