High-power switching and control system for concurrent TMS and MRI (under construction...)
Overview
We developed a switching and control system that allows the use of one coil for operation in both TMS and MRI modes. A switching box toggles between the two operation modes and the control system monitors the safety and transmits switching commands to the box itself.
Design
Two DCNEVT400 contactors (1.8kV, 400A) and two AEVT500 contactors (1.8kV, 3.3kA) are inside the switching box to switch in and out from MRI and TMS modes.
The Red Pitaya (FPGA, TEMLabs) and host computer coordinate operation mode transitions, MRI encoding sequences, and TMS pulse triggering.
The system reads an external trigger and starts the pre-programmed commands in the host computer. Through red pitaya, DAC, and control board, the command is executed as (1) encoding sequences that can be inputed into a gradient amplifier, (2) switching between different operation mode that instructs which pairs of contactors should be open/closed, and (3) TMS trigger that can be inputed into the TMS stimulator as the "trigger in" for firing TMS pulse.
Five fault conditions are actively monitored: (1) bad command, (2) TMS stuck open, (3) TMS stuck closed, (4) GPA stuck open, and (5) GPA stuck closed. Bad commands prevent unintended TMS pulses from being triggered when the TMS contactors are not fully closed or when a nonzero gradient amplifier current is detected during TMS mode. The TMS stuck open/closed and GPA stuck open/closed mechanisms continuously monitor the actual state of their respective contactors. If any fault condition is detected, the fault LED is activated, all contactors are immediately disengaged, and the system enters a safe shutdown state.
Circuit Design/Specifications
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