ECL: Class-Enhancement Contrastive Learning for Long-tailed Skin Lesion
  Classification
Yilan Zhang Jianqi Chen Ke Wang Fengying Xie
Skin image datasets often suffer from imbalanced data distribution,
exacerbating the difficulty of computer-aided skin disease diagnosis. Some
recent works exploit supervised contrastive learning (SCL) for this long-tailed
challenge. Despite achieving significant performance, these SCL-based methods
focus more on head classes, yet ignoring the utilization of information in tail
classes. In this paper, we propose class-Enhancement Contrastive Learning
(ECL), which enriches the information of minority classes and treats different
classes equally. For information enhancement, we design a hybrid-proxy model to
generate class-dependent proxies and propose a cycle update strategy for
parameters optimization. A balanced-hybrid-proxy loss is designed to exploit
relations between samples and proxies with different classes treated equally.
Taking both "imbalanced data" and "imbalanced diagnosis difficulty" into
account, we further present a balanced-weighted cross-entropy loss following
curriculum learning schedule. Experimental results on the classification of
imbalanced skin lesion data have demonstrated the superiority and effectiveness
of our method.