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Šiurytė P, Tourais J, Zhang Y, Coletti C, van de Steeg-Henzen C, Mandija S, Tao Q, Henningsson M, Weingärtner S. Preparation-based B 1 + mapping in the heart using Bloch-Siegert shifts. Magn Reson Med 2024; 92:2596-2606. [PMID: 39044620 DOI: 10.1002/mrm.30232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 06/11/2024] [Accepted: 07/10/2024] [Indexed: 07/25/2024]
Abstract
PURPOSE To develop and evaluate a robust cardiacB 1 + $$ {\mathrm{B}}_1^{+} $$ mapping sequence at 3 T, using Bloch-Siegert shift (BSS)-based preparations. METHODS A longitudinal magnetization preparation module was designed to encode| B 1 + | $$ \mid {\mathrm{B}}_1^{+}\mid $$ . After magnetization tip-down, off-resonant Fermi pulses, placed symmetrically around two refocusing pulses, induced BSS, followed by tipping back of the magnetization. Bloch simulations were used to optimize refocusing pulse parameters and to assess the mapping sensitivity. Relaxation-inducedB 1 + $$ {\mathrm{B}}_1^{+} $$ error was simulated for variousT 1 $$ {\mathrm{T}}_1 $$ /T 2 $$ {\mathrm{T}}_2 $$ times. The effective mapping range was determined in phantom experiments, and| B 1 + | $$ \mid {\mathrm{B}}_1^{+}\mid $$ maps were compared to the conventional BSS method and subadiabatic hyperbolic-secant 8 (HS8) pulse-sensitized method. CardiacB 1 + $$ {\mathrm{B}}_1^{+} $$ maps were acquired in healthy subjects, and evaluated for repeatability and imaging plane intersection consistency. The technique was modified for three-dimensional (3D) acquisition of the whole heart in a single breath-hold, and compared to two-dimensional (2D) acquisition. RESULTS Simulations indicate that the proposed preparation can be tailored to achieve high mapping sensitivity across variousB 1 + $$ {\mathrm{B}}_1^{+} $$ ranges, with maximum sensitivity at the upperB 1 + $$ {\mathrm{B}}_1^{+} $$ range.T 1 $$ {\mathrm{T}}_1 $$ /T 2 $$ {\mathrm{T}}_2 $$ -induced bias did not exceed 5.2% $$ \% $$ . Experimentally reproducedB 1 + $$ {\mathrm{B}}_1^{+} $$ sensitization closely matched simulations forB 1 + ≥ 0 . 3 B 1 , max + $$ {\mathrm{B}}_1^{+}\ge 0.3{\mathrm{B}}_{1,\max}^{+} $$ (mean difference 0.031± $$ \pm $$ 0.022, compared to 0.018± $$ \pm $$ 0.025 in the HS8-sensitized method), and showed 20-fold reduction in the standard deviation of repeated scans, compared with conventional BSSB 1 + $$ {\mathrm{B}}_1^{+} $$ mapping, and an equivalent 2-fold reduction compared with HS8-sensitization. Robust cardiacB 1 + $$ {\mathrm{B}}_1^{+} $$ map quality was obtained, with an average test-retest variability of 0.027± $$ \pm $$ 0.043 relative to normalizedB 1 + $$ {\mathrm{B}}_1^{+} $$ magnitude, and plane intersection bias of 0.052± $$ \pm $$ 0.031. 3D acquisitions showed good agreement with 2D scans (mean absolute deviation 0.055± $$ \pm $$ 0.061). CONCLUSION BSS-based preparations enable robust and tailorable 2D/3D cardiacB 1 + $$ {\mathrm{B}}_1^{+} $$ mapping at 3 T in a single breath-hold.
