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Stecker IR, Bdaiwi AS, Niedbalski PJ, Chatterjee N, Hossain MM, Cleveland ZI. Impact of undersampling on preclinical lung T 2* mapping with 3D radial UTE MRI at 7 T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 365:107741. [PMID: 39089222 PMCID: PMC11357708 DOI: 10.1016/j.jmr.2024.107741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 06/28/2024] [Accepted: 07/11/2024] [Indexed: 08/03/2024]
Abstract
Lung diseases are almost invariably heterogeneous and progressive, making it imperative to capture temporally and spatially explicit information to understand the disease initiation and progression. Imaging the lung with MRI-particularly in the preclinical setting-has historically been challenging because of relatively low lung tissue density, rapid cardiac and respiratory motion, and rapid transverse (T2*) relaxation. These limitations can largely be mitigated using ultrashort-echo-time (UTE) sequences, which are intrinsically robust to motion and avoid significant T2* decay. A significant disadvantage of common radial UTE sequences is that they require inefficient, center-out k-space sampling, resulting in long acquisition times relative to conventional Cartesian sequences. Therefore, pulmonary images acquired with radial UTE are often undersampled to reduce acquisition time. However, undersampling reduces image SNR, introduces image artifacts, and degrades true image resolution. The level of undersampling is further increased if offline gating techniques like retrospective gating are employed, because only a portion (∼40-50%) of the data is used in the final image reconstruction. Here, we explore the impact of undersampling on SNR and T2* mapping in mouse lung imaging using simulation and in-vivo data. Increased scatter in both metrics was noticeable at around 50% sampling. Parenchymal apparent SNR only decreased slightly (average decrease ∼ 1.4) with as little as 10% sampling. Apparent T2* remained similar across undersampling levels, but it became significantly increased (p < 0.05) below 80% sampling. These trends suggest that undersampling can generate quantifiable, but moderate changes in the apparent value of T2*. Moreover, these approaches to assess the impact of undersampling are straightforward to implement and can readily be expanded to assess the quantitative impact of other MR acquisition and reconstruction parameters.
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Affiliation(s)
- Ian R Stecker
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States; Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Abdullah S Bdaiwi
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States; Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Peter J Niedbalski
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Neelakshi Chatterjee
- Division of Biostatistics and Bioinformatics, Department of Environmental and Public Health Sciences, College of Medicine, University of Cincinnati, Cincinnati, OH, United States; Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Md M Hossain
- Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; Department of Pediatrics, University of Cincinnati, Cincinnati, OH, United States
| | - Zackary I Cleveland
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States; Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; Department of Pediatrics, University of Cincinnati, Cincinnati, OH, United States; Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.
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2
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Nyman JS, Ketsiri T, Louie EA, Harkins KD, Manhard MK, Gochberg DF, Lee DH, Desai MJ, Maslow J, Tanner SB, Does MD. Toward the use of MRI measurements of bound and pore water in fracture risk assessment. Bone 2023; 176:116863. [PMID: 37527697 PMCID: PMC10528882 DOI: 10.1016/j.bone.2023.116863] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/26/2023] [Accepted: 07/28/2023] [Indexed: 08/03/2023]
Abstract
The current clinical assessment of fracture risk lacks information about the inherent quality of a person's bone tissue. Working toward an imaging-based approach to quantify both a bone tissue quality marker (tissue hydration as water bound to the matrix) and a bone microstructure marker (porosity as water in pores), we hypothesized that the concentrations of bound water (Cbw) are lower and concentrations of pore water (Cpw) are higher in patients with osteoporosis (OP) than in age- and sex-matched adults without the disease. Using recent developments in ultrashort echo time (UTE) magnetic resonance imaging (MRI), maps of Cbw and Cpw were acquired from the uninjured distal third radius (Study 1) of 20 patients who experienced a fragility fracture of the distal radius (Fx) and 20 healthy controls (Non-Fx) and from the tibia mid-diaphysis (Study 2) of 30 women with clinical OP (low T-scores) and 15 women without OP (normal T-scores). In Study 1, Cbw was significantly lower (p = 0.0018) and Cpw was higher (p = 0.0022) in the Fx than in the Non-Fx group. In forward stepwise, logistic regression models using Bayesian Information Criterion for selecting the best set of predictors (from imaging parameters, age, BMI, and DXA scanner type), the area-under-the-receiver operator characteristics-curve (AUC with 95 % confidence intervals) was 0.73 (0.56, 0.86) for hip aBMD (best predictors without MRI) and 0.86 (0.70, 0.95) for the combination of Cbw and Cpw (best predictors overall). In Study 2, Cbw was significantly lower (p = 0.0005) in women with OP (23.8 ± 4.3 1H mol/L) than in women without OP (29.9 ± 6.4 1H mol/L); Cpw was significantly higher by estimate of 2.9 1H mol/L (p = 0.0298) with clinical OP, but only when accounting for the type of UTE-MRI scan with 3D providing higher values than 2D (p < 0.0001). Lastly, Cbw, but not Cpw, was sensitive to bone forming osteoporosis medications over 12-months. UTE-MRI-derived measurements of bound and pore water concentrations are potential, aBMD-independent predictors of fracture risk.
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Affiliation(s)
- Jeffry S Nyman
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA; Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Department of Veterans Affairs, Tennessee Valley Healthcare System, 1310 24th Ave. S., Nashville, TN 37212, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center,1211 Medical Center Dr., Nashville, TN 37212, USA.
| | - Thammathida Ketsiri
- Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Elizabeth A Louie
- Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Kevin D Harkins
- Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Mary Kate Manhard
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229, USA
| | - Daniel F Gochberg
- Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Donald H Lee
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA
| | - Mihir J Desai
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA
| | - Jed Maslow
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA
| | - S Bobo Tanner
- Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center,1211 Medical Center Dr., Nashville, TN 37212, USA; Department of Medicine, Division of Rheumatology, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Electrical Engineering and Computer Science, Vanderbilt University, 400 24th Ave. S., Nashville, TN 37212, USA.
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Dwork N, O'Connor D, Johnson EMI, Baron CA, Gordon JW, Pauly JM, Larson PEZ. Optimization in the space domain for density compensation with the nonuniform FFT. Magn Reson Imaging 2023; 100:102-111. [PMID: 36934830 PMCID: PMC10288563 DOI: 10.1016/j.mri.2023.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 03/02/2023] [Accepted: 03/12/2023] [Indexed: 03/19/2023]
Abstract
The non-uniform Discrete Fourier Transform algorithm has shown great utility for reconstructing images from non-uniformly spaced Fourier samples in several imaging modalities. Due to the non-uniform spacing, some correction for the variable density of the samples must be made. Common methods for generating density compensation values are either sub-optimal or only consider a finite set of points in the optimization. This manuscript presents an algorithm for generating density compensation values from a set of Fourier samples that takes into account the point spread function over an entire rectangular region in the image domain. We show that the reconstructed images using the density compensation values of this method are of superior quality when compared to other standard methods. Results are shown with a numerical phantom and with magnetic resonance images of the abdomen and the knee.
