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Nie S, Ratzsch KF, Grage SL, Keller J, Ulrich AS, Lacayo-Pineda J, Wilhelm M. Correlation between Macroscopic Elasticity and Chain Dynamics of Natural Rubber during Vulcanization as Determined by a Unique Rheo-NMR Combination. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Shouliang Nie
- Institute for Technical Chemistry and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | | | - Stephan L. Grage
- Institute of Biological Interfaces (IBG-2) and Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Jonas Keller
- Institute for Technical Chemistry and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Anne S. Ulrich
- Institute of Biological Interfaces (IBG-2) and Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Jorge Lacayo-Pineda
- Research and Development, Continental Reifen Deutschland GmbH, 30419 Hannover, Germany
| | - Manfred Wilhelm
- Institute for Technical Chemistry and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
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2
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Saini BS, Darby JRT, Portnoy S, Sun L, van Amerom J, Lock MC, Soo JY, Holman SL, Perumal SR, Kingdom JC, Sled JG, Macgowan CK, Morrison JL, Seed M. Normal human and sheep fetal vessel oxygen saturations by T2 magnetic resonance imaging. J Physiol 2020; 598:3259-3281. [PMID: 32372463 DOI: 10.1113/jp279725] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 04/30/2020] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Human fetal Doppler ultrasound and invasive blood gas measurements obtained by cordocentesis or at the time of delivery reveal similarities with sheep (an extensively used model for human fetal cardiovascular physiology). Oxygen saturation (SO2 ) measurements in human fetuses have been limited to the umbilical and scalp vessels, providing little information about normal regional SO2 differences in the fetus. Blood T2 MRI relaxometry presents a non-invasive measure of SO2 in the major fetal vessels. This study presents the first in vivo validation of fetal vessel T2 oximetry against the in vitro T2-SO2 relationship using catheterized sheep fetuses and compares the normal SO2 in the major vessels between the human and sheep fetal circulations. Human fetal vessel SO2 by T2 MRI confirms many similarities with the sheep fetal circulation and is able to demonstrate regional differences in SO2 ; in particular the significantly higher SO2 in the left versus right heart. ABSTRACT Blood T2 magnetic resonance imaging (MRI) relaxometry non-invasively measures oxygen saturation (SO2 ) in major vessels but has not been validated in fetuses in vivo. We compared the blood T2-SO2 relationship in vitro (tubes) and in vivo (vessels) in sheep, and measured SO2 across the normal human and sheep fetal circulations by T2. Singleton pregnant ewes underwent surgery to implant vascular catheters. In vitro and in vivo sheep blood T2 measurements were related to corresponding SO2 measured using a blood gas analyser, as well as relating T2 and SO2 of human fetal blood in vitro. MRI oximetry was performed in the major vessels of 30 human fetuses at 36 weeks (term, 40 weeks) and 10 fetal sheep (125 days; term, 150 days). The fidelity of in vivo fetal T2 oximetry was confirmed through comparison of in vitro and in vivo sheep blood T2-SO2 relationships (P = 0.1). SO2 was similar between human and sheep fetuses, as was the fetal oxygen extraction fraction (human, 33 ± 11%; sheep, 34 ± 7%; P = 0.798). The presence of streaming in the human fetal circulation was demonstrated by the SO2 gradient between the ascending aorta (68 ± 10%) and the main pulmonary artery (49 ± 9%; P < 0.001). Human and sheep fetal vessel MRI oximetry based on T2 is a validated approach that confirms the presence of streaming of umbilical venous blood towards the heart and brain. Streaming is important in ensuring oxygen delivery to these organs and its disruption may have important implications for organ development, especially in conditions such as congenital heart disease and fetal growth restriction.
