Biomedical Engineering Reference
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head which leads to pushing the head by the robot during stimulation. On the
contrary, hair can lead to a gap between coil and scalp which is also suboptimal
for coil positioning. As the coil touches the hair, the patients feel the contact and
report the coil on the head even though there is still a gap of a couple of
millimeters. Thus, optimal coil placement on the scalp can be difficult.
• General system safety:
Beside limiting the allowed robot trajectories, the robot velocity and accelera-
tion are limited on the software layer to maximize system's safety. To provide
security for the patient, the operator must continuously monitor the robot during
stimulation with the robot emergency button in reaching distance, which is an
exhausting task.
• Shift of head marker:
For tracking the patient's head, a marker is attached to the head and registered to
a virtual 3D head of the subject. However, over stimulation time (which can be
up to 1.5 h) the head marker might shift or become loose. Furthermore, patients
tend to shift the marker with the head band as it pushes or itches over time. This
results in inaccuracies of the registration and therefore in wrong coil positioning
with the robot. If noticed by the operator, a re-registration and re-start of the
stimulation is thus required. If not noticed, the stimulation outcome might be
biased.
As our systematic analysis and evaluation of robotized TMS shows the importance
of robotized TMS, we further improve the system to overcome the presented
deficits and problems. In this way, the robotized system becomes safe and clini-
cally applicable. The realization is explicitly described in the following chapters.
References
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