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Cui L, McWalter EJ, Moran G, Venugopal N. Design and development of a novel flexible ultra-short echo time (FUSE) sequence. Magn Reson Med 2023; 90:1905-1918. [PMID: 37392415 DOI: 10.1002/mrm.29784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 05/28/2023] [Accepted: 06/13/2023] [Indexed: 07/03/2023]
Abstract
PURPOSE To present the validation of a new Flexible Ultra-Short Echo time (FUSE) pulse sequence using a short-T2 phantom. METHODS FUSE was developed to include a range of RF excitation pulses, trajectories, dimensionalities, and long-T2 suppression techniques, enabling real-time interchangeability of acquisition parameters. Additionally, we developed an improved 3D deblurring algorithm to correct for off-resonance artifacts. Several experiments were conducted to validate the efficacy of FUSE, by comparing different approaches for off-resonance artifact correction, variations in RF pulse and trajectory combinations, and long-T2 suppression techniques. All scans were performed on a 3 T system using an in-house short-T2 phantom. The evaluation of results included qualitative comparisons and quantitative assessments of the SNR and contrast-to-noise ratio. RESULTS Using the capabilities of FUSE, we demonstrated that we could combine a shorter readout duration with our improved deblurring algorithm to effectively reduce off-resonance artifacts. Among the different RF and trajectory combinations, the spiral trajectory with the regular half-inc pulse achieves the highest SNRs. The dual-echo subtraction technique delivers better short-T2 contrast and superior suppression of water and agar signals, whereas the off-resonance saturation method successfully suppresses water and lipid signals simultaneously. CONCLUSION In this work, we have validated the use of our new FUSE sequence using a short T2 phantom, demonstrating that multiple UTE acquisitions can be achieved within a single sequence. This new sequence may be useful for acquiring improved UTE images and the development of UTE imaging protocols.
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Affiliation(s)
- Lumeng Cui
- Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Emily J McWalter
- Department of Mechanical Engineering and Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Gerald Moran
- Siemens Healthcare Limited, Oakville, Ontario, Canada
| | - Niranjan Venugopal
- Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
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Afsahi AM, Sedaghat S, Moazamian D, Afsahi G, Athertya JS, Jang H, Ma YJ. Articular Cartilage Assessment Using Ultrashort Echo Time MRI: A Review. Front Endocrinol (Lausanne) 2022; 13:892961. [PMID: 35692400 PMCID: PMC9178905 DOI: 10.3389/fendo.2022.892961] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/14/2022] [Indexed: 01/05/2023] Open
Abstract
Articular cartilage is a major component of the human knee joint which may be affected by a variety of degenerative mechanisms associated with joint pathologies and/or the aging process. Ultrashort echo time (UTE) sequences with a TE less than 100 µs are capable of detecting signals from both fast- and slow-relaxing water protons in cartilage. This allows comprehensive evaluation of all the cartilage layers, especially for the short T2 layers which include the deep and calcified zones. Several ultrashort echo time (UTE) techniques have recently been developed for both morphological imaging and quantitative cartilage assessment. This review article summarizes the current catalog techniques based on UTE Magnetic Resonance Imaging (MRI) that have been utilized for such purposes in the human knee joint, such as T1, T2∗ , T1ρ, magnetization transfer (MT), double echo steady state (DESS), quantitative susceptibility mapping (QSM) and inversion recovery (IR). The contrast mechanisms as well as the advantages and disadvantages of these techniques are discussed.
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Affiliation(s)
- Amir Masoud Afsahi
- Department of Radiology, University of California San Diego, San Diego, CA, United States
- Research Service, Veterans Affairs San Diego Healthcare System, San Diego, CA, United States
| | - Sam Sedaghat
- Department of Radiology, University of California San Diego, San Diego, CA, United States
| | - Dina Moazamian
- Department of Radiology, University of California San Diego, San Diego, CA, United States
- Research Service, Veterans Affairs San Diego Healthcare System, San Diego, CA, United States
| | - Ghazaleh Afsahi
- Department of Biotechnology Research, BioSapien, San Diego, CA, United States
| | - Jiyo S. Athertya
- Department of Radiology, University of California San Diego, San Diego, CA, United States
| | - Hyungseok Jang
- Department of Radiology, University of California San Diego, San Diego, CA, United States
| | - Ya-Jun Ma
- Department of Radiology, University of California San Diego, San Diego, CA, United States
- *Correspondence: Ya-Jun Ma,
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Zhang M, Li Z, Wang H, Chen T, Lu Y, Yan F, Zhang Y, Wei H. Simultaneous Quantitative Susceptibility Mapping of Articular Cartilage and Cortical Bone of Human Knee Joint Using Ultrashort Echo Time Sequences. Front Endocrinol (Lausanne) 2022; 13:844351. [PMID: 35273576 PMCID: PMC8901574 DOI: 10.3389/fendo.2022.844351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 01/31/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND It is of great clinical importance to assess the microstructure of the articular cartilage and cortical bone of the human knee joint. While quantitative susceptibility mapping (QSM) is a promising tool for investigating the knee joint, however, previous QSM studies using conventional gradient recalled echo sequences or ultrashort echo time (UTE) sequences only focused on mapping the magnetic susceptibility of the articular cartilage or cortical bone, respectively. Simultaneously mapping the underlying susceptibilities of the articular cartilage and cortical bone of human in vivo has not been explored and reported. METHOD Three-dimensional multi-echo radial UTE sequences with the shortest TE of 0.07 msec and computed tomography (CT) were performed on the bilateral knee joints of five healthy volunteers for this prospective study. UTE-QSM was reconstructed from the local field map after water-fat separation and background field removal. Spearman's correlation analysis was used to explore the relationship between the magnetic susceptibility and CT values in 158 representative regions of interest of cortical bone. RESULT The susceptibility properties of the articular cartilage and cortical bone were successfully quantified by UTE-QSM. The laminar structure of articular cartilage was characterized by the difference of susceptibility value in each layer. Susceptibility was mostly diamagnetic in cortical bone. A significant negative correlation (r=-0.43, p<0.001) between the susceptibility value and CT value in cortical bone was observed. CONCLUSION UTE-QSM enables simultaneous susceptibility mapping of the articular cartilage and cortical bone of human in vivo. Good association between susceptibility and CT values in cortical bone suggests the potential of UTE-QSM for bone mapping for further clinical application.
