MRI Gating System for Two Signals Respiration and ECG or BP
The DTU300 is a dual channel gating system for human MRI applications (small animal system available, see DTU200). It sends cardiac trigger pulses to the MRI when a respiration signal is in the quiet phase. Pre-processing filters and gain controls further refine the quality of the signal and ensure reliable triggering.
Scan from 1-8 ECG pulses after fall of RSP where first acceptable ECG is >100 msec after RSP enters quiet phase
Blanking - adjust from 250-1500 msec (this will shut off ECG from reaching trigger)
Delay - adjust from 5-250 msec.
Trigger pulse - fixed at 500 µsec
Scan time = Blanking - Delay
The DTU300 system requires two analog input signals:
Cardiac signal (ECG or BP) from an ECG100C Electrocardiogram Amplifier.
Respiration signal from an RSP100C module and an MECMRI-TRANS cable/filter set.
Cardiac phase
Threshold: The ECG or Blood pressure signal passes through a user selectable threshold that creates a square wave (0-5 volt) cardiac trigger signal. The R-wave or BP signal crosses the threshold in both directions to initiate the MRI trigger signal pulse.
Delay: A delay control allows precise timing of the trigger signal pulse relative to the rising or falling edge of the ECG R-wave (1-50 msec).
Blanking: A blanking control provides a time discriminator (50-300 msec) that prevents the DTU300 system from falsely triggering on an ECG signal corrupted by MRI operational artifact.
Monitoring: The cardiac trigger channel is available for monitoring purposes using a BNC to 3.5 mm cable (CBL102, included). BIOPAC recommends monitoring this signal with the MP150 data acquisition and analysis system.
Respiration
Threshold: The respiratory system also passes through a similar threshold to create a square wave when the signal crosses the threshold in both directions. The quiet period is user-selectable to be the interval between rising and falling edges or falling and rising edges of the RSP signal.
Monitoring: This signal is available for monitoring purposes using a BNC to 3.5mm cable (included) CBL102. We recommend monitoring this signal with the MP150 data acquisition and analysis system.
The MRI trigger channel only outputs a cardiac trigger when the respiration trigger channel goes into the quiet period, which occurs when the animal is between breaths and still. The system will output a precise number of cardiac triggers between each respiratory period by adjusting the trigger count control (1-8). Cardiac cycles are only considered if they occur >100 msec after the respiration trigger goes into the quiet period. If there isn’t enough time to complete the required number of triggers, the unit will stop and wait for the next quiet period before starting a new count. For example, if the counter is set to output 5 triggers, but there is only enough time to send 4, the unit will ignore the fifth trigger and wait for the next quiet period before starting the count again.
Signal Monitoring
There are outputs for the cardiac and respiration conditioned signals (available at BNC ports: Buffered ECG/BP and Buffered RSP) and the respective triggers. The conditioned signals are in the ±10 volt level range and trigger outputs are 0-5 volts. Seven BNC to 3.5 mm monitoring cables (CBL102) are included.
Compatibility
The unit will interface with either a BIOPAC MP100 or MP150 system. It will also work with third-party amplifiers and data acquisition systems that operate in the ±10 volt range.
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