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Affiliation(s)
- Nicholas Dwork
- Biomedical Informatics and Radiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
| | - Daniel O'Connor
- Mathematics and Statistics, University of San Francisco, San Francisco, CA, USA
| | | | - Corey A Baron
- Center for Functional and Metabolic Mapping, Western University, Ontario, Canada
| | - Jeremy W Gordon
- Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94158, USA
| | - John M Pauly
- Electrical Engineering Department, Stanford University, Palo Alto, CA, USA
| | - Peder E Z Larson
- Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94158, USA
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Ketsiri T, Uppuganti S, Harkins KD, Gochberg DF, Nyman JS, Does MD. Finite element analysis of bone mechanical properties using MRI-derived bound and pore water concentration maps. Comput Methods Biomech Biomed Engin 2023; 26:905-916. [PMID: 35822868 PMCID: PMC9837311 DOI: 10.1080/10255842.2022.2098016] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 06/10/2022] [Accepted: 06/30/2022] [Indexed: 01/17/2023]
Abstract
Ultrashort echo time (UTE) MRI techniques can be used to image the concentration of water in bones. Particularly, quantitative MRI imaging of collagen-bound water concentration (Cbw) and pore water concentration (Cpw) in cortical bone have been shown as potential biomarkers for bone fracture risk. To investigate the effect of Cbw and Cpw on the evaluation of bone mechanical properties, MRI-based finite element models of cadaver radii were generated with tissue material properties derived from 3 D maps of Cbw and Cpw measurements. Three-point bending tests were simulated by means of the finite element method to predict bending properties of the bone and the results were compared with those from direct mechanical testing. The study results demonstrate that these MRI-derived measures of Cbw and Cpw improve the prediction of bone mechanical properties in cadaver radii and have the potential to be useful in assessing patient-specific bone fragility risk.
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Affiliation(s)
- Thammathida Ketsiri
- Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States
| | - Sasidhar Uppuganti
- Department of Orthopaedic Surgery & Rehabilitation, Vanderbilt University, Nashville, TN, United States
- Tennessee Valley Healthcare System, Department of Veterans Affairs, Nashville, TN, United States
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Kevin D. Harkins
- Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States
- Radiology & Radiological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States
- Radiology & Radiological Sciences, Vanderbilt University, Nashville, TN, United States
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States
| | - Jeffry S. Nyman
- Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States
- Department of Orthopaedic Surgery & Rehabilitation, Vanderbilt University, Nashville, TN, United States
- Tennessee Valley Healthcare System, Department of Veterans Affairs, Nashville, TN, United States
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Mark D. Does
- Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States
- Radiology & Radiological Sciences, Vanderbilt University, Nashville, TN, United States
- Electrical Engineering, Vanderbilt University, Nashville, TN, United States
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5
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Subashi E, Feng L, Liu Y, Robertson S, Segars P, Driehuys B, Kelsey CR, Yin FF, Otazo R, Cai J. View-sharing for 4D magnetic resonance imaging with randomized projection-encoding enables improvements of respiratory motion imaging for treatment planning in abdominothoracic radiotherapy. Phys Imaging Radiat Oncol 2023; 25:100409. [PMID: 36655213 PMCID: PMC9841273 DOI: 10.1016/j.phro.2022.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 12/24/2022] [Accepted: 12/28/2022] [Indexed: 01/03/2023] Open
Abstract
Background and Purpose The accuracy and precision of radiation therapy are dependent on the characterization of organ-at-risk and target motion. This work aims to demonstrate a 4D magnetic resonance imaging (MRI) method for improving spatial and temporal resolution in respiratory motion imaging for treatment planning in abdominothoracic radiotherapy. Materials and Methods The spatial and temporal resolution of phase-resolved respiratory imaging is improved by considering a novel sampling function based on quasi-random projection-encoding and peripheral k-space view-sharing. The respiratory signal is determined directly from k-space, obviating the need for an external surrogate marker. The average breathing curve is used to optimize spatial resolution and temporal blurring by limiting the extent of data sharing in the Fourier domain. Improvements in image quality are characterized by evaluating changes in signal-to-noise ratio (SNR), resolution, target detection, and level of artifact. The method is validated in simulations, in a dynamic phantom, and in-vivo imaging. Results Sharing of high-frequency k-space data, driven by the average breathing curve, improves spatial resolution and reduces artifacts. Although equal sharing of k-space data improves resolution and SNR in stationary features, phases with large temporal changes accumulate significant artifacts due to averaging of high frequency features. In the absence of view-sharing, no averaging and detection artifacts are observed while spatial resolution is degraded. Conclusions The use of a quasi-random sampling function, with view-sharing driven by the average breathing curve, provides a feasible method for self-navigated 4D-MRI at improved spatial resolution.
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Affiliation(s)
- Ergys Subashi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | - Li Feng
- Biomedical Engineering and Imaging Institute, Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Yilin Liu
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | - Scott Robertson
- Medical Physics Graduate Program, Duke University Medical Center, Durham, NC, United States
- Department of Radiology, Duke University Medical Center, Durham, NC, United States
| | - Paul Segars
- Medical Physics Graduate Program, Duke University Medical Center, Durham, NC, United States
- Department of Radiology, Duke University Medical Center, Durham, NC, United States
| | - Bastiaan Driehuys
- Medical Physics Graduate Program, Duke University Medical Center, Durham, NC, United States
- Department of Radiology, Duke University Medical Center, Durham, NC, United States
| | - Christopher R Kelsey
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, United States
| | - Fang-Fang Yin
- Medical Physics Graduate Program, Duke University Medical Center, Durham, NC, United States
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, United States
| | - Ricardo Otazo
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | - Jing Cai
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong
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Stecker IR, Freeman MS, Sitaraman S, Hall CS, Niedbalski PJ, Hendricks AJ, Martin EP, Weaver TE, Cleveland ZI. Preclinical MRI to Quantify Pulmonary Disease Severity and Trajectories in Poorly Characterized Mouse Models: A Pedagogical Example Using Data from Novel Transgenic Models of Lung Fibrosis. JOURNAL OF MAGNETIC RESONANCE OPEN 2021; 6-7. [PMID: 34414381 PMCID: PMC8372031 DOI: 10.1016/j.jmro.2021.100013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Structural remodeling in lung disease is progressive and heterogeneous, making temporally and spatially explicit information necessary to understand disease initiation and progression. While mouse models are essential to elucidate mechanistic pathways underlying disease, the experimental tools commonly available to quantify lung disease burden are typically invasive (e.g., histology). This necessitates large cross-sectional studies with terminal endpoints, which increases experimental complexity and expense. Alternatively, magnetic resonance imaging (MRI) provides information noninvasively, thus permitting robust, repeated-measures statistics. Although lung MRI is challenging due to low tissue density and rapid apparent transverse relaxation (T2* <1 ms), various imaging methods have been proposed to quantify disease burden. However, there are no widely accepted strategies for preclinical lung MRI. As such, it can be difficult for researchers who lack lung imaging expertise to design experimental protocols-particularly for novel mouse models. Here, we build upon prior work from several research groups to describe a widely applicable acquisition and analysis pipeline that can be implemented without prior preclinical pulmonary MRI experience. Our approach utilizes 3D radial ultrashort echo time (UTE) MRI with retrospective gating and lung segmentation is facilitated with a deep-learning algorithm. This pipeline was deployed to assess disease dynamics over 255 days in novel, transgenic mouse models of lung fibrosis based on disease-associated, loss-of-function mutations in Surfactant Protein-C. Previously identified imaging biomarkers (tidal volume, signal coefficient of variation, etc.) were calculated semi-automatically from these data, with an objectively-defined high signal volume identified as the most robust metric. Beyond quantifying disease dynamics, we discuss common pitfalls encountered in preclinical lung MRI and present systematic approaches to identify and mitigate these challenges. While the experimental results and specific pedagogical examples are confined to lung fibrosis, the tools and approaches presented should be broadly useful to quantify structural lung disease in a wide range of mouse models.
