Abstract
.Significance: Convolutional neural networks (CNNs) show the potential for automated classification of different cancer lesions. However, their lack of interpretability and explainability makes CNNs less than understandable. Furthermore, CNNs may incorrectly concentrate on other areas surrounding the salient object, rather than the network’s attention focusing directly on the object to be recognized, as the network has no incentive to focus solely on the correct subjects to be detected. This inhibits the reliability of CNNs, especially for biomedical applications.Aim: Develop a deep learning training approach that could provide understandability to its predictions and directly guide the network to concentrate its attention and accurately delineate cancerous regions of the image.Approach: We utilized Selvaraju et al.’s gradient-weighted class activation mapping to inject interpretability and explainability into CNNs. We adopted a two-stage training process with data augmentation techniques and Li et al.’s guided attention inference network (GAIN) to train images captured using our customized mobile oral screening devices. The GAIN architecture consists of three streams of network training: classification stream, attention mining stream, and bounding box stream. By adopting the GAIN training architecture, we jointly optimized the classification and segmentation accuracy of our CNN by treating these attention maps as reliable priors to develop attention maps with more complete and accurate segmentation.Results: The network’s attention map will help us to actively understand what the network is focusing on and looking at during its decision-making process. The results also show that the proposed method could guide the trained neural network to highlight and focus its attention on the correct lesion areas in the images when making a decision, rather than focusing its attention on relevant yet incorrect regions.Conclusions: We demonstrate the effectiveness of our approach for more interpretable and reliable oral potentially malignant lesion and malignant lesion classification.
Highlights
Deep learning has become a powerful tool in solving image classification problems[1] and has been widely used in medical image analysis.[2]
In our experiments on the oral cancer dataset, we found setting the hyperparameter matrix σ to be a matrix of values containing 0.20, and setting weighting hyperparameter w to 3.0 yielded the most optimum results in training the Convolutional neural networks (CNNs)’s attention map on the cancerous lesions
In contrast to Li et al.’s guided attention inference network (GAIN) Lam loss function, we found that reparametrizing our loss function as seen in Eq (5) produced results that led to more optimum convergence
Summary
Deep learning has become a powerful tool in solving image classification problems[1] and has been widely used in medical image analysis.[2]. Visual interpretability and attention maps for CNNs have been investigated for improving the robustness and accuracy.[10,11] Class activation mapping (CAM)[12] was developed to inject interpretability and explainability into decision-based deep learning models by highlighting the most discriminative region of an input image during classification. This approach requires modification of image classification CNN architectures, replacing fully connected layers with convolutional layers and global average pooling (GAP). When attempting to classify a specific object or class, the CNN may incorrectly concentrate on other areas around the salient object, rather than the network’s attention focusing on the object to be recognized.[14,15,16]
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