User manual
Version: v4.5.2
For those reasons, a new
marker
reconstruction algorithm was developped. For backward compatibility
reasons, the old one is still used as the default, and the new one can be enabled using a dedicated option.
7.5 Temperature compensation
The internal temperature of the fusionTrack device have a non-negligible rise time, which leads to a loss of
trueness in both following situations:
1. as long as the device is not thermically stable;
2. if the steady temperature does not correspond to the temperature at which the calibration was per-
formed.
In order to solve those issues, a temperature compensation algorithm is used. The compensation decreases
the loss of trueness in the warm-up phase and if the reached temperature is different from the temperature
during the calibration.
The
integrator
must
check
the
‘Calibra-
tion
type’
option
value
corresponds
to
CalibrationType::TemperatureCompensation
if
and
only if they want to use the temperature compensation.
The temperature compensation consists of multiple calibrations, each of them obtained at a different
temperature. The fusionTrack device has several temperature sensors, which values are combined to com-
pute a ‘synthetic temperature’. The ‘temperature compensated calibration’ is therefore stored as a set of
calibration parameters indexed by a ‘synthetic temperature’ value. On each frame, the current ‘synthetic
temperature’ value is computed, and a calibration is either interpolated or extrapolated from the ones con-
tained in the calibration file. New events (see Section 7.3.1) have been added to allow the user to:
- get the current ‘synthetic temperature’ and the value of the ‘synthetic temperature’ when the device
is stable in a room at 20 °C (called the reference temperature), only provided for user information
;
- know if the current ‘synthetic temperature’ value is either below the lowest one or above the highest
one: those events are
FtkEventType::fetLowTemp
and
FtkEventType::fetHighTemp
respectively.
The events are the only way to know if the SDK is interpolation or extrapolation mode, no specific status
codes are issued. The presence of those events do not necessarily mean the data must be discarded: for
instance, as soon as the synthetic temperature gets below the lowest temperature, the event is generated,
not taking into account the temperature difference (i.e. the difference being 0
.
1 °C or 10
.
0 °C does not make
any difference).
Depending on the fusionTrack device model, the temperature compensation might not be available.
7.6 The fusionTrack device markers
The
markers
used for surgery must be bio-compatible.
1
Since the external temperature modifies the synthetic temperature value at thermal equilibrium, the latter cannot be used by
the integrator in their regulation software.
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