Introduction - Robotized Transcranial Magnetic Stimulation - page 15

Fig. 1.8 The tracking system and the robot are communicating with the TMS control program
via individual server programs that can either run on the same computer as the TMS GUI or on
extra computers (adapted from [ 46 ])
Now, all obtained tracking data is directly transformed into the robot coordinate
frame.
For navigation, a virtual head is reconstructed from individual 3D images from
the subject. For tracking, a headband with a passive marker is used. Prior to
stimulation, a head registration step must be performed, as discussed in Sect. 1.2.1 .
Thus, by tracking the head marker the position and orientation of the head is
known in relation to the robot.
The mounted TMS coil is registered to the robot's end effector. The geometrical
approach (cf. Sect. 1.2.2 ) for registration is used, but with calculation of the
transform to the end effector. The spatial position and orientation of the coil is now
computed with the current robot end effector position and the coil transform.
Now, the coil position in relation to the current head position can be estimated.
Based on that, the robot moves the coil to selected stimulation sites which can be
planned with the virtual head. Once the coil has reached the target, motion
compensation is automatically activated to keep the coil at the target.