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Affiliation(s)
- Brahmdeep S Saini
- Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Division of Cardiology, The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada
| | - Jack R T Darby
- Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, 5000, Australia
| | - Sharon Portnoy
- Translational Medicine, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada
| | - Liqun Sun
- Division of Cardiology, The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada
| | - Joshua van Amerom
- Division of Cardiology, The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada
| | - Mitchell C Lock
- Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, 5000, Australia
| | - Jia Yin Soo
- Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, 5000, Australia
| | - Stacey L Holman
- Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, 5000, Australia
| | - Sunthara R Perumal
- Preclinical Imaging and Research Laboratories, South Australian Health and Medical Research Institute, Adelaide, South Australia, 5086, Australia
| | - John C Kingdom
- Department of Obstetrics and Gynaecology, Maternal-Fetal Medicine, Mount Sinai Hospital, Toronto, Ontario, M5G 1X5, Canada.,Department of Obstetrics and Gynaecology, University of Toronto, Toronto, Ontario, M5G 1E2, Canada
| | - John G Sled
- Translational Medicine, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, M5G 1L7, Canada
| | - Christopher K Macgowan
- Translational Medicine, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, M5G 1L7, Canada
| | - Janna L Morrison
- Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, 5000, Australia
| | - Mike Seed
- Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Division of Cardiology, The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada.,Department of Obstetrics and Gynaecology, University of Toronto, Toronto, Ontario, M5G 1E2, Canada
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3
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Cavalli F, Pfeifer C, Arens L, Barner L, Wilhelm M. Analysis of the Local Mobility of RAFT Mediated Poly(acrylic acid) Networks via Low Field
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H‐NMR Techniques for Investigation of the Network Topology. MACROMOL CHEM PHYS 2019. [DOI: 10.1002/macp.201900387] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Federica Cavalli
- Soft Matter Synthesis Laboratories Institute for Biological Interfaces Karlsruhe Institute of Technology Hermann‐von‐Helmholtz Platz 1 76344 Eggenstein‐Leopoldshafen Germany
| | - Christoph Pfeifer
- Institute for Chemical Technology and Polymer Chemistry Karlsruhe Institute of Technology Engesserstrasse 18 76131 Karlsruhe Germany
| | - Lukas Arens
- Institute for Chemical Technology and Polymer Chemistry Karlsruhe Institute of Technology Engesserstrasse 18 76131 Karlsruhe Germany
| | - Leonie Barner
- Soft Matter Synthesis Laboratories Institute for Biological Interfaces Karlsruhe Institute of Technology Hermann‐von‐Helmholtz Platz 1 76344 Eggenstein‐Leopoldshafen Germany
- Institute for Future Environments Queensland University of Technology 2 George St Brisbane Queensland 4000 Australia
| | - Manfred Wilhelm
- Institute for Chemical Technology and Polymer Chemistry Karlsruhe Institute of Technology Engesserstrasse 18 76131 Karlsruhe Germany
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Bohidar P, Sun H, Sarty GE, Sharp JC. TRASE 1D sequence performance in imperfect B 1 fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 305:77-88. [PMID: 31229756 DOI: 10.1016/j.jmr.2019.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 06/08/2019] [Accepted: 06/10/2019] [Indexed: 06/09/2023]
Abstract
Transmit Array Spatial Encoding (TRASE) is an MRI technique that uses radio-frequency (RF) magnetic field (B1) phase gradients for spatial encoding. A TRASE pulse sequence consists of a long echo train in which each echo samples a different k-space point. Due to the need for accurate refocusing, TRASE imaging performance depends on |B1| homogeneity. Although the CPMG echo train is often relied on to provide immunity against B1 flip angle errors, this does not apply to TRASE echo trains. Due to the spatially dependent B1 phases involved in TRASE imaging, the CPMG condition, where all spins flip about the y-axis in the rotating frame, can only be achieved at one single location within the sample. Moreover, CPMG only preserves one component of the transverse magnetization, the y-component, whereas TRASE requires both components to be retained. Here we investigate the performance of a set of variants of a 1-dimensional (1D) TRASE sequence under conditions of |B1| errors. We varied the B1 transmit pulse RF waveform phases in an effort to optimize the TRASE imaging point spread function (PSF). The performance of 256 sequence variants, including those previously reported in the literature was studied. Both Bloch equation simulations and experimental confirmations were completed. Off-resonance (B0 inhomogeneity) effects were not considered so that the effects of B1 inhomogeneity alone could be understood. Results show that, using optimum transmit pulse phases, high quality image encoding is achievable over ∼90% of the Nyquist field-of-view (FOV) for a practically realizable variation in B1 amplitude (Δ|B1|⩽±11%). This improves significantly upon the performance of a previously-reported sequence which generated ∼75% usable FOV within the Nyquist FOV.
