| Frequency-offset Cartesian feedback for MRI power amplifier linearization. | |
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MedLine Citation:
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PMID: 20959264 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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High-quality magnetic resonance imaging (MRI) requires precise control of the transmit radio-frequency (RF) field. In parallel excitation applications such as transmit SENSE, high RF power linearity is essential to cancel aliased excitations. In widely-employed class AB power amplifiers, gain compression, cross-over distortion, memory effects, and thermal drift all distort the RF field modulation and can degrade image quality. Cartesian feedback (CF) linearization can mitigate these effects in MRI, if the quadrature mismatch and dc offset imperfections inherent in the architecture can be minimized. In this paper, we present a modified Cartesian feedback technique called "frequency-offset Cartesian feedback" (FOCF) that significantly reduces these problems. In the FOCF architecture, the feedback control is performed at a low intermediate frequency rather than dc, so that quadrature ghosts and dc errors are shifted outside the control bandwidth. FOCF linearization is demonstrated with a variety of typical MRI pulses. Simulation of the magnetization obtained with the Bloch equation demonstrates that high-fidelity RF reproduction can be obtained even with inexpensive class AB amplifiers. Finally, the enhanced RF fidelity of FOCF over CF is demonstrated with actual images obtained in a 1.5 T MRI system. |
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Authors:
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Marta G Zanchi; Pascal Stang; Adam Kerr; John M Pauly; Greig C Scott |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural Date: 2010-10-18 |
Journal Detail:
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Title: IEEE transactions on medical imaging Volume: 30 ISSN: 1558-254X ISO Abbreviation: IEEE Trans Med Imaging Publication Date: 2011 Feb |
Date Detail:
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Created Date: 2011-02-04 Completed Date: 2011-05-24 Revised Date: 2012-04-24 |
Medline Journal Info:
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Nlm Unique ID: 8310780 Medline TA: IEEE Trans Med Imaging Country: United States |
Other Details:
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Languages: eng Pagination: 512-22 Citation Subset: IM |
Affiliation:
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LitePoint Corporation, CA 94085, USA. mgzanchi@stanfordalumni.org |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Feedback Fourier Analysis Image Processing, Computer-Assisted / methods* Magnetic Resonance Imaging / instrumentation*, methods* Phantoms, Imaging Signal Processing, Computer-Assisted* |
| Grant Support | |
ID/Acronym/Agency:
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R01 EB008108-03/EB/NIBIB NIH HHS; R01 EB008108-05/EB/NIBIB NIH HHS; R01EB008108/EB/NIBIB NIH HHS; R21 EB007715-03/EB/NIBIB NIH HHS; R21EB007715/EB/NIBIB NIH HHS; R33 CA118276-03/CA/NCI NIH HHS; R33CA118276/CA/NCI NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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