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Affiliation(s)
- Ian R Stecker
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Matthew S Freeman
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Sneha Sitaraman
- Division of Neonatology and Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Chase S Hall
- Division of Pulmonary and Critical Care, University of Kansas Medical Center, Kansas City, KS 66160
| | - Peter J Niedbalski
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
- Division of Pulmonary and Critical Care, University of Kansas Medical Center, Kansas City, KS 66160
| | - Alexandra J Hendricks
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Emily P Martin
- Division of Neonatology and Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Timothy E Weaver
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45221
- Division of Neonatology and Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Zackary I Cleveland
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45221
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Jang H, McMillan AB, Ma Y, Jerban S, Chang EY, Du J, Kijowski R. Rapid single scan ramped hybrid-encoding for bicomponent T2* mapping in a human knee joint: A feasibility study. NMR IN BIOMEDICINE 2020; 33:e4391. [PMID: 32761692 PMCID: PMC7584401 DOI: 10.1002/nbm.4391] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 06/20/2020] [Accepted: 07/21/2020] [Indexed: 05/03/2023]
Abstract
The purpose of this study is to determine the feasibility of using a single scan ramped hybrid-encoding (RHE) method for rapid bicomponent T2* analysis of the human knee joint. The proposed method utilizes RHE to acquire ultrashort echo time (UTE) and subsequent gradient echo images at 16 different echo times ranging between 40 μs and 30 ms in a single scan. In the proposed RHE technique, UTE imaging was followed by acquisition of 14 gradient recalled echo images, where an additional UTE image was obtained within the first readout by oversampling single point imaging (SPI) encoding. The single scan RHE method with a 9-minute scan time was performed on human cadaveric knee joints from six donors and in vivo knee joints from four healthy volunteers at 3 T. A bicomponent signal model was used to characterize the short T2* and long T2* water components. Mean bicomponent T2* parameters for patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL) and meniscus were calculated. In the experimental results, the RHE technique provided bicomponent T2* parameter estimations of tendon, ACL, PCL and meniscus, which were similar to previously reported values in the literature. In conclusion, the proposed single scan RHE technique provides rapid bicomponent T2* analysis of the human knee joint with a total scan time of less than 9 minutes.
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Affiliation(s)
- Hyungseok Jang
- Department of Radiology, University of California San Diego, San Diego, CA 92103, USA
- Corresponding Author: Hyungseok Jang, Ph.D., University of California, San Diego, Department of Radiology, 200 West Arbor Drive, San Diego, CA 92103-8226, Phone (858) 246-2225,
| | - Alan B McMillan
- Department of Radiology, University of Wisconsin Madison, Madison, WI 53705, USA
| | - Yajun Ma
- Department of Radiology, University of California San Diego, San Diego, CA 92103, USA
| | - Saeed Jerban
- Department of Radiology, University of California San Diego, San Diego, CA 92103, USA
| | - Eric Y Chang
- Department of Radiology, University of California San Diego, San Diego, CA 92103, USA
- Radiology Service, VA San Diego Healthcare System, San Diego, CA 92037, USA
| | - Jiang Du
- Department of Radiology, University of California San Diego, San Diego, CA 92103, USA
| | - Richard Kijowski
- Department of Radiology, University of Wisconsin Madison, Madison, WI 53705, USA
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8
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Weiger M, Pruessmann KP. Short-T 2 MRI: Principles and recent advances. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:237-270. [PMID: 31779882 DOI: 10.1016/j.pnmrs.2019.07.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/14/2019] [Accepted: 07/26/2019] [Indexed: 06/10/2023]
Abstract
Among current modalities of biomedical and diagnostic imaging, MRI stands out by virtue of its versatile contrast obtained without ionizing radiation. However, in various cases, e.g., water protons in tissues such as bone, tendon, and lung, MRI performance is limited by the rapid decay of resonance signals associated with short transverse relaxation times T2 or T2*. Efforts to address this shortcoming have led to a variety of specialized short-T2 techniques. Recent progress in this field expands the choice of methods and prompts fresh considerations with regard to instrumentation, data acquisition, and signal processing. In this review, the current status of short-T2 MRI is surveyed. In an attempt to structure the growing range of techniques, the presentation highlights overarching concepts and basic methodological options. The most frequently used approaches are described in detail, including acquisition strategies, image reconstruction, hardware requirements, means of introducing contrast, sources of artifacts, limitations, and applications.
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Affiliation(s)
- Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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9
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Jeong KE, Hsu EW, Jeong EK. Diffusion MRI using two-dimensional single-shot radial imaging (2D ss-rDWI) with variable flip angle and random view ordering. Magn Reson Imaging 2019; 61:273-284. [PMID: 31009689 DOI: 10.1016/j.mri.2019.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/21/2019] [Accepted: 04/17/2019] [Indexed: 12/25/2022]
Abstract
PURPOSE The main objective of this study is to develop a 2D single-shot radial-DWI (2D ss-rDWI) technique to reduce motion artifacts and geometric distortion in DW images. METHOD A diffusion-preparation module is developed and applied prior to the data acquisition. Because the diffusion-prepared longitudinal magnetization is measured over multiple RF excitations in each shot, 2D ss-rDWI is subject to low signal-to-noise ratio (SNR). We used variable-flip angle (VFA), random view ordering (RVO), and sliding spokes, and compared the performances to constant flip angle (CFA), smooth view ordering (SVO), and identical spoke averaging, respectively. For each technique, we performed numerical simulation and MRI experiments on a fluid phantom as well as in-vivo human brain studies with a 3 T MRI system. RESULTS Using VFA, optimal SNR was acquired for 2D ss-rDWI. Using SVO, the high signal is clustered at specific quadrant in 2D k-space: the first quadrant using high initial flip angle or the last quadrant using the low flip angle. This clustered signal in k-space led to geometric distortion in image space. 2D ss-rDWI using RVO spreads the high signaled spokes over all angular directions and removes the view-order-related distortion. The in-vivo images using 2D ss-rDWI with VFA and RVO show no geometric distortion at the skull base brain, but greatly reduced SNR compared with those using 2D ss-DWEPI. CONCLUSION 2D ss-rDWI is optimized by using VFA with RVO. The resultant DWI using 2D ss-rDWI is insensitive to motion-induced artifacts and geometric distortion. Even with low SNR, it may be useful for DWI of organs limited by severe susceptibility-induced geometric distortion.
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Affiliation(s)
- Kyle E Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States of America; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States of America
| | - Edward W Hsu
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States of America
| | - Eun-Kee Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States of America; Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States of America.
