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Proceedings Paper

Spherical navigator echoes for full 3D rigid body motion measurement in MRI
Author(s): Edward B. Welch; Armando Manduca; Roger Grimm; Heidi Ward; Clifford R. Jack
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Paper Abstract

We are developing a 3-D spherical navigator (SNAV) echo technique for MRI that can measure rigid body motion in all six degrees of freedom simultaneously, in a single echo, by sampling a spherical shell in k-space. MRI pulse sequences were developed to acquire varying amounts of data on such a shell. 3-D rotations of an imaged object simply rotate the data on this shell, and can be detected by registration of magnitude values. 3-D translations add phase shifts to the data on the shell, and can be detected with a weighted least squares fit to the phase differences at corresponding points. Data collected with a computer controlled motion phantom with known rotational and translational motions was used to evaluate the technique. The accuracy and precision of the technique depend on the sampling density, with roughly 1000 sample points necessary for accurate detection to within the error limits of the motion phantom. This number of samples can be captured in a single SNAV echo with a 3-D helical spiral trajectory. Motion detection in MRI with spherical navigator echoes is thus feasible and practical. Accurate motion measurements about all three axes, suitable for retrospective or prospective correction, can be obtained in a single pulse sequence.

Paper Details

Date Published: 3 July 2001
PDF: 8 pages
Proc. SPIE 4322, Medical Imaging 2001: Image Processing, (3 July 2001); doi: 10.1117/12.431158
Show Author Affiliations
Edward B. Welch, Mayo Clinic and Foundation (United States)
Armando Manduca, Mayo Clinic and Foundation (United States)
Roger Grimm, Mayo Clinic and Foundation (United States)
Heidi Ward, Mayo Clinic and Foundation (United States)
Clifford R. Jack, Mayo Clinic and Foundation (United States)

Published in SPIE Proceedings Vol. 4322:
Medical Imaging 2001: Image Processing
Milan Sonka; Kenneth M. Hanson, Editor(s)

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