Discussion - Robotized Transcranial Magnetic Stimulation - page 155

Even though the ISO 9241-11, elaborated by the International Organization for
Standardization (ISO), is an international standard that was actually developed for
human-computer interaction, we can relate the hand-assisted positioning method
to this standard. In particular, the ISO 9241-11 defines a guidance on usability for
ergonomic human-computer interaction [ 8 ]. To this end, it identifies three guiding
principles to achieve usability:
• effectiveness to solve the task (completion of the task),
• efficiency in controlling the system (solving the task in time), and
• satisfaction of the user.
In the case of robotized TMS the task is to position the coil at the stimulation site
with a given coil orientation. With the hand-assisted positioning method the user is
now able to position the coil precisely at the stimulation site as shown in our
practical evaluation. Therefore, the task can be solved effectively with hand-
assisted positioning. Our practical test has also shown that inexperienced user only
need a very short period of time (a few minutes) to get familiar with the control.
As the coil positioning at the stimulation target was achieved in less than a minute,
we can conclude that the task was solved in time. Hand-assisted coil positioning is
also faster than coil positioning with the robotized TMS software. Therefore, hand-
assisted positioning allows for efficient coil positioning with a robotized TMS
system. Satisfaction of the user is clearly hard to show in figures. However, as the
users achieved the positioning of the coil at the targets accurately (mean error
below 0.8 mm), stably (mean variation 0.6 mm), and easily without complications,
we might assume that the users were satisfied in solving the task.
In total, we can therefore assume that hand-assisted positioning provides
usability in coil positioning with the robotized TMS system. Hence, it is a key
factor for the system's (clinical) acceptance. Therefore, the latest addition to
SmartMove TM , called TouchSense (Advanced Neuro Technology B.V., Enschede,
The Netherlands), is based on the presented FTA sensor with the optimized hand-
assisted positioning [ 1 ].
9.5 Direct Head Tracking
As direct head tracking is a promising alternative to indirect tracking, we devel-
oped and tested different systems and methods for their capabilities of accurate
head tracking for navigated or robotized TMS.
9.5.1 FaceAPI
The evaluation of the FaceAPI has shown that an application in the robotized TMS
system is not feasible. However, as the FaceAPI's tracking idea is promising, the