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Su S, Zhao Y, Ding Y, Lau V, Xiao L, Leung GKK, Lau GKK, Huang F, Vardhanabhuti V, Leong ATL, Wu EX. Ultra-low-field magnetization transfer imaging at 0.055T with low specific absorption rate. Magn Reson Med 2024. [PMID: 39044654 DOI: 10.1002/mrm.30231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 06/14/2024] [Accepted: 07/09/2024] [Indexed: 07/25/2024]
Abstract
PURPOSE To demonstrate magnetization transfer (MT) effects with low specific absorption rate (SAR) on ultra-low-field (ULF) MRI. METHODS MT imaging was implemented by using sinc-modulated RF pulse train (SPT) modules to provide bilateral off-resonance irradiation. They were incorporated into 3D gradient echo (GRE) and fast spin echo (FSE) protocols on a shielding-free 0.055T head scanner. MT effects were first verified using phantoms. Brain MT imaging was conducted in both healthy subjects and patients. RESULTS MT effects were clearly observed in phantoms using six SPT modules with total flip angle 3600° at central primary saturation bands of approximate offset ±786 Hz, even in the presence of large relative B0 inhomogeneity. For brain, strong MT effects were observed in gray matter, white matter, and muscle in 3D GRE and FSE imaging using six and sixteen SPT modules with total flip angle 3600° and 9600°, respectively. Fat, cerebrospinal fluid, and blood exhibited relatively weak MT effects. MT preparation enhanced tissue contrasts in T2-weighted and FLAIR-like images, and improved brain lesion delineation. The estimated MT SAR was 0.0024 and 0.0008 W/kg for two protocols, respectively, which is far below the US Food and Drug Administration (FDA) limit of 3.0 W/kg. CONCLUSION Robust MT effects can be readily obtained at ULF with extremely low SAR, despite poor relative B0 homogeneity in ppm. This unique advantage enables flexible MT pulse design and implementation on low-cost ULF MRI platforms to achieve strong MT effects in brain and beyond, potentially augmenting their clinical utility in the future.
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Affiliation(s)
- Shi Su
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Yujiao Zhao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Ye Ding
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Vick Lau
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Linfang Xiao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Gilberto K K Leung
- Department of Surgery, The University of Hong Kong, Hong Kong SAR, China
| | - Gary K K Lau
- Department of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Fan Huang
- Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong SAR, China
| | - Vince Vardhanabhuti
- Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong SAR, China
| | - Alex T L Leong
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China
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Hou J, Wong VWS, Qian Y, Jiang B, Chan AWH, Leung HHW, Wong GLH, Yu SCH, Chu WCW, Chen W. Detecting Early-Stage Liver Fibrosis Using Macromolecular Proton Fraction Mapping Based on Spin-Lock MRI: Preliminary Observations. J Magn Reson Imaging 2023; 57:485-492. [PMID: 35753084 DOI: 10.1002/jmri.28308] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 06/03/2022] [Accepted: 06/03/2022] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Liver fibrosis is characterized by macromolecule depositions. Recently, a novel technology termed macromolecular proton fraction quantification based on spin-lock magnetic resonance imaging (MPF-SL) is reported to measure macromolecule levels. HYPOTHESIS MPF-SL can detect early-stage liver fibrosis by measuring macromolecule levels in the liver. STUDY TYPE Retrospective. SUBJECTS Fifty-five participants, including 22 with no fibrosis (F0) and 33 with early-stage fibrosis (F1-2), were recruited. FIELD STRENGTH/SEQUENCE 3 T; two-dimensional (2D) MPF-SL turbo spin-echo sequence, 2D spin-lock T1rho turbo spin-echo sequence, and multi-slice 2D gradient echo sequence. ASSESSMENT Macromolecular proton fraction (MPF), T1rho, liver iron concentration (LIC), and fat fraction (FF) biomarkers were quantified within regions of interest. STATISTICAL TESTS Group comparison of the biomarkers using Mann-Whitney U tests; correlation between the biomarkers assessed using Spearman's rank correlation coefficient and linear regression with goodness-of-fit; fibrosis stage differentiation using receiver operating characteristic curve (ROC) analysis. P-value < 0.05 was considered statistically significant. RESULTS Average T1rho was 41.76 ± 2.94 msec for F0 and 41.15 ± 3.73 msec for F1-2 (P = 0.60). T1rho showed nonsignificant correlation with either liver fibrosis (ρ = -0.07; P = 0.61) or FF (ρ = -0.14; P = 0.35) but indicated a negative correlation with LIC (ρ = -0.66). MPF was 4.73 ± 0.45% and 5.65 ± 0.81% for F0 and F1-2 participants, respectively. MPF showed a positive correlation with liver fibrosis (ρ = 0.59), and no significant correlations with LIC (ρ = 0.02; P = 0.89) or FF (ρ = 0.05; P = 0.72). The area under the ROC curve was 0.85 (95% confidence interval [CI] 0.75-0.95) and 0.55 (95% CI 0.39-0.71; P = 0.55) for MPF and T1rho to discriminate between F0 and F1-2 fibrosis, respectively. DATA CONCLUSION MPF-SL has the potential to diagnose early-stage liver fibrosis and does not appear to be confounded by either LIC or FF. LEVEL OF EVIDENCE 3 TECHNICAL EFFICACY STAGE: 3.
