千伏级 CBCT 图像 CT 值校正及在放疗剂量计算中应用  

Investigation of CT numbers correction of kilo-voltage cone-beam CT images for accurate dose calculation

作　　者：王雪桃[1] 柏森[2] 李光俊[2] 蒋晓芹[2] 苏晨[1] 李衍龙 朱智慧[2] 

机构地区：[1]武汉大学物理科学与技术学院,430072 [2]四川大学华西医院肿瘤放射物理技术中心,成都610064

出　　处：《中华放射肿瘤学杂志》2015年第4期457-461,共5页Chinese Journal of Radiation Oncology

摘　　要：目的：研究千伏级CBCT图像CT值校正方法，提高其用于剂量计算的准确性。方法以扇形束计划 CT 作为先验信息，将 CBCT 与计划 CT 图像进行刚性配准，通过将 CBCT 与计划 CT 图像相减得到 CBCT 散射背景估计，对散射背景进行低通滤波处理，最后将原始 CBCT 图像减去滤波后的散射背景得到校正的 CBCT 图像。对 Catphan600模体和4例盆腔恶性肿瘤患者的 CBCT 图像进行校正，配对 t 检验校正前后 CBCT 与计划 CT 的差异，评估校正后的 CBCT 图像质量并分析用于剂量计算的准确性。结果经 CT 值校正后 CBCT 图像伪影明显减少，空气、脂肪、肌肉、股骨头的平均值校正前与计划 CT 分别相差232、89、29、66 HU，而校正后平均值差别缩小至5 HU 内（P＝0.39、0.66、0.59、1.00）。校正后 CBCT 图像用于剂量计算误差在2％内。结论校正后的 CBCT 图像 CT 值与计划 CT 的 CT 值相似，用于剂量计算可得到准确的结果。Objective To study CT numbers correction of kilo.voltage cone.beam CT （KV.CBCT） images for dose calculation. Method Aligning the CBCT images with plan CT images, then obtain the background scatter by subtracting CT images from CBCT images. The background scatter is then processed by low.pass filter. The final CBCT images are acquired by subtracting the background scatter from the raw CBCT. KV.CBCT images of Catphan600 phantom and four patients with pelvic tumors were obtained with the linac.integrated CBCT system. The CBCT images were modified to correct the CT numbers. Finally, compare HU numbers between corrected CBCT and planning CT by paired T test. Evaluate the image quality and accuracy of dose calculation of the modified CBCT images. Results The proposed method reduces the artifacts of CBCT images significantly. The differences of CT numbers were 232 HU, 89 HU, 29 HU and 66 HU for air, fat, muscle and femoral head between CT and CBCT respectively （P= 0. 39,0. 66,0. 59,1）.The differences of CT numbers between CT and CBCT was reduced to within 5 HU. And the error of dose calculation with corrected CBCT images was within 2%. Conclusions The CT numbers of corrected CBCT are similar with plan CT images and dose calculations based on the modified CBCT show good agreement with plan CT.

关 键 词：体层摄影术 X 线计算机 锥形束 CT 值校正 剂量计算 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]