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von Kleist H, Buehrer M, Kozerke S, Saengsin K, Harrington JK, Powell AJ, Moghari MH. Cardiac self-gating using blind source separation for 2D cine cardiovascular magnetic resonance imaging. Magn Reson Imaging 2021; 81:42-52. [PMID: 33905835 DOI: 10.1016/j.mri.2021.04.008] [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: 01/10/2021] [Revised: 04/11/2021] [Accepted: 04/21/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE To develop and validate a new cardiac self-gating algorithm using blind source separation for 2D cine steady-state free precession (SSFP) imaging. METHODS A standard cine SSFP sequence was modified so that the center point of k-space was sampled with each excitation. The center points of k-space were processed by 4 blind source separation methods, and used to detect heartbeats and assign k-space data to appropriate time points in the cardiac cycle. The proposed self-gating technique was prospectively validated in 8 patients against the standard electrocardiogram (ECG)-gating method by comparing the cardiac cycle lengths, image quality metrics, and ventricular volume measurements. RESULTS There was close agreement between the cardiac cycle length using the ECG- and self-gating methods (bias 0.0 bpm, 95% limits of agreement ±2.1 bpm). The image quality metrics were not significantly different between the ECG- and self-gated images. The ventricular volumes, stroke volumes, and mass measured from self-gated images were all comparable with those from ECG-gated images (all biases <5%). CONCLUSION The self-gating method yielded comparable cardiac cycle length, image quality, and ventricular measurements compared with standard ECG-gated cine imaging. It may simplify patient preparation, be more robust when there is arrhythmia, and allow cardiac gating at higher field strengths.
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Affiliation(s)
- Henrik von Kleist
- Department of Cardiology, Boston Children's Hospital, and Department of Pediatrics, Harvard Medical School, Boston, MA, USA; Department of Informatics, Technical University of Munich, Garching, Germany.
| | - Martin Buehrer
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Kwannapas Saengsin
- Department of Cardiology, Boston Children's Hospital, and Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Jamie K Harrington
- Department of Cardiology, Boston Children's Hospital, and Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Andrew J Powell
- Department of Cardiology, Boston Children's Hospital, and Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Mehdi H Moghari
- Department of Cardiology, Boston Children's Hospital, and Department of Pediatrics, Harvard Medical School, Boston, MA, USA
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Bruijnen T, Stemkens B, van den Berg CAT, Tijssen RHN. Prospective GIRF-based RF phase cycling to reduce eddy current-induced steady-state disruption in bSSFP imaging. Magn Reson Med 2019; 84:115-127. [PMID: 31755580 PMCID: PMC7154723 DOI: 10.1002/mrm.28097] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 11/04/2019] [Accepted: 11/04/2019] [Indexed: 11/07/2022]
Abstract
Purpose To propose an explicit Balanced steady‐state free precession (bSSFP) signal model that predicts eddy current‐induced steady‐state disruptions and to provide a prospective, practical, and general eddy current compensation method. Theory and Methods Gradient impulse response functions (GIRF) were used to simulate trajectory‐specific eddy current‐induced phase errors at the end of a repetition block. These phase errors were included in bloch simulations to establish a bSSFP signal model to predict steady‐state disruptions and their corresponding image artifacts. The signal model was embedded in the MR system and used to compensate the phase errors by prospectively modifying the phase cycling scheme of the RF pulse. The signal model and eddy current compensation method were validated in phantom and in vivo experiments. In addition, the signal model was used to analyze pre‐existing eddy current mitigation methods, such as 2D tiny golden angle radial and 3D paired phase encoded Cartesian acquisitions. Results The signal model predicted eddy current‐induced image artifacts, with the zeroth‐order GIRF being the primary factor to predict the steady‐state disruption. Prospective RF phase cycling schemes were automatically computed online and considerably reduced eddy current‐induced image artifacts. The signal model provides a direct relationship for the smoothness of k‐space trajectories, which explains the effectiveness of phase encode pairing and tiny golden angle trajectory. Conclusions The proposed signal model can accurately predict eddy current‐induced steady‐state disruptions for bSSFP imaging. The signal model can be used to derive the eddy current‐induced phase errors required for trajectory‐specific RF phase cycling schemes, which considerably reduce eddy current‐induced image artifacts.
