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Riedel M, Ulrich T, Pruessmann KP. Run-time motion and first-order shim control by expanded servo navigation. Magn Reson Med 2024. [PMID: 39188123 DOI: 10.1002/mrm.30262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 07/17/2024] [Accepted: 08/04/2024] [Indexed: 08/28/2024]
Abstract
PURPOSE To provide a navigator-based run-time motion and first-order field correction for three-dimensional human brain imaging with high precision, minimal calibration and acquisition, and fast processing. METHODS A complex-valued linear perturbation model with feedback control is extended to estimate and correct for gradient shim fields using orbital navigators (2.3 ms). Two approaches for sensitizing the model to gradient fields are presented, one based on finite differences with three additional navigators, and another projection-based approximation requiring no additional navigators. A mechanism for noise decorrelation of the matrix and the data is proposed and evaluated to reduce unwanted parameter biases. RESULTS The rigid motion and first-order field control achieves robust motion and gradient shim corrections improving image quality in a series of phantom and in vivo experiments with varying field conditions. In phantom scans, magnet drifts, forced gradient field perturbations and field distortions from shifts of a second bottle phantom are successfully corrected. Field estimates of the magnet drifts are in good agreement with concurrent field probe measurements. For in vivo scans, the proposed method mitigates field variations from torso motions while being robust to head motion. In vivo gradient field precisions were30 nT / m $$ 30\;\mathrm{nT}/\mathrm{m} $$ along with single-digit micrometer and millidegree rigid precisions. CONCLUSION The navigator-based method achieves accurate, high-precision run-time motion and field corrections with low sequence impact and calibration requirements.
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Affiliation(s)
- Malte Riedel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Switzerland
| | - Thomas Ulrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Switzerland
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2
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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] [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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3
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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] [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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4
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Amor Z, Le Ster C, Gr C, Daval-Frérot G, Boulant N, Mauconduit F, Thirion B, Ciuciu P, Vignaud A. Impact of B 0 $$ {\mathrm{B}}_0 $$ field imperfections correction on BOLD sensitivity in 3D-SPARKLING fMRI data. Magn Reson Med 2024; 91:1434-1448. [PMID: 38156952 DOI: 10.1002/mrm.29943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/07/2023] [Accepted: 11/09/2023] [Indexed: 01/03/2024]
Abstract
PURPOSE Static and dynamicB 0 $$ {\mathrm{B}}_0 $$ field imperfections are detrimental to functional MRI (fMRI) applications, especially at ultra-high magnetic fields (UHF). In this work, a field camera is used to assess the benefits of retrospectively correctingB 0 $$ {\mathrm{B}}_0 $$ field perturbations on Blood Oxygen Level Dependent (BOLD) sensitivity in non-Cartesian three-dimensional (3D)-SPARKLING fMRI acquisitions. METHODS fMRI data were acquired at 1 mm3 $$ {}^3 $$ and for a 2.4s-TR while concurrently monitoring in real-time field perturbations using a Skope Clip-on field camera in a novel experimental setting involving a shorter TR than the required minimal TR of the field probes. Measurements of the dynamic field deviations were used along with a staticΔ B 0 $$ \Delta {\mathrm{B}}_0 $$ map to retrospectively correct static and dynamic field imperfections, respectively. In order to evaluate the impact of such a correction on fMRI volumes, a comparative study was conducted on healthy volunteers. RESULTS Correction ofB 0 $$ {\mathrm{B}}_0 $$ deviations improved image quality and yielded between 20% and 30% increase in median temporal signal-to-noise ratio (tSNR).Using fMRI data collected during a retinotopic mapping experiment, we demonstrated a significant increase in sensitivity to the BOLD contrast and improved accuracy of the BOLD phase maps: 44% (resp., 159%) more activated voxels were retrieved when using a significance control level based on a p-value of 0.001 without correcting for multiple comparisons (resp., 0.05 with a false discovery rate correction). CONCLUSION 3D-SPARKLING fMRI hugely benefits from static and dynamicB 0 $$ {\mathrm{B}}_0 $$ imperfections correction. However, the proposed experimental protocol is flexible enough to be deployed on a large spectrum of encoding schemes, including arbitrary non-Cartesian readouts.
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Affiliation(s)
- Zaineb Amor
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Caroline Le Ster
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Chaithya Gr
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
| | - Guillaume Daval-Frérot
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
- Siemens Healthineers, Courbevoie, France
| | - Nicolas Boulant
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Franck Mauconduit
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Bertrand Thirion
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
| | - Philippe Ciuciu
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
| | - Alexandre Vignaud
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
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Madore B, Hess AT, van Niekerk AMJ, Hoinkiss DC, Hucker P, Zaitsev M, Afacan O, Günther M. External Hardware and Sensors, for Improved MRI. J Magn Reson Imaging 2023; 57:690-705. [PMID: 36326548 PMCID: PMC9957809 DOI: 10.1002/jmri.28472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/26/2022] [Accepted: 09/27/2022] [Indexed: 11/06/2022] Open
Abstract
Complex engineered systems are often equipped with suites of sensors and ancillary devices that monitor their performance and maintenance needs. MRI scanners are no different in this regard. Some of the ancillary devices available to support MRI equipment, the ones of particular interest here, have the distinction of actually participating in the image acquisition process itself. Most commonly, such devices are used to monitor physiological motion or variations in the scanner's imaging fields, allowing the imaging and/or reconstruction process to adapt as imaging conditions change. "Classic" examples include electrocardiography (ECG) leads and respiratory bellows to monitor cardiac and respiratory motion, which have been standard equipment in scan rooms since the early days of MRI. Since then, many additional sensors and devices have been proposed to support MRI acquisitions. The main physical properties that they measure may be primarily "mechanical" (eg acceleration, speed, and torque), "acoustic" (sound and ultrasound), "optical" (light and infrared), or "electromagnetic" in nature. A review of these ancillary devices, as currently available in clinical and research settings, is presented here. In our opinion, these devices are not in competition with each other: as long as they provide useful and unique information, do not interfere with each other and are not prohibitively cumbersome to use, they might find their proper place in future suites of sensors. In time, MRI acquisitions will likely include a plurality of complementary signals. A little like the microbiome that provides genetic diversity to organisms, these devices can provide signal diversity to MRI acquisitions and enrich measurements. Machine-learning (ML) algorithms are well suited at combining diverse input signals toward coherent outputs, and they could make use of all such information toward improved MRI capabilities. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 1.