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Affiliation(s)
- Jian Hou
- Department of Imaging and Interventional Radiology, Chinese University of Hong Kong, Hong Kong
| | - Vincent W-S Wong
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong.,State Key Laboratory of Digestive Disease, Chinese University of Hong Kong, Hong Kong.,Medical Data Analytics Centre, Chinese University of Hong Kong, Hong Kong
| | - Yurui Qian
- Department of Imaging and Interventional Radiology, Chinese University of Hong Kong, Hong Kong
| | - Baiyan Jiang
- Department of Imaging and Interventional Radiology, Chinese University of Hong Kong, Hong Kong
| | - Anthony W-H Chan
- Department of Anatomical and Cellular Pathology, Chinese University of Hong Kong, Hong Kong
| | - Howard H-W Leung
- Department of Anatomical and Cellular Pathology, Chinese University of Hong Kong, Hong Kong
| | - Grace L-H Wong
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong.,State Key Laboratory of Digestive Disease, Chinese University of Hong Kong, Hong Kong.,Medical Data Analytics Centre, Chinese University of Hong Kong, Hong Kong
| | - Simon C-H Yu
- Department of Imaging and Interventional Radiology, Chinese University of Hong Kong, Hong Kong
| | - Winnie C-W Chu
- Department of Imaging and Interventional Radiology, Chinese University of Hong Kong, Hong Kong
| | - Weitian Chen
- Department of Imaging and Interventional Radiology, Chinese University of Hong Kong, Hong Kong
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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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Zhang L, Wen B, Chen T, Tian H, Xue H, Ren H, Li L, Fan Q, Ren Z. A comparison study of inhomogeneous magnetization transfer (ihMT) and magnetization transfer (MT) in multiple sclerosis based on whole brain acquisition at 3.0 T. Magn Reson Imaging 2020; 70:43-49. [PMID: 32224092 DOI: 10.1016/j.mri.2020.03.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 03/19/2020] [Accepted: 03/25/2020] [Indexed: 11/16/2022]
Abstract
INTRODUCTION Multiple sclerosis (MS) is a central nervous system disorder that may eventually affect its function. The clinical standard for MS severity is based on a clinical scale, which lacks lesion specific information. Magnetic resonance imaging of MS faces the challenge of myelin specificity, and in this work a new method inhomogeneous magnetization transfer (ihMT) is investigated as new biomarker of demyelination in MS. METHODS Local ethics committee approved this study and written informed consents were obtained. Between Oct 2017 to May 2018, eighteen patients with relapsing-remitting MS (RRMS) (6 males, 12 females, mean age 31.2) and sixteen healthy volunteers (6 males, 10 females, mean age 30.4 years) were enrolled in this prospective study. All subjects underwent MRI exams including MT and ihMT imaging as well as the Expanded Disability Status Scale (EDSS) assessments. Independent sample t-test were used to compare the difference of ihMT parameters between healthy white matter (HWM) and normal appearing white matter (NAWM) and between HWM and MS lesions, respectively. Spearman correlation were used to analyze the correlation between ihMT parameters of MS lesions and EDSS score. RESULTS The ihMTR and qihMT demonstrate significant differences between WHM and NAWM groups, while no significant differences are observed for MTR and qMT. All parameters show significant differences between HWM and MS groups (p < 0.05). There was moderate negative correlation between MTR, qMT and EDSS score (-0.440 and -0.572), while there was a strong negative correlation between ihMTR and qihMT and EDSS score (-0.704 and -0.739). CONCLUSION Based on whole brain analysis at 3.0 T, ihMT showed better correlation with EDSS compared to magnetization transfer imaging, and may be a potentially valuable biomarker for demyelination in MS.
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Affiliation(s)
- Lei Zhang
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Baohong Wen
- Department of Radiology, Zhengzhou Univerisity First Affilicated Hospital, Zhengzhou, Henan, People's Republic of China
| | - Tao Chen
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Hongzhe Tian
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Hongqiang Xue
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Huipeng Ren
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Li Li
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Qing Fan
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China
| | - Zhuanqin Ren
- Department of Radiology, Baoji Center Hospital, Baoji, Shaanxi, People's Republic of China; Department of Medical Techniques, Shaanxi University of Chinese Medicine, Xianyang, 712000, Shannxi, People's Republic of China.
