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Shin HG, Li X, Heo HY, Knutsson L, Szczepankiewicz F, Nilsson M, van Zijl PCM. Compartmental anisotropy of filtered exchange imaging (FEXI) in human white matter: What is happening in FEXI? Magn Reson Med 2024; 92:660-675. [PMID: 38525601 PMCID: PMC11142880 DOI: 10.1002/mrm.30086] [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: 09/04/2023] [Revised: 01/30/2024] [Accepted: 02/28/2024] [Indexed: 03/26/2024]
Abstract
PURPOSE To investigate the effects of compartmental anisotropy on filtered exchange imaging (FEXI) in white matter (WM). THEORY AND METHODS FEXI signals were measured using multiple combinations of diffusion filter and detection directions in five healthy volunteers. Additional filters, including a trace-weighted diffusion filter with trapezoidal gradients, a spherical b-tensor encoded diffusion filter, and a T2 filter, were tested with trace-weighted diffusion detection. RESULTS A large range of apparent exchange rates (AXR) and both positive and negative filter efficiencies (σ) were found depending on the mutual orientation of the filter and detection gradients relative to WM fiber orientation. The data demonstrated that the fast-diffusion compartment suppressed by diffusional filtering is not exclusively extra-cellular, but also intra-cellular. While not comprehensive, a simple two-compartment diffusion tensor model with water exchange was able to account qualitatively for the trends in positive and negative filtering efficiencies, while standard model imaging (SMI) without exchange could not. This two-compartment diffusion tensor model also demonstrated smaller AXR variances across subjects. When employing trace-weighted diffusion detection, AXR values were on the order of the R1 (=1/T1) of water at 3T for crossing fibers, while being less than R1 for parallel fibers. CONCLUSION Orientation-dependent AXR and σ values were observed when using multi-orientation filter and detection gradients in FEXI, indicating that WM FEXI models need to account for compartmental anisotropy. When using trace-weighted detection, AXR values were on the order of or less than R1, complicating the interpretation of FEXI results in WM in terms of biological exchange properties. These findings may contribute toward better understanding of FEXI results in WM.
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Affiliation(s)
- Hyeong-Geol Shin
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Xu Li
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Hye-Young Heo
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Linda Knutsson
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Medical Radiation Physics, Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Filip Szczepankiewicz
- Department of Medical Radiation Physics, Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Markus Nilsson
- Department of Radiology, Clinical Sciences Lund, Lund University, Lund, Sweden
- Department of Medical Imaging and Physiology, Skåne University Hospital, Lund, Sweden
| | - Peter C M van Zijl
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Fiorito M, Yushchenko M, Cicolari D, Sarracanie M, Salameh N. Fast, interleaved, Look-Locker-based T 1 mapping with a variable averaging approach: Towards temperature mapping at low magnetic field. NMR IN BIOMEDICINE 2023; 36:e4826. [PMID: 36057925 PMCID: PMC10078420 DOI: 10.1002/nbm.4826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 08/18/2022] [Accepted: 08/30/2022] [Indexed: 06/15/2023]
Abstract
Proton resonance frequency shift (PRFS) is currently the gold standard method for magnetic resonance thermometry. However, the linearity between the temperature-dependent phase accumulation and the static magnetic field B0 confines its use to rather high-field scanners. Applications such as thermal therapies could naturally benefit from lower field MRI settings through leveraging increased accessibility, a lower physical and economical footprint, and further consideration of the technical challenges associated with the integration of heating systems into conventional clinical scanners. T 1 -based thermometry has been proposed as an alternative to the gold standard; however, because of longer acquisition times, it has found clinical use solely with adipose tissue where PRFS fails. At low field, the enhanced T 1 dispersion, combined with reduced relaxation times, make T 1 mapping an appealing candidate. Here, an interleaved Look-Locker-based T 1 mapping sequence was proposed for temperature quantification at 0.1 T. A variable averaging scheme was introduced, to maximize the signal-to-noise ratio throughout T 1 recovery. In calibrated samples, an average T 1 accuracy of 85% ± 4% was achieved in 10 min, compared with the 77% ± 7% obtained using a standard averaging scheme. Temperature maps between 29.0 and 41.7°C were eventually reconstructed, with a precision of 3.0 ± 1.1°C and an accuracy of 1.5 ± 1.0°C. Accounting for longer thermal treatments and less strict temperature constraints, applications such as MR-guided mild hyperthermia treatments at low field could be envisioned.