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Affiliation(s)
- Ming Zhang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zhihui Li
- Department of Radiology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Hanqi Wang
- Department of Radiology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Tongtong Chen
- Department of Radiology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yong Lu
- Department of Radiology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Fuhua Yan
- Department of Radiology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yuyao Zhang
- School of Information and Science and Technology, ShanghaiTech University, Shanghai, China
| | - Hongjiang Wei
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
- *Correspondence: Hongjiang Wei,
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Fischer A, Martirosian P, Benkert T, Schick F. Spatially resolved free-induction decay spectroscopy using a 3D ultra-short echo time multi-echo imaging sequence with systematic echo shifting and compensation of B 0 field drifts. Magn Reson Med 2021; 87:2099-2110. [PMID: 34866240 DOI: 10.1002/mrm.29115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 11/15/2021] [Accepted: 11/18/2021] [Indexed: 11/08/2022]
Abstract
PURPOSE Biologically interesting signals can exhibit fast transverse relaxation and frequency shifts compared to free water. For spectral assignment, a ultra-short echo time (UTE) imaging sequence was modified to provide pixel-wise free-induction decay (FID) acquisition. METHODS The UTE-FID approach presented relies on a multi-echo 3D spiral UTE sequence with six echoes per radiofrequency (RF) excitation (TEmin 0.05 ms, echo spacing 3 ms). A complex pixel-wise raw data set for FID spectroscopy is obtained by several multi-echo UTE measurements with systematic shifting of the readout by 0.25 or 0.5 ms, until the time domain is filled for 18 or 45 ms. B0 drifts are compensated by mapping and according phase correction. Autoregressive extrapolation of the signal is performed before Gaussian filtering. This method was applied to a phantom containing collagen-water solutions of different concentrations. To calculate the collagen content, a 19-peak collagen model was extracted from a non-selective FID spectrum (50% collagen solution). Proton-density-collagen-fraction (PDCF) was calculated for 10 collagen solutions (2%-50%). Furthermore, an in vivo UTE-FID spectrum of adipose tissue was recorded. RESULTS UTE-FID signal patterns agreed well with the non-spatially selective pulse-acquire FID spectrum from a sphere filled with 50% collagen. Differentiation of collagen solution from distilled water in the PDCF map was possible from 4% collagen concentration for a UTE-FID sequence with 128 × 128 × 64 matrix (voxel size 1 × 1 × 2.85 mm3 ). The mean values of the PDCF correlate linearly with collagen concentration. CONCLUSION The presented UTE-FID approach allows pixel-wise raw data acquisition similar to non-spatially selective pulse-acquire spectroscopy. Spatially resolved applications for assessment of spectra of rapidly decaying signals seem feasible.
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Affiliation(s)
- Anja Fischer
- Section on Experimental Radiology, University Hospital Tübingen, Tübingen, Germany
| | - Petros Martirosian
- Section on Experimental Radiology, University Hospital Tübingen, Tübingen, Germany
| | - Thomas Benkert
- MR Applications Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany
| | - Fritz Schick
- Section on Experimental Radiology, University Hospital Tübingen, Tübingen, Germany
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Gaeta M, Cavallaro M, Vinci SL, Mormina E, Blandino A, Marino MA, Granata F, Tessitore A, Galletta K, D'Angelo T, Visalli C. Magnetism of materials: theory and practice in magnetic resonance imaging. Insights Imaging 2021; 12:179. [PMID: 34862955 PMCID: PMC8643382 DOI: 10.1186/s13244-021-01125-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 11/08/2021] [Indexed: 02/03/2023] Open
Abstract
All substances exert magnetic properties in some extent when placed in an external magnetic field. Magnetic susceptibility represents a measure of the magnitude of magnetization of a certain substance when the external magnetic field is applied. Depending on the tendency to be repelled or attracted by the magnetic field and in the latter case on the magnitude of this effect, materials can be classified as diamagnetic or paramagnetic, superparamagnetic and ferromagnetic, respectively. Knowledge of type and extent of susceptibility of common endogenous and exogenous substances and how their magnetic properties affect the conventional sequences used in magnetic resonance imaging (MRI) can help recognize them and exalt or minimize their presence in the acquired images, so as to improve diagnosis in a wide variety of benign and malignant diseases. Furthermore, in the context of diamagnetic susceptibility, chemical shift imaging enables to assess the intra-voxel ratio between water and fat content, analyzing the tissue composition of various organs and allowing a precise fat quantification. The following article reviews the fundamental physical principles of magnetic susceptibility and examines the magnetic properties of the principal endogenous and exogenous substances of interest in MRI, providing potential through representative cases for improved diagnosis in daily clinical routine.
