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Peng X, Wang D, Borup D, Krishnamoorthy G, Pipe JG. Simultaneous brain and neck time-of-flight MRA using spiral multiband with localized quadratic encoding. Magn Reson Med 2024. [PMID: 38576077 DOI: 10.1002/mrm.30098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 02/22/2024] [Accepted: 03/15/2024] [Indexed: 04/06/2024]
Abstract
PURPOSE To develop a method that achieves simultaneous brain and neck time-of-flight (ToF) magnetic resonance angiography (MRA) within feasible scan timeframes. METHODS Localized quadratic (LQ) encoding is efficient for both signal-to-noise ratio (SNR) and in-flow enhancement. We proposed a spiral multiband LQ method to enable simultaneous intracranial and carotid ToF-MRA within a single scan. To address the venous signal contamination that becomes a challenge with multiband (MB) ToF, tilt-optimized non-saturated excitation (TONE) and partial-Fourier slice selection (PFSS) were further introduced in the LQ framework to mitigate the venous signal and improve artery contrast. A sequential spiral MB and LQ reconstruction pipeline was employed to obtain the brain-and-neck image volumes. RESULTS The proposed MB method was able to achieve simultaneous brain and neck ToF-MRA within a 2:50-min scan. The complementarily boosted SNR-efficiency by MB and LQ acquisitions allows for the increased spatial coverage without increase in scan time or noticeable compromise in SNR. The incorporation of both TONE and PFSS effectively alleviated the venous contamination with improved small vessel sensitivity. Selection of scan parameters such as the LQ factor and flip angle reflected the trade-off among SNR, blood contrast, and venous suppression. CONCLUSIONS A novel MB spiral LQ approach was proposed to enable fast intracranial and carotid ToF-MRA with minimized venous corruption. The method has shown promise in MRA applications where large spatial coverage is necessary.
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Affiliation(s)
- Xi Peng
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Radiology, University of Iowa, Iowa City, Iowa, USA
| | - Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Guruprasad Krishnamoorthy
- Royal Philips, Rochester, Minnesota, USA
- Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
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2
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Li Z, Wang D, Ooi MB, Choudhary P, Ragunathan S, Karis JP, Pipe JG, Quarles CC, Stokes AM. A 3D dual-echo spiral sequence for simultaneous dynamic susceptibility contrast and dynamic contrast-enhanced MRI with single bolus injection. Magn Reson Med 2024. [PMID: 38469930 DOI: 10.1002/mrm.30077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 02/20/2024] [Accepted: 02/20/2024] [Indexed: 03/13/2024]
Abstract
PURPOSE Perfusion MRI reveals important tumor physiological and pathophysiologic information, making it a critical component in managing brain tumor patients. This study aimed to develop a dual-echo 3D spiral technique with a single-bolus scheme to simultaneously acquire both dynamic susceptibility contrast (DSC) and dynamic contrast-enhanced (DCE) data and overcome the limitations of current EPI-based techniques. METHODS A 3D spiral-based technique with dual-echo acquisition was implemented and optimized on a 3T MRI scanner with a spiral staircase trajectory and through-plane SENSE acceleration for improved speed and image quality, in-plane variable-density undersampling combined with a sliding-window acquisition and reconstruction approach for increased speed, and an advanced iterative deblurring algorithm. Four volunteers were scanned and compared with the standard of care (SOC) single-echo EPI and a dual-echo EPI technique. Two patients were scanned with the spiral technique during a preload bolus and compared with the SOC single-echo EPI collected during the second bolus injection. RESULTS Volunteer data demonstrated that the spiral technique achieved high image quality, reduced geometric artifacts, and high temporal SNR compared with both single-echo and dual-echo EPI. Patient perfusion data showed that the spiral acquisition achieved accurate DSC quantification comparable to SOC single-echo dual-dose EPI, with the additional DCE information. CONCLUSION A 3D dual-echo spiral technique was developed to simultaneously acquire both DSC and DCE data in a single-bolus injection with reduced contrast use. Preliminary volunteer and patient data demonstrated increased temporal SNR, reduced geometric artifacts, and accurate perfusion quantification, suggesting a competitive alternative to SOC-EPI techniques for brain perfusion MRI.
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Affiliation(s)
- Zhiqiang Li
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Poonam Choudhary
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Sudarshan Ragunathan
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - John P Karis
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
| | - C Chad Quarles
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
- Department of Cancer Systems Imaging, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Ashley M Stokes
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
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3
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Wang D, Chao TC, Pipe JG. Accelerating spiral deblurring with square kernels and low-pass preconditioning. Magn Reson Med 2024; 91:1200-1208. [PMID: 38010065 DOI: 10.1002/mrm.29928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 10/10/2023] [Accepted: 10/31/2023] [Indexed: 11/29/2023]
Abstract
PURPOSE Robust implementation of spiral imaging requires efficient deblurring. A deblurring method was previously proposed to separate and deblur water and fat simultaneously, based on image-space kernel operations. The goal of this work is to improve the performance of the previous deblurring method using kernels with better properties. METHODS Four types of kernels were formed using different models for the region outside the collected k-space as well as low-pass preconditioning (LP). The performances of the kernels were tested and compared with both phantom and volunteer data. Data were also synthesized to evaluate the SNR. RESULTS The proposed "square" kernels are much more compact than the previously used circular kernels. Square kernels have better properties in terms of normalized RMS error, structural similarity index measure, and SNR. The square kernels created by LP demonstrated the best performance of artifact mitigation on phantom data. CONCLUSIONS The sizes of the blurring kernels and thus the computational cost can be reduced by the proposed square kernels instead of the previous circular ones. Using LP may further enhance the performance.
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Affiliation(s)
- Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Tzu Cheng Chao
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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Kim D, Wang D, Chao TC, Campeau N, Pipe JG. Volumetric T 2 -weighted spin echo imaging with improved SNR using localized quadratic encoding and a spiral readout trajectory. Magn Reson Med 2023; 90:2261-2274. [PMID: 37639386 DOI: 10.1002/mrm.29788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 05/18/2023] [Accepted: 06/15/2023] [Indexed: 08/31/2023]
Abstract
PURPOSE To demonstrate T2 -weighted (single-echo) spin-echo (SE) imaging with near-optimal acquisition efficiency by applying SNR-efficient RF slice encoding and spiral readout. METHODS A quadratic-phase (frequency swept) excitation RF pulse replaced the conventional excitation in T2 -weighted SE sequence to excite a thick slab that is internally spatially encoded by a variable phase along the slice direction. Highly overlapping slabs centered at every desired slice location were acquired in multiple passes, such that the entire imaging volume was excited by contiguous slabs in any given pass. Following 90° excitation, each slab was refocused with a conventional 180° RF to produce a SE signal, followed by a spiral in-out readout. A noise-insensitive reconstruction removed the quadratic phase in the spatial frequency domain, yielding desired slice resolution and improved SNR. RESULTS Increasing the RF frequency sweep (hence, excitation width) allowed more frequent encoding of each slice over the multiple passes, improving final image SNR, until crosstalk ensued at excessive slab widths compared to their center-to-center spacing. With an optimized slab width, the proposed technique used all passes to acquire every prescribed slice, with substantially improved SNR over conventional SE or 2D-turbo-spin-echo (TSE) scans. Quantitative SNR measurements indicated similar SNR as 3D-TSE, but radiologist scoring favored 3D-TSE, mainly because of spiral-related artifacts and possibly because of regularized reconstructions in 3D-TSE. CONCLUSION Using SNR-efficient slice excitation scheme and spiral readout helped eliminate SNR and temporal inefficiencies in conventional T2 -weighted imaging, yielding SNR independent of TR or number of passes.
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Affiliation(s)
- Dahan Kim
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Tzu-Cheng Chao
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Norbert Campeau
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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5
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Wang D, Krishnamoorthy G, Ooi MB, Pipe JG. Spiral inflow MRA with sliding-slice localized quadratic encoding. Magn Reson Med 2023; 90:1818-1829. [PMID: 37415416 DOI: 10.1002/mrm.29770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 05/27/2023] [Accepted: 06/02/2023] [Indexed: 07/08/2023]
Abstract
PURPOSE This work proposes a 2D/3D hybrid inflow MRA technique for fast scanning and high SNR and contrast-to-noise (CNR) efficiencies. METHODS Localized quadratic (LQ) encoding was combined with a sliding-slice spiral acquisition. Inflow MRAs around the circle of Willis and the carotid bifurcations were collected on four healthy volunteers. Spiral images were deblurred without or with water-fat separation for sliding-slice LQ (ssLQ) out-of-phase (OP) and Dixon inflow MRAs, respectively. Results were compared to multiple overlapping thin slab acquisitions (MOTSA) and 2D OP inflow MRAs. Noise data were also acquired with RF and gradients turned off to compute maps of SNR and SNR efficiency. Quantitative assessment of relative contrast, CNR, and CNR efficiency for flow were performed in regions of interest. RESULTS The sliding-slice spiral technique alone reduces scan time by 10% to 40% compared with a standard spiral acquisition scheme. The proposed spiral ssLQ OP achieves 50% higher scan speed than the spiral MOTSA with comparable SNR and CNR efficiencies, which are ∼100% higher than the Cartesian MOTSA for intracranial inflow MRAs. Spiral ssLQ Dixon inflow MRA provides better visibility for vessels around the fat compared to spiral ssLQ OP inflow MRA, with a trade-off of scan speed. Spiral ssLQ MRA with thinner slice thickness is two to five times faster than the 2D Cartesian inflow neck MRA around the carotid bifurcations, while also achieving higher SNR efficiency. CONCLUSION The proposed spiral ssLQ is a fast and flexible MRA method with improved SNR and CNR efficiencies over traditional Cartesian inflow MRAs.
