Automated Classification of Intravenous Contrast Enhancement Phase of CT Scans Using Residual Networks.

Intravenous contrast enhancement phase information is important for computer-aided diagnosis of CT scans because the visual appearance of the scans varies substantially among the different phases. Although phase information could help to refine training data curation for downstream tasks, it is seldom included in the process of data augmentation for training a deep learning model. Unfortunately, in the current clinical settings, phase information is either unavailable or unreliable in most PACS systems. This motivates us to develop a method to automatically classify multiphase CT scans. In this study, a residual network (ResNet34) was utilized to classify five CT phases commonly used in the clinical environment: non-contrast, arterial, portal venous, nephrographic, and delayed contrast phases. A dataset of 395 multiphase CT scans was weakly labeled using keywords. The weakly-labeled dataset was split into 316 training, and 79 test CT scans. We compared the ResNet34 with two other popular classification models, VGG19 and DenseNet121. ResNet34 achieved the highest accuracy of 99%, while the accuracy of VGG19 and DenseNet121 were 97% and 95%, respectively. In addition, ResNet34 had fewer parameters to train in comparison with two other models, which could reduce the inference time to 35 seconds per scan and enhance generalizability of the model. High accuracy of multiphase classification suggests a potential way to improve data curation based on CT contrast enhancement phase. This would be useful to improve deep learning models by enhancing dataset curation and providing more realistic augmented data.