CT肺功能成像技术研究

目的探讨CT肺功能成像技术的可行性,着重研究CT肺功能参数与肺功能检查(pulmonary functional test, PFT)参数的相关性.方法共69例,包括PFT正常者21例,阻塞性通气功能障碍者37例,限制性通气功能障碍者9例,混合性功能障碍者2例,均在1周内完成PFT和胸部CT检查.采用最大吸气末和呼气末屏气螺旋CT扫描.扫描参数120 kV,175 mA,每层螺旋扫描时间1 s,床速20 mm/s,螺距2∶1.将CT图像经医学数字影像与通讯(DICOM)协议接口接到计算机上.利用自行研制的CT肺功能定量软件进行数据分析.结果通过吸气末CT测得的肺体积(Vin)与PFT的最大肺总量(TLC)存在明显相关性(r=0.866,P<0.001),呼气末CT测得的肺体积(Vex)与残气量(RV)有相关性 (r=0.833,P<0.001),呼吸比(Vex/Vin)与RV/TLC有相关性(r=0.590,P<0.001).吸气像平均CT值与第1秒量占预计值的百分比(FEV1%),第1秒用力呼吸量(FEV1)/用力肺活量(FVC)存在相关性(r=0.382, P<0.05 ; r=0.682, P<0.01).像素指数(PI)=-910～-950 HU与FEV1、FEV1%、 FVC%、FEV1/FVC均存在相关性,其中与FEV1/FVC的相关性最好(r=0.747～0.772,P<0.01).呼气像平均CT值与FEV1、FEV1%、FVC%、FEV1/FVC存在相关性(r=0.624, P<0.01; r=0.654, P<0.01; r=0.452, P<0.01 ; r=0.758, P<0.01).呼气像CT各阈值与PFT参数均存在相关性.结论最大吸气末和最大呼气末行螺旋CT扫描,可获得肺部解剖和肺功能情况的参数,与PFT结果相关性好,因此本法是行之有效的CT肺功能定量成像技术.

The study of CT pulmonary functional imaging technique

Objective To evaluate the feasibility of CT pulmonary function imaging with emphasis on the results of the correlation between CT functional imaging parameters and that of pulmonary functional tests. Methods The study population was 69 cases. According to the results of pulmonary functional tests (PFT), 21 persons with normal lung function, 37 patients with obstructive lung function abnormality, 9 with restrictive lung function abnormality, and 2 with mixed lung function abnormality were included. The CT scanning and pulmonary function tests were performed within one week for all of the cases. Spiral CT scans were obtained during breath hold at full inspiration and full expiration from the lung bases to the lung apices. The scanning parameters were as fellows: 120 kV, 175 mA, one revolution per second; 10 mm slice thickness; 20 mm/s table speed (pitch 2). The images were reconstructed by 10 mm slice thickness and standard algorithm, and then were archived and transferred digitally to personal computer for analysis. A CT pulmonary functional quantitative software designed by the authors was used to analysis all images. Results Using full inspiratory and expiratory spiral CT, total lung capacity (Vin) and residual capacity (Vex) were revealed, which had a good correlation with results obtained by pulmonary function tests (r=0.866, P<0.001; r=0.833, P<0.001). Vex/Vin showed correlation with RV/TLC (r=0.590, P<0.001). The mean lung CT value obtained at full inspiratory phase showed correlation with FEV1%, FEV1/FVC (r=0.382, P<0.05 ; r=0.682, P<0.01 ). PI=-910--950 HU were found to correlate with FEV1, FEV1%, FVC%, FEV1/FVC, especially to have good correlation with FEV1/FVC (r=0.747-0.772, P<0.01). The mean lung CT value obtained at full expiratory phase also showed correlation with FEV1, FEV1%, FVC%, FEV1/FVC (r=0.624, P<0.01; r=0.654, P<0.01; r=0.452, P<0.01; r=0.758, P<0.01). Several pixel index (PI) at expiratory also were detected to correlate with pulmonary function test parameters. Conclusion Spiral CT scanning at full inspiratory and expiratory phase can provide pulmonary functional as well as anatomic information. The new imaging technique, therefore, is an effective method for quantitative pulmonary function study.