‍Summary

‍When running an experiment, it is desirable to synchronize the start of a trial with the start of an fMRI scan. The interval between scans is known as the TR, or Repetition Time. When designing an experiment, a difficulty arises when the fMRI scanner is configured to send a trigger not only at the start of a scan, but also for slices during the interval.

‍Required Firmware

‍The feature required to enable filtering out the slice triggers was added in Lumina firmware version 2.2.7, dated September 2021. Please update your controller’s firmware if running an earlier version. You can use Xidon to determine the firmware version.

‍Filtering Out the Slice Triggers

‍On either Mac or Windows, after you download Xidon and run it:

• Click on Search for Device….
• Once the Lumina controller is detected, click on Experiment menu and choose Lumina 3G Options….
• Click on the Signal Options tab to select it.
• On the right hand side, in the list of “Signals:”, select “Scanner Trigger”.
• Turn on the option Enable single shot feature.
• In the offset edit field beneath it, enter the TR value less 1 or 2 milliseconds. For example, if the TR is 5 seconds, enter 4998ms.

‍If  your scanner’s TR has a lot of jitter, you would need to reduce the value you enter by more than 1 or 2 milliseconds.

‍Important: ‘Scanner Trigger’ LED is Not Affected

‍The single shot settings above affect the USB output and m-pod output, but not the Scanner Trigger LED on the Lumina controller. This is by design, for a couple of reasons. The LED is meant to help the user verify that the physical connection between the controller and the MRI scanner is established, and for this reason, its behavior is not affected by any of the signal options.

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Last revision: September 1, 2021