Neighbor-Guided Unbiased Framework for Generalized Category Discovery in Medical Image Classification

Generalized category discovery (GCD) utilizes seen category knowledge to automatically discover new semantic categories that are not defined in the training phase. Nevertheless, there has been no research conducted on identifying new classes using medical images and disease categories, which is essential for understanding and diagnosing specific diseases. Moreover, existing methods still produce predictions that are biased towards seen categories since the model is mainly supervised by labeled seen categories, which in turn leads to sub-optimal clustering performance. In this paper, we propose a new neighbor-guided unbiased framework (NGUF) that leverages neighbor information to mitigate prediction bias to address the GCD problem in medical tasks. Specifically, we devise a neighbor-guided cross-pseudo-clustering strategy, which exploits the knowledge of the nearest-neighbor samples to adjust the model predictions thereby generating unbiased pseudo-clustering supervision. Then, based on the unbiased pseudo-clustering supervision, we use a view-invariant learning strategy to assign labels to all samples. In addition, we propose an adaptive weight learning strategy that dynamically determines the degree of adjustment of the predictions of different samples based on the distance density values. Finally, we further propose a cross-batch knowledge distillation module to utilize information from successive iterations to encourage training consistency. Extensive experiments on four medical image datasets show that NGUF is effective in mitigating the model's prediction bias and has superior performance to other state-of-the-art GCD algorithms. Our code will be released soon.