| 摘要 |
Refractory delay circuitry ensures that induced currents do not falsely rigger the acquisition phase of magnetic-resonance instrumentation. Immediately after the triggering of the acquisition sequence, for example, by the R-wave of a subject's cardiac cycle, the adjustable delay circuit is used to inhibit further trigger signals for a predetermined duration of the acquisition gradient activity. The acquisition sequence will thus not be triggered by extra peaks in the biological signal, which may take the form of non-R-wave signals in the cardiac cycle. In this embodiment of the invention triggering will occur only at most once per heartbeat. As cardiac signals may be divided into two major groups, electrical (ECG) and non-electrical (e.g., coronary artery pressure wave, or arterial flow signals) which exhibit two different frequency ranges, the invention typically utilizes separate filtering components for the isolation of these two types of signals, thus allowing for the selection of either stimulus for triggering purposes.
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