共查询到20条相似文献,搜索用时 15 毫秒
1.
Brian J. Soher William E. Wu Assaf Tal Pippa Storey Ke Zhang James S. Babb Ivan I. Kirov Yvonne W. Lui Oded Gonen 《NMR in biomedicine》2014,27(11):1275-1284
Concentration of the neuronal marker, N‐acetylaspartate (NAA), a quantitative metric for the health and density of neurons, is currently obtained by integration of the manually defined peak in whole‐head proton (1H)‐MRS. Our goal was to develop a full spectral modeling approach for the automatic estimation of the whole‐brain NAA concentration (WBNAA) and to compare the performance of this approach with a manual frequency‐range peak integration approach previously employed. MRI and whole‐head 1H‐MRS from 18 healthy young adults were examined. Non‐localized, whole‐head 1H‐MRS obtained at 3 T yielded the NAA peak area through both manually defined frequency‐range integration and the new, full spectral simulation. The NAA peak area was converted into an absolute amount with phantom replacement and normalized for brain volume (segmented from T1‐weighted MRI) to yield WBNAA. A paired‐sample t test was used to compare the means of the WBNAA paradigms and a likelihood ratio test used to compare their coefficients of variation. While the between‐subject WBNAA means were nearly identical (12.8 ± 2.5 mm for integration, 12.8 ± 1.4 mm for spectral modeling), the latter's standard deviation was significantly smaller (by ~50%, p = 0.026). The within‐subject variability was 11.7% (±1.3 mm ) for integration versus 7.0% (±0.8 mm ) for spectral modeling, i.e., a 40% improvement. The (quantifiable) quality of the modeling approach was high, as reflected by Cramer–Rao lower bounds below 0.1% and vanishingly small (experimental ‐ fitted) residuals. Modeling of the whole‐head 1H‐MRS increases WBNAA quantification reliability by reducing its variability, its susceptibility to operator bias and baseline roll, and by providing quality‐control feedback. Together, these enhance the usefulness of the technique for monitoring the diffuse progression and treatment response of neurological disorders. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
Comparison of reproducibility of single voxel spectroscopy and whole‐brain magnetic resonance spectroscopy imaging at 3T
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yue Zhang Edward Taub Nouha Salibi Gitendra Uswatte Andrew A. Maudsley Sulaiman Sheriff Brent Womble Victor W. Mark David C. Knight 《NMR in biomedicine》2018,31(4)
To date, single voxel spectroscopy (SVS) is the most commonly used MRS technique. SVS is relatively easy to use and provides automated and immediate access to the resulting spectra. However, it is also limited in spatial coverage. A new and very promising MRS technique allows for whole‐brain MR spectroscopic imaging (WB‐MRSI) with much improved spatial resolution. Establishing the reproducibility of data obtained using SVS and WB‐MRSI is an important first step for using these techniques to evaluate longitudinal changes in metabolite concentration. The purpose of this study was to assess and directly compare the reproducibility of metabolite quantification at 3T using SVS and WB‐MRSI in ‘hand‐knob’ areas of motor cortices and hippocampi in healthy volunteers. Ten healthy adults were scanned using both SVS and WB‐MRSI on three occasions one week apart. N‐acetyl aspartate (NAA), creatine (Cr), choline (Cho) and myo‐inositol (mI) were quantified using SVS and WB‐MRSI with reference to both Cr and H2O. The reproducibility of each technique was evaluated using the coefficient of variation (CV), and the correspondence between the two techniques was assessed using Pearson correlation analysis. The measured mean (range) intra‐subject CVs for SVS were 5.90 (2.65‐10.66)% for metabolites (i.e. NAA, Cho, mI) relative to Cr, and 8.46 (4.21‐21.07)% for metabolites (NAA, Cr, Cho, mI) relative to H2O. The mean (range) CVs for WB‐MRSI were 7.56 (2.78‐11.41)% for metabolites relative to Cr, and 7.79 (4.57‐14.11)% for metabolites relative to H2O. Significant positive correlations were observed between metabolites quantified using SVS and WB‐MRSI techniques when the Cr but not H2O reference was used. The results demonstrate that reproducibilities of SVS and WB‐MRSI are similar for quantifying the four major metabolites (NAA, Cr, Cho, mI); both SVS and WB‐MRSI exhibited good reproducibility. Our findings add reference information for choosing the appropriate 1H‐MRS technique in future studies. 相似文献
3.