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Affiliation(s)
- Pallavi Bohidar
- Space MRI Lab, Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, Canada
| | - Hongwei Sun
- Department of Oncology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Canada
| | - Gordon E Sarty
- Space MRI Lab, Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, Canada
| | - Jonathan C Sharp
- Department of Oncology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Canada.
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O'Brien C, Okell TW, Chiew M, Jezzard P. Volume-localized measurement of oxygen extraction fraction in the brain using MRI. Magn Reson Med 2019; 82:1412-1423. [PMID: 31131930 PMCID: PMC6772021 DOI: 10.1002/mrm.27823] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 04/30/2019] [Accepted: 05/01/2019] [Indexed: 01/12/2023]
Abstract
Purpose T2‐relaxation‐under‐spin‐tagging (TRUST) is an MR technique for the non‐invasive assessment of whole‐brain cerebral oxygen extraction fraction (OEF), through measurement of the venous blood T2 relaxation time in the sagittal sinus. A key limitation of TRUST, however, is the lack of spatial specificity of the measurement. We sought to develop a modified TRUST sequence, selective localized TRUST (SL‐TRUST), having sensitivity to venous blood T2 within a targeted brain region, and therefore achieving spatially localized measurements of cerebral tissue OEF, while still retaining acquisition in the sagittal sinus. Methods A method for selective localization of TRUST sequence was developed, and the reproducibility of the technique was evaluated in healthy participants. Regional measurements were achieved for a single hemisphere and for a 3D‐localized 70 × 70 × 80 mm3 tissue region using SL‐TRUST and compared to a global TRUST measure. An additional measure of venous blood T1 in the sagittal sinus was used to estimate subject‐specific hematocrit. Six subjects were scanned over 4 sessions, including intra‐session repeat measurements. Results The average T2 in the sagittal sinus was found to be 60.8 ± 8.9, 62.7 ± 7.9, 64.6 ± 8.4, and 66.3 ± 10.3 ms (mean ± SD) for conventional TRUST, global SL‐TRUST, hemispheric SL‐TRUST, and 3D‐localized SL‐TRUST, respectively. Intra‐, inter‐session, and inter‐subject coefficients of variation for OEF using SL‐TRUST were found to be comparable and in some cases superior to those obtained using TRUST. Conclusion OEF comparison of 2 contralateral regions was achievable in under 5 min suggesting SL‐TRUST offers potential for quantifying regional OEF differences in both healthy and clinical populations.
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Affiliation(s)
- Caitlin O'Brien
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Thomas W Okell
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Mark Chiew
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Peter Jezzard
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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Holdsworth SJ, O'Halloran R, Setsompop K. The quest for high spatial resolution diffusion-weighted imaging of the human brain in vivo. NMR IN BIOMEDICINE 2019; 32:e4056. [PMID: 30730591 DOI: 10.1002/nbm.4056] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 09/11/2018] [Accepted: 11/08/2018] [Indexed: 06/09/2023]
Abstract
Diffusion-weighted imaging, a contrast unique to MRI, is used for assessment of tissue microstructure in vivo. However, this exquisite sensitivity to finer scales far above imaging resolution comes at the cost of vulnerability to errors caused by sources of motion other than diffusion motion. Addressing the issue of motion has traditionally limited diffusion-weighted imaging to a few acquisition techniques and, as a consequence, to poorer spatial resolution than other MRI applications. Advances in MRI imaging methodology have allowed diffusion-weighted MRI to push to ever higher spatial resolution. In this review we focus on the pulse sequences and associated techniques under development that have pushed the limits of image quality and spatial resolution in diffusion-weighted MRI.
