Fig. 2

The CNN model with Grad-CAM was used on the ovarian tumour. a and d: Two-dimensional US image; b: Grad-CAM, the red area displayed the basis of decision-making of CNN; c: CEUS; e and f: histopathological results: struma ovarii (20× and 40×, respectively). Note: Grad-CAM, gradient-weighted class activation mapping; CNN, convolutional neural network; CEUS, contrast-enhanced ultrasound