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Affiliation(s)
- Paulina Šiurytė
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Joao Tourais
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Yi Zhang
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Chiara Coletti
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | | | - Stefano Mandija
- Department of Radiotherapy, Division of Imaging & Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Qian Tao
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Markus Henningsson
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
| | - Sebastian Weingärtner
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
- HollandPTC, Delft, The Netherlands
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Widmaier M, Kaiser A, Baup S, Wenz D, Pierzchala K, Xiao Y, Huang Z, Jiang Y, Xin L. Fast 3D 31P B 1 + mapping with a weighted stack of spiral trajectory at 7 Tesla. ARXIV 2024:arXiv:2406.18426v1. [PMID: 38979490 PMCID: PMC11230352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Purpose Phosphorus Magnetic Resonance Spectroscopy (31P MRS) enables non-invasive assessment of energy metabolism, yet its application is hindered by sensitivity limitations. To overcome this, often high magnetic fields are used, leading to challenges such as spatialB 1 + inhomogeneity and therefore the need for accurate flip angle determination in accelerated acquisitions with short repetition timesT R ) . In response to these challenges, we propose a novel shortT R and look-up table-based Double-Angle Method for fast 3D 31PB 1 + mapping (fDAM). Methods Our method incorporates 3D weighted stack of spiral gradient echo acquisitions and a frequency-selective pulse to enable efficientB 1 + mapping based on the phosphocreatine signal at 7T. Protocols were optimised using simulations and validated through phantom experiments. The method was validated in phantom experiments and skeletal muscle applications using a birdcage 1H/31P volume coil. Results The results of fDAM were compared to the classical DAM (cDAM). A good correlation (r=0.94) was obtained between the twoB 1 + maps. A 3D 31PB 1 + mapping in the human calf muscle was achieved in about 10 min using a birdcage volume coil, with a 20% extended coverage relative to that of the cDAM (24 min). fDAM also enabled the first full brain coverage 31P 3DB 1 + mapping in approx. 10 min using a 1 Tx/ 32 Rx coil. Conclusion fDAM is an efficient method for 31P 3DB 1 + mapping, showing promise for future applications in rapid 31P MRSI.
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Affiliation(s)
- Mark Widmaier
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
- Laboratory of functional and metabolic imaging, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Antonia Kaiser
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Salome Baup
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Daniel Wenz
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Katarzyna Pierzchala
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ying Xiao
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
- Laboratory of functional and metabolic imaging, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Zhiwei Huang
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Yun Jiang
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Lijing Xin
- CIBM Center for Biomedical Imaging, Switzerland
- Animal Imaging and Technology, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Physics, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
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Gupta A. Cardiac 31P MR spectroscopy: development of the past five decades and future vision-will it be of diagnostic use in clinics? Heart Fail Rev 2023; 28:485-532. [PMID: 36427161 DOI: 10.1007/s10741-022-10287-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/16/2022] [Indexed: 11/27/2022]
Abstract
In the past five decades, the use of the magnetic resonance (MR) technique for cardiovascular diseases has engendered much attention and raised the opportunity that the technique could be useful for clinical applications. MR has two arrows in its quiver: One is magnetic resonance imaging (MRI), and the other is magnetic resonance spectroscopy (MRS). Non-invasively, highly advanced MRI provides unique and profound information about the anatomical changes of the heart. Excellently developed MRS provides irreplaceable and insightful evidence of the real-time biochemistry of cardiac metabolism of underpinning diseases. Compared to MRI, which has already been successfully applied in routine clinical practice, MRS still has a long way to travel to be incorporated into routine diagnostics. Considering the exceptional potential of 31P MRS to measure the real-time metabolic changes of energetic molecules qualitatively and quantitatively, how far its powerful technique should be waited before a successful transition from "bench-to-bedside" is enticing. The present review highlights the seminal studies on the chronological development of cardiac 31P MRS in the past five decades and the future vision and challenges to incorporating it for routine diagnostics of cardiovascular disease.
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Affiliation(s)
- Ashish Gupta
- Centre of Biomedical Research, SGPGIMS Campus, Lucknow, 226014, India.
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Vaeggemose M, Schulte RF, Laustsen C. Clinically feasible B 1 field correction for multi-organ sodium imaging at 3 T. NMR IN BIOMEDICINE 2023; 36:e4835. [PMID: 36115017 PMCID: PMC10078323 DOI: 10.1002/nbm.4835] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 06/15/2023]
Abstract
Sodium MRI allows the non-invasive quantification of intra-organ sodium concentration. RF inhomogeneity introduces uncertainty in this estimated concentration. B1 field corrections can be used to overcome some of these limitations. However, the low signal-to-noise ratio in sodium MRI makes accurate B1 mapping in reasonable scan times challenging. The study aims to evaluate Bloch-Siegert off-resonance (BLOSI) B1 field correction for sodium MRI using a 3D Fermat looped, orthogonally encoded trajectories (FLORET) read-out trajectory. We propose a clinically feasible B1 field map correction method for sodium imaging at 3 T, evaluating five healthy subjects' brain, heart blood, kidneys, and thigh muscle. We scanned the subjects twice for repeatability measures and used sodium phantoms to determine organ total sodium concentration. Conventional proton scans were compared with sodium images for organ structural integrity. The BLOSI approach based on the 3D FLORET read-out trajectory was used in B1 field correction and 3D density-adapted radial acquisition for sodium imaging. Results indicate improvements in sodium imaging based on B1 field correction in a clinically feasible protocol. Improvements are determined in all organs by enhanced anatomical representation, organ homogeneity, and an increase in the total sodium concentration after applying a B1 field correction. The proposed BLOSI-based B1 field correction using a 3D FLORET read-out trajectory is clinically feasible for sodium imaging, which is shown in the brain, heart, kidney, and thigh muscle. This supports using fast B1 field mapping in the clinical setting.
