Feedback methods for collision avoidance using virtual fixtures for robotic neurosurgery in deep and narrow spaces. - Atsushi Nakazawa; Kodai Nanri; Kanako Harada; Shinichi Tanaka; Hiroshi Nukariya; Yusuke Kurose; Naoyuki Shono; Hirohumi Nakatomi; Akio Morita; Eiju Watanabe; Naohiko Sugita; Mamoru Mitsuishi (BioRob, 2016)