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Bjorkqvist O, Pruessmann KP. Stealth RF energy harvesting in MRI using selective shielding. Magn Reson Med 2024; 92:406-415. [PMID: 38411281 DOI: 10.1002/mrm.30048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 12/25/2023] [Accepted: 01/22/2024] [Indexed: 02/28/2024]
Abstract
PURPOSE To utilize the transmit radiofrequency (RF) field in MRI as a power source, near or within the field of view but without affecting image quality or safety. METHODS Power harvesting is performed by RF induction in a resonant coil. Resulting RF field distortion in the subject is canceled by a selective shield that couples to the harvester while being transparent to the RF transmitter. Such shielding is designed with the help of electromagnetic simulation. A shielded harvester of 3 cm diameter is implemented, assessed on the bench, and tested in a 3T MRI system, recording power yield during typical scans. RESULTS The concept of selective shielding is confirmed by simulation. Bench tests show effective power harvesting in the presence of the shield. In the MRI system, it is confirmed that selective shielding virtually eliminates RF perturbation. In scans with the harvester immediately adjacent to a phantom, up to 100 mW of average power are harvested without affecting image quality. CONCLUSION Selective shielding enables stealthy RF harvesting which can be used to supply wireless power to on-body devices during MRI.
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Affiliation(s)
- Oskar Bjorkqvist
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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2
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Ulrich T, Riedel M, Pruessmann KP. Servo navigators: Linear regression and feedback control for rigid-body motion correction. Magn Reson Med 2024; 91:1876-1892. [PMID: 38234052 DOI: 10.1002/mrm.29967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 11/05/2023] [Accepted: 11/24/2023] [Indexed: 01/19/2024]
Abstract
PURPOSE Navigator-based correction of rigid-body motion reconciling high precision with minimal acquisition, minimal calibration and simple, fast processing. METHODS A short orbital navigator (2.3 ms) is inserted in a three-dimensional (3D) gradient echo sequence for human head imaging. Head rotation and translation are determined by linear regression based on a complex-valued model built either from three reference navigators or in a reference-less fashion, from the first actual navigator. Optionally, the model is expanded by global phase and field offset. Run-time scan correction on this basis establishes servo control that maintains validity of the linear picture by keeping its expansion point stable in the head frame of reference. The technique is assessed in a phantom and demonstrated by motion-corrected imaging in vivo. RESULTS The proposed approach is found to establish stable motion control both with and without reference acquisition. In a phantom, it is shown to accurately detect motion mimicked by rotation of scan geometry as well as change in global B0 . It is demonstrated to converge to accurate motion estimates after perturbation well beyond the linear signal range. In vivo, servo navigation achieved motion detection with precision in the single-digit range of micrometers and millidegrees. Involuntary and intentional motion in the range of several millimeters were successfully corrected, achieving excellent image quality. CONCLUSION The combination of linear regression and feedback control enables prospective motion correction for head imaging with high precision and accuracy, short navigator readouts, fast run-time computation, and minimal demand for reference data.
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Affiliation(s)
- Thomas Ulrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Malte Riedel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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3
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Schreiner SJ, Van Bergen JMG, Gietl AF, Buck A, Hock C, Pruessmann KP, Henning A, Unschuld PG. Gray matter gamma-hydroxy-butyric acid and glutamate reflect beta-amyloid burden at old age. Alzheimers Dement (Amst) 2024; 16:e12587. [PMID: 38690510 PMCID: PMC11058481 DOI: 10.1002/dad2.12587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 03/05/2024] [Accepted: 03/10/2024] [Indexed: 05/02/2024]
Abstract
Gamma-hydroxy-butyric acid (GABA) and glutamate are neurotransmitters with essential importance for cognitive processing. Here, we investigate relationships between GABA, glutamate, and brain ß-amyloid (Aß) burden before clinical manifestation of Alzheimer's disease (AD). Thirty cognitively healthy adults (age 69.9 ± 6 years) received high-resolution atlas-based 1H-magnetic resonance spectroscopic imaging (MRSI) at ultra-high magnetic field strength of 7 Tesla for gray matter-specific assessment of GABA and glutamate. We assessed Aß burden with positron emission tomography and risk factors for AD. Higher gray matter GABA and glutamate related to higher Aß-burden (ß = 0.60, p < 0.05; ß = 0.64, p < 0.02), with positive effect modification by apolipoprotein-E-epsilon-4-allele (APOE4) (p = 0.01-0.03). GABA and glutamate negatively related to longitudinal change in verbal episodic memory performance (ß = -0.48; p = 0.02; ß = -0.50; p = 0.01). In vivo measures of GABA and glutamate reflect early AD pathology at old age, in an APOE4-dependent manner. GABA and glutamate may represent promising biomarkers and potential targets for early therapeutic intervention and prevention. Highlights Gray matter-specific metabolic imaging with high-resolution atlas-based MRSI at 7 Tesla.Higher GABA and glutamate relate to ß-amyloid burden, in an APOE4-dependent manner.Gray matter GABA and glutamate identify older adults with high risk of future AD.GABA and glutamate might reflect altered synaptic and neuronal activity at early AD.
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Affiliation(s)
- Simon J. Schreiner
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Psychogeriatric MedicinePsychiatric University Hospital Zurich (PUK)ZurichSwitzerland
- Department of NeurologyUniversity Hospital Zurich and University of ZurichZurichSwitzerland
| | | | - Anton F. Gietl
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- Department of Psychogeriatric MedicinePsychiatric University Hospital Zurich (PUK)ZurichSwitzerland
| | - Alfred Buck
- Department of Nuclear MedicineUniversity Hospital Zurich and University of ZurichZurichSwitzerland
| | - Christoph Hock
- Institute for Regenerative MedicineUniversity of ZurichZurichSwitzerland
- NeurimmuneSchlierenSwitzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical EngineeringUniversity of Zurich and ETH ZurichZurichSwitzerland
| | - Anke Henning
- Institute for Biomedical EngineeringUniversity of Zurich and ETH ZurichZurichSwitzerland
- High‐Field MR CenterMax Planck Institute for Biological CyberneticsTübingenGermany
- Advanced Imaging Research CenterUniversity of Texas Southwestern Medical CenterDallasTexasUSA
| | - Paul G. Unschuld
- Geriatric Psychiatry ServiceUniversity Hospitals of Geneva (HUG)ThônexSwitzerland
- Department of PsychiatryUniversity of Geneva (UniGE)GenevaSwitzerland
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4
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Baadsvik EL, Weiger M, Froidevaux R, Faigle W, Ineichen BV, Pruessmann KP. Quantitative magnetic resonance mapping of the myelin bilayer reflects pathology in multiple sclerosis brain tissue. Sci Adv 2023; 9:eadi0611. [PMID: 37566661 PMCID: PMC10421026 DOI: 10.1126/sciadv.adi0611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/07/2023] [Indexed: 08/13/2023]
Abstract
Multiple sclerosis (MS) is a neuroinflammatory disease characterized by loss of myelin (demyelination) and, to a certain extent, subsequent myelin repair (remyelination). To better understand the pathomechanisms underlying de- and remyelination and to monitor the efficacy of treatments aimed at regenerating myelin, techniques offering noninvasive visualizations of myelin are warranted. Magnetic resonance (MR) imaging has long been at the forefront of efforts to visualize myelin, but it has only recently become feasible to access the rapidly decaying resonance signals stemming from the myelin lipid-protein bilayer itself. Here, we show that direct MR mapping of the bilayer yields highly specific myelin maps in brain tissue from patients with MS. Furthermore, examination of the bilayer signal behavior is found to reveal pathological alterations in normal-appearing white and gray matter. These results indicate promise for in vivo implementations of the myelin bilayer mapping technique, with prospective applications in basic research, diagnostics, disease monitoring, and drug development.
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Affiliation(s)
- Emily Louise Baadsvik
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Romain Froidevaux
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Wolfgang Faigle
- Neuroimmunology and MS Research Section, Neurology Clinic, University of Zurich, University Hospital Zurich, Zurich, Switzerland
- Institut Curie, Immunity and Cancer Unit 932, Paris, France
| | - Benjamin V. Ineichen
- Department of Neuroradiology, Clinical Neuroscience Center, University Hospital Zurich, University of Zurich, Zurich, Switzerland
- Center for Reproducible Science, University of Zurich, Zurich, Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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Hennel F, Dillinger H, Leupold J, Pruessmann KP. Fourier transform temporal diffusion spectroscopy. J Magn Reson 2023; 348:107401. [PMID: 36774713 DOI: 10.1016/j.jmr.2023.107401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 01/04/2023] [Accepted: 02/03/2023] [Indexed: 06/18/2023]
Abstract
Temporal diffusion spectroscopy (TDS) currently uses the oscillating gradient spin echo (OGSE) experiment to measure the spectral density of translational velocity autocorrelation at single frequencies. Due to timing restrictions imposed by the transverse relaxation, the frequency selectivity and the sampling density of OGSE are limited, especially at low frequencies. We propose to overcome this problem by adopting the principles of Fourier transform spectroscopy. The new method of Fourier transform TDS (FTDS) uses two broadband gradient waveforms with different relative delays to make the spin echo attenuation sensitive to a broad range of diffusion frequencies with different harmonic modulations and calculates the spectrum by discrete Fourier transform. The method was validated by a measurement of diffusion spectra in highly restrictive tissues of a celery stalk and provided results consistent with OGSE, however, on a denser frequency grid.
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Affiliation(s)
- Franciszek Hennel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.
| | - Hannes Dillinger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Jochen Leupold
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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Serial MR, Benders S, Rotzetter P, Brummerloh DL, Metzger JP, Gross SP, Nussbaum J, Müller CR, Pruessmann KP, Penn A. Temperature distribution in a gas-solid fixed bed probed by rapid magnetic resonance imaging. Chem Eng Sci 2023. [DOI: 10.1016/j.ces.2023.118457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Kasper L, Engel M, Heinzle J, Mueller-Schrader M, Graedel NN, Reber J, Schmid T, Barmet C, Wilm BJ, Stephan KE, Pruessmann KP. Advances in spiral fMRI: A high-resolution dataset. Data Brief 2022; 42:108050. [PMID: 35372651 PMCID: PMC8968017 DOI: 10.1016/j.dib.2022.108050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 10/25/2022] Open
Abstract
We present data collected for the research article "Advances in Spiral fMRI: A High-resolution Study with Single-shot Acquisition" (Kasper et al. 2022). All data was acquired on a 7T ultra-high field MR system (Philips Achieva), equipped with a concurrent magnetic field monitoring setup based on 16 NMR probes. For task-based fMRI, a visual quarterfield stimulation paradigm was employed, alongside physiological monitoring via peripheral recordings. This data collection contains different datasets pertaining to different purposes: (1) Measured magnetic field dynamics (k0, spiral k-space trajectories, 2nd order spherical harmonics, concomitant fields) during ultra-high field fMRI sessions from six subjects, as well as concurrent temperature curves of the gradient coil, to explore MR system and subject-induced variability of field fluctuations and assess the impact of potential correction methods. (2) MR Raw Data, i.e., coil and concurrent encoding magnetic field (trajectory) data, of a single subject, as well as nominal spiral gradient waveforms, precomputed B0 and coil sensitivity maps, to enable testing of alternative image reconstruction approaches for spiral fMRI data. (3) Reconstructed image time series of the same subject alongside behavioral and physiological logfiles, to reproduce the fMRI preprocessing and analysis, as well as figures presented in the research article related to this article, using the published analysis code repository. All data is provided in standardized formats for the respective research area. In particular, ISMRMRD (HDF5) is used to store raw coil data and spiral trajectories, as well as measured field dynamics. Likewise, the NIfTI format is used for all imaging data (anatomical MRI and spiral fMRI, B0 and coil sensitivity maps).