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Affiliation(s)
- Michael Vaeggemose
- GE HealthcareBrondbyDenmark
- MR Research Centre, Department of Clinical MedicineAarhus UniversityAarhusDenmark
| | | | - Christoffer Laustsen
- MR Research Centre, Department of Clinical MedicineAarhus UniversityAarhusDenmark
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Bidinosti CP, Tastevin G, Nacher PJ. Generating accurate tip angles for NMR outside the rotating-wave approximation. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 345:107306. [PMID: 36434882 DOI: 10.1016/j.jmr.2022.107306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
The generation of accurate tip angles is critical for many applications of nuclear magnetic resonance. In low static field, with a linear rather than circular polarized rf field, the rotating-wave approximation may no longer hold and significant deviations from expected trajectories on the Bloch sphere can occur. For rectangular rf pulses, the effects depend strongly on the phase of the rf field and can be further compounded by transients at the start and end of the pulse. The desired terminus can be still be achieved, however, through the application of a phase-dependent Bloch-Siegert shift and appropriate consideration of pulse timings. For suitably shaped rf pulses, the Bloch-Siegert shift is largely phase independent, but its magnitude can vary significantly depending on details of the pulse shape as well as the characteristics of the rf coil circuit. We present numerical simulations and low-field NMR experiments with 1H and 3He that demonstrate several main consequences and accompanying strategies that one should consider when wanting to generate accurate tip angles outside the validity of the rotating-wave approximation and in low static field.
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Affiliation(s)
| | - Geneviève Tastevin
- Laboratoire Kastler Brossel, ENS-Université PSL, CNRS, Sorbonne Université, Collège de France, 24 rue Lhomond, 75005 Paris, France
| | - Pierre-Jean Nacher
- Laboratoire Kastler Brossel, ENS-Université PSL, CNRS, Sorbonne Université, Collège de France, 24 rue Lhomond, 75005 Paris, France.
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Guo R, Weingärtner S, Šiurytė P, T Stoeck C, Füetterer M, E Campbell-Washburn A, Suinesiaputra A, Jerosch-Herold M, Nezafat R. Emerging Techniques in Cardiac Magnetic Resonance Imaging. J Magn Reson Imaging 2021; 55:1043-1059. [PMID: 34331487 DOI: 10.1002/jmri.27848] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 07/08/2021] [Accepted: 07/09/2021] [Indexed: 11/10/2022] Open
Abstract
Cardiovascular disease is the leading cause of death and a significant contributor of health care costs. Noninvasive imaging plays an essential role in the management of patients with cardiovascular disease. Cardiac magnetic resonance (MR) can noninvasively assess heart and vascular abnormalities, including biventricular structure/function, blood hemodynamics, myocardial tissue composition, microstructure, perfusion, metabolism, coronary microvascular function, and aortic distensibility/stiffness. Its ability to characterize myocardial tissue composition is unique among alternative imaging modalities in cardiovascular disease. Significant growth in cardiac MR utilization, particularly in Europe in the last decade, has laid the necessary clinical groundwork to position cardiac MR as an important imaging modality in the workup of patients with cardiovascular disease. Although lack of availability, limited training, physician hesitation, and reimbursement issues have hampered widespread clinical adoption of cardiac MR in the United States, growing clinical evidence will ultimately overcome these challenges. Advances in cardiac MR techniques, particularly faster image acquisition, quantitative myocardial tissue characterization, and image analysis have been critical to its growth. In this review article, we discuss recent advances in established and emerging cardiac MR techniques that are expected to strengthen its capability in managing patients with cardiovascular disease. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 1.