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Affiliation(s)
- Michele Gaeta
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Marco Cavallaro
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Sergio Lucio Vinci
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Enricomaria Mormina
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy.
| | - Alfredo Blandino
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Maria Adele Marino
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Francesca Granata
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Agostino Tessitore
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Karol Galletta
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Tommaso D'Angelo
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
| | - Carmela Visalli
- Department of Biomedical Sciences and Morphological and Functional Imaging, Policlinico Universitario G. Martino, University of Messina, Via Consolare Valeria 1, 98100, Messina, Italy
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Quantitative MRI in patients with gluteal tendinopathy and asymptomatic volunteers: initial results on T1- and T2*-mapping diagnostic accuracy and correlation with clinical assessment. Skeletal Radiol 2021; 50:2221-2231. [PMID: 33914122 DOI: 10.1007/s00256-021-03781-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 04/04/2021] [Accepted: 04/04/2021] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To determine if T1- and T2*-mapping of the gluteal tendons can discriminate between participants with and without clinical findings of gluteal tendinopathy (GT) and if they correlate with clinical assessment. MATERIALS AND METHODS This prospective study was conducted between January and December 2016. MRI of the hip included spin echo, short-T1 inversion recovery, variable-flip angle, and variable echo-time gradient echo sequences. MRI studies were reviewed independently by two radiologists. Two other readers segmented the gluteal tendons and T1, mono- (T2*m) and bi-exponential T2* (short (T2*s) and long (T2*l) components) were computed. RESULTS Ten participants with GT (median age; interquartile range: 63 (57-67) years, all women) and 9 participants without GT (57 (55-59) years, 8 women) (P = 0.06) were enrolled. The sensitivity and specificity of reader 1 for disease classification were 40% (95% confidence interval (CI): 17-61%) and 70% (CI: 47-91%), and those of reader 2 were 70% (CI: 43-86%) and 80% (CI: 53-96%), with fair inter-reader agreement (Kappa = .38). T1 values could not discriminate between the two groups. The gluteal tendons T2*m and T2*s showed diagnostic accuracy ranging from .80 to .89. The posterior gluteus medius tendon T2*m and T2*s respectively showed sensitivity and specificity of 90%, and strong correlation (Spearman's rho = -.71; P = 0.02) with the Lower Extremity Functional Scale score. CONCLUSION Quantitative MRI could help gain new insight into healthy and diseased gluteal tendons to allow better diagnosis and treatment stratification for patients.
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Chong LR, Lee K, Sim FY. 3D MRI with CT-like bone contrast - An overview of current approaches and practical clinical implementation. Eur J Radiol 2021; 143:109915. [PMID: 34461599 DOI: 10.1016/j.ejrad.2021.109915] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/13/2021] [Accepted: 08/15/2021] [Indexed: 12/24/2022]
Abstract
CT is the imaging modality of choice for assessment of 3D bony morphology but incurs the penalty of ionizing radiation. Improving the ability of 3D MRI to provide high-resolution images of cortical bone with CT-like bone contrast has been a focus of recent research. The ability of 3D MRI to deliver cortical bone information with similar diagnostic performance to CT would complement assessment of soft tissues and medullary bone from a single MRI examination, simplifying evaluation and obviating radiation exposure from additional CT. This article presents an overview of current 3D MRI approaches for imaging cortical bone with CT-like bone contrast including ultrashort echo time, zero echo time, T1-weighted gradient recalled echo, susceptibility-weighted imaging and deep learning techniques. We also discuss clinical implementation of an optimized stack-of-stars 3D gradient recalled echo pulse sequence (3D-Bone) on commercially available MRI scanners for rendering 3D MRI with CT-like bone contrast in our institutional practice.
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Affiliation(s)
- Le Roy Chong
- Department of Radiology, Changi General Hospital, 2 Simei Street 3, Singapore 529889, Republic of Singapore.
| | - Kathy Lee
- Department of Radiology, Changi General Hospital, 2 Simei Street 3, Singapore 529889, Republic of Singapore.
| | - Fang Yang Sim
- Department of Radiology, Changi General Hospital, 2 Simei Street 3, Singapore 529889, Republic of Singapore.
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Trudel G, Duchesne-Bélanger S, Thomas J, Melkus G, Cron GO, Larson PEZ, Schweitzer M, Sheikh A, Louati H, Laneuville O. Quantitative analysis of repaired rabbit supraspinatus tendons (± channeling) using magnetic resonance imaging at 7 Tesla. Quant Imaging Med Surg 2021; 11:3460-3471. [PMID: 34341723 DOI: 10.21037/qims-20-1343] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 03/26/2021] [Indexed: 01/08/2023]
Abstract
Background The quantitative assessment of supraspinatus tendons by conventional magnetic resonance is limited by low contrast-to-noise ratio (CNR). Magnetic resonance imaging (MRI) scanners operating at 7 Tesla offer high signal-to noise ratio (SNR), low CNR and high spatial resolution that are well-suited for rapidly relaxing tissues like tendons. Few studies have applied T2 and T2* mapping to musculoskeletal imaging and to the rotator cuff tendons. Our objective was to analyze the T2 and T2* relaxation times from surgically repaired supraspinatus tendons and the effect of bone channeling. Methods One supraspinatus tendon of 112 adult female New Zealand white rabbits was surgically detached and repaired one week later. Rabbits were randomly assigned to channeling (n=64) or control (n=48) groups and harvested at 0, 1, 2, and 4 weeks. A 7T magnet was used for signal acquisition. For T2 mapping, a sagittal multi slice 2D multi-echo spin-echo (MESE) CPMG sequence with fat saturation was applied and T2* mapping was performed using a 3D UTE sequence. Magnetic resonance images from supraspinatus tendons were analyzed by two raters. Three regions of interest were manually drawn on the first T2-weighted dataset. For T2 and T2*, different ROI masks were generated to obtain relaxation times. Results T2-weighted maps but not T2*-weighted maps generated reliable signals for relaxation time measurement. Torn supraspinatus tendons had lower T2 than controls at the time of repair (20.0±3.4 vs. 25.6±3.9 ms; P<0.05). T2 increased at 1, 2 and 4 postoperative weeks: 22.7±3.1, 23.3±3.9 and 24.0±5.1 ms, respectively, and values were significantly different from contralateral supraspinatus tendons (24.8±3.1; 26.8±4.3 and 26.5±3.6 ms; all P<0.05). Bone channeling did not affect T2 (P>0.05). Conclusions Supraspinatus tendons detached for 1 week had shorter T2 relaxation time compared to contralateral as measured with 7T MRI.
