Biomedical Engineering Reference
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Fig. 8.7 MRI head contour
of head phantom with
overlying 3D laser scan.
Larger dark dots mark initial
landmarks for registration
Even though these tracking errors are roughly 10 times larger than tracking
errors of typical optical tracking systems [ 11 , 19 ], the results suggest that direct
head tracking with 3D laser scans is feasible. Note that for this estimation the ICP
registration was performed between two 3D laser scans instead of a registration of
a laser scan to an MRI scan, as above. Therefore, the ICP error might be essentially
larger which influences the tracking accuracy. Coil Registration
In order to proof the capability of the 3D laser scanning system to perform a coil
calibration for the robotized TMS system, we have scanned two different TMS
Figure 8.9 shows the laser scans of the two TMS coils. For instance, the laser
scan of the small circular coil consists of roughly 5,500 surface points. The scan of
the figure-of-eight coil, due to its larger size, comprises almost 15,000 points. For
both coils, the shape of the coil is clearly visible. Furthermore, the size of the coils
in the scatter plots is in accordance with the size the real coils.
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