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Affiliation(s)
- Rui Guo
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Sebastian Weingärtner
- Department of Imaging Physics, Magnetic Resonance Systems Lab, Delft University of Technology, Delft, The Netherlands
| | - Paulina Šiurytė
- Department of Imaging Physics, Magnetic Resonance Systems Lab, Delft University of Technology, Delft, The Netherlands
| | - Christian T Stoeck
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Maximilian Füetterer
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Adrienne E Campbell-Washburn
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Avan Suinesiaputra
- Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, UK
| | - Michael Jerosch-Herold
- Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Reza Nezafat
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
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Ruhm L, Dorst J, Avdievitch N, Wright AM, Henning A. 3D 31 P MRSI of the human brain at 9.4 Tesla: Optimization and quantitative analysis of metabolic images. Magn Reson Med 2021; 86:2368-2383. [PMID: 34219281 DOI: 10.1002/mrm.28891] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 05/14/2021] [Accepted: 05/28/2021] [Indexed: 12/16/2022]
Abstract
PURPOSE To present 31 P whole brain MRSI with a high spatial resolution to probe quantitative tissue analysis of 31 P MRSI at an ultrahigh field strength of 9.4 Tesla. METHODS The study protocol included a 31 P MRSI measurement with an effective resolution of 2.47 mL. For SNR optimization, the nuclear Overhauser enhancement at 9.4 Tesla was investigated. A sensitivity correction was achieved by applying a low rank approximation of the γ-adenosine triphosphate signal. Group analysis and regression on individual volunteers were performed to investigate quantitative concentration differences between different tissue types. RESULTS Differences in gray and white matter tissue 31 P concentrations could be investigated for 12 different 31 P resonances. In addition, the first highly resolved quantitative MRSI images measured at B0 = 9.4 Tesla of 31 P detectable metabolites with high SNR could be presented. CONCLUSION With an ultrahigh field strength B0 = 9.4 Tesla, 31 P MRSI moves further toward quantitative metabolic imaging, and subtle differences in concentrations between different tissue types can be detected.
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Affiliation(s)
- Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tübingen, Germany
| | - Johanna Dorst
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tübingen, Germany
| | - Nikolai Avdievitch
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Andrew Martin Wright
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, Eberhard-Karls University of Tübingen, Germany
| | - Anke Henning
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.,Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, USA
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van Houtum Q(, Mohamed Hoesein F(, Verhoeff J(, van Rossum P(, van Lindert A(, van der Velden T(, van der Kemp W(, Klomp D(, Arteaga de Castro C(. Feasibility of 31 P spectroscopic imaging at 7 T in lung carcinoma patients. NMR IN BIOMEDICINE 2021; 34:e4204. [PMID: 31736167 PMCID: PMC8244006 DOI: 10.1002/nbm.4204] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 09/20/2019] [Accepted: 09/26/2019] [Indexed: 05/13/2023]
Abstract
Currently, it is difficult to predict effective therapy response to molecular therapies for the treatment of lung cancer based solely on anatomical images. 31 P MR spectroscopic imaging could provide as a non-invasive method to monitor potential biomarkers for early therapy evaluation, a necessity to improve personalized care and reduce cost. However, surface coils limit the imaging volume in conventional 31 P MRSI. High-energetic adiabatic RF pulses are required to achieve flip angle homogeneity but lead to high SAR. Birdcage coils permit use of conventional amplitude modulated pulses, even over large FOV, potentially decreasing overall SAR massively. Here, we investigate the feasibility of 3D 31 P MRSI at 7 T in lung carcinoma patients using an integrated 31 P birdcage body coil in combination with either a dual-coil or a 16-channel receiver. Simulations showed a maximum decrease in SNR per unit of time of 8% for flip angle deviations in short TR low flip-angle excitation 3D CSI. The minimal SNR loss allowed for fast 3D CSI without time-consuming calibration steps (>10:00 min.). 31 P spectra from four lung carcinoma patients were acquired within 29:00 minutes and with high SNR using both receivers. The latter allowed discrimination of individual phosphodiesters, inorganic phosphate, phosphocreatine and ATP. The receiver array allowed for an increased FOV compared to the dual-coil receiver. 3D 31 P-CSI were acquired successfully in four lung carcinoma patients using the integrated 31 P body coil at ultra-high field. The increased spectral resolution at 7 T allowed differentiation of multiple 31 P metabolites related to phospholipid and energy metabolism. Simulations provide motivation to exclude 31 P B1 calibrations, potentially decreasing total scan duration. Employing large receiver arrays improves the field of view allowing for full organ coverage. 31 P MRSI is feasible in lung carcinoma patients and has potential as a non-invasive method for monitoring personalized therapy response in lung tumors.
