[Brainmap] TODAY 4/7 noon @ CNY149 (LOCATION: Conf. Rm A): M Dylan Tisdall on Prospectively Motion-corrected Anatomical Imaging

Adrian KC Lee akclee at nmr.mgh.harvard.edu
Wed Apr 7 10:43:58 EDT 2010
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TODAY 4/7/10 at noon
NOTE: Conference Room A
149 13th St., Charlestown Navy Yard

M. Dylan Tisdall, Ph.D.
Research Fellow, Department of Radiology, HMS

Prospectively Motion-Corrected Anatomical Imaging: Available on a  
Scanner Near You


3D-encoded MPRAGE and T2SPACE scans are used routinely to produce high- 
quality T1- and T2-weighted images of neuroanatomy. However, because  
of their extended duration, these scans are particularly sensitive  
to   subject motion. We present our recent work on making these  
sequences less sensitive to motion by introducing EPI-based navigators  
and using the PACE registration algorithm currently used in fMRI  
sequences. Our system allows users to perform motion-corrected MPRAGE  
and T2SPACE scans and have their images reconstructed on the scanner  
just as with the standard MPRAGE and T2SPACE sequences.

Prospective motion correction systems attempt to modify the scanning  
coordinates "on the fly" so that imaging occurs in consistent "patient  
coordinates" regardless of subject motion during the scan. Currently  
most users will be familiar with prospective motion correction via the  
PACE system for fMRI. In fMRI the scanner collects a succession of  
volumes with similar contrast. As the subject moves, the PACE  
algorithm attempts to prospectively motion-correct the imaging  
coordinates by registering the most recently acquired image volume to  
the first image volume. This gives an estimate of where the subject  
was last located and the scanning coordinates can be updated so that  
the image volumes are (ideally) aligned as they are acquired, instead  
of requiring alignment in post-processing.

We have extended this concept to anatomical imaging by embedding  
complete EPI volume acquisitions in each TR of the MPRAGE and T2SPACE  
sequences. This can be done at no cost in scan time because both  
sequences already have substantial "dead times" required to produce  
their desired contrast properties. As in the fMRI case, our sequences  
register the EPI volume acquired during each TR back to the volume  
captured in the first TR using the same PACE registration algorithm.  
We can then update the scan coordinates each TR to ensure that the  
coordinates of the anatomical imaging sequence remain consistent with  
the subject throughout the duration of the scan.

As these sequences are now available in Bays 3 and 4, we will discuss  
some of the practical issues associated with their use by groups at  
the center, as well as our future plans for the development of motion- 
insensitive anatomical imaging.

Adrian KC Lee, ScD
Martinos Center for Biomedical Imaging
149 13th St., Suite 2301
Charlestown, MA 02129
Tel: 617-726-8791
Fax: 617-726-7422

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