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Affiliation(s)
- Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
- Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, Zurich 8032 Switzerland
| | - Maria Engel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
| | - Jakob Heinzle
- Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, Zurich 8032 Switzerland
| | - Matthias Mueller-Schrader
- Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, Zurich 8032 Switzerland
| | - Nadine N. Graedel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Jonas Reber
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
| | - Bertram J. Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
| | - Klaas Enno Stephan
- Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, Zurich 8032 Switzerland
- Wellcome Centre for Human Neuroimaging, University College London, London WC1N 3BG, United Kingdom
- Max Planck Institute for Metabolism Research, Cologne 50931, Germany
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
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Kagerer SM, Schroeder C, van Bergen JMG, Schreiner SJ, Meyer R, Steininger SC, Vionnet L, Gietl AF, Treyer V, Buck A, Pruessmann KP, Hock C, Unschuld PG. Low Subicular Volume as an Indicator of Dementia-Risk Susceptibility in Old Age. Front Aging Neurosci 2022; 14:811146. [PMID: 35309894 PMCID: PMC8926841 DOI: 10.3389/fnagi.2022.811146] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 01/31/2022] [Indexed: 11/13/2022] Open
Abstract
Introduction Hippocampal atrophy is an established Alzheimer’s Disease (AD) biomarker. Volume loss in specific subregions as measurable with ultra-high field magnetic resonance imaging (MRI) may reflect earliest pathological alterations. Methods Data from positron emission tomography (PET) for estimation of cortical amyloid β (Aβ) and high-resolution 7 Tesla T1 MRI for assessment of hippocampal subfield volumes were analyzed in 61 non-demented elderly individuals who were divided into risk-categories as defined by high levels of cortical Aβ and low performance in standardized episodic memory tasks. Results High cortical Aβ and low episodic memory interactively predicted subicular volume [F(3,57) = 5.90, p = 0.018]. The combination of high cortical Aβ and low episodic memory was associated with significantly lower subicular volumes, when compared to participants with high episodic memory (p = 0.004). Discussion Our results suggest that low subicular volume is linked to established indicators of AD risk, such as increased cortical Aβ and low episodic memory. Our data support subicular volume as a marker of dementia-risk susceptibility in old-aged non-demented persons.
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Affiliation(s)
- Sonja M. Kagerer
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Psychogeriatric Medicine, Psychiatric University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Clemens Schroeder
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
| | | | - Simon J. Schreiner
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
| | - Rafael Meyer
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
| | - Stefanie C. Steininger
- Psychogeriatric Medicine, Psychiatric University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Laetitia Vionnet
- Institute for Biomedical Engineering, University of Zurich and ETH Zürich, Zurich, Switzerland
| | - Anton F. Gietl
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Psychogeriatric Medicine, Psychiatric University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Valerie Treyer
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Department of Nuclear Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Alfred Buck
- Department of Nuclear Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zürich, Zurich, Switzerland
| | - Christoph Hock
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Neurimmune, Schlieren, Switzerland
| | - Paul G. Unschuld
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Psychogeriatric Medicine, Psychiatric University Hospital Zurich, University of Zurich, Zurich, Switzerland
- Institute for Biomedical Engineering, University of Zurich and ETH Zürich, Zurich, Switzerland
- Geriatric Psychiatry, Department of Psychiatry, University Hospitals of Geneva, University of Geneva, Geneva, Switzerland
- *Correspondence: Paul G. Unschuld,
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9
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Nussbaum J, Dietrich BE, Wilm BJ, Pruessmann KP. Thermal variation in gradient response: measurement and modeling. Magn Reson Med 2021; 87:2224-2238. [PMID: 34932233 PMCID: PMC9303907 DOI: 10.1002/mrm.29123] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 11/02/2021] [Accepted: 11/29/2021] [Indexed: 12/14/2022]
Abstract
PURPOSE Many aspects and imperfections of gradient dynamics in MRI have been successfully captured by linear time-invariant (LTI) models. Changes in gradient behavior due to heating, however, violate time invariance. The goal of this work is to study such changes at the level of transfer functions and model them by thermal extension of the LTI framework. METHODS To study the impact of gradient heating on transfer functions, a clinical MR system was heated using a range of high-amplitude DC and AC waveforms, each followed by measuring transfer functions in rapid succession while the system cooled down. Simultaneously, gradient temperature was monitored with an array of temperature sensors positioned according to initial infrared recordings of the gradient tube. The relation between temperatures and transfer functions is cast into local and global linear models. The models are analysed in terms of self-consistency, conditioning, and prediction performance. RESULTS Pronounced thermal effects are observed in the time resolved transfer functions, largely attributable to in-coil eddy currents and mechanical resonances. Thermal modeling is found to capture these effects well. The keys to good model performance are well-placed temperature sensors and suitable training data. CONCLUSION Heating changes gradient response, violating time invariance. The utility of LTI modeling can nevertheless be recovered by a linear thermal extension, relying on temperature sensing and adequate one-time training.
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Affiliation(s)
- Jennifer Nussbaum
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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10
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Froidevaux R, Weiger M, Pruessmann KP. Pulse encoding for ZTE imaging: RF excitation without dead-time penalty. Magn Reson Med 2021; 87:1360-1374. [PMID: 34775617 PMCID: PMC9299067 DOI: 10.1002/mrm.29056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 09/09/2021] [Accepted: 10/04/2021] [Indexed: 11/23/2022]
Abstract
Purpose To overcome limitations in the duration of RF excitation in zero‐TE (ZTE) MRI by exploiting intrinsic encoding properties of RF pulses to retrieve data missed during the dead time caused by the pulse. Methods An enhanced ZTE signal model was developed using multiple RF pulses, which enables accessing information hidden in the pulse‐induced dead time via encoding intrinsically applied by the RF pulses. Such ZTE with pulse encoding was implemented by acquisition of two ZTE data sets using excitation with similar frequency‐swept pulses differing only by a small off‐resonance in their center frequency. In this way, the minimum scan time is doubled but each acquisition contributes equally to the SNR, as with ordinary averaging. The method was demonstrated on long‐T2 and short‐T2 phantoms as well as in in vivo experiments. Results ZTE with pulse encoding provided good image quality at unprecedented dead‐time gaps, demonstrated here up to 6 Nyquist dwells. In head imaging, the ability to use longer excitation pulses led to approximately 2‐fold improvements in SNR efficiency as compared with conventional ZTE and allowed the creation of T1 contrast. Conclusion Exploiting intrinsic encoding properties of RF pulses in a new signal model enables algebraic reconstruction of ZTE data sets with large dead‐time gaps. This permits larger flip angles, which can be used to achieve enhanced T1 contrast and significant improvements in SNR efficiency in case the Ernst angle can be better approached, thus broadening the range of application of ZTE MRI.
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Affiliation(s)
- Romain Froidevaux
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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11
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Graedel NN, Kasper L, Engel M, Nussbaum J, Wilm BJ, Pruessmann KP, Vannesjo SJ. Feasibility of spiral fMRI based on an LTI gradient model. Neuroimage 2021; 245:118674. [PMID: 34718138 DOI: 10.1016/j.neuroimage.2021.118674] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 10/15/2021] [Accepted: 10/20/2021] [Indexed: 11/25/2022] Open
Abstract
Spiral imaging is very well suited for functional MRI, however its use has been limited by the fact that artifacts caused by gradient imperfections and B0 inhomogeneity are more difficult to correct compared to EPI. Effective correction requires accurate knowledge of the traversed k-space trajectory. With the goal of making spiral fMRI more accessible, we have evaluated image reconstruction using trajectories predicted by the gradient impulse response function (GIRF), which can be determined in a one-time calibration step. GIRF-predicted reconstruction was tested for high-resolution (0.8 mm) fMRI at 7T. Image quality and functional results of the reconstructions using GIRF-prediction were compared to reconstructions using the nominal trajectory and concurrent field monitoring. The reconstructions using nominal spiral trajectories contain substantial artifacts and the activation maps contain misplaced activation. Image artifacts are substantially reduced when using the GIRF-predicted reconstruction, and the activation maps for the GIRF-predicted and monitored reconstructions largely overlap. The GIRF reconstruction provides a large increase in the spatial specificity of the activation compared to the nominal reconstruction. The GIRF-reconstruction generates image quality and fMRI results similar to using a concurrently monitored trajectory. The presented approach does not prolong or complicate the fMRI acquisition. Using GIRF-predicted trajectories has the potential to enable high-quality spiral fMRI in situations where concurrent trajectory monitoring is not available.
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Affiliation(s)
- Nadine N Graedel
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland; Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Maria Engel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Jennifer Nussbaum
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - S Johanna Vannesjo
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
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Engel M, Kasper L, Wilm B, Dietrich B, Patzig F, Vionnet L, Pruessmann KP. Mono-planar T-Hex: Speed and flexibility for high-resolution 3D imaging. Magn Reson Med 2021; 87:272-280. [PMID: 34398985 PMCID: PMC9292510 DOI: 10.1002/mrm.28979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 07/06/2021] [Accepted: 07/31/2021] [Indexed: 11/23/2022]
Abstract
Purpose The aim of this work is the reconciliation of high spatial and temporal resolution for MRI. For this purpose, a novel sampling strategy for 3D encoding is proposed, which provides flexible k‐space segmentation along with uniform sampling density and benign filtering effects related to signal decay. Methods For time‐critical MRI applications such as functional MRI (fMRI), 3D k‐space is usually sampled by stacking together 2D trajectories such as echo planar imaging (EPI) or spiral readouts, where each shot covers one k‐space plane. For very high temporal and medium to low spatial resolution, tilted hexagonal sampling (T‐Hex) was recently proposed, which allows the acquisition of a larger k‐space volume per excitation than can be covered with a planar readout. Here, T‐Hex is described in a modified version where it instead acquires a smaller k‐space volume per shot for use with medium temporal and high spatial resolution. Results Mono‐planar T‐Hex sampling provides flexibility in the choice of speed, signal‐to‐noise ratio (SNR), and contrast for rapid MRI acquisitions. For use with a conventional gradient system, it offers the greatest benefit in a regime of high in‐plane resolution <1 mm. The sampling scheme is combined with spirals for high sampling speed as well as with more conventional EPI trajectories. Conclusion Mono‐planar T‐Hex sampling combines fast 3D encoding with SNR efficiency and favorable depiction characteristics regarding noise amplification and filtering effects from T2∗ decay, thereby providing flexibility in the choice of imaging parameters. It is attractive both for high‐resolution time series such as fMRI and for applications that require rapid anatomical imaging.
