Clinician's Guide - Bio-Medical Instruments, Inc.

Understanding “values” seen in Infiniti MT assessment
screen:
(Only ‘glance’ at this until you are very comfortable running sessions)
This is easier if you understand the Appendix discussion on ‘magnitude’ (p. 147).
In the MT Infiniti assessment screen you will notice that the pk-pk amplitudes in the
EEG 2-40 Hz line graph and the coloured lines for pk-pk band widths (see below) are
very much higher amplitude values than the “mean” values given numerically for
different band widths and much much higher than the spectrum magnitude microvolt
values seen on the spectrum at the bottom of the screen. The discussion on derivation of
“power” values and then “magnitude” values from the raw EEG pk-pk values given in
the appendix (p. 147) will help you see how the numerical values will change drastically
depending on the unit-of-measurement that you have on the left hand ‘y’axis.
The important thing, at this juncture, is to see that this screen allows you to compare the
raw EEG to the spectrum. The spectrum is an average of the one second to the left of the
end of the EEG in play or replay mode and to the left of the ‘red’ line in the review mode.
This is really valuable for explaining the waves to a client. It is also valuable for you to
see the relative magnitude of the different frequencies. The peak-to-peak line graph and,
in the dual monitor assessment screens, the 3D spectrum really help you to see the bursts
of energy in different frequencies over a time period.
If you right click over the little numbers under the frequency bands (middle right side)
you will see that these are means. Don’t get confused, these are the means for that band
width up to the time you are at. In the screen below it is the mean to 5 seconds. You
could change these in screen editor to be the ‘instantaneous’ peak-to-peak’ or peak-topeak
+ damper values but we found these changed so quickly that just having a mean
seemed to be more helpful. Experiment and make your own choice.
“Raw” EEG
wave
On right
side note
“Mean” µv
values
Pk-Pk
µv values
Spectrum
“Magnitude”
µv values
Copyright ADD Centres Ltd. Prepublication – 1 st draft. Please do not copy. Dr. Thompson 905-803-8066 Canada 18