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Affiliation(s)
- Samantha J Holdsworth
- Department of Anatomy Medical Imaging & Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | | | - Kawin Setsompop
- Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA
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7
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Bussandri S, Prina I, Acosta RH, Buljubasich L. Optimized phases for the acquisition of J-spectra in coupled spin systems for thermally and PHIP polarized molecules. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 289:55-62. [PMID: 29471276 DOI: 10.1016/j.jmr.2018.01.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 01/25/2018] [Accepted: 01/28/2018] [Indexed: 06/08/2023]
Abstract
We demonstrate that the relative phases in the refocusing pulses of multipulse sequences can compensate for pulse errors and off-resonant effects, which are commonly encountered in J-spectroscopy when CPMG is used for acquisition. The use of supercycles has been considered many times in the past, but always from the view point of time-domain NMR, that is, in an effort to lengthen the decay of the magnetization. Here we use simple spin-coupled systems, in which the quantum evolution of the system can be simulated and contrasted to experimental results. In order to explore fine details, we resort to partial J-spectroscopy, that is, to the acquisition of J-spectra of a defined multiplet, which is acquired with a suitable digital filter. We unambiguously show that when finite radiofrequency pulses are considered, the off-resonance effects on nearby multiplets affects the dynamics of the spins within the spectral window under acquisition. Moreover, the most robust phase cycling scheme for our setup consists of a 4-pulse cycle, with phases yyyy‾ or xxxx‾ for an excitation pulse with phase x. We show simulated and experimental results in both thermally polarized and PHIP hyperpolarized systems.
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Affiliation(s)
- S Bussandri
- Universidad Nacional de Córdoba - Facultad de Matemática, Atronomía, Física y Computación, Córdoba, Argentina; CONICET - IFEG, Córdoba, Argentina
| | - I Prina
- Universidad Nacional de Córdoba - Facultad de Matemática, Atronomía, Física y Computación, Córdoba, Argentina; CONICET - IFEG, Córdoba, Argentina
| | - R H Acosta
- Universidad Nacional de Córdoba - Facultad de Matemática, Atronomía, Física y Computación, Córdoba, Argentina; CONICET - IFEG, Córdoba, Argentina
| | - L Buljubasich
- Universidad Nacional de Córdoba - Facultad de Matemática, Atronomía, Física y Computación, Córdoba, Argentina; CONICET - IFEG, Córdoba, Argentina.
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8
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Butler MC, Mehta HS, Chen Y, Reardon PN, Renslow RS, Khbeis M, Irish D, Mueller KT. Toward high-resolution NMR spectroscopy of microscopic liquid samples. Phys Chem Chem Phys 2018; 19:14256-14261. [PMID: 28534571 DOI: 10.1039/c7cp01933e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A longstanding limitation of high-resolution NMR spectroscopy is the requirement for samples to have macroscopic dimensions. Commercial probes, for example, are designed for volumes of at least 5 μL, in spite of decades of work directed toward the goal of miniaturization. Progress in miniaturizing inductive detectors has been limited by a perceived need to meet two technical requirements: (1) minimal separation between the sample and the detector, which is essential for sensitivity, and (2) near-perfect magnetic-field homogeneity at the sample, which is typically needed for spectral resolution. The first of these requirements is real, but the second can be relaxed, as we demonstrate here. By using pulse sequences that yield high-resolution spectra in an inhomogeneous field, we eliminate the need for near-perfect field homogeneity and the accompanying requirement for susceptibility matching of microfabricated detector components. With this requirement removed, typical imperfections in microfabricated components can be tolerated, and detector dimensions can be matched to those of the sample, even for samples of volume ≪5 μL. Pulse sequences that are robust to field inhomogeneity thus enable small-volume detection with optimal sensitivity. We illustrate the potential of this approach to miniaturization by presenting spectra acquired with a flat-wire detector that can easily be scaled to subnanoliter volumes. In particular, we report high-resolution NMR spectroscopy of an alanine sample of volume 500 pL.
