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Tian Y, Lim Y, Zhao Z, Byrd D, Narayanan S, Nayak KS. Aliasing artifact reduction in spiral real-time MRI. Magn Reson Med 2021; 86:916-925. [PMID: 33728700 DOI: 10.1002/mrm.28746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 01/09/2021] [Accepted: 02/02/2021] [Indexed: 12/17/2022]
Abstract
PURPOSE To mitigate a common artifact in spiral real-time MRI, caused by aliasing of signal outside the desired FOV. This artifact frequently occurs in midsagittal speech real-time MRI. METHODS Simulations were performed to determine the likely origin of the artifact. Two methods to mitigate the artifact are proposed. The first approach, denoted as "large FOV" (LF), keeps an FOV that is large enough to include the artifact signal source during reconstruction. The second approach, denoted as "estimation-subtraction" (ES), estimates the artifact signal source before subtracting a synthetic signal representing that source in multicoil k-space raw data. Twenty-five midsagittal speech-production real-time MRI data sets were used to evaluate both of the proposed methods. Reconstructions without and with corrections were evaluated by two expert readers using a 5-level Likert scale assessing artifact severity. Reconstruction time was also compared. RESULTS The origin of the artifact was found to be a combination of gradient nonlinearity and imperfect anti-aliasing in spiral sampling. The LF and ES methods were both able to substantially reduce the artifact, with an averaged qualitative score improvement of 1.25 and 1.35 Likert levels for LF correction and ES correction, respectively. Average reconstruction time without correction, with LF correction, and with ES correction were 160.69 ± 1.56, 526.43 ± 5.17, and 171.47 ± 1.71 ms/frame. CONCLUSION Both proposed methods were able to reduce the spiral aliasing artifacts, with the ES-reduction method being more effective and more time efficient.
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Affiliation(s)
- Ye Tian
- Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Yongwan Lim
- Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Ziwei Zhao
- Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Dani Byrd
- Department of Linguistics, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA
| | - Shrikanth Narayanan
- Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA.,Department of Linguistics, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA
| | - Krishna S Nayak
- Ming Hsieh Department of Electrical and Computer Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
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Kogan F, Levine E, Chaudhari AS, Monu UD, Epperson K, Oei EHG, Gold GE, Hargreaves BA. Simultaneous bilateral-knee MR imaging. Magn Reson Med 2017; 80:529-537. [PMID: 29250856 DOI: 10.1002/mrm.27045] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 11/19/2017] [Accepted: 11/21/2017] [Indexed: 12/23/2022]
Abstract
PURPOSE To demonstrate and evaluate the scan time and quantitative accuracy of simultaneous bilateral-knee imaging compared with single-knee acquisitions. METHODS Hardware modifications and safety testing was performed to enable MR imaging with two 16-channel flexible coil arrays. Noise covariance and sensitivity-encoding g-factor maps for the dual-coil-array configuration were computed to evaluate coil cross-talk and noise amplification. Ten healthy volunteers were imaged on a 3T MRI scanner with both dual-coil-array bilateral-knee and single-coil-array single-knee configurations. Two experienced musculoskeletal radiologists compared the relative image quality between blinded image pairs acquired with each configuration. Differences in T2 relaxation time measurements between dual-coil-array and single-coil-array acquisitions were compared with the standard repeatability of single-coil-array measurements using a Bland-Altman analysis. RESULTS The mean g-factors for the dual-coil-array configuration were low for accelerations up to 6 in the right-left direction, and minimal cross-talk was observed between the two coil arrays. Image quality ratings of various joint tissues showed no difference in 89% (95% confidence interval: 85-93%) of rated image pairs, with only small differences ("slightly better" or "slightly worse") in image quality observed. The T2 relaxation time measurements between the dual-coil-array configuration and the single-coil configuration showed similar limits of agreement and concordance correlation coefficients (limits of agreement: -0.93 to 1.99 ms; CCC: 0.97 (95% confidence interval: 0.96-0.98)), to the repeatability of single-coil-array measurements (limits of agreement: -2.07 to 1.96 ms; CCC: 0.97 (95% confidence interval: 0.95-0.98)). CONCLUSION A bilateral coil-array setup can image both knees simultaneously in similar scan times as conventional unilateral knee scans, with comparable image quality and quantitative accuracy. This has the potential to improve the value of MRI knee evaluations. Magn Reson Med 80:529-537, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Feliks Kogan
