[Freesurfer] bbregister problems with PET data

Hi Freesurfer team,

I’m encountering a problem using bbregister on PET data:

-- When I attempt to register a PET volume to T1-space the asymmetric tracer uptake of the PET throws off proper registration. (Treating the PET as a T1 because of the non-specific white matter uptake > grey matter signal).

-- You can really see the bbregister mis-registration in this gif here: https://goo.gl/iM6yrT

-- It (expectedly) attempts to find the best match between signal intensities on both the left and right surfaces, but is inherently biased by the asymmetric uptake shifts the entire volume to the right.

-- Are there any suggestions for dealing with asymmetric scans like this? Stick with just a simple FLIRT? It doesn't seem to do that great a job for everyone.

Cutting left and right hemispheres apart and register separately?

Using Martin’s new robust register for multi-modal data? Any suggestions on the parameters of ROBENT?

Thanks, Adam