Operational Protocol

The Operational Protocol of OPM will be fully ready during 2025.

There are three ways to coregister with OPM:

• First method:

  • laser scan the participants head and stylus points, before placing the participant in the OPM helmet

  • place participant in helmet, then laser scan the fiducials on the face again

  • laser scan the 8 points on the OPM helmet

  • we now can compute the rigid-body transformation of the head laser scan with restpect to the 8 points of the OPM helmet based on the fiducials laser points

  • computing this matrix, allows us to coregister the laser headscan with the OPM helmet

  • this method assumes that the participant is not moving their head within the OPM helmet

  • advantages: HPI coils are not needed

• Second method:

  • laser scan the participant head and stylus points

  • then place the participant in the OPM-helmet

  • then place HPI coils on known stylus points (must standardize those locations)

  • In this case, a script must be ran at beginning and end of the experiment to energize the coils with sinusoidal waves of known frequencies (follow up with fieldtrip tutorial section 2)

• Third method:

  • laser scan the participant, laser scan the fiducials

  • place participant in helmet, laser scan everything (i.e. face and helmet together)

  • mark fiducials

  • Coregister both set of fiducial