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Affiliation(s)
- Marco Fiorito
- Department of Biomedical EngineeringCenter for Adaptable MRI Technology, University of BaselAllschwilSwitzerland
| | - Maksym Yushchenko
- Department of Biomedical EngineeringCenter for Adaptable MRI Technology, University of BaselAllschwilSwitzerland
| | | | - Mathieu Sarracanie
- Department of Biomedical EngineeringCenter for Adaptable MRI Technology, University of BaselAllschwilSwitzerland
| | - Najat Salameh
- Department of Biomedical EngineeringCenter for Adaptable MRI Technology, University of BaselAllschwilSwitzerland
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Acceleration of neuromelanin-sensitive MRI sequences in the substantia nigra using standard MRI options. Neuroradiology 2023; 65:307-312. [PMID: 36169662 PMCID: PMC9859863 DOI: 10.1007/s00234-022-03058-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 09/19/2022] [Indexed: 01/25/2023]
Abstract
PURPOSE Neuromelanin MRI (NM-MRI) is applied as a proxy measurement of dopaminergic functioning of the substantia nigra pars compacta (SN). To increase its clinical applicability, a fast and easily applicable NM-MRI sequence is needed. This study therefore compared accelerated NM-MRI sequences using standard available MRI options with a validated 2D gradient recalled echo NM-MRI sequence with off-resonance magnetization transfer (MT) pulse (2D-MToffRes). METHODS We used different combinations of compressed sense (CS) acceleration, repetition times (TR), and MT pulse to accelerate the validated 2D-MToffRes. In addition, we compared a recently introduced 3D sequence with the 2D-MToffRes. RESULTS Our results show that the 2D sequences perform best with good to excellent reliability. Only excellent intraclass correlation coefficients were found for the CS factor 2 sequences. CONCLUSION We conclude that there are several reliable approaches to accelerate NM-MRI, in particular by using CS.
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Snyder J, McPhee KC, Wilman AH. T 2 quantification in brain using 3D fast spin-echo imaging with long echo trains. Magn Reson Med 2021; 87:2145-2160. [PMID: 34894641 PMCID: PMC9299830 DOI: 10.1002/mrm.29113] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 11/16/2021] [Accepted: 11/17/2021] [Indexed: 11/15/2022]
Abstract
Purpose Three‐dimensional fast spin‐echo (FSE) sequences commonly use very long echo trains (>64 echoes) and severely reduced refocusing angles. They are increasingly used in brain exams due to high, isotropic resolution and reasonable scan time when using long trains and short interecho spacing. In this study, T2 quantification in 3D FSE is investigated to achieve increased resolution when comparing with established 2D (proton‐density dual‐echo and multi‐echo spin‐echo) methods. Methods The FSE sequence design was explored to use long echo trains while minimizing T2 fitting error and maintaining typical proton density and T2‐weighted contrasts. Constant and variable flip angle trains were investigated using extended phase graph and Bloch equation simulations. Optimized parameters were analyzed in phantom experiments and validated in vivo in comparison to 2D methods for eight regions of interest in brain, including deep gray‐matter structures and white‐matter tracts. Results Phantom and healthy in vivo brain T2 measurements showed that optimized variable echo‐train 3D FSE performs similarly to previous 2D methods, while achieving three‐fold‐higher slice resolution, evident visually in the 3D T2 maps. Optimization resulted in better T2 fitting and compared well with standard multi‐echo spin echo (within the 8‐ms confidence limits defined based on Bland‐Altman analysis). Conclusion T2 mapping using 3D FSE with long echo trains and variable refocusing angles provides T2 accuracy in agreement with 2D methods with additional high‐resolution benefits, allowing isotropic views while avoiding incidental magnetization transfer effects. Consequently, optimized 3D sequences should be considered when choosing T2 mapping methods for high anatomic detail.