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Bashir A, Zhang J, Denney TS. Creatine kinase rate constant in the human heart at 7T with 1D-ISIS/2D CSI localization. PLoS One 2020; 15:e0229933. [PMID: 32191723 PMCID: PMC7081998 DOI: 10.1371/journal.pone.0229933] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 02/17/2020] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Creatine Kinase (CK) reaction plays an important role in energy metabolism and estimate of its reaction rate constant in heart provides important insight into cardiac energetics. Fast saturation transfer method ([Formula: see text] nominal) to measure CK reaction rate constant (kf) was previously demonstrated in open chest swine hearts. The goal of this work is to further develop this method for measuring the kf in human myocardium at 7T. [Formula: see text] approach is combined with 1D-ISIS/2D-CSI for in vivo spatial localization and myocardial CK forward rate constant was then measured in 7 volunteers at 7T. METHODS [Formula: see text] method uses two partially relaxed saturation transfer (ST) spectra and correction factor to determine CK rate constant. Correction factor is determined by numerical simulation of Bloch McConnell equations using known spin and experimental parameters. Optimal parameters and error estimate in calculation of CK reaction rate constant were determined by simulations. The technique was validated in calf muscles by direct comparison with saturation transfer measurements. [Formula: see text] pulse sequence was incorporated with 1D-image selected in vivo spectroscopy, combined with 2D-chemical shift spectroscopic imaging (1D-ISIS/2D-CSI) for studies in heart. The myocardial CK reaction rate constant was then measured in 7 volunteers. RESULTS Skeletal muscle kf determined by conventional approach and [Formula: see text] approach were the same 0.31 ± 0.02 s-1 and 0.30 ± 0.04 s-1 demonstrating the validity of the technique. Results are reported as mean ± SD. Myocardial CK reaction rate constant was 0.29 ± 0.05 s-1, consistent with previously reported studies. CONCLUSION [Formula: see text] method enables acquisition of 31P saturation transfer MRS under partially relaxed conditions and enables 2D-CSI of kf in myocardium. This work enables applications for in vivo CSI imaging of energetics in heart and other organs in clinically relevant acquisition time.
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Affiliation(s)
- Adil Bashir
- Department of Electrical and Computer Engineering, Auburn University, Auburn, Alabama, United States of America
| | - Jianyi Zhang
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Thomas S. Denney
- Department of Electrical and Computer Engineering, Auburn University, Auburn, Alabama, United States of America
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Purvis LAB, Clarke WT, Biasiolli L, Valkovič L, Robson MD, Rodgers CT. OXSA: An open-source magnetic resonance spectroscopy analysis toolbox in MATLAB. PLoS One 2017; 12:e0185356. [PMID: 28938003 PMCID: PMC5609763 DOI: 10.1371/journal.pone.0185356] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/11/2017] [Indexed: 01/17/2023] Open
Abstract
In vivo magnetic resonance spectroscopy provides insight into metabolism in the human body. New acquisition protocols are often proposed to improve the quality or efficiency of data collection. Processing pipelines must also be developed to use these data optimally. Current fitting software is either targeted at general spectroscopy fitting, or for specific protocols. We therefore introduce the MATLAB-based OXford Spectroscopy Analysis (OXSA) toolbox to allow researchers to rapidly develop their own customised processing pipelines. The toolbox aims to simplify development by: being easy to install and use; seamlessly importing Siemens Digital Imaging and Communications in Medicine (DICOM) standard data; allowing visualisation of spectroscopy data; offering a robust fitting routine; flexibly specifying prior knowledge when fitting; and allowing batch processing of spectra. This article demonstrates how each of these criteria have been fulfilled, and gives technical details about the implementation in MATLAB. The code is freely available to download from https://github.com/oxsatoolbox/oxsa.
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Affiliation(s)
- Lucian A. B. Purvis
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- * E-mail:
| | - William T. Clarke
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Luca Biasiolli
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Ladislav Valkovič
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Matthew D. Robson
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Christopher T. Rodgers
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
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11
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Weingärtner S, Zimmer F, Metzger GJ, Uğurbil K, Van de Moortele PF, Akçakaya M. Motion-robust cardiac B1+ mapping at 3T using interleaved bloch-siegert shifts. Magn Reson Med 2017; 78:670-677. [PMID: 27599782 PMCID: PMC5340643 DOI: 10.1002/mrm.26395] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 07/15/2016] [Accepted: 08/06/2016] [Indexed: 12/25/2022]
Abstract
PURPOSE To develop and evaluate a robust motion-insensitive Bloch-Siegert shift based B1+ mapping method in the heart. METHODS Cardiac Bloch-Siegert B1+ mapping was performed with interleaved positive and negative off-resonance shifts and diastolic spoiled gradient echo imaging in 12 heartbeats. Numerical simulations were performed to study the impact of respiratory motion. The method was compared with three-dimensional (3D) actual flip angle imaging (AFI) and two-dimensional (2D) saturated double angle method (SDAM) in phantom scans. Cardiac B1+ maps of three different views were acquired in six healthy volunteers using Bloch-Siegert and SDAM during breath-hold and free breathing. In vivo maps were evaluated for inter-view consistency using the correlation coefficients of the B1+ profiles along the lines of intersection between the views. RESULTS For the Bloch-Siegert sequence, numerical simulations indicated high similarity between breath-hold and free breathing scans, and phantom results indicated low deviation from the 3D AFI reference (normalized root mean square error [NRMSE] = 2.0%). Increased deviation was observed with 2D SDAM (NRMSE = 5.0%) due to underestimation caused by imperfect excitation slice profiles. Breath-hold and free breathing Bloch-Siegert in vivo B1+ maps were visually comparable with no significant difference in the inter-view consistency (P > 0.36). SDAM showed strongly impaired B1+ map quality during free breathing. Inter-view consistency was significantly lower than with the Bloch-Siegert method (breath-hold: P = 0.014, free breathing: P < 0.0001). CONCLUSION The proposed interleaved Bloch-Siegert sequence enables cardiac B1+ mapping with improved inter-view consistency and high resilience to respiratory motion. Magn Reson Med 78:670-677, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Sebastian Weingärtner
- Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, USA
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
- Computer Assisted Clinical Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
| | - Fabian Zimmer
- Computer Assisted Clinical Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
| | - Gregory J Metzger
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Kâmil Uğurbil
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Mehmet Akçakaya
- Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, USA
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
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12
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Khegai O, Madelin G, Brown R, Parasoglou P. Dynamic phosphocreatine imaging with unlocalized pH assessment of the human lower leg muscle following exercise at 3T. Magn Reson Med 2017; 79:974-980. [PMID: 28560829 DOI: 10.1002/mrm.26728] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 03/29/2017] [Accepted: 03/30/2017] [Indexed: 12/16/2022]
Abstract
PURPOSE To develop a high temporal resolution imaging method that measures muscle-specific phosphocreatine (PCr) resynthesis time constant (τPCr ) and pH changes in muscles of the lower leg following exercise on a clinical 3T MRI scanner. METHODS We developed a frequency-selective 3D non-Cartesian FLORET sequence to measure PCr with 17-mm nominal isotropic resolution (28 mm actual resolution) and 6-s temporal resolution to capture dynamic metabolic muscle activity. The sequence was designed to additionally collect inorganic phosphate spectra for pH quantification, which were localized using sensitivity profiles of individual coil elements. Nineteen healthy volunteers were scanned while performing a plantar flexion exercise on an in-house developed ergometer. Data were acquired with a dual-tuned multichannel coil array that enabled phosphorus imaging and proton localization for muscle segmentation. RESULTS After a 90-s plantar flexion exercise at 0.66 Hz with resistance set to 40% of the maximum voluntary contraction, τPCr was estimated at 22.9 ± 8.8 s (mean ± standard deviation) with statistical coefficient of determination r2 = 0.89 ± 0.05. The corresponding pH values after exercise were in the range of 6.9-7.1 in the gastrocnemius muscle. CONCLUSION The developed technique allows measurement of muscle-specific PCr resynthesis kinetics and pH changes following exercise, with a temporal resolution and accuracy comparable to that of single voxel 31 P-MRS sequences. Magn Reson Med 79:974-980, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Oleksandr Khegai
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Guillaume Madelin
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Ryan Brown
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University School of Medicine, New York, New York, USA.,NYU WIRELESS, Polytechnic Institute of New York University, Brooklyn, New York, USA
| | - Prodromos Parasoglou
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.,Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University School of Medicine, New York, New York, USA
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13
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Principals and clinical applications of magnetic resonance cardiac spectroscopy in heart failure. Heart Fail Rev 2017; 22:491-499. [DOI: 10.1007/s10741-017-9611-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Miller JJ, Cochlin L, Clarke K, Tyler DJ. Weighted averaging in spectroscopic studies improves statistical power. Magn Reson Med 2017; 78:2082-2094. [PMID: 28127795 PMCID: PMC5697704 DOI: 10.1002/mrm.26615] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 12/08/2016] [Accepted: 12/28/2016] [Indexed: 12/19/2022]
Abstract
Purpose In vivo MRS is often characterized by a spectral signal‐to‐noise ratio (SNR) that varies highly between experiments. A common design for spectroscopic studies is to compare the ratio of two spectral peak amplitudes between groups, e.g. individual PCr/γ‐ATP ratios in 31P‐MRS. The uncertainty on this ratio is often neglected. We wished to explore this assumption. Theory The canonical theory for the propagation of uncertainty on the ratio of two spectral peaks and its incorporation in the Frequentist hypothesis testing framework by weighted averaging is presented. Methods Two retrospective re‐analyses of studies comparing spectral peak ratios and one prospective simulation were performed using both the weighted and unweighted methods. Results It was found that propagating uncertainty correctly improved statistical power in all cases considered, which could be used to reduce the number of subjects required to perform an MR study. Conclusion The variability of in vivo spectroscopy data is often accounted for by requiring it to meet an SNR threshold. A theoretically sound propagation of the variable uncertainty caused by quantifying spectra of differing SNR is therefore likely to improve the power of in vivo spectroscopy studies. Magn Reson Med 78:2082–2094, 2017. © 2017 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 Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Affiliation(s)
- Jack J Miller
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK.,Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Lowri Cochlin
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK
| | - Kieran Clarke
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK
| | - Damian J Tyler
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK
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15
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Valkovič L, Chmelík M, Krššák M. In-vivo 31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism. Anal Biochem 2017; 529:193-215. [PMID: 28119063 PMCID: PMC5478074 DOI: 10.1016/j.ab.2017.01.018] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 01/13/2017] [Accepted: 01/19/2017] [Indexed: 01/18/2023]
Abstract
In addition to direct assessment of high energy phosphorus containing metabolite content within tissues, phosphorus magnetic resonance spectroscopy (31P-MRS) provides options to measure phospholipid metabolites and cellular pH, as well as the kinetics of chemical reactions of energy metabolism in vivo. Even though the great potential of 31P-MR was recognized over 30 years ago, modern MR systems, as well as new, dedicated hardware and measurement techniques provide further opportunities for research of human biochemistry. This paper presents a methodological overview of the 31P-MR techniques that can be used for basic, physiological, or clinical research of human skeletal muscle and liver in vivo. Practical issues of 31P-MRS experiments and examples of potential applications are also provided. As signal localization is essential for liver 31P-MRS and is important for dynamic muscle examinations as well, typical localization strategies for 31P-MR are also described.