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Affiliation(s)
- Bruno Madore
- Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Aaron T Hess
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Adam MJ van Niekerk
- Karolinska Institutet, Solna, Sweden
- Norwegian University of Science and Technology, Trondheim, Norway
| | | | - Patrick Hucker
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Maxim Zaitsev
- Division of Medical Physics, Department of Diagnostic and Interventional Radiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Onur Afacan
- Computational Radiology Laboratory, Department of Radiology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Matthias Günther
- Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany
- University Bremen, Bremen, Germany
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6
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Laustsen M, Andersen M, Xue R, Madsen KH, Hanson LG. Tracking of rigid head motion during MRI using an EEG system. Magn Reson Med 2022; 88:986-1001. [PMID: 35468237 PMCID: PMC9325421 DOI: 10.1002/mrm.29251] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 02/26/2022] [Accepted: 03/08/2022] [Indexed: 11/21/2022]
Abstract
Purpose To demonstrate a novel method for tracking of head movements during MRI using electroencephalography (EEG) hardware for recording signals induced by native imaging gradients. Theory and Methods Gradient switching during simultaneous EEG–fMRI induces distortions in EEG signals, which depend on subject head position and orientation. When EEG electrodes are interconnected with high‐impedance carbon wire loops, the induced voltages are linear combinations of the temporal gradient waveform derivatives. We introduce head tracking based on these signals (CapTrack) involving 3 steps: (1) phantom scanning is used to characterize the target sequence and a fast calibration sequence; (2) a linear relation between changes of induced signals and head pose is established using the calibration sequence; and (3) induced signals recorded during target sequence scanning are used for tracking and retrospective correction of head movement without prolonging the scan time of the target sequence. Performance of CapTrack is compared directly to interleaved navigators. Results Head‐pose tracking at 27.5 Hz during echo planar imaging (EPI) was demonstrated with close resemblance to rigid body alignment (mean absolute difference: [0.14 0.38 0.15]‐mm translation, [0.30 0.27 0.22]‐degree rotation). Retrospective correction of 3D gradient‐echo imaging shows an increase of average edge strength of 12%/−0.39% for instructed/uninstructed motion with CapTrack pose estimates, with a tracking interval of 1561 ms and high similarity to interleaved navigator estimates (mean absolute difference: [0.13 0.33 0.12] mm, [0.28 0.15 0.22] degrees). Conclusion Motion can be estimated from recordings of gradient switching with little or no sequence modification, optionally in real time at low computational burden and synchronized to image acquisition, using EEG equipment already found at many research institutions.
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Affiliation(s)
- Malte Laustsen
- Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, Denmark.,Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark.,Sino-Danish Centre for Education and Research, Aarhus, Denmark.,University of Chinese Academic of Sciences, Beijing, China
| | - Mads Andersen
- Philips Healthcare, Copenhagen, Denmark.,Lund University Bioimaging Center, Lund University, Lund, Sweden
| | - Rong Xue
- University of Chinese Academic of Sciences, Beijing, China.,State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Beijing Institute for Brain Disorders, Beijing, China
| | - Kristoffer H Madsen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark.,DTU Compute, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Lars G Hanson
- Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, Denmark.,Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark
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7
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Pawar K, Chen Z, Shah NJ, Egan GF. Suppressing motion artefacts in MRI using an Inception-ResNet network with motion simulation augmentation. NMR IN BIOMEDICINE 2022; 35:e4225. [PMID: 31865624 DOI: 10.1002/nbm.4225] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/24/2019] [Accepted: 10/24/2019] [Indexed: 06/10/2023]
Abstract
The suppression of motion artefacts from MR images is a challenging task. The purpose of this paper was to develop a standalone novel technique to suppress motion artefacts in MR images using a data-driven deep learning approach. A simulation framework was developed to generate motion-corrupted images from motion-free images using randomly generated motion profiles. An Inception-ResNet deep learning network architecture was used as the encoder and was augmented with a stack of convolution and upsampling layers to form an encoder-decoder network. The network was trained on simulated motion-corrupted images to identify and suppress those artefacts attributable to motion. The network was validated on unseen simulated datasets and real-world experimental motion-corrupted in vivo brain datasets. The trained network was able to suppress the motion artefacts in the reconstructed images, and the mean structural similarity (SSIM) increased from 0.9058 to 0.9338. The network was also able to suppress the motion artefacts from the real-world experimental dataset, and the mean SSIM increased from 0.8671 to 0.9145. The motion correction of the experimental datasets demonstrated the effectiveness of the motion simulation generation process. The proposed method successfully removed motion artefacts and outperformed an iterative entropy minimization method in terms of the SSIM index and normalized root mean squared error, which were 5-10% better for the proposed method. In conclusion, a novel, data-driven motion correction technique has been developed that can suppress motion artefacts from motion-corrupted MR images. The proposed technique is a standalone, post-processing method that does not interfere with data acquisition or reconstruction parameters, thus making it suitable for routine clinical practice.
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Affiliation(s)
- Kamlesh Pawar
- Monash Biomedical Imaging, Monash University, Melbourne, Australia
- School of Psychological Sciences, Monash University, Melbourne, Australia
| | - Zhaolin Chen
- Monash Biomedical Imaging, Monash University, Melbourne, Australia
| | - N Jon Shah
- Monash Biomedical Imaging, Monash University, Melbourne, Australia
- Research Centre Jülich, Institute of Medicine, Jülich, Germany
| | - Gary F Egan
- Monash Biomedical Imaging, Monash University, Melbourne, Australia
- School of Psychological Sciences, Monash University, Melbourne, Australia
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Yedavalli V, DiGiacomo P, Tong E, Zeineh M. High-resolution Structural Magnetic Resonance Imaging and Quantitative Susceptibility Mapping. Magn Reson Imaging Clin N Am 2021; 29:13-39. [PMID: 33237013 DOI: 10.1016/j.mric.2020.09.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
High-resolution 7-T imaging and quantitative susceptibility mapping produce greater anatomic detail compared with conventional strengths because of improvements in signal/noise ratio and contrast. The exquisite anatomic details of deep structures, including delineation of microscopic architecture using advanced techniques such as quantitative susceptibility mapping, allows improved detection of abnormal findings thought to be imperceptible on clinical strengths. This article reviews caveats and techniques for translating sequences commonly used on 1.5 or 3 T to high-resolution 7-T imaging. It discusses for several broad disease categories how high-resolution 7-T imaging can advance the understanding of various diseases, improve diagnosis, and guide management.
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Affiliation(s)
- Vivek Yedavalli
- Department of Radiology, Stanford University, 300 Pasteur Drive, Room S047, Stanford, CA 94305-5105, USA; Division of Neuroradiology, Johns Hopkins University, 600 N. Wolfe St. B-112 D, Baltimore, MD 21287, USA
| | - Phillip DiGiacomo
- Department of Bioengineering, Stanford University, Lucas Center for Imaging, Room P271, 1201 Welch Road, Stanford, CA 94305-5488, USA
| | - Elizabeth Tong
- Department of Radiology, 300 Pasteur Drive, Room S031, Stanford, CA 94305-5105, USA
| | - Michael Zeineh
- Department of Radiology, Stanford University, Lucas Center for Imaging, Room P271, 1201 Welch Road, Stanford, CA 94305-5488, USA.
