Title | Fully refocused multi-shot spatiotemporally encoded MRI: robust imaging in the presence of metallic implants. |
Publication Type | Journal Article |
Year of Publication | 2012 |
Authors | Ben-Eliezer N, Solomon E, Harel E, Nevo N, Frydman L |
Journal | MAGMA |
Volume | 25 |
Issue | 6 |
Pagination | 433-42 |
Date Published | 2012 Dec |
ISSN | 1352-8661 |
Keywords | Algorithms, Animals, Calibration, Echo-Planar Imaging, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Metals, Mice, Mice, SCID, Models, Statistical, Phantoms, Imaging, Prostheses and Implants, Reproducibility of Results, Software |
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 SPEN-based 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. |
DOI | 10.1007/s10334-012-0318-7 |
Alternate Journal | MAGMA |
PubMed ID | 22743822 |
Related Institute:
MRI Research Institute (MRIRI)