基于锥形束CT的头颈部肿瘤在线与离线结合图像引导放疗的研究  

Study of image-guided radiotherapy for head and neck cancer based on on-line and off-line CBCT setup verification

作　　者：李洪升[1] 李宝生[1] 孙涛[1] 尹勇[1] 李需[1] 余宁莎[1] 

机构地区：[1]山东省肿瘤防治研究院放疗科,山东济南250117

出　　处：《中华放射医学与防护杂志》2009年第3期280-283,共4页Chinese Journal of Radiological Medicine and Protection

基　　金：国家自然科学基金（30670617）

摘　　要：目的分析锥形束CT（CBCT）在线摆位校正与离线自适应校正在减小头颈部肿瘤临床靶区（CTV）外放，从而减轻正常组织并发症中的作用。方法16例行三维适形放疗的头颈部癌症患者人组。分次放疗前后均行在线CBCT扫描1次，并与计划CT图像配准，记录各个方向的配准差值。放疗前后的配准差值分别作为放疗分次间误差和分次内误差，用于计算每例患者的系统误差和随机误差。利用CTV外放计算公式，计算在线校正前后CTV外放；以0.5mm为允许的最大残余系统误差，计算离线校正系统摆位误差后CTV外放。结果未经在线校正，左右、头脚和前后方向上群体化CTV外放分别为5.7mm、5.6mm和7.3mm；每分次放疗均行在线校正，3个方向上群体化CTV外放分别为1.7mm、1.7mm和2.3mm；对系统摆位误差进行离线自适应校正，3个方向上群体化CTV外放分别为2.7mm、2.5mm和3.6mm。结论基于CBCT图像分析的在线校正和离线自适应校正均能明显减小摆位误差，有助于缩小CTV外放，并有望减轻正常组织并发症。Objective To investigate how much the patient setup accuracy for irradiation of head and neck cancer can be improved by online setup verification and offline setup verification using cone-beam computed tomography（CBCT）, and the feasibility of image-guided adaptive correction procedure to reduce the PTV margin. Methods 16 patients of head-and-neck cancer treated with three-dimensional conformal radiotherapy （3D- CRT）or intensity modulated radiotherapy（IMRT）were investigated. The first online kV CBCT scan, rigid image registration, setup correction were performed before radiotherapy. The second kV CBCT scan were acquired immediately after treatment and analysis was performed as above. CBCT scans were acquired at two or three fractions weekly during the entire course of radiotherapy and CBCT online-guided correction data were recorded. The data was used to calculate the population-based CTV-PTV margins under the condition of non-correction, correction every fraction and compensation of the systematic setup error respectively. The number of initial images required to predict systematic setup error was evaluated with the permission of 0.5 mm residue error. Results Total of 320 sets of CBCT images were analyzed for 16 patients. Under the condition of non-correction, the margins required to account for total error are 5.7mm,5.6 mm,aud 7.3 mm in the left-right（X axis）,cranio- caudal（Y axis）, and anterior-posterior （Z axis）directions respectively, when the tumor was corrected every fraction, the margins required to account for intrafraction error are 1.7mm, 1.7mm, and 2.3 mm in X, Y, and Z axis. To correct the systematic setup error,8 sets of CBCT images are adequate. After compensation for the effect of the systematic setup error, 2.7 mm,2.5 mm,and 3.6 mm PTV margins are necessary in X, Y,and Z axis respectively. Conclusions There exists some extent of setup error in head and neck 3D-CRT or IMRT.The on- line CBCT correction and the approach based on off-line adaptive correction both can be used to

关 键 词：头颈部肿瘤 计划靶体积 自适应放疗 图像引导放疗 锥形束CT 

分 类 号：R730.55[医药卫生—肿瘤] R739.91[医药卫生—临床医学]