4.
Yue Zhang Edward Taub Christina Mueller Jarred Younger Gitendra Uswatte Thomas Patrick DeRamus David C. Knight 《NMR in biomedicine》2020,33(7)
Assessing brain temperature can provide important information about disease processes (e.g., stroke, trauma) and therapeutic effects (e.g., cerebral hypothermia treatment). Whole‐brain magnetic resonance spectroscopic imaging (WB‐MRSI) is increasingly used to quantify brain metabolites across the entire brain. However, its feasibility and reliability for estimating brain temperature needs further validation. Therefore, the present study evaluates the reproducibility of WB‐MRSI for temperature mapping as well as metabolite quantification across the whole brain in healthy volunteers. Ten healthy adults were scanned on three occasions 1 week apart. Brain temperature, along with four commonly assessed brain metabolites—total N‐acetyl‐aspartate (tNAA), total creatine (tCr), total choline (tCho) and myo‐inositol (mI)—were measured from WB‐MRSI data. Reproducibility was evaluated using the coefficient of variation (CV). The measured mean (range) of the intra‐subject CVs was 0.9% (0.6%‐1.6%) for brain temperature mapping, and 4.7% (2.5%‐15.7%), 6.4% (2.4%‐18.9%) and 14.2% (4.4%‐52.6%) for tNAA, tCho and mI, respectively, with reference to tCr. Consistently larger variability was found when using H2O as the reference for metabolite quantifications: 7.8% (3.3%‐17.8%), 7.8% (3.1%‐18.0%), 9.8% (3.7%‐31.0%) and 17.0% (5.9%‐54.0%) for tNAA, tCr, tCho and mI, respectively. Further, the larger the brain region (indicated by a greater number of voxels within that region), the better the reproducibility for both temperature and metabolite estimates. Our results demonstrate good reproducibility of whole‐brain temperature and metabolite measurements using the WB‐MRSI technique. 相似文献
5.
Relaxation times of choline, creatine and N-acetyl aspartate in human cerebral white matter at 1.5 T
Several studies have investigated the T1 and T2 relaxation time of choline, creatine and N-acetyl aspartate in cerebral white matter in normal human subjects. However, these studies demonstrate a large variation in T1 and T2 values. In the present study, relaxation times of choline, creatine and N-acetyl aspartate were determined in cerebral white matter in 15 control subjects (age 21 +/- 2 y, mean +/- SD) at 1.5 T. Using PRESS, seven or eight data points were obtained to fit the T1 and T2 relaxation curves to, respectively. The mean voxel size was 14 cm3. The T1 relaxation times of choline, creatine and N-acetyl aspartate were 1091 +/- 132 (mean +/- SD), 1363 +/- 137 and 1276 +/- 132 ms. The T2 relaxation times were 352 +/- 52, 219 +/- 29 and 336 +/- 46 ms, respectively. 相似文献
6.
