Hi Graham, this is usually caused by either motion, which there's not that much you can do about, or an MR problem, which you can. The most likely MR problem is from "partial k" or "fast" options. Make sure you are collecting all of k-space and see if things get better.
cheers, Bruce On Wed, 4 Jun 2003, Graham Wideman wrote: > Folks: > > Indirectly a FreeSurfer question. > > We are trying to process some images that have visible Gibbs artifact (aka > "truncation" artifact). This shows up as "ringing" -- artifact lines > parallel to large intensity discontinuites, such as air-skull or skull-CSF. > > In places these ripples of intensity can impinge on the outer areas of grey > matter. While these artifacts are visible, they generally don't fool the > naked eye as to where pial and grey-white boundaries are, but they are > tripping up FS's boundary finding. > > Has anyone on this list had any experience trying to eliminate or reduce > these artifacts -- either on images that have been gathered, or by > adjusting MRI parameters to reduce them in the first place? > > Thanks, > > Graham > > > --------------------------------------------------- > Graham Wideman > Author of: Visio 2002 Developer's Survival Pack > Microsoft MVP for Visio > Resources for programmable diagramming at: > http://www.diagramantics.com > http://www.wideman-one.com >
