Effect of PRESS and STEAM sequences on magnetic resonance spectroscopic liver fat quantification

Purpose

To compare PRESS and STEAM MR spectroscopy for assessment of liver fat in human subjects.

Materials and Methods

Single‐voxel (20 × 20 × 20 mm) PRESS and STEAM spectra were obtained at 1.5T in 49 human subjects with known or suspected fatty liver disease. PRESS and STEAM sequences were obtained with fixed TR (1500 msec) and different TE (five PRESS spectra between TE 30‐70 msec, five STEAM spectra between TE 20–60 msec). Spectra were quantified and T2 and T2‐corrected peak area were calculated by different techniques. The values were compared for PRESS and STEAM.

Results

Water T2 values from PRESS and STEAM were not significantly different (P = 0.33). Fat peak T2s were 25%–50% shorter on PRESS than on STEAM (P < 0.02 for all comparisons) and there was no correlation between T2s of individual peaks. PRESS systematically overestimated the relative fat peak areas (by 7%–263%) compared to STEAM (P < 0.005 for all comparisons). The peak area given by PRESS was more dependent on the T2‐correction technique than STEAM.

Conclusion

Measured liver fat depends on the MRS sequence used. Compared to STEAM, PRESS underestimates T2 values of fat, overestimates fat fraction, and provides a less consistent fat fraction estimate, probably due to J coupling effects. J. Magn. Reson. Imaging 2009;30:145–152. © 2009 Wiley‐Liss, Inc.     

1H MR spectroscopy using TE averaged PRESS: a more sensitive technique to detect neurodegeneration associated with Alzheimer's disease.

A sensitive proton magnetic resonance spectroscopy ((1)H MRS) acquisition scheme that is capable of discriminating between normal controls and a group of patients with early Alzheimer's disease (AD) is presented. The performance of this newly developed method, TE averaged PRESS (PRESS-J), in detecting neurodegeneration associated with early AD is compared with that of short echo time (TE) PRESS. A stepwise discriminant function analysis is used to construct discriminant functions for both pulse sequences. These functions are each composed of a single predictor: the N-acetyl aspartate (NAA)/creatine (Cr) ratio for PRESS-J, and the NAA/myoInositol (mI) ratio for PRESS. We observed lower P-values, higher areas under the receiver operating characteristic curves, and higher sensitivity at a given specificity for the PRESS-J discriminating function in comparison with the PRESS discriminating function. The higher sensitivity of PRESS-J is due to decreased variability when the singlets are fit in the spectra. This increased sensitivity enables new MR applications and, among other benefits, allows for smaller group sizes in drug trials, which can significantly reduce the cost of such trials.     

Long echo time proton magnetic resonance spectroscopy for estimating relative measures of lipid unsaturation at 3 T

Purpose:

To examine the behavior of lipid olefinic and diallylic resonances as a function of PRESS (point resolved spectroscopy) echo time (TE) to determine an optimal long TE value for their measurement at 3 T.

Materials and Methods:

Experiments were conducted on nine oils (almond, canola, cod liver, corn, linseed, peanut, sesame, sunflower, and walnut oil) and on vertebral and tibial bone marrow in vivo at 3 T. The methylene (or methyl + methylene), diallylic, and olefinic resonances were measured with PRESS with multiple TEs.

Results:

J‐coupling evolution effects on the olefinic and diallylic peaks appeared to be minimized when TE = 200 msec. The TE = 200 msec olefinic/methylene and diallylic/methylene peak area ratios calculated for each oil correlated well with ratios deduced from oil compositions in the literature (R² = 0.92 and 0.98 for the olefinic and diallylic protons, respectively). In addition, the relative amounts of bone marrow unsaturation of vertebral and tibial bone marrow inferred from the TE = 200 msec olefinic/(methyl + methylene) peak area ratio agreed with values estimated from the literature.

Conclusion:

A PRESS sequence with a long TE value of 200 msec is suitable for determining relative amounts of lipid unsaturation at 3 T. J. Magn. Reson. Imaging 2013;37:944–949. © 2012 Wiley Periodicals, Inc.     

Localized proton MR spectroscopy of the brain in children

Small-voxel (3.0–8.0 cm³), magnetic resonance (MR) imaging–guided proton MR spectroscopy was performed in 54 patients (aged 6 days to 19 years) with intracranial masses (n = 16), neurodegenerative disorders (n = 34), and other neurologic diseases (n = 4) and in 23 age-matched control subjects without brain disease. A combined short TE (18 msec) stimulatedecho acquisition mode (STEAM) and long TE (135 and/or 270 msec) spin-echo point-resolved spatially localized spectroscopy (PRESS) protocol, using designed radio-frequency pulses, was performed at 1.5 T. STEAM spectra revealed short T2 and/or strongly coupled metabolites; prominent resonances were obtained from N-acetyl aspartate (NAA), choline-containing compounds (Cho), and total creatine (tCr). Lactate was well resolved with the long TE PRESS sequence. Intracranial tumors were readily differentiated from cerebrospinal fluid (CSF) collections. All tumors showed low NAA, high Cho, and reduced tCr levels. Neurodegenerative disorders showed low or absent NAA levels and enhanced mobile lipid, glutamate and glutamine, and inositol levels, consistent with neuronal loss, gliosis, demyelination, and amino acid neuro-toxicity. Preliminary experience indicates that proton MR spectroscopy can contribute in the evaluation of central nervous system abnormalities of infants and children.     

