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Lin Z, Jiang D, Hong Y, Zhang Y, Hsu YC, Lu H, Wu D. Vessel-specific quantification of cerebral venous oxygenation with velocity-encoding preparation and rapid acquisition. Magn Reson Med 2024; 92:782-791. [PMID: 38523598 DOI: 10.1002/mrm.30092] [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: 01/29/2024] [Revised: 03/03/2024] [Accepted: 03/07/2024] [Indexed: 03/26/2024]
Abstract
PURPOSE Non-invasive measurement of cerebral venous oxygenation (Yv) is of critical importance in brain diseases. The present work proposed a fast method to quantify regional Yv map for both large and small veins. METHODS A new sequence was developed, referred to as TRU-VERA (T2 relaxation under velocity encoding and rapid acquisition, which isolates blood spins from static tissue with velocity-encoding preparation, modulates the T2 weighting of venous signal with T2-preparation and utilizes a bSSFP readout to achieve fast acquisition with high resolution. The sequence was first optimized to achieve best sensitivity for both large and small veins, and then validated with TRUST (T2 relaxation under spin tagging), TRUPC (T2 relaxation under phase contrast), and accelerated TRUPC MRI. Regional difference of Yv was evaluated, and test-retest reproducibility was examined. RESULTS Optimal Venc was determined to be 3 cm/s, while recovery time and balanced SSFP flip angle within reasonable range had minimal effect on SNR efficiency. Venous T2 measured with TRU-VERA was highly correlated with T2 from TRUST (R2 = 0.90), and a conversion equation was established for further calibration to Yv. TRU-VERA sequences showed consistent Yv estimation with TRUPC (R2 = 0.64) and accelerated TRUPC (R2 = 0.79). Coefficient of variation was 0.84% for large veins and 2.49% for small veins, suggesting an excellent test-retest reproducibility. CONCLUSION The proposed TRU-VERA sequence is a promising method for vessel-specific oxygenation assessment.
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Affiliation(s)
- Zixuan Lin
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Dengrong Jiang
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Yiwen Hong
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Yi-Cheng Hsu
- MR Collaboration, Siemens Healthineers Ltd, Shanghai, China
| | - Hanzhang Lu
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Dan Wu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
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Plähn NMJ, Poli S, Peper ES, Açikgöz BC, Kreis R, Ganter C, Bastiaansen JAM. Getting the phase consistent: The importance of phase description in balanced steady-state free precession MRI of multi-compartment systems. Magn Reson Med 2024; 92:215-225. [PMID: 38321594 DOI: 10.1002/mrm.30033] [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: 10/16/2023] [Revised: 01/09/2024] [Accepted: 01/12/2024] [Indexed: 02/08/2024]
Abstract
PURPOSE Determine the correct mathematical phase description for balanced steady-state free precession (bSSFP) signals in multi-compartment systems. THEORY AND METHODS Based on published bSSFP signal models, different phase descriptions can be formulated: one predicting the presence and the other predicting the absence of destructive interference effects in multi-compartment systems. Numerical simulations of bSSFP signals of water and acetone were performed to evaluate the predictions of these different phase descriptions. For experimental validation, bSSFP profiles were measured at 3T using phase-cycled bSSFP acquisitions performed in a phantom containing mixtures of water and acetone, which replicates a system with two signal components. Localized single voxel MRS was performed at 7T to determine the relative chemical shift of the acetone-water mixtures. RESULTS Based on the choice of phase description, the simulated bSSFP profiles of water-acetone mixtures varied significantly, either displaying or lacking destructive interference effects, as predicted theoretically. In phantom experiments, destructive interference was consistently observed in the measured bSSFP profiles of water-acetone mixtures, supporting the theoretical description that predicts such interference effects. The connection between the choice of phase description and predicted observation enables unambiguous experimental identification of the correct phase description for multi-compartment bSSFP profiles, which is consistent with the Bloch equations. CONCLUSION The study emphasizes that consistent phase descriptions are crucial for accurately describing multi-compartment bSSFP signals, as incorrect phase descriptions result in erroneous predictions.
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Affiliation(s)
- Nils M J Plähn
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translation Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Simone Poli
- Translation Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
- MR Methodology, Department for Diagnostic and Interventional Neuroradiology, University of Bern, Bern, Switzerland
| | - Eva S Peper
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translation Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
| | - Berk C Açikgöz
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translation Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Roland Kreis
- Translation Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
- MR Methodology, Department for Diagnostic and Interventional Neuroradiology, University of Bern, Bern, Switzerland
- Department for Biomedical Research, University of Bern, Bern, Switzerland
| | - Carl Ganter
- Department of Diagnostic and Interventional Radiology, TUM School of Medicine and Health, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Jessica A M Bastiaansen
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Translation Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland
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3
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Uzun D, Yildirim DK, Bruce CG, Halaby RN, Jaimes A, Potersnak A, Ramasawmy R, Campbell-Washburn A, Lederman RJ, Kocaturk O. Interventional device tracking under MRI via alternating current controlled inhomogeneities. Magn Reson Med 2024; 92:346-360. [PMID: 38394163 PMCID: PMC11055668 DOI: 10.1002/mrm.30031] [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: 07/18/2023] [Revised: 01/10/2024] [Accepted: 01/12/2024] [Indexed: 02/25/2024]
Abstract
PURPOSE To introduce alternating current-controlled, conductive ink-printed marker that could be implemented with both custom and commercial interventional devices for device tracking under MRI using gradient echo, balanced SSFP, and turbo spin-echo sequences. METHODS Tracking markers were designed as solenoid coils and printed on heat shrink tubes using conductive ink. These markers were then placed on three MR-compatible test samples that are typically challenging to visualize during MRI scans. MRI visibility of markers was tested by applying alternating and direct current to the markers, and the effects of applied current parameters (amplitude, frequency) on marker artifacts were tested for three sequences (gradient echo, turbo spin echo, and balanced SSFP) in a gel phantom, using 0.55T and 1.5T MRI scanners. Furthermore, an MR-compatible current supply circuit was designed, and the performance of the current-controlled markers was tested in one postmortem animal experiment using the current supply circuit. RESULTS Direction and parameters of the applied current were determined to provide the highest conspicuity for all three sequences. Marker artifact size was controlled by adjusting the current amplitude, successfully. Visibility of a custom-designed, 20-gauge nitinol needle was increased in both in vitro and postmortem animal experiments using the current supply circuit. CONCLUSION Current-controlled conductive ink-printed markers can be placed on custom or commercial MR-compatible interventional tools and can provide an easy and effective solution to device tracking under MRI for three sequences by adjusting the applied current parameters with respect to pulse sequence parameters using the current supply circuit.
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Affiliation(s)
- Dogangun Uzun
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
- Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey
| | - Dursun Korel Yildirim
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Christopher G. Bruce
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Rim N. Halaby
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Andi Jaimes
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Amanda Potersnak
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Rajiv Ramasawmy
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Adrienne Campbell-Washburn
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Robert J. Lederman
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, MD, USA
| | - Ozgur Kocaturk
- Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey
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4
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Coronado R, Castillo-Passi C, Besa C, Irarrazaval P. Fast and accessible T2 mapping using off-resonance corrected DESPOT2 with application to 3D prostate. Magn Reson Imaging 2024; 109:227-237. [PMID: 38508291 DOI: 10.1016/j.mri.2024.03.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 03/22/2024]
Abstract
PURPOSE Most T1 and T2 mapping take long acquisitions or needs specialized sequences not widely accessible on clinical scanners. An available solution is DESPOT1/T2 (Driven equilibrium single pulse observation of T1/T2). DESPOT1/T2 uses Spoiled gradient-echo (SPGR) and balanced Steady-State Free Precession (bSSFP) sequences, offering an accessible and reliable way for 3D accelerated T1/T2 mapping. However, bSSFP is prone to off-resonance artifacts, limiting the application of DESPOT2 in regions with high susceptibility contrasts, like the prostate. Our proposal, DESPO+, employs the full bSSFP and SPGR models with a dictionary-based method to reconstruct 3D T1/T2 maps in the prostate region without off-resonance banding. METHODS DESPO+ modifies the bSSFP acquisition of the original variable flip angle DESPOT2. DESPO+ uses variable repetition and echo times, employing a dictionary-based method of the full bSSFP and SPGR models to reconstruct T1, T2, and Proton Density (PD) simultaneously. The proposed DESPO+ method underwent testing through simulations, T1/T2 phantoms, and on fourteen healthy subjects. RESULTS The results reveal a significant reduction in T2 map banding artifacts compared to the original DESPOT2 method. DESPO+ approach reduced T2 errors by up to seven times compared to DESPOT2 in simulations and phantom experiments. We also synthesized in-vivo T1-weighted/T2-weighted images from the acquired maps using a spin-echo model to verify the map's quality when lacking a reference. For in-vivo imaging, the synthesized images closely resemble those from the clinical MRI protocol, reducing scan time by around 50% compared to traditional spin-echo T1-weighted/T2-weighted acquisitions. CONCLUSION DESPO+ provides an off-resonance insensitive and clinically available solution, enabling high-resolution 3D T1/T2 mapping and synthesized T1-weighted/T2-weighted images for the entire prostate, all achieved within a short scan time of 3.6 min, similar to DESPOT1/T2.
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Affiliation(s)
- Ronal Coronado
- Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Chile; Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile
| | - Carlos Castillo-Passi
- Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile; School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom; Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Cecilia Besa
- Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile; Department of Radiology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo Irarrazaval
- Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Chile; Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile; Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile.
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5
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He T, Zur Y, Montrazi ET, Frydman L. Phase-Incremented Steady-State Free Precession as an Alternate Route to High-Resolution NMR. J Am Chem Soc 2024; 146:3615-3621. [PMID: 38291738 PMCID: PMC10870713 DOI: 10.1021/jacs.3c12954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 01/20/2024] [Accepted: 01/22/2024] [Indexed: 02/01/2024]
Abstract
Pulsed Fourier transform nuclear magnetic resonance (FT-NMR) has reigned supreme in high-resolution, high-field spectroscopy─particularly when targeting complex liquid-state samples involving multiple sharp peaks spread over large spectral bandwidths. It is known, however, that if spectral resolution is not a must, the FT-based approach is not necessarily the optimal route for maximizing NMR sensitivity: if T2 ≈ T1, as often found in solutions, Carr's steady-state free-precession (SSFP) approach can in principle provide a superior signal-to-noise ratio per √(acquisition_time) (SNRt). A rapid train of pulses will then lead to a transverse component that reaches up to 50% of the thermal equilibrium magnetization, provided that pulses are applied at repetition times TR ≪ T2, T1, and that a single suitable offset is involved. It is generally assumed that having to deal with multiple chemical shifts deprives SSFP from its advantages. The present study revisits this assumption by introducing an approach whereby arbitrarily short SSFP-derived free induction decays (FIDs) can deliver high-resolution spectra, without suffering from peak broadenings or phase distortions. To achieve discrimination among nearby frequencies, signals arising from a series of regularly phase-increased excitation pulses are collected. Given SSFP's amplitude and phase sensitivity to the spins' offset, this enables the resolution of sites according to their chemical shift position. In addition, the extreme fold-over associated with SSFP acquisitions is dealt with by a customized discrete FT of the interpulse time-domain signal. Solution-state 13C NMR spectra which compare well with FT-NMR data in terms of sensitivity, bandwidth, and resolution can then be obtained.