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Affiliation(s)
- Guy Trudel
- Bone and Joint Research Laboratory, Ottawa Hospital Research Institute, Ottawa, ON, Canada.,Department of Medicine, Division of Physiatry, University of Ottawa, Ottawa, ON, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
| | - Samuel Duchesne-Bélanger
- Bone and Joint Research Laboratory, Ottawa Hospital Research Institute, Ottawa, ON, Canada.,Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Justin Thomas
- Bone and Joint Research Laboratory, Ottawa Hospital Research Institute, Ottawa, ON, Canada.,Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Gerd Melkus
- Department of Medical Imaging, The Ottawa Hospital, Ottawa, ON, Canada.,Department of Radiology, University of Ottawa, Ottawa, ON, Canada
| | - Greg O Cron
- Department of Medical Imaging, The Ottawa Hospital, Ottawa, ON, Canada.,Department of Radiology, University of Ottawa, Ottawa, ON, Canada
| | - Peder E Z Larson
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, CA, USA
| | - Mark Schweitzer
- Department of Radiology, Stony Brook University NY, New York, NY, USA
| | - Adnan Sheikh
- Department of Medical Imaging, The Ottawa Hospital, Ottawa, ON, Canada.,Department of Radiology, University of Ottawa, Ottawa, ON, Canada
| | - Hakim Louati
- Bone and Joint Research Laboratory, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Odette Laneuville
- Bone and Joint Research Laboratory, Ottawa Hospital Research Institute, Ottawa, ON, Canada.,Department of Biology, University of Ottawa, Ottawa, ON, Canada
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Ljungberg E, Damestani NL, Wood TC, Lythgoe DJ, Zelaya F, Williams SCR, Solana AB, Barker GJ, Wiesinger F. Silent zero TE MR neuroimaging: Current state-of-the-art and future directions. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2021; 123:73-93. [PMID: 34078538 PMCID: PMC7616227 DOI: 10.1016/j.pnmrs.2021.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 06/12/2023]
Abstract
Magnetic Resonance Imaging (MRI) scanners produce loud acoustic noise originating from vibrational Lorentz forces induced by rapidly changing currents in the magnetic field gradient coils. Using zero echo time (ZTE) MRI pulse sequences, gradient switching can be reduced to a minimum, which enables near silent operation.Besides silent MRI, ZTE offers further interesting characteristics, including a nominal echo time of TE = 0 (thus capturing short-lived signals from MR tissues which are otherwise MR-invisible), 3D radial sampling (providing motion robustness), and ultra-short repetition times (providing fast and efficient scanning).In this work we describe the main concepts behind ZTE imaging with a focus on conceptual understanding of the imaging sequences, relevant acquisition parameters, commonly observed image artefacts, and image contrasts. We will further describe a range of methods for anatomical and functional neuroimaging, together with recommendations for successful implementation.
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Affiliation(s)
- Emil Ljungberg
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom.
| | - Nikou L Damestani
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Tobias C Wood
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - David J Lythgoe
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Fernando Zelaya
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Steven C R Williams
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | | | - Gareth J Barker
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Florian Wiesinger
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom; ASL Europe, GE Healthcare, Munich, Germany
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10
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Kim DJ, Hwang K, Kim H, Cha JG, Jang H, Park JY, Kim YJ. Depiction of the Periosteum Using Ultrashort Echo Time Pulse Sequence with Three-Dimensional Cone Trajectory and Histologic Correlation in a Porcine Model. Korean J Radiol 2021; 22:782-791. [PMID: 33660460 PMCID: PMC8076835 DOI: 10.3348/kjr.2020.0640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 08/16/2020] [Accepted: 10/14/2020] [Indexed: 12/31/2022] Open
Abstract
Objective To evaluate the signal intensity of the periosteum using ultrashort echo time pulse sequence with three-dimensional cone trajectory (3D UTE) with or without fat suppression (FS) to distinguish from artifacts in porcine tibias. Materials and Methods The periosteum and overlying soft tissue of three porcine lower legs were partially peeled away from the tibial cortex. Another porcine tibia was prepared as three segments: with an intact periosteum outer and inner layer, with an intact periosteum inner layer, and without periosteum. Axial T1 weighted sequence (T1 WI) and 3D UTE (FS) were performed. Another porcine tibia without periosteum was prepared and subjected to 3D UTE (FS) and T1 WI twice, with positional changes. Two radiologists analyzed images to reach a consensus. Results The three periosteal tissues that were partially peeled away from the cortex showed a high signal in 3D UTE (FS) and low signal on T1 WI. 3D UTE (FS) showed a high signal around the cortical surface with an intact outer and inner periosteum, and subtle high signals, mainly around the upper cortical surfaces with the inner layer of the periosteum and without periosteum. T1 WI showed no signal around the cortical surfaces, regardless of the periosteum state. The porcine tibia without periosteum showed changes in the high signal area around the cortical surface as the position changed in 3D UTE (FS). No signal was detected around the cortical surface in T1 WI, regardless of the position change. Conclusion The periosteum showed a high signal in 3D UTE and 3D UTE FS that overlapped with artifacts around the cortical bone.
