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Chapter 3
PC and ERT Control/Gating Module
Overview
The ERT Control/Gating Module, located near the operator's console, is connected to a
PC to provide operator control as well as display and storage of waveforms, computed
gates, measured values and trends.
The optical signal received at the ERT Control/Gating Module from the ERT Module is
demodulated and separated into ECG, respiration from the pneumatic pillow sensor and
temperature components before being processed to detect the R-wave (primary) peak
of the ECG waveform. Operator control of the QRS (R-wave) detection algorithm is
affected from the PC by selecting threshold values for the QR (leading) and RS (trailing
of opposite polarity) slew rates as well as ECG gate blanking time. Slew rate control
allows reliable determination of the ECG R-wave peak with minimal delay.
Gate
blanking time is set to eliminate unwanted gates from secondary peaks and/or
interference.
The respiration waveform from the pneumatic pillow sensor is automatically processed
to detect inspiration. When the animal takes air into the lungs, the pillow sensor is
compressed and the respiration waveform dips. The dip in the waveform is detected
and an inspiration gate is generated. The inspiration gate is usually inverted to make an
expiration gate. Both the beginning delay and maximum width of the gate are user
controlled.
The E-Resp respiration waveform is extracted from digitized ECG measurements and
processed to detect inspiration. Respiration gates (E-Resp gates) are determined
either automatically or manually from the E-resp waveform.
Gate position in the
respiratory cycle can also be set by the user similar to P-resp or respiration gates..
Monitor display
The monitor display is user configurable from the MONITOR SETUP window. Double
clicking the PC-sam icon on the PC desktop generates an option to enter the MONITOR
SETUP window before starting the monitor.
A typical monitor display configuration is shown on the next page. In this example, the
parameters monitored are ECG, respiration and temperature. Detection of the R-wave
(QRS complex) is indicated by the presence of a red dot on the cardio sweep display
above the R-wave peak.
The respiration waveform dips during animal inspiration and exhibits only small changes
in amplitude during expiration. Expiration is indicated by the presence of a red bar
above the appropriate portion of the waveform.
White dots in the cardio sweep display are also shown in the respiration sweep display.
They indicate times when gates have been sent to the scanner to initiate image data
acquisition. In this case, the gating algorithm included both ECG and respiration, so red
dots (R-waves) only generate white dots (gates) when they occur during animal
expiration.
Revision C, August 2013
3-1
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