千伏级锥形束CT图像对食管癌放疗剂量计算可行性研究

摘要

Objective To investigate the dose calculation accuracy and feasibility of using kilovoltage cone-beam CT (KVCBCT) for esophageal cancer radiotherapy.Methods Hounsfield unit (HU) values and profile along the horizontal line of Catphan (R) 600 phantom in KVCBCT images acquired on Trilogy linear accelerator were compared to those in the planning CT.The KVCBCT value-density calibration curve was established.The intensity modulated radiotherapy plans were created on the planning CT images and copied to KVCBCT images.The dose distribution was recalculated by means of the KVCBCT value-density calibration curve in the treatment planning system.The dosimetric comparisons were performed between the KVCBCT and planning CT plans on the phantom and 10 patients with esophageal cancer.Results The KVCBCT value was stable with a maximum variation of 1.6％,and there was no significant time trend.CT value profiles showed good agreement within 1％ variation except the peripheral regions.The dosimetric differences were less than 1.33％ and 3.65％ for the phantom case and the patient ones,respectively.The dose distribution comparison was also in good agreements.Conclusions The accurate dose caleulation based on KVCBCT for esophageal cancer is feasible.The KVCBCT images can be used for monitoring the dosimetric changes during the treatment.%目的 探讨千伏级锥形束CT图像(KVCBCT)对食管癌放疗剂量计算的可行性.方法 比较Trilogy加速器采集的Catphan(R)600模体KVCBCT图像CT值稳定性及离轴曲线重合度并建立CT值-密度转换曲线用于剂量计算.在模体和10例食管癌患者常规CT上设计逆向调强计划,并将计划移植到相对应的KVCBCT图像上.基于KVCBCT的转换曲线计算靶区及周围组织受量,并与常规CT计算结果行配对t检验.结果 KVCBCT的CT值变化范围均在 1.6％内,且未发现有随时间变化趋势.常规CT和KVCBCT的CT值离轴曲线重合度较高,大部分成像区域差别在1％内.模体调强计划常规CT与KVCBCT所得剂量统计参数最大差别为1.33％,对食管癌患者凋强计划两者剂量差别在3.65％内.等中心层面剂量分布有较好一致性.结论 使用食管癌KVCBCT图像进行剂量计算是准确可行的,在临床上具有实际应用意义.