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Affiliation(s)
- Dae Joong Kim
- Department of Anatomy, College of Medicine, Inha University, Incheon, Korea
| | - Kun Hwang
- Department of Plastic Surgery, College of Medicine, Inha University, Incheon, Korea
| | - Hun Kim
- Department of Plastic Surgery, College of Medicine, Inha University, Incheon, Korea
| | - Jang Gyu Cha
- Department of Radiology, Soonchunhyang University Hospital, Bucheon, Korea
| | - Hyungseok Jang
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
| | - Ju Yong Park
- Department of Radiology, College of Medicine, Inha University, Incheon, Korea
| | - Yeo Ju Kim
- Department of Radiology, College of Medicine, Inha University, Incheon, Korea.
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11
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Ozen AC, Idiyatullin D, Adriany G, Jungst S, Kobayashi N, Groenke BR, Bock M, Garwood M, Nixdorf DR. Design of an Intraoral Dipole Antenna for Dental Applications. IEEE Trans Biomed Eng 2021; 68:2563-2573. [PMID: 33513097 DOI: 10.1109/tbme.2021.3055777] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE In dental MRI, intraoral coils provide higher signal-to-noise ratio (SNR) than coils placed outside the mouth. This study aims to design an intraoral dipole antenna and demonstrates the feasibility of combining it with an extraoral coil. METHODS Dipole antenna design was chosen over loop design, as it is open toward the distal; therefore, it does not restrain tongue movement. The dipole design offers also an increased depth-of-sensitivity that allows for MRI of dental roots. Different dipole antenna designs were simulated using a finite-difference-time-domain approach. Ribbon, wire, and multi-wire arms were compared. The best design was improved further by covering the ends of the dipole arms with a high-permittivity material. Phantom and in vivo measurements were conducted on a 3T clinical MRI system. RESULTS The best transmit efficiency and homogeneity was achieved with a multi-wire curved dipole antenna with 7 wires for each arm. With an additional high-permittivity cap the transmit field inhomogeneity was further reduced from 20% to 5% along the dipole arm. When combined with extraoral flexible surface-coil, the coupling between the coils was less than -32dB and SNR was increased. CONCLUSION Using intraoral dipole design instead of loop improves patient comfort. We demonstrated feasibility of the intraoral dipole combined with an extraoral flexible coil-array for dental MRI. Dipole antenna enabled decreasing imaging field-of-view, and reduced the prevalent signal from tongue. SIGNIFICANCE This study highlights the advantages and the main challenges of the intraoral RF coils and describes a novel RF coil that addresses those challenges.
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Comparison of phase-resolved functional lung (PREFUL) MRI derived perfusion and ventilation parameters at 1.5T and 3T in healthy volunteers. PLoS One 2020; 15:e0244638. [PMID: 33378373 PMCID: PMC7773267 DOI: 10.1371/journal.pone.0244638] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/15/2020] [Indexed: 11/20/2022] Open
Abstract
Purpose The purpose of this study is to evaluate the influence of different field strengths on perfusion and ventilation parameters, SNR and CNR derived by PREFUL MRI using predefined sequence parameters. Methods Data sets of free breathing 2d FLASH lung MRI were acquired from 15 healthy subjects at 1.5T and 3T (Magnetom Avanto and Skyra, Siemens Healthcare, Erlangen, Germany) with a maximum period of 3 days in between. The processed functional parameters regional ventilation (RVent), perfusion (Q), quantified perfusion (QQuant), perfusion defect percentage (QDP), ventilation defect percentage (VDP) and ventilation-perfusion match (VQM) were compared for systematic differences. Signal- and contrast-to-noise ratio (SNR and CNR) of both acquisitions were analyzed. Results RVent, Q, VDP, SNR and CNR presented no significant differences between 1.5T and 3T. QQuant (1.5T vs. 3T, P = 0.04), and QDP (1.5T vs. 3T, P≤0.01) decreased significantly at 3T. Consequently, VQM increased significantly (1.5T vs. 3T, P≤0.01). Skewness and kurtosis of the Q-values increased significantly at 3T (P≤0.01). The mean Sørensen-Dice coefficients between both series were 0.91 for QDP and 0.94 for VDP. The Bland-Altman analysis of both series showed mean differences of 4.29% for QDP, 1.23% for VDP and -5.15% for VQM. Using the above-mentioned parameters for three-day repeatability at two different scanners and field strengths, the retrospective power calculation showed, that a sample size of 15 can detect differences of 3.7% for QDP, of 2.9% for VDP and differences of 2.6% for VQM. Conclusion Significant differences in QDP may be related to field inhomogeneities, which is expressed by increasing skewness and kurtosis at 3T. QQuant reveals only poor reproducibility between 1.5T and 3T. RVent, Q, VDP, SNR and CNR were not altered significantly at the used sequence parameters. Healthy participants with minimal defects present high spatial agreement of QDP and VDP.
