共查询到20条相似文献,搜索用时 15 毫秒
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Gannet: A batch‐processing tool for the quantitative analysis of gamma‐aminobutyric acid–edited MR spectroscopy spectra 下载免费PDF全文
Richard A.E. Edden PhD Nicolaas A.J. Puts PhD Ashley D. Harris PhD Peter B. Barker DPhil C. John Evans PhD 《Journal of magnetic resonance imaging : JMRI》2014,40(6):1445-1452
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Karaus A Merboldt KD Graessner J Frahm J 《Journal of magnetic resonance imaging : JMRI》2007,26(6):1666-1671
PURPOSE: To develop a rapid stimulated echo acquisition mode (STEAM) MRI technique for "black-blood" imaging of the human heart that overcomes the single-slice limitation and partially compromised blood suppression associated with double inversion-recovery techniques. MATERIALS AND METHODS: Black-blood multislice images of the heart along anatomic orientations and triggered to end diastole were obtained from healthy human subjects at 3T using rapid STEAM MRI sequences with five-eighths partial Fourier encoding and variable flip angles. Single-shot STEAM images at 2.5 x 2.5 mm2 in-plane resolution and 6-mm section thickness were recorded in 230 msec from individual heartbeats. Improved signal-to-noise ratio (SNR) and higher spatial resolution of 2.0 x 2.0 mm2 and 1.5 x 1.5 mm2 were achieved by segmented multishot STEAM MRI with interleaved k-space acquisitions (160 msec each) from several heartbeats. In a single breathhold covering 18 heartbeats selected applications employed either three segments with six sections or six segments with three sections. RESULTS: Because stimulated echoes (STEs) dephase signals from moving spins, rapid STEAM images are free from blood signal contamination. The method offers a flexible tradeoff between spatial resolution, imaging speed (i.e., number of segments), and volume coverage (i.e., number of sections). CONCLUSION: Rapid STEAM MRI of the heart emerges as a simple technique for multislice imaging of the myocardial wall with efficient flow suppression. 相似文献
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N. Kunz C. Cudalbu V. Mlynarik P. S. Hüppi S. V. Sizonenko R. Gruetter 《Magnetic resonance in medicine》2010,64(4):939-946
Quantification of short‐echo time proton magnetic resonance spectroscopy results in >18 metabolite concentrations (neurochemical profile). Their quantification accuracy depends on the assessment of the contribution of macromolecule (MM) resonances, previously experimentally achieved by exploiting the several fold difference in T1. To minimize effects of heterogeneities in metabolites T1, the aim of the study was to assess MM signal contributions by combining inversion recovery (IR) and diffusion‐weighted proton spectroscopy at high‐magnetic field (14.1 T) and short echo time (=8 msec) in the rat brain. IR combined with diffusion weighting experiments (with δ/Δ = 1.5/200 msec and b‐value = 11.8 msec/μm2) showed that the metabolite nulled spectrum (inversion time = 740 msec) was affected by residuals attributed to creatine, inositol, taurine, choline, N‐acetylaspartate as well as glutamine and glutamate. While the metabolite residuals were significantly attenuated by 50%, the MM signals were almost not affected (<8%). The combination of metabolite‐nulled IR spectra with diffusion weighting allows a specific characterization of MM resonances with minimal metabolite signal contributions and is expected to lead to a more precise quantification of the neurochemical profile. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
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Osteoporosis is associated with increased marrow fat content and decreased marrow fat unsaturation: a proton MR spectroscopy study 总被引:6,自引:0,他引:6
Yeung DK Griffith JF Antonio GE Lee FK Woo J Leung PC 《Journal of magnetic resonance imaging : JMRI》2005,22(2):279-285
PURPOSE: To use proton magnetic resonance spectroscopy ((1)H-MRS) to evaluate vertebral marrow fat, and to determine whether bone density correlates with fat content and fat unsaturation levels in postmenopausal women. MATERIALS AND METHODS: Fifty-three women (mean age = 70 years) underwent dual energy x-ray absorptiometry and (1)H-MRS, and 12 young female controls (mean age = 28 years) underwent (1)H-MRS of the lumber spine. Water and lipid peak amplitudes were measured to calculate fat content and fat unsaturation index. Spearman's correlation tests and a t-test comparison of means were applied. RESULTS: (1)H-MRS was successful in 15 normal, 15 osteopenic, and 20 osteoporotic subjects, and in all controls. Marrow fat content was significantly elevated in osteoporotic (65.5% +/- 10%) and osteopenic (63.5% +/- 9.3%) subjects compared to normal subjects (56.3% +/- 11.2%) and young controls (29% +/- 9.6%). The fat unsaturation index was significantly decreased in osteoporotic (0.091 +/- 0.013) and osteopenic (0.097 +/- 0.014) subjects compared to normal subjects (0.114 +/- 0.016) and young controls (0.127 +/- 0.031). A good inverse correlation was observed between the fat content and the unsaturation index (r(s) = -0.53, P < 0.0001). CONCLUSION: Osteoporosis is associated with increased marrow fat. As marrow fat increases, saturated lipids appear to increase preferentially to unsaturated lipids. 相似文献
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Geraldine H. Kang BS Irene Cruite MD Masoud Shiehmorteza MD Tanya Wolfson MA Anthony C. Gamst PhD Gavin Hamilton PhD Mark Bydder PhD Michael S. Middleton MD PhD Claude B. Sirlin MD 《Journal of magnetic resonance imaging : JMRI》2011,34(4):928-934
Purpose:
To evaluate magnetic resonance imaging (MRI)‐determined proton density fat fraction (PDFF) reproducibility across two MR scanner platforms and, using MR spectroscopy (MRS)‐determined PDFF as reference standard, to confirm MRI‐determined PDFF estimation accuracy.Materials and Methods:
This prospective, cross‐sectional, crossover, observational pilot study was approved by an Institutional Review Board. Twenty‐one subjects gave written informed consent and underwent liver MRI and MRS at both 1.5T (Siemens Symphony scanner) and 3T (GE Signa Excite HD scanner). MRI‐determined PDFF was estimated using an axial 2D spoiled gradient‐recalled echo sequence with low flip‐angle to minimize T1 bias and six echo‐times to permit correction of T2* and fat‐water signal interference effects. MRS‐determined PDFF was estimated using a stimulated‐echo acquisition mode sequence with long repetition time to minimize T1 bias and five echo times to permit T2 correction. Interscanner reproducibility of MRI determined PDFF was assessed by correlation analysis; accuracy was assessed separately at each field strength by linear regression analysis using MRS‐determined PDFF as reference standard.Results:
1.5T and 3T MRI‐determined PDFF estimates were highly correlated (r = 0.992). MRI‐determined PDFF estimates were accurate at both 1.5T (regression slope/intercept = 0.958/‐0.48) and 3T (slope/intercept = 1.020/0.925) against the MRS‐determined PDFF reference.Conclusion:
MRI‐determined PDFF estimation is reproducible and, using MRS‐determined PDFF as reference standard, accurate across two MR scanner platforms at 1.5T and 3T. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc. 相似文献7.
High‐resolution, diffusion‐weighted (DW) MR microscopy is gaining increasing acceptance as a nondestructive histological tool for the study of fixed tissue samples. Spin‐echo sequences are popular for high‐field diffusion imaging due to their high tolerance to B0 field inhomogeneities. Volumetric DW rapid acquisition with relaxation enhancement (DW‐RARE) currently offers the best tradeoff between imaging efficiency and image quality, but is relatively sensitive to residual eddy‐current effects on the echo train phase, resulting in encoding direction‐dependent ghosting in the DW images. We introduce two efficient, image‐based phase corrections for ghost artifact reduction in DW‐RARE of fixed tissue samples, neither of which require navigator echo acquisition. Both methods rely on the phase difference in k‐space between the unweighted reference image and a given DW image and assume a constant, per‐echo phase error arising from residual eddy‐current effects in the absence of sample motion. Significant qualitative and quantitative ghost artifact reductions are demonstrated for individual DW and calculated diffusion tensor images. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
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Masayuki Yamaguchi Fumiyuki Mitsumori Hidehiro Watanabe Nobuhiro Takaya Manabu Minami 《Magnetic resonance in medicine》2006,55(4):749-754
A noninvasive NMR technique for evaluating testicular function was explored in this study. Localized in vivo 1H NMR spectroscopy was performed on rat testes using a stimulated echo acquisition mode (STEAM) sequence with a short echo time (TE). In the 1H spectra, large lipid signals dominated the chemical shift range of 0.89-2.78 ppm, which prevented the observation of metabolite signals in this region. To suppress these lipid signals, short inversion time (TI) inversion recovery (STIR) was combined with STEAM (STIR-STEAM). The optimal TI was typically 320 ms. STIR-STEAM with a TE of 15 ms allowed successful suppression of the lipid signals and the sensitive detection of several new metabolite signals. In normal testes, choline, creatine, glutamate, and glycine signals were identified. In addition to these metabolites, a lactate signal was observed in ischemic testes. To our knowledge, the signals of glutamate, glycine, and lactate have not been previously assigned in 1H MR spectra of testes in vivo. Lipid suppression by STIR aided in the detection of these metabolites, which would otherwise have been masked by the lipid signals. 相似文献
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Ananth J. Madhuranthakam PhD Huanzhou Yu PhD Ann Shimakawa MS Reed F. Busse PhD Martin P. Smith MD Scott B. Reeder MD PhD Neil M. Rofsky MD Jean H. Brittain PhD Charles A. McKenzie PhD 《Journal of magnetic resonance imaging : JMRI》2010,32(3):745-751
Purpose:
To develop a robust 3D fast spin echo (FSE) T2‐weighted imaging method with uniform water and fat separation in a single acquisition, amenable to high‐quality multiplanar reformations.Materials and Methods:
The Iterative Decomposition of water and fat with Echo Asymmetry and Least squares estimation (IDEAL) method was integrated with modulated refocusing flip angle 3D‐FSE. Echoes required for IDEAL processing were acquired by shifting the readout gradient with respect to the Carr‐Purcell‐Meiboom‐Gill echo. To reduce the scan time, an alternative data acquisition using two gradient echoes per repetition was implemented. Using the latter approach, a total of four gradient echoes were acquired in two repetitions and used in the modified IDEAL reconstruction.Results:
3D‐FSE T2‐weighted images with uniform water–fat separation were successfully acquired in various anatomies including breast, abdomen, knee, and ankle in clinically feasible scan times, ranging from 5:30–8:30 minutes. Using water‐only and fat‐only images, in‐phase and out‐of‐phase images were reconstructed.Conclusion:
3D‐FSE‐IDEAL provides volumetric T2‐weighted images with uniform water and fat separation in a single acquisition. High‐resolution images with multiple contrasts can be reformatted to any orientation from a single acquisition. This could potentially replace 2D‐FSE acquisitions with and without fat suppression and in multiple planes, thus improving overall imaging efficiency. J. Magn. Reson. Imaging 2010;32:745–751. © 2010 Wiley‐Liss, Inc. 相似文献11.