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Affiliation(s)
- Tom Bruijnen
- Department of RadiotherapyUniversity Medical Center UtrechtUtrechtThe Netherlands
- Computational Imaging Group for MRI diagnostics and therapy, Centre for Image SciencesUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Bjorn Stemkens
- Department of RadiotherapyUniversity Medical Center UtrechtUtrechtThe Netherlands
- Computational Imaging Group for MRI diagnostics and therapy, Centre for Image SciencesUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Cornelis Antonius Theodorus van den Berg
- Department of RadiotherapyUniversity Medical Center UtrechtUtrechtThe Netherlands
- Computational Imaging Group for MRI diagnostics and therapy, Centre for Image SciencesUniversity Medical Center UtrechtUtrechtThe Netherlands
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Jackson LH, Price AN, Hutter J, Ho A, Roberts TA, Slator PJ, Clough JR, Deprez M, McCabe L, Malik SJ, Chappell L, Rutherford MA, Hajnal JV. Respiration resolved imaging with continuous stable state 2D acquisition using linear frequency SWEEP. Magn Reson Med 2019; 82:1631-1645. [PMID: 31183892 PMCID: PMC6682494 DOI: 10.1002/mrm.27834] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 04/04/2019] [Accepted: 05/09/2019] [Indexed: 01/31/2023]
Abstract
Purpose To investigate the potential of continuous radiofrequency (RF) shifting (SWEEP) as a technique for creating densely sampled data while maintaining a stable signal state for dynamic imaging. Methods We present a method where a continuous stable state of magnetization is swept smoothly across the anatomy of interest, creating an efficient approach to dense multiple 2D slice imaging. This is achieved by introducing a linear frequency offset to successive RF pulses shifting the excited slice by a fraction of the slice thickness with each successive repeat times (TR). Simulations and in vivo imaging were performed to assess how this affects the measured signal. Free breathing, respiration resolved 4D volumes in fetal/placental imaging is explored as potential application of this method. Results The SWEEP method maintained a stable signal state over a full acquisition reducing artifacts from unstable magnetization. Simulations demonstrated that the effects of SWEEP on slice profiles was of the same order as that produced by physiological motion observed with conventional methods. Respiration resolved 4D data acquired with this method shows reduced respiration artifacts and resilience to non‐rigid and non‐cyclic motion. Conclusions The SWEEP method is presented as a technique for improved acquisition efficiency of densely sampled short‐TR 2D sequences. Using conventional slice excitation the number of RF pulses required to enter a true steady state is excessively high when using short‐TR 2D acquisitions, SWEEP circumvents this limitation by creating a stable signal state that is preserved between slices.
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Affiliation(s)
- L H Jackson
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - A N Price
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - J Hutter
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - A Ho
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom.,Department of Women and Children's Health, School of Life Course Sciences, King's College London, London, United Kingdom
| | - T A Roberts
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - P J Slator
- Centre for Medical Image Computing, University College London, London, United Kingdom
| | - J R Clough
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - M Deprez
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - L McCabe
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - S J Malik
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - L Chappell
- Department of Women and Children's Health, School of Life Course Sciences, King's College London, London, United Kingdom
| | - M A Rutherford
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - J V Hajnal
- Biomedical Engineering, School of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
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Guo L, Herzka DA. Sorted Golden-step phase encoding: an improved Golden-step imaging technique for cardiac and respiratory self-gated cine cardiovascular magnetic resonance imaging. J Cardiovasc Magn Reson 2019; 21:23. [PMID: 30999911 PMCID: PMC6472023 DOI: 10.1186/s12968-019-0533-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 03/19/2019] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Numerous self-gated cardiac imaging techniques have been reported in the literature. Most can track either cardiac or respiratory motion, and many incur some overhead to imaging data acquisition. We previously described a Cartesian cine imaging technique, pseudo-projection motion tracking with golden-step phase encoding, capable of tracking both cardiac and respiratory motion at no cost to imaging data acquisition. In this work, we describe improvements to the technique by dramatically reducing its