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Affiliation(s)
- Tian He
- Department
of Chemical and Biological Physics, Weizmann
Institute, 7610001 Rehovot, Israel
- Department
of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Yuval Zur
- Insightec
Ltd, 3903203 Tirat Carmel, Israel
| | - Elton T. Montrazi
- Department
of Chemical and Biological Physics, Weizmann
Institute, 7610001 Rehovot, Israel
| | - Lucio Frydman
- Department
of Chemical and Biological Physics, Weizmann
Institute, 7610001 Rehovot, Israel
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6
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Tong C, Pang Y, Wang Y. HIWDNet: A hybrid image-wavelet domain network for fast magnetic resonance image reconstruction. Comput Biol Med 2022; 151:105947. [PMID: 36334363 DOI: 10.1016/j.compbiomed.2022.105947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 07/16/2022] [Accepted: 08/06/2022] [Indexed: 12/27/2022]
Abstract
The application of Magnetic Resonance Imaging (MRI) is limited due to the long acquisition time of k-space signals. Recently, many deep learning-based MR image reconstruction methods have been proposed to reduce acquisition time and improve MRI image quality by reconstructing images from under-sampled k-space data. However, these methods suffer from two shortcomings. Firstly, the reconstruction network are mainly designed in the image domain or frequency domain, while ignoring the characteristics of time-frequency features in the wavelet domain. In addition, the existing cross-domain methods design the same reconstruction network in different transform domains, so that the network cannot learn targeted information for different domains. To solve the above problems, we propose a Hybrid Image-Wavelet Domain Reconstruction Network (HIWDNet) for fast MRI reconstruction. Specifically, we employ Cross-scale Dense Feature Fusion Module (CDFFM) in the image domain to reconstruct the basic structure of MR images, while introducing Region Adaptive Artifact Removal Module (RAARM) to remove aliasing artifacts in large areas. Then, a Wavelet Sub-band Reconstruction Module (WSRM) is proposed to refine wavelet sub-bands to improve the accuracy of HIWDNet. The proposed method is evaluated in different sampling modes on the fastMRI dataset, the CC359 dataset and the IXI dataset. Extensive experimental results show that HIWDNet achieves better results on both SSIM and PSNR evaluation metrics compared with other methods.
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Affiliation(s)
- Chuan Tong
- TJK-BIIT Lab, School of Electrical and Information Engineering, Tianjin University, Tianjin, 300072, China.
| | - Yanwei Pang
- TJK-BIIT Lab, School of Electrical and Information Engineering, Tianjin University, Tianjin, 300072, China.
| | - Yueze Wang
- TJK-BIIT Lab, School of Electrical and Information Engineering, Tianjin University, Tianjin, 300072, China.
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7
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Hoff MN, Xiang QS, Cross NM, Hippe D, Andre JB. Motion resilience of the balanced steady-state free precession geometric solution. Magn Reson Med 2022; 89:192-204. [PMID: 36093906 DOI: 10.1002/mrm.29438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/26/2022] [Accepted: 08/11/2022] [Indexed: 11/06/2022]
Abstract
PURPOSE Many MRI sequences are sensitive to motion and its associated artifacts. The linearized geometric solution (LGS), a balanced steady-state free precession (bSSFP) off-resonance signal demodulation technique, is evaluated with respect to motion artifact resilience. THEORY AND METHODS The mechanism and extent of LGS motion artifact resilience is examined in simulated, flow phantom, and in vivo clinical imaging. Motion artifact correction capabilities are decoupled from susceptibility artifact correction when feasible to permit controlled analysis of motion artifact correction when comparing the LGS with standard and phase-cycle-averaged (complex sum) bSSFP imaging. RESULTS Simulations reveal that the LGS demonstrates motion artifact reduction capabilities similar to standard clinical bSSFP imaging techniques, with slightly greater resilience in high SNR regions and for shorter-duration motion. Flow phantom experiments assert that the LGS reduces shorter-duration motion artifact error by ∼24%-65% relative to the complex sum, whereas reconstructions exhibit similar error reduction for constant motion. In vivo analysis demonstrates that in the internal auditory canal/orbits, the LGS was deemed to have less artifact in 24%/49% and similar artifact in 76%/51% of radiological assessments relative to the complex sum, and the LGS had less artifact in 97%/81% and similar artifact in 3%/16% of assessments relative to standard bSSFP. Only 2 of 63 assessments deemed the LGS inferior to either complex sum or standard bSSFP in terms of artifact reduction. CONCLUSION The LGS provides sufficient bSSFP motion artifact resilience to permit robust elimination of susceptibility artifacts, inspiring its use in a wide variety of applications.
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Affiliation(s)
- Michael N Hoff
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA
| | - Qing-San Xiang
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nathan M Cross
- Department of Radiology, University of Washington, Seattle, Washington, USA
| | - Daniel Hippe
- Clinical Biostatistics, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Jalal B Andre
- Department of Radiology, University of Washington, Seattle, Washington, USA
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8
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Seginer A, Schmidt R. Phase-based fast 3D high-resolution quantitative T 2 MRI in 7 T human brain imaging. Sci Rep 2022; 12:14088. [PMID: 35982143 PMCID: PMC9388657 DOI: 10.1038/s41598-022-17607-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 07/28/2022] [Indexed: 12/04/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a powerful and versatile technique that offers a range of physiological, diagnostic, structural, and functional measurements. One of the most widely used basic contrasts in MRI diagnostics is transverse relaxation time (T2)-weighted imaging, but it provides only qualitative information. Realizing quantitative high-resolution T2 mapping is imperative for the development of personalized medicine, as it can enable the characterization of diseases progression. While ultra-high-field (≥ 7 T) MRI offers the means to gain new insights by increasing the spatial resolution, implementing fast quantitative T2 mapping cannot be achieved without overcoming the increased power deposition and radio frequency (RF) field inhomogeneity at ultra-high-fields. A recent study has demonstrated a new phase-based T2 mapping approach based on fast steady-state acquisitions. We extend this new approach to ultra-high field MRI, achieving quantitative high-resolution 3D T2 mapping at 7 T while addressing RF field inhomogeneity and utilizing low flip angle pulses; overcoming two main ultra-high field challenges. The method is based on controlling the coherent transverse magnetization in a steady-state gradient echo acquisition; achieved by utilizing low flip angles, a specific phase increment for the RF pulses, and short repetition times. This approach simultaneously extracts both T2 and RF field maps from the phase of the signal. Prior to in vivo experiments, the method was assessed using a 3D head-shaped phantom that was designed to model the RF field distribution in the brain. Our approach delivers fast 3D whole brain images with submillimeter resolution without requiring special hardware, such as multi-channel transmit coil, thus promoting high usability of the ultra-high field MRI in clinical practice.
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Affiliation(s)
| | - Rita Schmidt
- Department of Brain Sciences, Weizmann Institute of Science, Rehovot, Israel. .,The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel.
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9
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Mizukami S, Watanabe Y, Mizoguchi T, Gomi T, Hara H, Takei H, Fukunishi N, Ishikawa KL, Fukuda S, Maeyama T. Whole Three-Dimensional Dosimetry of Carbon Ion Beams with an MRI-Based Nanocomposite Fricke Gel Dosimeter Using Rapid T1 Mapping Method. Gels 2021; 7:233. [PMID: 34940293 PMCID: PMC8701283 DOI: 10.3390/gels7040233] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/23/2021] [Accepted: 11/23/2021] [Indexed: 11/17/2022] Open
Abstract
MRI-based gel dosimeters are attractive systems for the evaluation of complex dose distributions in radiotherapy. In particular, the nanocomposite Fricke gel dosimeter is one among a few dosimeters capable of accurately evaluating the dose distribution of heavy ion beams. In contrast, reduction of the scanning time is a challenging issue for the acquisition of three-dimensional volume data. In this study, we investigated a three-dimensional dose distribution measurement method for heavy ion beams using variable flip angle (VFA), which is expected to significantly reduce the MRI scanning time. Our findings clarified that the whole three-dimensional dose distribution could be evaluated within the conventional imaging time (20 min) and quality of one cross-section.
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Affiliation(s)
- Shinya Mizukami
- School of Allied Health Sciences, Kitasato University, Sagamihara 252-0373, Japan; (S.M.); (Y.W.); (T.G.); (H.H.)
| | - Yusuke Watanabe
- School of Allied Health Sciences, Kitasato University, Sagamihara 252-0373, Japan; (S.M.); (Y.W.); (T.G.); (H.H.)
| | - Takahiro Mizoguchi
- Graduate School of Medical Sciences, Kitasato University, Sagamihara 252-0373, Japan;
| | - Tsutomu Gomi
- School of Allied Health Sciences, Kitasato University, Sagamihara 252-0373, Japan; (S.M.); (Y.W.); (T.G.); (H.H.)
| | - Hidetake Hara
- School of Allied Health Sciences, Kitasato University, Sagamihara 252-0373, Japan; (S.M.); (Y.W.); (T.G.); (H.H.)
| | - Hideyuki Takei
- Proton Medical Research Center, University of Tsukuba Hospital, Tsukuba 305-8576, Japan;
| | - Nobuhisa Fukunishi
- Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198, Japan;
| | - Kenichi L. Ishikawa
- Department of Nuclear Engineering and Management, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan;
| | - Shigekazu Fukuda
- QST Hospital, National Institutes for Quantum Science and Technology, Chiba 263-8555, Japan;
| | - Takuya Maeyama
- Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198, Japan;
- Department of Chemistry, School of Science, Kitasato University, Sagamihara 252-0373, Japan
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10
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Peters DC, Markovic S, Bao Q, Preise D, Sasson K, Agemy L, Scherz A, Frydman L. Improving deuterium metabolic imaging (DMI) signal-to-noise ratio by spectroscopic multi-echo bSSFP: A pancreatic cancer investigation. Magn Reson Med 2021; 86:2604-2617. [PMID: 34196041 DOI: 10.1002/mrm.28906] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 06/07/2021] [Accepted: 06/07/2021] [Indexed: 12/15/2022]
Abstract
PURPOSE Deuterium metabolic imaging (DMI) maps the uptake of deuterated precursors and their conversion into lactate and other markers of tumor metabolism. Even after leveraging 2 H's short T1 s, DMI's signal-to-noise ratio (SNR) is limited. We hypothesize that a multi-echo balanced steady-state free precession (ME-bSSFP) approach would increase SNR compared to chemical shift imaging (CSI), while achieving spectral isolation of the metabolic precursors and products. METHODS Suitably tuned 2 H ME-bSSFP (five echo times [TEs], ΔTE = 2.2 ms, repetition time [TR]/flip-angle = 12 ms/60°) was implemented at 15.2T and compared to CSI (TR/flip-angle = 95 ms/90°) regarding SNR and spectral isolation, in simulations, in deuterated phantoms and for the in vivo diagnosis of a mouse tumor model of pancreatic adenocarcinoma (N = 10). RESULTS Simulations predicted an SNR increase vs. CSI of 3-5, and that the peaks of 2 H-water, 2 H6,6' -glucose, and 2 H3,3' -lactate can be well isolated by ME-bSSFP; phantoms confirmed this. In vivo, at equal spatial resolution (1.25 × 1.25 mm2 ) and scan time (10 min), 2 H6,6' -glucose's and 2 H3,3' -lactate's SNR were indeed higher for bSSFP than for CSI, three-fold for glucose (57 ± 30 vs. 19 ± 11, P < .001), doubled for water (13 ± 5 vs. 7 ± 3, P = .005). The time courses and overall localization of all metabolites agreed well, comparing CSI against ME-bSSFP. However, a clearer localization of glucose in kidneys and bladder, the detection of glucose-avid rims in certain tumors, and a heterogeneous pattern of intra-tumor lactate production could only be observed using ME-bSSFP's higher resolution. CONCLUSIONS ME-bSSFP provides greater SNR per unit time than CSI, providing for higher spatial resolution mapping of glucose uptake and lactate production in tumors.
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Affiliation(s)
- Dana C Peters
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, Connecticut, USA
| | - Stefan Markovic
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Qingjia Bao
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Dina Preise
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Keren Sasson
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Lilach Agemy
- Department of Plant and Environmental Science, Weizmann Institute of Science, Rehovot, Israel
| | - Avigdor Scherz
- Department of Plant and Environmental Science, Weizmann Institute of Science, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
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11
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Lally PJ, Matthews PM, Bangerter NK. Unbalanced SSFP for super-resolution in MRI. Magn Reson Med 2020; 85:2477-2489. [PMID: 33201538 PMCID: PMC8972796 DOI: 10.1002/mrm.28593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/18/2020] [Accepted: 10/20/2020] [Indexed: 11/13/2022]
Abstract
Purpose: To achieve rapid, low specific absorption rate (SAR) super-resolution imaging by exploiting the characteristic magnetization off-resonance profile in SSFP. Theory and Methods: In the presented technique, low flip angle unbalanced SSFP imaging is used to acquire a series of images at a low nominal resolution that are then combined in a super-resolution strategy analogous to non-linear structured illumination microscopy. This is demonstrated in principle via Bloch simulations and synthetic phantoms, and the performance is quantified in terms of point-spread function (PSF) and SNR for gray and white matter from field strengths of 0.35T to 9.4T. A k-space reconstruction approach is proposed to account for B0 effects. This was applied to reconstruct super-resolution images from a test object at 9.4T. Results: Artifact-free super-resolution images were produced after incorporating sufficient preparation time for the magnetization to approach the steady state. High-resolution images of a test object were obtained at 9.4T, in the presence of considerable B0 inhomogeneity. For gray matter, the highest achievable resolution ranges from 3% of the acquired voxel dimension at 0.35T, to 9% at 9.4T. For white matter, this corresponds to 3% and 10%, respectively. Compared to an equivalent segmented gradient echo acquisition at the optimal flip angle, with a fixed TR of 8 ms, gray matter has up to 34% of the SNR at 9.4T while using a ×10 smaller flip angle. For white matter, this corresponds to 29% with a ×11 smaller flip angle. Conclusion: This approach achieves high degrees of super-resolution enhancement with minimal RF power requirements.