William E. Wu Assaf Tal Ivan I. Kirov Henry Rusinek Daniel Charytonowicz James S. Babb Eva‐Maria Ratai R. Gilberto Gonzalez Oded Gonen 《NMR in biomedicine》2013,26(4):480-488
To test the hypotheses that global decreased neuro‐axonal integrity reflected by decreased N‐acetylaspartate (NAA) and increased glial activation reflected by an elevation in its marker, the myo‐inositol (mI), present in a CD8‐depleted rhesus macaque model of HIV‐associated neurocognitive disorders. To this end, we performed quantitative MRI and 16 × 16 × 4 multivoxel proton MRS imaging (TE/TR = 33/1400 ms) in five macaques pre‐ and 4–6 weeks post‐simian immunodeficiency virus infection. Absolute NAA, creatine, choline (Cho), and mI concentrations, gray and white matter (GM and WM) and cerebrospinal fluid fractions were obtained. Global GM and WM concentrations were estimated from 224 voxels (at 0.125 cm3 spatial resolution over ~35% of the brain) using linear regression. Pre‐ to post‐infection global WM NAA declined 8%: 6.6 ± 0.4 to 6.0 ± 0.5 mM (p = 0.05); GM Cho declined 20%: 1.3 ± 0.2 to 1.0 ± 0.1 mM (p < 0.003); global mI increased 11%: 5.7 ± 0.4 to 6.5 ± 0.5 mM (p < 0.03). Global GM and WM brain volume fraction changes were statistically insignificant. These metabolic changes are consistent with global WM (axonal) injury and glial activation, and suggest a possible GM host immune response. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Spatial variability and reproducibility of GABA‐edited MEGA‐LASER 3D‐MRSI in the brain at 3 T
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Petra Hnilicová Michal Považan Bernhard Strasser Ovidiu C. Andronesi Martin Gajdošík Ulrike Dydak Jozef Ukropec Dušan Dobrota Siegfried Trattnig Wolfgang Bogner 《NMR in biomedicine》2016,29(11):1656-1665
The reproducibility of gamma‐aminobutyric acid (GABA) quantification results, obtained with MRSI, was determined on a 3 T MR scanner in healthy adults. In this study, a spiral‐encoded, GABA‐edited, MEGA‐LASER MRSI sequence with real‐time motion–scanner‐instability corrections was applied for robust 3D mapping of neurotransmitters in the brain. In particular, the GABA+ (i.e. GABA plus macromolecule contamination) and Glx (i.e. glutamate plus glutamine contamination) signal was measured. This sequence enables 3D‐MRSI with about 3 cm3 nominal resolution in about 20 min. Since reliable quantification of GABA is challenging, the spatial distribution of the inter‐subject and intra‐subject variability of GABA+ and Glx levels was studied via test–retest assessment in 14 healthy volunteers (seven men–seven women). For both inter‐subject and intra‐subject repeated measurement sessions a low coefficient of variation (CV) and a high intraclass correlation coefficient (ICC) were found for GABA+ and Glx ratios across all evaluated voxels (intra?/inter‐subject: GABA+ ratios, CV ~ 8%–ICC > 0.75; Glx ratios, CV ~ 6%–ICC > 0.70). The same was found in selected brain regions for Glx ratios versus GABA+ ratios (CV varied from about 5% versus about 8% in occipital and parietal regions, to about 8% versus about 10% in the frontal area, thalamus, and basal ganglia). These results provide evidence that 3D mapping of GABA+ and Glx using the described methodology provides high reproducibility for application in clinical and neuroscientific studies. 相似文献
8.
Neurochemical evaluation of brain function with 1H magnetic resonance spectroscopy in patients with fragile X syndrome
下载免费PDF全文
![点击此处可从《American journal of medical genetics. Part A》网站下载免费的PDF全文](/ch/ext_images/free.gif)
G.E. Utine B. Akpınar U. Arslan P.Ö.Ş. Kiper B. Volkan‐Salancı Y. Alanay D. Aktaş G. Haliloğlu K.K. Oğuz K. Boduroğlu M. Alikaşifoğlu 《American journal of medical genetics. Part A》2014,164(1):99-105
9.