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Affiliation(s)
- Maria Engel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.,Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Bertram Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Franz Patzig
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Laetitia Vionnet
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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13
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Froidevaux R, Weiger M, Rösler MB, Brunner DO, Pruessmann KP. HYFI: Hybrid filling of the dead-time gap for faster zero echo time imaging. NMR Biomed 2021; 34:e4493. [PMID: 33624305 PMCID: PMC8244056 DOI: 10.1002/nbm.4493] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 01/25/2021] [Accepted: 01/29/2021] [Indexed: 05/31/2023]
Abstract
The aim of this work was to improve the SNR efficiency of zero echo time (ZTE) MRI pulse sequences for faster imaging of short-T2 components at large dead-time gaps. ZTE MRI with hybrid filling (HYFI) is a strategy for retrieving inner k-space data missed during the dead-time gaps arising from radio-frequency excitation and switching in ZTE imaging. It performs hybrid filling of the inner k-space with a small single-point-imaging core surrounded by a stack of shells acquired on radial readouts in an onion-like fashion. The exposition of this concept is followed by translation into guidelines for parameter choice and implementation details. The imaging properties and performance of HYFI are studied in simulations as well as phantom, in vitro and in vivo imaging, with an emphasis on comparison with the pointwise encoding time reduction with radial acquisition (PETRA) technique. Simulations predict higher SNR efficiency for HYFI compared with PETRA at preserved image quality, with the advantage increasing with the size of the k-space gap. These results are confirmed by imaging experiments with gap sizes of 25 to 50 Nyquist dwells, in which scan times for similar image quality could be reduced by 25% to 60%. The HYFI technique provides both high SNR efficiency and image quality, thus outperforming previously known ZTE-based pulse sequences, in particular for large k-space gaps. Promising applications include direct imaging of ultrashort-T2 components, such as the myelin bilayer or collagen, T2 mapping of ultrafast relaxing signals, and ZTE imaging with reduced chemical shift artifacts.
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Affiliation(s)
- Romain Froidevaux
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Manuela B Rösler
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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14
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Hennel F, Michael ES, Pruessmann KP. Improved gradient waveforms for oscillating gradient spin-echo (OGSE) diffusion tensor imaging. NMR Biomed 2021; 34:e4434. [PMID: 33124071 DOI: 10.1002/nbm.4434] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 09/11/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
The dependence of the diffusion tensor on frequency is of great interest in studies of tissue microstructure because it reveals restrictions to the Brownian motion of water molecules caused by cell membranes. Oscillating gradient spin-echo (OGSE) sequences can sample this dependence with gradient shapes for which the power spectrum of the zeroth moment is focused at a target frequency. In order to maintain the total spectral power (ie the b-value), oscillating gradient amplitudes must grow with the frequency squared. For this reason, OGSE applications on clinical MRI scanners are limited to low frequencies, for which it is difficult to obtain a narrow frequency bandwidth of the gradient moment in a useful echo time. In particular, the commonly used pair of single-period trapezoidal-cosine pulses separated by a half-period produces significant side lobes away from the target frequency. To mitigate this effect, improved OGSE waveforms are proposed, which reduce the gap between the two gradient pulses to the minimum duration required for the refocusing RF pulse. Additionally, a slight deviation from the periodicity of the waveforms is proposed in order to permit using the maximum slew rate of the gradient system for all lobes of trapezoidal waveforms while maintaining advantageous spectral properties, which is not the case for the currently used OGSE sequences. Numerical calculations validate these changes, showing that both modifications significantly narrow the gradient moment power spectrum and increase the contribution of its main lobe to the b-value, thus improving the specificity of the measurement. The utility of the new shapes is demonstrated by diffusion tensor measurements of human white matter in vivo over the range of 30-75 Hz with a b-value of nearly 1000 s/mm2 , using a high-performance gradient insert. However, the improvement should increase the sampling precision of OGSE experiments for all gradient systems.
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Affiliation(s)
- Franciszek Hennel
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Eric Seth Michael
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
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15
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Port A, Luechinger R, Brunner DO, Pruessmann KP. Elastomer coils for wearable MR detection. Magn Reson Med 2021; 85:2882-2891. [PMID: 33433044 DOI: 10.1002/mrm.28662] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/20/2020] [Accepted: 12/07/2020] [Indexed: 01/06/2023]
Abstract
PURPOSE To explore the use of conductive elastomer for MR signal detection and the utility of this approach for wearable detector arrays. METHODS An elastomer filled with silver microparticles was used to form stretchable radiofrequency coils for MR detection. Their electrical performance in terms of the Qunloaded and Q ratio was assessed in the relaxed state and under repeated strain up to 40%. In a phantom imaging study, the signal-to-noise ratio yield of conductive elastomer coils was compared with that of a reference copper coil. Four elastomer coils were integrated with a stretchable textile substrate to form a wearable array for knee imaging. The array was employed for multiple-angle and kinematic knee imaging in vivo. RESULTS The elastomer coils proved highly stretchable and mechanically robust. Upon repeated stretching by 20%, a medium-sized coil element settled at Qunloaded of 42 in the relaxed state and 32 at full strain, reflecting sample-noise dominance. The signal-to-noise ratio of elastomer coils was found to be 8% to 16% lower than that achieved with a conventional copper coil. Multiple-angle and kinematic knee imaging with the wearable array yielded high-quality results indicating robustness of detection performance against stretching and warping of the array. CONCLUSION Conductive elastomer is a viable material for MR detection. Coils made from this material reconcile high stretchability and adequate electrical performance with ease of manufacturing. Conductive elastomer also offers inherent restoring forces and is readily washable and sanitizable, making it an excellent basis of wearable detector front ends.
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Affiliation(s)
- Andreas Port
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Roger Luechinger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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16
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Lee Y, Wilm BJ, Brunner DO, Gross S, Schmid T, Nagy Z, Pruessmann KP. On the signal-to-noise ratio benefit of spiral acquisition in diffusion MRI. Magn Reson Med 2020; 85:1924-1937. [PMID: 33280160 DOI: 10.1002/mrm.28554] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/15/2020] [Accepted: 09/22/2020] [Indexed: 12/20/2022]
Abstract
PURPOSE Spiral readouts combine several favorable properties that promise superior net sensitivity for diffusion imaging. The purpose of this study is to verify the signal-to-noise ratio (SNR) benefit of spiral acquisition in comparison with current echo-planar imaging (EPI) schemes. METHODS Diffusion-weighted in vivo brain data from three subjects were acquired with a single-shot spiral sequence and several variants of single-shot EPI, including full-Fourier and partial-Fourier readouts as well as different diffusion-encoding schemes. Image reconstruction was based on an expanded signal model including field dynamics obtained by concurrent field monitoring. The effective resolution of each sequence was matched to that of full-Fourier EPI with 1 mm nominal resolution. SNR maps were generated by determining the noise statistics of the raw data and analyzing the propagation of equivalent synthetic noise through image reconstruction. Using the same approach, maps of noise amplification due to parallel imaging (g-factor) were calculated for different acceleration factors. RESULTS Relative to full-Fourier EPI at b = 0 s/mm2 , spiral acquisition yielded SNR gains of 42-88% and 40-89% in white and gray matter, respectively, depending on the diffusion-encoding scheme. Relative to partial-Fourier EPI, the gains were 36-44% and 34-42%. Spiral g-factor maps exhibited less spatial variation and lower maxima than their EPI counterparts. CONCLUSION Spiral readouts achieve significant SNR gains in the order of 40-80% over EPI in diffusion imaging at 3T. Combining systematic effects of shorter echo time, readout efficiency, and favorable g-factor behavior, similar benefits are expected across clinical and neurosciences uses of diffusion imaging.
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Affiliation(s)
- Yoojin Lee
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.,Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Zoltan Nagy
- Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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17
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Engel M, Kasper L, Wilm B, Dietrich B, Vionnet L, Hennel F, Reber J, Pruessmann KP. T-Hex: Tilted hexagonal grids for rapid 3D imaging. Magn Reson Med 2020; 85:2507-2523. [PMID: 33270941 DOI: 10.1002/mrm.28600] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 01/09/2023]
Abstract
PURPOSE The purpose of this work is to devise and demonstrate an encoding strategy for 3D MRI that reconciles high speed with flexible segmentation, uniform k-space density, and benign T 2 ∗ effects. METHODS Fast sampling of a 3D k-space is typically accomplished by 2D readouts per shot using EPI trains or spiral readouts. Tilted hexagonal (T-Hex) sampling is a way of acquiring more k-space volume per excitation while maintaining uniform sampling density and a smooth T 2 ∗ filter. The k-space volume covered per shot is controlled by the tilting angle. Image reconstruction is performed with a 3D extension of the iterative SENSE approach, incorporating actual field dynamics and static off-resonance. T-Hex imaging is compared with established 3D schemes in terms of speed and noise performance. RESULTS Tilted hexagonal acquisition is found to achieve greater imaging speed than known alternatives, particularly in combination with spiral trajectories. The interplay of the proposed 3D trajectories, array detection, and off-resonance is successfully addressed by iterative inversion of the full signal model. Enhanced coverage per shot is of greatest utility for high speed in an intermediate resolution regime of 1 to 4 mm. T-Hex EPI combines the benefits of extended coverage per shot with increased robustness against off-resonance effects. CONCLUSION Sampling of tilted hexagonal grids is a feasible means of gaining 3D imaging speed with near-optimal SNR efficiency and benign depiction properties. It is a particularly promising technique for time-resolved applications such as fMRI.