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Diffusion‐weighted imaging in assessing pathological response of tumor in breast cancer subtype to neoadjuvant chemotherapy 下载免费PDF全文
Shangang Liu MD Ruimei Ren PhD Zhaoqiu Chen MD Yongsheng Wang PhD Tingyong Fan MD Chengli Li PhD Pinliang Zhang MD 《Journal of magnetic resonance imaging : JMRI》2015,42(3):779-787
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MRI‐determined liver proton density fat fraction,with MRS validation: Comparison of regions of interest sampling methods in patients with type 2 diabetes 下载免费PDF全文
Kim‐Nhien Vu MD Guillaume Gilbert PhD Marianne Chalut Miguel Chagnon MS Gabriel Chartrand BS An Tang MD MS 《Journal of magnetic resonance imaging : JMRI》2016,43(5):1090-1099
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Developing and validating a multivariable prediction model to improve the diagnostic accuracy in determination of cervical versus endometrial origin of uterine adenocarcinomas: A prospective MR study combining diffusion‐weighted imaging and spectroscopy 下载免费PDF全文
Gigin Lin MD PhD Yu‐Chun Lin PhD Ren‐Chin Wu MD PhD Lan‐Yan Yang PhD Hsin‐Ying Lu MSc Shang‐Yueh Tsai PhD Yu‐Ting Huang MD Yen‐Ling Huang MD Kuan‐Ying Lu MSc Koon‐Kwan Ng MD Tzu‐Chen Yen MD PhD Angel Chao MD PhD Chyong‐Huey Lai MD Ji‐Hong Hong MD PhD 《Journal of magnetic resonance imaging : JMRI》2018,47(6):1654-1666
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Yoshito Tsushima MD Ayako Takahashi‐Taketomi MD Keigo Endo MD 《Journal of magnetic resonance imaging : JMRI》2009,30(2):249-255
To review the published reports concerning the apparent diffusion coefficient (ADC) value evaluation for the differentiation between malignant and benign breast tumors, articles were searched with the inclusion criteria: (a) a 1.5‐T unit was used; (b) the diagnostic criteria were clearly stated; (c) diffusion‐weighted images (DWIs) were obtained, and ADC value was calculated; (d) ADC values of breast tumors were reported with mean ± standard deviation (SD). Meta‐analysis from 12 articles revealed that the pooled sensitivity and specificity were 0.89 (95% confidence interval [CI], 0.85–0.91) and 0.77 (95% CI, 0.69–0.84), respectively, and that only the maximum b factor correlated with the mean ADC values of malignant and benign tumors, and the noncancerous breast tissue (P< 0.05,P < 0.01,P< 0.05, respectively). In conclusion, ADC evaluation is useful for the differentiation between malignant and benign breast tumors. J. Magn. Reson. Imaging 2009;30:249–255. © 2009 Wiley‐Liss, Inc. 相似文献
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MRI‐based staging of hepatic fibrosis: Comparison of intravoxel incoherent motion diffusion‐weighted imaging with magnetic resonance elastography 下载免费PDF全文
Shintaro Ichikawa MD Utaroh Motosugi MD PhD Hiroyuki Morisaka MD Katsuhiro Sano MD PhD Tomoaki Ichikawa MD PhD Nobuyuki Enomoto MD PhD Masanori Matsuda MD PhD Hideki Fujii MD PhD Hiroshi Onishi MD PhD 《Journal of magnetic resonance imaging : JMRI》2015,42(1):204-210
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Characterization of malignant breast tissue of breast cancer patients and the normal breast tissue of healthy lactating women volunteers using diffusion MRI and in vivo 1H MR spectroscopy 下载免费PDF全文
Rani G. Sah PhD Khushbu Agarwal MSc Uma Sharma PhD Rajinder Parshad MS Vurthaluru Seenu MS Naranamangalam R. Jagannathan PhD 《Journal of magnetic resonance imaging : JMRI》2015,41(1):169-174