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10
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Guo J, Hardie WD, Cleveland ZI, Davidson C, Xu X, Madala SK, Woods JC. Longitudinal free-breathing MRI measurement of murine lung physiology in a progressive model of lung fibrosis. J Appl Physiol (1985) 2019; 126:1138-1149. [PMID: 30730810 DOI: 10.1152/japplphysiol.00993.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
To longitudinally monitor progressive fibrosis in the transforming growth factor-α (TGF-α) transgenic mouse model of lung fibrosis, we used retrospective self-gating ultrashort echo time (UTE) magnetic resonance imaging (MRI) to image mouse lung at baseline and after 4 and 8 wk of fibrosis initiation via doxycycline administration. Only bitransgenic mice were used in this study and divided into two cohorts: six mice were fed doxycycline food to induce lung fibrosis (referred to as Dox cohort), and five other mice were fed normal food (referred to as control cohort). Lung mechanics, histology, and hydroxyproline were assessed after the final MRI. A linear mixed-effects model was used to analyze MRI-derived longitudinal lung-function parameters. Tidal volume decreased at a rate of -0.016 ± 0.002 ml/week [χ2(1) = 16.48, P < 0.001] for Dox cohort and increased at a rate of 0.010 ± 0.003 ml/week [χ2(1) = 6.37, P = 0.01] for control cohort. Minute ventilation decreased at a rate of -1.71 ± 0.26 ml·min-1·wk-1 [χ2(1) = 14.04, P < 0.001] for Dox cohort but did not change significantly over time for control cohort. High-density lung volume percentage increased at a rate of 3.9 ± 0.7%/wk for Dox cohort [χ2(1) = 11.47, P < 0.001] but did not change significantly over time for control cohort. MRI-derived lung structure and function parameters were strongly correlated with pleural thickness, hydroxyproline content, lung compliance, airway resistance, and airway elastance. We conclude that self-gating UTE MRI could be used to longitudinally monitor lung fibrosis in the TGF-α transgenic mouse model. NEW & NOTEWORTHY Self-gating UTE MRI was used to monitor morphology and physiology in lung fibrosis in a transforming growth factor-α transgenic mouse model. Tidal volume was shown for the first time to correlate strongly with conventional metrics of fibrosis such as hydroxyproline and pleural thickness.
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Affiliation(s)
- Jinbang Guo
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio.,Department of Physics, Washington University in St. Louis , St. Louis, Missouri
| | - William D Hardie
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati , Cincinnati, Ohio
| | - Zackary I Cleveland
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati , Cincinnati, Ohio
| | - Cynthia Davidson
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Xuefeng Xu
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Satish K Madala
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Jason C Woods
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio.,Department of Physics, Washington University in St. Louis , St. Louis, Missouri.,Department of Physics, University of Cincinnati , Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati , Cincinnati, Ohio
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11
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Malavé MO, Baron CA, Addy NO, Cheng JY, Yang PC, Hu BS, Nishimura DG. Whole-heart coronary MR angiography using a 3D cones phyllotaxis trajectory. Magn Reson Med 2019; 81:1092-1103. [PMID: 30370941 PMCID: PMC6715422 DOI: 10.1002/mrm.27475] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 07/08/2018] [Accepted: 07/10/2018] [Indexed: 01/28/2023]
Abstract
PURPOSE To develop a 3D cones steady-state free precession sequence with improved robustness to respiratory motion while mitigating eddy current artifacts for free-breathing whole-heart coronary magnetic resonance angiography. METHOD The proposed sequence collects cone interleaves using a phyllotaxis pattern, which allows for more distributed k-space sampling for each heartbeat compared to a typical sequential collection pattern. A Fibonacci number of segments is chosen to minimize eddy current effects with the trade-off of an increased number of acquisition heartbeats. For verification, phyllotaxis-cones is compared to sequential-cones through simulations, phantom studies, and in vivo coronary scans with 8 subjects using 2D image-based navigators for retrospective motion correction. RESULTS Simulated point spread functions and moving phantom results show less coherent motion artifacts for phyllotaxis-cones compared to sequential-cones. Assessment of the right and left coronary arteries using reader scores and the image edge profile acutance vessel sharpness metric indicate superior image quality and sharpness for phyllotaxis-cones. CONCLUSION Phyllotaxis 3D cones results in improved qualitative image scores and coronary vessel sharpness for free-breathing whole-heart coronary magnetic resonance angiography compared to standard sequential ordering when using a steady-state free precession sequence.
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Affiliation(s)
- Mario O. Malavé
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California
| | - Corey A. Baron
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California
| | - Nii Okai Addy
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California
| | - Joseph Y. Cheng
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California
- Department of Radiology, Stanford University, Palo Alto, California, United States
| | - Phillip C. Yang
- Cardiovascular Medicine, Stanford University, Stanford, California, United States
| | - Bob S. Hu
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California
- Cardiology, Palo Alto Medical Foundation, Palo Alto, California, United States
| | - Dwight G. Nishimura
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California
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12
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Guo J, Cao X, Cleveland ZI, Woods JC. Murine pulmonary imaging at 7T: T2* and T 1 with anisotropic UTE. Magn Reson Med 2017; 79:2254-2264. [PMID: 28812309 DOI: 10.1002/mrm.26872] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 07/18/2017] [Accepted: 07/25/2017] [Indexed: 12/12/2022]
Abstract
PURPOSE To measure the T2* and T1 of mouse lung at 7T via anisotropic-resolution radial ultrashort echo-time imaging with ellipsoidal k-space coverage. METHODS Ellipsoidal field-of-view was created by expanding uniform spherical k-space coverage. The effects of T2* and ellipsoidal sampling on image resolution were investigated by using point-spread-function analysis and resolution phantoms. Finally, this ellipsoidal sampling approach was used to measure the lung T2* and T1 of healthy C57BL/6 mice at the increasingly common preclinical field strength of 7T. RESULTS Lung parenchyma T2* of 17- to 23-week-old mice at 7T was 0.395 ± 0.033 ms. T1 of lung and left- and right-heart ventricles was 1452.5 ± 87.0 ms, 1810.5 ± 54.6 ms, and 1602.6 ± 120.9 ms, respectively. Ellipsoidal k-space sampling provides enhanced resolution for a fixed scanning time or provides equivalent (although anisotropic) spatial resolution with reduced scanning times, while simultaneously avoiding fold-in artifacts. CONCLUSION Using these techniques, the first T2* and T1 measures of mouse lung at 7T are reported. Ultrashort echo-time imaging with ellipsoidal k-space coverage significantly increases in-plane resolution without increasing scanning time, or equivalently, decreases scanning time while maintaining equivalent in-plane resolution. Magn Reson Med 79:2254-2264, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jinbang Guo
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Xuefeng Cao
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, University of Cincinnati, Cincinnati, Ohio, USA
| | - Zackary I Cleveland
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Jason C Woods
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Physics, University of Cincinnati, Cincinnati, Ohio, USA
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13
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Jang H, McMillan AB. A rapid and robust gradient measurement technique using dynamic single-point imaging. Magn Reson Med 2016; 78:950-962. [PMID: 27699867 DOI: 10.1002/mrm.26481] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 09/01/2016] [Accepted: 09/02/2016] [Indexed: 12/20/2022]