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van Niekerk A, Berglund J, Sprenger T, Norbeck O, Avventi E, Rydén H, Skare S. Control of a wireless sensor using the pulse sequence for prospective motion correction in brain MRI. Magn Reson Med 2021; 87:1046-1061. [PMID: 34453458 DOI: 10.1002/mrm.28994] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/19/2021] [Accepted: 08/12/2021] [Indexed: 11/09/2022]
Abstract
PURPOSE To synchronize and pass information between a wireless motion-tracking device and a pulse sequence and show how this can be used to implement customizable navigator interleaving schemes that are part of the pulse sequence design. METHODS The device tracks motion by sampling the voltages induced in 3 orthogonal pickup coils by the changing gradient fields. These coils were modified to also detect RF-transmit events using a 3D RF-detection circuit. The device could then detect and decode a set RF signatures while ignoring excitations in the parent pulse sequence. A set of unique RF signatures were then paired with a collection of navigators and used to trigger readouts on the wireless device synchronous to the pulse sequence execution. Navigator interleaving schemes were then demonstrated in 3D RF-spoiled gradient echo, T1 -FLAIR (fluid-attenuated inversion recovery) PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction), and T2 -FLAIR PROPELLER pulse sequences. RESULTS Excitations in the parent pulse sequences were successfully rejected and the RF signatures successfully decoded. For the 3D gradient echo sequence, distortions were removed by interleaving flipped polarity navigators and taking the difference between consecutive readouts. The impact on scan duration was reduced by 54% by breaking up the navigators into smaller parts. Successful motion correction was performed using the PROPELLER pulse sequences in 3 Tesla and 1.5 Tesla MRI scanners without modifications to the device hardware or software. CONCLUSION The proposed RF signature-based triggering scheme enables complex interactions between the pulse sequence and a wireless device. Thus, enabling prospective motion correction that is repeatable, versatile, and minimally invasive with respect to hardware setup.
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Affiliation(s)
- Adam van Niekerk
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Johan Berglund
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Tim Sprenger
- MR Applied Science Laboratory Europe, GE Healthcare, Stockholm, Sweden
| | - Ola Norbeck
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Enrico Avventi
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Henric Rydén
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Stefan Skare
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
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10
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Simultaneous feedback control for joint field and motion correction in brain MRI. Neuroimage 2020; 226:117286. [PMID: 32992003 DOI: 10.1016/j.neuroimage.2020.117286] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/21/2020] [Accepted: 08/14/2020] [Indexed: 11/23/2022] Open
Abstract
T2*-weighted gradient-echo sequences count among the most widely used techniques in neuroimaging and offer rich magnitude and phase contrast. The susceptibility effects underlying this contrast scale with B0, making T2*-weighted imaging particularly interesting at high field. High field also benefits baseline sensitivity and thus facilitates high-resolution studies. However, enhanced susceptibility effects and high target resolution come with inherent challenges. Relying on long echo times, T2*-weighted imaging not only benefits from enhanced local susceptibility effects but also suffers from increased field fluctuations due to moving body parts and breathing. High resolution, in turn, renders neuroimaging particularly vulnerable to motion of the head. This work reports the implementation and characterization of a system that aims to jointly address these issues. It is based on the simultaneous operation of two control loops, one for field stabilization and one for motion correction. The key challenge with this approach is that the two loops both operate on the magnetic field in the imaging volume and are thus prone to mutual interference and potential instability. This issue is addressed at the levels of sensing, timing, and control parameters. Performance assessment shows the resulting system to be stable and exhibit adequate loop decoupling, precision, and bandwidth. Simultaneous field and motion control is then demonstrated in examples of T2*-weighted in vivo imaging at 7T.
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11
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Wehkamp N, Rovedo P, Fischer E, Hennig J, Zaitsev M. Frequency-adjustable magnetic field probes. Magn Reson Med 2020; 85:1123-1133. [PMID: 32745321 DOI: 10.1002/mrm.28444] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 06/24/2020] [Accepted: 07/03/2020] [Indexed: 11/11/2022]
Abstract
PURPOSE Nuclear Magnetic Resonance field probes provide exciting possibilities for enhancing MR image quality by allowing for calibration of k-space trajectories and/or dynamic measurement of local field changes. The purpose of this study is to design and build field probes, which are easier to manufacture and more flexible to use than existing probes. METHODS A new manufacturing method is presented based on light-activated resin to encase the coil assembly and the 1H sample. This method allows for realizing field probes with tightly integrated orthogonal coils, whereby the local resonance frequency of protons can be adjusted during the MR experiment, by applying a DC current to the integrated B 0 -field modification coil. RESULTS The apparent field probe position in a gradient echo experiment was shifted within the field of view by changing its Larmor frequency using an integrated micro-coil with 5.5 windings. The measured frequency modulation induced by the B 0 -field modification coil was 113 Hz/mA. The probe was tested with currents up to 100 mA. The DC current in the local field modification coil did not introduce visible artifacts in the MR images. Furthermore selective off-resonant excitation of the new field probes at 2 kHz above the main RF frequency was demonstrated. Gradient impulse response functions measured with a traditional and proposed probe show similar gradient imperfections. CONCLUSIONS The presented approach opens up new possibilities for concurrent field monitoring during MR experiments using standard RF capabilities of clinical scanners.
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Affiliation(s)
- Niklas Wehkamp
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Freiburg, Germany
| | - Philipp Rovedo
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Freiburg, Germany
| | - Elmar Fischer
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Freiburg, Germany
| | - Jürgen Hennig
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Freiburg, Germany
| | - Maxim Zaitsev
- Faculty of Medicine, Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Freiburg, Germany
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12
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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 TRANSACTIONS ON MEDICAL 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] [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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13
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DiGiacomo P, Maclaren J, Aksoy M, Tong E, Carlson M, Lanzman B, Hashmi S, Watkins R, Rosenberg J, Burns B, Skloss TW, Rettmann D, Rutt B, Bammer R, Zeineh M. A within-coil optical prospective motion-correction system for brain imaging at 7T. Magn Reson Med 2020; 84:1661-1671. [PMID: 32077521 DOI: 10.1002/mrm.28211] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 01/18/2020] [Accepted: 01/21/2020] [Indexed: 12/22/2022]
Abstract
PURPOSE Motion artifact limits the clinical translation of high-field MR. We present an optical prospective motion correction system for 7 Tesla MRI using a custom-built, within-coil camera to track an optical marker mounted on a subject. METHODS The camera was constructed to fit between the transmit-receive coils with direct line of sight to a forehead-mounted marker, improving upon prior mouthpiece work at 7 Tesla MRI. We validated the system by acquiring a 3D-IR-FSPGR on a phantom with deliberate motion applied. The same 3D-IR-FSPGR and a 2D gradient echo were then acquired on 7 volunteers, with/without deliberate motion and with/without motion correction. Three neuroradiologists blindly assessed image quality. In 1 subject, an ultrahigh-resolution 2D gradient echo with 4 averages was acquired with motion correction. Four single-average acquisitions were then acquired serially, with the subject allowed to move between acquisitions. A fifth single-average 2D gradient echo was acquired following subject removal and reentry. RESULTS In both the phantom and human subjects, deliberate and involuntary motion were well corrected. Despite marked levels of motion, high-quality images were produced without spurious artifacts. The quantitative ratings confirmed significant improvements in image quality in the absence and presence of deliberate motion across both acquisitions (P < .001). The system enabled ultrahigh-resolution visualization of the hippocampus during a long scan and robust alignment of serially acquired scans with interspersed movement. CONCLUSION We demonstrate the use of a within-coil camera to perform optical prospective motion correction and ultrahigh-resolution imaging at 7 Tesla MRI. The setup does not require a mouthpiece, which could improve accessibility of motion correction during 7 Tesla MRI exams.