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Affiliation(s)
- Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Guruprasad Krishnamoorthy
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
- Philips Healthcare, Gainesville, Florida, USA
| | | | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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6
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Chao TC, Peng X, Wang D, Pipe JG. Evaluating efficient SENSE algorithms to deblur spiral MRI with fat/water separation. Magn Reson Med 2023; 90:2190-2197. [PMID: 37379476 DOI: 10.1002/mrm.29773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 05/05/2023] [Accepted: 06/02/2023] [Indexed: 06/30/2023]
Abstract
PURPOSE The combination of SENSE and spiral imaging with fat/water separation enables high temporal efficiency. However, the corresponding computation increases due to the blurring/deblurring operation across the multi-channel data. This study presents two alternative models to simplify computational complexity in the original full model (model 1). The performances of the models are evaluated in terms of the computation time and reconstruction error. METHODS Two approximated spiral MRI reconstruction models were proposed: the comprehensive blurring before coil operation (model 2) and the regional blurring before coil operation (model 3), respectively, by altering the order of coil-sensitivity encoding process to distribute signals among the multi-channel coils. Four subjects were recruited for scanning both fully sampled T1 - and T2 -weighted brain image data with simulated undersampling for testing the computational efficiency and accuracy on the approximation models. RESULTS Based on the examples, the computation time can be reduced to 31%-47% using model 2, and to 39%-56% using model 3. The quality of the water image remains unchanged among the three models, whereas the primary difference in image quality is in the fat channel. The fat images from model 3 are consistent with those from model 1, but those from model 2 have higher normalized error, differing by up to 4.8%. CONCLUSION Model 2 provides the fastest computation but exhibits higher error in the fat channel, particularly in the high field and with long acquisition window. Model 3, an abridged alternative, is also faster than the full model and can maintain high accuracy in reconstruction.
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Affiliation(s)
- Tzu Cheng Chao
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Xi Peng
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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Zhou Z, Alfayad A, Chao TC, Pipe JG. Acoustic noise reduction for spiral MRI by gradient derating. Magn Reson Med 2023. [PMID: 37345705 DOI: 10.1002/mrm.29747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/20/2023] [Accepted: 05/18/2023] [Indexed: 06/23/2023]
Abstract
PURPOSE To show that the acoustic noise of spiral MRI can be reduced by derating the gradients with minimal penalty to image quality and scan time, and to illustrate an algorithm for optimal choice of derating parameters. THEORY AND METHODS Acoustic noise level was measured and compared for various values of maximum gradient amplitude and slew rate for T1 -weighted spin-echo spiral scans while maintaining image contrast, FOV and resolution, and readout time. A full gradient trajectory and a derated gradient (undersampled) trajectory were chosen for a volunteer scan followed by parallel imaging-aided reconstruction to illustrate comparable image SNR. Two auto-derating methods, which prioritize slew rate and gradient amplitude, respectively, were derived using analytical results from the WHIRLED PEAS variant of spiral waveforms and compared in their acoustic noise level under test use cases. RESULTS Derating the gradients made the scan quieter by 16.6 dB(A) on average than a full gradient trajectory and required an undersampling factor R = 2 in order to maintain scan time, with no appreciable penalty in image SNR. Prioritizing reduced slew rate resulted in maximal loudness reduction. CONCLUSION Scanner gradients can often be derated to reduce the acoustic noise for spiral MRI with minimal penalty in scan time and image quality with the help of parallel imaging. An automatic slew-priority derating method that maximizes loudness reduction is given.
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Affiliation(s)
- Zeyu Zhou
- Department of Radiology, Mayo Clinic, Rochester, 55905, Minnesota, USA
| | | | - Tzu Cheng Chao
- Department of Radiology, Mayo Clinic, Rochester, 55905, Minnesota, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, 55905, Minnesota, USA
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8
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Chao TC, Wang D, Krishnamoorthy G, Pipe JG. A field map updating algorithm to improve fat-water spiral imaging. Magn Reson Med 2023. [PMID: 37158313 DOI: 10.1002/mrm.29697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 04/20/2023] [Accepted: 04/21/2023] [Indexed: 05/10/2023]
Abstract
PURPOSE An accurate field map is essential to separate fat and water signals in a dual-echo chemical shift encoded spiral MRI scan. A rapid low-resolution B0 map prescan is usually performed before each exam. Occasional inaccuracy in these field map estimates can lead to misclassification of the water and fat signals as well as blurring artifacts in the reconstruction. The present work proposes a self-consistent model to evaluate residual field offsets according to the image data to improve the reconstruction quality and facilitate the scan efficiency. THEORY AND METHODS The proposed method compares the phase differences of the two-echo data after correcting for fat frequency offsets. A more accurate field map is approximated according to the phase discrepancies and improved image quality. Experiments were conducted with simulated off-resonance on a numerical phantom, five volunteer head scans, and four volunteer abdominal scans for validation. RESULTS The initial reconstruction of the demonstrated examples exhibit blurring artifacts and misregistration of fat and water because of the inaccuracy of the field map. The proposed method updates the field map to amend the fat and water estimation and improve image quality. CONCLUSIONS This work presents a model to improve the quality of fat-water imaging of the spiral MRI by estimating a better field map from the acquired data. It allows reducing the field map pre-scans before each spiral scan under normal circumstances to increase scan efficiency.
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Affiliation(s)
- Tzu Cheng Chao
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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Wang D, Robison RK, Li Z, Pipe JG. High SNR rapid T 1 -weighted MPRAGE using spiral imaging with long readouts and improved deblurring. Magn Reson Med 2023; 89:951-963. [PMID: 36321560 DOI: 10.1002/mrm.29492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 09/26/2022] [Accepted: 09/27/2022] [Indexed: 11/07/2022]
Abstract
PURPOSE The goal of this work is to present the implementation of 3D spiral high-resolution MPRAGE and to demonstrate that SNR and scan efficiency increase with the increment of readout time. THEORY Simplified signal equations for MPRAGE indicate that the T1 contrast can be kept approximately the same by a simple relationship between the flip angle and the TR. Furthermore, if T1 contrast remains the same, image SNR depends on the square root of the product of the total scan time and the readout time. METHODS MPRAGE spiral sequences were implemented with distributed spirals and spiral staircase on 3 Tesla scanners. Brain images of three volunteers were acquired with different readout times. Spiral images were processed with a joint water-fat separation and deblurring algorithm and compared to Cartesian images. Pure noise data sets were also acquired for SNR evaluation. RESULTS Consistent T1 weighting can be achieved with various spiral readout lengths, and between spiral MPRAGE imaging and the traditional Cartesian MPRAGE imaging. Noise performance analysis demonstrates higher SNR efficiency of spiral MPRAGE imaging with matched T1 contrast compared to the Cartesian reference imaging. CONCLUSION Fast, high SNR MPRAGE imaging is feasible with long readout spiral trajectories.
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Affiliation(s)
- Dinghui Wang
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Zhiqiang Li
- Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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10
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Peng X, Sui Y, Trzasko JD, Glaser KJ, Huston J, Ehman RL, Pipe JG. Fast 3D MR elastography of the whole brain using spiral staircase: Data acquisition, image reconstruction, and joint deblurring. Magn Reson Med 2021; 86:2011-2024. [PMID: 34096097 PMCID: PMC8498799 DOI: 10.1002/mrm.28855] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 04/06/2021] [Accepted: 05/04/2021] [Indexed: 02/06/2023]
Abstract
PURPOSE To address the need for a method to acquire 3D data for MR elastography (MRE) of the whole brain with substantially improved spatial resolution, high SNR, and reduced acquisition time compared with conventional methods. METHODS We combined a novel 3D spiral staircase data-acquisition method with a spoiled gradient-echo pulse sequence and MRE motion-encoding gradients (MEGs). The spiral-out acquisition permitted use of longer-duration motion-encoding gradients (ie, over two full oscillatory cycles) to enhance displacement SNR, while still maintaining a reasonably short TE for good phase-SNR. Through-plane parallel imaging with low noise penalties was implemented to accelerate acquisition along the slice direction. Shared anatomical information was exploited in the deblurring procedure to further boost SNR for stiffness inversion. RESULTS In vivo and phantom experiments demonstrated the feasibility of the proposed method in producing brain MRE results comparable to the spin-echo-based approaches, both qualitatively and quantitatively. High-resolution (2-mm isotropic) brain MRE data were acquired in 5 minutes using our method with good SNR. Joint deblurring with shared anatomical information produced SNR-enhanced images, leading to upward stiffness estimation. CONCLUSION A novel 3D gradient-echo-based approach has been designed and implemented, and shown to have promising potential for fast and high-resolution in vivo MRE of the whole brain.