Abstract
PURPOSE We propose a new gradient measurement technique based on dynamic single-point imaging (SPI), which allows simple, rapid, and robust measurement of k-space trajectory. METHODS To enable gradient measurement, we utilize the variable field-of-view (FOV) property of dynamic SPI, which is dependent on gradient shape. First, one-dimensional (1D) dynamic SPI data are acquired from a targeted gradient axis, and then relative FOV scaling factors between 1D images or k-spaces at varying encoding times are found. These relative scaling factors are the relative k-space position that can be used for image reconstruction. The gradient measurement technique also can be used to estimate the gradient impulse response function for reproducible gradient estimation as a linear time invariant system. RESULTS The proposed measurement technique was used to improve reconstructed image quality in 3D ultrashort echo, 2D spiral, and multi-echo bipolar gradient-echo imaging. In multi-echo bipolar gradient-echo imaging, measurement of the k-space trajectory allowed the use of a ramp-sampled trajectory for improved acquisition speed (approximately 30%) and more accurate quantitative fat and water separation in a phantom. CONCLUSION The proposed dynamic SPI-based method allows fast k-space trajectory measurement with a simple implementation and no additional hardware for improved image quality. Magn Reson Med 78:950-962, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Hyungseok Jang
- Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA.,Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, USA
| | - Alan B McMillan
- Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
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14
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Jang H, Wiens CN, McMillan AB. Ramped hybrid encoding for improved ultrashort echo time imaging. Magn Reson Med 2015; 76:814-25. [PMID: 26381890 DOI: 10.1002/mrm.25977] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 08/18/2015] [Accepted: 08/18/2015] [Indexed: 12/15/2022]
Abstract
PURPOSE We propose a new acquisition to minimize the per-excitation encoding duration and improve the imaging capability for short T2 * species. METHODS In the proposed ramped hybrid encoding (RHE) technique, gradients are applied before the radiofrequency (RF) pulse as in pointwise encoding time reduction with radial acquisition (PETRA) and zero echo time (ZTE) imaging. However, in RHE, gradients are rapidly ramped after RF excitation to the maximum amplitude to minimize encoding duration. To acquire central k-space data not measured during RF deadtime, RHE uses a hybrid encoding scheme similar to PETRA. A new gradient calibration method based on single-point imaging was developed to estimate the k-space trajectory and enable robust and high quality reconstruction. RESULTS RHE enables a shorter per-excitation encoding time and provides the highest spatial resolution among ultrashort T2 * imaging methods. In phantom and in vivo experiments, RHE exhibited robust imaging with negligible chemical shift or blurriness caused by T2 * decay and unwanted slice selection. CONCLUSION RHE allows the shortest per-excitation encoding time for ultrashort T2 * imaging, which alleviates the impact of fast T2 * decay occurring during encoding, and enables improved spatial resolution. Magn Reson Med 76:814-825, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Hyungseok Jang
- Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA.,Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, USA
| | - Curtis N Wiens
- Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
| | - Alan B McMillan
- Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
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15
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Addy NO, Ingle RR, Wu HH, Hu BS, Nishimura DG. High-resolution variable-density 3D cones coronary MRA. Magn Reson Med 2015; 74:614-21. [PMID: 26172829 DOI: 10.1002/mrm.25803] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 05/16/2015] [Accepted: 05/21/2015] [Indexed: 12/13/2022]
Abstract
PURPOSE To improve the spatial/temporal resolution of whole-heart coronary MR angiography by developing a variable-density (VD) 3D cones acquisition suitable for image reconstruction with parallel imaging and compressed sensing techniques. METHODS A VD 3D cones trajectory design incorporates both radial and spiral trajectory undersampling techniques to achieve higher resolution. This design is used to generate a VD 3D cones trajectory with 0.8 mm/66 ms isotropic spatial/temporal resolution, using a similar number of readouts as our previous fully sampled cones trajectory (1.2 mm/100 ms). Scans of volunteers and patients are performed to evaluate the performance of the VD trajectory, using non-Cartesian L1 -ESPIRiT for high-resolution image reconstruction. RESULTS With gridding reconstruction, the high-resolution scans experience an expected drop in signal-to-noise and contrast-to-noise ratios, but with L1 -ESPIRiT, the apparent noise is substantially reduced. Compared with 1.2 mm images, in each volunteer, the L1 -ESPIRiT 0.8 mm images exhibit higher vessel sharpness values in the right and left anterior descending arteries. CONCLUSION Coronary MR angiography with isotropic submillimeter spatial resolution and high temporal resolution can be performed with VD 3D cones to improve the depiction of coronary arteries.
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Affiliation(s)
- Nii Okai Addy
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
| | - R Reeve Ingle
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
| | - Holden H Wu
- Department of Radiology, University of California, Los Angeles, California, USA
| | - Bob S Hu
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
- Department of Cardiology, Palo Alto Medical Foundation, Palo Alto, California, USA
| | - Dwight G Nishimura
- Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA
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16
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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: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [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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17
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Akçakaya M, Nam S, Basha TA, Kawaji K, Tarokh V, Nezafat R. An augmented Lagrangian based compressed sensing reconstruction for non-Cartesian magnetic resonance imaging without gridding and regridding at every iteration. PLoS One 2014; 9:e107107. [PMID: 25215945 PMCID: PMC4162575 DOI: 10.1371/journal.pone.0107107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 08/14/2014] [Indexed: 12/03/2022] Open
Abstract
Background Non-Cartesian trajectories are used in a variety of fast imaging applications, due to the incoherent image domain artifacts they create when undersampled. While the gridding technique is commonly utilized for reconstruction, the incoherent artifacts may be further removed using compressed sensing (CS). CS reconstruction is typically done using conjugate-gradient (CG) type algorithms, which require gridding and regridding to be performed at every iteration. This leads to a large computational overhead that hinders its applicability. Methods We sought to develop an alternative method for CS reconstruction that only requires two gridding and one regridding operation in total, irrespective of the number of iterations. This proposed technique is evaluated on phantom images and whole-heart coronary MRI acquired using 3D radial trajectories, and compared to conventional CS reconstruction using CG algorithms in terms of quantitative vessel sharpness, vessel length, computation time, and convergence rate. Results Both CS reconstructions result in similar vessel length (P = 0.30) and vessel sharpness (P = 0.62). The per-iteration complexity of the proposed technique is approximately 3-fold lower than the conventional CS reconstruction (17.55 vs. 52.48 seconds in C++). Furthermore, for in-vivo datasets, the convergence rate of the proposed technique is faster (60±13 vs. 455±320 iterations) leading to a ∼23-fold reduction in reconstruction time. Conclusions The proposed reconstruction provides images of similar quality to the conventional CS technique in terms of removing artifacts, but at a much lower computational complexity.