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Affiliation(s)
- Peter J Lally
- Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Paul M Matthews
- Department of Brain Sciences, Imperial College London, London, United Kingdom.,UK Dementia Research Institute Centre at Imperial College London, London, United Kingdom
| | - Neal K Bangerter
- Department of Bioengineering, Imperial College London, London, United Kingdom
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12
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Tendler BC, Foxley S, Hernandez-Fernandez M, Cottaar M, Scott C, Ansorge O, Miller KL, Jbabdi S. Use of multi-flip angle measurements to account for transmit inhomogeneity and non-Gaussian diffusion in DW-SSFP. Neuroimage 2020; 220:117113. [PMID: 32621975 PMCID: PMC7573656 DOI: 10.1016/j.neuroimage.2020.117113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 06/25/2020] [Accepted: 06/27/2020] [Indexed: 11/06/2022] Open
Abstract
Diffusion-weighted steady-state free precession (DW-SSFP) is an SNR-efficient diffusion imaging method. The improved SNR and resolution available at ultra-high field has motivated its use at 7T. However, these data tend to have severe B1 inhomogeneity, leading not only to spatially varying SNR, but also to spatially varying diffusivity estimates, confounding comparisons both between and within datasets. This study proposes the acquisition of DW-SSFP data at two-flip angles in combination with explicit modelling of non-Gaussian diffusion to address B1 inhomogeneity at 7T. Data were acquired from five fixed whole human post-mortem brains with a pair of flip angles that jointly optimize the diffusion contrast-to-noise (CNR) across the brain. We compared one- and two-flip angle DW-SSFP data using a tensor model that incorporates the full DW-SSFP Buxton signal, in addition to tractography performed over the cingulum bundle and pre-frontal cortex using a ball & sticks model. The two-flip angle DW-SSFP data produced angular uncertainty and tractography estimates close to the CNR optimal regions in the single-flip angle datasets. The two-flip angle tensor estimates were subsequently fitted using a modified DW-SSFP signal model that incorporates a gamma distribution of diffusivities. This allowed us to generate tensor maps at a single effective b-value yielding more consistent SNR across tissue, in addition to eliminating the B1 dependence on diffusion coefficients and orientation maps. Our proposed approach will allow the use of DW-SSFP at 7T to derive diffusivity estimates that have greater interpretability, both within a single dataset and between experiments.
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Affiliation(s)
- Benjamin C Tendler
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Sean Foxley
- Department of Radiology, University of Chicago, Chicago, IL, USA
| | | | - Michiel Cottaar
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Connor Scott
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Olaf Ansorge
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Karla L Miller
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Saad Jbabdi
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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13
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Tendler BC, Foxley S, Cottaar M, Jbabdi S, Miller KL. Modeling an equivalent b-value in diffusion-weighted steady-state free precession. Magn Reson Med 2020; 84:873-884. [PMID: 31922283 PMCID: PMC7216928 DOI: 10.1002/mrm.28169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 12/13/2019] [Accepted: 12/18/2019] [Indexed: 11/26/2022]
Abstract
PURPOSE Diffusion-weighted steady-state free precession (DW-SSFP) is shown to provide a means to probe non-Gaussian diffusion through manipulation of the flip angle. A framework is presented to define an effective b-value in DW-SSFP. THEORY The DW-SSFP signal is a summation of coherence pathways with different b-values. The relative contribution of each pathway is dictated by the flip angle. This leads to an apparent diffusion coefficient (ADC) estimate that depends on the flip angle in non-Gaussian diffusion regimes. By acquiring DW-SSFP data at multiple flip angles and modeling the variation in ADC for a given form of non-Gaussianity, the ADC can be estimated at a well-defined effective b-value. METHODS A gamma distribution is used to model non-Gaussian diffusion, embedded in the Buxton signal model for DW-SSFP. Monte-Carlo simulations of non-Gaussian diffusion in DW-SSFP and diffusion-weighted spin-echo sequences are used to verify the proposed framework. Dependence of ADC on flip angle in DW-SSFP is verified with experimental measurements in a whole, human postmortem brain. RESULTS Monte-Carlo simulations reveal excellent agreement between ADCs estimated with diffusion-weighted spin-echo and the proposed framework. Experimental ADC estimates vary as a function of flip angle over the corpus callosum of the postmortem brain, estimating the mean and standard deviation of the gamma distribution as 1.50 · 10 - 4 mm2 /s and 2.10 · 10 - 4 mm2 /s. CONCLUSION DW-SSFP can be used to investigate non-Gaussian diffusion by varying the flip angle. By fitting a model of non-Gaussian diffusion, the ADC in DW-SSFP can be estimated at an effective b-value, comparable to more conventional diffusion sequences.
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Affiliation(s)
- Benjamin C. Tendler
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Sean Foxley
- Department of RadiologyUniversity of ChicagoChicagoIllinois
| | - Michiel Cottaar
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Saad Jbabdi
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Karla L. Miller
- Wellcome Centre for Integrative NeuroimagingFMRIBNuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
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14
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Mahon C, Gatehouse P, Baksi J, Mohiaddin RH. The mysterious needle in the heart: a case report. Eur Heart J Case Rep 2020; 4:1-4. [PMID: 33043238 PMCID: PMC7534165 DOI: 10.1093/ehjcr/ytaa083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 10/31/2019] [Accepted: 03/17/2020] [Indexed: 11/18/2022]
Abstract
Background A 53-year-old female with dyspnoea and atypical chest pain. Her electrocardiogram demonstrated a left bundle branch block, transthoracic echocardiogram demonstrated a mildly impaired left ventricle ejection fraction, and coronary angiogram revealed unobstructed coronary arteries. She was referred for cardiovascular magnetic resonance (CMR) for structural and functional assessment. Her imaging revealed an unexpected finding of an off-resonance artefact within the ventricle wall. This material was secondary to a ferromagnetic material. Case summary Chest X ray and computer tomography confirmed a needle-shaped structure in the ventricle wall. Understanding the basis of this off-resonance artefact aided in a new diagnosis, raised questions on the origin of the material, patient safety, and implementation of corrective strategies to optimize image acquisition. Discussion The continued development of CMR is revolutionizing our ability to establish diagnosis and guide patient treatment. The CMR sequences can be prone to artefact. This case highlights the importance of understanding the basis of CMR artefacts.
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Affiliation(s)
- Ciara Mahon
- Department of Cardiovascular Magnetic Resonance, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK
| | - Peter Gatehouse
- Department of Cardiovascular Magnetic Resonance, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK
| | - John Baksi
- Department of Cardiovascular Magnetic Resonance, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK
- National Heart and Lung Institute, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Raad H Mohiaddin
- Department of Cardiovascular Magnetic Resonance, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK
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15
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Guenthner C, Sethi S, Troelstra M, van Gorkum RJ, Gastl M, Sinkus R, Kozerke S. Unipolar MR elastography: Theory, numerical analysis and implementation. NMR IN BIOMEDICINE 2020; 33:e4138. [PMID: 31664745 PMCID: PMC7003474 DOI: 10.1002/nbm.4138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 06/10/2019] [Accepted: 06/14/2019] [Indexed: 06/10/2023]
Abstract
In MR elastography (MRE), zeroth moment balanced motion-encoding gradients (MEGs) are incorporated into MRI sequences to induce a phase shift proportional to the local displacement caused by external actuation. To maximize the signal-to-noise ratio (SNR), fractional encoding is employed, i.e., the MEG duration is reduced below the wave period. Here, gradients encode primarily the velocity of the motion-reducing encoding efficiency. Thus, in GRE-MRE, T2 * decay and motion sensitivity have to be balanced, imposing a lower limit on repetition times (TRs). We propose to use a single trapezoidal gradient, a "unipolar gradient", to directly encode spin displacement. Such gradients cannot be used in conventional sequences as they exhibit a large zeroth moment and dephase magnetization. By time-reversing a spoiled SSFP sequence, the spoiling gradient becomes an efficient unipolar MEG. The proposed "unipolar MRE" technique benefits from this approach in three ways: first, displacement encoding is split over multiple TRs increasing motion sensitivity; second, spoiler and MEG coincide, allowing a reduction in TR; third, motion sensitivity of a typical unipolar lobe is of an order of magnitude higher than a bipolar MEG of equal duration. In this work, motion encoding using unipolar MRE is analyzed using the extended phase graph (EPG) formalism with a periodic motion propagator. As an approximation, the two-transverse TR approximation for diffusion-weighted SSFP is extended to incorporate cyclic motion. A complex encoding efficiency metric is introduced to compare the displacement fields of unipolar and conventional GRE-MRE sequences in both magnitude and phase. The derived theoretical encoding equations are used to characterize the proposed sequence using an extensive parameter study. Unipolar MRE is validated against conventional GRE-MRE in a phantom study showing excellent agreement between measured displacement fields. In addition, unipolar MRE yields significantly increased octahedral shear strain-SNR relative to conventional GRE-MRE and allows for the recovery of high stiffness inclusions, where conventional GRE-MRE fails.
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Affiliation(s)
- Christian Guenthner
- Institute for Biomedical EngineeringUniversity and ETH ZurichZurichSwitzerland
| | - Sweta Sethi
- Division of Research OncologyGuy's and Saint Thomas' NHS Foundation TrustLondonUK
| | - Marian Troelstra
- Division for Imaging Sciences & Biomedical EngineeringKing's College LondonLondonUK
- Department of Radiology and Nuclear MedicineUniversity Medical Center AmsterdamAmsterdamThe Netherlands
| | | | - Mareike Gastl
- Institute for Biomedical EngineeringUniversity and ETH ZurichZurichSwitzerland
| | - Ralph Sinkus
- Division for Imaging Sciences & Biomedical EngineeringKing's College LondonLondonUK
| | - Sebastian Kozerke
- Institute for Biomedical EngineeringUniversity and ETH ZurichZurichSwitzerland
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16
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Neumann W, Pusch TP, Siegfarth M, Schad LR, Stallkamp JL. CT and MRI compatibility of flexible 3D-printed materials for soft actuators and robots used in image-guided interventions. Med Phys 2019; 46:5488-5498. [PMID: 31587313 DOI: 10.1002/mp.13852] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/12/2019] [Accepted: 09/26/2019] [Indexed: 01/09/2023] Open
Abstract
PURPOSE Three-dimensional (3D) printing allows for the fabrication of medical devices with complex geometries, such as soft actuators and robots that can be used in image-guided interventions. This study investigates flexible and rigid 3D-printing materials in terms of their impact on multimodal medical imaging. METHODS The generation of artifacts in clinical computer tomography (CT) and magnetic resonance (MR) imaging was evaluated for six flexible and three rigid materials, each with a cubical and a cylindrical geometry, and for one exemplary flexible fluidic actuator. Additionally, CT Hounsfield units (HU) were quantified for various parameter sets iterating peak voltage, x-ray tube current, slice thickness, and convolution kernel. RESULTS We found the image artifacts caused by the materials to be negligible in both CT and MR images. The HU values mainly depended on the elemental composition of the materials and applied peak voltage was ranging between 80 and 140 kVp. Flexible, nonsilicone-based materials were ranged between 51 and 114 HU. The voltage dependency was less than 29 HU. Flexible, silicone-based materials were ranged between 60 and 365 HU. The voltage-dependent influence was as large as 172 HU. Rigid materials ranged between -69 and 132 HU. The voltage-dependent influence was <33 HU. CONCLUSIONS All tested materials may be employed for devices placed in the field of view during CT and MR imaging as no significant artifacts were measured. Moreover, the material selection in CT could be based on the desired visibility of the material depending on the application. Given the wide availability of the tested materials, we expect our results to have a positive impact on the development of devices and robots for image-guided interventions.