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Affiliation(s)
- Phillip DiGiacomo
- Department of Bioengineering, Stanford University, Stanford, California
| | - Julian Maclaren
- Department of Radiology, Stanford University, Stanford, California
| | - Murat Aksoy
- Department of Radiology, Stanford University, Stanford, California
| | - Elizabeth Tong
- Department of Radiology, Stanford University, Stanford, California
| | - Mackenzie Carlson
- Department of Bioengineering, Stanford University, Stanford, California
| | - Bryan Lanzman
- Department of Radiology, Stanford University, Stanford, California
| | - Syed Hashmi
- Department of Radiology, Stanford University, Stanford, California
| | - Ronald Watkins
- Department of Radiology, Stanford University, Stanford, California
| | | | - Brian Burns
- Applied Sciences Lab West, GE Healthcare, Menlo Park, California
| | | | - Dan Rettmann
- MR Applications and Workflow, GE Healthcare, Rochester, Minnesota
| | - Brian Rutt
- Department of Bioengineering, Stanford University, Stanford, California.,Department of Radiology, Stanford University, Stanford, California
| | - Roland Bammer
- Department of Radiology, University of Melbourne, Melbourne, Australia
| | - Michael Zeineh
- Department of Radiology, Stanford University, Stanford, California
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14
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Boer VO, Andersen M, Lind A, Lee NG, Marsman A, Petersen ET. MR spectroscopy using static higher order shimming with dynamic linear terms (HOS-DLT) for improved water suppression, interleaved MRS-fMRI, and navigator-based motion correction at 7T. Magn Reson Med 2020; 84:1101-1112. [PMID: 32060951 PMCID: PMC7317823 DOI: 10.1002/mrm.28202] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 01/08/2020] [Accepted: 01/17/2020] [Indexed: 12/12/2022]
Abstract
PURPOSE To interleave global and local higher order shimming for single voxel MRS. Single voxel MR spectroscopy requires optimization of the B0 field homogeneity in the region of the voxel to obtain a narrow linewidth and provide high data quality. However, the optimization of local higher order fields on a localized MRS voxel typically leads to large field offsets outside that volume. This compromises interleaved MR sequence elements that benefit from global field homogeneity such as water suppression, interleaved MRS-fMRI, and MR motion correction. METHODS A shimming algorithm was developed to optimize the MRS voxel homogeneity and the whole brain homogeneity for interleaved sequence elements, using static higher order shims and dynamic linear terms (HOS-DLT). Shimming performance was evaluated using 6 brain regions and 10 subjects. Furthermore, the benefits of HOS-DLT was demonstrated for water suppression, MRS-fMRI, and motion corrected MRS using fat-navigators. RESULTS The HOS-DLT algorithm was shown to improve the whole brain homogeneity compared to an MRS voxel-based shim, without compromising the MRS voxel homogeneity. Improved water suppression over the brain, reduced image distortions in MRS-fMRI, and improved quality of motion navigators were demonstrated using the HOS-DLT method. CONCLUSION HOS-DLT shimming allowed for both local and global field homogeneity, providing excellent MR spectroscopy data quality, as well as good field homogeneity for interleaved sequence elements, even without the need for dynamic higher order shimming capabilities.
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Affiliation(s)
- Vincent O Boer
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark
| | | | - Anna Lind
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark
| | - Nam Gyun Lee
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark.,Department of Biomedical Engineering, University of Southern California, Los Angeles, California
| | - Anouk Marsman
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark
| | - Esben T Petersen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark.,Center for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
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15
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Jorge J, Gretsch F, Najdenovska E, Tuleasca C, Levivier M, Maeder P, Gallichan D, Marques JP, Bach Cuadra M. Improved susceptibility-weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T. Magn Reson Med 2020; 84:1218-1234. [PMID: 32052486 DOI: 10.1002/mrm.28197] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 01/10/2020] [Accepted: 01/13/2020] [Indexed: 02/06/2023]
Abstract
PURPOSE The thalamus is an important brain structure and neurosurgical target, but its constituting nuclei are challenging to image non-invasively. Recently, susceptibility-weighted imaging (SWI) at ultra-high field has shown promising capabilities for thalamic nuclei mapping. In this work, several methodological improvements were explored to enhance SWI quality and contrast, and specifically its ability for thalamic imaging. METHODS High-resolution SWI was performed at 7T in healthy participants, and the following techniques were applied: (a) monitoring and retrospective correction of head motion and B0 perturbations using integrated MR navigators, (b) segmentation and removal of venous vessels on the SWI data using vessel enhancement filtering, and (c) contrast enhancement by tuning the parameters of the SWI phase-magnitude combination. The resulting improvements were evaluated with quantitative metrics of image quality, and by comparison to anatomo-histological thalamic atlases. RESULTS Even with sub-millimeter motion and natural breathing, motion and field correction produced clear improvements in both magnitude and phase data quality (76% and 41%, respectively). The improvements were stronger in cases of larger motion/field deviations, mitigating the dependence of image quality on subject performance. Optimizing the SWI phase-magnitude combination yielded substantial improvements in image contrast, particularly in the thalamus, well beyond previously reported SWI results. The atlas comparisons provided compelling evidence of anatomical correspondence between SWI features and several thalamic nuclei, for example, the ventral intermediate nucleus. Vein detection performed favorably inside the thalamus, and vein removal further improved visualization. CONCLUSION Altogether, the proposed developments substantially improve high-resolution SWI, particularly for thalamic nuclei imaging.
