食管癌螺旋断层放疗及三维适形调强放疗计划剂量学研究

Dosimetric comparison between helical tomotherapy and intensity-modulated radiotherapy for esophageal carcinoma

目的近年来放射治疗设备不断更新,放疗技术持续发展,肿瘤放疗方式有了更多的选择。本研究通过评估食管癌的螺旋断层放疗(tomotherapy,TOMO)及三维适形调强放疗(intensity modulation radiation therapy,IMRT)的剂量学特性,为临床上食管癌放疗方式的选择提供依据。方法选取2014-07-13-2015-02-25浙江省肿瘤医院胸部肿瘤放疗科10例食管癌患者,勾画靶区及正常器官后,分别传输至Raystation及TOMO计划系统,给予肿瘤原发灶(PGTV)61.6Gy/28次,计划靶区(PTV)56.0Gy/28次,根据RTOG 1106标准限制危及器官(organs at risk,OAR)剂量。分别对靶区的剂量体积直方图(dose volume histogram,DVH)、均匀性指数(homogeneity index,HI)、适形性指数(conformal index CI)和OAR(肺、心脏、脊髓)受照最大剂量及平均剂量进行评估。结果两种计划都能满足处方剂量要求和危及器官受量限制。TOMO计划中PGTV的中位均匀性指数(HI)为0.057 5,优于IMRT计划的0.073 5,P=0.047。TOMO计划中PTV的中位适形性指数(CI)为0.785,优于IMRT计划的0.682 5,P=0.009。TOMO计划中PGTV的中位最大剂量Dmax为64.9Gy,明显低于IMRT计划的66.5Gy,P=0.005;TOMO计划中PTV的中位最大剂量Dmax为64.1Gy,明显低于IMRT计划的64.9Gy,P=0.028。TOMO计划的中位总的肺剂量为10.8Gy,低于IMRT计划的11.9Gy,P=0.005。TOMO计划的中位总的心脏剂量为22.6Gy,明显低于IMRT计划的24.3Gy,P=0.028。TOMO计划的中位脊髓最大剂量为40.2Gy,明显低于IMRT计划的41.7Gy,P=0.007。结论食管癌放疗中TOMO放疗计划对比IMRT放疗计划,具有更好的靶区覆盖适形性及剂量分布均匀性,同时明显减少双肺、心脏及脊髓的受照剂量。

OBJECTIVE With the constantly development of the equipment and technology,the methods for tumor radiotherapy became diversify.The aims of this study were to compare the effectiveness of different radiotherapy techniques-tomotherapy（TOMO）and intensity-modulated radiation therapy（IMRT）for patients with esophageal carcinoma（EC）on the basis of dosimetric analysis.METHODS A retrospective dosimetric study was performed in 10 patients with esophageal cancer.The target areas and organs at risk（OAR）were underlined and transmitted to the Raystation and TOMO planning system.A dose of 61.6Gy given in 28 fractions was delivered to the planning gross tumor volume（PGTV）,while dose for planning target volume（PTV）was 56.0Gy/28 F.The doses to the organs at risk（OAR）were districted according to the RTOG1106.Tomotherapy plans and IMRT plans were created for each of the patients.The dose-volume histograms（DVHs）,homogeneity index（HI）and conformal index（CI）values,mean dose and volumes of lung receiving more than 5,10,20,30,40 and 50Gy（V5,V10,V20,V30,V40,V50）,mean dose and volumes of heart receiving more than 20,30,40,50 and 60Gy（V20,V30,V40,V50,V60）and maximum dose of spinal cord were determined for each treatment scheme.RESULTS The two plans could meet the standards of prescribed doses and the limit of acceptable doses for the OAR.The median of HI of gross PTV by tomotherapy（HI=0.057 5）indicated improved conformity and superior homogeneity dose distribution compared to IMRT technique（HI=0.073 5,P=0.047）.The median of CI of PTV by tomotherapy（CI=0.785）indicated improved conformity dose distribution compared to IMRT technique（CI=0.682 5,P=0.009）.The median of maximum dose to gross PTV by tomotherapy（Dmax=64.9Gy）was significantly decreased compared to plans by IMRT（Dmax=66.5Gy,P =0.005）.The median of maximum dose to PTV by tomotherapy（Dmax=64.1Gy）was significantly decreased compared to plans by IMRT（Dmax=66.5Gy,P=0.005）.The median of total lung doses was significantly reduced by tomotherapy（10.8Gy）compared to IMRT（11.9Gy,P=0.005）.The median of total heart doses was significantly reduced by tomotherapy tomotherapy（22.6 Gy）compared to IMRT（24.3Gy,P=0.028）.The median of maximum doses to spinal cord was also significantly reduced by tomotherapy（40.2Gy）when compared to IMRT plans（41.7Gy,P=0.007）.CONCLUSIONS Compared to IMRT,tomotherapy could provide better conformal target coverage and more homogeneity dose distribution.Tomotherapy also significantly decreases the radiation dose to the lungs,heart and spinal cord when compared to IMRT.