Spherical navigator echoes for full 3-D rigid body motion measurement in MRI

E. B. Welch, A. Manduca, R. Grimm, H. Ward, C. Jack

Research output: Contribution to journalConference article

1 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)796-803
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
Issue number2
StatePublished - Jan 1 2001
EventMedical Imaging 2001 Image Processing - San Diego, CA, United States
Duration: Feb 19 2001Feb 22 2001


  • Motion artifacts
  • Motion correction
  • MRI
  • Navigator echo
  • Pulse sequence
  • Sphere

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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