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Affiliation(s)
- João Jorge
- Medical Image Analysis Laboratory, Center for Biomedical Imaging (CIBM), University of Lausanne, Lausanne, Switzerland.,Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Frédéric Gretsch
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Elena Najdenovska
- Medical Image Analysis Laboratory, Center for Biomedical Imaging (CIBM), University of Lausanne, Lausanne, Switzerland.,Department of Radiology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Constantin Tuleasca
- Department of Clinical Neurosciences, Neurosurgery Service and Gamma Knife Center, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.,Signal Processing Laboratory (LTS5), École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Faculty of Biology and Medicine (FBM), University of Lausanne (UNIL), Lausanne, Switzerland
| | - Marc Levivier
- Department of Clinical Neurosciences, Neurosurgery Service and Gamma Knife Center, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.,Faculty of Biology and Medicine (FBM), University of Lausanne (UNIL), Lausanne, Switzerland
| | - Philippe Maeder
- Department of Radiology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Daniel Gallichan
- Cardiff University Brain Research Imaging Centre, School of Engineering, Cardiff University, Cardiff, UK
| | - José P Marques
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
| | - Meritxell Bach Cuadra
- Medical Image Analysis Laboratory, Center for Biomedical Imaging (CIBM), University of Lausanne, Lausanne, Switzerland.,Department of Radiology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland.,Signal Processing Laboratory (LTS5), École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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16
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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] [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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17
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van Niekerk A, Meintjes E, van der Kouwe A. A Wireless Radio Frequency Triggered Acquisition Device (WRAD) for Self-Synchronised Measurements of the Rate of Change of the MRI Gradient Vector Field for Motion Tracking. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:1610-1621. [PMID: 30629498 PMCID: PMC7192240 DOI: 10.1109/tmi.2019.2891774] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this paper, we present a device that is capable of wireless synchronization to the MRI pulse sequence time frame with sub-microsecond precision. This is achieved by detecting radio frequency pulses in the parent pulse sequence using a small resonant circuit. The device incorporates a 3-axis pickup coil, constructed using conventional printed circuit board (PCB) manufacturing techniques, to measure the rate of change of the gradient waveforms with respect to time. Using Maxwell's equations, assuming negligible rates of change of curl and divergence, a model of the expected gradient derivative (slew) vector field is presented. A 3-axis Hall effect magnetometer allows for the measurement of the direction of the static magnetic field in the device co-ordinate frame. By combining the magnetometer measurement with the pickup coil voltages and slew vector field model, the orientation and position can be determined to within a precision of 0.1 degrees and 0.1 mm, respectively, using a pulse series lasting 880 μs . The gradient pulses are designed to be sinusoidal, enabling the detection of a phase shift between the time frame of the pickup coil digitization circuit and the gradient amplifiers. The signal processing is performed by a low power micro-controller on the device and the results are transmitted out of the scanner bore using a low latency 2.4 GHz radio link. The device identified an unexpected 40 kHz oscillation relating to the pulse width modulation frequency of the gradient amplifiers that is predominantly in the direction of the static magnetic field. The proposed wireless radio frequency triggered acquisition device enables users to probe the scanner gradient slew vector field with minimal hardware set-up and shows promise for the future developments in the prospective motion correction.
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18
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Andersen M, Björkman-Burtscher IM, Marsman A, Petersen ET, Boer VO. Improvement in diagnostic quality of structural and angiographic MRI of the brain using motion correction with interleaved, volumetric navigators. PLoS One 2019; 14:e0217145. [PMID: 31100092 PMCID: PMC6524807 DOI: 10.1371/journal.pone.0217145] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 05/06/2019] [Indexed: 12/30/2022] Open
Abstract
INTRODUCTION Subject movements lead to severe artifacts in magnetic resonance (MR) brain imaging. In this study we evaluate the diagnostic image quality in T1-weighted, T2-weighted, and time-of-flight angiographic MR sequences when using a flexible, navigator-based prospective motion correction system (iMOCO). METHODS Five healthy volunteers were scanned during different movement scenarios with and without (+/-) iMOCO activated. An experienced neuroradiologist graded images for image quality criteria (grey-white-matter discrimination, basal ganglia, and small structure and vessel delineation), and general image quality on a four-grade scale. RESULTS In scans with deliberate motion, there was a significant improvement in the image quality with iMOCO compared to the scans without iMOCO in both general image impression (T1 p<0.01, T2 p<0.01, TOF p = 0.03) and in anatomical grading (T1 p<0.01, T2 p<0.01, TOF p = 0.01). Subjective image quality was considered non-diagnostic in 91% of the scans with motion -iMOCO, but only in 4% of the scans with motion +iMOCO. iMOCO performed best in the T1-weighted sequence and least well in the angiography sequence. iMOCO was not shown to have any negative effect on diagnostic image quality, as no significant difference in diagnostic quality was seen between scans -iMOCO and +iMOCO with no deliberate movement. CONCLUSION The evaluation showed that iMOCO enables substantial improvements in image quality in scans affected by subject movement, recovering important diagnostic information in an otherwise unusable scan.
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Affiliation(s)
- Mads Andersen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
- Philips Healthcare, Copenhagen, Denmark
- * E-mail:
| | - Isabella M. Björkman-Burtscher
- Department of Radiology, Clinical Sciences Lund, Lund University, Lund, Sweden
- Department of Medical Imaging and Physiology, Skåne University Hospital, Lund, Sweden
- Lund University Bioimaging Centre (LBIC), Lund University, Lund, Sweden
| | - Anouk Marsman
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Esben Thade Petersen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
- Centre for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Vincent Oltman Boer
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
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19
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van Niekerk A, van der Kouwe A, Meintjes E. Toward "plug and play" prospective motion correction for MRI by combining observations of the time varying gradient and static vector fields. Magn Reson Med 2019; 82:1214-1228. [PMID: 31066109 DOI: 10.1002/mrm.27790] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 03/22/2019] [Accepted: 04/08/2019] [Indexed: 11/05/2022]
Abstract
PURPOSE The efficacy of a Wireless Radio frequency triggered Acquisition Device (WRAD) is evaluated for high frequency (50 Hz) prospective motion correction in a 3-dimensional spoiled gradient echo pulse sequence. METHODS The device measures the rate of change in the gradient vector fields (slew) using a 3-dimensional assembly of Printed Circuit Board (PCB) inductors and the direction of the static magnetic field using a 3-axis Hall effect magnetometer. The slew vector encoding is highly efficient, because the Maxwell-term position encoding is observable, allowing overconstrained pose measurement using 3 sinusoidal gradient pulses lasting 880 μs. Since small offsets in the magnetometer can introduce bias into the pose estimates, sensor/system biases are tracked using a lightweight Kalman filter. The only calibration required is determining a geometric scaling factor for the pickup coils, which is specific to the device and will therefore be valid in any scanner. RESULTS The device was used to perform prospective motion correction in 3 subjects, resulting in an increase in Average Edge Strength (AES) for involuntary and deliberate motion. CONCLUSIONS The WRAD is simple to set up and use, with well-defined measurement variance. This could enable "plug and play" prospective motion correction if pulse sequence independence is achieved.