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Affiliation(s)
- Xi Peng
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Yi Sui
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Kevin J Glaser
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - John Huston
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Richard L Ehman
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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11
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Pipe JG, Borup DD. Generating spiral gradient waveforms with a compact frequency spectrum. Magn Reson Med 2021; 87:791-799. [PMID: 34519379 DOI: 10.1002/mrm.28993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 11/11/2022]
Abstract
PURPOSE To generate efficient gradient waveforms for spiral MRI which mitigate the high-frequency attenuation inherent in gradient systems. THEORY AND METHODS Spiral MRI has many clinical advantages, including high temporal and SNR efficiency. One of the challenges for robust spiral MRI is a high sensitivity to imperfections in the gradient system, which requires some form of correction in order to map data correctly in k-space. A previous numerical algorithm for generating spiral gradient waveforms was modified to reduce its high-frequency content with minimal increase in waveform duration. RESULTS Examples are shown of compact frequency gradient waveforms. Software implementing the algorithm is made available. CONCLUSION An algorithm to produce gradient waveforms with a compact frequency spectrum is described. This algorithm results in greatly reduced overall error and better compatibility with gradient systems than the original algorithm from which it was derived.
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Affiliation(s)
- James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
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12
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Stokes AM, Ragunathan S, Robison RK, Fuentes A, Bell LC, Karis JP, Pipe JG, Quarles CC. Development of a spiral spin- and gradient-echo (spiral-SAGE) approach for improved multi-parametric dynamic contrast neuroimaging. Magn Reson Med 2021; 86:3082-3095. [PMID: 34288112 DOI: 10.1002/mrm.28933] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 06/29/2021] [Accepted: 06/30/2021] [Indexed: 11/09/2022]
Abstract
PURPOSE The purpose of this study was to develop a spiral-based combined spin- and gradient-echo (spiral-SAGE) method for simultaneous dynamic contrast-enhanced (DCE-MRI) and dynamic susceptibility contrast MRI (DSC-MRI). METHODS Using this sequence, we obtained gradient-echo TEs of 1.69 and 26 ms, a SE TE of 87.72 ms, with a TR of 1663 ms. Using an iterative SENSE reconstruction followed by deblurring, spiral-induced image artifacts were minimized. Healthy volunteer images are shown to demonstrate image quality using the optimized reconstruction, as well as for comparison with EPI-based SAGE. A bioreactor phantom was used to compare dynamic-contrast time courses with both spiral-SAGE and EPI-SAGE. A proof-of-concept cohort of patients with brain tumors shows the range of hemodynamic maps available using spiral-SAGE. RESULTS Comparison of spiral-SAGE images with conventional EPI-SAGE images illustrates substantial reductions of image distortion and artifactual image intensity variations. Bioreactor phantom data show similar dynamic contrast time courses between standard EPI-SAGE and spiral-SAGE for the second and third echoes, whereas first-echo data show improvements in quantifying T1 changes with shorter echo times. In a cohort of patients with brain tumors, spiral-SAGE-based perfusion and permeability maps are shown with comparison with the standard single-echo EPI perfusion map. CONCLUSION Spiral-SAGE provides a substantial improvement for the assessment of perfusion and permeability by mitigating artifacts typically encountered with EPI and by providing a shorter echo time for improved characterization of permeability. Spiral-SAGE enables quantification of perfusion, permeability, and vessel architectural parameters, as demonstrated in brain tumors.
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Affiliation(s)
- Ashley M Stokes
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Sudarshan Ragunathan
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Ryan K Robison
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA.,Philips Healthcare, Nashville, Tennessee, USA.,Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Alberto Fuentes
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Laura C Bell
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - John P Karis
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA.,Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA.,Mayo Clinic, Rochester, Minnesota, USA
| | - C Chad Quarles
- Barrow Neuroimaging Innovation Center, Barrow Neurological Institute, Phoenix, Arizona, USA
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13
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Ooi MB, Li Z, Robison RK, Wang D, Anderson AG, Zwart NR, Bakhru A, Nagaraj S, Mathews T, Hey S, Koonen JJ, Dimitrov IE, Friel HT, Lu Q, Obara M, Saha I, Wang H, Wang Y, Zhao Y, Temkit M, Hu HH, Chenevert TL, Togao O, Tkach JA, Nagaraj UD, Pinho MC, Gupta RK, Small JE, Kunst MM, Karis JP, Andre JB, Miller JH, Pinter NK, Pipe JG. Spiral T1 Spin-Echo for Routine Postcontrast Brain MRI Exams: A Multicenter Multireader Clinical Evaluation. AJNR Am J Neuroradiol 2020; 41:238-245. [PMID: 32029467 DOI: 10.3174/ajnr.a6409] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 12/10/2019] [Indexed: 02/02/2023]
Abstract
BACKGROUND AND PURPOSE Spiral MR imaging has several advantages compared with Cartesian MR imaging that can be leveraged for added clinical value. A multicenter multireader study was designed to compare spiral with standard-of-care Cartesian postcontrast structural brain MR imaging on the basis of relative performance in 10 metrics of image quality, artifact prevalence, and diagnostic benefit. MATERIALS AND METHODS Seven clinical sites acquired 88 total subjects. For each subject, sites acquired 2 postcontrast MR imaging scans: a spiral 2D T1 spin-echo, and 1 of 4 routine Cartesian 2D T1 spin-echo/TSE scans (fully sampled spin-echo at 3T, 1.5T, partial Fourier, TSE). The spiral acquisition matched the Cartesian scan for scan time, geometry, and contrast. Nine neuroradiologists independently reviewed each subject, with the matching pair of spiral and Cartesian scans compared side-by-side, and scored on 10 image-quality metrics (5-point Likert scale) focused on intracranial assessment. The Wilcoxon signed rank test evaluated relative performance of spiral versus Cartesian, while the Kruskal-Wallis test assessed interprotocol differences. RESULTS Spiral was superior to Cartesian in 7 of 10 metrics (flow artifact mitigation, SNR, GM/WM contrast, image sharpness, lesion conspicuity, preference for diagnosing abnormal enhancement, and overall intracranial image quality), comparable in 1 of 10 metrics (motion artifacts), and inferior in 2 of 10 metrics (susceptibility artifacts, overall extracranial image quality) related to magnetic susceptibility (P < .05). Interprotocol comparison confirmed relatively higher SNR and GM/WM contrast for partial Fourier and TSE protocol groups, respectively (P < .05). CONCLUSIONS Spiral 2D T1 spin-echo for routine structural brain MR imaging is feasible in the clinic with conventional scanners and was preferred by neuroradiologists for overall postcontrast intracranial evaluation.
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Affiliation(s)
- M B Ooi
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - Z Li
- Gainesville, Florida; Barrow Neurological Institute (Z.L., A.G.A., N.R.Z., J.P.K.)
| | - R K Robison
- Rochester, Minnesota; Phoenix Children's Hospital (R.K.R., M.T., H.H.H., J.H.M.)
| | - D Wang
- Phoenix, Arizona; Mayo Clinic (D.W., J.G.P.)
| | - A G Anderson
- Gainesville, Florida; Barrow Neurological Institute (Z.L., A.G.A., N.R.Z., J.P.K.)
| | - N R Zwart
- Gainesville, Florida; Barrow Neurological Institute (Z.L., A.G.A., N.R.Z., J.P.K.)
| | - A Bakhru
- Buffalo, New York; Philips Healthcare (A.B., S.N., T.M.)
| | - S Nagaraj
- Buffalo, New York; Philips Healthcare (A.B., S.N., T.M.)
| | - T Mathews
- Buffalo, New York; Philips Healthcare (A.B., S.N., T.M.)
| | - S Hey
- Bangalore, India; Philips Healthcare, (S.H., J.J.K.), Best, the Netherlands
| | - J J Koonen
- Bangalore, India; Philips Healthcare, (S.H., J.J.K.), Best, the Netherlands
| | - I E Dimitrov
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - H T Friel
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - Q Lu
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - M Obara
- Philips Healthcare (M.O.), Tokyo, Japan
| | - I Saha
- Philips Healthcare (I.S.), Gurgaon, India
| | - H Wang
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - Y Wang
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - Y Zhao
- From Philips Healthcare (M.B.O., I.E.D., H.T.F., Q.L., H.W., Y.W., Y.Z.)
| | - M Temkit
- Rochester, Minnesota; Phoenix Children's Hospital (R.K.R., M.T., H.H.H., J.H.M.)
| | - H H Hu
- Rochester, Minnesota; Phoenix Children's Hospital (R.K.R., M.T., H.H.H., J.H.M.)
| | - T L Chenevert
- University of Michigan (T.L.C.), Ann Arbor, Michigan
| | - O Togao
- Kyushu University Hospital (O.T.), Kyushu, Japan
| | - J A Tkach
- Cincinnati Children's Hospital (J.A.T., U.D.N.), Cincinnati, Ohio
| | - U D Nagaraj
- Cincinnati Children's Hospital (J.A.T., U.D.N.), Cincinnati, Ohio
| | - M C Pinho
- University of Texas Southwestern Medical Center (M.C.P.), Dallas, Texas
| | - R K Gupta
- Fortis Memorial Research Institute (R.K.G.), Gurgaon, India
| | - J E Small
- Lahey Hospital and Medical Center (J.E.S., M.M.K.), Burlington, Massachusetts
| | - M M Kunst
- Lahey Hospital and Medical Center (J.E.S., M.M.K.), Burlington, Massachusetts
| | - J P Karis
- Gainesville, Florida; Barrow Neurological Institute (Z.L., A.G.A., N.R.Z., J.P.K.)
| | - J B Andre
- University of Washington (J.B.A.), Seattle, Washington
| | - J H Miller
- Rochester, Minnesota; Phoenix Children's Hospital (R.K.R., M.T., H.H.H., J.H.M.)
| | - N K Pinter
- Phoenix, Arizona; DENT Neurologic Institute (N.K.P.)
| | - J G Pipe
- Phoenix, Arizona; Mayo Clinic (D.W., J.G.P.)
