Closing Remarks - Robotized Transcranial Magnetic Stimulation - page 161

be adapted (cf. Sect. 1.1.4 ) . Once the MT is calculated, the robot will move the
coil to the planned treatment target, set the stimulation intensity and start the
stimulation. The FTA sensor monitors the automated system and will guarantee its
safety. Even though most of the described methods already exist, due to technical
constraints, it will not be available in the near future. These constraints are for
instance:
• a robust automatic MEP amplitude detection,
• a stable motor threshold estimation method,
• a deterministic and reliable automated hot-spot estimation, and
• the interaction and combination of all the single systems and methods.
Nevertheless, in case rTMS should be established as a treatment tool for psychi-
atric and neurological conditions, fully automated TMS will be a promising tool
for efficient and effective rTMS treatments.
10.2.2 Mapping of the Spinal Roots
Previous work has used the robotized TMS system for an accurate mapping of the
brain [ 11 , 15 ]. However, it is important not to forget that also the other part of the
central nervous system, which is the spinal cord, plays an important role for
stimulus transmission. Therefore, the used brain mapping methods could be
adapted for the stimulation of the spinal roots with TMS. Mapping of the response
to TMS could directly prove the theory that the fibers are stimulated where they
pass through the Intervertebral foramina. Precisely navigated stimulation could
also facilitate studies that non-invasively relate stimulation of one single defined
root with a muscle response.
The neck area, which is the target region for spinal root stimulation, is non-rigid
in contrast to the scalp. This makes an accurate navigation and a precise mapping
challenging:
• A marker must be rigidly attached to the neck or upper back for navigation.
• This marker must be registered to the neck/back area. Therefore, the current
registration methods must be extended for non-rigid registration [ 7 ].
• As the neck/back area is non-rigid, patient motion must be minimized and the
registration might be updated online during operation. The use of several
markers, surrounding the target region and tracked in parallel might be helpful.
• The robot control and trajectory planning must be adapted to allow targeting the
neck or back.
• A model of the fibers must be extracted from individual scans as basis for the
mapping algorithm.
• Finally, the computation model used for brain mapping must be changed to
allow for use of nerve fibers instead of gray and white matter.