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Affiliation(s)
- Wiebke Neumann
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Tim P Pusch
- Fraunhofer Institute for Manufacturing Engineering and Automation, Project Group for Automation in Medicine and Biotechnology, 68167, Mannheim, Germany
| | - Marius Siegfarth
- Fraunhofer Institute for Manufacturing Engineering and Automation, Project Group for Automation in Medicine and Biotechnology, 68167, Mannheim, Germany
| | - Lothar R Schad
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Jan L Stallkamp
- Fraunhofer Institute for Manufacturing Engineering and Automation, Project Group for Automation in Medicine and Biotechnology, 68167, Mannheim, Germany.,Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
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17
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Pfister J, Blaimer M, Kullmann WH, Bartsch AJ, Jakob PM, Breuer FA. Simultaneous T 1 and T 2 measurements using inversion recovery TrueFISP with principle component-based reconstruction, off-resonance correction, and multicomponent analysis. Magn Reson Med 2019; 81:3488-3502. [PMID: 30687949 DOI: 10.1002/mrm.27657] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 12/14/2018] [Accepted: 12/16/2018] [Indexed: 01/14/2023]
Abstract
PURPOSE To improve the reconstruction quality for quantitative T1 and T2 measurements using the inversion recovery (IR) TrueFISP sequence and to demonstrate the potential for multicomponent analysis. METHODS The iterative reconstruction method takes advantage of the high redundancy in the smooth exponential signals using principle component analysis (PCA). Multicomponent information is preserved and allows voxel-by-voxel computation of relaxation time spectra with an inverse Laplace transform. Off-resonance effects are analytically and numerically investigated and a correction approach is presented. RESULTS Single-shot IR TrueFISP in vivo measurements on healthy volunteers demonstrate the improved reconstruction performance compared to a view sharing (k-space weighted image contrast [KWIC]) reconstruction. Especially, tissue components with short apparent relaxation times T1 * are not filtered out and can be identified in the relaxation time spectra. These components include myelin in the human brain (T1 * ≈ 130 ms) and extra cranial subcutaneous fat. CONCLUSION The PCA-based reconstruction method improves the temporal accuracy and preserves multicomponent information. Spatially resolved relaxation time spectra can be obtained and allow the identification of tissue types with short, apparent relaxation times.
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Affiliation(s)
- Julian Pfister
- Magnetic Resonance and X-ray Imaging Department, Fraunhofer Development Center for X-Ray Technology (EZRT), Würzburg, Germany.,Department of Experimental Physics V, University of Würzburg, Würzburg, Germany.,Institute of Medical Engineering Schweinfurt, University of Applied Sciences Würzburg-Schweinfurt, Schweinfurt, Germany
| | - Martin Blaimer
- Magnetic Resonance and X-ray Imaging Department, Fraunhofer Development Center for X-Ray Technology (EZRT), Würzburg, Germany
| | - Walter H Kullmann
- Institute of Medical Engineering Schweinfurt, University of Applied Sciences Würzburg-Schweinfurt, Schweinfurt, Germany
| | - Andreas J Bartsch
- Department of Neuroradiology, University of Heidelberg, Heidelberg, Germany.,Department of Neuroradiology, University Hospital Würzburg, Würzburg, Germany.,WIN/FMRIB Centre, Department of Clinical Neurology, University of Oxford, Oxford, UK.,Radiologie Bamberg, Bamberg, Germany
| | - Peter M Jakob
- Department of Experimental Physics V, University of Würzburg, Würzburg, Germany
| | - Felix A Breuer
- Magnetic Resonance and X-ray Imaging Department, Fraunhofer Development Center for X-Ray Technology (EZRT), Würzburg, Germany
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18
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Roeloffs V, Rosenzweig S, Holme HCM, Uecker M, Frahm J. Frequency-modulated SSFP with radial sampling and subspace reconstruction: A time-efficient alternative to phase-cycled bSSFP. Magn Reson Med 2018; 81:1566-1579. [PMID: 30357904 DOI: 10.1002/mrm.27505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/05/2018] [Accepted: 08/03/2018] [Indexed: 11/11/2022]
Abstract
PURPOSE A novel subspace-based reconstruction method for frequency-modulated balanced steady-state free precession (fmSSFP) MRI is presented. In this work, suitable data acquisition schemes, subspace sizes, and efficiencies for banding removal are investigated. THEORY AND METHODS By combining a fmSSFP MRI sequence with a 3D stack-of-stars trajectory, scan efficiency is maximized as spectral information is obtained without intermediate preparation phases. A memory-efficient reconstruction routine is implemented by introducing the low-frequency Fourier transform as a subspace which allows for the formulation of a convex reconstruction problem. The removal of banding artifacts is investigated by comparing the proposed acquisition and reconstruction technique to phase-cycled bSSFP MRI. Aliasing properties of different undersampling schemes are analyzed and water/fat separation is demonstrated by reweighting the reconstructed subspace coefficients to generate virtual spectral responses in a post-processing step. RESULTS A simple root-of-sum-of-squares combination of the reconstructed subspace coefficients yields high-SNR images with the characteristic bSSFP contrast but without banding artifacts. Compared to Golden-Angle trajectories, turn-based sampling schemes were superior in minimizing aliasing across reconstructed subspace coefficients. Water/fat separated images of the human knee were obtained by reweighting subspace coefficients. CONCLUSIONS The novel subspace-based fmSSFP MRI technique emerges as a time-efficient alternative to phase-cycled bSFFP. The method does not need intermediate preparation phases, offers high SNR and avoids banding artifacts. Reweighting of the reconstructed subspace coefficients allows for generating virtual spectral responses with applications to water/fat separation.
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Affiliation(s)
- Volkert Roeloffs
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
| | - Sebastian Rosenzweig
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - H Christian M Holme
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - Martin Uecker
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
| | - Jens Frahm
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.,German Centre for Cardiovascular Research (DZHK), Göttingen, Germany
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19
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Bipin Mehta B, Coppo S, Frances McGivney D, Ian Hamilton J, Chen Y, Jiang Y, Ma D, Seiberlich N, Gulani V, Alan Griswold M. Magnetic resonance fingerprinting: a technical review. Magn Reson Med 2018; 81:25-46. [PMID: 30277265 DOI: 10.1002/mrm.27403] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 05/01/2018] [Accepted: 05/21/2018] [Indexed: 01/31/2023]
Abstract
Multiparametric quantitative imaging is gaining increasing interest due to its widespread advantages in clinical applications. Magnetic resonance fingerprinting is a recently introduced approach of fast multiparametric quantitative imaging. In this article, magnetic resonance fingerprinting acquisition, dictionary generation, reconstruction, and validation are reviewed.
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Affiliation(s)
- Bhairav Bipin Mehta
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio
| | - Simone Coppo
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio
| | - Debra Frances McGivney
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio
| | - Jesse Ian Hamilton
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Yong Chen
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio
| | - Yun Jiang
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio
| | - Dan Ma
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio
| | - Nicole Seiberlich
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Vikas Gulani
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio.,Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Mark Alan Griswold
- Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio.,Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
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20
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Yang A, Xiao XH, Wang ZL, Wang ZY, Wang KY. T2-weighted balanced steady-state free procession MRI evaluated for diagnosing placental adhesion disorder in late pregnancy. Eur Radiol 2018; 28:3770-3778. [PMID: 29651765 DOI: 10.1007/s00330-018-5388-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 01/19/2018] [Accepted: 02/16/2018] [Indexed: 10/17/2022]
Abstract
OBJECTIVE This study evaluated the imaging characteristics and accuracy of T2-weighted (T2W) balanced steady-state free procession (b-SSFP) magnetic resonance imaging, relative to b-SSFP or single-shot fast spin echo (SSFSE), for the diagnosis of placental adhesion disorder (PAD). METHODS Fifty-one pregnant patients suspected of PAD were examined with T2W b-SSFP, b-SSFP and SSFSE. The image types were independently analysed for signs of PAD: abnormal placental bulge (APB), dark intraplacental bands (DIB), placental heterogeneity (PH) and placental protrusion into adjacent structures (PPAS). The sequences were compared for muscle-to-placenta signal ratio, signs of PAD and area under the receiver operating characteristic curve (AUC) for diagnostic accuracy of PAD. RESULTS PAD was confirmed in 34 women. The muscle-to-placenta signal ratio was highest in the T2W b-SSFP. The diagnostic rates of APB in T2W b-SSFP were comparable to that of b-SSFP, but were significantly higher than that of SSFSE. The rates of PH in SSFE were comparable to that of b-SSFP, but both were significantly lower than that of T2W b-SSFP. The rates of DIB were significantly higher in T2W b-SSFP images compared with SSFSE. Rates of PPAS were comparable among three sequences. The AUCs of the T2W b-SSFP, b-SSFP and SSFSE were 0.966, 0.890 and 0.823, respectively. CONCLUSION T2W b-SSFP has high diagnostic accuracy for PAD relative to SSFSE or b-SSFP, which may be due to its high SNR, T2-weighting and lack of blur. KEY POINTS • Signal myometrium-to-placenta ratio was highest in the T2W b-SSFP images. • Diagnostic rate of APB in T2W b-SSFP was highest. • Diagnostic rate of DIB was higher in T2W b-SSFP than in SSFSE. • Diagnostic rate of PH in T2W b-SSFP was highest. • Maximum AUC for diagnostic accuracy of PAD was in T2W b-SSFP.
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Affiliation(s)
- Ang Yang
- MR department of Affiliated Zhongshan City Hospital of Sun Yat-sen University, Sun Wendong Road No. 2, Zhongshan City, Guangdong Province, China.
