NIRStar 14.1 - User Manual
Page 50 of 124
Critical – Signal quality is low and neuro-activation signatures may be obscured by signal noise. Most
likely, insufficient coupling of light into/out of the tissue is the reason; please check and try to improve
the preparation of the optode-tissue contact.
Lost – The signal is severely compromised to the point that no extraction of meaningful physiological
information can be expected from this channel. Possible reasons include: Mis-placement of the optical
probe, improper probe-tissue contact, lose or improper hardware connections.
If signal quality remains insufficient (especially, ‘Lost’ = white) despite efforts to improve
skin-optode contact, and no obvious erroneous connection or placement of probe
hardware, please check whether the hardware is working properly by running calibration
and dark-noise tests with the static phantom supplied with NIRx imagers.
This classification is a combined metric that takes into account all features of the traditional setup display
(Gain, Level, Noise: please see definitions on section 8.2) at all wavelengths according to the table below.
Table 2. Look-up table for the calculation of the signal quality scale considering each of the indicators separately.
The signal parameters shown in Table 2 are evaluated from left to right, i.e., the quality scale algorithm
first checks whether an excellent gain was reached for a channel, then evaluates the signal strength in
both wavelengths, and lastly estimates the noise level encountered.
The final classification of the signal quality for a given channel relies on the worst indicator obtained.
Figure 32 shows an example of Signal Quality map in which all the channels were judged as Excellent, i.e.
the masked channels have received amplification Gains within the range [1 - 6] (NIRScout), the resulting
Levels obtained for them lie within [0.09 – 1.40]V and the corresponding Noise values are under 2.5%.
The values obtained for each of the parameters listed in the table above can be individually checked
using the main function Details (see section 15.2).
To Next Page
Loading...
Need help?
General
