Automated Hemorrhage Detection from Coarsely Annotated Fundus Images in Diabetic Retinopathy

In this paper, we proposed and validated a novel and effective pipeline for automatically detecting hemorrhage from coarsely-annotated fundus images in diabetic retinopathy. The proposed framework consisted of three parts: image preprocessing, training data refining, and object detection using a convolutional neural network with label smoothing. Contrast limited adaptive histogram equalization and adaptive gamma correction with weighting distribution were adopted to improve image quality by enhancing image contrast and correcting image illumination. To refine coarsely-annotated training data, we designed a bounding box refining network (BBR-net) to provide more accurate bounding box annotations. Combined with label smoothing, RetinaNet was implemented to alleviate mislabeling issues and automatically detect hemorrhages. The proposed method was trained and evaluated on a publicly available IDRiD dataset and also one of our private datasets. Experimental results showed that our BBR-net could effectively refine manually-delineated coarse hemorrhage annotations, with the average IoU being 0.8715 when compared with well-annotated bounding boxes. The proposed hemorrhage detection pipeline was compared to several alternatives and superior performance was observed.