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Affiliation(s)
- Adam van Niekerk
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Faculty of Health Sciences, Department of Human Biology, University of Cape Town, Cape Town, South Africa
| | - Andre van der Kouwe
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Faculty of Health Sciences, Department of Human Biology, University of Cape Town, Cape Town, South Africa.,Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, Massachusetts.,Radiology, Harvard Medical School, Boston, Massachusetts
| | - Ernesta Meintjes
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Faculty of Health Sciences, Department of Human Biology, University of Cape Town, Cape Town, South Africa.,Cape Universities Body Imaging Centre (CUBIC) at UCT, Cape Town, South Africa
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20
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Slipsager JM, Ellegaard AH, Glimberg SL, Paulsen RR, Tisdall MD, Wighton P, van der Kouwe A, Marner L, Henriksen OM, Law I, Olesen OV. Markerless motion tracking and correction for PET, MRI, and simultaneous PET/MRI. PLoS One 2019; 14:e0215524. [PMID: 31002725 PMCID: PMC6474595 DOI: 10.1371/journal.pone.0215524] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 04/03/2019] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE We demonstrate and evaluate the first markerless motion tracker compatible with PET, MRI, and simultaneous PET/MRI systems for motion correction (MC) of brain imaging. METHODS PET and MRI compatibility is achieved by careful positioning of in-bore vision extenders and by placing all electronic components out-of-bore. The motion tracker is demonstrated in a clinical setup during a pediatric PET/MRI study including 94 pediatric patient scans. PET MC is presented for two of these scans using a customized version of the Multiple Acquisition Frame method. Prospective MC of MRI acquisition of two healthy subjects is demonstrated using a motion-aware MRI sequence. Real-time motion estimates are accompanied with a tracking validity parameter to improve tracking reliability. RESULTS For both modalities, MC shows that motion induced artifacts are noticeably reduced and that motion estimates are sufficiently accurate to capture motion ranging from small respiratory motion to large intentional motion. In the PET/MRI study, a time-activity curve analysis shows image improvements for a patient performing head movements corresponding to a tumor motion of ±5-10 mm with a 19% maximal difference in standardized uptake value before and after MC. CONCLUSION The first markerless motion tracker is successfully demonstrated for prospective MC in MRI and MC in PET with good tracking validity. SIGNIFICANCE As simultaneous PET/MRI systems have become available for clinical use, an increasing demand for accurate motion tracking and MC in PET/MRI scans has emerged. The presented markerless motion tracker facilitate this demand.
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Affiliation(s)
- Jakob M. Slipsager
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, Lyngby, Denmark
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- TracInnovations, Ballerup, Denmark
| | - Andreas H. Ellegaard
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, Lyngby, Denmark
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - Rasmus R. Paulsen
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, Lyngby, Denmark
| | - M. Dylan Tisdall
- Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Paul Wighton
- Athinoula. A. Matinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - André van der Kouwe
- Athinoula. A. Matinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Lisbeth Marner
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Otto M. Henriksen
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Ian Law
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Oline V. Olesen
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, Lyngby, Denmark
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- TracInnovations, Ballerup, Denmark
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21
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Eschelbach M, Aghaeifar A, Bause J, Handwerker J, Anders J, Engel EM, Thielscher A, Scheffler K. Comparison of prospective head motion correction with NMR field probes and an optical tracking system. Magn Reson Med 2018; 81:719-729. [PMID: 30058220 DOI: 10.1002/mrm.27343] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 03/21/2018] [Accepted: 04/12/2018] [Indexed: 11/08/2022]
Abstract
PURPOSE The aim of this study was to compare prospective head motion correction and motion tracking abilities of two tracking systems: Active NMR field probes and a Moiré phase tracking camera system using an optical marker. METHODS Both tracking systems were used simultaneously on human subjects. The prospective head motion correction was compared in an MP2RAGE and a gradient echo sequence. In addition, the motion tracking trajectories for three subjects were compared against each other and their correlation and deviations were analyzed. RESULTS With both tracking systems motion artifacts were visibly reduced. The precision of the field probe system was on the order of 50 µm for translations and 0.03° for rotations while the camera's was approximately 5 µm and 0.007°. The comparison of the measured trajectories showed close correlation and an average absolute deviation below 500 µm and 0.5°. CONCLUSION This study presents the first in vivo comparison between NMR field probes and Moiré phase tracking. For the gradient echo images, the field probes had a similar motion correction performance as the optical tracking system. For the MP2RAGE measurement, however, the camera yielded better results. Still, both tracking systems substantially decreased image artifacts in the presence of subject motion. Thus, the motion tracking modality should be chosen according to the specific requirements of the experiment while considering the desired image resolution, refresh rate, and head coil constraints.
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Affiliation(s)
| | - Ali Aghaeifar
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Jonas Bause
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Jonas Handwerker
- Institute of Microelectronics, University of Ulm, Ulm, Germany.,Institute of Smart Sensors, University of Stuttgart, Stuttgart, Germany
| | - Jens Anders
- Institute of Microelectronics, University of Ulm, Ulm, Germany.,Institute of Smart Sensors, University of Stuttgart, Stuttgart, Germany
| | - Eva-Maria Engel
- Department of Prosthodontics, Center of Dentistry, Oral Medicine, and Maxillofacial Surgery, University Hospital Tuebingen, Germany
| | - Axel Thielscher
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,Department of Electrical Engineering, Technical University of Denmark, Lyngby, Denmark.,DRCMR, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Klaus Scheffler
- Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,Department for Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany
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22
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Liu J, de Zwart JA, van Gelderen P, Murphy-Boesch J, Duyn JH. Effect of head motion on MRI B 0 field distribution. Magn Reson Med 2018; 80:2538-2548. [PMID: 29770481 PMCID: PMC6239980 DOI: 10.1002/mrm.27339] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/05/2018] [Accepted: 04/05/2018] [Indexed: 01/07/2023]
Abstract
PURPOSE To identify and characterize the sources of B0 field changes due to head motion, to reduce motion sensitivity in human brain MRI. METHODS B0 fields were measured in 5 healthy human volunteers at various head poses. After measurement of the total field, the field originating from the subject was calculated by subtracting the external field generated by the magnet and shims. A subject-specific susceptibility model was created to quantify the contribution of the head and torso. The spatial complexity of the field changes was analyzed using spherical harmonic expansion. RESULTS Minor head pose changes can cause substantial and spatially complex field changes in the brain. For rotations and translations of approximately 5 º and 5 mm, respectively, at 7 T, the field change that is associated with the subject's magnetization generates a standard deviation (SD) of about 10 Hz over the brain. The stationary torso contributes to this subject-associated field change significantly with a SD of about 5 Hz. The subject-associated change leads to image-corrupting phase errors in multi-shot <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> -weighted acquisitions. CONCLUSION The B0 field changes arising from head motion are problematic for multishot <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> -weighted imaging. Characterization of the underlying sources provides new insights into mitigation strategies, which may benefit from individualized predictive field models in addition to real-time field monitoring and correction strategies.