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14
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Anderson AG, Wang D, Pipe JG. Controlled aliasing for improved parallel imaging with a 3D spiral staircase trajectory. Magn Reson Med 2020; 84:866-872. [DOI: 10.1002/mrm.28154] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 11/21/2019] [Accepted: 12/09/2019] [Indexed: 11/11/2022]
Affiliation(s)
| | - Dinghui Wang
- Department of Radiology Mayo Clinic Rochester Minnesota
| | - James G. Pipe
- Department of Radiology Mayo Clinic Rochester Minnesota
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15
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Willmering MM, Niedbalski PJ, Wang H, Walkup LL, Robison RK, Pipe JG, Cleveland ZI, Woods JC. Improved pulmonary 129 Xe ventilation imaging via 3D-spiral UTE MRI. Magn Reson Med 2019; 84:312-320. [PMID: 31788858 DOI: 10.1002/mrm.28114] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/13/2019] [Accepted: 11/15/2019] [Indexed: 02/03/2023]
Abstract
PURPOSE Hyperpolarized 129 Xe MRI characterizes regional lung ventilation in a variety of disease populations, with high sensitivity to airway obstruction in early disease. However, ventilation images are usually limited to a single breath-hold and most-often acquired using gradient-recalled echo sequences with thick slices (~10-15 mm), which increases partial-volume effects, limits ability to observe small defects, and suffers from imperfect slice selection. We demonstrate higher-resolution ventilation images, in shorter breath-holds, using FLORET (Fermat Looped ORthogonally Encoded Trajectories), a center-out 3D-spiral UTE sequence. METHODS In vivo human adult (N = 4; 2 healthy, 2 with cystic fibrosis) 129 Xe images were acquired using 2D gradient-recalled echo, 3D radial, and FLORET. Each sequence was acquired at its highest possible resolution within a 16-second breath-hold with a minimum voxel dimension of 3 mm. Images were compared using 129 Xe ventilation defect percentage, SNR, similarity coefficients, and vasculature cross-sections. RESULTS The FLORET sequence obtained relative normalized SNR, 40% greater than 2D gradient-recalled echo (P = .012) and 26% greater than 3D radial (P = .067). Moreover, the FLORET images were acquired with 3-fold-higher nominal resolution in a 15% shorter breath-hold. Finally, vasculature was less prominent in FLORET, likely due to diminished susceptibility-induced dephasing at shorter TEs afforded by UTE sequences. CONCLUSION The FLORET sequence yields higher SNR for a given resolution with a shorter breath-hold than traditional ventilation imaging techniques. This sequence more accurately measures ventilation abnormalities and enables reduced scan times in patients with poor compliance and severe lung disease.
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Affiliation(s)
- Matthew M Willmering
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Peter J Niedbalski
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Hui Wang
- Clinical Science, Philips, Cincinnati, Ohio.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Laura L Walkup
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati Medical Center, Cincinnati, Ohio
| | - Ryan K Robison
- Department of Radiology, Phoenix Children's Hospital, Phoenix, Arizona
| | - James G Pipe
- Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Zackary I Cleveland
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati Medical Center, Cincinnati, Ohio.,Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio
| | - Jason C Woods
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati Medical Center, Cincinnati, Ohio
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16
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Willmering MM, Robison RK, Wang H, Pipe JG, Woods JC. Implementation of the FLORET UTE sequence for lung imaging. Magn Reson Med 2019; 82:1091-1100. [PMID: 31081961 PMCID: PMC6559861 DOI: 10.1002/mrm.27800] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/21/2019] [Accepted: 04/15/2019] [Indexed: 12/28/2022]
Abstract
PURPOSE Magnetic resonance imaging of lungs is inherently challenging, but it has become more common with the use of UTE sequences and their relative insensitivity to motion. Spiral UTE sequences have been touted recently as having greater k-space sampling efficiencies than radial UTE, but few are designed for the shorter T2 * of the lung. In this study, FLORET (Fermat looped, orthogonally encoded trajectories), a recently developed spiral 3D-UTE sequence designed for the short T2 * species, was implemented in human lungs for the first time and the images were compared with traditional radial UTE images. METHODS The FLORET sequence was implemented with parameters optimized for lung imaging on healthy and diseased (cystic fibrosis) subjects. On healthy subjects, radial UTE images (3D-radial and 2D-radial with phase encoding) were acquired for comparison to FLORET. Various metrics including SNR, vasculature contrast, diaphragm sharpness, and parenchymal density ratios were acquired and compared among the separate UTE sequences. RESULTS The FLORET sequence performed similarly to traditional radial UTE methods with a much shorter total scan time for fully sampled images (FLORET: 1 minute 55 seconds, 3D-radial: 3 minutes 25 seconds, 2D-radial with phase encoding: 7 minutes 22 seconds). Additionally, the FLORET image obtained on the cystic fibrosis subject resulted in the observation of cystic fibrosis lung pathology similar or superior to that of the other UTE-MRI techniques. CONCLUSION The FLORET sequence allows for faster acquisition of high diagnostic-quality lung images and its short T2 * components without sacrificing SNR, image quality, or tissue/disease quantification.
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Affiliation(s)
- Matthew M. Willmering
- Center for Pulmonary Imaging Research, Divisions of Pulmonary Medicine and Radiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - Ryan K. Robison
- Department of Radiology, Phoenix Children’s Hospital, Phoenix, AZ, 85016, USA
| | - Hui Wang
- Center for Pulmonary Imaging Research, Divisions of Pulmonary Medicine and Radiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, 45229, USA
- Clinical Science, Philips Healthcare, Gainesville, FL, 32608, USA
| | - James G. Pipe
- Imaging Research, Barrow Neurological Institute, Phoenix, AZ, 85013, USA
| | - Jason C. Woods
- Center for Pulmonary Imaging Research, Divisions of Pulmonary Medicine and Radiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, 45229, USA
- Departments of Pediatrics, Radiology, and Physics, University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
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17
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Li Z, Pipe JG, Ooi MB, Kuwabara M, Karis JP. Improving the image quality of 3D FLAIR with a spiral MRI technique. Magn Reson Med 2019; 83:170-177. [DOI: 10.1002/mrm.27911] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 06/26/2019] [Accepted: 06/29/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Zhiqiang Li
- Barrow Neurological Institute Phoenix Arizona
| | | | - Melvyn B. Ooi
- Barrow Neurological Institute Phoenix Arizona
- Philips Healthcare Gainesville Florida
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18
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Robison RK, Li Z, Wang D, Ooi MB, Pipe JG. Correction of B
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eddy current effects in spiral MRI. Magn Reson Med 2018; 81:2501-2513. [DOI: 10.1002/mrm.27583] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 10/05/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Ryan K. Robison
- Phoenix Children's Hospital Phoenix Arizona
- Barrow Neurological Institute Phoenix Arizona
| | - Zhiqiang Li
- Barrow Neurological Institute Phoenix Arizona
| | | | - Melvyn B. Ooi
- Barrow Neurological Institute Phoenix Arizona
- Philips Healthcare Gainesville Florida
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19
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Affiliation(s)
- James G. Pipe
- Imaging ResearchBarrow Neurological Institute Mayo ClinicRochester MinnesotaUSA
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20
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van Beek EJR, Kuhl C, Anzai Y, Desmond P, Ehman RL, Gong Q, Gold G, Gulani V, Hall-Craggs M, Leiner T, Lim CCT, Pipe JG, Reeder S, Reinhold C, Smits M, Sodickson DK, Tempany C, Vargas HA, Wang M. Value of MRI in medicine: More than just another test? J Magn Reson Imaging 2018; 49:e14-e25. [PMID: 30145852 DOI: 10.1002/jmri.26211] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/16/2018] [Indexed: 02/06/2023] Open
Abstract
There is increasing scrutiny from healthcare organizations towards the utility and associated costs of imaging. MRI has traditionally been used as a high-end modality, and although shown extremely important for many types of clinical scenarios, it has been suggested as too expensive by some. This editorial will try and explain how value should be addressed and gives some insights and practical examples of how value of MRI can be increased. It requires a global effort to increase accessibility, value for money, and impact on patient management. We hope this editorial sheds some light and gives some indications of where the field may wish to address some of its research to proactively demonstrate the value of MRI. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;49:e14-e25.