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Mastrogiacomo S, Dou W, Jansen JA, Walboomers XF. Magnetic Resonance Imaging of Hard Tissues and Hard Tissue Engineered Bio-substitutes. Mol Imaging Biol 2020; 21:1003-1019. [PMID: 30989438 DOI: 10.1007/s11307-019-01345-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Magnetic resonance imaging (MRI) is a non-invasive diagnostic imaging tool based on the detection of protons into the tissues. This imaging technique is remarkable because of high spatial resolution, strong soft tissue contrast and specificity, and good depth penetration. However, MR imaging of hard tissues, such as bone and teeth, remains challenging due to low proton content in such tissues as well as to very short transverse relaxation times (T2). To overcome these issues, new MRI techniques, such as sweep imaging with Fourier transformation (SWIFT), ultrashort echo time (UTE) imaging, and zero echo time (ZTE) imaging, have been developed for hard tissues imaging with promising results reported. Within this article, MRI techniques developed for the detection of hard tissues, such as bone and dental tissues, have been reviewed. The main goal was thus to give a comprehensive overview on the corresponding (pre-) clinical applications and on the potential future directions with such techniques applied. In addition, a section dedicated to MR imaging of novel biomaterials developed for hard tissue applications was given as well.
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Affiliation(s)
- Simone Mastrogiacomo
- Department of Biomaterials, Radboud University Medical Center, Philips van Leijdenlaan 25, 6525 EX, Nijmegen, The Netherlands.
- Laboratory of Functional and Molecular Imaging, NINDS, National Institutes of Health, Building 10, 5S261, Bethesda, MD, 20892, USA.
| | - Weiqiang Dou
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA, Nijmegen, The Netherlands
- GE Healthcare, MR Research, Beijing, People's Republic of China
| | - John A Jansen
- Department of Biomaterials, Radboud University Medical Center, Philips van Leijdenlaan 25, 6525 EX, Nijmegen, The Netherlands
| | - X Frank Walboomers
- Department of Biomaterials, Radboud University Medical Center, Philips van Leijdenlaan 25, 6525 EX, Nijmegen, The Netherlands
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T1- and T2*-Mapping for Assessment of Tendon Tissue Biophysical Properties: A Phantom MRI Study. Invest Radiol 2019; 54:212-220. [PMID: 30444794 DOI: 10.1097/rli.0000000000000532] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The aim of this study was to quantitatively assess changes in collagen structure using MR T1- and T2*-mapping in a novel controlled ex vivo tendon model setup. MATERIALS AND METHODS Twenty-four cadaveric bovine flexor tendons underwent MRI at 3 T before and after chemical modifications, representing mechanical degeneration and augmentation. Collagen degradation (COL), augmenting collagen fiber cross-linking (CXL), and a control (phosphate-buffered saline [PBS]) were examined in experimental groups, using histopathology as standard of reference. Variable echo-time and variable-flip angle gradient-echo sequences were used for T2*- and T1-mapping, respectively. Standard T1- and T2-weighted spin-echo sequences were acquired for visual assessment of tendon texture. Tendons were assessed subsequently for their biomechanical properties and compared with quantitative MRI analysis. RESULTS T1- and T2*-mapping was feasible and repeatable for untreated (mean, 545 milliseconds, 2.0 milliseconds) and treated tendons. Mean T1 and T2* values of COL, CXL, and PBS tendons were 1459, 934, and 1017 milliseconds, and 5.5, 3.6, and 2.5 milliseconds, respectively. T2* values were significantly different between enzymatically degraded tendons, cross-linked tendons, and controls, and were significantly correlated with mechanical tendon properties (r = -0.74, P < 0.01). T1 values and visual assessment could not differentiate CXL from PBS tendons. Photo-spectroscopy showed increased autofluorescence of cross-linked tendons, whereas histopathology verified degenerative lesions of enzymatically degraded tendons. CONCLUSIONS T2*-mapping has the potential to detect and quantify subtle changes in tendon collagen structure not visible on conventional clinical MRI. Tendon T2* values might serve as a biomarker for biochemical alterations associated with tendon pathology.
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Parthasarathy J, Krishnamurthy R, Ostendorf A, Shinoka T, Krishnamurthy R. 3D printing with MRI in pediatric applications. J Magn Reson Imaging 2019; 51:1641-1658. [PMID: 31329332 DOI: 10.1002/jmri.26870] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 07/01/2019] [Accepted: 07/01/2019] [Indexed: 12/12/2022] Open
Abstract
3D printing (3DP) applications for clinical evaluation, preoperative planning, patient and trainee education, and simulation has increased in the past decade. Most of the applications are found in cardiovascular, head and neck, orthopedic, neurological, urological, and oncological surgical cases. This review has three parts. The first part discusses the technical pathway to realizing a physical model, 3DP considerations in pediatric MRI image acquisition, data and resolution requirements, and related structural segmentation and postprocessing steps needed to generalize both virtual and physical models. Standard practices and processing software used in these processes will be assessed. The second part discusses complementary examples in pediatric applications, including cases from cardiology, neuroradiology, neurology, and neurosurgery, head and neck, orthopedics, pelvic and urological applications, oncological applications, and fetal imaging. The third part explores other 3D printing applications and considerations such as using 3DP to develop tissue-specific phantoms and devices for testing in the MR environment, to educate patients and their families, to train clinicians and students, and facility requirements for building a 3DP program. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2020;51:1641-1658.