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Preoperative Evaluation of Pancreatic Fibrosis and Lipomatosis: Correlation of Magnetic Resonance Findings With Histology Using Magnetization Transfer Imaging and Multigradient Echo Magnetic Resonance Imaging. Invest Radiol 2019; 53:720-727. [PMID: 30247172 DOI: 10.1097/rli.0000000000000496] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
OBJECTIVES The purpose of this study was to evaluate the diagnostic performance of magnetization transfer (MT) imaging and multigradient echo magnetic resonance imaging (MRI) to quantify pancreatic fibrosis and lipomatosis in patients before pancreatoduodenectomy for postoperative risk stratification with histopathology as the reference standard. MATERIALS AND METHODS Twenty-four patients (age, 68 ± 8 years, 16 males) prospectively underwent quantitative MT imaging using a 2-dimensional gradient echo sequence with and without MT prepulse and multigradient echo imaging on a 3 T MRI 1 day before pancreatoduodenectomy due to adenocarcinoma of the pancreatic head region (n = 20), neuroendocrine tumor (n = 3), or intraductal papillary mucinous neoplasm (n = 1). Magnetization transfer ratio (MTR) and proton density fat fraction (PDFF) were measured in pancreatic tail (PT) and at the resection margin (RM). Histopathologically, pancreatic fibrosis was graded as mild, moderate, or severe (F1-F3), lipomatosis was graded as 0% to 10%, 11% to 30%, and greater than 30% fat deposition (L1-L3). In addition, MTR and histopathologic fibrosis was assessed in pancreatic adenocarcinoma. Mann-Whitney U test and Spearman correlation were used. RESULTS Patients with advanced pancreatic fibrosis (F3) showed a significantly higher MTR compared with the F1 group at the RM and PT (38 ± 4 vs 32.3 ± 1.6, P = 0.018 and 39.7 ± 5.5 vs 31.2 ± 1.7, P = 0.001). Spearman correlation coefficient of MTR and fibrosis grade was r = 0.532 (P = 0.011) and 0.554 (P = 0.008), respectively. Pancreatic parenchyma with advanced fat deposition (L2-L3) showed significantly higher PDFF compared with lipomatosis grade L1 (RM: P = 0.002 and PT: P = 0.001). Proton density fat fraction of pancreatic parenchyma exhibited a moderate and significant correlation with histopathologic lipomatosis grade (RM: r = 0.668 and PT: r = 0.707, P < 0.001). Magnetization transfer ratio was significantly higher in pancreatic adenocarcinoma compared with pancreatic parenchyma (44 ± 5.5 vs 36.0 ± 4.4 and 37.4 ± 5.4, P = 0.004). CONCLUSIONS Multiparametric MRI of the pancreas including MTR and PDFF maps may provide quantitative and noninvasive information on pancreatic fibrosis and lipomatosis before surgery.
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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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Germain P, El Ghannudi S, Labani A, Jeung MY, Gangi A, Ohlmann P, Roy C. A dual flip angle 3D bSSFP magnetization transfer-like method to differentiate between recent and old myocardial infarction. J Magn Reson Imaging 2017; 47:798-808. [PMID: 28727209 DOI: 10.1002/jmri.25821] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/07/2017] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Magnetic resonance imaging (MRI) tissue signal is modulated by magnetization transfer (MT) phenomena, intrinsically induced by balanced steady-state free precession (bSSFP) imaging. PURPOSE To investigate the possible value of such a MT-like bSSFP approach in two clinical settings involving focal myocardial lesions highligthed by late gadolinium enhancement (LGE+): edema induced by recent myocardial infarction (MI) and fibrotic scar related to chronic infarction. MATERIALS AND METHODS Population: 48 LGE + patients were studied: 26 with recent MI, 22 with chronic MI. 20 LGE-normal subjects were considered the control group. Field strength/sequence: Navigator-based short axis 3D-bSSFP sequences with 20° and 90° excitation flip angles were acquired (1.5T). ASSESSMENT Pixel-wise normalized MT Ratio (nMTR) parametric images were calculated according to: nMTR = 100*(S20 -S90 *k)/S20 , with S20 and S90 signal intensity in 20° and 90° flip angle images and k = Blood20 /Blood90 as a normalization ratio. Statistical tests: analysis of variance (ANOVA), receiver operating characteristic (ROC) analysis. RESULTS Overall normal myocardial nMTR was 50.2 ± 3.6%. In recent MI, nMTR values were significantly reduced in LGE + regions (-22.3 ± 9.9%, P < 0.0001). In cases of chronic infarct, nMTR was significantly increased in LGE + regions (14.2 ± 11.4%, P < 0.0001). Comparison between observed results and theoretical values obtained with the Freeman-Hill formula showed that most variations observed in MI are related to MT effects instead of relaxation effects. CONCLUSION In contrast to LGE imaging, which may show a similar hyperenhancement in recent and old infarctions, nMTR imaging demonstrates an opposite pattern: decreased values for recent infarction and increased values for old infarction, thus allowing to discriminate between these two clinical conditions without gadolinium injection. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:798-808.