| | - Xue Hong Xiao
- MR department of Affiliated Zhongshan City Hospital of Sun Yat-sen University, Sun Wendong Road No. 2, Zhongshan City, Guangdong Province, China
| | - Zhi Long Wang
- MR department of Affiliated Zhongshan City Hospital of Sun Yat-sen University, Sun Wendong Road No. 2, Zhongshan City, Guangdong Province, China
| | - Ze Yan Wang
- MR department of Affiliated Zhongshan City Hospital of Sun Yat-sen University, Sun Wendong Road No. 2, Zhongshan City, Guangdong Province, China
| | - Ke Yi Wang
- MR department of Affiliated Zhongshan City Hospital of Sun Yat-sen University, Sun Wendong Road No. 2, Zhongshan City, Guangdong Province, China
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21
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Rodríguez-Soto AE, Abdulmalik O, Langham MC, Schwartz N, Lee H, Wehrli FW. T 2 -prepared balanced steady-state free precession (bSSFP) for quantifying whole-blood oxygen saturation at 1.5T. Magn Reson Med 2018; 79:1893-1900. [PMID: 28718522 PMCID: PMC5771982 DOI: 10.1002/mrm.26835] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 06/06/2017] [Accepted: 06/21/2017] [Indexed: 11/11/2022]
Abstract
PURPOSE To establish a calibration equation to convert human blood T2 to the full range of oxygen saturation levels (HbO2 ) and physiologic hematocrit (Hct) values using a T2 -prepared balanced steady-state free precession sequence (T2 -SSFP) at 1.5T. METHODS Blood drawn from 10 healthy donors (29.1 ± 3.9 years old) was prepared into samples of varying HbO2 and Hct (n = 79), and imaged using T2 -SSFP sequence at 37°C and interrefocusing interval τ180 = 12 ms. The relationship between blood T2 , HbO2 , and Hct was established based on the model R2=R2,plasma+Hct (R2,RBC-R2,plasma)+k·Hct·(1-Hct)·(1-HbO2)2. Measured R2 and HbO2 levels were fit by the model yielding values of R2,plasma, R2,RBC, and k. T2 -SSFP and the established calibration equation were applied to extract HbO2 at the superior sagittal sinus (SSS) in vivo and were compared with susceptometry-based oximetry. RESULTS Constants derived from the fit were: k = 74.2 [s-1 ], R2,plasma = 1.5 [s-1 ], R2,RBC = 11.6 [s-1 ], the R2 of the fit was 0.95. Average HbO2 at the SSS in seven healthy volunteers was 65% ± 7% and 66% ± 7% via T2 - and susceptometry-based oximetry, respectively. Bland-Altman analysis indicated agreement between the two oximetric methods with no significant bias. CONCLUSION The calibration constants presented here should ensure improved accuracy for whole-blood oximetry based on T2 -SSFP at 1.5T. Magn Reson Med 79:1893-1900, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Ana E. Rodríguez-Soto
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA
| | - Osheiza Abdulmalik
- Division of Hematology, The Children’s Hospital of Philadelphia, Philadelphia, PA
| | - Michael C. Langham
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA
| | - Nadav Schwartz
- Maternal and Child Health Research Program, Department of OBGYN, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Hyunyeol Lee
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA
| | - Felix W. Wehrli
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA
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22
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He Y, Wang M, Chen X, Pohmann R, Polimeni JR, Scheffler K, Rosen BR, Kleinfeld D, Yu X. Ultra-Slow Single-Vessel BOLD and CBV-Based fMRI Spatiotemporal Dynamics and Their Correlation with Neuronal Intracellular Calcium Signals. Neuron 2018; 97:925-939.e5. [PMID: 29398359 PMCID: PMC5845844 DOI: 10.1016/j.neuron.2018.01.025] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 11/14/2017] [Accepted: 01/10/2018] [Indexed: 01/07/2023]
Abstract
Functional MRI has been used to map brain activity and functional connectivity based on the strength and temporal coherence of neurovascular-coupled hemodynamic signals. Here, single-vessel fMRI reveals vessel-specific correlation patterns in both rodents and humans. In anesthetized rats, fluctuations in the vessel-specific fMRI signal are correlated with the intracellular calcium signal measured in neighboring neurons. Further, the blood-oxygen-level-dependent (BOLD) signal from individual venules and the cerebral-blood-volume signal from individual arterioles show correlations at ultra-slow (<0.1 Hz), anesthetic-modulated rhythms. These data support a model that links neuronal activity to intrinsic oscillations in the cerebral vasculature, with a spatial correlation length of ∼2 mm for arterioles. In complementary data from awake human subjects, the BOLD signal is spatially correlated among sulcus veins and specified intracortical veins of the visual cortex at similar ultra-slow rhythms. These data support the use of fMRI to resolve functional connectivity at the level of single vessels.
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Affiliation(s)
- Yi He
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tuebingen, 72074 Tuebingen, Germany
| | - Maosen Wang
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tuebingen, 72074 Tuebingen, Germany
| | - Xuming Chen
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Graduate Training Centre of Neuroscience, International Max Planck Research School, University of Tuebingen, 72074 Tuebingen, Germany
| | - Rolf Pohmann
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany
| | - Jonathan R Polimeni
- MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA 02114, USA
| | - Klaus Scheffler
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany; Department of Biomedical Magnetic Resonance, University of Tübingen, 72076 Tübingen, Germany
| | - Bruce R Rosen
- MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA 02114, USA
| | - David Kleinfeld
- Department of Physics, University of California at San Diego, La Jolla, CA 92093, USA; Section of Neurobiology, University of California at San Diego, La Jolla, CA 92093, USA
| | - Xin Yu
- High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany.
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Malekian V, Nasiraei-Moghaddam A, Khajehim M. A robust SSFP technique for fMRI at ultra-high field strengths. Magn Reson Imaging 2018; 50:17-25. [PMID: 29466704 DOI: 10.1016/j.mri.2018.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 02/04/2018] [Accepted: 02/12/2018] [Indexed: 11/17/2022]
Abstract
A non-balanced (nb) SSFP-based fMRI method based on CE-FAST is presented to alleviate some shortcomings of high spatial-specificity techniques commonly used in high static magnetic fields. The proposed sequence does not suffer from the banding artifacts inherent to balanced (b) SSFP, has low geometrical distortions and SAR compared to spin-echo EPI, and in contrast to previous nbSSFP implementations, is applied at a TR, theoretically prescribed for the optimum contrast. Its non-balanced gradient was chosen to just dephase the unwanted signal component (2π dephasing per TR per voxel). 3D data were acquired from nine healthy subjects, who performed a visual-motor task on a 7 Tesla scanner. For comparison, experiments were accompanied by similar bSSFP and spin-echo acquisitions. Consistent activation was achieved in all subjects with theoretically optimal TR, in contrast to previous nbSSFP techniques. The signal stability as well as relative and absolute functional signal changes, were found to be comparable with bSSFP and spin-echo techniques. The results suggest that with suitable modifications, CE-FAST can be regarded as a robust SSFP-based method for high spatial specificity fMRI techniques.
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Affiliation(s)
- Vahid Malekian
- Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran
| | - Abbas Nasiraei-Moghaddam
- Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran.
| | - Mahdi Khajehim
- Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran; School of Cognitive Sciences, Institute for Research in Fundamental Sciences, Tehran, Iran
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24
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Han PK, Park H, Park SH. DC artifact correction for arbitrary phase-cycling sequence. Magn Reson Imaging 2017; 38:21-26. [DOI: 10.1016/j.mri.2016.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 12/15/2016] [Accepted: 12/15/2016] [Indexed: 11/17/2022]
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25
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Khajehim M, Nasiraei Moghaddam A. Investigating the spatial specificity of S2-SSFP fMRI: A Monte Carlo simulation approach. Magn Reson Imaging 2017; 37:282-289. [DOI: 10.1016/j.mri.2016.11.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 11/21/2016] [Accepted: 11/21/2016] [Indexed: 11/29/2022]
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26
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Zhang S, Liu Z, Grant A, Keupp J, Lenkinski RE, Vinogradov E. Balanced Steady-State Free Precession (bSSFP) from an effective field perspective: Application to the detection of chemical exchange (bSSFPX). JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 275:55-67. [PMID: 28012297 PMCID: PMC5810596 DOI: 10.1016/j.jmr.2016.12.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 12/02/2016] [Accepted: 12/03/2016] [Indexed: 05/08/2023]
Abstract
Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence. The bSSFP in itself is sensitive to the exchange processes; hence, no additional saturation or preparation is needed for CEST-like data acquisition. The bSSFP experiment can be regarded as observation during saturation, without separate saturation and acquisition modules as used in standard CEST and similar experiments. One of the differences from standard CEST methods is that the bSSFP spectrum is an XY-spectrum not a Z-spectrum. As the first proof-of-principle step, we have implemented the steady-state bSSFP sequence for chemical exchange detection (bSSFPX) and verified its feasibility in phantom studies. These studies have shown that bSSFPX can achieve exchange-mediated contrast comparable to the standard CEST experiment. Therefore, the bSSFPX method has a potential for fast and quantitative CEST data acquisition.
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Affiliation(s)
- Shu Zhang
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Zheng Liu
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Aaron Grant
- Division of MR Research, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | | | - Robert E Lenkinski
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Elena Vinogradov
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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27
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Samiotaki G, Karakatsani ME, Buch A, Papadopoulos S, Wu SY, Jambawalikar S, Konofagou EE. Pharmacokinetic analysis and drug delivery efficiency of the focused ultrasound-induced blood-brain barrier opening in non-human primates. Magn Reson Imaging 2016; 37:273-281. [PMID: 27916657 DOI: 10.1016/j.mri.2016.11.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 11/29/2016] [Accepted: 11/29/2016] [Indexed: 11/26/2022]
Abstract
PURPOSE Focused Ultrasound (FUS) in conjunction with systemically administered microbubbles has been shown to open the Blood-Brain Barrier (BBB) locally, non-invasively and reversibly in rodents and non-human primates (NHP), suggesting the immense potential of this technique. The objective of this study entailed the investigation of the physiologic changes in the brain following the FUS-induced BBB opening and their relationship with the underlying anatomy. MATERIALS AND METHODS Pharmacokinetic analysis was implemented in NHP's that received FUS at various acoustic pressures. Relaxivity mapping enabled the robust quantitative detection of the BBB opening as well as grey and white matter segmentation. Drug delivery efficiency was measured for pre-clinical validation of the technique. RESULTS Based on our results, the opening volume and the amount of the gadolinium delivered were found mostly contained in the grey matter, while FUS-induced permeability and drug concentration varied depending upon the underlying brain inhomogeneity, and increased with the acoustic pressure. CONCLUSIONS Overall, apart from the in vivo protocols for BBB analysis developed here, this study also suggests the important role that FUS can have in efficient drug delivery via localized and transient BBB opening.
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Affiliation(s)
- Gesthimani Samiotaki
- Department of Biomedical Engineering, Columbia University, Biomedical Engineering, 630 West 168th Street, Physicians and Surgeons 19-418, Manhattan, NY 10032, United States
| | - Maria Eleni Karakatsani
- Department of Biomedical Engineering, Columbia University, Biomedical Engineering, 630 West 168th Street, Physicians and Surgeons 19-418, Manhattan, NY 10032, United States.
