Detection Rate Of Pulmonary Subsolid Nodules With Different Thickness Of MIP And Comparison With CADe System

Objective: The objective of this study was to evaluate the detectability of pulmonary subsolid nodules on CT by using maximum intensity projection(MIP)with different thickness and compare with computer-aided detection(CADe)system.Methods: One hundred and two patients(49 men,53 women;mean age,57 years;age range,37-82 years)who underwent chest CT examinations and found small subsolid pulmonary nodules were retrospectively included.Two radiologists together evaluated each CT examination for the presence of subsolid pulmonary nodules using MIP with each image reconstructed using four different thicknesses(4,6,8,10 mm)and using 1mm thin axial CT scans.CADe system was used to detect small subsolid pulmonary nodules automatically.The reference standard of true small subsolid pulmonary nodules was determined in consensus by another two senior radiologists.Nodules' size,location were recorded.The chi-square test and matching chi-square test were used.Results: There were 314 true small subsolid pulmonary nodules determined by two senior radiologists.The number of true nodules,sensitivity and positive predictive value of 1mm axial scans,4mmMIP,6mmMIP,8mmMIP,10 mmMIP and CADe system were 219(69.7%,97.8%),204(65%,89.9%),217(69.1%,85.8%),247(78.7%,85.7%),194(61.8%,80.2%)and 300(95.5%,44.4%),respectively.Sensitivity for small subsolid pulmonary nodules was superior for 8mm MIP and was better than the sensitivities of other thickness MIP and 1mm axial scans,and the difference was statistically significant(P < 0.01 each).Sensitivity for small subsolid pulmonary nodules was superior for CADe system and was significantly better than the sensitivities of all other tested techniques,and the difference was statistically significant(P < 0.001 each).A total of 376 false positive nodules were labeled by CADe system and the average false positive was 3.7 / case(0-27).Conclusions: 8mm thickness MIP reconstruction image is superior to other thickness in detecting subsolid pulmonary nodules.The sensitivity of the CADe system to the detection of subsolid pulmonary nodules was improved and higher than that of the double reading method,but the false positive of the system was too high to be used independently.