Shizhe Li Yan Zhang Shumin Wang Maria Ferraris Araneta Christopher S. Johnson Yun Xiang Robert B. Innis Jun Shen 《NMR in biomedicine》2010,23(8):977-985
Previously, we devised a novel strategy for in vivo 13C MRS using [2‐13C]glucose infusion and low‐power proton decoupling, and proposed that this strategy could be used to acquire 13C MR spectra from the frontal lobe of the human brain. Here, we demonstrate, for the first time, in vivo 13C MRS of human frontal lobe acquired at 3 T. Because the primary metabolites of [2‐13C]glucose can be decoupled using very‐low‐radiofrequency power, we used a volume coil for proton decoupling in this study. The homogeneous B1 field of the volume coil was found to significantly enhance the decoupling efficiency of the stochastic decoupling sequence. Detailed specific absorption rates inside the human head were analyzed using the finite difference time domain method to ensure experimental safety. In vivo 13C spectra from the occipital and frontal lobes of the human brain were obtained. At a decoupling power of 30 W (time‐averaged power, 2.45 W), the spectra from the occipital lobe showed well‐resolved spectral resolution and excellent signal‐to‐noise ratio. Although frontal lobe 13C spectra were affected by local B0 field inhomogeneity, we demonstrated that the spectral quality could be improved using post‐acquisition data processing. In particular, we showed that the frontal lobe glutamine C5 at 178.5 ppm and aspartate C4 at 178.3 ppm could be spectrally resolved with effective proton decoupling and B0 field correction. Because of its large spatial coverage, volume coil decoupling provides the potential to acquire 13C MRS from more than one brain region simultaneously. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
Measurement of glycine in healthy and tumorous brain by triple‐refocusing MRS at 3 T in vivo
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vivek Tiwari Zhongxu An Sandeep K. Ganji Jeannie Baxter Toral R. Patel Edward Pan Bruce E. Mickey Elizabeth A. Maher Marco C. Pinho Changho Choi 《NMR in biomedicine》2017,30(9)
Glycine (Gly) has been implicated in several neurological disorders, including malignant brain tumors. The precise measurement of Gly is challenging largely as a result of the spectral overlap with myo‐inositol (mI). We report a new triple‐refocusing sequence for the reliable co‐detection of Gly and mI at 3 T and for the evaluation of Gly in healthy and tumorous brain. The sequence parameters were optimized with density‐matrix simulations and phantom validation. With a total TE of 134 ms, the sequence gave complete suppression of the mI signal between 3.5 and 3.6 ppm and, consequently, well‐defined Gly (3.55 ppm) and mI (3.64 ppm) peaks. In vivo 1H magnetic resonance spectroscopy (MRS) data were acquired from the gray matter (GM)‐dominant medial occipital and white matter (WM)‐dominant left parietal regions in six healthy subjects, and analyzed with LCModel using in‐house‐calculated basis spectra. Tissue segmentation was performed to obtain the GM and WM contents within the MRS voxels. Metabolites were quantified with reference to GM‐rich medial occipital total creatine at 8 mM. The Gly and mI concentrations were estimated to be 0.63 ± 0.05 and 8.6 ± 0.6 mM for the medial occipital and 0.34 ± 0.05 and 5.3 ± 0.8 mM for the left parietal regions, respectively. From linear regression of the metabolite estimates versus fractional GM content, the concentration ratios between pure GM and pure WM were estimated to be 2.6 and 2.1 for Gly and mI, respectively. Clinical application of the optimized sequence was performed in four subjects with brain tumor. The Gly levels in tumors were higher than those of healthy brain. Gly elevation was more extensive in a post‐contrast enhancing region than in a non‐enhancing region. The data indicate that the optimized triple‐refocusing sequence may provide reliable co‐detection of Gly and mI, and alterations of Gly in brain tumors can be precisely evaluated. 相似文献
11.
MRS thermometry calibration at 3 T: effects of protein,ionic concentration and magnetic field strength
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ben Babourina‐Brooks Robert Simpson Theodoros N. Arvanitis Graham Machin Andrew C. Peet Nigel P. Davies 《NMR in biomedicine》2015,28(7):792-800
MRS thermometry has been utilized to measure temperature changes in the brain, which may aid in the diagnosis of brain trauma and tumours. However, the temperature calibration of the technique has been shown to be sensitive to non‐temperature‐based factors, which may provide unique information on the tissue microenvironment if the mechanisms can be further understood. The focus of this study was to investigate the effects of varied protein content on the calibration of MRS thermometry at 3 T, which has not been thoroughly explored in the literature. The effects of ionic concentration and magnetic field strength were also considered. Temperature reference materials were controlled by water circulation and freezing organic fixed‐point compounds (diphenyl ether and ethylene carbonate) stable to within 0.2 °C. The temperature was measured throughout the scan time with a fluoro‐optic probe, with an uncertainty of 0.16 °C. The probe was calibrated at the National Physical Laboratory (NPL) with traceability to the International Temperature Scale 1990 (ITS‐90). MRS thermometry measures were based on single‐voxel spectroscopy chemical shift differences between water and N‐acetylaspartate (NAA), Δ(H20‐NAA), using a Philips Achieva 3 T scanner. Six different phantom solutions with varying protein or ionic concentration, simulating potential tissue differences, were investigated within a temperature range of 21–42 °C. Results were compared with a similar study performed at 1.5 T to observe the effect of field strengths. Temperature calibration curves were plotted to convert Δ(H20‐NAA) to apparent temperature. The apparent temperature changed by ?0.2 °C/% of bovine serum albumin (BSA) and a trend of 0.5 °C/50 mM ionic concentration was observed. Differences in the calibration coefficients for the 10% BSA solution were seen in this study at 3 T compared with a study at 1.5 T. MRS thermometry may be utilized to measure temperature and the tissue microenvironment, which could provide unique unexplored information for brain abnormalities and other pathologies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
12.