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Affiliation(s)
- Mark C Butler
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
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9
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Gibbons EK, Le Roux P, Vasanawala SS, Pauly JM, Kerr AB. Robust Self-Calibrating nCPMG Acquisition: Application to Body Diffusion-Weighted Imaging. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:200-209. [PMID: 28829307 PMCID: PMC5784776 DOI: 10.1109/tmi.2017.2741421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
This paper demonstrates a robust diffusion-weighted single-shot fast spin echo (SS-FSE) sequence in the presence of significant off-resonance, which includes a variable-density acquisition and a self-calibrated reconstruction as improvements. A non-Carr-Purcell-Meiboom-Gill (nCPMG) SS-FSE acquisition stabilizes both the main and parasitic echo families for each echo. This preserves both the in-phase and quadrature components of the magnetization throughout the echo train. However, nCPMG SS-FSE also promotes aliasing of the quadrature component, which complicates reconstruction. A new acquisition and reconstruction approach is presented here, where the field-of-view is effectively doubled, but a partial k-space and variable density sampling is used to improve scan efficiency. The technique is presented in phantom scans to validate SNR and robustness against rapidly varying object phase. In vivo healthy volunteer examples and the clinical cases are demonstrated in abdominal imaging. This new approach provides comparable SNR to previous nCPMG acquisition techniques as well as providing more uniform apparent diffusion coefficient maps in phantom scans. In vivo scans suggest that this method is more robust against motion than previous approaches. The proposed reconstruction is an improvement to the nCPMG sequence as it is auto-calibrating and is justified to accurately treat the signal model for the nCPMG SS-FSE sequence.
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10
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Nguyen C, Fan Z, Xie Y, Pang J, Speier P, Bi X, Kobashigawa J, Li D. In vivo diffusion-tensor MRI of the human heart on a 3 tesla clinical scanner: An optimized second order (M2) motion compensated diffusion-preparation approach. Magn Reson Med 2016; 76:1354-1363. [PMID: 27550078 PMCID: PMC5067209 DOI: 10.1002/mrm.26380] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 06/23/2016] [Accepted: 07/22/2016] [Indexed: 12/13/2022]
Abstract
PURPOSE To optimize a diffusion-prepared balanced steady-state free precession cardiac MRI (CMR) technique to perform diffusion-tensor CMR (DT-CMR) in humans on a 3 Tesla clinical scanner METHODS: A previously developed second order motion compensated (M2) diffusion-preparation scheme was significantly shortened (40%) yielding sufficient signal-to-noise ratio for DT-CMR imaging. In 20 healthy volunteers and 3 heart failure (HF) patients, DT-CMR was performed comparing no motion compensation (M0), first order motion compensation (M1), and the optimized M2. Mean diffusivity (MD), fractional anisotropy (FA), helix angle (HA), and HA transmural slope (HATS) were calculated. Reproducibility and success rate (SR) were investigated. RESULTS M2-derived left ventricular (LV) MD, FA, and HATS (1.4 ± 0.2 μm2 /ms, 0.28 ± 0.06, -1.0 ± 0.2 °/%trans) were significantly (P < 0.001) less than M1 (1.8 ± 0.3 μm2 /ms, 0.46 ± 0.14, -0.1 ± 0.3 °/%trans) and M0 (4.8 ± 1.0 μm2 /ms, 0.70 ± 0.14, 0.1 ± 0.3 °/%trans) indicating less motion corruption and yielding values more consistent with previous literature. M2-derived DT-CMR parameters had higher reproducible (ICC > 0.85) and SR (82%) than M1 (ICC = 0.20-0.85; SR = 37%) and M0 (ICC = 0.20-0.30; SR = 11%). M2 DT-CMR was able to yield HA maps with smooth transmural transition from endocardium to epicardium. CONCLUSION The proposed M2 DT-CMR reproducibly yielded bulk motion robust estimations of mean LV MD, FA, HA, and HATS on a 3T clinical scanner. Magn Reson Med 76:1354-1363, 2016. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Christopher Nguyen
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Zhaoyang Fan
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Yibin Xie
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Jianing Pang
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | | | - Xiaoming Bi
- Siemens Healthcare, Los Angeles, California, USA
| | - Jon Kobashigawa
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Debiao Li
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, USA.
