User manual
Version: v4.5.2
Markers
or
fiducials
geometrically deformed due to shocks
or manufacturing defects can create wrong measurements
leading to patient injury. Instructions about not using ge-
ometrically deformed
markers
or
fiducials
must be clearly
specified in the end user manual.
Markers
or
fiducials
too close from lenses might lead to
wrong measurement (see Table 2.1). The integrator has
to mention in the end user manual that
markers
or
fiducials
should not be positioned too close from the lenses.
The integrator has to ensure generating an error message
when the
markers
are placed on vibrating instruments and
the frequency of vibrations could affect the measurements.
At all time, the integrator software should monitor the regis-
tration error of the reconstructed
markers
, to prevent badly
reconstructed data to be used.
Instructions about using a calibrated
marker
and not geo-
metrically deformed have to be clearly specified by the inte-
grator to the user.
A
marker
is a rigid structure on which three or more
fiducials
are fixed so that the distance between
them is constant.
The fusionTrack system is compatible with both passive and active wireless
markers
. The fusionTrack
device identifies and tracks the
markers
using the geometry of the
fiducials
on the
marker
. The fusionTrack
device needs a geometrical description of each tracked
marker
(this description is called the geometry file).
Several causes related to
markers
might cause wrong measurements. Even when the
marker
itself has
not been geometrically deformed, any damages on
fiducials
might be an issue: when a fiducial is particularly
damaged, the
marker
might not be detected and tracked. In presence of a damage, the device is not able
to match the
marker
with a known geometry.
A significant value of error is critical for an accurate tracking. In some cases, the
marker
might even
disappear suddenly because the geometry is not identified anymore. In some cases, the
marker
in the field
of view of the fusionTrack could even not be detected. The integrator must indicate to the operator that the
computed error is critical. It could be a warning or error message.
7.6.1 Passive markers
The passive
markers
use reflecting material in various shapes (spheres or discs). The used passive material
has a specific coating which minimises the scattering of the IR light, allowing a large amount of it to be
reflected back to its source. This causes the IR light from the illuminators to be reflected directly into the
cameras. The fusionTrack system is designed to track the position and orientation of
markers
and the
position of individual reflecting objects.
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