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Affiliation(s)
| | | | - Adam Ostendorf
- Department of Neurology Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Toshiharu Shinoka
- Department of Cardiothoracic Surgery, Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Rajesh Krishnamurthy
- The Department of Radiology, Nationwide Children's Hospital, Columbus, Ohio, USA
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Bae WC, Ruangchaijatuporn T, Chung CB. New Techniques in MR Imaging of the Ankle and Foot. Magn Reson Imaging Clin N Am 2017; 25:211-225. [PMID: 27888849 DOI: 10.1016/j.mric.2016.08.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Foot and ankle disorders are common in everyday clinical practice. MR imaging is frequently required for diagnosis given the variety and complexity of foot and ankle anatomy. Although conventional MR imaging plays a significant role in diagnosis, contemporary management increasingly relies on advanced imaging for monitoring therapeutic response. There is an expanding need for identification of biomarkers for musculoskeletal tissues. Advanced imaging techniques capable of imaging these tissue substrates will be increasingly used in routine clinical practice. Radiologists should therefore become familiar with these innovative MR techniques. Many such techniques are already widely used in other organ systems.
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Affiliation(s)
- Won C Bae
- Radiology Service, Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, MC 114, San Diego, CA 92161, USA; Department of Radiology, UCSD MSK Imaging Research Lab, University of California, San Diego, 9427 Health Sciences Drive, La Jolla, CA 92093-0997, USA
| | - Thumanoon Ruangchaijatuporn
- Department of Diagnostic and Therapeutic Radiology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, 270 Rama VI Road, Ratchatewi, Bangkok 10400, Thailand
| | - Christine B Chung
- Radiology Service, Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, MC 114, San Diego, CA 92161, USA; Department of Radiology, UCSD MSK Imaging Research Lab, University of California, San Diego, 9427 Health Sciences Drive, La Jolla, CA 92093-0997, USA.
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Abstract
OBJECTIVE The purposes of this article are to present a state-of-the-art routine protocol for MRI of the ankle, to provide problem-solving tools based on specific clinical indications, and to introduce principles for the implementation of ultrashort echo time MRI of the ankle, including morphologic and quantitative assessment. CONCLUSION Ankle injury is common among both athletes and the general population, and MRI is the established noninvasive means of evaluation. The design of an ankle protocol depends on various factors. Higher magnetic field improves signal-to-noise ratio but increases metal artifact. Specialized imaging planes are useful but prolong acquisition times. MR neurography is useful, but metal reduction techniques are needed whenever a metal prosthesis is present. An ultrashort echo time sequence is a valuable tool for both structural and quantitative evaluation.
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Menikou G, Yiannakou M, Yiallouras C, Ioannides C, Damianou C. MRI-compatible bone phantom for evaluating ultrasonic thermal exposures. ULTRASONICS 2016; 71:12-19. [PMID: 27261569 DOI: 10.1016/j.ultras.2016.05.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 05/15/2016] [Accepted: 05/24/2016] [Indexed: 06/05/2023]
Abstract
OBJECTIVE The goal of the proposed study was the development of a magnetic resonance imaging (MRI) compatible bone phantom suitable for evaluating focused ultrasound protocols. MATERIALS AND METHODS High resolution CT images were used to segment femur bone. The segmented model was manufactured with (Acrylonitrile Butadiene Styrene) ABS plastic using a 3-D printer. The surrounding skeletal muscle tissue was mimicked using an agar-silica-evaporated milk gel (2% w/v-2% w/v-40% v/v). MR thermometry was used to evaluate the exposures of the bone phantom to focused ultrasound. RESULTS The estimated agar-silica-evaporated milk gel's T1 and T2 relaxation times in a 1.5T magnetic field were 776ms and 66ms respectively. MR thermometry maps indicated increased temperature adjacent to the bone, which was also shown in situations of real bone/tissue interfaces. CONCLUSION Due to growing interest of using MRI guided Focused Ultrasound Surgery (MRgFUS) in palliating bone cancer patients at terminal stages of the disease, the proposed bone phantom can be utilized as a very useful tool for evaluating ultrasonic protocols, thus minimizing the need for animal models. The estimated temperature measured and its distribution near the bone phantom/agar interface which was similar to temperatures recorded in real bone ablation with FUS, confirmed the phantom's functionality.
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Affiliation(s)
| | | | - Christos Yiallouras
- Cyprus University of Technology, Limassol, Cyprus; MEDSONIC LTD, Limassol, Cyprus
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Chang EY, Du J, Biswas R, Statum S, Pauli C, Bae WC, Chung CB. Off-resonance saturation ratio obtained with ultrashort echo time-magnetization transfer techniques is sensitive to changes in static tensile loading of tendons and degeneration. J Magn Reson Imaging 2015; 42:1064-71. [PMID: 25808266 DOI: 10.1002/jmri.24881] [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: 10/22/2014] [Accepted: 02/18/2015] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND To determine if off-saturation ratio (OSR) measured with the ultrashort echo time magnetization transfer (UTE-MT) sequence could differentiate between tendons under different states of tensile load and to compare these changes between normal versus degenerated tendons. METHODS Fourteen tendons were imaged at 3 Tesla before and during the application of 0.5-1 kg tension. A two-dimensional (2D) -UTE-MT sequence with 1.5, 3, and 5 kHz frequency offsets was used on nine tendons and a 3D-UTE-MT sequence with 1.5 kHz frequency offset was used on five tendons. OSR was calculated and compared for each condition. Histologic correlation was performed using light microscopy. RESULTS In general, OSR increased after the application of tension. Mean increase of 2D OSR was 0.035 (95% confidence interval [CI], 0.013-0.056) at 1.5 kHz offset (P < 0.01), 0.031 (95% CI, 0.023-0.040) at 3 kHz offset (P < 0.01), and 0.013 (95% CI, -0.013-0.027) at 5 kHz offset (P = 0.07) from pre- to posttension states. Mean increase of 3D OSR was 0.026 (95% CI, 0.008-0.044) at a 1.5 kHz offset (P = 0.02) from pre- to posttension states. Mean decrease of 2D OSR at 1.5 kHz offset was 0.074-0.087 when comparing normal versus degenerated tendons (P < 0.01). CONCLUSION OSR as measured with 2D or 3D UTE-MT sequences can detect the changes in hydration seen when tendons are placed under two different states of tensile load, but these changes are smaller than those encountered when comparing between normal versus pathologic tendons. Lower off-resonance saturation frequencies (3 kHz or less) are more sensitive to these changes than higher off-resonance saturation frequencies.