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11
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Kim Y, Liu M, Hilty C. Parallelized Ligand Screening Using Dissolution Dynamic Nuclear Polarization. Anal Chem 2016; 88:11178-11183. [PMID: 27723298 DOI: 10.1021/acs.analchem.6b03382] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Protein-ligand interactions are frequently screened using nuclear magnetic resonance (NMR) spectroscopy. The dissociation constant (KD) of a ligand of interest can be determined via a spin-spin relaxation measurement of a reporter ligand in a single scan when using hyperpolarization by means of dissolution dynamic nuclear polarization (D-DNP). Despite nearly instantaneous signal acquisition, a limitation of D-DNP for the screening of protein-ligand interactions is the required polarization time on the order of tens of minutes. Here, we introduce a multiplexed NMR experiment, where a single hyperpolarized ligand sample is rapidly mixed with protein injected into two flow cells. NMR detection is achieved simultaneously on both channels, resulting in a chemical shift resolved spin relaxation measurement. Spectral resolution allows the use of reference compounds for accurate quantification of concentrations. Simultaneous use of two concentration ratios between protein and ligand broadens the range of KD that is accurately measurable in a single experiment to at least an order of magnitude. In a comparison of inhibitors for the protein trypsin, the average KD values of benzamidine and benzylamine were found to be 12.6 ± 1.4 μM and 207 ± 22 μM from three measurements, based on KD = 142 μM assumed known for the reporter ligand 4-(trifluoromethyl)benzene-1-carboximidamide. Typical confidence ranges at 95% evaluated for single experiments were (8.3 μM, 20 μM) and (151 μM, 328 μM). The multiplexed detection of two or more hyperpolarized samples increases throughput of D-DNP by the same factor, improving the applicability to most multipoint measurements that would traditionally be achieved using titrations.
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Affiliation(s)
- Yaewon Kim
- Department of Chemistry, Texas A&M University , College Station, Texas 77843-3255, United States
| | - Mengxiao Liu
- Department of Chemistry, Texas A&M University , College Station, Texas 77843-3255, United States
| | - Christian Hilty
- Department of Chemistry, Texas A&M University , College Station, Texas 77843-3255, United States
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12
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Nezafat R, Stuber M, Ouwerkerk R, Gharib AM, Desai MY, Pettigrew RI. B1-insensitiveT2 preparation for improved coronary magnetic resonance angiography at 3 T. Magn Reson Med 2006; 55:858-64. [PMID: 16538606 DOI: 10.1002/mrm.20835] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T2 preparation (T2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast-passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Numerical simulations predict an excellent suppression of artifacts originating from B1 inhomogeneity while achieving good contrast enhancement between coronary arteries and surrounding tissue. This was confirmed by an in vivo study, in which coronary MR angiograms were obtained without a T2 Prep, with an MLEV weighted T2 Prep and the proposed adiabatic T2 Prep. Improved quantitative and qualitative coronary MRA image measurement was achieved using the adiabatic T2 Prep at 3 T.