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Affiliation(s)
| | - Christiane Kuhl
- Department of Diagnostic and Interventional Radiology, University of Aachen, Aachen, Germany
| | - Yoshimi Anzai
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA
| | - Patricia Desmond
- Royal Melbourne Hospital, University of Melbourne, Melbourne, Australia
| | - Richard L Ehman
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Qiyong Gong
- Huaxi MR Research Center (HMRRC), Department of Radiology, West China Hospital of Sichuan University, Chengdu, Sichuan, China
| | - Garry Gold
- Department of Radiology, Engineering and Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Vikas Gulani
- Departments of Radiology, Urology and Biomedical Imaging, Case Western Reserve University, University Hospitals of Cleveland, Cleveland, Ohio, USA
| | - Margaret Hall-Craggs
- Department of Medical Imaging and Radiology, University College Hospital NHS Trust, London, UK
| | - Tim Leiner
- Department of Radiology and Nuclear Medicine, University Medical Centre, Utrecht, The Netherlands
| | - C C Tschoyoson Lim
- Department of Neuroradiology, National Neuroscience Institute and Duke NUS Medical School, Singapore, Singapore
| | - James G Pipe
- Department of Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Scott Reeder
- Departments of Radiology, Medical Physics, Biomedical Engineering, Medicine and Emergency Medicine, University of Madison, Madison, Wisconsin, USA
| | - Caroline Reinhold
- Department of Radiology, McGill University Health Center, Montreal, Canada
| | - Marion Smits
- Department of Radiology and Nuclear Medicine, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Daniel K Sodickson
- Department of Radiology, New York University Langone Health, New York, New York, USA
| | - Clare Tempany
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - H Alberto Vargas
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Meiyun Wang
- Department of Radiology, Henan Provincial People's Hospital, Zhengzhou, Henan, China
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21
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Abstract
PURPOSE 2D turbo-spin-echo (TSE) is widely used in the clinic for neuroimaging. However, the long refocusing radiofrequency pulse train leads to high specific absorption rate (SAR) and alters the contrast compared to conventional spin-echo. The purpose of this work is to develop a robust 2D spiral TSE technique for fast T2 -weighted imaging with low SAR and improved contrast. METHODS A spiral-in/out readout is incorporated into 2D TSE to fully take advantage of the acquisition efficiency of spiral sampling while avoiding potential off-resonance-related artifacts compared to a typical spiral-out readout. A double encoding strategy and a signal demodulation method are proposed to mitigate the artifacts because of the T2 -decay-induced signal variation. An adapted prescan phase correction as well as a concomitant phase compensation technique are implemented to minimize the phase errors. RESULTS Phantom data demonstrate the efficacy of the proposed double encoding/signal demodulation, as well as the prescan phase correction and concomitant phase compensation. Volunteer data show that the proposed 2D spiral TSE achieves fast scan speed with high SNR, low SAR, and improved contrast compared to conventional Cartesian TSE. CONCLUSION A robust 2D spiral TSE technique is feasible and provides a potential alternative to conventional 2D Cartesian TSE for T2 -weighted neuroimaging.
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Affiliation(s)
- Zhiqiang Li
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona
| | - John P Karis
- Department of Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona
| | - James G Pipe
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona
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22
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Li Y, Mao D, Li Z, Schär M, Pillai JJ, Pipe JG, Lu H. Cardiac-triggered pseudo-continuous arterial-spin-labeling: A cost-effective scheme to further enhance the reliability of arterial-spin-labeling MRI. Magn Reson Med 2018; 80:969-975. [PMID: 29369422 DOI: 10.1002/mrm.27090] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 12/04/2017] [Accepted: 12/27/2017] [Indexed: 01/01/2023]
Affiliation(s)
- Yang Li
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Deng Mao
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Zhiqiang Li
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Michael Schär
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jay J Pillai
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - James G Pipe
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Hanzhang Lu
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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23
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Wang D, Zwart NR, Pipe JG. Joint water-fat separation and deblurring for spiral imaging. Magn Reson Med 2017; 79:3218-3228. [DOI: 10.1002/mrm.26950] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 08/31/2017] [Accepted: 09/06/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Dinghui Wang
- Imaging Research; Barrow Neurological Institute; Phoenix Arizona USA
| | - Nicholas R. Zwart
- Imaging Research; Barrow Neurological Institute; Phoenix Arizona USA
| | - James G. Pipe
- Imaging Research; Barrow Neurological Institute; Phoenix Arizona USA
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24
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Ragunathan S, Pipe JG. Radiofrequency saturation induced bias in aqueductal cerebrospinal fluid flow quantification obtained using two-dimensional cine phase contrast magnetic resonance imaging. Magn Reson Med 2017; 79:2067-2076. [PMID: 28833454 DOI: 10.1002/mrm.26883] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 07/28/2017] [Accepted: 07/31/2017] [Indexed: 12/31/2022]
Abstract
PURPOSE To explore the extent of bias in cerebrospinal fluid flow estimates due to radiofrequency saturation, and its possible impact on the use of two-dimensional cine phase contrast magnetic resonance imaging in the diagnosis and characterization of normal pressure hydrocephalus in patients. THEORY AND METHODS Theoretical signal equations were generated to describe saturation dependence on velocity. An experimental set of phase contrast magnetic resonance imaging scans with two different flip angles was used to show bias in flow estimates in a flow phantom, and in six different healthy volunteers. The cerebral aqueduct was targeted as the flow region of interest. RESULTS Data from a constant flow phantom showed a spatial distribution of voxels with significant bias in flow at the periphery of the flow region. The velocity difference (bias) maps of the cerebral aqueduct correlated with the spatial velocity gradients around peak systole and peak diastole, and high correlation with temporal velocity gradients during transition between systole and diastole. The aqueductal stroke volume for θ = 30° were found to be significantly higher than for θ = 10° using a Wilcoxon signed rank test. CONCLUSION This work shows the extent of bias in cerebrospinal fluid flow quantification due to radiofrequency saturation effects. This clinical relevance of this error was presented with respect to shunt responsiveness among normal pressure hydrocephalus patients. Magn Reson Med 79:2067-2076, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
| | - James G Pipe
- Barrow Neurological Institute, Imaging Research, Phoenix, Arizona, USA
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25
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Robison RK, Anderson AG, Pipe JG. Three-dimensional ultrashort echo-time imaging using a FLORET trajectory. Magn Reson Med 2016; 78:1038-1049. [PMID: 27775843 DOI: 10.1002/mrm.26500] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 09/15/2016] [Accepted: 09/16/2016] [Indexed: 12/22/2022]
Abstract
PURPOSE Three-dimensional ultrashort echo-time (UTE) imaging commonly makes use of an isotropic 3D radial projection acquisition. The FLORET sequence is proposed and evaluated as a more efficient alternative. METHODS The properties of the FLORET trajectory are contrasted with those of a 3D radial projection trajectory. The theoretical advantages of FLORET, including greater sampling and SNR efficiency, are evaluated based upon experimental data. The effect of T2* decay on FLORET is analyzed in comparison to the 3D radial, Cones, and Density Adapted Radial trajectories. FLORET UTE image quality is compared with 3D radial UTE image quality. RESULTS FLORET is shown to have several advantages over 3D radial acquisitions with respect to image quality, scan time, signal-to-noise, and off-resonance blurring for UTE data. The signal and resolution losses from T2* decay for a FLORET acquisition are shown to be comparable to those of Density Adapted Radial and Density Compensated Cones trajectories. CONCLUSION The FLORET sequence is recommended as an alternative to 3D radial projection sequences for musculoskeletal UTE imaging as well as other UTE applications that accommodate modest to long per shot sampling times. FLORET is not recommended for imaging extremely short T2 species such as dentin. Magn Reson Med 78:1038-1049, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Ryan K Robison
- Imaging Research, Barrow Neurological Institute, 350 West Thomas Rd., Phoenix, Arizona, USA
| | - Ashley G Anderson
- Imaging Research, Barrow Neurological Institute, 350 West Thomas Rd., Phoenix, Arizona, USA
| | - James G Pipe
- Imaging Research, Barrow Neurological Institute, 350 West Thomas Rd., Phoenix, Arizona, USA
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26
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Hu HH, Li Z, Pokorney AL, Chia JM, Stefani N, Pipe JG, Miller JH. Assessment of cerebral blood perfusion reserve with acetazolamide using 3D spiral ASL MRI: Preliminary experience in pediatric patients. Magn Reson Imaging 2016; 35:132-140. [PMID: 27580517 DOI: 10.1016/j.mri.2016.08.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/03/2016] [Accepted: 08/20/2016] [Indexed: 01/04/2023]
Abstract
PURPOSE To demonstrate the clinical feasibility of a new non-Cartesian cylindrically-distributed spiral 3D pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI) pulse sequence in pediatric patients in quantifying cerebral blood flow (CBF) response to an acetazolamide (ACZ) vasodilator challenge. MATERIALS AND METHODS MRI exams were performed on two 3 Tesla Philips Ingenia systems using 32 channel head coil arrays. After local institutional review board approval, the 3D spiral-based pCASL technique was added to a standard brain MRI exam and evaluated in 13 pediatric patients (average age: 11.7±6.4years, range: 1.4-22.2years). All patients were administered ACZ for clinically indicated reasons. Quantitative whole-brain CBF measurements were computed pre- and post-ACZ to assess cerebrovascular reserve. RESULTS 3D spiral pCASL data were successfully reconstructed in all 13 cases. In 11 patients, CBF increased 2.8% to 93.2% after administration of ACZ. In the two remaining patients, CBF decreased by 2.4 to 6.0% after ACZ. The group average change in CBF due to ACZ was approximately 25.0% and individual changes were statistically significant (p<0.01) in all patients using a paired t-test analysis. CBF perfusion data were diagnostically useful in supporting conventional MR angiography and clinical findings. CONCLUSION 3D cylindrically-distributed spiral pCASL MRI provides a robust approach to assess cerebral blood flow and reserve in pediatric patients.