Neurometabolic profiles of the substantia nigra and striatum of MPTP‐intoxicated common marmosets: An in vivo proton MRS study at 9.4 T
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hwon Heo Jae‐Bum Ahn Hyeong Hun Lee Euna Kwon Jun‐Won Yun Hyeonjin Kim Byeong‐Cheol Kang 《NMR in biomedicine》2017,30(2)
Given the strong coupling between the substantia nigra (SN) and striatum (STR) in the early stage of Parkinson's disease (PD), yet only a few studies reported to date that have simultaneously investigated the neurochemistry of these two brain regions in vivo, we performed longitudinal metabolic profiling in the SN and STR of 1‐methyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐intoxicated common marmoset monkey models of PD (n = 10) by using proton MRS (1H–MRS) at 9.4 T. T2 relaxometry was also performed in the SN by using MRI. Data were classified into control, MPTP_2weeks, and MPTP_6‐10 weeks groups according to the treatment duration. In the SN, T2 of the MPTP_6‐10 weeks group was lower than that of the control group (44.33 ± 1.75 versus 47.21 ± 2.47 ms, p < 0.05). The N‐acetylaspartate to total creatine ratio (NAA/tCr) and γ‐aminobutyric acid to tCr ratio (GABA/tCr) of the MPTP_6‐10 weeks group were lower than those of the control group (0.41 ± 0.04 versus 0.54 ± 0.08 (p < 0.01) and 0.19 ± 0.03 versus 0.30 ± 0.09 (p < 0.05), respectively). The glutathione to tCr ratio (GSH/tCr) was correlated with T2 for the MPTP_6‐10 weeks group (r = 0.83, p = 0.04). In the STR, however, GABA/tCr of the MPTP_6‐10 weeks group was higher than that of the control group (0.25 ± 0.10 versus 0.16 ± 0.05, p < 0.05). These findings may be an in vivo depiction of the altered basal ganglion circuit in PD brain resulting from the degeneration of nigral dopaminergic neurons and disruption of nigrostriatal dopaminergic projections. Given the important role of non‐human primates in translational studies, our findings provide better understanding of the complicated evolution of PD. 相似文献
13.
Karthik Lakshmanan Ryan Brown Guillaume Madelin Yongxian Qian Fernando Boada Graham C. Wiggins 《NMR in biomedicine》2018,31(2)
The purpose of this work is to illustrate a new coil decoupling strategy and its application to a transmit/receive sodium/proton phased array for magnetic resonance imaging (MRI) of the human brain. We implemented an array of eight triangular coils that encircled the head. The ensemble of coils was arranged to form a modified degenerate mode birdcage whose eight shared rungs were offset from the z‐axis at interleaved angles of ±30°. This key geometric modification resulted in triangular elements whose vertices were shared between next‐nearest neighbors, which provided a convenient location for counter‐wound decoupling inductors, whilst nearest‐neighbor decoupling was addressed with shared capacitors along the rungs. This decoupling strategy alleviated the strong interaction that is characteristic of array coils at low frequency (32.6 MHz in this case) and allowed the coil to operate efficiently in transceive mode. The sodium array provided a 1.6‐fold signal‐to‐noise ratio advantage over a dual‐nuclei birdcage coil in the center of the head and up to 2.3‐fold gain in the periphery. The array enabled sodium MRI of the brain with 5‐mm isotropic resolution in approximately 13 min, thus helping to overcome low sodium MR sensitivity and improving quantification in neurological studies. An eight‐channel proton array was integrated into the sodium array to enable anatomical imaging. 相似文献
14.