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Affiliation(s)
- Jiaen Liu
- Advanced MRI, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Jacco A de Zwart
- Advanced MRI, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Peter van Gelderen
- Advanced MRI, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Joseph Murphy-Boesch
- Advanced MRI, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Jeff H Duyn
- Advanced MRI, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
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23
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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] [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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24
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Topfer R, Foias A, Stikov N, Cohen-Adad J. Real-time correction of respiration-induced distortions in the human spinal cord using a 24-channel shim array. Magn Reson Med 2018; 80:935-946. [DOI: 10.1002/mrm.27089] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 12/22/2017] [Accepted: 12/24/2017] [Indexed: 12/25/2022]
Affiliation(s)
- Ryan Topfer
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
| | - Alexandru Foias
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
| | - Nikola Stikov
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
- Montreal Heart Institute, Université de Montréal; Montreal Quebec Canada
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
- Functional Neuroimaging Unit, CRIUGM, Université de Montréal; Montreal Quebec Canada
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25
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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] [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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26
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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] [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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27
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Özbay PS, Duerst Y, Wilm BJ, Pruessmann KP, Nanz D. Enhanced quantitative susceptibility mapping (QSM) using real-time field control. Magn Reson Med 2017; 79:770-778. [DOI: 10.1002/mrm.26735] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 03/31/2017] [Accepted: 04/02/2017] [Indexed: 12/15/2022]
Affiliation(s)
- Pinar Senay Özbay
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology; Zurich Switzerland
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Yolanda Duerst
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Bertram Jakob Wilm
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Klaas Paul Pruessmann
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Daniel Nanz
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology; Zurich Switzerland
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28
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van Niekerk A, van der Kouwe A, Meintjes E. A Method for Measuring Orientation Within a Magnetic Resonance Imaging Scanner Using Gravity and the Static Magnetic Field (VectOrient). IEEE TRANSACTIONS ON MEDICAL IMAGING 2017; 36:1129-1139. [PMID: 28129151 PMCID: PMC5637283 DOI: 10.1109/tmi.2017.2652502] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In MRI brain imaging, subject motion limits obtainable image clarity. Due to the hardware layout of an MRI scanner, gradient excitations can be used to rapidly detect position. Orientation, however, is more difficult to detect and is commonly calculated by comparing the position measurements of multiple spatially constrained points to a reference dataset. The result is increased size of the apparatus the subject must wear, which can influence the imaging workflow. In optical based methods marker attachment sites are limited due to the line of sight requirement between the camera and marker, and an external reference frame is introduced. To address these challenges a method called VectOrient is proposed for orientation measurement that is based on vector observations of gravity and the MRI scanner's static magnetic field. A prototype device comprising of an accelerometer, magnetometer and angular rate sensor shows good MRI compatibility. Phantom scans of a pineapple with zero scanner specific calibration achieve comparable results to a rigid body registration algorithm with deviations less than 0.8 degrees over 28 degree changes in orientation. Dynamic performance shows potential for prospective motion correction as rapid changes in orientation (peak 20 degrees per second) can be corrected. The pulse sequence implemented achieves orientation updates with a latency estimated to be less than 12.7 ms, of which only a small fraction (<1 ms) is used for computing orientation from the raw sensor signals. The device is capable of quantifying subject respiration and heart rates. The proposed approach for orientation estimation could help address some limitations of existing methods such as orientation measurement range, temporal resolution, ease of use and marker placement.
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29
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Jorge J, Gretsch F, Gallichan D, Marques JP. Tracking discrete off-resonance markers with three spokes (trackDOTS) for compensation of head motion and B0
perturbations: Accuracy and performance in anatomical imaging. Magn Reson Med 2017; 79:160-171. [DOI: 10.1002/mrm.26654] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 02/03/2017] [Accepted: 02/03/2017] [Indexed: 01/29/2023]
Affiliation(s)
- João Jorge
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne; Lausanne Switzerland
| | - Frédéric Gretsch
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne; Lausanne Switzerland
| | - Daniel Gallichan
- Biomedical Imaging Research Center, École Polytechnique Fédérale de Lausanne; Lausanne Switzerland
| | - José P. Marques
- Donders Institute; Radboud University; Nijmegen the Netherlands
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30
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Gross S, Vionnet L, Kasper L, Dietrich BE, Pruessmann KP. Physiology recording with magnetic field probes for fMRI denoising. Neuroimage 2017; 154:106-114. [PMID: 28088483 DOI: 10.1016/j.neuroimage.2017.01.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 12/28/2016] [Accepted: 01/10/2017] [Indexed: 10/20/2022] Open
Abstract
Physiological noise originating in cardiovascular and respiratory processes is a substantial confound in BOLD fMRI. When unaccounted for it reduces the temporal SNR and causes error in inferred brain activity and connectivity. Physiology correction typically relies on auxiliary measurements with peripheral devices such as ECG, pulse oximeters, and breathing belts. These require direct skin contact or at least a tight fit, impairing subject comfort and adding to the setup time. In this work, we explore a touch-free alternative for physiology recording, using magnetic detection with NMR field probes. Placed close to the chest such probes offer high sensitivity to cardiovascular and respiratory dynamics without mechanical contact. This is demonstrated by physiology regression in a typical fMRI scenario at 7T, including validation against standard devices. The study confirms essentially equivalent performance of noise models based on conventional recordings and on field probes. It is shown that the field probes may be positioned in the subject's back such that they could be readily integrated in the patient table.
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Affiliation(s)
- Simon Gross
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Laetitia Vionnet
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Lars Kasper
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland; Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, 8032 Zurich, Switzerland.
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
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31
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Kettinger Á, Hill C, Vidnyánszky Z, Windischberger C, Nagy Z. Investigating the Group-Level Impact of Advanced Dual-Echo fMRI Combinations. Front Neurosci 2016; 10:571. [PMID: 28018165 PMCID: PMC5149566 DOI: 10.3389/fnins.2016.00571] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 11/28/2016] [Indexed: 11/16/2022] Open
Abstract
Multi-echo fMRI data acquisition has been widely investigated and suggested to optimize sensitivity for detecting the BOLD signal. Several methods have also been proposed for the combination of data with different echo times. The aim of the present study was to investigate whether these advanced echo combination methods provide advantages over the simple averaging of echoes when state-of-the-art group-level random-effect analyses are performed. Both resting-state and task-based dual-echo fMRI data were collected from 27 healthy adult individuals (14 male, mean age = 25.75 years) using standard echo-planar acquisition methods at 3T. Both resting-state and task-based data were subjected to a standard image pre-processing pipeline. Subsequently the two echoes were combined as a weighted average, using four different strategies for calculating the weights: (1) simple arithmetic averaging, (2) BOLD sensitivity weighting, (3) temporal-signal-to-noise ratio weighting and (4) temporal BOLD sensitivity weighting. Our results clearly show that the simple averaging of data with the different echoes is sufficient. Advanced echo combination methods may provide advantages on a single-subject level but when considering random-effects group level statistics they provide no benefit regarding sensitivity (i.e., group-level t-values) compared to the simple echo-averaging approach. One possible reason for the lack of clear advantages may be that apart from increasing the average BOLD sensitivity at the single-subject level, the advanced weighted averaging methods also inflate the inter-subject variance. As the echo combination methods provide very similar results, the recommendation is to choose between them depending on the availability of time for collecting additional resting-state data or whether subject-level or group-level analyses are planned.