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Affiliation(s)
- Philippe Germain
- Department of Radiology, University Hospital, Strasbourg, France.,Department of Cardiology, University Hospital, Strasbourg, France
| | - Soraya El Ghannudi
- Department of Radiology, University Hospital, Strasbourg, France.,Department of Nuclear Medicine, University Hospital, Strasbourg, France
| | - Aissam Labani
- Department of Radiology, University Hospital, Strasbourg, France
| | - Mi Y Jeung
- Department of Radiology, University Hospital, Strasbourg, France
| | - Afshin Gangi
- Department of Radiology, University Hospital, Strasbourg, France
| | - Patrick Ohlmann
- Department of Cardiology, University Hospital, Strasbourg, France
| | - Catherine Roy
- Department of Radiology, University Hospital, Strasbourg, France
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Zhang Y, Liang W, Wu G, Zhang X, Wen G. Magnetization transfer imaging reveals geniculocalcarine and striate area degeneration in primary glaucoma: a preliminary study. Acta Radiol Open 2016; 5:2058460116666876. [PMID: 27651931 PMCID: PMC5019197 DOI: 10.1177/2058460116666876] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 08/01/2016] [Indexed: 11/23/2022] Open
Abstract
Background Glaucoma is a neurodegenerative disease that affects both the retina and central visual pathway. Magnetization transfer imaging (MTI) is a sensitive magnetic resonance imaging (MRI) technique that can detect degenerative changes in the brain. Purpose To investigate the geniculocalcarine (GCT) and striate areas in primary glaucoma patients using region of interest (ROI) analysis of magnetization transfer ratio (MTR). Material and Methods Twenty patients with primary glaucoma in both eyes were compared with 31 healthy control patients. All of the participants were examined on a 3.0 T scanner using a three-dimensional T1-weighted spoiled gradient recalled acquisition (SPGR) with and without a MT saturation pulse. A two-sample t-test was used to evaluate the MTR difference between the groups. P < 0.05 was used to determine statistical significance. Results The MTR of the glaucoma group was lower than the healthy controls in both the bilateral GCT (t = 3.781, P = 0.001) and striate areas (t = 4.177, P = 0.000). Conclusion The MTR reductions in the bilateral GCT and striate areas suggest that there is GCT demyelination and striate area degeneration in primary glaucoma. These neurodegenerative effects may be induced as a direct effect of retrograde axonal degeneration along with the indirect effect of anterograde trans-synaptic degeneration.
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Affiliation(s)
- Yan Zhang
- ZhongShan Ophthalmic center, State Key Laboratory of Ophthalmology Sun Yat-sen University, Guangzhou, GuangDong, PR China
| | - Wenwen Liang
- Department of Radiology, Nan Fang Hospital, Southern Medical University, Guangzhou, Guang Dong, PR China
| | - Guijun Wu
- Department of Ophthalmology, Nan Fang Hospital, Southern Medical University, Guangzhou, GuangDong, PR China
| | - Xuelin Zhang
- Department of Radiology, Nan Fang Hospital, Southern Medical University, Guangzhou, Guang Dong, PR China
| | - Ge Wen
- Department of Radiology, Nan Fang Hospital, Southern Medical University, Guangzhou, Guang Dong, PR China
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Magnetization transfer imaging of cortical bone in vivo using a zero echo time sequence in mice at 4.7 T: a feasibility study. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2016; 29:853-862. [PMID: 27384463 DOI: 10.1007/s10334-016-0577-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 06/09/2016] [Accepted: 06/18/2016] [Indexed: 12/29/2022]
Abstract
OBJECTIVE To investigate the feasibility of magnetization transfer (MT) imaging in mice in vivo for the assessment of cortical bone. MATERIALS AND METHODS MT-zero echo time data were acquired at 4.7 T in six mice using MT preparation pulses with two different flip angles (FAs) and a series of ten different off-resonance frequencies (500-15000 Hz). Regions of interest were drawn at multiple levels of the femoral cortical bone. The MT ratio (MTR) was computed for each combination of FAs and off-resonance frequencies. T1 measurements were used to estimate the direct saturation (DS) using a Bloch equation simulation. Estimation of the absorption line width of cortical bone from T2* measurements was also performed. RESULTS MTR values were higher using 3000° FA than 1000° FA. MTR values decreased toward higher off-resonance frequencies. Maximum mean MTR ± standard deviation (SD) of 58.57 ± 5.22 (range 50.44-70.61) was measured with a preparation pulse of 3000° and off-resonance frequency of 500 Hz. Maximum "true" MT effect was estimated at around 2-3 and 5 kHz, respectively, for 1000° and 3000° FA. Mean full width at half maximum ± SD of 577 ± 91 Hz was calculated for the absorption spectral line of the cortical bone. CONCLUSION MT imaging can be used for the assessment of cortical bone in mice in vivo. DS effects are negligible using preparation pulses with off-resonance frequencies greater than 3 kHz.