Six fucose‐α(1–2) sugars and α‐fucose assigned in the human brain using in vivo two‐dimensional MRS
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Carolyn Mountford Scott Quadrelli Alexander Lin Saadallah Ramadan 《NMR in biomedicine》2015,28(3):291-296
A growing body of literature has indicated that fucose‐α(1–2)‐galactose sugars are implicated in the molecular mechanisms that underlie neuronal development, learning and memory in the human brain. An understanding of the in vivo roles played by these terminal fucose residues has been hampered by the lack of technology to non‐invasively monitor their levels in the human brain. We have implemented in vivo two‐dimensional MRS technology to examine the human brain in a 3‐T clinical MR scanner, and report that six fucose‐α(1–2)‐galactose residues and free α‐fucose are available for inspection. Fucose‐α(1–3)‐galactose residues cannot yet be assigned using this technology as they resonate under the water resonance. This new application offers an unprecedented insight into the molecular mechanisms by which fucosylated sugars contribute to neuronal processes and how they alter during development, ageing and disease. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
15.
Changho Choi Sandeep Ganji Keith Hulsey Akshay Madan Zoltan Kovacs Ivan Dimitrov Song Zhang Kumar Pichumani Dianne Mendelsohn Bruce Mickey Craig Malloy Robert Bachoo Ralph DeBerardinis Elizabeth Maher 《NMR in biomedicine》2013,26(10):1242-1250
2‐Hydroxyglutarate (2HG) is produced in gliomas with mutations of isocitrate dehydrogenase (IDH) 1 and 2. The 1H resonances of the J‐coupled spins of 2HG are extensively overlapped with signals from other metabolites. Here, we report a comparative study at 3 T of the utility of the point‐resolved spectroscopy sequence with a standard short TE (35 ms) and a long TE (97 ms), which had been theoretically designed for the detection of the 2HG 2.25‐ppm resonance. The performance of the methods is evaluated using data from phantoms, seven healthy volunteers and 22 subjects with IDH‐mutated gliomas. The results indicate that TE = 97 ms provides higher detectability of 2HG than TE = 35 ms, and that this improved capability is gained when data are analyzed with basis spectra that include the effects of the volume localizing radiofrequency and gradient pulses. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
Jamie Near Jesper Andersson Eduard Maron Ralf Mekle Rolf Gruetter Philip Cowen Peter Jezzard 《NMR in biomedicine》2013,26(11):1353-1362
Short‐TE MRS has been proposed recently as a method for the in vivo detection and quantification of γ‐aminobutyric acid (GABA) in the human brain at 3 T. In this study, we investigated the accuracy and reproducibility of short‐TE MRS measurements of GABA at 3 T using both simulations and experiments. LCModel analysis was performed on a large number of simulated spectra with known metabolite input concentrations. Simulated spectra were generated using a range of spectral linewidths and signal‐to‐noise ratios to investigate the effect of varying experimental conditions, and analyses were performed using two different baseline models to investigate the effect of an inaccurate baseline model on GABA quantification. The results of these analyses indicated that, under experimental conditions corresponding to those typically observed in the occipital cortex, GABA concentration estimates are reproducible (mean reproducibility error, <20%), even when an incorrect baseline model is used. However, simulations indicate that the accuracy of GABA concentration estimates depends strongly on the experimental conditions (linewidth and signal‐to‐noise ratio). In addition to simulations, in vivo GABA measurements were performed using both spectral editing and short‐TE MRS in the occipital cortex of 14 healthy volunteers. Short‐TE MRS measurements of GABA exhibited a significant positive correlation with edited GABA measurements (R = 0.58, p < 0.05), suggesting that short‐TE measurements of GABA correspond well with measurements made using spectral editing techniques. Finally, within‐session reproducibility was assessed in the same 14 subjects using four consecutive short‐TE GABA measurements in the occipital cortex. Across all subjects, the average coefficient of variation of these four GABA measurements was 8.7 ± 4.9%. This study demonstrates that, under some experimental conditions, short‐TE MRS can be employed for the reproducible detection of GABA at 3 T, but that the technique should be used with caution, as the results are dependent on the experimental conditions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
17.