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Affiliation(s)
- Ladislav Valkovič
- High-field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria; Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, Oxford, United Kingdom; Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia.
| | - Marek Chmelík
- High-field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria; Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria; Institute for Clinical Molecular MRI in Musculoskeletal System, Karl Landsteiner Society, Vienna, Austria
| | - Martin Krššák
- High-field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria; Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria; Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
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16
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Valkovič L, Clarke WT, Purvis LA, Schaller B, Robson MD, Rodgers CT. Adiabatic excitation for 31 P MR spectroscopy in the human heart at 7 T: A feasibility study. Magn Reson Med 2016; 78:1667-1673. [PMID: 28000961 PMCID: PMC5645675 DOI: 10.1002/mrm.26576] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 11/16/2016] [Accepted: 11/18/2016] [Indexed: 11/18/2022]
Abstract
Purpose Phosphorus magnetic resonance spectroscopy (31P‐MRS) provides a unique tool for assessing cardiac energy metabolism, often quantified using the phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio. Surface coils are typically used for excitation for 31P‐MRS, but they create an inhomogeneous excitation field across the myocardium, producing undesirable, spatially varying partial saturation. Therefore, we implemented adiabatic excitation in a 3D chemical shift imaging (CSI) sequence for cardiac 31P‐MRS at 7 Tesla (T). Methods We optimized an adiabatic half passage pulse with bandwidth sufficient to excite PCr and γ‐ATP together. In addition, the CSI sequence was modified to allow interleaved excitation of PCr and γ‐ATP, then 2,3‐DPG, to enable PCr/ATP determination with blood correction. Nine volunteers were scanned at 2 transmit voltages to confirm that measured PCr/ATP was independent of
B1+ (i.e. over the adiabatic threshold). Six septal voxels were evaluated for each volunteer. Results Phantom experiments showed that adiabatic excitation can be reached at the depth of the heart using our pulse. The mean evaluated cardiac PCr/ATP ratio from all 9 volunteers corrected for blood signal was 2.14 ± 0.16. Comparing the two acquisitions with different voltages resulted in a minimal mean difference of
−0.005. Conclusion Adiabatic excitation is possible in the human heart at 7 T, and gives consistent PCr/ATP ratios. Magn Reson Med 78:1667–1673, 2017. © 2016 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 Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Affiliation(s)
- Ladislav Valkovič
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR)University of OxfordOxfordUnited Kingdom
- Department of Imaging MethodsInstitute of Measurement Science, Slovak Academy of SciencesBratislavaSlovakia
| | - William T. Clarke
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR)University of OxfordOxfordUnited Kingdom
| | - Lucian A.B. Purvis
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR)University of OxfordOxfordUnited Kingdom
| | - Benoit Schaller
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR)University of OxfordOxfordUnited Kingdom
| | - Matthew D. Robson
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR)University of OxfordOxfordUnited Kingdom
| | - Christopher T. Rodgers
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR)University of OxfordOxfordUnited Kingdom
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17
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Stäb D, Roessler J, O'Brien K, Hamilton-Craig C, Barth M. ECG Triggering in Ultra-High Field Cardiovascular MRI. ACTA ACUST UNITED AC 2016; 2:167-174. [PMID: 30042961 PMCID: PMC6024401 DOI: 10.18383/j.tom.2016.00193] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cardiac magnetic resonance imaging at ultra-high field (B0 ≥ 7 T) potentially provides improved resolution and new opportunities for tissue characterization. Although an accurate synchronization of the acquisition to the cardiac cycle is essential, electrocardiogram (ECG) triggering at ultra-high field can be significantly impacted by the magnetohydrodynamic (MHD) effect. Blood flow within a static magnetic field induces a voltage, which superimposes the ECG and often affects the recognition of the R-wave. The MHD effect scales with B0 and is particularly pronounced at ultra-high field creating triggering-related image artifacts. Here, we investigated the performance of a conventional 3-lead ECG trigger device and a state-of-the-art trigger algorithm for cardiac ECG synchronization at 7 T. We show that by appropriate subject preparation and by including a learning phase for the R-wave detection outside of the magnetic field, reliable ECG triggering is feasible in healthy subjects at 7 T without additional equipment. Ultra-high field cardiac imaging was performed with the ECG signal and the trigger events recorded in 8 healthy subjects. Despite severe ECG signal distortions, synchronized imaging was successfully performed. Recorded ECG signals, vectorcardiograms, and large consistency in trigger event spacing indicate high accuracy for R-wave detection.
