Sunday, January 29, 2012
In this and a subsequent post I am going to cover some common situations when the N/2 ghosts can become abnormally high, i.e. higher than it is possible to achieve with comparatively small tweaks to the setup. For now I am going to restrict the discussion to temporally static, or persistent, ghosts. Furthermore, I will restrict the discussion to situations over which you can exert some control, usually through the subject setup and via EPI parameter selection. I'll cover the origins of dynamic ghosts later on in this series, once you've got a better grasp of the common persistent ghosting sources and are in a position to differentiate between a source that is intermittent and a (persistent) ghost that is being modulated by subject motion.
Before we get into the different experimental conditions that can lead to abnormally high ghosting, it is important that you are familiar with the reason why N/2 ghosts arise in EPI in the first place. So, if the following section sounds like Swahili (and you don't ordinarily speak Swahili) then I would encourage you to spend twenty minutes reviewing the section on N/2 ghosts in PFUFA Part Twelve before continuing here.
Friday, January 27, 2012
My colleague, DS has begun a new blog, mathematiCal Neuroimaging, dedicated to exploration of the mathematical principles underlying neuroimaging methods. Here are some excerpts from the section labeled About:
As the name of the blog partially implies, the topic here will be the mathematics and physics of neuroimaging. In particular the focus will be upon functional imaging of the brain.
The style of this blog will range from tutorial-like expositions of present functional neuroimaging technology to whimsical explorations of how we might create better functional neuroimaging technology.
An entry on parallel imaging has just been posted. See you over there!