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Affiliation(s)
- Maria Engel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.,Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Bertram Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Laetitia Vionnet
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Franciszek Hennel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Jonas Reber
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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18
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Kagerer SM, Schroeder C, Van Bergen JMG, Schreiner SJ, Meyer R, Steininger SC, Laetitia V, Gietl AF, Treyer V, Buck A, Pruessmann KP, Hock C, Unschuld PG. Beta‐amyloid‐associated episodic memory variation correlates with subicular volume in non‐demented old aged individuals. Alzheimers Dement 2020. [DOI: 10.1002/alz.043904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Sonja M Kagerer
- Hospital for Psychogeriatric Medicine University of Zurich Zurich Switzerland
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
| | - Clemens Schroeder
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
| | | | - Simon J. Schreiner
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
| | - Rafael Meyer
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
| | | | - Vionnet Laetitia
- Institute for Biomedical Engineering University of Zürich and ETH Zürich Zürich Switzerland
| | - Anton F. Gietl
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
| | - Valerie Treyer
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
- Department of Nuclear Medicine University Hospital Zürich and University of Zürich Zurich Switzerland
| | - Alfred Buck
- Department of Nuclear Medicine University Hospital Zürich and University of Zürich Zurich Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering University of Zurich and ETH Zurich Zürich Switzerland
| | - Christoph Hock
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
- University of Zurich Institute for Regenerative Medicine ‐ IREM Schlieren Switzerland
| | - Paul G. Unschuld
- Hospital for Psychogeriatric Medicine University of Zurich Zurich Switzerland
- Institute for Regenerative Medicine University of Zurich Schlieren Switzerland
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19
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Do CT, Manjaly ZM, Heinzle J, Schöbi D, Kasper L, Pruessmann KP, Stephan KE, Frässle S. Hemodynamic modeling of long-term aspirin effects on blood oxygenated level dependent responses at 7 Tesla in patients at cardiovascular risk. Eur J Neurosci 2020; 53:1262-1278. [PMID: 32936980 DOI: 10.1111/ejn.14970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 08/06/2020] [Accepted: 09/02/2020] [Indexed: 11/29/2022]
Abstract
Aspirin is considered a potential confound for functional magnetic resonance imaging (fMRI) studies. This is because aspirin affects the synthesis of prostaglandin, a vasoactive mediator centrally involved in neurovascular coupling, a process underlying blood oxygenated level dependent (BOLD) responses. Aspirin-induced changes in BOLD signal are a potential confound for fMRI studies of at-risk individuals or patients (e.g. with cardiovascular conditions or stroke) who receive low-dose aspirin prophylactically and are compared to healthy controls without aspirin. To examine the severity of this potential confound, we combined high field (7 Tesla) MRI during a simple hand movement task with a biophysically informed hemodynamic model. We compared elderly individuals receiving aspirin for primary or secondary prophylactic purposes versus age-matched volunteers without aspirin medication, testing for putative differences in BOLD responses. Specifically, we fitted hemodynamic models to BOLD responses from 14 regions activated by the task and examined whether model parameter estimates were significantly altered by aspirin. While our analyses indicate that hemodynamics differed across regions, consistent with the known regional variability of BOLD responses, we neither found a significant main effect of aspirin (i.e., an average effect across brain regions) nor an expected drug × region interaction. While our sample size is not sufficiently large to rule out small-to-medium global effects of aspirin, we had adequate statistical power for detecting the expected interaction. Altogether, our analysis suggests that patients with cardiovascular risk receiving low-dose aspirin for primary or secondary prophylactic purposes do not show strongly altered BOLD signals when compared to healthy controls without aspirin.
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Affiliation(s)
- Cao-Tri Do
- Translational Neuromodeling Unit, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland
| | - Zina-Mary Manjaly
- Department of Neurology, Schulthess Clinic, Zurich, Switzerland.,Department of Health Science and Technology (D-HEST), ETH Zurich, Zurich, Switzerland
| | - Jakob Heinzle
- Translational Neuromodeling Unit, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland
| | - Dario Schöbi
- Translational Neuromodeling Unit, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland
| | - Lars Kasper
- Translational Neuromodeling Unit, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland.,MR Technology Group, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- MR Technology Group, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland
| | - Klaas Enno Stephan
- Translational Neuromodeling Unit, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland.,Wellcome Centre for Human Neuroimaging, University College London, London, UK.,Max Planck Institute for Metabolism Research, Cologne, Germany
| | - Stefan Frässle
- Translational Neuromodeling Unit, Institute of Biomedical Engineering, University of Zurich & ETH Zurich, Zurich, Switzerland
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20
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Rösler MB, Leussler C, Brunner DO, Schmid T, Hennel F, Luechinger R, Weiger M, Pruessmann KP. A transmit–receive array for brain imaging with a high‐performance gradient insert. Magn Reson Med 2020; 84:2278-2289. [DOI: 10.1002/mrm.28261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 02/24/2020] [Accepted: 02/27/2020] [Indexed: 12/26/2022]
Affiliation(s)
- Manuela B. Rösler
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
| | | | - David O. Brunner
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
| | - Thomas Schmid
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
| | - Franciszek Hennel
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
| | - Roger Luechinger
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
| | - Markus Weiger
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
| | - Klaas P. Pruessmann
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering Zurich CH Switzerland
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21
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Marjanovic J, Reber J, Brunner DO, Engel M, Kasper L, Dietrich BE, Vionnet L, Pruessmann KP. A Reconfigurable Platform for Magnetic Resonance Data Acquisition and Processing. IEEE Trans Med Imaging 2020; 39:1138-1148. [PMID: 31567076 DOI: 10.1109/tmi.2019.2944696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Developments in magnetic resonance imaging (MRI) in the last decades show a trend towards a growing number of array coils and an increasing use of a wide variety of sensors. Associated cabling and safety issues have been addressed by moving data acquisition closer to the coil. However, with the increasing number of radio-frequency (RF) channels and trend towards higher acquisition duty-cycles, the data amount is growing, which poses challenges for throughput and data handling. As it is becoming a limitation, early compression and preprocessing is becoming ever more important. Additionally, sensors deliver diverse data, which require distinct and often low-latency processing for run-time updates of scanner operation. To address these challenges, we propose the transition to reconfigurable hardware with an application tailored assembly of interfaces and real-time processing resources. We present an integrated solution based on a system-on-chip (SoC), which offers sufficient throughput and hardware-based parallel processing power for very challenging applications. It is equipped with fiber-optical modules serving as versatile interfaces for modular systems with in-field operation. We demonstrate the utility of the platform on the example of concurrent imaging and field sensing with hardware-based coil compression and trajectory extraction. The preprocessed data are then used in expanded encoding model based image reconstruction of single-shot and segmented spirals as used in time-series and anatomical imaging respectively.
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22
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Reber J, Marjanovic J, Brunner DO, Port A, Schmid T, Dietrich BE, Moser U, Barmet C, Pruessmann KP. An In-Bore Receiver for Magnetic Resonance Imaging. IEEE Trans Med Imaging 2020; 39:997-1007. [PMID: 31484112 DOI: 10.1109/tmi.2019.2939090] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In magnetic resonance imaging, the use of array detection and the number of detector elements have seen a steady increase over the past two decades. As a result, per-channel analog connection via long coaxial cable, as commonly used, poses an increasing challenge in terms of handling, safety, and coupling among cables. This situation is exacerbated when complementary recording of radiofrequency transmission or NMR-based magnetic field sensing further add to channel counts. A generic way of addressing this trend is the transition to digital signal transmission, enabled by digitization and first-level digital processing close to detector coils and sensors in the magnet bore. The foremost challenge that comes with this approach is to achieve high dynamic range, linearity, and phase stability despite interference by strong static, audiofrequency, and radiofrequency fields. The present work reports implementation of a 16-channel in-bore receiver, performing signal digitization and processing with subsequent optical transmission over fiber. Along with descriptions of the system design and construction, performance evaluation is reported. The resulting device is fully MRI compatible providing practically equal performance and signal quality compared to state-of-the-art RF digitizers operating outside the magnet. Its use is demonstrated by examples of head imaging and magnetic field recording.
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23
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Froidevaux R, Weiger M, Rösler MB, Brunner DO, Dietrich BE, Reber J, Pruessmann KP. High-resolution short-T 2 MRI using a high-performance gradient. Magn Reson Med 2020; 84:1933-1946. [PMID: 32176828 DOI: 10.1002/mrm.28254] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 02/20/2020] [Accepted: 02/20/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE To achieve high resolution in imaging of short-T2 materials and tissues by using a high-performance human-sized gradient insert with strength up to 200 mT/m and 100% duty cycle. METHODS Dedicated short-T2 methodology and hardware are used, such as the pointwise encoding time reduction with radial acquisition (PETRA) technique with modulated excitation pulses, optimized radio-frequency hardware, and a high-performance gradient insert. A theoretical analysis of actual spatial resolution and SNR is provided to support the choice of scan parameters and interpretation of the results. Imaging is performed in resolution phantoms, animal specimen, and human volunteers at both conventional and maximum available gradient strengths and compared using image subtraction. RESULTS Calculations suggest that increasing gradient strength beyond conventional values considerably improves both actual resolution and SNR efficiency in short-T2 imaging. Resolution improvements are confirmed in all investigated samples, in particular 2 mm slots were resolved in a hard-plastic plate with T2 ≈ 10 μs and in vivo musculoskeletal images were acquired at isotropic 200 μm resolution. Expected improvements in signal yield are realized in fine structures benefitting from high resolution but to less extent in regions of low contrast where decay-related blurring leads to signal overlap between neighboring locations. CONCLUSION Strong gradients with high duty cycle enable short-T2 imaging at unprecedentedly high resolution, holding the potential for improving MRI of, eg, bone, tendon, lung, or teeth. Moreover, it allows direct access of tissues with T2 of tens of microseconds such as myelin or collagen.
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Affiliation(s)
- Romain Froidevaux
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Manuela B Rösler
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Jonas Reber
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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Wilm BJ, Dietrich BE, Reber J, Vannesjo SJ, Pruessmann KP. Gradient Response Harvesting for Continuous System Characterization During MR Sequences. IEEE Trans Med Imaging 2020; 39:806-815. [PMID: 31425067 DOI: 10.1109/tmi.2019.2936107] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
MRI gradient systems are required to generate magnetic field gradient waveforms with very high fidelity. This is commonly implemented by gradient system calibration and pre-emphasis. However, a number of mechanisms, particularly thermal changes, cause variation in the gradient response over time, which cannot be addressed by calibration approaches. To overcome this limitation, we present a novel method termed gradient response harvesting, where the gradient response is continuously characterized during the course of a normal MR sequence. Snippets of field measurements are repeatedly acquired during an MR sequence, and from these multiple field measurements and the known nominal MR sequence gradients, the gradient response and gradient/field offsets are calculated. The calculation is implemented in a model-based and a model-free variant. The method is demonstrated for EPI with high gradient duty-cycle, where the continuous gradient characterization is used to obtain k-space trajectory estimates that are employed in the subsequent image reconstruction. During the course of the MR sequence, changes in both the envelope and the phase of the gradient response functions were observed, including shifts of mechanical resonances. The gradient response changes were also reflected in the calculated uninterrupted gradient waveforms and thus in the k-space trajectories. Using the updated encoding information in the image reconstruction removed ghosting artifacts, that otherwise impaired the image quality. We introduced the concept of gradient response harvesting and demonstrated its feasibility. The obtained gradient response functions may be used for quality assurance/preventive maintenance, real-time adaptation of gradient pre-emphasis or to calculate uninterrupted gradient field evolutions.