Sanaz Mohajeri Omkar B. Ijare Tedros Bezabeh Scott B. King M. Albert Thomas Gerald Minuk Jeremy Lipschitz Iain Kirkpatrick Mike Smith Ian C. P. Smith 《NMR in biomedicine》2014,27(10):1192-1202
In vitro 1H MRS of human bile has shown potential in the diagnosis of various hepatopancreatobiliary (HPB) diseases. Previously, in vivo 1H MRS of human bile in gallbladder using a 1.5 T scanner demonstrated the possibility of quantification of choline‐containing phospholipids (chol‐PLs). However, other lipid components such as bile acids play an important role in the pathophysiology of the HPB system. We have employed a higher magnetic field strength (3 T), and a custom‐built receive array coil, to improve the quality of in vivo 1H MRS of human bile in the gallbladder. We obtained significant improvement in the quality of 1D spectra (17 healthy volunteers) using a respiratory‐gated PRESS sequence with well distinguished signals for total bile acids (TBAs) plus cholesterol resonating at 0.66 ppm, taurine‐conjugated bile acids (TCBAs) at 3.08 ppm, chol‐PLs at 3.22 ppm, glycine‐conjugated bile acids (GCBAs) at 3.74 ppm, and the amide proton (?NH) arising from GCBAs and TCBAs in the region 7.76–8.05 ppm. The peak areas of these signals were measured by deconvolution, and subsequently the molar concentrations of metabolites were estimated with good accuracy, except for that of TBAs plus cholesterol. The concentration of TBAs plus cholesterol was overestimated in some cases, which could be due to lipid contamination. In addition, we report the first 2D L‐COSY spectra of human gallbladder bile in vivo (obtained in 15 healthy volunteers). 2D L‐COSY spectra will be helpful in differentiating various biliary chol‐PLs in pathological conditions of the HPB system. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
18.
Intra‐ and interindividual variability of fatty acid unsaturation in six different human adipose tissue compartments assessed by 1H‐MRS in vivo at 3 T
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jürgen Machann Norbert Stefan Robert Wagner Malte Bongers Erwin Schleicher Andreas Fritsche Hans‐Ulrich Häring Konstantin Nikolaou Fritz Schick 《NMR in biomedicine》2017,30(9)
It is generally accepted that the amount and distribution of adipose tissue (AT) in the human body play an important role in the pathogenesis of metabolic diseases. In addition, metabolic effects of released saturated fatty acids (FAs) in blood are known to be more critical than those of unsaturated FAs. However, little is known about the variability in unsaturation of FAs in various AT compartments. The aim of this prospective study was the assessment of mono‐ and polyunsaturated FAs in various AT compartments by localized 1H‐MRS in order to obtain insight into the intra‐ and interindividual variability. Associations of FA unsaturation with intrahepatic lipids (IHLs), insulin sensitivity and related AT volumes were analyzed. Fifty healthy Caucasians (36 male, 14 female) participated in this study. Spectroscopic examinations were performed in subcutaneous adipose tissue in the neck (SCATneck), abdominal deep subcutaneous adipose tissue (DSCAT), abdominal superficial subcutaneous adipose tissue (SSCAT), visceral adipose tissue (VAT), tibial bone marrow (BM) and subcutaneous adipose tissue of the lower leg (SCATcalf) at 3 T. Unsaturated index (UI) was calculated by the ratio of olefinic and methyl resonances, polyunsaturated index (PUI) by the ratio of diallylic and methyl resonances. Volumes of AT compartments (by T1‐weighted MRI) and IHL (single‐voxel STEAM) were assessed at 1.5 T, insulin sensitivity by an oral glucose tolerance test. UI was highest for SCATcalf (0.622) and lowest for BM (0.527). Highest PUI was observed for SSCAT (0.108), lowest for BM (0.093). Significant intraindividual differences between UIs—but not PUIs—are present for most compartments. There is a non‐significant trend for higher UI in males but otherwise no correlation to anthropometric data (age, BMI). A significant negative correlation between UI and AT volume was observed for VAT but for none of the other compartments. Neither UIs nor PUIs show a relation with IHL; insulin sensitivity is significantly correlated to UI in BM (p < 0.01). Unsaturation indices in several distinct AT compartments are location dependent. Our cohort showed only moderate gender‐related differences, with a trend towards less unsaturated FAs (mainly PUI) in females. In BM, insulin resistant subjects are characterized by a higher UI compared with the insulin sensitive ones. Further studies in larger cohorts are necessary to gain further insight into unsaturation of AT. 相似文献
19.