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Affiliation(s)
- Eric Y Chang
- Radiology Service, VA San Diego Healthcare System, San Diego, California, USA.,Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
| | - Jiang Du
- Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
| | - Reni Biswas
- Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
| | - Sheronda Statum
- Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
| | - Chantal Pauli
- Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland
| | - Won C Bae
- Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
| | - Christine B Chung
- Radiology Service, VA San Diego Healthcare System, San Diego, California, USA.,Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
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Chang EY, Du J, Chung CB. UTE imaging in the musculoskeletal system. J Magn Reson Imaging 2014; 41:870-83. [PMID: 25045018 DOI: 10.1002/jmri.24713] [Citation(s) in RCA: 173] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/08/2014] [Accepted: 07/03/2014] [Indexed: 12/12/2022] Open
Abstract
Tissues, such as bone, tendon, and ligaments, contain a high fraction of components with "short" and "ultrashort" transverse relaxation times and therefore have short mean transverse relaxation times. With conventional magnetic resonance imaging (MRI) sequences that employ relatively long echo times (TEs), there is no opportunity to encode the decaying signal of short and ultrashort T2 /T2 * tissues before it has reached zero or near zero. The clinically compatible ultrashort TE (UTE) sequence has been increasingly used to study the musculoskeletal system. This article reviews the UTE sequence as well as various modifications that have been implemented since its introduction. These modifications have been used to improve efficiency or contrast as well as provide quantitative analysis. This article reviews several clinical musculoskeletal applications of UTE.
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Affiliation(s)
- Eric Y Chang
- Department of Radiology, VA San Diego Healthcare System, San Diego, California, USA; Department of Radiology, University of California, San Diego Medical Center, San Diego, California, USA
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Kirsch S, Kreinest M, Reisig G, Schwarz MLR, Ströbel P, Schad LR. In vitro mapping of 1H ultrashort T2* and T2 of porcine menisci. NMR IN BIOMEDICINE 2013; 26:1167-1175. [PMID: 23505140 DOI: 10.1002/nbm.2931] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 12/14/2012] [Accepted: 01/23/2013] [Indexed: 06/01/2023]
Abstract
In this study, mapping of ultrashort T2 and T2* of acutely isolated porcine menisci at B0 = 9.4 T was investigated. Maps of T2 were measured from a slice through the pars intermedia with a spin echo-prepared two-dimensional ultrashort-TE T2 mapping technique published previously. T2* mapping was performed by two-dimensional ultrashort-TE MRI with variable acquisition delay. The measured signal decays were fitted by monoexponential, biexponential and Gaussian-exponential fitting functions. The occurrence of Gaussian-like signal decays is outlined theoretically. The quality of the curve fits was visualized by mapping the value δ = abs(1 - χ(2) red). For T2 mapping, the Gaussian-exponential fit showed the best performance, whereas the monoexponential and biexponential fits showed regionally high values of δ (δ > 20). Interpretation of the Gaussian-exponential parameter maps was found to be difficult, because a Gaussian signal component can be related to mesoscopic (collagen texture) or macroscopic (slice profile, shim, sample geometry) magnetic field inhomogeneities and/or residual (1) H dipole-dipole couplings. It seems likely that an interplay of these effects yielded the observed signal decays. Modulation of the T2* signal decay caused by chemical shift was observed and addressed to fat protons by means of histology. In the T2 measurements, no modulation of the signal decay was observed and the biexponential and Gaussian-exponential fits showed the best performance with comparable values of δ. Our results suggest that T2 mapping provides the more robust method for the characterization of meniscal tissue by means of MRI relaxometry. However, mapping of ultrashort T2, as performed in this study, is time consuming and provides less signal-to-noise ratio per time than the mapping of T2*. If T2* mapping is used, pixel-wise monitoring of the fitting quality based on reduced χ(2) should be employed and great care should be taken when interpreting the parameter maps of the fits.
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Affiliation(s)
- S Kirsch
- Department of Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
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Garwood M. MRI of fast-relaxing spins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 229:49-54. [PMID: 23465800 PMCID: PMC3602136 DOI: 10.1016/j.jmr.2013.01.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Revised: 01/29/2013] [Accepted: 01/29/2013] [Indexed: 06/01/2023]
Abstract
MR imaging of extremely fast-relaxing spins is currently a topic of much interest due to recent technical innovations and groundbreaking studies demonstrating its utility in biomedical research applications. From a technical perspective, this article examines the different classes of pulse sequences currently available to image spins with ultra-short transverse relaxation times (T2 and T2*), with particular attention focused on the newest member of the class, sweep imaging with Fourier transformation (SWIFT).
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Affiliation(s)
- Michael Garwood
- The Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA.
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Abstract
MR imaging of extremely fast-relaxing spins is currently a topic of much interest due to recent technical innovations and groundbreaking studies demonstrating its utility in biomedical research applications. From a technical perspective, this article examines the different classes of pulse sequences currently available to image spins with ultra-short transverse relaxation times (T2 and T2*), with particular attention focused on the newest member of the class, sweep imaging with Fourier transformation (SWIFT).
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Affiliation(s)
- Michael Garwood
- The Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 55455, USA.
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