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Exploring the bandwidth limits of ZTE imaging: Spatial response, out-of-band signals, and noise propagation


Weiger, Markus; Brunner, David O; Tabbert, Martin; Pavan, Matteo; Schmid, Thomas; Pruessmann, Klaas P (2015). Exploring the bandwidth limits of ZTE imaging: Spatial response, out-of-band signals, and noise propagation. Magnetic Resonance in Medicine, 74(5):1236-1247.

Abstract

Purpose: Zero echo time (ZTE) imaging with single-pulse excitation is a fast, robust, and silent three-dimensional (3D) method for MRI of short T2 tissues. In this technique, algebraic reconstruction serves to fill gaps in the center of k-space due to finite acquisition dead time. The purpose of this study was to investigate the effect of this operation on depiction characteristics, noise behavior, and achievable bandwidth.
Methods: The spatial response function (SRF) and noise covariance resulting from ZTE reconstruction were studied using formal analysis, simulations, and phantom experiments.
Results: Three prominent limiting phenomena were identified: SRF behavior within the field of view, heightened sensitivity to out-of-band signal sources, and noise amplification. The related errors all appear as image distortions of low spatial frequency and are strongly attenuated upon the transition from one-dimensional projections to 3D image data. Relying on these observations, ZTE imaging was accomplished with a previously unreached gap size, permitting the depiction of a solid sample with T2 ≈ 25 µs at a bandwidth of 500 kHz.
Conclusion: The tightest bandwidth limits in ZTE arise from background signal and radiofrequency (RF) switching transients. Significant advances in ZTE performance will be afforded by faster transmit-receive (T/R) switching with negligible transients and RF coils free of background signal.

Abstract

Purpose: Zero echo time (ZTE) imaging with single-pulse excitation is a fast, robust, and silent three-dimensional (3D) method for MRI of short T2 tissues. In this technique, algebraic reconstruction serves to fill gaps in the center of k-space due to finite acquisition dead time. The purpose of this study was to investigate the effect of this operation on depiction characteristics, noise behavior, and achievable bandwidth.
Methods: The spatial response function (SRF) and noise covariance resulting from ZTE reconstruction were studied using formal analysis, simulations, and phantom experiments.
Results: Three prominent limiting phenomena were identified: SRF behavior within the field of view, heightened sensitivity to out-of-band signal sources, and noise amplification. The related errors all appear as image distortions of low spatial frequency and are strongly attenuated upon the transition from one-dimensional projections to 3D image data. Relying on these observations, ZTE imaging was accomplished with a previously unreached gap size, permitting the depiction of a solid sample with T2 ≈ 25 µs at a bandwidth of 500 kHz.
Conclusion: The tightest bandwidth limits in ZTE arise from background signal and radiofrequency (RF) switching transients. Significant advances in ZTE performance will be afforded by faster transmit-receive (T/R) switching with negligible transients and RF coils free of background signal.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Biomedical Engineering
Dewey Decimal Classification:170 Ethics
610 Medicine & health
Language:English
Date:2015
Deposited On:19 Jan 2015 14:34
Last Modified:05 Apr 2016 18:44
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0740-3194
Publisher DOI:https://doi.org/10.1002/mrm.25509

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