| | - Amanda Buch
- Department of Biomedical Engineering, Columbia University, Biomedical Engineering, 630 West 168th Street, Physicians and Surgeons 19-418, Manhattan, NY 10032, United States
| | - Stephanos Papadopoulos
- Department of Biomedical Engineering, Columbia University, Biomedical Engineering, 630 West 168th Street, Physicians and Surgeons 19-418, Manhattan, NY 10032, United States
| | - Shih Ying Wu
- Department of Biomedical Engineering, Columbia University, Biomedical Engineering, 630 West 168th Street, Physicians and Surgeons 19-418, Manhattan, NY 10032, United States
| | - Sachin Jambawalikar
- Department of Radiology, Columbia University Medical Center, 177 Ft. Washington Ave. Milstein Bldg Room 3-124B, New York, NY 10032, United States
| | - Elisa E Konofagou
- Department of Biomedical Engineering, Columbia University, Biomedical Engineering, 630 West 168th Street, Physicians and Surgeons 19-418, Manhattan, NY 10032, United States; Department of Radiology, Columbia University Medical Center, 177 Ft. Washington Ave. Milstein Bldg Room 3-124B, New York, NY 10032, United States
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28
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Gras V, Farrher E, Grinberg F, Shah NJ. Diffusion-weighted DESS protocol optimization for simultaneous mapping of the mean diffusivity, proton density and relaxation times at 3 Tesla. Magn Reson Med 2016; 78:130-141. [PMID: 27476684 DOI: 10.1002/mrm.26353] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 06/16/2016] [Accepted: 07/01/2016] [Indexed: 01/09/2023]
Abstract
PURPOSE To design a general framework for the optimization of an MRI protocol based on the the diffusion-weighted dual-echo steady-state (DW-DESS) sequence, enabling quantitative and simultaneous mapping of proton density (PD), relaxation times T1 and T2 and diffusion coefficient D. METHODS A parameterization of the DW-DESS sequence minimizing the Cramér-Rao lower bound of each parameter estimate was proposed and tested in a phantom experiment. An extension of the protocol was implemented for brain imaging to return the rotationally invariant mean diffusivity (MD). RESULTS In an NiCl2 -doped agar gel phantom wherein T1/T2=920/65 ms, the parameter estimation errors were below 3% for PD and T1 and below 7% for T2 and D while the measured signal-to-noise ratio always exceeded 20. In the human brain, the in vivo parametric maps obtained were overall in reasonable agreement with gold standard measurements, despite a broadening of the distributions due to physiological motion. CONCLUSION Within the optimization framework presented here, DW-DESS images can be quantitatively interpreted to yield four intrinsic parameters of the tissue. Currently, the method is limited by the sensitivity of the DW-DESS sequence in terms of physiological motion. Magn Reson Med 78:130-141, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Vincent Gras
- Institute of Neuroscience and Medicine - 4, Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany.,UNIRS, Institut d'Imagerie Biomédicale, Neurospin, CEA Saclay, Gif-sur-Yvette, France
| | - Ezequiel Farrher
- Institute of Neuroscience and Medicine - 4, Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Farida Grinberg
- Institute of Neuroscience and Medicine - 4, Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany.,Department of Neurology, Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany
| | - N Jon Shah
- Institute of Neuroscience and Medicine - 4, Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany.,Department of Neurology, Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany
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29
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Assländer J, Glaser SJ, Hennig J. Pseudo Steady-State Free Precession for MR-Fingerprinting. Magn Reson Med 2016; 77:1151-1161. [PMID: 27079826 DOI: 10.1002/mrm.26202] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 02/14/2016] [Accepted: 02/15/2016] [Indexed: 11/10/2022]
Abstract
PURPOSE This article discusses the signal behavior in the case the flip angle in steady-state free precession sequences is continuously varied as suggested for MR-fingerprinting sequences. Flip angle variations prevent the establishment of a steady state and introduce instabilities regarding to magnetic field inhomogeneities and intravoxel dephasing. We show how a pseudo steady state can be achieved, which restores the spin echo nature of steady-state free precession. METHODS Based on geometrical considerations, relationships between the flip angle, repetition and echo time are derived that suffice to the establishment of a pseudo steady state. The theory is tested with Bloch simulations as well as phantom and in vivo experiments. RESULTS A typical steady-state free precession passband can be restored with the proposed conditions. The stability of the pseudo steady state is demonstrated by comparing the evolution of the signal of a single isochromat to one resulting from a spin ensemble. As confirmed by experiments, magnetization in a pseudo steady state can be described with fewer degrees of freedom compared to the original fingerprinting and the pseudo steady state results in more reliable parameter maps. CONCLUSION The proposed conditions restore the spin-echo-like signal behavior typical for steady-state free precession in fingerprinting sequences, making this approach more robust to B0 variations. Magn Reson Med 77:1151-1161, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jakob Assländer
- Department of Radiology-Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Steffen J Glaser
- Department of Chemistry, Technische Universität München, München, Germany
| | - Jürgen Hennig
- Department of Radiology-Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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30
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Delangre S, Vuong QL, Po C, Gallez B, Gossuin Y. Improvement of the Off-Resonance Saturation, an MRI sequence for positive contrast with SPM particles: Theoretical and experimental study. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 265:99-107. [PMID: 26894477 DOI: 10.1016/j.jmr.2016.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 02/02/2016] [Accepted: 02/04/2016] [Indexed: 06/05/2023]
Abstract
The SuperParaMagnetic particles (SPM particles) are used as contrast agents in MRI and produce negative contrast with conventional T2 or T2(∗)-weighted sequences. Unfortunately, the SPM particle detection on images acquired with such sequences is sometimes difficult because negative contrast can be created by artifacts such as air bubbles or calcification. To overcome this problem, new sequences as Off-Resonance Saturation (ORS) were developed to produce positive contrast with SPM particles. This work explores a new way to optimize the contrast generated by the ORS sequence by increasing the number of saturation pulses applied before the imaging sequence. This modified sequence is studied with numerical simulations and experiments on agarose gel phantoms. A theoretical model able to predict the contrast for different values of the sequence parameters is also developed. The results show that the contrast increases with the saturation pulses number with an optimal value of three saturation pulses in order to avoid artifacts and limit the Specific Absorption Rate (SAR) effect. The dependence of the contrast on the SPM particle concentration and sequence parameters is comparable to what was observed for the ORS sequence.
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Affiliation(s)
- S Delangre
- Biomedical Physics Unit, Université de Mons, Place du Parc 20, 7000 Mons, Belgium
| | - Q L Vuong
- Biomedical Physics Unit, Université de Mons, Place du Parc 20, 7000 Mons, Belgium
| | - C Po
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium
| | - B Gallez
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Y Gossuin
- Biomedical Physics Unit, Université de Mons, Place du Parc 20, 7000 Mons, Belgium.
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31
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Hoff MN, Andre JB, Xiang Q. Combined geometric and algebraic solutions for removal of bSSFP banding artifacts with performance comparisons. Magn Reson Med 2016; 77:644-654. [DOI: 10.1002/mrm.26150] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 12/22/2015] [Accepted: 01/14/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Michael N. Hoff
- Department of RadiologyUniversity of WashingtonSeattle Washington USA
| | - Jalal B. Andre
- Department of RadiologyUniversity of WashingtonSeattle Washington USA
| | - Qing‐San Xiang
- Department of Physics & AstronomyUniversity of British ColumbiaVancouver BC Canada
- Department of RadiologyUniversity of British ColumbiaVancouver BC Canada
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32
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Ciris PA, Cheng CC, Mei CS, Panych LP, Madore B. Dual-Pathway sequences for MR thermometry: When and where to use them. Magn Reson Med 2016; 77:1193-1200. [PMID: 26968318 DOI: 10.1002/mrm.26177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 01/21/2016] [Accepted: 01/31/2016] [Indexed: 01/23/2023]
Abstract
PURPOSE Dual-pathway sequences have been proposed to help improve the temperature-to-noise ratio (TNR) in MR thermometry. The present work establishes how much of an improvement these so-called "PSIF-FISP" sequences may bring in various organs and tissues. METHODS Simulations and TNR calculations were validated against analytical equations, phantom, abdomen, and brain scans. Relative TNRs for PSIF-FISP, as compared to a dual-FISP reference standard, were calculated for flip angle (FA) = 1 to 85 º and repetition time (TR) = 6 to 60 ms, for gray matter, white matter, cervix, endometrium, myometrium, prostate, kidney medulla and cortex, bone marrow, pancreas, spleen, muscle, and liver tissues. RESULTS PSIF-FISP was TNR superior in the kidney, pelvis, spleen, or gray matter at most tested TR and FA settings, and benefits increased at shorter TRs. PSIF-FISP was TNR superior in other tissues, e.g., liver, muscle, pancreas, for only short TR settings (20 ms or less). The TNR benefits of PSIF-FISP increased slightly with FA, and strongly with decreasing TR. Up to two- to three-fold reductions in TR with 20% TNR gains were achievable. In any given tissue, TNR performance is expected to further improve with heating, due to changes in relaxation rates. CONCLUSION Dual-pathway PSIF-FISP can improve TNR and acquisition speed over standard gradient-recalled echo sequences, but optimal acquisition parameters are tissue dependent. Magn Reson Med 77:1193-1200, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Pelin Aksit Ciris
- Department of Biomedical Engineering, Akdeniz University, Antalya, Turkey.,Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Cheng-Chieh Cheng
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Lawrence P Panych
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Bruno Madore
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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33
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Fast isotropic banding-free bSSFP imaging using 3D dynamically phase-cycled radial bSSFP (3D DYPR-SSFP). Z Med Phys 2016; 26:63-74. [DOI: 10.1016/j.zemedi.2015.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 04/23/2015] [Accepted: 05/10/2015] [Indexed: 11/21/2022]
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Jutras JD, Wachowicz K, De Zanche N. Analytical corrections of banding artifacts in driven equilibrium single pulse observation of T2 (DESPOT2). Magn Reson Med 2015; 76:1790-1804. [PMID: 26714609 DOI: 10.1002/mrm.26074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 11/05/2015] [Accepted: 11/15/2015] [Indexed: 11/10/2022]
Abstract
PURPOSE DESPOT2 is a single-component T2 mapping technique based on bSSFP imaging. It has seen limited application because of banding artifacts and magnetization transfer (MT) effects. In this work, acquisitions are optimized to minimize MT effects, while exact and approximate analytical equations enable automatic correction of banding artifacts within the T2 maps in mere seconds. THEORY AND METHODS The technique was verified on an agar phantom at 3 tesla. The T2 resulting from four different data combination techniques was compared with the T2 from CPMG. Two comparable DESPOT2 scan protocols (short vs. long TR/TRF ) designed to minimize MT effects, were tested both in the phantom and in vivo. A third protocol was tested in the brain of 8 volunteers and analytical correction schemes were compared with DESPOT2-FM. RESULTS The T2 measurements in agar agree with CPMG within ∼7% and in vivo results agree with values reported in the literature. The approximate analytical solutions provide increased robustness to hardware imperfections and higher T2 -to-noise ratio than the exact solutions. CONCLUSION New analytical solutions enable fast and accurate whole-brain T2 mapping from previously measured T1 and B1 maps, and bSSFP images with at least two phase offsets and two flip angles (=4 datasets, 8 min scan). Magn Reson Med 76:1790-1804, 2016. © 2015 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jean-David Jutras
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
| | - Keith Wachowicz
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Nicola De Zanche
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
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35
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Han S, Cho H. Temporal resolution improvement of calibration-free dynamic contrast-enhanced MRI with compressed sensing optimized turbo spin echo: The effects of replacing turbo factor with compressed sensing accelerations. J Magn Reson Imaging 2015; 44:138-47. [DOI: 10.1002/jmri.25136] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 12/03/2015] [Indexed: 11/09/2022] Open
Affiliation(s)
- SoHyun Han
- Department of Biomedical Engineering; Ulsan National Institute of Science and Technology; Ulsan South Korea
| | - HyungJoon Cho
- Department of Biomedical Engineering; Ulsan National Institute of Science and Technology; Ulsan South Korea
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Wang Y, Shao X, Martin T, Moeller S, Yacoub E, Wang DJJ. Phase-cycled simultaneous multislice balanced SSFP imaging with CAIPIRINHA for efficient banding reduction. Magn Reson Med 2015; 76:1764-1774. [PMID: 26667600 DOI: 10.1002/mrm.26076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/13/2015] [Accepted: 11/13/2015] [Indexed: 11/08/2022]
Abstract
PURPOSE To present a time-efficient technique for banding reduction in balanced steady-state free precession (bSSFP) imaging using phase-cycled simultaneous multislice (SMS) acquisition with CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration). THEORY The proposed technique exploits the inherent phase modulation of SMS imaging with CAIPIRINHA to acquire multiple phase-cycled images, which can be combined for efficient banding reduction within the same scan time of a single-band bSSFP scan. METHODS Bloch equation simulation, phantom and in vivo brain, abdominal and cardiac imaging experiments were performed on healthy volunteers at 3T using multi-channel head and body array coils with SMS acceleration factors of two to four. The performance of banding reduction was quantitatively evaluated based on the percent ripple of signal distribution and signal-to-noise ratio (SNR) efficiency in both phantom and human studies. RESULTS The banding artifact was successfully removed or suppressed using phase-cycled SMS bSSFP imaging across SMS factors of two to four. The performance of banding reduction improved with higher SMS factors along with increased SNR efficiency. CONCLUSION Phase-cycled SMS bSSFP with CAIPIRINHA is a promising technique for efficient band reduction in bSSFP without prolonged scan time. Further evaluation of this technique in clinical applications is warranted. Magn Reson Med 76:1764-1774, 2016. © 2015 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Yi Wang
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, California, USA
| | - Xingfeng Shao
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, California, USA
| | - Thomas Martin
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, California, USA
| | - Steen Moeller
- Center of Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Essa Yacoub
- Center of Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Danny J J Wang
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, California, USA
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Bär S, Weigel M, von Elverfeldt D, Hennig J, Leupold J. Intrinsic diffusion sensitivity of the balanced steady-state free precession (bSSFP) imaging sequence. NMR IN BIOMEDICINE 2015; 28:1383-1392. [PMID: 26346811 DOI: 10.1002/nbm.3380] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 07/02/2015] [Accepted: 07/22/2015] [Indexed: 06/05/2023]
Abstract
The purpose of this work was to analyze the intrinsic diffusion sensitivity of the balanced steady-state free precession (bSSFP) imaging sequence, meaning the observation of diffusion-induced attenuation of the bSSFP steady-state signal due to the imaging gradients. Although these diffusion effects are usually neglected for most clinical gradient systems, such strong gradient systems are employed for high resolution imaging of small animals or MR Microscopy. The impact on the bSSFP signal of the imaging gradients characterized by their b-values was analyzed with simulations and experiments at a 7T animal scanner using a gradient system with maximum gradient amplitude of approx. 700 mT/m. It was found that the readout gradients have a stronger impact on the attenuation than the phase encoding gradients. Also, as the PE gradients are varying with each repetition interval, the diffusion effects induce strong modulations of the bSSFP signal over the sequence repetition cycles depending on the phase encoding gradient table. It is shown that a signal gain can be obtained through a change of flip angle as a new optimal flip angle maximizing the signal can be defined. The dependency of the diffusion effects on relaxation times and b-values were explored with simulations. The attenuation increases with T2. In conclusion, diffusion attenuation of the bSSFP signal becomes significant for high resolution imaging voxel size (roughly < 100 μm) of long T2 substances.