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Affiliation(s)
- Jeff Snyder
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
| | | | - Alan H Wilman
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
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Luu HM, Kim DH, Kim JW, Choi SH, Park SH. qMTNet: Accelerated quantitative magnetization transfer imaging with artificial neural networks. Magn Reson Med 2020; 85:298-308. [PMID: 32643202 DOI: 10.1002/mrm.28411] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 12/11/2022]
Abstract
PURPOSE To develop a set of artificial neural networks, collectively termed qMTNet, to accelerate data acquisition and fitting for quantitative magnetization transfer (qMT) imaging. METHODS Conventional and interslice qMT data were acquired with two flip angles at six offset frequencies from seven subjects for developing the networks and from four young and four older subjects for testing the generalizability. Two subnetworks, qMTNet-acq and qMTNet-fit, were developed and trained to accelerate data acquisition and fitting, respectively. qMTNet-2 is the sequential application of qMTNet-acq and qMTNet-fit to produce qMT parameters (exchange rate, pool fraction) from undersampled qMT data (two offset frequencies rather than six). qMTNet-1 is one single integrated network having the same functionality as qMTNet-2. qMTNet-fit was compared with a Gaussian kernel-based fitting. qMT parameters generated by the networks were compared with those from ground truth fitted with a dictionary-driven approach. RESULTS The proposed networks achieved high peak signal-to-noise ratio (>30) and structural similarity index (>97) in reference to the ground truth. qMTNet-fit produced qMT parameters in concordance with the ground truth with better performance than the Gaussian kernel-based fitting. qMTNet-2 and qMTNet-1 could accelerate data acquisition at threefold and accelerate fitting at 5800- and 4218-fold, respectively. qMTNet-1 showed slightly better performance than qMTNet-2, whereas qMTNet-2 was more flexible for applications. CONCLUSION The proposed single (qMTNet-1) and two joint neural networks (qMTNet-2) can accelerate qMT workflow for both data acquisition and fitting significantly. qMTNet has the potential to accelerate qMT imaging for clinical applications, which warrants further investigation.
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Affiliation(s)
- Huan Minh Luu
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Dong-Hyun Kim
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Jae-Woong Kim
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Seung-Hong Choi
- Department of Radiology, Seoul National University College of Medicine, Seoul, Korea
| | - Sung-Hong Park
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
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Murata S, Tachibana Y, Murata K, Kamagata K, Hori M, Andica C, Suzuki M, Wada A, Kumamaru K, Hagiwara A, Irie R, Sato S, Hamasaki N, Fukunaga I, Hoshito H, Aoki S. Comparison of magnetization transfer contrast of conventional and simultaneous multislice turbo spin echo acquisitions focusing on excitation time interval. Jpn J Radiol 2019; 37:579-589. [PMID: 31230186 DOI: 10.1007/s11604-019-00848-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 06/14/2019] [Indexed: 10/26/2022]
Abstract
PURPOSE Image contrast differs between conventional multislice turbo spin echo (conventional TSE) and multiband turbo spin echo (SMS-TSE). Difference in time interval between excitations for adjacent slices (SETI) might cause this difference. This study aimed to evaluate the influence of SETI on MT effect for conventional TSE and compare conventional TSE with SMS-TSE in this respect. MATERIALS AND METHODS Three different agar concentration phantoms were scanned with conventional TSE by adjusting SETI and TR. Signal change for different SETI was evaluated using Pearson's correlation analysis. SMS-TSE was acquired by changing TR similarly. Three human volunteers were scanned with similar settings to evaluate reproducibility of the phantom results in human brain. RESULTS In conventional TSE, shorter SETI induced larger signal reduction. Longer TR and higher agar concentration emphasized this characteristic. Significant linear correlation (P < 0.05) was found in the major cases. The SMS-TSE signal intensity in each TR and phantom was smaller than the assumable levels in conventional TSE when the slices were simultaneously excited. Similar characteristic was observed in human brain. CONCLUSION Shorter SETI results in larger MT effect in conventional TSE. The contrast change in SMS-TSE was larger than the supposable level from simultaneous excitation, which needs consideration in clinics.
