Gating Setup When Large Artifacts Are Present In The Ecg Waveform - SA Instruments 1030 Operation Manual

Troubleshooting
Module was dropped during shipment, the heat chamber may be damaged. You might
start with a cold system and without the Fan and then with the FAN to try to understand
what is not working.
You can only get very low temperature if one of the following occurs:
1. Wrong voltage,
2. Fan not on or the processor thinks it is not on
3. Heat chamber housing cracked and leaking
Make certain the air hoses are connected properly. i.e. that the fan is not connected to
the "Warm Air" port on the Heater Module.

Gating Setup when large artifacts are present in the ECG waveform

The most common artifact in the ECG waveform is generated by vibrations of the ECG
leads due to activation of the pulsed gradients during MR system data acquisition.
When the MR scanner acquires imaging data, pulsed gradients are activated which
generates acoustic noise, movement of the gradient insert and corresponding
movement of the ECG leads. Vibration or movement of the ECG leads in the presence
of the strong static magnetic field creates artifacts on the ECG waveform.
Many factors contribute to the size and extent of vibration artifacts on the ECG
waveform. High field strength, long lead length, leads that are not taped and close
coupling of the animal to the gradient insert all make vibration artifacts more extensive.
However, in many cases it is not necessary to minimize the effects of vibration. It is
usually possible to create accurate and reliable triggers even with the presence of large
artifacts on the ECG waveform.
Follow these steps to generate accurate gating when large artifacts are present:
1. When the scanner is not acquiring data, check that each R-wave is detected and
that no false gates are generated. i.e make certain a red dot (ECG gate) is
present for each R-wave and that there are no extra red dots in the Cardio
Sweep display. If this is not the case, adjust the R-detect parameters according
to Chapter 3 of the Operation Manual.
2. Set the blanking time to 90% of the R-R interval.
displayed below the heart rate. Right clicking the ECG display will open the R-
DETECT SETUP window.
3. Run a gated scan with the total slice acquisition time at least 20 msec less than
the animal's R-R interval. It maybe useful to initially run a single slice scan to
observe the effect of gradient vibrations on the ECG waveform. As you increase
the number of slices, you will observe an increase in the width of the artifact
following the trigger generated by the R-wave. Note that 5 to 10 msec are
required for the vibrations to damp after the pulsed gradients are turned off. If
the total slice acquisition time is too long, a false trigger will be generated at the
end of the blanking time.
C-6
Revision C, August 2013
Note the R-R interval is