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Affiliation(s)
- Sébastien Bär
- University Medical Center Freiburg, Department of Radiology, Medical Physics, Freiburg, Germany
| | - Matthias Weigel
- University Hospital Basel, Clinics of Radiology and Nuclear Medicine, Radiological Physics, Basel, Switzerland
- University of Basel, Department of Biomedical Engineering, Basel, Switzerland
| | - Dominik von Elverfeldt
- University Medical Center Freiburg, Department of Radiology, Medical Physics, Freiburg, Germany
| | - Jürgen Hennig
- University Medical Center Freiburg, Department of Radiology, Medical Physics, Freiburg, Germany
| | - Jochen Leupold
- University Medical Center Freiburg, Department of Radiology, Medical Physics, Freiburg, Germany
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Xiang QS, Hoff MN. Banding artifact removal for bSSFP imaging with an elliptical signal model. Magn Reson Med 2015; 71:927-33. [PMID: 24436006 DOI: 10.1002/mrm.25098] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
PURPOSE Balanced steady-state free precession (bSSFP) imaging has broad clinical applications by virtue of its high time efficiency and desirable contrast. Unfortunately, banding artifact is often seen as a result of signal modulation due to B0 inhomogeneity. This study aims to develop an effective method for banding artifact suppression. METHODS bSSFP is analyzed with an elliptical signal model. A simple analytical "Geometric-Solution" (GS) is presented to demodulate the signal from B0 inhomogeneity dependence with phase-cycled bSSFP data from both a computer simulation and experiments using phantom and human subjects. RESULTS The proposed algorithm is able to remove banding artifacts completely. It also compares favorably with the complex sum (CS), which is considered one of the more efficient methods for banding artifact correction. CONCLUSION Using an elliptical signal model, an analytical solution to the bSSFP banding problem has been found and demonstrated with simulation as well as phantom and in vivo experiments.
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Affiliation(s)
- Qing-San Xiang
- Department of Radiology, University of British Columbia, Vancouver, Canada; Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
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Lee H, Jeong WC, Kim HJ, Woo EJ, Park J. Alternating steady state free precession for estimation of current-induced magnetic flux density: A feasibility study. Magn Reson Med 2015; 75:2009-19. [DOI: 10.1002/mrm.25813] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/19/2015] [Accepted: 05/21/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Hyunyeol Lee
- Center for Neuroscience Imaging Research; Institute for Basic Science (IBS), Sungkyunkwan University; Suwon Republic of Korea
| | - Woo Chul Jeong
- Department of Biomedical Engineering; Kyung Hee University; Yongin Republic of Korea
| | - Hyung Joong Kim
- Department of Biomedical Engineering; Kyung Hee University; Yongin Republic of Korea
| | - Eung Je Woo
- Department of Biomedical Engineering; Kyung Hee University; Yongin Republic of Korea
| | - Jaeseok Park
- Department of Global Biomedical Engineering; Biomedical Imaging and Engineering Lab., Sungkyunkwan University; Suwon Republic of Korea
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Park SH, Han PK, Choi SH. Physiological and Functional Magnetic Resonance Imaging Using Balanced Steady-state Free Precession. Korean J Radiol 2015; 16:550-9. [PMID: 25995684 PMCID: PMC4435985 DOI: 10.3348/kjr.2015.16.3.550] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 02/05/2015] [Indexed: 12/01/2022] Open
Abstract
Balanced steady-state free precession (bSSFP) is a highly efficient pulse sequence that is known to provide the highest signal-to-noise ratio per unit time. Recently, bSSFP is getting increasingly popular in both the research and clinical communities. This review will be focusing on the application of the bSSFP technique in the context of probing the physiological and functional information. In the first part of this review, the basic principles of bSSFP are briefly covered. Afterwards, recent developments related to the application of bSSFP, in terms of physiological and functional imaging, are introduced and reviewed. Despite its long development history, bSSFP is still a promising technique that has many potential benefits for obtaining high-resolution physiological and functional images.
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Affiliation(s)
- Sung-Hong Park
- Magnetic Resonance Imaging Lab, Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Paul Kyu Han
- Magnetic Resonance Imaging Lab, Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Seung Hong Choi
- Department of Radiology, Seoul National University College of Medicine, Seoul 110-744, Korea
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Henze Bancroft LC, Strigel RM, Hernando D, Johnson KM, Kelcz F, Kijowski R, Block WF. Utilization of a balanced steady state free precession signal model for improved fat/water decomposition. Magn Reson Med 2015; 75:1269-77. [PMID: 25946145 DOI: 10.1002/mrm.25728] [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: 10/14/2014] [Revised: 03/10/2015] [Accepted: 03/20/2015] [Indexed: 12/21/2022]
Abstract
PURPOSE Chemical shift based fat/water decomposition methods such as IDEAL are frequently used in challenging imaging environments with large B0 inhomogeneity. However, they do not account for the signal modulations introduced by a balanced steady state free precession (bSSFP) acquisition. Here we demonstrate improved performance when the bSSFP frequency response is properly incorporated into the multipeak spectral fat model used in the decomposition process. THEORY AND METHODS Balanced SSFP allows for rapid imaging but also introduces a characteristic frequency response featuring periodic nulls and pass bands. Fat spectral components in adjacent pass bands will experience bulk phase offsets and magnitude modulations that change the expected constructive and destructive interference between the fat spectral components. A bSSFP signal model was incorporated into the fat/water decomposition process and used to generate images of a fat phantom, and bilateral breast and knee images in four normal volunteers at 1.5 Tesla. RESULTS Incorporation of the bSSFP signal model into the decomposition process improved the performance of the fat/water decomposition. CONCLUSION Incorporation of this model allows rapid bSSFP imaging sequences to use robust fat/water decomposition methods such as IDEAL. While only one set of imaging parameters were presented, the method is compatible with any field strength or repetition time.
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Affiliation(s)
- Leah C Henze Bancroft
- University of Wisconsin-Madison, Department of Medical Physics, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA
| | - Roberta M Strigel
- University of Wisconsin-Madison, Department of Medical Physics, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA.,University of Wisconsin School of Medicine and Public health, Department of Radiology, Madison, Wisconsin, USA.,University of Wisconsin Carbone Cancer Center, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA
| | - Diego Hernando
- University of Wisconsin-Madison, Department of Radiology, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA
| | - Kevin M Johnson
- University of Wisconsin-Madison, Department of Medical Physics, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA
| | - Frederick Kelcz
- University of Wisconsin School of Medicine and Public health, Department of Radiology, Madison, Wisconsin, USA
| | - Richard Kijowski
- University of Wisconsin School of Medicine and Public health, Department of Radiology, Madison, Wisconsin, USA
| | - Walter F Block
- University of Wisconsin-Madison, Department of Medical Physics, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA.,University of Wisconsin-Madison, Department of Radiology, Wisconsin Institutes for Medical Research, Madison, Wisconsin, USA.,University of Wisconsin-Madison, Department of Biomedical Engineering, Wisconsin Institutes for Medical Research, Madison, Wisconsin
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Delangre S, Vuong QL, Henrard D, Po C, Gallez B, Gossuin Y. Bottom-up study of the MRI positive contrast created by the Off-Resonance Saturation sequence. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 254:98-109. [PMID: 25863894 DOI: 10.1016/j.jmr.2015.02.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 02/12/2015] [Accepted: 02/24/2015] [Indexed: 06/04/2023]
Abstract
Superparamagnetic iron oxide nanoparticles (SPM particles) are used in MRI to highlight regions such as tumors through negative contrast. Unfortunately, sources as air bubbles or tissues interfaces also lead to negative contrast, which complicates the image interpretation. New MRI sequences creating positive contrast in the particle surrounding, such as the Off-Resonance Saturation sequence (ORS), have thus been developed. However, a theoretical study of the ORS sequence is still lacking, which hampers the optimization of this sequence. For this reason, this work provides a self-consistent analytical expression able to predict the dependence of the contrast on the sequence parameters and the SPM particles properties. This expression was validated by numerical simulations and experiments on agarose gel phantoms on a 11.7 T scanner system. It provides a fundamental understanding of the mechanisms leading to positive contrast, which could allow the improvement of the sequence for future in vivo applications. The influence of the SPM particle relaxivities, the SPM particle concentration, the echo time and the saturation pulse parameters on the contrast were investigated. The best contrast was achieved with SPM particles possessing the smallest transverse relaxivity, an optimal particle concentration and for low echo times.
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Affiliation(s)
- S Delangre
- Biomedical Physics Department, Université de Mons, Place du Parc 20, 7000 Mons, Belgium
| | - Q L Vuong
- Biomedical Physics Department, Université de Mons, Place du Parc 20, 7000 Mons, Belgium
| | - D Henrard
- Biomedical Physics Department, Université de Mons, Place du Parc 20, 7000 Mons, Belgium
| | - C Po
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium
| | - B Gallez
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Y Gossuin
- Biomedical Physics Department, Université de Mons, Place du Parc 20, 7000 Mons, Belgium.
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Delangre S, Vuong QL, Henrard D, Magat J, Po C, Gallez B, Gossuin Y. Theoretical and experimental study of ON-Resonance Saturation, an MRI sequence for positive contrast with superparamagnetic nanoparticles. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 252:151-162. [PMID: 25700117 DOI: 10.1016/j.jmr.2015.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 01/13/2015] [Accepted: 01/14/2015] [Indexed: 06/04/2023]
Abstract
Superparamagnetic iron oxide nanoparticles (SPM particles) are widely used in MRI as negative contrast agents. Their detection is sometimes difficult because negative contrast can be caused by different artifacts. To overcome this problem, MRI protocols achieving positive contrast specific to SPM particles were developed such as the ON-Resonance Saturation (ONRS) sequence. The aim of the present work is to achieve a bottom-up study of the ONRS sequence by an understanding of the physical mechanisms leading to positive contrast. A complete theoretical modeling, a novel numerical simulation approach and experiments on agarose gel phantoms on a 11.7 T MRI system were carried out for this purpose. The influence of the particle properties and concentration - as well as the effect of the sequence parameters on the contrast - were investigated. It was observed that theory and experiments were in strong agreement. The tools developed in this work allowed to predict the parameters leading to the maximum contrast. For example, particles presenting a low transverse relaxivity can provide an interesting positive contrast after optimization of their concentration in the sample.
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Affiliation(s)
- S Delangre
- Biomedical Physics Department, University of Mons, 24, Avenue du Champ de Mars, 7000 Mons, Belgium
| | - Q L Vuong
- Biomedical Physics Department, University of Mons, 24, Avenue du Champ de Mars, 7000 Mons, Belgium
| | - D Henrard
- Biomedical Physics Department, University of Mons, 24, Avenue du Champ de Mars, 7000 Mons, Belgium
| | - J Magat
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, 73, Avenue E. Mounier, 1200 Brussels, Belgium
| | - C Po
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, 73, Avenue E. Mounier, 1200 Brussels, Belgium
| | - B Gallez
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université Catholique de Louvain, 73, Avenue E. Mounier, 1200 Brussels, Belgium
| | - Y Gossuin
- Biomedical Physics Department, University of Mons, 24, Avenue du Champ de Mars, 7000 Mons, Belgium.
