适应性统计迭代重建算法对肺部低剂量CT下计算机辅助检测系统的影响

Impact of adaptive statistical iterative reconstruction algorithm on computer-aided detection system using low-dose scanning in lung CT

目的探讨胸部低剂量CT扫描条件下不同适应性统计迭代重建(ASIR)水平对计算机辅助检测系统(CAD)检出小结节的影响。方法收集接受肺部低剂量CT筛查的60例受检者,平均体质量指数(25.00±2.22)kg/m2。应用自动管电流调节技术,设置噪声指数为30,管电压100kVp进行扫描;对图像采用5种ASIR水平(0%、30%、50%、80%和100%)进行重建。由3名放射科医师阅片,确定真性结节。应用Lung VCAR软件对5种ASIR水平图像的小结节进行检测,计算检出小结节的敏感度及假阳性数量。结果 60例受检者共检出非钙化结节212个,其中实性结节198个,部分实性结节6个,磨玻璃密度结节8个。5种ASIR水平下CAD检出结节的敏感度分别为73.03%、75.49%、75.91%、76.25%和84.41%。对于平均直径≤5mm的结节,0%ASIR和100%ASIR、30%ASIR和100%ASIR敏感度差异有统计学意义(P均<0.05)。5种ASIR水平下CAD检出小结节的假阳性分别为4.15、4.50、4.72、4.80、5.00个/扫描。扫描的有效剂量为(0.81±0.36)mSv。结论胸部低剂量CT中,CAD检出实性结节的敏感度及假阳性数量可达较满意水平;100%ASIR为CAD检出平均直径≤5mm小结节的最佳重建水平。

Objective To evaluate the effect of adaptive statistical iterative reconstruction（ASIR）levels on computer-aided detection（CAD）using low-dose CT.Methods Sixty subjects（body mass index[25.00±2.22]kg/m^2）were scanned using automatic current modulation with noise index of 30 and tube voltage of 100 kVp.Images were reconstructed with 5different ASIR levels（0%,30%,50%,80% and 100%）.CAD（Lung VCAR software）output was compared with the reference standard which established using consensus panel of three radiologists,and then the sensitivity and false-positive findings for each ASIR level were calculated.Results Totally 212non-calcified nodules（198solid,6partly solid and 8ground glass opacity）were found in the consensus panel.The sensitivity of CAD for different ASIR level was 73.03%,75.49%,75.91%,76.25%and 84.41%,respectively,and the sensitivity increased with increasing of ASIR level.Statistical difference of sensitivity could be found between 0% ASIR and 100% ASIR,30% ASIR and 100% ASIR for nodules diameter≤5mm（both P〈0.05）.The false-positive nodules of CAD for different ASIR levels were 4.15,4.50,4.72,4.80 and 5.00 per examination,respectively.The effective dose was 0.81 mSv.Conclusion The sensitivity and false-positive finding of CAD for detecting solid nodules using low-dose scanning in lung CT are satisfied,and 100% ASIR is the optimal level for CAD in detecting solid nodules with diameter≤5mm.