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Affiliation(s)
- Mehmet Akçakaya
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Seunghoon Nam
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America; Surgical Technologies, Medtronic, Inc., Littleton, Massachusetts, United States of America
| | - Tamer A Basha
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Keigo Kawaji
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America; Department of Medicine (Section of Cardiology), University of Chicago, Chicago, Illinois, United States of America
| | - Vahid Tarokh
- School of Engineering & Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America
| | - Reza Nezafat
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
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18
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Harkins KD, Does MD, Grissom WA. Iterative method for predistortion of MRI gradient waveforms. IEEE TRANSACTIONS ON MEDICAL IMAGING 2014; 33:1641-7. [PMID: 24801945 PMCID: PMC4128553 DOI: 10.1109/tmi.2014.2320987] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The purpose of this work is to correct for transient gradient waveform errors in magnetic resonance imaging (MRI), whether from eddy currents, group delay, or gradient amplifier nonlinearities, which are known to affect image quality. An iterative method is proposed to minimize error between desired and measured gradient waveforms, whose success does not depend on accurate knowledge of the gradient system impulse response. The method was applied to half-pulse excitation for 2-D ultra-short echo time (UTE) imaging on a small animal MRI system and to spiral 2-D excitation on a human 7T MRI system. Predistorted gradient waveforms reduced temporal signal variation caused by excitation gradient trajectory errors in 2-D UTE, and improved the quality of excitation patterns produced by spiral excitation pulses. Iterative gradient predistortion is useful for minimizing transient gradient errors without requiring accurate characterization of the gradient system impulse response.
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Harkins KD, Horch RA, Does MD. Simple and robust saturation-based slice selection for ultrashort echo time MRI. Magn Reson Med 2014; 73:2204-11. [PMID: 25046136 DOI: 10.1002/mrm.25361] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/06/2014] [Accepted: 06/21/2014] [Indexed: 12/23/2022]
Abstract
PURPOSE To present a new method for localizing signal within a two-dimensional (2D) slice suitable for ultrashort echo time (UTE) imaging, called saturation-based UTE (sat-UTE). The new method digitally subtracts two acquisitions that are nonselectively excited with and without selective saturation of the slice of interest. METHODS Sat-UTE was compared with half-pulse and double-half pulse excited UTE within phantoms, as well as 3D-UTE within ex vivo femur and in vivo tibia. Numerical simulations were also used to quantify the effects of slice profile broadening and signal component amplitudes for quantitative UTE. RESULTS Sat-UTE is robust to suppress out-of-slice signal, and produces short T2 signal decay curves comparable to 3D-UTE, but has a lower signal to noise ratio efficiency compared with other slice-selective methods. CONCLUSION The proposed method is useful for fast, quantitative evaluation of short T2 signals, and is insensitive to gradient performance.
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Affiliation(s)
- Kevin D Harkins
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
| | - R Adam Horch
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Mark D Does
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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20
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O'Halloran R, Aksoy M, Aboussouan E, Peterson E, Van A, Bammer R. Real-time correction of rigid body motion-induced phase errors for diffusion-weighted steady-state free precession imaging. Magn Reson Med 2014; 73:565-76. [PMID: 24715414 DOI: 10.1002/mrm.25159] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 01/08/2014] [Accepted: 01/10/2014] [Indexed: 11/08/2022]
Abstract
PURPOSE Diffusion contrast in diffusion-weighted steady-state free precession magnetic resonance imaging (MRI) is generated through the constructive addition of signal from many coherence pathways. Motion-induced phase causes destructive interference which results in loss of signal magnitude and diffusion contrast. In this work, a three-dimensional (3D) navigator-based real-time correction of the rigid body motion-induced phase errors is developed for diffusion-weighted steady-state free precession MRI. METHODS The efficacy of the real-time prospective correction method in preserving phase coherence of the steady state is tested in 3D phantom experiments and 3D scans of healthy human subjects. RESULTS In nearly all experiments, the signal magnitude in images obtained with proposed prospective correction was higher than the signal magnitude in images obtained with no correction. In the human subjects, the mean magnitude signal in the data was up to 30% higher with prospective motion correction than without. Prospective correction never resulted in a decrease in mean signal magnitude in either the data or in the images. CONCLUSIONS The proposed prospective motion correction method is shown to preserve the phase coherence of the steady state in diffusion-weighted steady-state free precession MRI, thus mitigating signal magnitude losses that would confound the desired diffusion contrast.
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Affiliation(s)
- Rafael O'Halloran
- Department of Radiology, Stanford University, Stanford, California, USA
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21
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Kopeinigg D, Bammer R. Time-resolved angiography using inflow subtraction (TRAILS). Magn Reson Med 2013; 72:669-78. [PMID: 24166577 DOI: 10.1002/mrm.24985] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 08/21/2013] [Accepted: 09/06/2013] [Indexed: 12/30/2022]
Abstract
PURPOSE A novel pseudo-continuous arterial spin labeling based angiographic method called Time-Resolved Angiography using InfLow Subtraction is introduced and used to acquire time-resolved whole-head angiographic data sets in healthy volunteers in a clinical feasible scan time of less than 5 min. METHODS Using this new method, in conjunction with a sliding window reconstruction, a temporal resolution of 7.2 ms with a low temporal footprint of 432 ms can be achieved. RESULTS Excellent vessel delineation compared to a time-of-flight MRA was demonstrated. Normal variations of the vascular system including the Circle of Willis (CoW) were identified using Time-Resolved Angiography Using Inflow Subtraction. Signal intensities were measured in various vascular segments to quantify the blood transit time. CONCLUSION In this feasibility study, we showed that Time-Resolved Angiography using InfLow Subtraction can be used to acquire hemodynamic information of the whole head in healthy volunteers with a high temporal and spatial resolution. Further studies in patients that suffer from vascular diseases to explore various flow patterns including longer transit time are needed.
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Affiliation(s)
- Daniel Kopeinigg
- Department of Radiology, Stanford University, Stanford, California, USA
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22
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Xiao D, Balcom BJ. Hybrid-SPRITE MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 235:6-14. [PMID: 23916990 DOI: 10.1016/j.jmr.2013.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 06/02/2023]
Abstract
In a FID based frequency encoding MRI experiment the central part of k-space is not generally accessible due to the probe dead time. This portion of k-space is however crucial for image reconstruction. SPRITE (Single Point Ramped Imaging with T1 Enhancement), SPI with a linearly ramped phase encode gradient, has been employed to image short relaxation time systems for many years with great success. It is a robust imaging method in significant measure because it provides acquisition of high quality k-space origin data. We propose a new sampling scheme, termed hybrid-SPRITE, combining phase and frequency encoding to ensure high quality images with reduced acquisition times, reduced gradient duty cycle and increased sensitivity. In hybrid-SPRITE, numerous time domain points are collected to assist image reconstruction. An Inverse Non-uniform Discrete Fourier Transform (INDFT) is employed in 1D applications. A pseudo-polar grid is exploited in 2D hybrid-SPRITE for rapid and accurate image reconstruction.
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Affiliation(s)
- Dan Xiao
- MRI Research Center, Department of Physics, University of New Brunswick, 8 Bailey Drive, Fredericton, NB E3B 5A3, Canada.
