Fully refocused multi-shot spatiotemporally encoded MRI: Robust imaging in the presence of metallic implants

Noam Ben-Eliezer, Eddy Solomon, Elad Harel, Nava Nevo, Lucio Frydman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Object An approach has been recently introduced for acquiring arbitrary 2D NMR spectra or images in a single scan, based on the use of frequency-swept RF pulses for the sequential excitation and acquisition of the spins response. This spatiotemporal-encoding (SPEN) approach enables a unique, voxel-by-voxel refocusing of all frequency shifts in the sample, for all instants throughout the data acquisition. The present study investigates the use of this full-refocusing aspect of SPEN-based imaging in the multi-shot MRI of objects, subject to sizable field inhomogeneities that complicate conventional imaging approaches. Materials and methods 2D MRI experiments were performed at 7 T on phantoms and on mice in vivo, focusing on imaging in proximity to metallic objects. Fully refocused SPEN-based spin echo imaging sequences were implemented, using both Cartesian and back-projection trajectories, and compared with k-space encoded spin echo imaging schemes collected on identical samples under equal bandwidths and acquisition timing conditions. Results In all cases assayed, the fully refocused spatiotemporally encoded experiments evidenced a ca. 50 % reduction in signal dephasing in the proximity of the metal, as compared to analogous results stemming from the k-space encoded spin echo counterparts. Conclusion The results in this study suggest that SPENbased acquisition schemes carry the potential to overcome strong field inhomogeneities, of the kind that currently preclude high-field, high-resolution tissue characterizations in the neighborhood of metallic implants.

Original languageEnglish (US)
Pages (from-to)433-442
Number of pages10
JournalMagnetic Resonance Materials in Physics, Biology and Medicine
Volume25
Issue number6
DOIs
StatePublished - Dec 2012

Keywords

  • Field inhomogeneities
  • Frequency-swept pulses
  • Fully refocused acquisitions
  • High-definition MRI
  • Metal-implant artifacts
  • Spatiotemporal encoding

ASJC Scopus subject areas

  • Biophysics
  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

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