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Affiliation(s)
- Daniel Stäb
- The Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia.,Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany
| | | | | | - Christian Hamilton-Craig
- Richard Slaughter Centre of Excellence in CVMRI, The Prince Charles Hospital, Brisbane, Queensland, Australia
| | - Markus Barth
- The Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia
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18
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Clarke WT, Robson MD, Neubauer S, Rodgers CT. Creatine kinase rate constant in the human heart measured with 3D-localization at 7 tesla. Magn Reson Med 2016; 78:20-32. [PMID: 27579566 PMCID: PMC5484353 DOI: 10.1002/mrm.26357] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 06/26/2016] [Accepted: 07/06/2016] [Indexed: 12/21/2022]
Abstract
PURPOSE We present a new Bloch-Siegert four Angle Saturation Transfer (BOAST) method for measuring the creatine kinase (CK) first-order effective rate constant kf in human myocardium at 7 tesla (T). BOAST combines a variant of the four-angle saturation transfer (FAST) method using amplitude-modulated radiofrequency pulses, phosphorus Bloch-Siegert B1+-mapping to determine the per-voxel flip angles, and nonlinear fitting to Bloch simulations for postprocessing. METHODS Optimal flip angles and repetition time parameters were determined from Monte Carlo simulations. BOAST was validated in the calf muscle of two volunteers at 3T and 7T. The myocardial CK forward rate constant was then measured in 10 volunteers at 7T in 82 min (after 1 H localization). RESULTS BOAST kfCK values were 0.281 ± 0.002 s-1 in the calf and 0.35 ± 0.05 s-1 in myocardium. These are consistent with literature values from lower fields. Using a literature values for adenosine triphosphate concentration, we computed CK flux values of 4.55 ± 1.52 mmol kg-1 s-1 . The sensitive volume for BOAST depends on the B1 inhomogeneity of the transmit coil. CONCLUSION BOAST enables measurement of the CK rate constant in the human heart at 7T, with spatial localization in three dimensions to 5.6 mL voxels, using a 10-cm loop coil. Magn Reson Med 78:20-32, 2017. © 2016 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 Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Affiliation(s)
- William T Clarke
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Matthew D Robson
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Stefan Neubauer
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Christopher T Rodgers
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
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19
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Löring J, van der Kemp WJM, Almujayyaz S, van Oorschot JWM, Luijten PR, Klomp DWJ. Whole-body radiofrequency coil for (31) P MRSI at 7 T. NMR IN BIOMEDICINE 2016; 29:709-20. [PMID: 27037615 DOI: 10.1002/nbm.3517] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 02/05/2016] [Accepted: 02/19/2016] [Indexed: 05/12/2023]
Abstract
Widespread use of ultrahigh-field (31) P MRSI in clinical studies is hindered by the limited field of view and non-uniform radiofrequency (RF) field obtained from surface transceivers. The non-uniform RF field necessitates the use of high specific absorption rate (SAR)-demanding adiabatic RF pulses, limiting the signal-to-noise ratio (SNR) per unit of time. Here, we demonstrate the feasibility of using a body-sized volume RF coil at 7 T, which enables uniform excitation and ultrafast power calibration by pick-up probes. The performance of the body coil is examined by bench tests, and phantom and in vivo measurements in a 7-T MRI scanner. The accuracy of power calibration with pick-up probes is analyzed at a clinical 3-T MR system with a close to identical (1) H body coil integrated at the MR system. Finally, we demonstrate high-quality three-dimensional (31) P MRSI of the human body at 7 T within 5 min of data acquisition that includes RF power calibration. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- J Löring
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - W J M van der Kemp
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | | | - J W M van Oorschot
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - P R Luijten
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - D W J Klomp
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
- MR Coils BV, Zaltbommel, the Netherlands
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