Question-guided feature pyramid network for medical visual question answering

Medical VQA (VQA-Med) is a critical multi-modal task that raises attention from the community. Existing models utilized just one high-level feature map (i.e., the last layer feature map) extracted by CNN and then fused it with semantic features through the co-attention mechanism. However, only using the high-level feature as a visual feature often ignores the details of the image, which are crucial for VQA-Med. In addition, questions often serve as a guide to targets of attention in the medical image. Therefore, in this paper, we propose a question-guided Feature Pyramid Network (QFPN) for VQA-Med. It extracts multi-level visual features with a feature pyramid network (FPN). In this way, the multi-scale information of medical images can be captured by using the high resolution of low-level features and rich semantic information of high-level features. Besides, a novel question-guided dynamic filter network (DFN) is designed to modulate the fusion progress of multi-level visual features and semantic features with respect to the raised question. Extensive results have demonstrated the effectiveness of the QFPN. Especially, we beat the winner of the 2019 ImageCLEF challenge and achieved 63.8% Accuracy and 65.7% BLEU in the ImageCLEF 2019 VQA-Med dataset.