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Fast quantitative MRI using controlled saturation magnetization transfer
PURPOSE: This study demonstrates magnetization transfer (MT) effects directly affect relaxometry measurements and develops a framework that allows single‐pool models to be valid in 2‐pool MT systems. METHODS: A theoretical framework is developed in which a 2‐pool MT system effectively behaves as a s...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6492254/ https://www.ncbi.nlm.nih.gov/pubmed/30257044 http://dx.doi.org/10.1002/mrm.27442 |
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author | A.G. Teixeira, Rui Pedro Malik, Shaihan J. Hajnal, Joseph V. |
author_facet | A.G. Teixeira, Rui Pedro Malik, Shaihan J. Hajnal, Joseph V. |
author_sort | A.G. Teixeira, Rui Pedro |
collection | PubMed |
description | PURPOSE: This study demonstrates magnetization transfer (MT) effects directly affect relaxometry measurements and develops a framework that allows single‐pool models to be valid in 2‐pool MT systems. METHODS: A theoretical framework is developed in which a 2‐pool MT system effectively behaves as a single‐pool if the RMS RF magnetic field ([Formula: see text] {\text{B}}_{1}^{{{\text{rms}}}}) is kept fixed across all measurements. A practical method for achieving controlled saturation magnetization transfer (CSMT) using multiband RF pulses is proposed. Numerical, Phantom, and in vivo validations were performed directly comparing steady state (SS) estimation approaches that under correct single‐pool assumptions would be expected to vary in precision but not accuracy. RESULTS: Numerical simulations predict single‐pool estimates obtained from MT model generated data are not consistent for different SS estimation methods, and a systematic underestimation of T(2) is expected. Neither effect occurs under the proposed CSMT approach. Both phantom and in vivo experiments corroborate the numerical predictions. Experimental data highlights that even when using the same relaxometry method, different estimates are obtained depending on which combination of flip angles (FAs) and TRs are used if the CSMT approach is not used. Using CSMT, stable measurements of both T(1) and T(2) are obtained. The measured T(1) [Formula: see text]) depends on [Formula: see text] {\text{B}}_{1}^{{{\text{rms}}}}, which is therefore an important parameter to specify. CONCLUSION: This work demonstrates that conventional single pool relaxometry, which is highly efficient for human studies, results in unreliable parameter estimates in biological tissues because of MT effects. The proposed CSMT framework is shown to allow single‐pool assumptions to be valid, enabling reliable and efficient quantitative imaging to be performed. |
format | Online Article Text |
id | pubmed-6492254 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-64922542019-05-07 Fast quantitative MRI using controlled saturation magnetization transfer A.G. Teixeira, Rui Pedro Malik, Shaihan J. Hajnal, Joseph V. Magn Reson Med Full Papers—Imaging Methodology PURPOSE: This study demonstrates magnetization transfer (MT) effects directly affect relaxometry measurements and develops a framework that allows single‐pool models to be valid in 2‐pool MT systems. METHODS: A theoretical framework is developed in which a 2‐pool MT system effectively behaves as a single‐pool if the RMS RF magnetic field ([Formula: see text] {\text{B}}_{1}^{{{\text{rms}}}}) is kept fixed across all measurements. A practical method for achieving controlled saturation magnetization transfer (CSMT) using multiband RF pulses is proposed. Numerical, Phantom, and in vivo validations were performed directly comparing steady state (SS) estimation approaches that under correct single‐pool assumptions would be expected to vary in precision but not accuracy. RESULTS: Numerical simulations predict single‐pool estimates obtained from MT model generated data are not consistent for different SS estimation methods, and a systematic underestimation of T(2) is expected. Neither effect occurs under the proposed CSMT approach. Both phantom and in vivo experiments corroborate the numerical predictions. Experimental data highlights that even when using the same relaxometry method, different estimates are obtained depending on which combination of flip angles (FAs) and TRs are used if the CSMT approach is not used. Using CSMT, stable measurements of both T(1) and T(2) are obtained. The measured T(1) [Formula: see text]) depends on [Formula: see text] {\text{B}}_{1}^{{{\text{rms}}}}, which is therefore an important parameter to specify. CONCLUSION: This work demonstrates that conventional single pool relaxometry, which is highly efficient for human studies, results in unreliable parameter estimates in biological tissues because of MT effects. The proposed CSMT framework is shown to allow single‐pool assumptions to be valid, enabling reliable and efficient quantitative imaging to be performed. John Wiley and Sons Inc. 2018-09-14 2019-02 /pmc/articles/PMC6492254/ /pubmed/30257044 http://dx.doi.org/10.1002/mrm.27442 Text en © 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Full Papers—Imaging Methodology A.G. Teixeira, Rui Pedro Malik, Shaihan J. Hajnal, Joseph V. Fast quantitative MRI using controlled saturation magnetization transfer |
title | Fast quantitative MRI using controlled saturation magnetization transfer |
title_full | Fast quantitative MRI using controlled saturation magnetization transfer |
title_fullStr | Fast quantitative MRI using controlled saturation magnetization transfer |
title_full_unstemmed | Fast quantitative MRI using controlled saturation magnetization transfer |
title_short | Fast quantitative MRI using controlled saturation magnetization transfer |
title_sort | fast quantitative mri using controlled saturation magnetization transfer |
topic | Full Papers—Imaging Methodology |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6492254/ https://www.ncbi.nlm.nih.gov/pubmed/30257044 http://dx.doi.org/10.1002/mrm.27442 |
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