应用Alderson Rando人形体模探讨肺肿瘤位置和体积对正常肺组织剂量学参数影响

Study of effect of lung tumor location and volume on dosimetric parameters using Alderson Rando phantom

目的探讨肺肿瘤位置、体积对正常肺组织剂量体积参数的影响。方法将采用组织等效材料制作的模拟球形病灶分别嵌入AldersonRando人形体模右肺3个叶和左肺下、上叶，采用6MVX线对上述各种情况进行5个野简化调强放疗计划设计，处方剂量为60Gy（2Gy／次共30次）。所有计划都使99％靶区体积达到处方剂量要求。分析正常肺组织接受不同剂量照射的体积百分比（V5、V10、V20、V30、V50）和平均肺剂量。结果就正常肺组织的各个剂量体积参数而言，不同病灶位置和直径的差异多数是不同的，两种因素对各个参数的变化有不同程度的影响。各个参数随球形病灶直径的增大而增大（P〈0．05）。当病灶直径从2cm增至3cm、病灶位于不同位置时，各参数增幅在3．83％-125．38％范围内；当病灶直径从3cm增至4cm、病灶位于不同位置时，各参数增幅在10．46％～51．46％范围内。结论肺肿瘤位置和直径变化对正常肺组织剂量体积参数多数有不同程度影响，但如何提高预测准确性尚待基础和临床实验的进一步研究。

Objective To study the effect of the location and volume of tumors on the normal lung dose-volume parameters for lung cancer. Methods An sphere with a diameter of 2 cm made of tissue-equiv- alent material used for simulating tumor was inserted into the superior lobe, middle lobe, inferior lobe of the right lung, and superior lobe, inferior lobe of the left lung of the Rando phantom, respectively. 5-field slM- RT plans were designed. The prescribed dose was 60 Gy/2 Gy/30 f, and 99% of the planning target volume received this dose. Dose-volume parameters of normal lung tissue including V5 , V10, V20, V30, V50 and mean lung dose were analyzed and compared. Results For the dose-volume parameters, the diameter and the position of the tumor have a significant effect （ P 〈 0.05 ）. With the diameter expanding from 2 cm to 3 cm, the parameters associated with tumor in various lobes increased by a range between 3.83% - 125.38%, while the parameters linked with tumor in different lobes increased by a range between 10.46% -51.46% with the diameter expanding from 3 cm to 4 cm. Conclusions Location and diameter of sphere-like tumor have obvious effect on dose-volume parameters. Knowing about the degree of influence will help oncologists and physicists to evaluate treatment planning better and reduce radiation pneumonitis.