vulnerability to eddy current and flow artifacts and demonstrating its effectiveness in expanded cardiovascular applications. METHODS As with our previous golden-step technique, the Cartesian phase encodes over time were arranged based on the integer golden step, and readouts near ky = 0 (pseudo-projections) were used to derive motion. In this work, however, the readouts were divided into equal and consecutive temporal segments, within which the readouts were sorted according to ky. The sorting reduces the phase encode jump between consecutive readouts while maintaining the pseudo-randomness of ky to sample both cardiac and respiratory motion without comprising the ability to retrospectively set the temporal resolution of the original technique. On human volunteers, free-breathing, electrocardiographic (ECG)-free cine scans were acquired for all slices of the short axis stack and the 4-chamber view of the long axis. Retrospectively, cardiac motion and respiratory motion were automatically extracted from the pseudo-projections to guide cine reconstruction. The resultant image quality in terms of sharpness and cardiac functional metrics was compared against breath-hold ECG-gated reference cines. RESULTS With sorting, motion tracking of both cardiac and respiratory motion was effective for all slices orientations imaged, and artifact occurrence due to eddy current and flow was efficiently eliminated. The image sharpness derived from the self-gated cines was found to be comparable to the reference cines (mean difference less than 0.05 mm- 1 for short-axis images and 0.075 mm- 1 for long-axis images), and the functional metrics (mean difference < 4 ml) were found not to be statistically different from those from the reference. CONCLUSIONS This technique dramatically reduced the eddy current and flow artifacts while preserving the ability of cost-free motion tracking and the flexibility of choosing arbitrary navigator zone width, number of cardiac phases, and duration of scanning. With the restriction of the artifacts removed, the Cartesian golden-step cine imaging can now be applied to cardiac imaging slices of more diverse orientation and anatomy at greater reliability.
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Affiliation(s)
- Liheng Guo
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Ave, Suite 726 Ross Building, Baltimore, MD 21205 USA
| | - Daniel A. Herzka
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Ave, Suite 726 Ross Building, Baltimore, MD 21205 USA
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Kim B, Seo H, Kim D, Park H. Retrospective motion gating in cardiac MRI using a simultaneously acquired navigator. NMR IN BIOMEDICINE 2018; 31:e3874. [PMID: 29266452 DOI: 10.1002/nbm.3874] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/03/2017] [Accepted: 11/06/2017] [Indexed: 06/07/2023]
Abstract
A simultaneous acquisition technique of image and navigator signals (simultaneously acquired navigator, SIMNAV) is proposed for cardiac magnetic resonance imaging (CMRI) in Cartesian coordinates. To simultaneously acquire both image and navigator signals, a conventional balanced steady-state free precession (bSSFP) pulse sequence is modified by adding a radiofrequency (RF) pulse, which excites a supplementary slice for the navigator signal. Alternating phases of the RF pulses make it easy to separate the simultaneously acquired magnetic resonance data into image and navigator signals. The navigator signals of the proposed SIMNAV were compared with those of current gating devices and self-gating techniques for seven healthy subjects. In vivo experiments demonstrated that SIMNAV could provide cardiac cine images with sufficient image quality, similar to those from electrocardiogram (ECG) gating with breath-hold. SIMNAV can be used to acquire a cardiac cine image without requiring an ECG device and breath-hold, whilst maintaining feasible imaging time efficiency.
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Affiliation(s)
- Byungjai Kim
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Guseong-dong, Yuseong-gu, Daejeon, South Korea
| | - Hyunseok Seo
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Guseong-dong, Yuseong-gu, Daejeon, South Korea
| | - Dongchan Kim
- College of Medicine, Gachon University, Hambakmoero 191, Yeonsu-gu, Incheon, South Korea
| | - HyunWook Park
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Guseong-dong, Yuseong-gu, Daejeon, South Korea
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Mickevicius NJ, Paulson ES. Simultaneous orthogonal plane imaging. Magn Reson Med 2016; 78:1700-1710. [DOI: 10.1002/mrm.26555] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 10/10/2016] [Accepted: 10/28/2016] [Indexed: 12/25/2022]
Affiliation(s)
| | - Eric S. Paulson
- Department of Biophysics; Medical College of Wisconsin; Milwaukee Wisconsin USA
- Department of Radiation Oncology; Medical College of Wisconsin; Milwaukee Wisconsin USA
- Department of Radiology; Medical College of Wisconsin; Milwaukee Wisconsin USA
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