容积旋转调强放疗在老年食管癌根治性放疗中肺损伤的剂量学因素分析

Dosimetric analysis of radioactive injury lungs in elderly patients with esophageal cancer underwent volumetric modulated arc therapy

目的比较老年食管癌患者行根治性放疗应用容积旋转调强放疗(VMAT)与调强适形放疗(IMRT)两种计划的剂量学差异。方法应用Pinnacle V9.6计划系统分别对23例行根治性放疗的老年食管癌患者进行IMRT和VMAT两种计划设计,采用剂量体积直方图分析两种放疗技术的靶区剂量分布特点以及危及器官的受照射剂量和体积。结果IMRT和VMAT均能满足计划设计要求,VMAT适形指数优于IMRT(0.79±0.04 vs.0.69±0.05)(P<0.05),均匀指数略优于IMRT(0.24±0.05 vs.0.29±0.13)(P>0.05)。VMAT双肺V20、V30和肺平均剂量低于IMRT(P<0.05)。IMRT与VMAT脊髓最大耐受剂量以及心脏V30、V40差异均无统计学意义(P>0.05)。与IMRT相比,VMAT加速器跳数和治疗时间均减少[(345.50±25.95)MU vs.(574.10±128.74)MU和(431.80±109.06)s vs.(913.60±139.80)s](P<0.01)。结论VMAT能改善靶区剂量,减少双肺V20、V30和肺平均剂量,缩短治疗时间,提高治疗效率,从而降低老年食管癌患者放射性肺炎的发生。

Objective To compare the dose difference between volumetric modulated arc therapy(VMAT)and intensity modulated radiation therapy(IMRT)in radical radiotherapy for elderly patients with esophageal cancer.Methods Twenty-three elderly patients with esophageal cancer underwent radical radiotherapy received both IMRT and VMAT plans via Pinnacle V9.6 system.The distribution of target dose and the radiation dose and volume of organ at risk were analyzed by dose-volume histogram.Results Both IMRT and VMAT could meet the design requirements.The conformity index of VMAT was obviously better than that of IMRT(0.79±0.04 vs.0.69±0.05)(P<0.05)and the homogeneity index was slightly better than that of IMRT(0.24±0.05 vs.0.29±0.13)(P>0.05).The V20,V30 of lung and mean lung dose of VMAT were lower than those of IMRT(P<0.05).There was no statistical difference in the maximum tolerated dose of spinal cord and V30 and V40 of heart between IMRT and VMAT(P>0.05).Compared with IMRT,the monitor unit and curative time of VMAT were significantly decreased[(345.50±25.95)MU vs.(574.10±128.74)MU and(431.80±109.06)seconds vs.(913.60±139.80)seconds](P<0.01).Conclusion VMAT could effectively improve the target dose,decrease the V20,V30 of lung and mean lung dose,shorten the curative time,increase the therapeutic efficacy and reduce the occurrence of radiation pneumonia in elderly patients with esophageal cancer.