应用CTVision图像引导分析胸部肿瘤在放疗中的摆位误差

Analysis of Set-up Errors with Use of CTVision Imaging Guided Thoracic Tumor Radiation

目的应用西门子CTVision图像引导分析校正胸部肿瘤在放疗中的摆位误差,为制定胸部肿瘤放疗计划时从临床靶区(CTV)到计划靶区(PTV)的外扩边界提供参考。方法选取我科2011年1～9月应用西门子ONCOR直线加速器行根治性放疗的胸部恶性肿瘤患者20例,每周行CTVision图像引导放射治疗分析1次,对摆位误差超过3 mm的患者进行在线校正,分析患者校正前和校正后的摆位误差。结果 20例患者共获得三维方向上校正前后的摆位误差数据194组。校正前患者在前后(Anterior Posterior,AP)、上下(Superior Inferior,SI)和左右(Left Right,LR)3个方向上的摆位误差分别是:(-0.57±1.28)mm、(-0.81±4.39)mm、(0.94±1.25)mm,校正后AP、SI、LR 3个方向的摆位误差值分别为:(-0.24±0.40)mm、(0.31±1.29)mm、(-0.02±0.41)mm,采用Van等人的摆位外扩边界(MPTV)推理公式MPTV=2.5∑+0.7δ计算,校正前CTV到PTV需外扩MPTV值应为11 mm,校正后为3 mm。结论采用CTVision图像引导系统在线引导放疗技术,可以有效地减少患者在治疗实施过程的误差,提高治疗精度。

Objective To analyze the change of set-up errors with the use of CTVision guided radiotherapy for thoracic patients. The results can be used to determine the margin from clinical target volume （CTV） to planning target volume （PTV） in treatment planning. Methods From January 2011 to September 2011, 20 patients with thoracic tumor were included in this study. Online imaging guided set-up error correction was performed weekly for each patient, set-up error, before and after correction, was analyzed. Results A total of 194-group data was acquired before and after correction during 6 weeks. Before correction, the set-up errors in anterior posterior, superior inferior, left right were（-0.57±1.28） mm, （-0.81±4.39） mm, （0.94±1.25） mm, separately, and the set-up errors, after correction were （-0.24±0.40） mm, （0.31±1.2,9） mm, （-0.02±0.41） ram, separately. According to the van Herk formula Mpaw =2.5∑＋0.7δ, the MPTV should be llmm before correction, and 3mm after correction. Conclusion CTVision guidance can improve the set-up accuracy of thoracic tumor patient＇s radiation.