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Evan Levine
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Akshay S Chaudhari
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Bioengineering, Stanford University, Stanford, California, USA
| | - Uchechukwuka D Monu
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Kevin Epperson
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Edwin H G Oei
- Department of Radiology & Nuclear Medicine, Erasmus MC, University Medical Center, Rotterdam, Netherlands
| | - Garry E Gold
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Bioengineering, Stanford University, Stanford, California, USA.,Department of Orthopedic Surgery, Stanford University, Stanford, California, USA
| | - Brian A Hargreaves
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Electrical Engineering, Stanford University, Stanford, California, USA.,Department of Bioengineering, Stanford University, Stanford, California, USA
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Pang Y, Wu B, Wang C, Vigneron DB, Zhang X. Numerical Analysis of Human Sample Effect on RF Penetration and Liver MR Imaging at Ultrahigh Field. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2011; 39B:206-216. [PMID: 22337345 PMCID: PMC3277816 DOI: 10.1002/cmr.b.20209] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Magnetic resonance imaging (MRI) can provide clinically-valuable images for hepatic diseases and has become one of the most promising noninvasive methods in evaluating liver lesions. To facilitate the ultrahigh field human liver MRI, in this work, the RF penetration behavior in the conductive and high dielectric human body at the ultrahigh field of 7 Tesla (7T) is investigated and evaluated using the finite-difference time-domain numerical analysis. The study shows that in brain imaging at the ultrahigh field of 7T, the "dielectric resonance" effect dominates among other factors, resulting in improved B(1) penetration; while in liver imaging, due to its irregular geometry of the liver, the "dielectric resonance" effect is not readily to be established, leading to a reduced B(1) penetration or limited image coverage comparing to that in the brain. Therefore, it is necessary to build a large size coil to have deeper penetration to image human liver although the coil design may become more challenging due to the required high frequency. Based on this study, a bisected microstrip coil operating at 300 MHz range is designed and constructed. Three-dimensional in vivo liver images in axial, sagittal and coronal orientations are then acquired from healthy volunteers using this dedicated RF coil on a 7T whole body MR scanner.
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Affiliation(s)
- Yong Pang
- Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA
| | - Bing Wu
- Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA
| | - Chunsheng Wang
- Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA
| | - Daniel B. Vigneron
- Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA
- UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA
| | - Xiaoliang Zhang
- Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA
- UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA
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Cukur T, Santos JM, Pauly JM, Nishimura DG. Variable-density parallel imaging with partially localized coil sensitivities. IEEE TRANSACTIONS ON MEDICAL IMAGING 2010; 29:1173-1181. [PMID: 20236876 PMCID: PMC3155390 DOI: 10.1109/tmi.2010.2042805] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Partially parallel imaging with localized sensitivities is a fast parallel image reconstruction method for both Cartesian and non-Cartesian trajectories, but suffers from aliasing artifacts when there are deviations from the assumption of perfect localization. Such reconstructions would normally crop the individual coil images to remove the artifacts prior to combination. However, the sampling densities in variable-density k-space trajectories support different field-of-views for separate regions in k -space. In fact, the higher sampling density of low frequencies can be used to reconstruct a bigger field-of-view without introducing aliasing artifacts and the resulting image signal-to-noise ratio (SNR) can be improved. A novel, fast variable-density parallel imaging method is presented, which reconstructs different field-of-views from separate frequencies according to the local sampling density in k-space. Aliasing-suppressed images can be produced with high SNR-efficiency without the need for accurate estimation of coil sensitivities and complex or iterative computations.