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Native T1 Mapping by 3-T CMR Imaging for Characterization of Chronic Myocardial Infarctions. JACC Cardiovasc Imaging 2015; 8:1019-1030. [PMID: 26298071 DOI: 10.1016/j.jcmg.2015.04.018] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/26/2015] [Accepted: 04/29/2015] [Indexed: 01/03/2023]
Abstract
OBJECTIVES The purpose of this study was to investigate whether native T1 maps at 3-T can reliably characterize chronic myocardial infarctions (MIs) in patients with prior ST-segment elevation myocardial infarction (STEMI) or non-ST-segment elevation myocardial infarction (NSTEMI). BACKGROUND Late gadolinium enhancement (LGE) cardiac magnetic resonance is the gold standard for characterizing chronic MIs, but it is contraindicated in patients with end-stage chronic kidney disease. METHODS Native T1 and LGE images were acquired at 3-T in patients with prior STEMI (n = 13) and NSTEMI (n = 12) at a median of 13.6 years post-MI. Infarct location, size, and transmurality were measured using mean ± 5 SDs thresholding criterion from LGE images and T1 maps and compared against one another. Independent reviewers assessed visual conspicuity of MIs on LGE images and T1 maps. RESULTS Native T1 maps and LGE images were not different for measuring infarct size (STEMI: p = 0.46; NSTEMI: p = 0.27) and transmurality (STEMI: p = 0.13; NSTEMI: p = 0.21) using thresholding criterion. Using thresholding criterion, good agreement was observed between LGE images and T1 maps for measuring infarct size (STEMI: bias = 0.6 ± 3.1%; R(2) = 0.93; NSTEMI: bias = -0.4 ± 4.4%; R(2) = 0.85) and transmurality (STEMI: bias = 2.0 ± 4.2%; R(2) = 0.89; NSTEMI: bias = -2.7 ± 7.9%; R(2) = 0.68). Sensitivity and specificity of T1 maps for detecting chronic MIs based on thresholding criterion were 89% and 98%, respectively (STEMI), and 87% and 95%, respectively (NSTEMI). Relative to LGE images, the mean visual conspicuity score for detecting chronic MIs was significantly lower for T1 maps (p < 0.001 for both cases). Median infarct-to-remote myocardium contrast-to-noise ratio was 2.5-fold higher for LGE images relative to T1 maps (p < 0.001). Sensitivity and specificity of T1 maps for visual detection were 60% and 86%, respectively (STEMI), and 64% and 91% (NSTEMI), respectively. CONCLUSIONS Chronic MIs in STEMI and NSTEMI patients can be reliably characterized using threshold-based detection on native T1 maps at 3-T. Visual detection of chronic MIs on native T1 maps in both patient populations has high specificity, but modest sensitivity.
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Chang EY, Bae WC, Shao H, Biswas R, Li S, Chen J, Patil S, Healey R, D’Lima DD, Chung CB, Du J. Ultrashort echo time magnetization transfer (UTE-MT) imaging of cortical bone. NMR IN BIOMEDICINE 2015; 28:873-80. [PMID: 25981914 PMCID: PMC4652942 DOI: 10.1002/nbm.3316] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 03/20/2015] [Accepted: 04/06/2015] [Indexed: 05/24/2023]
Abstract
Magnetization transfer (MT) imaging is one way to indirectly assess pools of protons with fast transverse relaxation. However, conventional MT imaging sequences are not applicable to short T2 tissues such as cortical bone. Ultrashort echo time (UTE) sequences with TE values as low as 8 µs can detect signals from different water components in cortical bone. In this study we aim to evaluate two-dimensional UTE-MT imaging of cortical bone and its application in assessing cortical bone porosity as measured by micro-computed tomography (μCT) and biomechanical properties. In total, 38 human cadaveric distal femur and proximal tibia bones were sectioned to produce 122 rectangular pieces of cortical bone for quantitative UTE-MT MR imaging, μCT, and biomechanical testing. Off-resonance saturation ratios (OSRs) with a series of MT pulse frequency offsets (Δf) were calculated and compared with porosity assessed with μCT, as well as elastic (modulus, yield stress, and strain) and failure (ultimate stress, failure strain, and energy) properties, using Pearson correlation and linear regression. A moderately strong negative correlation was observed between OSR and μCT porosity (R(2) = 0.46-0.51), while a moderate positive correlation was observed between OSR and yield stress (R(2) = 0.25-0.30) and failure stress (R(2) = 0.31-0.35), and a weak positive correlation (R(2) = 0.09-0.12) between OSR and Young's modulus at all off-resonance saturation frequencies. OSR determined with the UTE-MT sequence provides quantitative information on cortical bone and is sensitive to μCT porosity and biomechanical function.