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Affiliation(s)
- Ádám Kettinger
- Department of Nuclear Techniques, Budapest University of Technology and EconomicsBudapest, Hungary; Brain Imaging Centre, Research Centre for Natural Sciences, Hungarian Academy of SciencesBudapest, Hungary
| | - Christopher Hill
- Laboratory for Social and Neural Systems Research, University of Zurich Zurich, Switzerland
| | - Zoltán Vidnyánszky
- Brain Imaging Centre, Research Centre for Natural Sciences, Hungarian Academy of Sciences Budapest, Hungary
| | - Christian Windischberger
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna Vienna, Austria
| | - Zoltán Nagy
- Laboratory for Social and Neural Systems Research, University of Zurich Zurich, Switzerland
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32
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Fehlner A, Hirsch S, Weygandt M, Christophel T, Barnhill E, Kadobianskyi M, Braun J, Bernarding J, Lützkendorf R, Sack I, Hetzer S. Increasing the spatial resolution and sensitivity of magnetic resonance elastography by correcting for subject motion and susceptibility-induced image distortions. J Magn Reson Imaging 2016; 46:134-141. [DOI: 10.1002/jmri.25516] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 10/05/2016] [Indexed: 12/13/2022] Open
Affiliation(s)
- Andreas Fehlner
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Sebastian Hirsch
- Institute of Medical Informatics; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Martin Weygandt
- Berlin Center for Advanced Neuroimaging; Charité - Universitätsmedizin Berlin; Berlin Germany
- Bernstein Center for Computational Neuroscience; Berlin Germany
| | - Thomas Christophel
- Berlin Center for Advanced Neuroimaging; Charité - Universitätsmedizin Berlin; Berlin Germany
- Bernstein Center for Computational Neuroscience; Berlin Germany
| | - Eric Barnhill
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Mykola Kadobianskyi
- Berlin Center for Advanced Neuroimaging; Charité - Universitätsmedizin Berlin; Berlin Germany
- Bernstein Center for Computational Neuroscience; Berlin Germany
| | - Jürgen Braun
- Institute of Medical Informatics; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Johannes Bernarding
- Institute of Biometry and Medical Informatics; Otto-von-Guericke University; Magdeburg Germany
| | - Ralf Lützkendorf
- Institute of Biometry and Medical Informatics; Otto-von-Guericke University; Magdeburg Germany
| | - Ingolf Sack
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Stefan Hetzer
- Berlin Center for Advanced Neuroimaging; Charité - Universitätsmedizin Berlin; Berlin Germany
- Bernstein Center for Computational Neuroscience; Berlin Germany
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33
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Dietrich BE, Brunner DO, Wilm BJ, Barmet C, Pruessmann KP. Continuous Magnetic Field Monitoring Using Rapid Re-Excitation of NMR Probe Sets. IEEE TRANSACTIONS ON MEDICAL IMAGING 2016; 35:1452-1462. [PMID: 26742126 DOI: 10.1109/tmi.2016.2514608] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
MRI relies on static and spatially varying dynamic magnetic fields of high accuracy. NMR field probes permit the direct observation of spatiotemporal field dynamics for diverse purposes such as data correction, field control, sequence validation, and hardware characterization. However, due to probe signal decay and dephasing existing field cameras are limited in terms of readout duration and the extent of k -space that can be covered. The present work aims to overcome these limitations by the transition to short-lived NMR probes and rapid re-excitation. The proposed approach uses probes with T 2 so short that thermal relaxation dominates signal decay even in the presence of strongest gradients. They are integrated with transmit, receive and sequencing electronics that permit high-rate re-excitation with optional probe alternation as well as complementary RF pulse recording. The system is demonstrated by monitoring of sample MRI sequences with long readouts and large gradient moments. It is compared with the conventional long-lived probe concept and characterized in terms of net sensitivity and sources of systematic error. Continuous k -space trajectory mapping is demonstrated and validated by trajectory-based image reconstruction.
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34
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Hock A, Henning A. Motion correction and frequency stabilization for MRS of the human spinal cord. NMR IN BIOMEDICINE 2016; 29:490-498. [PMID: 26867133 DOI: 10.1002/nbm.3487] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/15/2015] [Accepted: 12/20/2015] [Indexed: 06/05/2023]
Abstract
Subject motion is challenging for MRS, because it can falsify results. For spinal cord MRS in particular, subject movement is critical, since even a small movement > 1 mm) can lead to a voxel shift out of the desired measurement region. Therefore, the identification of motion corrupted MRS scans is essential. In this investigation, MR navigators acquired simultaneously with the MRS data are used to identify a displacement of the spinal cord due to subject motion. It is shown that navigators are able to recognize substantial subject motion (>1 mm) without impairing the MRS measurement. In addition, navigators are easy to apply to the measurement, because no additional hardware and just a minor additional user effort are needed. Moreover, no additional scan time is required, because navigators can be applied in the deadtime of the MRS sequence. Furthermore, in this work, retrospective motion correction combined with frequency stabilization is presented by combining navigators with non-water-suppressed (1)H-MRS, resulting in an improved spectral quality of the spinal cord measurements.
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Affiliation(s)
- Andreas Hock
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
- Department of Psychiatry, Psychotherapy and Psychosomatics, Hospital of Psychiatry, University of Zurich, Zurich, Switzerland
| | - Anke Henning
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
- Max Plank Institute for Biological Cybernetics, Tuebingen, Germany
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35
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Dietrich BE, Brunner DO, Wilm BJ, Barmet C, Gross S, Kasper L, Haeberlin M, Schmid T, Vannesjo SJ, Pruessmann KP. A field camera for MR sequence monitoring and system analysis. Magn Reson Med 2015; 75:1831-40. [DOI: 10.1002/mrm.25770] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/18/2015] [Accepted: 04/20/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Benjamin E. Dietrich
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
| | - David O. Brunner
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
- Skope Magnetic Resonance Technologies; Zurich Switzerland
| | - Bertram J. Wilm
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
- Skope Magnetic Resonance Technologies; Zurich Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
- Skope Magnetic Resonance Technologies; Zurich Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
| | - Lars Kasper
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
- Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
| | - Maximilian Haeberlin
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Zurich Switzerland
| | - S. Johanna Vannesjo
- 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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36
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Zahneisen B, Ernst T. Homogeneous coordinates in motion correction. Magn Reson Med 2015; 75:274-9. [PMID: 25648318 DOI: 10.1002/mrm.25552] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 10/01/2014] [Accepted: 11/07/2014] [Indexed: 11/09/2022]
Abstract
PURPOSE Prospective motion correction for MRI and other imaging modalities are commonly based on the assumption of affine motion, i.e., rotations, shearing, scaling and translations. In addition it often involves transformations between different reference frames, especially for applications with an external tracking device. The goal of this work is to develop a computational framework for motion correction based on homogeneous transforms. THEORY AND METHODS The homogeneous representation of affine transformations uses 4 × 4 transformation matrices applied to four-dimensional augmented vectors. It is demonstrated how homogenous transforms can be used to describe the motion of slice objects during an MRI scan. Furthermore, we extend the concept of homogeneous transforms to gradient and k-space vectors, and show that the fourth dimension of an augmented k-space vector encodes the complex phase of the corresponding signal sample due to translations. RESULTS The validity of describing motion tracking in real space and k-space using homogeneous transformations only is demonstrated on phantom experiments. CONCLUSION Homogeneous transformations allows for a conceptually simple, consistent and computationally efficient theoretical framework for motion correction applications.
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Affiliation(s)
- Benjamin Zahneisen
- University of Hawaii, Department of Medicine, John A. Burns School of Medicine, Honolulu, Hawaii, USA
| | - Thomas Ernst
- University of Hawaii, Department of Medicine, John A. Burns School of Medicine, Honolulu, Hawaii, USA
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