Fiber Optic Universal Gating Module
Revision C, August 2013
17-2
Input fiber optic gate light pulse
Output 2 mV pulse on RA, LA, RL, LL studs
TTL pulse on BNC connector
Power switch activates the 9 V internal battery,
the power on and low battery LEDs
Setup and use
When used with a clinical MR system, the Fiber Optic Universal Gating Module is
positioned near the patient gantry. A simplex fiber optic cable is connected between the
ERT Control/Gating Module’s fiber optic AUX GATE output and the Universal Gating
Module’s fiber optic gate input. The ERT Control/Gating Module is located outside and
the Universal Gating Module is located inside the RF shielded room. So the simplex
cable should pass through a wave guide installed in the room.
The optical gate signal is converted to an electrical signal by the Universal Gating
Module. The electrical signal can be input to the clinical MR either by supplying the TTL
signal to a gate input port (if available) or by supplying the 2 mV pulse to the scanner’s
clinical ECG cable. In either case, it maybe advantageous to change the gate width or
invert the gate pulse using controls in PC-sam’s GATING window.
Clinical scanners typically use both analog and digital filters to remove gradient
interference from their ECG input. These filters necessarily add delay to the time the
gate is received by the scanner. This delay can be quite large, a few 10s of msec. So,
if a TTL gate input is available, it is preferred over input from the clinical ECG cable.
Caution: the 9 V battery should only be replaced
with a battery obtained from SAII. Many
9 V batteries are magnetic and may be
attracted by the MR magnet.
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