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Affiliation(s)
- Houchun H Hu
- Department of Medical Imaging and Radiology, Phoenix Children's Hospital, Phoenix, AZ, USA.
| | - Zhiqiang Li
- Keller Center for Imaging Innovation, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Amber L Pokorney
- Department of Medical Imaging and Radiology, Phoenix Children's Hospital, Phoenix, AZ, USA
| | | | | | - James G Pipe
- Keller Center for Imaging Innovation, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Jeffrey H Miller
- Department of Medical Imaging and Radiology, Phoenix Children's Hospital, Phoenix, AZ, USA
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Li Z, Hu HH, Miller JH, Karis JP, Cornejo P, Wang D, Pipe JG. A Spiral Spin-Echo MR Imaging Technique for Improved Flow Artifact Suppression in T1-Weighted Postcontrast Brain Imaging: A Comparison with Cartesian Turbo Spin-Echo. AJNR Am J Neuroradiol 2015; 37:642-7. [PMID: 26611994 DOI: 10.3174/ajnr.a4600] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/19/2015] [Indexed: 01/24/2023]
Abstract
BACKGROUND AND PURPOSE A challenge with the T1-weighted postcontrast Cartesian spin-echo and turbo spin-echo brain MR imaging is the presence of flow artifacts. Our aim was to develop a rapid 2D spiral spin-echo sequence for T1-weighted MR imaging with minimal flow artifacts and to compare it with a conventional Cartesian 2D turbo spin-echo sequence. MATERIALS AND METHODS T1-weighted brain imaging was performed in 24 pediatric patients. After the administration of intravenous gadolinium contrast agent, a reference Cartesian TSE sequence with a scanning time of 2 minutes 30 seconds was performed, followed by the proposed spiral spin-echo sequence with a scanning time of 1 minutes 18 seconds, with similar spatial resolution and volumetric coverage. The results were reviewed independently and blindly by 3 neuroradiologists. Scores from a 3-point scale were assigned in 3 categories: flow artifact reduction, subjective preference, and lesion conspicuity, if any. The Wilcoxon signed rank test was performed to evaluate the reviewer scores. The t test was used to evaluate the SNR. The Fleiss κ coefficient was calculated to examine interreader agreement. RESULTS In 23 cases, spiral spin-echo was scored over Cartesian TSE in flow artifact reduction (P < .001). In 21 cases, spiral spin-echo was rated superior in subjective preference (P < .001). Ten patients were identified with lesions, and no statistically significant difference in lesion conspicuity was observed between the 2 sequences. There was no statistically significant difference in SNR between the 2 techniques. The Fleiss κ coefficient was 0.79 (95% confidence interval, 0.65-0.93). CONCLUSIONS The proposed spiral spin-echo pulse sequence provides postcontrast images with minimal flow artifacts at a faster scanning time than its Cartesian TSE counterpart.
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Affiliation(s)
- Z Li
- From the Departments of Imaging Research (Z.L., D.W., J.G.P.)
| | - H H Hu
- Department of Radiology (H.H.H., J.H.M., P.C.), Phoenix Children's Hospital, Phoenix, Arizona
| | - J H Miller
- Department of Radiology (H.H.H., J.H.M., P.C.), Phoenix Children's Hospital, Phoenix, Arizona
| | - J P Karis
- Radiology (J.P.K.), Barrow Neurological Institute, Phoenix, Arizona
| | - P Cornejo
- Department of Radiology (H.H.H., J.H.M., P.C.), Phoenix Children's Hospital, Phoenix, Arizona
| | - D Wang
- From the Departments of Imaging Research (Z.L., D.W., J.G.P.)
| | - J G Pipe
- From the Departments of Imaging Research (Z.L., D.W., J.G.P.)
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Schär M, Eggers H, Zwart NR, Chang Y, Bakhru A, Pipe JG. Dixon water‐fat separation in PROPELLER MRI acquired with two interleaved echoes. Magn Reson Med 2015; 75:718-28. [DOI: 10.1002/mrm.25656] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Revised: 12/16/2014] [Accepted: 01/23/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Michael Schär
- Neuroimaging ResearchBarrow Neurological InstitutePhoenix Arizona USA
- Philips HealthcareCleveland Ohio USA
- Russell H. Morgan Department of Radiology and Radiological ScienceJohns Hopkins UniversityBaltimore Maryland USA
| | | | - Nicholas R. Zwart
- Neuroimaging ResearchBarrow Neurological InstitutePhoenix Arizona USA
| | - Yuchou Chang
- Neuroimaging ResearchBarrow Neurological InstitutePhoenix Arizona USA
| | | | - James G. Pipe
- Neuroimaging ResearchBarrow Neurological InstitutePhoenix Arizona USA
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Wang D, Zwart NR, Li Z, Schär M, Pipe JG. Analytical three‐point Dixon method: With applications for spiral water–fat imaging. Magn Reson Med 2015; 75:627-38. [DOI: 10.1002/mrm.25620] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 12/05/2014] [Accepted: 12/26/2014] [Indexed: 12/21/2022]
Affiliation(s)
- Dinghui Wang
- Barrow Neurological InstitutePhoenix Arizona USA
| | | | - Zhiqiang Li
- Barrow Neurological InstitutePhoenix Arizona USA
| | - Michael Schär
- Barrow Neurological InstitutePhoenix Arizona USA
- Philips HealthcareCleveland OH USA
- Russell H. Morgan Department of Radiology and Radiological ScienceJohns Hopkins UniversityBaltimore MD USA
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Li Z, Wang D, Robison RK, Zwart NR, Schär M, Karis JP, Pipe JG. Sliding-slab three-dimensional TSE imaging with a spiral-In/Out readout. Magn Reson Med 2015; 75:729-38. [PMID: 25753219 DOI: 10.1002/mrm.25660] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 01/28/2015] [Accepted: 01/28/2015] [Indexed: 11/11/2022]
Abstract
PURPOSE T2 -weighted imaging is of great diagnostic value in neuroimaging. Three-dimensional (3D) Cartesian turbo spin echo (TSE) scans provide high signal-to-noise ratio (SNR) and contiguous slice coverage. The purpose of this preliminary work is to implement a novel 3D spiral TSE technique with image quality comparable to 2D/3D Cartesian TSE. METHODS The proposed technique uses multislab 3D TSE imaging. To mitigate the slice boundary artifacts, a sliding-slab method is extended to spiral imaging. A spiral-in/out readout is adopted to minimize the artifacts that may be present with the conventional spiral-out readout. Phase errors induced by B0 eddy currents are measured and compensated to allow for the combination of the spiral-in and spiral-out images. A nonuniform slice encoding scheme is used to reduce the truncation artifacts while preserving the SNR performance. RESULTS Preliminary results show that each of the individual measures contributes to the overall performance, and the image quality of the results obtained with the proposed technique is, in general, comparable to that of 2D or 3D Cartesian TSE. CONCLUSION 3D sliding-slab TSE with a spiral-in/out readout provides good-quality T2 -weighted images, and, therefore, may become a promising alternative to Cartesian TSE.
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Affiliation(s)
- Zhiqiang Li
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Dinghui Wang
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Ryan K Robison
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Nicholas R Zwart
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Michael Schär
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.,Philips Healthcare, Cleveland, Ohio, USA.,Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA
| | - John P Karis
- Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
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Li Z, Schär M, Wang D, Zwart NR, Madhuranthakam AJ, Karis JP, Pipe JG. Arterial spin labeled perfusion imaging using three-dimensional turbo spin echo with a distributed spiral-in/out trajectory. Magn Reson Med 2015; 75:266-73. [PMID: 25754947 DOI: 10.1002/mrm.25645] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 01/12/2015] [Accepted: 01/12/2015] [Indexed: 11/12/2022]
Abstract
PURPOSE The three-dimensional (3D) spiral turbo spin echo (TSE) sequence is one of the preferred readout methods for arterial spin labeled (ASL) perfusion imaging. Conventional spiral TSE collects the data using a spiral-out readout on a stack of spirals trajectory. However, it may result in suboptimal image quality and is not flexible in protocol design. The goal of this study is to provide a more robust readout technique without such limitation. METHODS The proposed technique incorporates a spiral-in/out readout into 3D TSE, and collects the data on a distributed spirals trajectory. The data set is split into the spiral-in and -out subsets that are reconstructed separately and combined after image deblurring. RESULTS The volunteer results acquired with the proposed technique show no geometric distortion or signal pileup, as is present with GRASE, and no signal loss, as is seen with conventional spiral TSE. Examples also demonstrate the flexibility in changing the imaging parameters to satisfy various criteria. CONCLUSION The 3D TSE with a distributed spiral-in/out trajectory provides a robust readout technique and allows for easy protocol design, thus is a promising alternative to GRASE or conventional spiral TSE for ASL perfusion imaging.
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Affiliation(s)
- Zhiqiang Li
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Michael Schär
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.,Philips Healthcare, Cleveland, Ohio, USA.,Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA
| | - Dinghui Wang
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Nicholas R Zwart
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Ananth J Madhuranthakam
- Department of Radiology and Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, USA
| | - John P Karis
- Neuroradiology, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
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Chang Y, Pipe JG, Karis JP, Gibbs WN, Zwart NR, Schär M. The effects of SENSE on PROPELLER imaging. Magn Reson Med 2014; 74:1598-608. [PMID: 25522132 DOI: 10.1002/mrm.25557] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 10/27/2014] [Accepted: 11/08/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE To study how sensitivity encoding (SENSE) impacts periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) image quality, including signal-to-noise ratio (SNR), robustness to motion, precision of motion estimation, and image quality. METHODS Five volunteers were imaged by three sets of scans. A rapid method for generating the g-factor map was proposed and validated via Monte Carlo simulations. Sensitivity maps were extrapolated to increase the area over which SENSE can be performed and therefore enhance the robustness to head motion. The precision of motion estimation of PROPELLER blades that are unfolded with these sensitivity maps was investigated. An interleaved R-factor PROPELLER sequence was used to acquire data with similar amounts of motion with and without SENSE acceleration. Two neuroradiologists independently and blindly compared 214 image pairs. RESULTS The proposed method of g-factor calculation was similar to that provided by the Monte Carlo methods. Extrapolation and rotation of the sensitivity maps allowed for continued robustness of SENSE unfolding in the presence of motion. SENSE-widened blades improved the precision of rotation and translation estimation. PROPELLER images with a SENSE factor of 3 outperformed the traditional PROPELLER images when reconstructing the same number of blades. CONCLUSION SENSE not only accelerates PROPELLER but can also improve robustness and precision of head motion correction, which improves overall image quality even when SNR is lost due to acceleration. The reduction of SNR, as a penalty of acceleration, is characterized by the proposed g-factor method.