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Affiliation(s)
- Eric Y Chang
- Department of Radiology, VA San Diego Healthcare System, La Jolla, CA
- Department of Radiology, University of California, San Diego, CA
| | - Won C Bae
- Department of Radiology, VA San Diego Healthcare System, La Jolla, CA
| | - Hongda Shao
- Department of Radiology, University of California, San Diego, CA
| | - Reni Biswas
- Department of Radiology, University of California, San Diego, CA
| | - Shihong Li
- Department of Radiology, University of California, San Diego, CA
| | - Jun Chen
- Department of Radiology, University of California, San Diego, CA
| | - Shantanu Patil
- Shiley Center for Orthopaedic Research & Education, Scripps Clinic, La Jolla, CA
| | - Robert Healey
- Department of Radiology, University of California, San Diego, CA
| | - Darryl D D’Lima
- Shiley Center for Orthopaedic Research & Education, Scripps Clinic, La Jolla, CA
| | - Christine B Chung
- Department of Radiology, VA San Diego Healthcare System, La Jolla, CA
- Department of Radiology, University of California, San Diego, CA
| | - Jiang Du
- Department of Radiology, University of California, San Diego, CA
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Martens MH, Lambregts DM, Papanikolaou N, Heijnen LA, Riedl RG, zur Hausen A, Maas M, Beets GL, Beets-Tan RG. Magnetization Transfer Ratio. Invest Radiol 2014; 49:29-34. [DOI: 10.1097/rli.0b013e3182a3459b] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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13
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Magnetisation transfer MR imaging of the kidney: evaluation at 3.0 T in association with renal function. Eur Radiol 2013; 23:2315-9. [DOI: 10.1007/s00330-013-2841-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 02/15/2013] [Accepted: 02/25/2013] [Indexed: 10/26/2022]
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14
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Rosenkrantz AB, Storey P, Gilet AG, Niver BE, Babb JS, Hajdu CH, Lee VS. Magnetization Transfer Contrast–prepared MR Imaging of the Liver: Inability to Distinguish Healthy from Cirrhotic Liver. Radiology 2012; 262:136-43. [DOI: 10.1148/radiol.11111043] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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15
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Abstract
The newer magnetic resonance (MR) imaging methods can give insights into the initiation, progression, and eventual treatment of osteoarthritis. Sodium imaging is specific for changes in proteoglycan (PG) content without the need for an exogenous contrast agent. T1ρ imaging is sensitive to early PG depletion. Delayed gadolinium-enhanced MR imaging has high resolution and sensitivity. T2 mapping is straightforward and is sensitive to changes in collagen and water content. Ultrashort echo time MR imaging examines the osteochondral junction. Magnetization transfer provides improved contrast between cartilage and fluid. Diffusion-weighted imaging may be a valuable tool in postoperative imaging.
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16
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Wu Y, Du H, Storey P, Glielmi C, Malone F, Sidharthan S, Ragin A, Tofts PS, Edelman RR. Comprehensive brain analysis with automated high-resolution magnetization transfer measurements. J Magn Reson Imaging 2011; 35:309-17. [PMID: 21990125 DOI: 10.1002/jmri.22835] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 09/14/2011] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To enhance the reliability and spatial resolution of magnetization transfer ratio (MTR) measurements for interrogation of subcortical brain regions with an automated volume of interest (VOI) approach. MATERIALS AND METHODS A 3D magnetization transfer (MT) sequence was acquired using a scan-rescan imaging protocol in nine healthy volunteers. VOI definition masks for the MTR measurements were generated using FreeSurfer and compared to a manual region of interest (ROI) approach. (The longitudinal stability of MTR was monitored using agar gel phantom over a 5-month period.) Intraclass correlation coefficients (ICCs), coefficients of variation (CVs), and instrumental standard deviation (ISD) were determined. RESULTS CVs ranged from 1.29%-2.64% (automated) vs. 1.30%-3.40% (manual). ISDs ranged from 0.62-1.10 pu (automated) vs. 0.68-1.67 pu (manual). The SD of the running difference was 1.70% for the phantom scans. The Bland-Altman method indicated interchangeability of the automated VOI and manual ROI measurements. CONCLUSION The automated VOI approach for MTR measurement yielded higher ICCs, lower CVs, and lower ISDs compared to the manual method, supporting the utility of this strategy. These results demonstrate the feasibility of obtaining reliable MTR measurements in hippocampus and other critical subcortical regions.
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Affiliation(s)
- Ying Wu
- Radiology, NorthShore University HealthSystem, Evanston, Illinois 60201, USA.
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Choi CH, Hutchison JMS, Lurie DJ. Design and construction of an actively frequency-switchable RF coil for field-dependent Magnetisation Transfer Contrast MRI with fast field-cycling. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 207:134-139. [PMID: 20864367 DOI: 10.1016/j.jmr.2010.08.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 08/25/2010] [Accepted: 08/25/2010] [Indexed: 05/29/2023]
Abstract
Magnetisation Transfer Contrast (MTC) is an important MR contrast-generating mechanism to characterise the MR-invisible macromolecular protons using an off-resonance pre-saturation RF irradiation pulse (or MT pulse). MTC MRI is normally implemented at a fixed magnetic field; however, it may be useful to evaluate changes of the MT effect as a function of external magnetic field strength (B₀). In order to conduct field-dependent MTC experiments with a single MR system, two techniques are crucially needed. B₀ should be able to be switched between levels during irradiation of the MT pulse. At the same time, the resonance frequency of the RF coil (f₀) should also be able to be shifted to the corresponding value. Switching B₀ is attained by the fast field-cycling technique, while in order to switch f₀, a specially designed multi-tunable RF coil is required. Here, we designed and constructed an actively frequency-switchable RF coil for frequencies at and below 2.5 MHz. The design employed PIN diodes, and enabled switching f₀ between five different values, with excellent impedance matching (approximately -37 dB S₁₁ reflection) and Q-factor of about 100 at each configuration.
