1. Introduction
High-resolution Electron Microscopy (EM) image has been used in biomedical research to investigate the detailed structure of tissues, cells, organelles and so on. For example, EM images were used to study Drosophila brain structure [1] which required segmentation of neural structures from the images. Manual labeling of each element in the image requires by an expert human neuroanatomist. However, due to the visual complexity of the EM images, it can be time-consuming for human experts to interpret them one-by-one, which drives the demand for automated approaches.