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- Title
Off-resonance suppression for multispectral MR imaging near metallic implants.
- Authors
den Harder, J. Chiel; van Yperen, Gert H.; Blume, Ulrike A.; Bos, Clemens
- Abstract
Purpose Metal artifact reduction in MRI within clinically feasible scan-times without through-plane aliasing. Theory and Methods Existing metal artifact reduction techniques include view angle tilting (VAT), which resolves in-plane distortions, and multispectral imaging (MSI) techniques, such as slice encoding for metal artifact correction (SEMAC) and multi-acquisition with variable resonances image combination (MAVRIC), that further reduce image distortions, but significantly increase scan-time. Scan-time depends on anatomy size and anticipated total spectral content of the signal. Signals outside the anticipated spatial region may cause through-plane back-folding. Off-resonance suppression (ORS), using different gradient amplitudes for excitation and refocusing, is proposed to provide well-defined spatial-spectral selectivity in MSI to allow scan-time reduction and flexibility of scan-orientation. Comparisons of MSI techniques with and without ORS were made in phantom and volunteer experiments. Results Off-resonance suppressed SEMAC (ORS-SEMAC) and outer-region suppressed MAVRIC (ORS-MAVRIC) required limited through-plane phase encoding steps compared with original MSI. Whereas SEMAC (scan time: 5′46″) and MAVRIC (4′12″) suffered from through-plane aliasing, ORS-SEMAC and ORS-MAVRIC allowed alias-free imaging in the same scan-times. Conclusion ORS can be used in MSI to limit the selected spatial-spectral region and contribute to metal artifact reduction in clinically feasible scan-times while avoiding slice aliasing. Magn Reson Med 73:233-243, 2015. © 2014 Wiley Periodicals, Inc.
- Publication
Magnetic Resonance in Medicine, 2015, Vol 73, Issue 1, p233
- ISSN
0740-3194
- Publication type
Article
- DOI
10.1002/mrm.25126