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Hennel F, Wilm B, Roesler MB, Weiger M, Dietrich B, Pruessmann KP. Echo-planar imaging of the human head with 100 mT/m gradients and high-order modeling of eddy current fields. Magn Reson Med 2020; 84:751-761. [PMID: 31961966 DOI: 10.1002/mrm.28168] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/25/2019] [Accepted: 12/19/2019] [Indexed: 11/08/2022]
Abstract
PURPOSE To demonstrate the utility of a high-performance gradient insert for ultrafast MRI of the human head. METHODS EPI was used for the first time with a readout gradient amplitude of 100 mT/m, 1200 T/m/s slew rate, and nearly 1 MHz signal bandwidth for human head scanning. To avoid artefacts due to eddy currents, the magnetic field was dynamically monitored with NMR probes at multiple points, modeled by solid harmonics up to fifth order, and included in the image reconstruction. An approximation of a negligible intra-echo effect of the eddy currents was made to accelerate the high-order reconstruction. The field monitoring-based approach was compared with a recently proposed phase error estimation from separate reconstructions of even and odd echoes. RESULTS Images obtained with the gradient insert have significantly lower distortions than it is the case with the whole body 30 mT/m, 200 T/m/s gradients of the same system. However, eddy currents of high spatial order must be properly characterized and corrected for in order to avoid a persistent 2D Nyquist ghost. Multi-position monitoring proves to be a robust method to measure the eddy currents and allows higher undersampling rates than the image-based approach. The proposed approximation of the eddy currents effect allows a significant acceleration of the high-order reconstruction by a separate processing of each spatial dimension. CONCLUSION Strong gradients with adequate switching rates are highly beneficial for the quality of EPI provided that robust measures are taken to include the contribution of eddy currents to the image encoding.
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Affiliation(s)
- Franciszek Hennel
- Institute for Biomedical Engineering, ETH Zurich, and University of Zurich, Zurich, Switzerland
| | - Bertram Wilm
- Institute for Biomedical Engineering, ETH Zurich, and University of Zurich, Zurich, Switzerland
| | - Manuela B Roesler
- Institute for Biomedical Engineering, ETH Zurich, and University of Zurich, Zurich, Switzerland
| | - Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich, and University of Zurich, Zurich, Switzerland
| | | | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich, and University of Zurich, Zurich, Switzerland
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Aranovitch A, Haeberlin M, Gross S, Dietrich BE, Reber J, Schmid T, Pruessmann KP. Motion detection with NMR markers using real‐time field tracking in the laboratory frame. Magn Reson Med 2019; 84:89-102. [DOI: 10.1002/mrm.28094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 11/01/2019] [Accepted: 11/01/2019] [Indexed: 01/13/2023]
Affiliation(s)
- Alexander Aranovitch
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
| | - Maximilian Haeberlin
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
| | - Benjamin E. Dietrich
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
| | - Jonas Reber
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering ETH Zurich and University of Zurich Zurich Switzerland
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Tian R, Hennel F, Pruessmann KP. Low-distortion diffusion tensor MRI with improved phaseless encoding. J Magn Reson 2019; 309:106602. [PMID: 31614304 DOI: 10.1016/j.jmr.2019.106602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 09/13/2019] [Accepted: 09/16/2019] [Indexed: 06/10/2023]
Abstract
Due to the motion-related instability of the signal phase, diffusion MRI is usually performed with single-shot techniques such as the echo-planar imaging (EPI), which are resolution-limited and suffer from distortions caused by resonance offsets. Multi-shot methods may improve the images but require time-consuming navigators or a trade-off of the sensitivity encoding to measure shot-dependent phase errors. We have recently introduced an alternative approach to multi-shot MRI called phaseless encoding, which, by analogy to optical super-resolution methods, relies on the magnitude value of images taken in different shots thus discarding the phase error without navigators, and demonstrated its capability to perform diffusion MRI at sub-millimeter scale on a standard 3T scanner. In this work, we apply phaseless encoding in a routine diffusion tensor imaging (DTI) protocol with a moderately high resolution that is still within reach of single-shot EPI with the same hardware, and compare both techniques with respect to image distortions. A qualitative comparison of the phaseless encoding with the established navigator-based readout-segmented EPI is also presented. Several technical improvements are proposed to make phaseless encoding compatible with the routine scanning mode. The tagging radiofrequency pulses used in the encoding sequence are made slice-selective to avoid artefacts caused by saturation effects in multi-slice scans and their flip angle is optimized to reduce the intrinsic SNR loss. The super-resolution reconstruction algorithm is also improved to better suppress Gibbs ringing and to correct for possible signal amplitude fluctuations. Our study shows that the phaseless encoding is a promising approach to diffusion weighted imaging. It can easily be implemented in multi-slice sequences and produces less distorted images than the single-shot EPI at the same resolution and hardware parameters. It provides similar results to readout-segmented EPI but without the need of navigators.
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Affiliation(s)
- Rui Tian
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.
| | - Franciszek Hennel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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Weiger M, Pruessmann KP. Short-T 2 MRI: Principles and recent advances. Prog Nucl Magn Reson Spectrosc 2019; 114-115:237-270. [PMID: 31779882 DOI: 10.1016/j.pnmrs.2019.07.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/14/2019] [Accepted: 07/26/2019] [Indexed: 06/10/2023]
Abstract
Among current modalities of biomedical and diagnostic imaging, MRI stands out by virtue of its versatile contrast obtained without ionizing radiation. However, in various cases, e.g., water protons in tissues such as bone, tendon, and lung, MRI performance is limited by the rapid decay of resonance signals associated with short transverse relaxation times T2 or T2*. Efforts to address this shortcoming have led to a variety of specialized short-T2 techniques. Recent progress in this field expands the choice of methods and prompts fresh considerations with regard to instrumentation, data acquisition, and signal processing. In this review, the current status of short-T2 MRI is surveyed. In an attempt to structure the growing range of techniques, the presentation highlights overarching concepts and basic methodological options. The most frequently used approaches are described in detail, including acquisition strategies, image reconstruction, hardware requirements, means of introducing contrast, sources of artifacts, limitations, and applications.
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Affiliation(s)
- Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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Tezcan KC, Baumgartner CF, Luechinger R, Pruessmann KP, Konukoglu E. MR Image Reconstruction Using Deep Density Priors. IEEE Trans Med Imaging 2019; 38:1633-1642. [PMID: 30571618 DOI: 10.1109/tmi.2018.2887072] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Algorithms for magnetic resonance (MR) image reconstruction from undersampled measurements exploit prior information to compensate for missing k-space data. Deep learning (DL) provides a powerful framework for extracting such information from existing image datasets, through learning, and then using it for reconstruction. Leveraging this, recent methods employed DL to learn mappings from undersampled to fully sampled images using paired datasets, including undersampled and corresponding fully sampled images, integrating prior knowledge implicitly. In this letter, we propose an alternative approach that learns the probability distribution of fully sampled MR images using unsupervised DL, specifically variational autoencoders (VAE), and use this as an explicit prior term in reconstruction, completely decoupling the encoding operation from the prior. The resulting reconstruction algorithm enjoys a powerful image prior to compensate for missing k-space data without requiring paired datasets for training nor being prone to associated sensitivities, such as deviations in undersampling patterns used in training and test time or coil settings. We evaluated the proposed method with T1 weighted images from a publicly available dataset, multi-coil complex images acquired from healthy volunteers ( N=8 ), and images with white matter lesions. The proposed algorithm, using the VAE prior, produced visually high quality reconstructions and achieved low RMSE values, outperforming most of the alternative methods on the same dataset. On multi-coil complex data, the algorithm yielded accurate magnitude and phase reconstruction results. In the experiments on images with white matter lesions, the method faithfully reconstructed the lesions.
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Penn A, Boyce CM, Conzelmann N, Bezinge G, Pruessmann KP, Müller CR. Real-time magnetic resonance imaging of fluidized beds with internals. Chem Eng Sci 2019. [DOI: 10.1016/j.ces.2018.12.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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31
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Quevenco FC, Schreiner SJ, Preti MG, van Bergen JMG, Kirchner T, Wyss M, Steininger SC, Gietl A, Leh SE, Buck A, Pruessmann KP, Hock C, Nitsch RM, Henning A, Van De Ville D, Unschuld PG. GABA and glutamate moderate beta-amyloid related functional connectivity in cognitively unimpaired old-aged adults. Neuroimage Clin 2019; 22:101776. [PMID: 30927605 PMCID: PMC6439267 DOI: 10.1016/j.nicl.2019.101776] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 02/03/2019] [Accepted: 03/10/2019] [Indexed: 02/08/2023]
Abstract
Background Effects of beta-amyloid accumulation on neuronal function precede the clinical manifestation of Alzheimer's disease (AD) by years and affect distinct cognitive brain networks. As previous studies suggest a link between beta-amyloid and dysregulation of excitatory and inhibitory neurotransmitters, we aimed to investigate the impact of GABA and glutamate on beta-amyloid related functional connectivity. Methods 29 cognitively unimpaired old-aged adults (age = 70.03 ± 5.77 years) were administered 11C-Pittsburgh Compound B (PiB) positron-emission tomography (PET), and MRI at 7 Tesla (7T) including blood oxygen level dependent (BOLD) functional MRI (fMRI) at rest for measuring static and dynamic functional connectivity. An advanced 7T MR spectroscopic imaging (MRSI) sequence based on the free induction decay acquisition localized by outer volume suppression’ (FIDLOVS) technology was used for gray matter specific measures of GABA and glutamate in the posterior cingulate and precuneus (PCP) region. Results GABA and glutamate MR-spectra indicated significantly higher levels in gray matter than in white matter. A global effect of beta-amyloid on functional connectivity in the frontal, occipital and inferior temporal lobes was observable. Interactive effects of beta-amyloid with gray matter GABA displayed positive PCP connectivity to the frontomedial regions, and the interaction of beta-amyloid with gray matter glutamate indicated positive PCP connectivity to frontal and cerebellar regions. Furthermore, decreased whole-brain but increased fronto-occipital and temporo-parietal dynamic connectivity was found, when GABA interacted with regional beta-amyloid deposits in the amygdala, frontal lobe, hippocampus, insula and striatum. Conclusions GABA, and less so glutamate, may moderate beta-amyloid related functional connectivity. Additional research is needed to better characterize their interaction and potential impact on AD. Combined ultra-high fieldstrength FIDLOVS MRSI at 7 Tesla with 11C-PIB PET. Assessment of gray matter specific levels of GABA and glutamate. Identification of interactive effects of GABA, glutamate and beta-Amyloid. GABA may moderate dysfunctional beta-Amyloid effects on pre-clinical brain pathology.
