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Communication

Gradient-Modulated PETRA MRI

by
Naoharu Kobayashi
*,
Ute Goerke
,
Luning Wang
,
Jutta Ellermann
,
Gregory J. Metzger
and
Michael Garwood
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, 2021 Sixth Street SE, Minneapolis, MN, USA
*
Author to whom correspondence should be addressed.
Tomography 2015, 1(2), 85-90; https://doi.org/10.18383/j.tom.2015.00157
Submission received: 8 September 2015 / Revised: 11 October 2015 / Accepted: 10 November 2015 / Published: 1 December 2015

Abstract

Image blurring that results from off-resonance and fast T2* signal decay is a common issue in radial ultrashort echo time magnetic resonance imaging (MRI) sequences. One solution is to use a higher readout bandwidth, but this may be impractical for some techniques such as pointwise-encoding time reduction with radial acquisition (PETRA), which is a hybrid method of zero echo time and single-point imaging techniques. Specifically, PETRA has severe specific absorption rate (SAR) and radiofrequency (RF) pulse peak power limitations when using higher bandwidths in human measurements. In this study, we introduce gradient modulation (GM) to PETRA to reduce image-blurring artifacts while keeping SAR and RF peak power low. GM-PETRA tolerance to image blurring was evaluated in simulations and experiments by comparison with the conventional PETRA technique. We performed inner ear imaging of a healthy subject at 7 T. GM-PETRA showed significantly less image blurring as a result of off-resonance and fast T2* signal decay compared to PETRA. In in vivo imaging, GM-PETRA nicely captured complex structures of the inner ear such as the cochlea and semicircular canals. GM can improve PETRA image quality and mitigate SAR and RF peak power limitations without special hardware modification in clinical scanners.
Keywords: magnetic resonance imaging; ultrashort echo time; pointwise-encoding time reduction with radial acquisition; image blurring; off-resonance magnetic resonance imaging; ultrashort echo time; pointwise-encoding time reduction with radial acquisition; image blurring; off-resonance

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MDPI and ACS Style

Kobayashi, N.; Goerke, U.; Wang, L.; Ellermann, J.; Metzger, G.J.; Garwood, M. Gradient-Modulated PETRA MRI. Tomography 2015, 1, 85-90. https://doi.org/10.18383/j.tom.2015.00157

AMA Style

Kobayashi N, Goerke U, Wang L, Ellermann J, Metzger GJ, Garwood M. Gradient-Modulated PETRA MRI. Tomography. 2015; 1(2):85-90. https://doi.org/10.18383/j.tom.2015.00157

Chicago/Turabian Style

Kobayashi, Naoharu, Ute Goerke, Luning Wang, Jutta Ellermann, Gregory J. Metzger, and Michael Garwood. 2015. "Gradient-Modulated PETRA MRI" Tomography 1, no. 2: 85-90. https://doi.org/10.18383/j.tom.2015.00157

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