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Affiliation(s)
- Reza Nezafat
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
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13
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Nikolova S, Hughes S, Bartha R. T(2) + measurement during acute cerebral ischemia by Carr-Purcell MRI at 4T. Magn Reson Med 2005; 54:1448-54. [PMID: 16265634 DOI: 10.1002/mrm.20716] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Metabolic and structural changes occur in brain tissue within minutes of ischemia. The adiabatic multi-echo (Carr-Purcell) localization pulse sequence LASER has shown promise in detecting tissue contrast changes within the first hour of ischemia. The purpose of this initial study was to combine the LASER localization sequence with fast 3D echo-planar imaging (EPI) to quantify the regional apparent transverse relaxation (T(2) (dagger)) in a rabbit model of acute embolic ischemia at 4 Tesla. Carr-Purcell T(2) (dagger)-weighted images were acquired at 7 different echo-times and used to estimate T(2) (dagger) in both cortex and striatum. In ischemic tissue identified by 2,3,5-triphenyltetrazolium chloride (TTC) staining, the T(2) (dagger) increased by approximately 31% after 1 hour of ischemia and remained elevated until study completion at 4 h of ischemia. Lesion volume, defined as the number of pixels with T(2) (dagger) greater than 90 ms, increased by 40% between 1 and 4 h after induction of ischemia. Carr-Purcell LASER-EPI T(2) (dagger)-weighted images show promise in detecting early tissue changes in focal cerebral ischemia.
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Affiliation(s)
- Simona Nikolova
- Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
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14
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Bastin ME, Le Roux P. On the application of a non-CPMG single-shot fast spin-echo sequence to diffusion tensor MRI of the human brain. Magn Reson Med 2002; 48:6-14. [PMID: 12111926 DOI: 10.1002/mrm.10214] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The strong sensitivity of Carr-Purcell-Meiboom-Gill (CPMG) fast spin-echo (FSE) sequences, such as rapid acquisition with relaxation enhancement (RARE), to the phase of the prepared transverse magnetization means that artifact-free single-shot diffusion-weighted images can currently only be obtained with a 30-50% reduction in the signal-to-noise ratio (SNR). However, this phase sensitivity and signal loss can be addressed in FSE sequences that use quadratic phase modulation of the radiofrequency (RF) refocusing pulses to generate a sustained train of stable echoes. Here the first application of such a non-CPMG single-shot FSE (ssFSE) sequence to diffusion tensor MR imaging (DT-MRI) of the human brain is described. This approach provides high SNR diffusion-weighted images that have little or no susceptibility to poor B(0) magnetic field homogeneity and the strong eddy currents typically present in DT-MRI experiments.
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Affiliation(s)
- Mark E Bastin
- Department of Medical and Radiological Sciences (Medical Physics), University of Edinburgh, Western General Hospital, Edinburgh, UK.
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15
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De Deene Y, De Wagter C, De Neve W, Achten E. Artefacts in multi-echo T2 imaging for high-precision gel dosimetry: I. Analysis and compensation of eddy currents. Phys Med Biol 2000; 45:1807-23. [PMID: 10943920 DOI: 10.1088/0031-9155/45/7/307] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In BANG gel dosimetry, the spin-spin relaxation rate, R2 = I/T2, is related to the radiation dose that has been delivered to the gel phantom. R2 is calculated by fitting the pixel intensities of a set of differently T2-weighted base images. In gel dosimetry for radiotherapy, an accuracy of 5% in dose and 3 mm spatially, whichever is lower, is the objective. Therefore, possible sources of artefacts must be considered and dealt with. To obtain a set of base images a multiple spin-echo sequence is used. However, in a conventional MR scanner eddy currents will be provoked by switching the imaging gradients. As the eddy currents change in the course of the sequence, the net magnetization will be affected accordingly. Hence, eddy currents may have a significant influence on the quantitative R2 images themselves as well as on their slice position. In this study, we report an analysis of the eddy currents as they appear in the multiple spin-echo sequence. Eddy currents are measured using a frequency shift method resulting in eddy current field maps. The related geometrical displacements are obtained by use of a pyramidal phantom. The R2 versus dose relation is determined in the three main directions of the magnet, revealing a dependence of the measured R2 on slice orientation. The time course of eddy currents is then used in a computer simulation to estimate the effects they produce in the recorded R2 images. A compensation method for eddy current effects in multi-echo T2 mapping is described.
