Before revision:  Accurate detection and segmentation of densely-packed nuclei in images acquired under a variety of conditions is the major challenge. With a sufficient number of training examples, Mask R-CNN based methods have achieved state-of-the-art results on nuclei segmentation.
After revision:  Accurate detection and segmentation of densely-packed nuclei in images acquired under a variety of conditions . With sufficient training examples, Mask R-CNN based methods have achieved state-of-the-art results on nuclei segmentation.