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Affiliation(s)
- F C Quevenco
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - S J Schreiner
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland
| | - M G Preti
- Department of Radiology and Medical Informatics, Université de Genève, Switzerland; Institute of Bioengineering, École polytechnique fédérale de Lausanne, Switzerland
| | - J M G van Bergen
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - T Kirchner
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - M Wyss
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - S C Steininger
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland
| | - A Gietl
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - S E Leh
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland
| | - A Buck
- Division of Nuclear Medicine, University Hospital Zurich (USZ), Zurich, Switzerland
| | - K P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland; Neuroscience Center Zurich (ZNZ), Zurich, Switzerland
| | - C Hock
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland; Neuroscience Center Zurich (ZNZ), Zurich, Switzerland
| | - R M Nitsch
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland; Neuroscience Center Zurich (ZNZ), Zurich, Switzerland
| | - A Henning
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland; Max Planck Institute for Biological Cybernetics, Tubingen, Germany
| | - D Van De Ville
- Department of Radiology and Medical Informatics, Université de Genève, Switzerland; Institute of Bioengineering, École polytechnique fédérale de Lausanne, Switzerland
| | - P G Unschuld
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland; Neuroscience Center Zurich (ZNZ), Zurich, Switzerland.
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Hua J, Lee S, Blair NIS, Wyss M, van Bergen JMG, Schreiner SJ, Kagerer SM, Leh SE, Gietl AF, Treyer V, Buck A, Nitsch RM, Pruessmann KP, Lu H, Van Zijl PCM, Albert M, Hock C, Unschuld PG. Increased cerebral blood volume in small arterial vessels is a correlate of amyloid-β-related cognitive decline. Neurobiol Aging 2019; 76:181-193. [PMID: 30738323 DOI: 10.1016/j.neurobiolaging.2019.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 01/01/2019] [Accepted: 01/02/2019] [Indexed: 12/22/2022]
Abstract
The protracted accumulation of amyloid-β (Aβ) is a major pathologic hallmark of Alzheimer's disease and may trigger secondary pathological processes that include neurovascular damage. This study was aimed at investigating long-term effects of Aβ burden on cerebral blood volume of arterioles and pial arteries (CBVa), possibly present before manifestation of dementia. Aβ burden was assessed by 11C Pittsburgh compound-B positron emission tomography in 22 controls and 18 persons with mild cognitive impairment (MCI), [ages: 75(±6) years]. After 2 years, inflow-based vascular space occupancy at ultra-high field strength of 7-Tesla was administered for measuring CBVa, and neuropsychological testing for cognitive decline. Crushing gradients were incorporated during MR-imaging to suppress signals from fast-flowing blood in large arteries, and thereby sensitize inflow-based vascular space occupancy to CBVa in pial arteries and arterioles. CBVa was significantly elevated in MCI compared to cognitively normal controls and regional CBVa related to local Aβ deposition. For both MCI and controls, Aβ burden and follow-up CBVa in several brain regions synergistically predicted cognitive decline over 2 years. Orbitofrontal CBVa was positively associated with apolipoprotein E e4 carrier status. Increased CBVa may reflect long-term effects of region-specific pathology associated with Aβ deposition. Additional studies are needed to clarify the role of the arteriolar system and the potential of CBVa as a biomarker for Aβ-related vascular downstream pathology.
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Affiliation(s)
- Jun Hua
- Neurosection, Division of MRI Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - SeungWook Lee
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Nicholas I S Blair
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Michael Wyss
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Jiri M G van Bergen
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland
| | - Simon J Schreiner
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland
| | - Sonja M Kagerer
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland
| | - Sandra E Leh
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland
| | - Anton F Gietl
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland
| | - Valerie Treyer
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland; Department of Nuclear Medicine, University Hospital Zurich, Switzerland
| | - Alfred Buck
- Department of Nuclear Medicine, University Hospital Zurich, Switzerland
| | - Roger M Nitsch
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Hanzhang Lu
- Neurosection, Division of MRI Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Peter C M Van Zijl
- Neurosection, Division of MRI Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Marilyn Albert
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Christoph Hock
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland
| | - Paul G Unschuld
- Institute for Regenerative Medicine (IREM), University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, Psychiatric University Hospital Zurich (PUK), Zurich, Switzerland.
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Frässle S, Lomakina EI, Kasper L, Manjaly ZM, Leff A, Pruessmann KP, Buhmann JM, Stephan KE. A generative model of whole-brain effective connectivity. Neuroimage 2018; 179:505-529. [DOI: 10.1016/j.neuroimage.2018.05.058] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 05/16/2018] [Accepted: 05/24/2018] [Indexed: 12/17/2022] Open
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Penn A, Boyce CM, Kovar T, Tsuji T, Pruessmann KP, Müller CR. Real-Time Magnetic Resonance Imaging of Bubble Behavior and Particle Velocity in Fluidized Beds. Ind Eng Chem Res 2018. [DOI: 10.1021/acs.iecr.8b00932] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexander Penn
- Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - Christopher M. Boyce
- Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
- Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
| | - Thomas Kovar
- Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
| | - Takuya Tsuji
- Department of Mechanical Engineering, Osaka University, Osaka 565-0871, Japan
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - Christoph R. Müller
- Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
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Hennel F, Tian R, Engel M, Pruessmann KP. In-plane "superresolution" MRI with phaseless sub-pixel encoding. Magn Reson Med 2018; 80:2384-2392. [PMID: 29656440 DOI: 10.1002/mrm.27209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 03/13/2018] [Accepted: 03/13/2018] [Indexed: 12/13/2022]
Abstract
PURPOSE Acquisition of high-resolution imaging data using multiple excitations without the sensitivity to fluctuations of the transverse magnetization phase, which is a major problem of multi-shot MRI. THEORY AND METHODS The concept of superresolution MRI based on microscopic tagging is analyzed using an analogy with the optical method of structured illumination. Sinusoidal tagging is shown to provide subpixel resolution by mixing of neighboring spatial frequency (k-space) bands. It represents a phaseless modulation added on top of the standard Fourier encoding, which allows the phase fluctuations to be discarded at an intermediate reconstruction step. Improvements are proposed to correct for tag distortions due to magnetic field inhomogeneity and to avoid the propagation of Gibbs ringing from intermediate low-resolution images to the final image. The method was applied to diffusion-weighted EPI. RESULTS Artifact-free superresolution images can be obtained despite a finite duration of the tagging sequence and related pattern distortions by a field map based phase correction of band-wise reconstructed images. The ringing effect present in the intermediate images can be suppressed by partial overlapping of the mixed k-space bands in combination with an adapted filter. High-resolution diffusion-weighted images of the human head were obtained with a three-shot EPI sequence despite motion-related phase fluctuations between the shots. CONCLUSION Due to its phaseless character, tagging-based sub-pixel encoding is an alternative to k-space segmenting in the presence of unknown phase fluctuations, in particular those due to motion under strong diffusion gradients. Proposed improvements render the method practicable in realistic conditions.
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Affiliation(s)
- Franciszek Hennel
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Rui Tian
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Maria Engel
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
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Engel M, Kasper L, Barmet C, Schmid T, Vionnet L, Wilm B, Pruessmann KP. Single‐shot spiral imaging at 7
T. Magn Reson Med 2018; 80:1836-1846. [DOI: 10.1002/mrm.27176] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 02/15/2018] [Accepted: 02/18/2018] [Indexed: 01/18/2023]
Affiliation(s)
- Maria Engel
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
| | - Lars Kasper
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
- Translational Neuromodeling Unit, Institute for Biomedical EngineeringUniversity of Zurich and ETH ZurichZurich Switzerland
| | - Christoph Barmet
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
- Skope Magnetic Resonance Technologies AGZurich Switzerland
| | - Thomas Schmid
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
| | - Laetitia Vionnet
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
| | - Bertram Wilm
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
- Skope Magnetic Resonance Technologies AGZurich Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
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Looser A, Barmet C, Fox T, Blacque O, Gross S, Nussbaum J, Pruessmann KP, Alberto R. Ultrafast Ligand Self-Exchanging Gadolinium Complexes in Ionic Liquids for NMR Field Probes. Inorg Chem 2018; 57:2314-2319. [DOI: 10.1021/acs.inorgchem.7b03191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anna Looser
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Christoph Barmet
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
- Skope Magnetic Resonance Technologies AG, Gladbachstrasse 105, CH-8044 Zurich, Switzerland
| | - Thomas Fox
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Olivier Blacque
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Simon Gross
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Jennifer Nussbaum
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Klaas P. Pruessmann
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Roger Alberto
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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Marjanovic J, Weiger M, Reber J, Brunner DO, Dietrich BE, Wilm BJ, Froidevaux R, Pruessmann KP. Multi-Rate Acquisition for Dead Time Reduction in Magnetic Resonance Receivers: Application to Imaging With Zero Echo Time. IEEE Trans Med Imaging 2018; 37:408-416. [PMID: 28910759 DOI: 10.1109/tmi.2017.2750208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
For magnetic resonance imaging of tissues with very short transverse relaxation times, radio-frequency excitation must be immediately followed by data acquisition with fast spatial encoding. In zero-echo-time (ZTE) imaging, excitation is performed while the readout gradient is already on, causing data loss due to an initial dead time. One major dead time contribution is the settling time of the filters involved in signal down-conversion. In this paper, a multi-rate acquisition scheme is proposed to minimize dead time due to filtering. Short filters and high output bandwidth are used initially to minimize settling time. With increasing time since the signal onset, longer filters with better frequency selectivity enable stronger signal decimation. In this way, significant dead time reduction is accomplished at only a slight increase in the overall amount of output data. Multi-rate acquisition was implemented with a two-stage filter cascade in a digital receiver based on a field-programmable gate array. In ZTE imaging in a phantom and in vivo, dead time reduction by multi-rate acquisition is shown to improve image quality and expand the feasible bandwidth while increasing the amount of data collected by only a few percent.