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23
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Subashi E, Moding EJ, Cofer GP, MacFall JR, Kirsch DG, Qi Y, Johnson GA. A comparison of radial keyhole strategies for high spatial and temporal resolution 4D contrast-enhanced MRI in small animal tumor models. Med Phys 2013; 40:022304. [PMID: 23387766 DOI: 10.1118/1.4774050] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Dynamic contrast-enhanced (DCE) MRI has been widely used as a quantitative imaging method for monitoring tumor response to therapy. The simultaneous challenges of increasing temporal and spatial resolution in a setting where the signal from the much smaller voxel is weaker have made this MR technique difficult to implement in small-animal imaging. Existing protocols employed in preclinical DCE-MRI acquire a limited number of slices resulting in potentially lost information in the third dimension. This study describes and compares a family of four-dimensional (3D spatial + time), projection acquisition, radial keyhole-sampling strategies that support high spatial and temporal resolution. METHODS The 4D method is based on a RF-spoiled, steady-state, gradient-recalled sequence with minimal echo time. An interleaved 3D radial trajectory with a quasi-uniform distribution of points in k-space was used for sampling temporally resolved datasets. These volumes were reconstructed with three different k-space filters encompassing a range of possible radial keyhole strategies. The effect of k-space filtering on spatial and temporal resolution was studied in a 5 mM CuSO(4) phantom consisting of a meshgrid with 350-μm spacing and in 12 tumors from three cell lines (HT-29, LoVo, MX-1) and a primary mouse sarcoma model (three tumors∕group). The time-to-peak signal intensity was used to assess the effect of the reconstruction filters on temporal resolution. As a measure of heterogeneity in the third dimension, the authors analyzed the spatial distribution of the rate of transport (K(trans)) of the contrast agent across the endothelium barrier for several different types of tumors. RESULTS Four-dimensional radial keyhole imaging does not degrade the system spatial resolution. Phantom studies indicate there is a maximum 40% decrease in signal-to-noise ratio as compared to a fully sampled dataset. T1 measurements obtained with the interleaved radial technique do not differ significantly from those made with a conventional Cartesian spin-echo sequence. A bin-by-bin comparison of the distribution of the time-to-peak parameter shows that 4D radial keyhole reconstruction does not cause significant temporal blurring when a temporal resolution of 9.9 s is used for the subsamples of the keyhole data. In vivo studies reveal substantial tumor heterogeneity in the third spatial dimension that may be missed with lower resolution imaging protocols. CONCLUSIONS Volumetric keyhole imaging with projection acquisition provides a means to increase spatiotemporal resolution and coverage over that provided by existing 2D Cartesian protocols. Furthermore, there is no difference in temporal resolution between the higher spatial resolution keyhole reconstruction and the undersampled projection data. The technique allows one to measure complex heterogeneity of kinetic parameters with isotropic, microscopic spatial resolution.
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Affiliation(s)
- Ergys Subashi
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA
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Loktyushin A, Nickisch H, Pohmann R, Schölkopf B. Blind retrospective motion correction of MR images. Magn Reson Med 2013; 70:1608-18. [PMID: 23401078 DOI: 10.1002/mrm.24615] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 11/30/2012] [Accepted: 12/02/2012] [Indexed: 11/12/2022]
Abstract
PURPOSE Subject motion can severely degrade MR images. A retrospective motion correction algorithm, Gradient-based motion correction, which significantly reduces ghosting and blurring artifacts due to subject motion was proposed. The technique uses the raw data of standard imaging sequences; no sequence modifications or additional equipment such as tracking devices are required. Rigid motion is assumed. METHODS The approach iteratively searches for the motion trajectory yielding the sharpest image as measured by the entropy of spatial gradients. The vast space of motion parameters is efficiently explored by gradient-based optimization with a convergence guarantee. RESULTS The method has been evaluated on both synthetic and real data in two and three dimensions using standard imaging techniques. MR images are consistently improved over different kinds of motion trajectories. Using a graphics processing unit implementation, computation times are in the order of a few minutes for a full three-dimensional volume. CONCLUSION The presented technique can be an alternative or a complement to prospective motion correction methods and is able to improve images with strong motion artifacts from standard imaging sequences without requiring additional data.
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Nam S, Akçakaya M, Basha T, Stehning C, Manning WJ, Tarokh V, Nezafat R. Compressed sensing reconstruction for whole-heart imaging with 3D radial trajectories: a graphics processing unit implementation. Magn Reson Med 2013; 69:91-102. [PMID: 22392604 PMCID: PMC3371294 DOI: 10.1002/mrm.24234] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 01/16/2012] [Accepted: 02/06/2012] [Indexed: 11/11/2022]
Abstract
A disadvantage of three-dimensional (3D) isotropic acquisition in whole-heart coronary MRI is the prolonged data acquisition time. Isotropic 3D radial trajectories allow undersampling of k-space data in all three spatial dimensions, enabling accelerated acquisition of the volumetric data. Compressed sensing (CS) reconstruction can provide further acceleration in the acquisition by removing the incoherent artifacts due to undersampling and improving the image quality. However, the heavy computational overhead of the CS reconstruction has been a limiting factor for its application. In this article, a parallelized implementation of an iterative CS reconstruction method for 3D radial acquisitions using a commercial graphics processing unit is presented. The execution time of the graphics processing unit-implemented CS reconstruction was compared with that of the C++ implementation, and the efficacy of the undersampled 3D radial acquisition with CS reconstruction was investigated in both phantom and whole-heart coronary data sets. Subsequently, the efficacy of CS in suppressing streaking artifacts in 3D whole-heart coronary MRI with 3D radial imaging and its convergence properties were studied. The CS reconstruction provides improved image quality (in terms of vessel sharpness and suppression of noise-like artifacts) compared with the conventional 3D gridding algorithm, and the graphics processing unit implementation greatly reduces the execution time of CS reconstruction yielding 34-54 times speed-up compared with C++ implementation.
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Affiliation(s)
- Seunghoon Nam
- Department of Medicine (Cardiovascular Division), Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA
| | - Mehmet Akçakaya
- Department of Medicine (Cardiovascular Division), Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
| | - Tamer Basha
- Department of Medicine (Cardiovascular Division), Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
| | | | - Warren J. Manning
- Department of Medicine (Cardiovascular Division), Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
- Department of Radiology, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
| | - Vahid Tarokh
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA
| | - Reza Nezafat
- Department of Medicine (Cardiovascular Division), Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA
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26
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Feng Y, Song Y, Wang C, Xin X, Feng Q, Chen W. Fast direct fourier reconstruction of radial and PROPELLER MRI data using the chirp transform algorithm on graphics hardware. Magn Reson Med 2012; 70:1087-94. [PMID: 23165973 DOI: 10.1002/mrm.24556] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 10/16/2012] [Accepted: 10/17/2012] [Indexed: 11/06/2022]
Abstract
PURPOSE To develop and test a new algorithm for fast direct Fourier transform (DrFT) reconstruction of MR data on non-Cartesian trajectories composed of lines with equally spaced points. THEORY AND METHODS The DrFT, which is normally used as a reference in evaluating the accuracy of other reconstruction methods, can reconstruct images directly from non-Cartesian MR data without interpolation. However, DrFT reconstruction involves substantially intensive computation, which makes the DrFT impractical for clinical routine applications. In this article, the Chirp transform algorithm was introduced to accelerate the DrFT reconstruction of radial and Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) MRI data located on the trajectories that are composed of lines with equally spaced points. The performance of the proposed Chirp transform algorithm-DrFT algorithm was evaluated by using simulation and in vivo MRI data. RESULTS After implementing the algorithm on a graphics processing unit, the proposed Chirp transform algorithm-DrFT algorithm achieved an acceleration of approximately one order of magnitude, and the speed-up factor was further increased to approximately three orders of magnitude compared with the traditional single-thread DrFT reconstruction. CONCLUSION Implementation the Chirp transform algorithm-DrFT algorithm on the graphics processing unit can efficiently calculate the DrFT reconstruction of the radial and PROPELLER MRI data.
