Non-contact parametric estimation and localization of human head for transcranial magnetic stimulation (TMS)

Transcranial magnetic stimulation (TMS) has been gaining popularity in various neurological treatments and an automated platform with better precision is desired. This paper proposes a dexterous articulated robotic arm with TMS coils as the end-effectors. Most robotic arm based positioning systems utilize vision feedback from stationary cameras for dynamic positioning, but these are not suitable for clinics with limited space. In this paper, a compact approach to identify the size, position and orientation of the patient's head relative to a robotic arm using a non-vision, range data based system is proposed. An accurate distance measurement sensor is used in tandem with a robotic arm to scan the patient's head and produce a growing 3D point cloud. An efficient surface fitting algorithm, taking into consideration the similarity of the human head to an ellipsoid, is presented to simultaneously extract position, orientation and geometrical information of the target head. Simulations and experiments are conducted and promising results are obtained to demonstrate its capability to identify the location and orientation of the patient's head.