探讨能谱CT单能量图像对计算机辅助检测系统肺栓塞检出率的影响

Influence of mono-energetic images of spectral CT on the detection rate in computer-aided detection system for pulmonary embolism

目的:探讨不同水平单能量图像对计算机辅助检测系统(CAD)检出肺栓塞准确率的影响。方法:20例确诊为肺栓塞的患者均行能谱扫描模式CT肺动脉成像(CTPA)。重建40、45、50、55、60、65、70、75和80 keV共9组单能量图像,然后应用CAD软件分别对各组单能量图进行分析。由两位有经验的放射科医师分析所有图像并标记出栓子,记录数量和部位,以两位医师的诊断结果作为金标准,计算各单能量图像结合CAD对栓子的检出率和假阳性率。结果:两位医师共检出120个栓子。在40~80 keV的各组单能量图像上CAD对栓子的检出检出率和假阳性率分别为40.00%和0%、54.17%和2.99%、51.17%和1.59%、68.33%和5.75%、81.67%和7.55%、84.17%和12.17%、80.00%和30.77%、82.50%和36.94%、85.38%和54.42%。低keV(<60 keV)单能量水平CAD检出栓子的敏感度较低;高keV(>65 keV)单能量水平假阳性率较高。在60和65 keV单能量水平时的敏感度相对较高且假阳性率相对较低。结论:能谱CT不同水平单能量图像与CAD结合能够影响栓子检出的准确性,在60~65 keV单能量图像上CAD对栓子检出的敏感性较高且假阳性较低。

Objective:To evaluate the influence of mono-energetic images at different energy levels of spectral CT on the detection rate of computer aided detection(CAD)system for pulmonary embolism(PE).Methods:20 patients with PE confirmed by clinics underwent CT pulmonary angiography(CTPA)under spectral scan mode.Nine sets of mono-chromatic images at 40,45,50,55,60,65,70,75 and 80keV energy levels were reconstructed and analyzed for detecting PE using a commercially available CAD software.Two experienced radiologists reviewed all images and recorded the number and locations of the emboli they found,which was used as the reference standard.The CAD findings for the number of emboli at different photon energies were compared with the reference standard to determine the true positive and false positive number and to calculate the sensitivity and false positive rate of different energy levels.Results:There were 120 emboli found by the two experienced radiologists.The sensitivity(detection rate)and false positive rate of CAD at 40,45,50,55,60,65,70,75 and 80keV were 40%and 0%,54.17%and 2.99%,51.17%and 1.59%,68.33%and 5.75%,81.67%and 7.55%,84.17%and 12.17%,80.00%and 30.77%,82.5%and 36.94%,85.38%and 54.42%,respectively.CAD system was lower in sensitivities based on the images at low energy levels(<60keV)and higher false positive rates at high energy levels(>65keV).At 60 and 65keV,the sensitivity was relatively high and false positive rate was relatively low.Conclusion:Mono-chromatic images of different energy levels in dual-energy spectral CT affect the accuracy of CAD detection system for PE.The combination of CAD system with images at 60~65keV provides high sensitivity and low false positive rate in the detection of pulmonary embolism.