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Schreiner SJ, Kirchner T, Narkhede A, Wyss M, Van Bergen JMG, Steininger SC, Gietl A, Leh SE, Treyer V, Buck A, Pruessmann KP, Nitsch RM, Hock C, Henning A, Brickman AM, Unschuld PG. Brain amyloid burden and cerebrovascular disease are synergistically associated with neurometabolism in cognitively unimpaired older adults. Neurobiol Aging 2017; 63:152-161. [PMID: 29310864 DOI: 10.1016/j.neurobiolaging.2017.12.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 11/16/2017] [Accepted: 12/04/2017] [Indexed: 01/08/2023]
Abstract
Alzheimer's disease (AD) is the most common cause of cognitive dysfunction in older adults. The pathological hallmarks of AD such as beta amyloid (Aβ) aggregation and neurometabolic change, as indicated by altered myo-inositol (mI) and N-acetylaspartate (NAA) levels, typically precede the onset of cognitive dysfunction by years. Furthermore, cerebrovascular disease occurs early in AD, but the interplay between vascular and neurometabolic brain change is largely unknown. Thirty cognitively normal older adults (age = 70 ± 5.6 years, Mini-Mental State Examination = 29.2 ± 1) received 11-C-Pittsburgh Compound B positron emission tomography for estimating Aβ-plaque density, 7 Tesla fluid-attenuated inversion recovery magnetic resonance imaging for quantifying white matter hyperintensity volume as a marker of small vessel cerebrovascular disease and high-resolution magnetic resonance spectroscopic imaging at 7 Tesla, based on free induction decay acquisition localized by outer volume suppression to investigate tissue-specific neurometabolism in the posterior cingulate and precuneus. Aβ (β = 0.45, p = 0.018) and white matter hyperintensities (β = 0.40, p = 0.046) were independently and interactively (β = -0.49, p = 0.026) associated with a higher ratio of mI over NAA (mI/NAA) in the posterior cingulate and precuneus gray matter but not in the white matter. Our data suggest that cerebrovascular disease and Aβ burden are synergistically associated with AD-related gray matter neurometabolism in older adults.
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Affiliation(s)
- Simon J Schreiner
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Thomas Kirchner
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Atul Narkhede
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, College of Physicians and Surgeons, Columbia University, NY
| | - Michael Wyss
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Jiri M G Van Bergen
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Stephanie C Steininger
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Anton Gietl
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Sandra E Leh
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Valerie Treyer
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Alfred Buck
- Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Roger M Nitsch
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Christoph Hock
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
| | - Anke Henning
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland; Max Planck Institute for Biological Cybernetics, Tubingen, Germany
| | - Adam M Brickman
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, College of Physicians and Surgeons, Columbia University, NY.
| | - Paul G Unschuld
- Institute for Regenerative Medicine, University of Zurich, Schlieren, Switzerland; Hospital for Psychogeriatric Medicine, University of Zurich, Zurich, Switzerland
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Sporrer B, Wu L, Bettini L, Vogt C, Reber J, Marjanovic J, Burger T, Brunner DO, Pruessmann KP, Troster G, Huang Q. A Fully Integrated Dual-Channel On-Coil CMOS Receiver for Array Coils in 1.5-10.5 T MRI. IEEE Trans Biomed Circuits Syst 2017; 11:1245-1255. [PMID: 29293422 DOI: 10.1109/tbcas.2017.2764443] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Magnetic resonance imaging (MRI) is among the most important medical imaging modalities. Coil arrays and receivers with high channel counts (16 and more) have to be deployed to obtain the image quality and acquisition speed required by modern clinical protocols. In this paper, we report the theoretical analysis, the system-level design, and the circuit implementation of the first receiver IC (RXIC) for clinical MRI fully integrated in a modern CMOS technology. The dual-channel RXIC sits directly on the sensor coil, thus eliminating any RF cable otherwise required to transport the information out of the magnetic field. The first stage LNA was implemented using a noise-canceling architecture providing a highly reflective input used to decouple the individual channels of the array. Digitization is performed directly on-chip at base-band by means of a delta-sigma modulator, allowing the subsequent optical transmission of data. The presented receiver, implemented in a CMOS technology, is compatible with MRI scanners up to . It reaches sub- noise figure for MRI units and features a dynamic range up to at a power consumption below per channel, with an area occupation of . Mounted on a small-sized printed circuit board (PCB), the receiver IC has been employed in a commercial MRI scanner to acquire in-vivo images matching the quality of traditional systems, demonstrating the first step toward multichannel wearable MRI array coils.
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Stephan KE, Petzschner FH, Kasper L, Bayer J, Wellstein KV, Stefanics G, Pruessmann KP, Heinzle J. Laminar fMRI and computational theories of brain function. Neuroimage 2017; 197:699-706. [PMID: 29104148 DOI: 10.1016/j.neuroimage.2017.11.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 10/29/2017] [Accepted: 11/01/2017] [Indexed: 12/20/2022] Open
Abstract
Recently developed methods for functional MRI at the resolution of cortical layers (laminar fMRI) offer a novel window into neurophysiological mechanisms of cortical activity. Beyond physiology, laminar fMRI also offers an unprecedented opportunity to test influential theories of brain function. Specifically, hierarchical Bayesian theories of brain function, such as predictive coding, assign specific computational roles to different cortical layers. Combined with computational models, laminar fMRI offers a unique opportunity to test these proposals noninvasively in humans. This review provides a brief overview of predictive coding and related hierarchical Bayesian theories, summarises their predictions with regard to layered cortical computations, examines how these predictions could be tested by laminar fMRI, and considers methodological challenges. We conclude by discussing the potential of laminar fMRI for clinically useful computational assays of layer-specific information processing.
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Affiliation(s)
- K E Stephan
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland; Wellcome Trust Centre for Neuroimaging, University College London, London, WC1N 3BG, UK.
| | - F H Petzschner
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland
| | - L Kasper
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland; Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - J Bayer
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland; Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - K V Wellstein
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland
| | - G Stefanics
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland; Laboratory for Social and Neural Systems Research (SNS), Dept. of Economics, University of Zurich, 8006 Zurich, Switzerland
| | - K P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - J Heinzle
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich & ETH Zurich, 8032 Zurich, Switzerland
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Weiger M, Overweg J, Rösler MB, Froidevaux R, Hennel F, Wilm BJ, Penn A, Sturzenegger U, Schuth W, Mathlener M, Borgo M, Börnert P, Leussler C, Luechinger R, Dietrich BE, Reber J, Brunner DO, Schmid T, Vionnet L, Pruessmann KP. A high-performance gradient insert for rapid and short-T2
imaging at full duty cycle. Magn Reson Med 2017; 79:3256-3266. [DOI: 10.1002/mrm.26954] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/06/2017] [Accepted: 09/12/2017] [Indexed: 01/07/2023]
Affiliation(s)
- Markus Weiger
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Johan Overweg
- Philips GmbH Innovative Technologies; Hamburg Germany
| | - Manuela Barbara Rösler
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Romain Froidevaux
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Franciszek Hennel
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Bertram Jakob Wilm
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Alexander Penn
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | | | - Wout Schuth
- Futura Composites BV; Heerhugowaard The Netherlands
| | | | | | - Peter Börnert
- Philips GmbH Innovative Technologies; Hamburg Germany
| | | | - Roger Luechinger
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | | | - Jonas Reber
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - David Otto Brunner
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Laetitia Vionnet
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Zurich Switzerland
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Penn A, Tsuji T, Brunner DO, Boyce CM, Pruessmann KP, Müller CR. Real-time probing of granular dynamics with magnetic resonance. Sci Adv 2017; 3:e1701879. [PMID: 28929140 PMCID: PMC5600527 DOI: 10.1126/sciadv.1701879] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 08/15/2017] [Indexed: 06/07/2023]
Abstract
Granular dynamics govern earthquakes, avalanches, and landslides and are of fundamental importance in a variety of industries ranging from energy to pharmaceuticals to agriculture. Nonetheless, our understanding of the underlying physics is poor because we lack spatially and temporally resolved experimental measurements of internal grain motion. We introduce a magnetic resonance imaging methodology that provides internal granular velocity measurements that are four orders of magnitude faster compared to previous work. The technique is based on a concerted interplay of scan acceleration and materials engineering. Real-time probing of granular dynamics is explored in single- and two-phase systems, providing fresh insight into bubble dynamics and the propagation of shock waves upon impact of an intruder. We anticipate that the methodology outlined here will enable advances in understanding the propagation of seismic activity, the jamming transition, or the rheology and dynamics of dense suspensions.
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Affiliation(s)
- Alexander Penn
- Laboratory of Energy Science and Engineering, ETH Zürich, Leonhardstrasse 27, 8092 Zürich, Switzerland
- Institute for Biomedical Engineering, University of Zürich and ETH Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland
| | - Takuya Tsuji
- Department of Mechanical Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - David O. Brunner
- Institute for Biomedical Engineering, University of Zürich and ETH Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland
| | - Christopher M. Boyce
- Laboratory of Energy Science and Engineering, ETH Zürich, Leonhardstrasse 27, 8092 Zürich, Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering, University of Zürich and ETH Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland
| | - Christoph R. Müller
- Laboratory of Energy Science and Engineering, ETH Zürich, Leonhardstrasse 27, 8092 Zürich, Switzerland
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44
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Froidevaux R, Weiger M, Brunner DO, Dietrich BE, Wilm BJ, Pruessmann KP. Filling the dead-time gap in zero echo time MRI: Principles compared. Magn Reson Med 2017; 79:2036-2045. [PMID: 28856717 DOI: 10.1002/mrm.26875] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 07/24/2017] [Accepted: 07/27/2017] [Indexed: 11/07/2022]
Abstract
PURPOSE MRI of tissues with short coherence lifetimes T2 or T2* can be performed efficiently using zero echo time (ZTE) techniques such as algebraic ZTE, pointwise encoding time reduction with radial acquisition (PETRA), and water- and fat-suppressed proton projection MRI (WASPI). They share the principal challenge of recovering data in central k-space missed due to an initial radiofrequency dead time. The purpose of this study was to compare the three techniques directly, with a particular focus on their behavior in the presence of ultra-short-lived spins. METHODS The most direct comparison was enabled by aligning acquisition and reconstruction strategies of the three techniques. Image quality and short- T2* performance were investigated using point spread functions, 3D simulations, and imaging of phantom and bone samples with short (<1 ms) and ultra-short (<100 μs) T2*. RESULTS Algebraic ZTE offers favorable properties but is limited to k-space gaps up to approximately three Nyquist dwells. At larger gaps, PETRA enables robust imaging with little compromise in image quality, whereas WASPI may be prone to artifacts from ultra-short T2* species. CONCLUSION For small k-space gaps (<4 dwells) and T2* much larger than the dead time, all techniques enable artifact-free short- T2* MRI. However, if these requirements are not fulfilled careful consideration is needed and PETRA will generally achieve better image quality. Magn Reson Med 79:2036-2045, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Romain Froidevaux
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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45
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Aranovitch A, Haeberlin M, Gross S, Dietrich BE, Wilm BJ, Brunner DO, Schmid T, Luechinger R, Pruessmann KP. Prospective motion correction with NMR markers using only native sequence elements. Magn Reson Med 2017; 79:2046-2056. [PMID: 28840611 DOI: 10.1002/mrm.26877] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/27/2017] [Accepted: 07/29/2017] [Indexed: 12/20/2022]
Abstract
PURPOSE To develop a method of tracking active NMR markers that requires no alterations of common imaging sequences and can be used for prospective motion correction (PMC) in brain MRI. METHODS Localization of NMR markers is achieved by acquiring short signal snippets in rapid succession and evaluating them jointly. To spatially encode the markers, snippets are timed such that signal phase is accrued during sequence intervals with suitably diverse gradient actuation. For motion tracking and PMC in brain imaging, the markers are mounted on a lightweight headset. PMC is then demonstrated with high-resolution T2 *- and T1 -weighted imaging sequences in the presence of instructed as well as residual unintentional head motion. RESULTS With both unaltered sequences, motion tracking was achieved with precisions on the order of 10 µm and 0.01° and temporal resolution of 48 and 39 ms, respectively. On this basis, PMC improved image quality significantly throughout. CONCLUSION The proposed approach permits high-precision motion tracking and PMC with standard imaging sequences. It does so without altering sequence design and thus overcomes a key hindrance to routine motion tracking with NMR markers. Magn Reson Med 79:2046-2057, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Alexander Aranovitch
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Maximilian Haeberlin
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Roger Luechinger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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46
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Kasper L, Engel M, Barmet C, Haeberlin M, Wilm BJ, Dietrich BE, Schmid T, Gross S, Brunner DO, Stephan KE, Pruessmann KP. Rapid anatomical brain imaging using spiral acquisition and an expanded signal model. Neuroimage 2017; 168:88-100. [PMID: 28774650 DOI: 10.1016/j.neuroimage.2017.07.062] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 06/22/2017] [Accepted: 07/29/2017] [Indexed: 11/30/2022] Open
Abstract
We report the deployment of spiral acquisition for high-resolution structural imaging at 7T. Long spiral readouts are rendered manageable by an expanded signal model including static off-resonance and B0 dynamics along with k-space trajectories and coil sensitivity maps. Image reconstruction is accomplished by inversion of the signal model using an extension of the iterative non-Cartesian SENSE algorithm. Spiral readouts up to 25 ms are shown to permit whole-brain 2D imaging at 0.5 mm in-plane resolution in less than a minute. A range of options is explored, including proton-density and T2* contrast, acceleration by parallel imaging, different readout orientations, and the extraction of phase images. Results are shown to exhibit competitive image quality along with high geometric consistency.