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Affiliation(s)
- Y De Deene
- Radiotherapy and Nuclear Medicine, University Hospital of Gent, Belgium.
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16
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De Deenet Y, De Wagter C, De Neve W, Achten E. Artefacts in multi-echo T2 imaging for high-precision gel dosimetry: II. Analysis of B1-field inhomogeneity. Phys Med Biol 2000; 45:1825-39. [PMID: 10943921 DOI: 10.1088/0031-9155/45/7/308] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In BANG gel dosimetry, the spin-spin relaxation rate, R2 = 1/T2, is related to radiation dose that has been delivered to a gel phantom. R2 is calculated by fitting the pixel intensities of a set of differently T2-weighted base images. The accuracy that is aimed for in this quantitative MR application is about 5% relative to the maximum dose. In a conventional imaging MR scanner, however, several imaging artefacts may perturb the final dose map. These deviations manifest themselves as either a deformation of the dose map or an inaccuracy of the dose pixel value. Inaccuracies in the dose maps are caused by both spatial and temporal deviations in signal intensities during scanning. This study deals with B1-field inhomogeneities as a source of dose inaccuracy. First, the influence of B1-field inhomogeneities on slice profiles is investigated using a thin-slice phantom. Secondly, a FLASH sequence is used to map the B1-field by assessing the effective flip angle in each voxel of a homogeneous phantom. In addition, both experiments and computer simulations revealed the effects of B1 field inhomogeneities on the measured R2. This work offers a method to correct R2 maps for B1 -field inhomogeneities.
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Affiliation(s)
- Y De Deenet
- Radiotherapy and Nuclear Medicine, University Hospital of Gent, Belgium.
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17
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Olcott EW, Li KC, Wright GA, Pattarelli PP, Katz DS, Ch'en IY, Daniel BL. Differentiation of hepatic malignancies from hemangiomas and cysts by T2 relaxation times: early experience with multiply refocused four-echo imaging at 1.5 T. J Magn Reson Imaging 1999; 9:81-6. [PMID: 10030654 DOI: 10.1002/(sici)1522-2586(199901)9:1<81::aid-jmri11>3.0.co;2-q] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The purpose of this study was to examine hepatic lesions with a sequence designed to yield improved T2 measurements and evaluate the clinical utility of these measurements in distinguishing malignant from benign disease. Using a modified Carr-Purcell sequence incorporating features designed to compensate for imperfections in the imaging system, including a train of refocusing pulses emitted in an MLEV pattern oriented in composite fashion along all three coordinate axes, and a single spatially selective pulse placed immediately before a spiral readout, 14 benign lesions and 13 malignant lesions were evaluated prospectively with a conventional 1.5 T imager. The maximum, minimum, and mean T2 values of malignant lesions, hemangiomas, and cysts exceeded corresponding published values from spin-echo and echoplanar studies. The mean T2 value of the malignant lesions differed significantly (P < 0.0001) from those of hemangiomas and cysts. All malignant lesions and all benign lesions were distinguishable by their T2 values, which had ranges of no greater than 118.6 msec and no less than 134.3 msec, respectively. This early experience suggests that improved T2 measurements can facilitate the differentiation of hepatic malignancies from hemangiomas and cysts.
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Affiliation(s)
- E W Olcott
- Department of Radiology, Veterans Affairs Palo Alto Health Care System, Stanford University School of Medicine, California 94304, USA
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