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Affiliation(s)
- Yanqiu Feng
- School of Biomedical Engineering, Southern Medical University, Guangzhou, China
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27
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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] [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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28
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O'Halloran RL, Aksoy M, Van AT, Bammer R. 3D isotropic high-resolution diffusion-weighted MRI of the whole brain with a motion-corrected steady-state free precession sequence. Magn Reson Med 2012; 70:466-78. [DOI: 10.1002/mrm.24489] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 08/15/2012] [Accepted: 08/16/2012] [Indexed: 11/10/2022]
Affiliation(s)
- R. L. O'Halloran
- Department of Radiology; Stanford University; Stanford; California; USA
| | - M. Aksoy
- Department of Radiology; Stanford University; Stanford; California; USA
| | - A. T. Van
- Department of Radiology; Stanford University; Stanford; California; USA
| | - R. Bammer
- Department of Radiology; Stanford University; Stanford; California; USA
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Addy NO, Wu HH, Nishimura DG. Simple method for MR gradient system characterization and k-space trajectory estimation. Magn Reson Med 2011; 68:120-9. [PMID: 22189904 DOI: 10.1002/mrm.23217] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 08/19/2011] [Accepted: 08/22/2011] [Indexed: 11/10/2022]
Abstract
Fast imaging trajectories are used in MRI to speed up the acquisition process, but imperfections in the gradient system create artifacts in the reconstructed images. Artifacts result from the deviation between k-space trajectories achieved on the scanner and their original prescription. Measuring or approximating actual k-space trajectories with predetermined gradient timing delays reduces the artifacts, but are generally based on a specific trajectory and scan orientation. A single linear time-invariant characterization of the gradient system provides a method to predict k-space trajectories scanned in arbitrary orientations through convolution. This is done efficiently, by comparing the Fourier transforms of the input and measured waveforms of a single high-bandwidth test gradient waveform. This new method is tested for spiral, interleaved echo-planar, and three-dimensional cones imaging, demonstrating its ability to reduce reconstructed image artifacts for various k-space trajectories.
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Affiliation(s)
- Nii Okai Addy
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.
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30
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Lin W, Huang F, Simonotto E, Duensing GR, Reykowski A. Off-resonance artifacts correction with convolution in k-space (ORACLE). Magn Reson Med 2011; 67:1547-55. [DOI: 10.1002/mrm.23135] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 06/24/2011] [Accepted: 07/12/2011] [Indexed: 11/11/2022]
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31
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Ioakimidis I, Zandian M, Eriksson-Marklund L, Bergh C, Grigoriadis A, Södersten P. Description of chewing and food intake over the course of a meal. Physiol Behav 2011; 104:761-9. [PMID: 21807012 DOI: 10.1016/j.physbeh.2011.07.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/13/2011] [Accepted: 07/14/2011] [Indexed: 11/18/2022]
Abstract
While the average frequency of chewing and food intake have been reported before, a detailed description of the pattern of chewing and the cumulative intake of food over the course of a meal have not. In order to achieve this goal, video recording of the maxillary-mandibular region of women eating food from a plate was synchronized with video recording of the plate and computer recording of the weight-loss of the plate. Video recording of chewing correlated strongly with chewing identified by magnetic tracking of jaw displacement in a test with chewing gum at three different frequencies, thus ensuring the validity of video recording of chewing. Weight-loss data were corrected by convolution algorithms, validated against human correction, using sliding window filtering to correct errors with video events as reference points. By use of this method, women ate on average 264 g of food over 114 min, they took an average of 51 mouthfuls during the meal and displayed on average 794 chews with 15 chews per chewing sequence. The number of mouthfuls decreased and the duration of the pauses after each mouthful increased in the middle of the meal and these measures were then restored. The ratio between chewing sequences and subsequent pauses remained stable although the weight of each mouthful decreased by the end of the meal, a measure that is hypothesized to be reflected in a decelerated speed of eating. The method allows this hypothesis to be tested and its implication for clinical intervention to be examined.
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Affiliation(s)
- Ioannis Ioakimidis
- Karolinska Institutet, NVS, Section of Applied Neuroendocrinology and Mandometer and Mandolean Clinics Sweden, Department of Dental Medicine, Mando Group AB, Novum, S-141 04, Huddinge, Sweden.
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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] [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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33
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Chan RW, Ramsay EA, Cheung EY, Plewes DB. The influence of radial undersampling schemes on compressed sensing reconstruction in breast MRI. Magn Reson Med 2011; 67:363-77. [DOI: 10.1002/mrm.23008] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/31/2011] [Accepted: 04/28/2011] [Indexed: 12/24/2022]
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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] [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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35
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Lin W, Börnert P, Huang F, Duensing GR, Reykowski A. Generalized GRAPPA operators for wider spiral bands: Rapid self-calibrated parallel reconstruction for variable density spiral MRI. Magn Reson Med 2011; 66:1067-78. [DOI: 10.1002/mrm.22900] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 12/13/2010] [Accepted: 02/08/2011] [Indexed: 11/06/2022]
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Johnson KO, Robison RK, Pipe JG. Rigid body motion compensation for spiral projection imaging. IEEE TRANSACTIONS ON MEDICAL IMAGING 2011; 30:655-665. [PMID: 21062678 DOI: 10.1109/tmi.2010.2091146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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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Maclaren J, Lee KJ, Luengviriya C, Speck O, Zaitsev M. Combined prospective and retrospective motion correction to relax navigator requirements. Magn Reson Med 2011; 65:1724-32. [PMID: 21590805 DOI: 10.1002/mrm.22754] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/22/2010] [Accepted: 11/18/2010] [Indexed: 11/11/2022]
Abstract
Prospective motion correction can prevent motion artifacts in magnetic resonance imaging of the brain. However, for high-resolution imaging, the technique relies on precise tracking of head motion. This precision is often limited by tracking noise, which leads to residual errors in the prospectively-corrected k-space data and artifacts in the image. This work shows that it is possible to estimate these tracking errors, and hence the true k-space sample locations, by applying a two-sided filter to the tracking data after imaging. A conjugate gradient reconstruction is compared to gridding as a means of using this information to retrospectively correct for the effects of the residual errors.
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Affiliation(s)
- Julian Maclaren
- Department of Radiology, Medical Physics, University Medical Center, Freiburg, Freiburg, Germany.
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Non-Iterative Regularized reconstruction Algorithm for Non-CartesiAn MRI: NIRVANA. Magn Reson Imaging 2011; 29:222-9. [DOI: 10.1016/j.mri.2010.08.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 08/04/2010] [Accepted: 08/31/2010] [Indexed: 11/21/2022]
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39
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Robison RK, Devaraj A, Pipe JG. Fast, simple gradient delay estimation for spiral MRI. Magn Reson Med 2010; 63:1683-90. [PMID: 20512872 DOI: 10.1002/mrm.22327] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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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