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Analysis of the Precision of Variable Flip Angle T-1 Mapping with Emphasis on the Noise Propagated from RF Transmit Field Maps

Lee, Y; Callaghan, MF; Nagy, Z; (2017) Analysis of the Precision of Variable Flip Angle T-1 Mapping with Emphasis on the Noise Propagated from RF Transmit Field Maps. Frontiers in Neuroscience , 11 , Article 106. 10.3389/fnins.2017.00106. Green open access

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Abstract

In magnetic resonance imaging, precise measurements of longitudinal relaxation time (T1) is crucial to acquire useful information that is applicable to numerous clinical and neuroscience applications. In this work, we investigated the precision of T1 relaxation time as measured using the variable flip angle method with emphasis on the noise propagated from radiofrequency transmit field (B+1B1+) measurements. The analytical solution for T1 precision was derived by standard error propagation methods incorporating the noise from the three input sources: two spoiled gradient echo (SPGR) images and a B+1B1+ map. Repeated in vivo experiments were performed to estimate the total variance in T1 maps and we compared these experimentally obtained values with the theoretical predictions to validate the established theoretical framework. Both the analytical and experimental results showed that variance in the B+1B1+ map propagated comparable noise levels into the T1 maps as either of the two SPGR images. Improving precision of the B+1B1+ measurements significantly reduced the variance in the estimated T1 map. The variance estimated from the repeatedly measured in vivo T1 maps agreed well with the theoretically-calculated variance in T1 estimates, thus validating the analytical framework for realistic in vivo experiments. We concluded that for T1 mapping experiments, the error propagated from the B+1B1+ map must be considered. Optimizing the SPGR signals while neglecting to improve the precision of the B+1B1+ map may result in grossly overestimating the precision of the estimated T1 values.

Type: Article
Title: Analysis of the Precision of Variable Flip Angle T-1 Mapping with Emphasis on the Noise Propagated from RF Transmit Field Maps
Open access status: An open access version is available from UCL Discovery
DOI: 10.3389/fnins.2017.00106
Publisher version: http://dx.doi.org/10.3389/fnins.2017.00106
Language: English
Additional information: © 2017 Lee, Callaghan and Nagy. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Keywords: B-1(+) map, T-1 map, error propagation, uncertainty, precision, variable flip angle, lattice relaxation-times, high-resolution t-1, radiofrequency field, steady-state, spin-lattice, magnetic-resonance, ernst equation, accuracy, brain, flash
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Imaging Neuroscience
URI: https://discovery.ucl.ac.uk/id/eprint/1550270
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