1. Wellcome/EPSRC Centre for Interventional and Surgical Sciences (WEISS), University College London, London, U.K.
2. School of Biomedical Engineering and Imaging Sciences, King's College London, London, U.K.
3. Institute of Automation, Chinese Academy of Sciences, and Centre of AI and Robotics (CAIR), Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Beijing, China