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Affiliation(s)
- Chang-Hoon Choi
- Aberdeen Biomedical Imaging Centre, Biomedical Physics, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
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Helms G, Dathe H, Dechent P. Modeling the influence of TR and excitation flip angle on the magnetization transfer ratio (MTR) in human brain obtained from 3D spoiled gradient echo MRI. Magn Reson Med 2010; 64:177-85. [DOI: 10.1002/mrm.22379] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Double inversion recovery: impact of incidental magnetic transfer effects on optimal inversion times. Invest Radiol 2010; 45:196-201. [PMID: 20177388 DOI: 10.1097/rli.0b013e3181d2ff0e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
OBJECTIVES Doube inversion recovery (DIR) is increasingly used in clinical studies on multiple sclerosis, as it selectively images gray matter and lesions. The inversion times used in literature differ significantly from theoretical predictions. One explanation for this are incidental magnetic transfer (iMT) effects, which are caused by the high density of pulses. In this work, the influence of iMT on DIR was analyzed and compared with theoretical assumptions and inversion times found in literature. MATERIALS AND METHODS Three subjects were measured with 2D DIR sequences. The number of slices measured was varied. Optimum inversion times for white matter (WM) suppression were determined for 1 and for 24 slices by increasing TI2. The impact of slice-to-slice cross talk was evaluated with phantom measurements. RESULTS For constant inversion times TI1 = 3400 ms and TI2 = 325 ms signal intensity of WM decreased with increasing number of slices. The effective longitudinal relaxation time T1sat of WM was with 24 slices (strong iMT effect) 28% lower than at 1 slice (almost no iMT effect). The determined T1sat for 24 slices was 540 ms, compared with 750 ms with 1 slice. CONCLUSIONS Incidental magnetic transfer effects have a huge impact on 2D DIR sequences. The number of slices measured affect strongly the severity of the iMT effect. This can lead to a strong decrease of T1sat for WM depending on the interleaving scheme. Results from different studies and at different field strengths are therefore not easily comparable, without exact knowledge of the sequence design.
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Volz S, Nöth U, Rotarska-Jagiela A, Deichmann R. A fast B1-mapping method for the correction and normalization of magnetization transfer ratio maps at 3 T. Neuroimage 2009; 49:3015-26. [PMID: 19948229 DOI: 10.1016/j.neuroimage.2009.11.054] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 11/02/2009] [Accepted: 11/20/2009] [Indexed: 10/20/2022] Open
Abstract
In neuroimaging, there is increasing interest in magnetization transfer (MT) techniques which yield information about bound water protons. One of the main applications is the investigation of the myelin integrity in the central nervous system (CNS). However, several problems may arise, in particular at high magnetic field strengths: B1 inhomogeneities may yield deviations of the MT saturation angle and thus non-uniformities of the measured MT ratio (MTR). This effect can be corrected for but requires in general additional time consuming B1 mapping. Furthermore, increased values of the specific absorption rate (SAR) may require a reduction of the saturation angle for individual subjects, impairing comparability of results. In this work, a B1 mapping method based on magnetization-prepared FLASH with slice selective preparation and excitation pulses and correction for relaxation effects is presented, yielding B1 maps with whole brain coverage, an in-plane resolution of 4 mm, a slice thickness of 3 mm, and a clinically acceptable duration of 46 s. The method is tested both in vitro and in vivo and applied in a subsequent in vivo study to show that MTR values in human brain tissue depend approximately linearly on the preparation angle, with a slope similar to values reported for 1.5 T. Calibration data and B1 maps are applied to B1 inhomogeneity corrections of MTR maps. Subsequently, it is shown that B1-corrected MTR maps acquired at reduced preparation angles due to individual SAR restrictions can be normalized, allowing for a direct comparison with maps acquired at the full angle.
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Affiliation(s)
- Steffen Volz
- Brain Imaging Center, University Hospital, Schleusenweg 2-16, 60528 Frankfurt, Germany.
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21
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Yao W, Qu N, Lu Z, Yang S. The application of T1 and T2 relaxation time and magnetization transfer ratios to the early diagnosis of patellar cartilage osteoarthritis. Skeletal Radiol 2009; 38:1055-62. [PMID: 19688346 DOI: 10.1007/s00256-009-0769-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 07/09/2009] [Accepted: 07/17/2009] [Indexed: 02/02/2023]
Abstract
OBJECTIVES We compare the T1 and T2 relaxation times and magnetization transfer ratios (MTRs) of normal subjects and patients with osteoarthritis (OA) to evaluate the ability of these techniques to aid in the early diagnosis and treatment of OA. MATERIALS AND METHODS The knee joints in 11 normal volunteers and 40 patients with OA were prospectively evaluated using T1 relaxation times as measured using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 relaxation times (multiple spin-echo sequence, T2 mapping), and MTRs. The OA patients were further categorized into mild, moderate, and severe OA. RESULTS The mean T1 relaxation times of the four groups (normal, mild OA, moderate OA, and severe OA) were: 487.3 +/- 27.7, 458.0 +/- 55.9, 405.9 +/- 57.3, and 357.9 +/- 36.7 respectively (p <0.001). The mean T2 relaxation times of the four groups were: 37.8 +/- 3.3, 44.0 +/- 8.5, 50.9 +/- 9.5, and 57.4 +/- 4.8 respectively (p < 0.001). T1 relaxation time decreased and T2 relaxation time increased with worsening degeneration of patellar cartilage. The result of the covariance analysis showed that the covariate age had a significant influence on T2 relaxation time (p < 0.001). No significant differences between the normal and OA groups using MTR were noted. CONCLUSION T1 and T2 relaxation times are relatively sensitive to early degenerative changes in the patellar cartilage, whereas the MTR may have some limitations with regard to early detection of OA. In addition, The T1 and T2 relaxation times negatively correlate with each other, which is a novel finding.