Reproducibility and optimization of in vivo human diffusion‐weighted MRS of the corpus callosum at 3T and 7T
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Emily T. Wood Ayse Ece Ercan Francesca Branzoli Andrew Webb Pascal Sati Daniel S. Reich Itamar Ronen 《NMR in biomedicine》2015,28(8):976-987
Diffusion‐weighted MRS (DWS) of brain metabolites enables the study of cell‐specific alterations in tissue microstructure by probing the diffusion of intracellular metabolites. In particular, the diffusion properties of neuronal N‐acetylaspartate (NAA), typically co‐measured with N‐acetylaspartyl glutamate (NAAG) (NAA + NAAG = tNAA), have been shown to be sensitive to intraneuronal/axonal damage in pathologies such as stroke and multiple sclerosis. Lacking, so far, are empirical assessments of the reproducibility of DWS measures across time and subjects, as well as a systematic investigation of the optimal acquisition parameters for DWS experiments, both of which are sorely needed for clinical applications of the method. In this study, we acquired comprehensive single‐volume DWS datasets of the human corpus callosum at 3T and 7T. We investigated the inter‐ and intra‐subject variability of empirical and modeled diffusion properties of tNAA [Davg(tNAA) and Dmodel(tNAA), respectively]. Subsequently, we used a jackknife‐like resampling approach to explore the variance of these properties in partial data subsets reflecting different total scan durations. The coefficients of variation (CV) and repeatability coefficients (CR) for Davg(tNAA) and Dmodel(tNAA) were calculated for both 3T and 7T, with overall lower variability in the 7T results. Although this work is limited to the estimation of the diffusion properties in the corpus callosum, we show that a careful choice of diffusion‐weighting conditions at both field strengths allows the accurate measurement of tNAA diffusion properties in clinically relevant experimental time. Based on the resampling results, we suggest optimized acquisition schemes of 13‐min duration at 3T and 10‐min duration at 7T, whilst retaining low variability (CV ≈ 8%) for the tNAA diffusion measures. Power calculations for the estimation of Dmodel(tNAA) and Davg(tNAA) based on the suggested schemes show that less than 21 subjects per group are sufficient for the detection of a 10% effect between two groups in case–control studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
Andrew P. Prescot Todd Richards Stephen R. Dager Changho Choi Perry F. Renshaw 《NMR in biomedicine》2012,25(11):1245-1252
1H MRS investigations have reported altered glutamatergic neurotransmission in a variety of psychiatric disorders. The unraveling of glutamate from glutamine resonances is crucial for the interpretation of these observations, although this remains a challenge at clinical static magnetic field strengths. Glutamate resolution can be improved through an approach known as echo time (TE) averaging, which involves the acquisition and subsequent averaging of multiple TE steps. The process of TE averaging retains the central component of the glutamate methylene multiplet at 2.35 ppm, with the simultaneous attenuation of overlapping phase‐modulated coupled resonances of glutamine and N‐acetylaspartate. We have developed a novel post‐processing approach, termed phase‐adjusted echo time (PATE) averaging, for the retrieval of glutamine signals from a TE‐averaged 1H MRS dataset. The method works by the application of an optimal TE‐specific phase term, which is derived from spectral simulation, prior to averaging over TE space. The simulation procedures and preliminary in vivo spectra acquired from the human frontal lobe at 2.89 T are presented. Three metabolite normalization schemes were developed to evaluate the frontal lobe test–retest reliability for glutamine measurement in six subjects, and the resulting values were comparable with previous reports for within‐subject (9–14%) and inter‐subject (14–20%) measures. Using the acquisition parameters and TE range described, glutamine quantification is possible in approximately 10 min. The post‐processing methods described can also be applied retrospectively to extract glutamine and glutamate levels from previously acquired TE‐averaged 1H MRS datasets. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献