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Affiliation(s)
- Syo Murata
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yasuhiko Tachibana
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. .,Applied MRI Research, Department of Molecular Imaging and Theranostics, NIRS, QST, Chiba, Japan.
| | | | - Koji Kamagata
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masaaki Hori
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Christina Andica
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Michimasa Suzuki
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Akihiko Wada
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kanako Kumamaru
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Akifumi Hagiwara
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.,Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Ryusuke Irie
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.,Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Shuji Sato
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Nozomi Hamasaki
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Issei Fukunaga
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Haruyoshi Hoshito
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Shigeki Aoki
- Department of Radiology, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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Kim J, Lee S, Choi SH, Park S. Rapid framework for quantitative magnetization transfer imaging with interslice magnetization transfer and dictionary‐driven fitting approaches. Magn Reson Med 2019; 82:1671-1683. [DOI: 10.1002/mrm.27850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 05/16/2019] [Accepted: 05/20/2019] [Indexed: 01/02/2023]
Affiliation(s)
- Jae‐Woong Kim
- Magnetic Resonance Imaging Laboratory, Department of Bio and Brain Engineering Korea Advanced Institute of Science and Technology Daejeon Korea
| | - Sul‐Li Lee
- Magnetic Resonance Imaging Laboratory, Department of Bio and Brain Engineering Korea Advanced Institute of Science and Technology Daejeon Korea
| | - Seung Hong Choi
- Department of Radiology Seoul National University College of Medicine Seoul Korea
| | - Sung‐Hong Park
- Magnetic Resonance Imaging Laboratory, Department of Bio and Brain Engineering Korea Advanced Institute of Science and Technology Daejeon Korea
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Shin HG, Oh SH, Fukunaga M, Nam Y, Lee D, Jung W, Jo M, Ji S, Choi JY, Lee J. Advances in gradient echo myelin water imaging at 3T and 7T. Neuroimage 2019; 188:835-844. [DOI: 10.1016/j.neuroimage.2018.11.040] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/22/2018] [Accepted: 11/22/2018] [Indexed: 12/18/2022] Open
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McPhee KC, Wilman AH. T
1
and T
2
quantification from standard turbo spin echo images. Magn Reson Med 2018; 81:2052-2063. [DOI: 10.1002/mrm.27495] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/10/2018] [Accepted: 07/23/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Kelly C. McPhee
- Department of Physics University of Alberta Edmonton Alberta Canada
- Department of Biomedical Engineering University of Alberta Edmonton Alberta Canada
| | - Alan H. Wilman
- Department of Physics University of Alberta Edmonton Alberta Canada
- Department of Biomedical Engineering University of Alberta Edmonton Alberta Canada
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Kobayashi A, Shibukawa S, Takano S, Muro I. [Effect of Contrast on FLAIR by Changing the Number of Packages]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2018; 74:1180-1185. [PMID: 30344215 DOI: 10.6009/jjrt.2018_jsrt_74.10.1180] [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] [Indexed: 06/08/2023]
Abstract
We have found that the number of packages influences contrast for brain tissue signals on fluid-attenuated inversion recovery (FLAIR). The purpose of this study was to evaluate the contrast of white and gray matters by changing the number of packages. In a volunteer study (n=8), FLAIR images were obtained with the various number of packages (number of package=2, 3, 4, 5). We investigated the same imaging condition at both 1.5 and 3.0T. The signal intensity of white and gray matters in all volunteers was increased as increasing the number of packages. Moreover, the contrast ratio between white and gray matters was slightly decreased. In our conclusion, the contrast between the gray and white matters on FLAIR was influenced by the number of packages.
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Affiliation(s)
| | | | | | - Isao Muro
- Department of Radiology, Tokai University Hospital
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Uddin MN, McPhee KC, Blevins G, Wilman AH. Recovery of accurate T 2 from historical 1.5 tesla proton density and T 2 -weighted images: Application to 7-year T 2 changes in multiple sclerosis brain. Magn Reson Imaging 2017; 37:21-26. [DOI: 10.1016/j.mri.2016.11.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 11/11/2016] [Accepted: 11/12/2016] [Indexed: 01/12/2023]
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12
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Uddin MN, Marc Lebel R, Wilman AH. Transverse relaxometry with reduced echo train lengths via stimulated echo compensation. Magn Reson Med 2013; 70:1340-6. [DOI: 10.1002/mrm.24568] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Revised: 10/24/2012] [Accepted: 10/29/2012] [Indexed: 11/06/2022]
Affiliation(s)
- Md Nasir Uddin
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
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Kajisako M, Miyati T, Taniguchi M, Syakudo Y, Koizumi K, Hiraga A, Miki Y. [Evaluation of crosstalk effect on spin-echo images at 1.5 and 3 T]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2011; 67:779-784. [PMID: 21799279 DOI: 10.6009/jjrt.67.779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The purpose of this study is to evaluate the crosstalk effect on spin-echo (SE) images at 1.5 and 3 T MRI. We examined the influence of crosstalk by comparing the full width at half-maximum (FWHM) and slice profile of images of a wedge-shaped phantom for various slice gaps. We also assessed crosstalk effect in the brain by comparing image contrast among healthy volunteers (n=8). Among the subjects, the shapes of the slice profiles at 1.5 T were similar to those at 3 T for long repetition times (TRs); however, at shorter TRs, differences in slice profiles were observed among the subjects and were more apparent at 3 than at 1.5 T. The relative contrast between white matter and gray matter on T(1)-weighted images was lower at 3 than at 1.5 T. The crosstalk effect was strongest when the TR of the excitation pulse was short. The influence of the adjacent excitation pulse is important in the process of T(1) relaxation because T(1) values are greater at 3 T. In conclusion, the influence of crosstalk on SE T(1)-weighted images is greater at 3 than at 1.5 T.