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Affiliation(s)
- Weiwu Yao
- Department of Radiology, Shanghai No.6 People's Hospital affiliated to Shanghai Jiaotong University, Shanghai, China.
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Shin W, Gu H, Yang Y. Incidental magnetization transfer contrast by fat saturation preparation pulses in multislice Look-Locker echo planar imaging. Magn Reson Med 2009; 62:520-6. [PMID: 19526506 DOI: 10.1002/mrm.22034] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, it is demonstrated that fat saturation (FS) preparation (prep) pulses generate incidental magnetization transfer contrast (MTC) in multislice Look-Locker (LL) imaging. It is shown that frequency-selective FS prep pulses can invoke MTC through the exchange between free and motion-restricted protons. Simulation reveals that the fractional signal loss by these MTC effects is more severe for smaller flip angles (FAs), shorter repetition times (TRs), and greater number of slices (SN). These incidental MTC effects result in a signal attenuation at a steady state (up to 30%) and a T(1) measurement bias (up to 20%) when using inversion recovery (IR) LL echo-planar imaging (EPI) sequences. Furthermore, it is shown that water-selective MRI using binomial pulses has the potential to minimize the signal attenuation and provide unbiased T(1) measurement without fat artifacts in MR images.
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Affiliation(s)
- Wanyong Shin
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA.
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Morphologic and Dynamic Renal Imaging With Assessment of Glomerular Filtration Rate in a pcy-Mouse Model Using a Clinical 3.0 Tesla Scanner. Invest Radiol 2009; 44:469-75. [DOI: 10.1097/rli.0b013e3181a8afa1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Underhill HR, Yuan C, Yarnykh VL. Direct quantitative comparison between cross-relaxation imaging and diffusion tensor imaging of the human brain at 3.0 T. Neuroimage 2009; 47:1568-78. [PMID: 19500678 DOI: 10.1016/j.neuroimage.2009.05.075] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 05/12/2009] [Accepted: 05/26/2009] [Indexed: 10/20/2022] Open
Abstract
Cross-relaxation imaging (CRI) describes the magnetization transfer within tissues between mobile water protons and macromolecular protons. Whole-brain parametric maps of the principle kinetic components of magnetization transfer, the fraction of macromolecular protons (f) and the rate constant (k), revealed detailed anatomy of white matter (WM) fiber tracts at 1.5 T. In this study, CRI was first adapted to 3.0 T, and constraints for transverse relaxation times of water and macromolecular protons were identified to enable unbiased f and k estimation. Subsequently, whole-brain CRI and diffusion tensor imaging (DTI) were performed in five healthy subjects. The parameters f and k were compared to DTI indices (fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity (RD), and axial diffusivity (AD)) across a range of anatomic regions. In WM, neither f nor k was significantly correlated to FA, RD, and AD. In contrast, both f (r=0.90 and r=-0.80) and k (r=0.92 and r=-0.89) in gray matter (GM) were strongly correlated to FA and RD, respectively. A moderate correlation between ADC and k (r=0.48) was identified in WM, while an inverse correlation was identified in GM (r=-0.72). The lack of association between CRI and FA in WM is consistent with differences in the underlying physical principles between techniques - fiber density vs. directionality, respectively. The association in GM may be attributable to variable axonal density unique to each structure. Our findings suggest that whole-brain CRI provides distinct quantitative information compared to DTI, and CRI parameters may prove constructive as biomarkers in neurological diseases.
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Affiliation(s)
- Hunter R Underhill
- Department of Radiology, University of Washington, Seattle, WA 98109, USA.
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Springer F, Martirosian P, Machann J, Schwenzer NF, Claussen CD, Schick F. Magnetization transfer contrast imaging in bovine and human cortical bone applying an ultrashort echo time sequence at 3 Tesla. Magn Reson Med 2009; 61:1040-8. [PMID: 19267348 DOI: 10.1002/mrm.21866] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Fabian Springer
- Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen, Germany.
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Abstract
Current advances in magnetic resonance, as a diagnostic modality, are discussed in the context of publications from Investigative Radiology during 2007 and 2008. The articles relating to this topic, published during the past 2 years, are reviewed by anatomic region. The discussion concludes with a consideration of magnetic resonance contrast media, focusing on studies published in the journal, and examining in particular the potential impact of nephrogenic systemic fibrosis.
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