Fig. 5

Heatmaps for cardiac pathology assessment on T1 mapping images. A, B: Subject without cardiac pathology in the sagittal plane with short axis view. A shows the T1 mapping image. In B, the image was overlaid with a gradient-weighted class activation map (Grad-CAM), generating a heatmap. The heatmap depicts the focus areas of the model. Red indicates higher activation, and blue indicates lower activation. While making the classification, the network focused on parts of the image other than the heart. Thoracic muscles, spleen, intestines, and lower pole of the kidney represented the focus points. The model classified this case incorrectly as abnormal with 94% certainty. C, D: Subject with cardiac disease in the sagittal plane with short axis view. C shows the T1 mapping image. In D, the image was overlaid with a gradient-weighted class activation map (Grad-CAM), generating a heatmap. The heatmap depicts the focus areas of the model. Red indicates higher activation, and blue indicates lower activation. The strongest focus of the model was the right ventricle, including part of the septum. The kidney and liver represent weaker focus areas of the deep learning model. The network diagnosed a cardiac pathology with 100% certainty