Class-balanced Open-set Semi-supervised Object Detection for Medical Images
This addresses the challenge of leveraging imbalanced and unlabeled medical image data with unknown classes to improve object detection, which is incremental as it builds on existing semi-supervised methods.
The paper tackles the problem of open-set semi-supervised object detection for medical images, where unlabeled data contain out-of-distribution classes and class imbalance, and achieves a 4.25 mAP improvement on the Parasite dataset.
Medical image datasets in the real world are often unlabeled and imbalanced, and Semi-Supervised Object Detection (SSOD) can utilize unlabeled data to improve an object detector. However, existing approaches predominantly assumed that the unlabeled data and test data do not contain out-of-distribution (OOD) classes. The few open-set semi-supervised object detection methods have two weaknesses: first, the class imbalance is not considered; second, the OOD instances are distinguished and simply discarded during pseudo-labeling. In this paper, we consider the open-set semi-supervised object detection problem which leverages unlabeled data that contain OOD classes to improve object detection for medical images. Our study incorporates two key innovations: Category Control Embed (CCE) and out-of-distribution Detection Fusion Classifier (OODFC). CCE is designed to tackle dataset imbalance by constructing a Foreground information Library, while OODFC tackles open-set challenges by integrating the ``unknown'' information into basic pseudo-labels. Our method outperforms the state-of-the-art SSOD performance, achieving a 4.25 mAP improvement on the public Parasite dataset.