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Affiliation(s)
- Yuchou Chang
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - John P Karis
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Wende N Gibbs
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Nicholas R Zwart
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Michael Schär
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.,Philips Healthcare, Cleveland, Ohio, USA.,Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA
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Zwart NR, Pipe JG. Graphical programming interface: A development environment for MRI methods. Magn Reson Med 2014; 74:1449-60. [PMID: 25385670 DOI: 10.1002/mrm.25528] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 10/17/2014] [Accepted: 10/20/2014] [Indexed: 11/05/2022]
Abstract
PURPOSE To introduce a multiplatform, Python language-based, development environment called graphical programming interface for prototyping MRI techniques. METHODS The interface allows developers to interact with their scientific algorithm prototypes visually in an event-driven environment making tasks such as parameterization, algorithm testing, data manipulation, and visualization an integrated part of the work-flow. Algorithm developers extend the built-in functionality through simple code interfaces designed to facilitate rapid implementation. RESULTS This article shows several examples of algorithms developed in graphical programming interface including the non-Cartesian MR reconstruction algorithms for PROPELLER and spiral as well as spin simulation and trajectory visualization of a FLORET example. CONCLUSION The graphical programming interface framework is shown to be a versatile prototyping environment for developing numeric algorithms used in the latest MR techniques.
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Affiliation(s)
- Nicholas R Zwart
- Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, Arizona, USA
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Pipe JG, Gibbs WN, Li Z, Karis JP, Schar M, Zwart NR. Revised motion estimation algorithm for PROPELLER MRI. Magn Reson Med 2013; 72:430-7. [PMID: 24006354 DOI: 10.1002/mrm.24929] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 07/24/2013] [Accepted: 07/29/2013] [Indexed: 11/08/2022]
Abstract
PURPOSE To introduce a new algorithm for estimating data shifts (used for both rotation and translation estimates) for motion-corrected PROPELLER MRI. The method estimates shifts for all blades jointly, emphasizing blade-pair correlations that are both strong and more robust to noise. THEORY AND METHODS The heads of three volunteers were scanned using a PROPELLER acquisition while they exhibited various amounts of motion. All data were reconstructed twice, using motion estimates from the original and new algorithm. Two radiologists independently and blindly compared 216 image pairs from these scans, ranking the left image as substantially better or worse than, slightly better or worse than, or equivalent to the right image. RESULTS In the aggregate of 432 scores, the new method was judged substantially better than the old method 11 times, and was never judged substantially worse. CONCLUSION The new algorithm compared favorably with the old in its ability to estimate bulk motion in a limited study of volunteer motion. A larger study of patients is planned for future work.
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Affiliation(s)
- James G Pipe
- Barrow Neurological Institute, Phoenix, Arizona, USA
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35
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Affiliation(s)
- Payal S. Bhavsar
- Keller Center for Imaging Innovation; Barrow Neurological Institute; Phoenix Arizona USA
| | - Nicholas R. Zwart
- Keller Center for Imaging Innovation; Barrow Neurological Institute; Phoenix Arizona USA
| | - James G. Pipe
- Keller Center for Imaging Innovation; Barrow Neurological Institute; Phoenix Arizona USA
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36
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Pipe JG, Zwart NR. Spiral trajectory design: a flexible numerical algorithm and base analytical equations. Magn Reson Med 2013; 71:278-85. [PMID: 23440770 DOI: 10.1002/mrm.24675] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 12/06/2012] [Accepted: 01/11/2013] [Indexed: 11/10/2022]
Abstract
PURPOSE Spiral-based trajectories for magnetic resonance imaging can be advantageous, but are often cumbersome to design or create. This work presents a flexible numerical algorithm for designing trajectories based on explicit definition of radial undersampling, and also gives several analytical expressions for charactering the base (critically sampled) class of these trajectories. THEORY AND METHODS Expressions for the gradient waveform, based on slew and amplitude limits, are developed such that a desired pitch in the spiral k-space trajectory is followed. The source code for this algorithm, written in C, is publicly available. Analytical expressions approximating the spiral trajectory (ignoring the radial component) are given to characterize measurement time, gradient heating, maximum gradient amplitude, and off-resonance phase for slew-limited and gradient amplitude-limited cases. Several numerically calculated trajectories are illustrated, and base Archimedean spirals are compared with analytically obtained results. RESULTS Several different waveforms illustrate that the desired slew and amplitude limits are reached, as are the desired undersampling patterns, using the numerical method. For base Archimedean spirals, the results of the numerical and analytical approaches are in good agreement. CONCLUSION A versatile numerical algorithm was developed, and was written in publicly available code. Approximate analytical formulas are given that help characterize spiral trajectories.
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Affiliation(s)
- James G Pipe
- Barrow Neurological Institute, Phoenix, Arizona, USA
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37
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Roher AE, Debbins JP, Malek-Ahmadi M, Chen K, Pipe JG, Maze S, Belden C, Maarouf CL, Thiyyagura P, Mo H, Hunter JM, Kokjohn TA, Walker DG, Kruchowsky JC, Belohlavek M, Sabbagh MN, Beach TG. Cerebral blood flow in Alzheimer's disease. Vasc Health Risk Manag 2012; 8:599-611. [PMID: 23109807 PMCID: PMC3481957 DOI: 10.2147/vhrm.s34874] [Citation(s) in RCA: 128] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Alzheimer’s disease (AD) dementia is a consequence of heterogeneous and complex interactions of age-related neurodegeneration and vascular-associated pathologies. Evidence has accumulated that there is increased atherosclerosis/arteriosclerosis of the intracranial arteries in AD and that this may be additive or synergistic with respect to the generation of hypoxia/ischemia and cognitive dysfunction. The effectiveness of pharmacologic therapies and lifestyle modification in reducing cardiovascular disease has prompted a reconsideration of the roles that cardiovascular disease and cerebrovascular function play in the pathogenesis of dementia. Methods Using two-dimensional phase-contrast magnetic resonance imaging, we quantified cerebral blood flow within the internal carotid, basilar, and middle cerebral arteries in a group of individuals with mild to moderate AD (n = 8) and compared the results with those from a group of age-matched nondemented control (NDC) subjects (n = 9). Clinical and psychometric testing was performed on all individuals, as well as obtaining their magnetic resonance imaging-based hippocampal volumes. Results Our experiments reveal that total cerebral blood flow was 20% lower in the AD group than in the NDC group, and that these values were directly correlated with pulse pressure and cognitive measures. The AD group had a significantly lower pulse pressure (mean AD 48, mean NDC 71; P = 0.0004). A significant group difference was also observed in their hippocampal volumes. Composite z-scores for clinical, psychometric, hippocampal volume, and hemodynamic data differed between the AD and NDC subjects, with values in the former being significantly lower (t = 12.00, df = 1, P = 0.001) than in the latter. Conclusion These results indicate an association between brain hypoperfusion and the dementia of AD. Cardiovascular disease combined with brain hypoperfusion may participate in the pathogenesis/pathophysiology of neurodegenerative diseases. Future longitudinal and larger-scale confirmatory investigations measuring multidomain parameters are warranted.
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Affiliation(s)
- Alex E Roher
- The Longtine Center for Neurodegenerative Biochemistry, Banner Sun Health Research Institute, Sun City, AZ 85351, USA.
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Turley DC, Pipe JG. Distributed spirals: a new class of three-dimensional k-space trajectories. Magn Reson Med 2012; 70:413-9. [PMID: 23042669 DOI: 10.1002/mrm.24475] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 08/01/2012] [Accepted: 08/07/2012] [Indexed: 11/10/2022]
Abstract
This work presents a new class of three-dimensional spiral based-trajectories for sampling magnetic resonance data. The distributed spirals trajectory efficiently traverses a cylinder or sphere or intermediate shape in k-space. The trajectory is shown to be nearly as efficient as a conventional stack of spirals trajectory in terms of scan time and signal-to-noise ratio, while reducing coherent aliasing in all three spatial directions and reducing Gibbs ringing due to the nature of collecting data from a sphere in k-space. The trajectory uses a single two-dimensional spiral waveform with the addition of a single orthogonal waveform which is scaled with each repetition, making it relatively easy to implement. Blurring from off-resonance only occurs in two dimensions due to the temporal nature of the sampling.