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Affiliation(s)
- Tolga Cukur
- Information Systems Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
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Barmet C, De Zanche N, Pruessmann KP. Spatiotemporal magnetic field monitoring for MR. Magn Reson Med 2008; 60:187-97. [PMID: 18581361 DOI: 10.1002/mrm.21603] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
MR experiments frequently rely on signal encoding by the application of magnetic fields that vary in both space and time. The accurate interpretation of the resulting signals often requires knowledge of the exact spatiotemporal field evolution during the experiment. To better fulfill this need, a new approach is presented that enables measuring the field evolution concurrently with any MR sequence. Miniature NMR probes are used to monitor the MR phase evolution around the object under investigation. Based on these data, a global phase model is calculated that can then be used as a basis for processing the actual image or spectroscopic data. The new method is demonstrated by MRI of a phantom, using spin-warp, spiral, and EPI trajectories. Throughout, the monitoring results enabled highly accurate image reconstruction, even in the presence of massive gradient imperfections.
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Affiliation(s)
- Christoph Barmet
- Institute for Biomedical Engineering of the University, ETH Zurich, Department of Information Technology and Electrical Engineering, Gloriastrasse 35, Zurich, Switzerland
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Meyer CH, Hu P. Spiral parallel magnetic resonance imaging. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2008; 2006:369-71. [PMID: 17946823 DOI: 10.1109/iembs.2006.259758] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Spiral k-space scanning is a rapid magnetic resonance imaging (MRI) technique that can provide an order of magnitude reduction in scan time compared to conventional spin warp techniques. Parallel imaging is another method for reducing scan time that exploits spatially varying radiofrequency (RF) coil sensitivities to reduce the amount of data required to reconstruct an image. Combining spiral scanning with parallel imaging provide a scan time reduction factor that is the product of the reduction factors for each of the techniques and thus can permit very rapid imaging. Image reconstruction for spiral parallel MRI is more involved than for spin warp parallel MRI and is an area of active research. Two techniques for performing this image reconstruction are PILS, a simple image-domain method that relies on localized coil sensitivities, and BOSCO, a method that is based on successive convolution operations in k-space.
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Affiliation(s)
- Craig H Meyer
- Dept. of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
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Kressler B, Spincemaille P, Nguyen TD, Cheng L, Xi Hai Z, Prince MR, Wang Y. Three-dimensional cine imaging using variable-density spiral trajectories and SSFP with application to coronary artery angiography. Magn Reson Med 2007; 58:535-43. [PMID: 17763360 DOI: 10.1002/mrm.21365] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A single breath-hold 3D cardiac phase resolved steady-state free precession (SSFP) sequence was developed, allowing 3D visualization of the moving coronary arteries. A 3D stack of spirals was acquired continuously throughout the cardiac cycle, and a sliding window reconstruction was used to achieve high temporal resolution. A coil specific field of view reconstruction technique was combined with Parallel Imaging with Localized Sensitivities (PILS) to allow acquisition of a reduced field of view. A view ordering incorporating fat suppression was employed to allow use of sliding window reconstruction. The technique was evaluated on healthy volunteers (n=8), yielding images with 102 ms temporal resolution and 1.35 mm in-plane resolution, and reasonable visualization of the left and right coronary arteries was achieved.
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Affiliation(s)
- Bryan Kressler
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA, and Department of Radiology, Chinese PLA General Hospital, Beijing, China
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He W, Qin X, Jiejing R, Gengying L. Four-channel magnetic resonance imaging receiver using frequency domain multiplexing. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:015102. [PMID: 17503941 DOI: 10.1063/1.2424426] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
An alternative technique that uses frequency domain multiplexing to acquire phased array magnetic resonance images is discussed in detail. The proposed method has advantages over traditional independent receiver chains in that it utilizes an analog-to-digital converter and a single-chip multicarrier receiver with high performance to reduce the size and cost of the phased array receiver system. A practical four-channel digital receiver using frequency domain multiplexing was implemented and verified on a home-built 0.3 T magnetic resonance imaging system. The experimental results confirmed that the cross talk between each channel was below -60 dB, the phase fluctuations were about 1 degrees , and there was no obvious signal-to-noise ratio degradation. It is demonstrated that the frequency domain multiplexing is a valuable and economical technique, particularly for array coil systems where the multichannel receiver is indispensable and dynamic range is not a critical problem.
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Affiliation(s)
- Wang He
- Shanghai Key Laboratory of Functional Magnetic Resonance Imaging, East China Normal University, Shanghai 200062, People's Republic of China
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