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Foxley S, Jbabdi S, Clare S, Lam W, Ansorge O, Douaud G, Miller K. Improving diffusion-weighted imaging of post-mortem human brains: SSFP at 7 T. Neuroimage 2014; 102 Pt 2:579-89. [PMID: 25128709 PMCID: PMC4229505 DOI: 10.1016/j.neuroimage.2014.08.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 07/17/2014] [Accepted: 08/06/2014] [Indexed: 11/23/2022] Open
Abstract
Post-mortem diffusion imaging of whole, human brains has potential to provide data for validation or high-resolution anatomical investigations. Previous work has demonstrated improvements in data acquired with diffusion-weighted steady-state free precession (DW-SSFP) compared with conventional diffusion-weighted spin echo at 3T. This is due to the ability of DW-SSFP to overcome signal-to-noise and diffusion contrast losses brought about by tissue fixation related decreases in T2 and ADC. In this work, data of four post-mortem human brains were acquired at 3T and 7 T, using DW-SSFP with similar effective b-values (b(eff)~5150 s/mm(2)) for inter-field strength comparisons; in addition, DW-SSFP data were acquired at 7 T with higher b(eff) (~8550 s/mm(2)) for intra-field strength comparisons. Results demonstrate that both datasets acquired at 7 T had higher SNR and diffusion contrast than data acquired at 3T, and data acquired at higher b(eff) had improved diffusion contrast than at lower b(eff) at 7 T. These results translate to improved estimates of secondary fiber orientations leading to higher fidelity tractography results compared with data acquired at 3T. Specifically, tractography streamlines of cortical projections originating from the corpus callosum, corticospinal tract, and superior longitudinal fasciculus were more successful at crossing the centrum semiovale and projected closer to the cortex. Results suggest that DW-SSFP at 7 T is a preferential method for acquiring diffusion-weighted data of post-mortem human brain, specifically where the primary region of interest involves crossing white matter tracts.
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Affiliation(s)
- Sean Foxley
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Saad Jbabdi
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Stuart Clare
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Wilfred Lam
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Olaf Ansorge
- Division of Clinical Neurology, University of Oxford, Oxford, UK
| | - Gwenaelle Douaud
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Karla Miller
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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Quist B, Hargreaves BA, Daniel BL, Saranathan M. Balanced SSFP Dixon imaging with banding-artifact reduction at 3 Tesla. Magn Reson Med 2014; 74:706-15. [PMID: 25227766 DOI: 10.1002/mrm.25449] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 01/10/2023]
Abstract
PURPOSE To develop a three-dimensional (3D) balanced steady-state free-precession (bSSFP) two-point Dixon method with banding-artifact suppression to offer robust high-resolution 3D bright-fluid imaging. METHODS A complex sum reconstruction that combines phase-cycled bSSFP images acquired at specific echo times for robust fat/water separation without banding was investigated and compared with a magnitude-based method. Bloch simulations using both single-peak and multiple-peak fat models were performed to predict the performance of these methods for a wide range of echo times and repetition times. The quality and degree of fat/water separation was evaluated in both simulations and using in vivo imaging. RESULTS Simulations predicted that both effective banding-artifact suppression and substantial improvements in fat/water separation are possible at echo times that are different from conventional echo times, enabling improved spatial resolution. Comparisons between various echo times and repetition times in vivo validated the improved fat/water separation and effective banding-artifact removal predicted by the simulations. CONCLUSION The proposed complex sum Dixon 3D bSSFP method is able to effectively separate fat and water at different sets of echo times, while removing banding-artifacts, providing a fast, high-resolution, T2 -like sequence without blurring.
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Affiliation(s)
- Brady Quist
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | | | - Bruce L Daniel
- Department of Radiology, Stanford University, Stanford, California, USA
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Soleimanifard S, Stuber M, Hays AG, Weiss RG, Schär M. Robust volume-targeted balanced steady-state free-precession coronary magnetic resonance angiography in a breathhold at 3.0 Tesla: a reproducibility study. J Cardiovasc Magn Reson 2014; 16:27. [PMID: 24758168 PMCID: PMC4006454 DOI: 10.1186/1532-429x-16-27] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 03/28/2014] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Transient balanced steady-state free-precession (bSSFP) has shown substantial promise for noninvasive assessment of coronary arteries but its utilization at 3.0 T and above has been hampered by susceptibility to field inhomogeneities that degrade image quality. The purpose of this work was to refine, implement, and test a robust, practical single-breathhold bSSFP coronary MRA sequence at 3.0 T and to test the reproducibility of the technique. METHODS A 3D, volume-targeted, high-resolution bSSFP sequence was implemented. Localized image-based shimming was performed to minimize inhomogeneities of both the static magnetic field and the radio frequency excitation field. Fifteen healthy volunteers and three patients with coronary artery disease underwent examination with the bSSFP sequence (scan time = 20.5 ± 2.0 seconds), and acquisitions were repeated in nine subjects. The images were quantitatively analyzed using a semi-automated software tool, and the repeatability and reproducibility of measurements were determined using regression analysis and intra-class correlation coefficient (ICC), in a blinded manner. RESULTS The 3D bSSFP sequence provided uniform, high-quality depiction of coronary arteries (n = 20). The average visible vessel length of 100.5 ± 6.3 mm and sharpness of 55 ± 2% compared favorably with earlier reported navigator-gated bSSFP and gradient echo sequences at 3.0 T. Length measurements demonstrated a highly statistically significant degree of inter-observer (r = 0.994, ICC = 0.993), intra-observer (r = 0.894, ICC = 0.896), and inter-scan concordance (r = 0.980, ICC = 0.974). Furthermore, ICC values demonstrated excellent intra-observer, inter-observer, and inter-scan agreement for vessel diameter measurements (ICC = 0.987, 0.976, and 0.961, respectively), and vessel sharpness values (ICC = 0.989, 0.938, and 0.904, respectively). CONCLUSIONS The 3D bSSFP acquisition, using a state-of-the-art MR scanner equipped with recently available technologies such as multi-transmit, 32-channel cardiac coil, and localized B0 and B1+ shimming, allows accelerated and reproducible multi-segment assessment of the major coronary arteries at 3.0 T in a single breathhold. This rapid sequence may be especially useful for functional imaging of the coronaries where the acquisition time is limited by the stress duration and in cases where low navigator-gating efficiency prohibits acquisition of a free breathing scan in a reasonable time period.
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Affiliation(s)
- Sahar Soleimanifard
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Matthias Stuber
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA
- Department of Radiology, Centre Hospitalier Universitaire Vaudois, Center for Biomedical Imaging (CIBM) and University of Lausanne, Lausanne, Switzerland
- Russell H. Morgan Department of Radiology and Radiological Science, Division of Magnetic Resonance Research, Johns Hopkins University, Baltimore, MD, USA
| | - Allison G Hays
- Russell H. Morgan Department of Radiology and Radiological Science, Division of Magnetic Resonance Research, Johns Hopkins University, Baltimore, MD, USA
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD, USA
| | - Robert G Weiss
- Russell H. Morgan Department of Radiology and Radiological Science, Division of Magnetic Resonance Research, Johns Hopkins University, Baltimore, MD, USA
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD, USA
| | - Michael Schär
- Russell H. Morgan Department of Radiology and Radiological Science, Division of Magnetic Resonance Research, Johns Hopkins University, Baltimore, MD, USA
- Philips Healthcare, Cleveland, OH, USA
- Barrow Neurological Institute, Keller Center for Imaging Innovation, 350 W. Thomas Rd, Phoenix, AZ 85013, USA
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Extended phase graphs: Dephasing, RF pulses, and echoes - pure and simple. J Magn Reson Imaging 2014; 41:266-95. [DOI: 10.1002/jmri.24619] [Citation(s) in RCA: 239] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 02/10/2014] [Accepted: 02/19/2014] [Indexed: 11/07/2022] Open
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Mulkern R, Haker S, Mamata H, Lee E, Mitsouras D, Oshio K, Balasubramanian M, Hatabu H. Lung Parenchymal Signal Intensity in MRI: A Technical Review with Educational Aspirations Regarding Reversible Versus Irreversible Transverse Relaxation Effects in Common Pulse Sequences. CONCEPTS IN MAGNETIC RESONANCE. PART A, BRIDGING EDUCATION AND RESEARCH 2014; 43A:29-53. [PMID: 25228852 PMCID: PMC4163152 DOI: 10.1002/cmr.a.21297] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Lung parenchyma is challenging to image with proton MRI. The large air space results in ~l/5th as many signal-generating protons compared to other organs. Air/tissue magnetic susceptibility differences lead to strong magnetic field gradients throughout the lungs and to broad frequency distributions, much broader than within other organs. Such distributions have been the subject of experimental and theoretical analyses which may reveal aspects of lung microarchitecture useful for diagnosis. Their most immediate relevance to current imaging practice is to cause rapid signal decays, commonly discussed in terms of short T2* values of 1 ms or lower at typical imaging field strengths. Herein we provide a brief review of previous studies describing and interpreting proton lung spectra. We then link these broad frequency distributions to rapid signal decays, though not necessarily the exponential decays generally used to define T2* values. We examine how these decays influence observed signal intensities and spatial mapping features associated with the most prominent torso imaging sequences, including spoiled gradient and spin echo sequences. Effects of imperfect refocusing pulses on the multiple echo signal decays in single shot fast spin echo (SSFSE) sequences and effects of broad frequency distributions on balanced steady state free precession (bSSFP) sequence signal intensities are also provided. The theoretical analyses are based on the concept of explicitly separating the effects of reversible and irreversible transverse relaxation processes, thus providing a somewhat novel and more general framework from which to estimate lung signal intensity behavior in modern imaging practice.
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Affiliation(s)
| | - Steven Haker
- Brigham and Women's Hospital, Radiology, Boston, MA, 02115
| | - Hatsuho Mamata
- Brigham and Women's Hospital, Radiology, Boston, MA, 02115
| | - Edward Lee
- Children's Hospital, Radiology, Boston, MA, 02115
| | | | - Koichi Oshio
- Brigham and Women's Hospital, Radiology, Boston, MA, 02115
| | | | - Hiroto Hatabu
- Brigham and Women's Hospital, Radiology, Boston, MA, 02115
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Effects of RF profile on precision of quantitative T2 mapping using dual-echo steady-state acquisition. Magn Reson Imaging 2013; 32:102-6. [PMID: 24211187 DOI: 10.1016/j.mri.2013.10.002] [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: 04/02/2013] [Revised: 08/26/2013] [Accepted: 10/03/2013] [Indexed: 11/22/2022]
Abstract
The dual echo steady-state (DESS) sequence has been shown successful in achieving fast T2 mapping with good precision. Under-estimation of T2, however, becomes increasingly prominent as the flip angle decreases. In 3D DESS imaging, therefore, the derived T2 values would become a function of the slice location in the presence of non-ideal slice profile of the excitation RF pulse. Furthermore, the pattern of slice-dependent variation in T2 estimates is dependent on the RF pulse waveform. Multi-slice 2D DESS imaging provides better inter-slice consistency, but the signal intensity is subject to integrated effects of within-slice distribution of the actual flip angle. Consequently, T2 measured using 2D DESS is prone to inaccuracy even at the designated flip angle of 90°. In this study, both phantom and human experiments demonstrate the above phenomena in good agreement with model prediction.
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Björk M, Ingle RR, Gudmundson E, Stoica P, Nishimura DG, Barral JK. Parameter estimation approach to banding artifact reduction in balanced steady-state free precession. Magn Reson Med 2013; 72:880-92. [PMID: 24166591 DOI: 10.1002/mrm.24986] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 08/13/2013] [Accepted: 09/02/2013] [Indexed: 11/11/2022]
Abstract
PURPOSE The balanced steady-state free precession (bSSFP) pulse sequence has shown to be of great interest due to its high signal-to-noise ratio efficiency. However, bSSFP images often suffer from banding artifacts due to off-resonance effects, which we aim to minimize in this article. METHODS We present a general and fast two-step algorithm for 1) estimating the unknowns in the bSSFP signal model from multiple phase-cycled acquisitions, and 2) reconstructing band-free images. The first step, linearization for off-resonance estimation (LORE), solves the nonlinear problem approximately by a robust linear approach. The second step applies a Gauss-Newton algorithm, initialized by LORE, to minimize the nonlinear least squares criterion. We name the full algorithm LORE-GN. RESULTS We derive the Cramér-Rao bound, a theoretical lower bound of the variance for any unbiased estimator, and show that LORE-GN is statistically efficient. Furthermore, we show that simultaneous estimation of T1 and T2 from phase-cycled bSSFP is difficult, since the Cramér-Rao bound is high at common signal-to-noise ratio. Using simulated, phantom, and in vivo data, we illustrate the band-reduction capabilities of LORE-GN compared to other techniques, such as sum-of-squares. CONCLUSION Using LORE-GN we can successfully minimize banding artifacts in bSSFP.
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Affiliation(s)
- Marcus Björk
- Department of Information Technology, Uppsala University, Uppsala, Sweden
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