胸部肿瘤影像引导放疗剩余摆位误差分析

Analysis of Residual Set-up Errors for Imaging-guided Thoracic Tumor Radiation

目的量化分析胸部肿瘤影像引导放疗剩余摆位误差,为制定合理的临床靶体积(CTV)到计划靶体积(PTV)外放边界提供依据。方法收集2008年3月至2008年8月,在复旦大学附属肿瘤医院行根治性放疗的胸部肿瘤患者21例,1例患者自动退出,20例进入最终研究分析。每周行一次千伏锥形束CT(KVCBCT)引导分析。以2mm作为摆位误差是否在线校正的界值,分析在线校正前、后患者的摆位误差。结果 20例患者共获取225幅KVCBCT影像。采用KVCBCT引导放疗技术校正前,患者在前后(anterior posterior,AP)、上下(superior inferior,SI)和左右(left right,LR)三个方向上的摆位误差分别为:(-0.2±4.6)mm、(0.5±4.5)mm和(-0.8±4.4)mm。根据van等[5]提供的公式:2.5∑+0.7σ,CTV到PTV的预留边界应设定为12mm。采用KVCBCT在线引导放疗技术校正后,患者在LR、SI和AP三个方向上的剩余摆位误差分别为:(-0.2±1.3)mm、(0.1±1.3)mm和(0.3±1.3)mm,CTV到PTV的预留边界应设定为3mm。结论采用KVCBCT在线引导放疗技术可以减少患者摆位误差,提高治疗精确性、保证治疗质量。

Objective To assess the residual set-up error of the on-line kilovoltage cone-beam CT （KVCBCT） guided radiotherapy for thoracic tumor patients.Methods From Mar 2008 to Aug 2008,21 patients with pathologically confirmed thoracic tumor were included in this study.On-line imaging-guided set-up error correction was performed weekly for each patient.Set-up error,before and after correction,was documented.Results A total of 225 kVCBCT scans were obtained during 6 weeks.The initial average set-up error（x-±s） was（-0.2±4.6）mm,（0.5±4.5）mm and （-0.8±4.4）mm in the left-right （LR）,superior-inferior （SI） and anterior-posterior （AP） direction,respectively.After online correction,average residual set-up error （x-±s） was（-0.2±1.3）mm,（0.1±1.3）mm and （0.3±1.3）mm in the LR,SI and AP directions,respectively.According to the formalisms suggested by van Herk et al,3mm can be applied to the margin of clinical target volume （CTV） to planning target volume （PTV）,when using the on-line correction.Conclusion On-line KVCBCT guidance can improve the set-up accuracy of thoracic tumor patient＇s radiation.