Solitary Pulmonary Nodule on Helical Dynamic CT Scans: Analysis of the Enhancement Patterns Using a Computer-Aided Diagnosis (CAD) System

Analysis of the Enhancement Patterns Using a Computer-Aided Diagnosis (CAD) SystemObjective: We wanted to investigate the usefulness of a computer-aided diagnosis (CAD) system in assisting radiologists to diagnosis malignant solitary pulmonary nodules (SPNs), as compared with diagnosing SPNs with using direct personal drawing. Materials and Methods:Forty patients with SPNs were analyzed.After the pre-contrast scan was performed, an additional ten series of post-contrast images were obtained at 20-second intervals.Two investigators measured the attenuation values of the SPNs: a radiologist who drew the regions of interest (ROIs), and a technician who used a CAD system.The Bland and Altman plots were used to compare the net enhancement between a CAD system and direct personal drawing.The diagnostic characteristics of the malignant SPNs were calculated by considering the CAD and direct personal drawing and with using Fisher's exact test.Results: On the Bland and Altman plot, the net enhancement difference between the CAD system and direct personal drawing was not significant (within ± 2 standard deriation).The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of diagnosing malignant SPNs using CAD was 92%, 85%, 75%, 96% and 88%, respectively.The sensitivity, specificity, PPV, NPV and accuracy of diagnosing malignant SPNs using direct drawing was 92%, 89%, 79%, 92% and 88%, respectively.Conclusion: The CAD system was a useful tool for diagnosing malignant SPNs.olitary pulmonary nodules (SPNs) are a major concern not only for radiologists, but also for clinicians because 30-80% of resected SPNs are found to be malignant (1-6).The role of the radiologist for evaluating SPNs is to accurately distinguish between benign and malignant lesions.In general, CT has high specificity and acceptable sensitivity and accuracy, and it might be a reasonable modality for characterizing nodules (1-11).Malignant nodules tend to enhance substantially more than benign nodules even though some overlap, such as for active granulomas or benign vascular tumors, has been found (2,4,5,7,(12)(13)(14).More recently, several authors have attempted to assess the washout characteristics of SPNs on contrast-enhanced CT, which is also known as helical dynamic CT (HDCT) (10, 15-17).Jeong et al. (15) evaluated solitary pulmonary nodules by analyzing the combined wash-in and washout characteristics of dynamic contrast-enhanced multi-detector row CT, and they reported 92% accuracy for distinguishing between benign and malignant nodules.However, a diagnosis of SPNs using HDCT is a difficult task for human readers