Fast cancer metastasis location based on dual magnification hard example mining network in whole-slide images

Abstract

Breast cancer has become the most common form of cancer among women. In recent years, deep learning has shown great potential in aiding the diagnosis of pathological images, particularly through the use of convolutional neural networks for locating lymph node metastasis under gigapixel whole slide images (WSIs). However, the massive size of these images at the highest magnification introduces redundant computation during the inference process. Additionally, the diversity of biological textures and structures within WSIs can cause confusion for classifiers, particularly in identifying hard examples. As a result, the trade-off between accuracy and efficiency remains a critical issue for whole-slide image metastasis localization. In this paper, we propose a novel two-stream network that takes a pair of low- and high-magnification image patches as input for identifying hard examples during the training phase. Specifically, our framework focuses on samples where the outputs of the two magnification networks are dissimilar. We adopt a dual magnification hard mining loss to re-weight the ambiguous samples. To more efficiently locate tumor metastasis cells in whole slide images, the two stream networks are decomposed into a cascaded network during the inference phase. The low magnification WSIs scanned by the low-mag network generate a coarse probability map, and the suspicious areas in the map are refined by the high-mag network. Finally, we evaluate our fast location dual magnification hard example mining network on the Camelyon16 breast cancer whole-slide image dataset. Experiments demonstrate that our proposed method achieves a 0.871 FROC score with a faster inference time, and our high magnification network also achieves a 0.88 FROC score.

Keywords: Convolutional neural network; Digital pathology; Dual magnification; Fast metastasis location; Hard example mining.