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Spin-echo T1-weighted imaging of the brain with interleaved acquisition and presaturation pulse at 3 T: a feasibility study before clinical use. Acad Radiol 2009; 16:852-7. [PMID: 19375955 DOI: 10.1016/j.acra.2008.12.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 12/25/2008] [Accepted: 12/30/2008] [Indexed: 11/22/2022]
Abstract
RATIONALE AND OBJECTIVES Although spin-echo (SE) sequence has some advantages over gradient-echo sequence in brain imaging, gradient-echo sequence is commonly used for T1-weighted imaging (T1WI) at 3 T because contrast on SE T1WI is widely believed to be poor at 3 T. Recently, gray-white matter contrast on single-slice and multi-slice SE imaging with interslice gap was reported as better at 3 T than at 1.5 T. This study examined the feasibility of interleaved SE T1WI of the brain at 3 T. This study also examined whether presaturation pulse (PP) sufficiently suppresses intra-arterial signals because these signals tend to be hyperintense due to longer T1 at 3 T. MATERIALS AND METHODS Subjects consisted of 18 healthy volunteers. Two sets of T1WI were performed using SE sequence. One set consisted of imaging without PP, and the other consisted of imaging with PP. Each set contained three types of gapless imaging as follows; sequential, 100% interleaved, and 200% interleaved imaging. In each subject, contrast-to-noise ratio between gray-matter and white-matter (CNR(GM-WM)) and intra-arterial signals were evaluated. RESULTS CNR(GM-WM) was significantly higher on interleaved images than on sequential images, regardless of PP (P < .0001). PP sufficiently suppressed intra-arterial signals (P < .0001). CONCLUSION CNR(GM-WM) on SE T1WI at 3 T can be improved by interleaved acquisition, and PP sufficiently suppressed intra-arterial signals. Interleaved SE T1WI with PP appears clinically feasible at 3 T.
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Turner R, Oros-Peusquens AM, Romanzetti S, Zilles K, Shah NJ. Optimised in vivo visualisation of cortical structures in the human brain at 3 T using IR-TSE. Magn Reson Imaging 2008; 26:935-42. [DOI: 10.1016/j.mri.2008.01.043] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 01/14/2008] [Indexed: 11/26/2022]
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Meara SJP, Barker GJ. Impact of incidental magnetization transfer effects on inversion-recovery sequences that use a fast spin-echo readout. Magn Reson Med 2008; 58:825-9. [PMID: 17899590 DOI: 10.1002/mrm.21338] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Multislice MR images obtained using a fast spin-echo (FSE) readout are strongly affected by magnetization transfer (MT) effects, which will cause a decrease in the observed longitudinal relaxation times for tissues with a large bound water component. This is pertinent for FSE-based inversion-recovery (IR) sequences, as it would be expected to cause a change in the required inversion times. Furthermore, the effect will be greater as the number of slices that are acquired within the repetition time (TR) is increased. A pseudo-3D IR-FSE sequence was used to obtain images of a phantom consisting of thermally crosslinked bovine serum albumin. It was found that increasing the number of slabs acquired per TR period led to a decrease in the inversion time that maximally suppressed the signal from the MT phantom; this was not the case for water. This has important consequences for any IR imaging sequence that uses an FSE readout.
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Affiliation(s)
- Simon J P Meara
- Imaging Science and Biomedical Engineering Research Group, University of Manchester, Manchester, United Kingdom.
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