ELECTRONIC POSTER - ismrm

Tuesday 13:30-15:30 Computer 121
13:30 5027. Prospective Motion Correction for MRI with a Single Retro-Grate Reflector Target
and a Single Camera
Maxim Zaitsev 1 , Brian S. R. Armstrong 2 , Brian Andrews-Shigaki 3 , Todd P. Kusik 2 , Robert
T. Barrows 2 , Kazim Gumus 3 , Ilja Y. Kadashevich 4 , Thomas Prieto 5 , Oliver Speck 4 ,
Thomas M. Ernst 3
1 Dept. of Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2 Electrical
Engineering and Computer Science, UW-Milwaukee, Milwaukee, WI, United States; 3 John A. Burns School of
Medicine, University of Hawaii, Honolulu, HI, United States; 4 Biomedical Magnetic Resonance, Otto-von-
Guericke University,, Magdeburg, Germany; 5 Medical College of Wisconsin, Milwaukee, WI, United States
Even subtle motions degrade MR image quality. With optical stereoscopic motion tracking it is possible to correct for head motion in
6 degrees of freedom. However, it is extremely difficult to realise in the tight geometric constraints of the MR scanner, while keeping
up with comfort and handling requirements of the clinical routine. Optical motion tracking with a single retro-grate reflector (RGR)
target and a single camera has a great potential due to its versatility and accuracy. Reported here is the successful implementation of a
prospective real time motion correction with RGR tracking, aiming at developing easy-to-handle motion correction strategies.
14:00 5028. Breathing Motion Artifact Reduction for MRI with Continuously Moving Table
Using Motion Consistent Retrospective Data Selection
Matthias Honal 1 , Jochen Leupold 1 , Tobias Baumann 2
1 Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2 Dept. of
Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany
A retrospective breathing motion compensation technique for axial MRI with continuously moving table is proposed. Redundant free
breathing acquisitions are performed and motion consistent undersampled k-spaces are retrospectively extracted for parallel imaging
reconstruction. Compared to a conventional reconstruction from free breathing data artifacts are significantly reduced. Except for
increased noise, the achieved image quality is comparable to a reconstruction from a breath-hold acquisition.
14:30 5029. 3D PROMO MRI with Online Automatic Slice Positioning
Nathan Scott White 1 , Josh Kuperman 2 , Beth Ripley 2 , Ajit Shankaranarayanan 3 , Eric
Han 3 , Anders Dale 2,4
1 Dept. of Cognitive Science, University of California, San Diego, La Jolla, CA, United States; 2 Dept. of
Radiology, University of California, San Diego, La Jolla, CA, United States; 3 Global Applied Science Lab, GE
Healthcare, Menlo Park, CA, United States; 4 Dept. of Neuroscience, University of California, San Diego, La
Jolla, CA, United States
We present an extension to the real-time 3D "PROspective MOtion correction" (PROMO) framework for online correction of
between-scan motion in 3D sequences through automatic slice plane positioning. Initial results demonstrate an intra-subject alignment
precision of better than 1 mm/deg, despite initial position/landmark differences of over 13 mm. Given current scanner and computer
hardware capabilities, the alignment procedure can be done in about a second or two, making it suitable to be integrated as part of a
routine automatic pre-scan procedure.
15:00 5030. Motion-Induced Frequency and Shim Variations During Localized 1H MR
Spectroscopy with Prospective Motion Correction
Brian Keating 1 , Thomas Ernst 1
1 Department of Medicine, John. A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United
States
Motion during brain 1H MR spectroscopy may cause susceptibility-induced changes in B0. We used a PRESS sequence with
prospective motion correction (PMC) to quantify the effects of motion on center frequency and shim quality. Subjects performed x-
and z-head rotations while the MRS voxel tracked head motion. The center frequency displays a linear dependence on both θx
(0.01ppm/deg) and θz (0.002ppm/deg). The FWHM is approximately a quadratic function of the θx, but is largely independent of θz.
Our results indicate that PMC requires real-time frequency and shim updates in order to recover high-quality spectra in the presence of
subject motion.
Wednesday 13:30-15:30 Computer 121
13:30 5031. Head Pose Prediction for Prospectively-Corrected EPI During Rapid Subject
Motion
Julian Maclaren 1 , Rainer Boegle 1 , Michael Herbst 1 , Jürgen Hennig 1 , Maxim Zaitsev 1
1 Medical Physics, Dept. of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany
The final goal of this project is fMRI of moving subjects using prospective motion correction. An optical tracking system provides
head pose data in six degrees of freedom, which are used to prospectively update the imaging volume. However, latency delays in the
tracking system, and the effective echo time of the sequence, result in a time lag between position measurement and the acquisition of
the central k-space line. This causes in errors in slice registration. This work shows that motion prediction using a Kalman filter can
solve this problem.