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Lee CY, Li Z, Pipe JG, Debbins JP. Turboprop+: enhanced Turboprop diffusion-weighted imaging with a new phase correction. Magn Reson Med 2012; 70:497-503. [PMID: 23023533 DOI: 10.1002/mrm.24481] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 08/13/2012] [Accepted: 08/13/2012] [Indexed: 01/01/2023]
Abstract
Faster periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted imaging acquisitions, such as Turboprop and X-prop, remain subject to phase errors inherent to a gradient echo readout, which ultimately limits the applied turbo factor (number of gradient echoes between each pair of radiofrequency refocusing pulses) and, thus, scan time reductions. This study introduces a new phase correction to Turboprop, called Turboprop+. This technique employs calibration blades, which generate 2-D phase error maps and are rotated in accordance with the data blades, to correct phase errors arising from off-resonance and system imperfections. The results demonstrate that with a small increase in scan time for collecting calibration blades, Turboprop+ had a superior immunity to the off-resonance-related artifacts when compared to standard Turboprop and recently proposed X-prop with the high turbo factor (turbo factor = 7). Thus, low specific absorption rate and short scan time can be achieved in Turboprop+ using a high turbo factor, whereas off-resonance related artifacts are minimized.
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Affiliation(s)
- Chu-Yu Lee
- School of Electrical, Computer, and Energy Engineering, Ira A, Fulton School of Engineering, Arizona State University, Tempe, Arizona, USA
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Zwart NR, Pipe JG. Multidirectional high-moment encoding in phase contrast MRI. Magn Reson Med 2012; 69:1553-64. [PMID: 22760964 DOI: 10.1002/mrm.24390] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 05/31/2012] [Accepted: 06/04/2012] [Indexed: 11/08/2022]
Abstract
The use of phase contrast MRI to measure vascular flow provides a unique method for acquiring quantitative estimates of flow as well as morphological imaging. The quantitative aspects of phase contrast magnetic resonance angiography (PC-MRA) provide unique relationships between measurement parameters and resulting signal to noise ratio of the velocity measurements. This article introduces a new method to exploit these relationships providing increased efficiency, and therefore, higher vessel conspicuity. Signal to noise ratio gains in high-moment PC-MRA are limited by the ability to unalias phase measurements that fall outside the -π to π interval. Unaliasing phase on a per pixel basis is limited by errors in the measurements due to noise and intravoxel flow distributions. Current dual-VENC methods have been shown to be robust to these errors and provide high velocity to noise ratio gains, however, the collection of a required high-VENC set can be inefficient. The presented method provides more time efficient gains in velocity to noise ratio compared to a dual-VENC approach by eliminating the high-VENC acquisitions and using shared information between nonorthogonal measurements. Simulations, phantom, and in vivo angiography are used to characterize the noise performance of each method. The velocity to noise ratio efficiency of the proposed method is shown to be ∼1.7 times greater than the dual-VENC method at the same gradient moment.
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Affiliation(s)
- Nicholas R Zwart
- Department of Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona 85013, USA.
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Zwart NR, Johnson KO, Pipe JG. Efficient sample density estimation by combining gridding and an optimized kernel. Magn Reson Med 2011; 67:701-10. [PMID: 21688320 DOI: 10.1002/mrm.23041] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 03/30/2011] [Accepted: 05/18/2011] [Indexed: 11/07/2022]
Abstract
The reconstruction of non-Cartesian k-space trajectories often requires the estimation of nonuniform sampling density. Particularly for 3D, this calculation can be computationally expensive. The method proposed in this work combines an iterative algorithm previously proposed by Pipe and Menon (Magn Reson Med 1999;41:179-186) with the optimal kernel design previously proposed by Johnson and Pipe (Magn Reson Med 2009;61:439-447). The proposed method shows substantial time reductions in estimating the densities of center-out trajectories, when compared with that of Johnson. It is demonstrated that, depending on the trajectory, the proposed method can provide reductions in execution time by factors of 12 to 85. The method is also shown to be robust in areas of high trajectory overlap, when compared with two analytical density estimation methods, producing a 10-fold increase in accuracy in one case. Initial conditions allow the proposed method to converge in fewer iterations and are shown to be flexible in terms of the accuracy of information supplied. The proposed method is not only one of the fastest and most accurate algorithms, it is also completely generic, allowing any arbitrary trajectory to be density compensated extemporaneously. The proposed method is also simple and can be implemented on parallel computing platforms in a straightforward manner.
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Affiliation(s)
- Nicholas R Zwart
- Keller Center for Imaging Innovation, Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona 85013, USA.
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Li Z, Pipe JG, Lee CY, Debbins JP, Karis JP, Huo D. X-PROP: A fast and robust diffusion-weighted propeller technique. Magn Reson Med 2011; 66:341-7. [DOI: 10.1002/mrm.23033] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 04/18/2011] [Accepted: 05/07/2011] [Indexed: 11/10/2022]
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Pipe JG, Zwart NR, Aboussouan EA, Robison RK, Devaraj A, Johnson KO. A new design and rationale for 3D orthogonally oversampled k
-space trajectories. Magn Reson Med 2011; 66:1303-11. [DOI: 10.1002/mrm.22918] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Revised: 01/28/2011] [Accepted: 02/18/2011] [Indexed: 11/10/2022]
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Abstract
Spiral projection imaging (SPI) is a 3D, spiral based magnetic resonance imaging (MRI) acquisition scheme that allows for self-navigated motion estimation of all six degrees-of-freedom. The trajectory, a set of spiral planes, is enhanced to accommodate motion tracking by adding orthogonal planes. Rigid-body motion tracking is accomplished by comparing the overlapping data and deducing the motion that is consistent with the comparisons. The accuracy of the proposed method is quantified for simulated data and for data collected using both a phantom and a volunteer. These tests were repeated to measure the effect of off-resonance blurring, coil sensitivity, gradient warping, undersampling, and nonrigid motion (e.g., neck). The artifacts of off-resonance, coils sensitivity, and gradient warping impose an unnotable effect on the accuracy of motion estimation. The worst mean accuracy is 0.15° and 0.20 mm for the phantom while the worst mean accuracy is 0.48° and 0.34 mm when imaging a brain, indicating that the nonrigid component in human subjects slightly degrades accuracy. When applied to in vivo motion, the proposed technique considerably reduces motion artifact.
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Affiliation(s)
- Kenneth O Johnson
- Keller Center for Imaging Innvation, Barrow Neurological Institute, Phoenix, AZ 85013, USA
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Li Z, Pipe JG, Aboussouan E, Karis JP, Huo D. A parallel imaging technique using mutual calibration for split-blade diffusion-weighted PROPELLER. Magn Reson Med 2010; 65:638-44. [DOI: 10.1002/mrm.22646] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Revised: 08/04/2010] [Accepted: 08/26/2010] [Indexed: 11/10/2022]
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Abstract
Timing delays between data acquisition and gradient transmission result in image degradation. This is especially true in spiral MRI, where delays can alter data in a nonuniform manner, generating significant artifact in the reconstructed data. The many methods that exist to mitigate these delays or measure the k-space coordinates require long measurement times, complicated analysis, specialized phantoms or hardware, or significant changes to the sequence of interest. A fast and simple method is proposed to measure delays on each gradient channel. It requires only minimal modification to an existing spiral sequence and can be used to measure independent delays on three gradient channels and any scan subject within six sequence repetition times. The effectiveness and accuracy of this method are analyzed.
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Affiliation(s)
- Ryan K Robison
- Keller Center for Imaging Innovation, Barrow Neurological Institute, 350 West Thomas Rd., Phoenix, Arizona 85013, USA.
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Abstract
Traditionally two-dimensional scans are designed to support an isotropic field-of-view (iFOV). When imaging elongated objects, significant savings in scan time can potentially be achieved by supporting an elliptical field-of-view (eFOV). This work presents an empirical closed-form solution to adapt the PROPELLER trajectory for an eFOV. The proposed solution is built on the geometry of the PROPELLER trajectory permitting the scan prescription and data reconstruction to remain largely similar to standard PROPELLER. The achieved FOV is experimentally validated by the point spread function (PSF) of a phantom scan. The details of potential savings in scan time and the signal-to-noise ratio (SNR) performance in comparison to iFOV scans for both phantom and in-vivo images are also described.
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Affiliation(s)
- Ajit Devaraj
- Department of Electrical Engineering, Arizona State University, Tempe, Arizona, USA.
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Abstract
Sampling density compensation is an important step in non-cartesian image reconstruction. One of the common techniques to determine weights that compensate for differences in sampling density involves a convolution. A new convolution kernel is designed for sampling density attempting to minimize the error in a fully reconstructed image. The resulting weights obtained using this new kernel are compared with various previous methods, showing a reduction in reconstruction error. A computationally efficient algorithm is also presented that facilitates the calculation of the convolution of finite kernels. Both the kernel and the algorithm are extended to 3D.
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Affiliation(s)
- Kenneth O Johnson
- Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, Arizona 85013, USA.
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Abstract
Suppression of the fat signal in MRI is very important for many clinical applications. Multi-point water-fat separation methods, such as IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation), can robustly separate water and fat signal, but inevitably increase scan time, making separated images more easily affected by patient motions. PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) and Turboprop techniques offer an effective approach to correct for motion artifacts. By combining these techniques together, we demonstrate that the new TP-IDEAL method can provide reliable water-fat separation with robust motion correction. The Turboprop sequence was modified to acquire source images, and motion correction algorithms were adjusted to assure the registration between different echo images. Theoretical calculations were performed to predict the optimal shift and spacing of the gradient echoes. Phantom images were acquired, and results were compared with regular FSE-IDEAL. Both T1- and T2-weighted images of the human brain were used to demonstrate the effectiveness of motion correction. TP-IDEAL images were also acquired for pelvis, knee, and foot, showing great potential of this technique for general clinical applications.
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Affiliation(s)
- Donglai Huo
- Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, Arizona 85013, USA.
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