The characteristic QRS complex of the ECG signal is used as a trigger
signal. Simultaneous acquisition and overlaying of the orthogonal
leads (vector cardiography) is used to minimize triggering errors due
to gradient switching and the magneto-hydrodynamic effect (i.e.
excess T-wave amplitude).
In the dialog box of the Physiological Display several trigger
methods are available:
◾ VCG standard: VCG activated
◾ ECG I: VCG inactive
◾ ECG II: VCG inactive
◾ ECG III: VCG inactive
◾ Auto: Improved trigger algorithm; VCG activated; default trigger
method
If Auto is used, the signal characteristics can be relearned by
selecting Relearn in the context menu of the Physiological Display.
If triggering with Auto fails, preferably VCG standard should be used.
For ECG triggering, special MR Conditional and disposable electrodes
are used (the recommended ones are available through the
Accessories catalog).
Performing
The quality of the ECG signal for triggered measurements is enhanced
by:
◾ Proper placement of the electrodes
◾ Good skin contact of the electrodes
Trigger methods
Disposable electrodes
4.3.2
Image quality
4 Physiological imaging
92
MR System | Operator Manual
Print No. M6-04401.621.02.02.02
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