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Affiliation(s)
- Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland; Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zurich, Switzerland.
| | - Maria Engel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland; Skope Magnetic Resonance Technologies AG, Zurich, Switzerland
| | - Maximilian Haeberlin
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas E Stephan
- Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zurich, Switzerland; Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom; Max Planck Institute for Metabolism Research, Cologne, Germany
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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Vogt C, Reber J, Waltisberg D, Buthe L, Marjanovic J, Munzenrieder N, Pruessmann KP, Troster G. A wearable bluetooth LE sensor for patient monitoring during MRI scans. Annu Int Conf IEEE Eng Med Biol Soc 2017; 2016:4975-4978. [PMID: 28269385 DOI: 10.1109/embc.2016.7591844] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper presents a working prototype of a wearable patient monitoring device capable of recording the heart rate, blood oxygen saturation, surface temperature and humidity during an magnetic resonance imaging (MRI) experiment. The measured values are transmitted via Bluetooth low energy (LE) and displayed in real time on a smartphone on the outside of the MRI room. During 7 MRI image acquisitions of at least 1 min and a total duration of 25 min no Bluetooth data packets were lost. The raw measurements of the light intensity for the photoplethysmogram based heart rate measurement shows an increased noise floor by 50LSB (least significant bit) during the MRI operation, whereas the temperature and humidity readings are unaffected. The device itself creates a magnetic resonance (MR) signal loss with a radius of 14 mm around the device surface and shows no significant increase in image noise of an acquired MRI image due to its radio frequency activity. This enables continuous and unobtrusive patient monitoring during MRI scans.
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48
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Çavuşoğlu M, Mooiweer R, Pruessmann KP, Malik SJ. VERSE-guided parallel RF excitations using dynamic field correction. NMR Biomed 2017; 30:e3697. [PMID: 28211968 PMCID: PMC5484370 DOI: 10.1002/nbm.3697] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 11/24/2016] [Accepted: 12/29/2016] [Indexed: 06/06/2023]
Abstract
In parallel RF pulse design, peak RF magnitudes and specific absorption rate levels are critical concerns in the hardware and safety limits. The variable rate selective excitation (VERSE) method is an efficient technique to limit the peak RF power by applying a local-only RF and gradient waveform reshaping while retaining the on-resonance profile. The accuracy of the excitation performed by the VERSEd RF and gradient waveforms strictly depends on the performance of the employed hardware. Any deviation from the nominal gradient fields as a result of frequency dependent system imperfections violates the VERSE condition similarly to off-resonance effects, leading to significant excitation errors and the RF pulse not converging to the targeted peak RF power. Moreover, for iterative VERSE-guided RF pulse design (i.e. reVERSE), the k-space trajectory actually changes at every iteration, which is assumed to be constant. In this work, we show both theoretically and experimentally the effect of gradient system imperfections on iteratively VERSEd parallel RF excitations. In order to improve the excitation accuracy besides limiting the RF power below certain thresholds, we propose to integrate gradient field monitoring or gradient impulse response function (GIRF) estimations of the actual gradient fields into the RF pulse design problem. A third-order dynamic field camera comprising a set of NMR field sensors and GIRFs was used to measure or estimate the actual gradient waveforms that are involved in the VERSE algorithm respectively. The deviating and variable k-space is counteracted at each iteration of the VERSE-guided iterative RF pulse design. The proposed approaches are demonstrated for accelerated multiple-channel spatially selective RF pulses, and highly improved experimental performance was achieved at both 3 T and 7 T.
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Affiliation(s)
- Mustafa Çavuşoğlu
- Institute for Biomedical EngineeringUniversity and ETH ZürichZürichSwitzerland
| | - Ronald Mooiweer
- Division of Imaging Sciences and Biomedical Engineering, King's College LondonSt. Thomas' HospitalLondonUK
- Center for Image SciencesUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Klaas P. Pruessmann
- Institute for Biomedical EngineeringUniversity and ETH ZürichZürichSwitzerland
| | - Shaihan J. Malik
- Division of Imaging Sciences and Biomedical Engineering, King's College LondonSt. Thomas' HospitalLondonUK
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Gross S, Barmet C, Dietrich BE, Brunner DO, Schmid T, Pruessmann KP. Correction: Corrigendum: Dynamic nuclear magnetic resonance field sensing with part-per-trillion resolution. Nat Commun 2017; 8:14746. [PMID: 28240281 PMCID: PMC5333354 DOI: 10.1038/ncomms14746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Quevenco FC, Preti MG, van Bergen JMG, Hua J, Wyss M, Li X, Schreiner SJ, Steininger SC, Meyer R, Meier IB, Brickman AM, Leh SE, Gietl AF, Buck A, Nitsch RM, Pruessmann KP, van Zijl PCM, Hock C, Van De Ville D, Unschuld PG. Memory performance-related dynamic brain connectivity indicates pathological burden and genetic risk for Alzheimer's disease. Alzheimers Res Ther 2017; 9:24. [PMID: 28359293 PMCID: PMC5374623 DOI: 10.1186/s13195-017-0249-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 02/27/2017] [Indexed: 11/10/2022]
Abstract
BACKGROUND The incidence of Alzheimer's disease (AD) strongly relates to advanced age and progressive deposition of cerebral amyloid-beta (Aβ), hyperphosphorylated tau, and iron. The purpose of this study was to investigate the relationship between cerebral dynamic functional connectivity and variability of long-term cognitive performance in healthy, elderly subjects, allowing for local pathology and genetic risk. METHODS Thirty seven participants (mean (SD) age 74 (6.0) years, Mini-Mental State Examination 29.0 (1.2)) were dichotomized based on repeated neuropsychological test performance within 2 years. Cerebral Aβ was measured by 11C Pittsburgh Compound-B positron emission tomography, and iron by quantitative susceptibility mapping magnetic resonance imaging (MRI) at an ultra-high field strength of 7 Tesla (7T). Dynamic functional connectivity patterns were investigated by resting-state functional MRI at 7T and tested for interactive effects with genetic AD risk (apolipoprotein E (ApoE)-ε4 carrier status). RESULTS A relationship between low episodic memory and a lower expression of anterior-posterior connectivity was seen (F(9,27) = 3.23, p < 0.008), moderated by ApoE-ε4 (F(9,27) = 2.22, p < 0.005). Inherent node-strength was related to local iron (F(5,30) = 13.2; p < 0.022). CONCLUSION Our data indicate that altered dynamic anterior-posterior brain connectivity is a characteristic of low memory performance in the subclinical range and genetic risk for AD in the elderly. As the observed altered brain network properties are associated with increased local iron, our findings may reflect secondary neuronal changes due to pathologic processes including oxidative stress.
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Affiliation(s)
- Frances C Quevenco
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - Maria G Preti
- Department of Radiology and Medical Informatics, Université de Genève, Geneva, Switzerland.,Institute of Bioengineering, École polytechnique fédérale de Lausanne, Lausanne, Switzerland
| | - Jiri M G van Bergen
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - Jun Hua
- Department of Radiology, Johns Hopkins School of Medicine and F.M. Kirby Center for Functional Brain Imaging at Kennedy Krieger Institute, Baltimore, MD, USA
| | - Michael Wyss
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Xu Li
- Department of Radiology, Johns Hopkins School of Medicine and F.M. Kirby Center for Functional Brain Imaging at Kennedy Krieger Institute, Baltimore, MD, USA
| | - Simon J Schreiner
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Stefanie C Steininger
- Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Rafael Meyer
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Irene B Meier
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - Adam M Brickman
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, USA
| | - Sandra E Leh
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Anton F Gietl
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Alfred Buck
- Division of Nuclear Medicine, University of Zurich, Zurich, Switzerland
| | - Roger M Nitsch
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Peter C M van Zijl
- Department of Radiology, Johns Hopkins School of Medicine and F.M. Kirby Center for Functional Brain Imaging at Kennedy Krieger Institute, Baltimore, MD, USA
| | - Christoph Hock
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland
| | - Dimitri Van De Ville
- Department of Radiology and Medical Informatics, Université de Genève, Geneva, Switzerland.,Institute of Bioengineering, École polytechnique fédérale de Lausanne, Lausanne, Switzerland
| | - Paul G Unschuld
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland. .,Hospital for Psychogeriatric Medicine, University of Zurich, Minervastr.145, CH-8032, Zurich, Switzerland.
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