Optimized glutamate detection at 3T

Purpose:

To identify the pulse sequence and acquisition parameters that result in the most accurate and repeatable measurements of glutamate (Glu) concentration in the brain at 3T.

Materials and Methods:

Simulations were performed to compare the accuracy and repeatability of 11 pulse sequences and acquisition parameters, within four general classes (PRESS, STEAM, Carr–Purcell PRESS [CPRESS] and TE averaged PRESS [JPRESS]), the majority of which were previously suggested as optimal for Glu detection. Three of the simulated acquisitions were implemented in a clinical scanner and measures of repeatability in vivo were compared to their simulated values.

Results:

Good agreement was demonstrated between simulated and experimentally determined measures of repeatability. Among the acquisitions considered, a CPRESS sequence with minimal echo time, together with, possibly, a short TE PRESS sequence, result in the most repeatable within session Glu measurements, while slightly overestimating the Glu concentration. Excellent accuracy is demonstrated by the simulations for a JPRESS sequence, at the expense of lower repeatability than optimal PRESS or CPRESS sequences.

Conclusion:

Further proof of concept is presented toward validation of a simulation approach to understand pulse sequence performance in measuring the concentration of a given metabolite. Improved within session Glu measurement repeatability is predicted for CPRESS and demonstrated in vivo. J. Magn. Reson. Imaging 2009;30:1155–1162. © 2009 Wiley‐Liss, Inc.     

Prostate spectroscopy at 3 Tesla using two‐dimensional S‐PRESS

Two‐dimensional (2D) strong‐coupling point‐resolved spectroscopy (S‐PRESS) is introduced as a novel approach to ¹H MR spectroscopy (MRS) in the prostate. The technique provides full spectral information and allows for an accurate characterization of the citrate (Cit) signal. The method is based on acquiring a series of PRESS spectra with constant total echo time (TE). The indirect dimension is encoded by varying the relative lengths of the first and second TEs (TE₁ + TE₂ = TE). In the resulting 2D spectra, only the signal of strongly coupled spin systems is spread into the second dimension, which leads to more clearly arranged spectra. Furthermore, the spectral parameters of Cit (coupling constant J and chemical shift difference δ of the AB spin system) can be determined with high accuracy in vivo. The sequence is analytically optimized for maximal “strong coupling peaks” of Cit at 3T. 2D S‐PRESS spectra are compared with JPRESS spectra in vitro as well as in vivo. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.     

Very short echo time improves the precision of glutamate detection at 3T in 1H magnetic resonance spectroscopy

Purpose:

To examine the precision of glutamate detection using a very short echo time (TE) phase rotation STEAM (PR‐STEAM) sequence.

Materials and Methods:

Spectrosopic data were acquired from the anterior cingulate gyrus in nine healthy adults using 6.5‐msec TE PR‐STEAM, 40‐msec TE PRESS, 72‐msec TE STEAM, and TE‐Averaging with an effective TE of 105 msec on a clinical 3T magnetic resonance imaging (MRI) system. All data were quantified using LCModel and reported as ratios relative to total creatine.

Results:

Glutamate Cramer‐Rao lower bounds were less than 8% for all sequences. The 6.5‐msec TE PR‐STEAM identified glutamate with the greatest precision (coefficient of variation [CV] of 7.1%), followed by TE‐Averaging (CV of 8.9%), 40‐msec TE PRESS (CV of 11.9%), and 72‐msec TE STEAM (CV of 13.8%).

Conclusion:

In the absence of spectral editing, glutamate is best detected in the human brain at 3T using very short TEs. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Quantitative measurement of N‐acetyl‐aspartyl‐glutamate at 3 T using TE‐averaged PRESS spectroscopy and regularized lineshape deconvolution

This article introduces regularized lineshape deconvolution in conjunction with TE‐averaged PRESS spectroscopy to measure N‐acetyl‐aspartyl‐glutamate (NAAG). Averaging different echo times suppressed the signals of multiplets from strongly coupled spin systems near 2 ppm; thus, minimizing the interfering signals to detect the acetyl proton signal of NAAG. Signal distortion was corrected by lineshape deconvolution, and Tikhonov regularization was introduced to reduce noise amplification arising from deconvolution; as a result, spectral resolution was enhanced without significantly sacrificing signal‐to‐noise ratio (SNR). This new approach was used to measure NAAG in the two regions of interest of healthy volunteers, dominated by gray matter and white matter, respectively. The acetyl proton signal of NAAG was directly quantified by fitting the deconvoluted spectra to a Voigt‐lineshape spectral model function, yielding the NAAG–N‐acetyl‐aspartate (NAA) ratios of 0.11 ± 0.02 for the gray matter voxels (n = 8) and 0.18 ± 0.02 for the white matter voxels (n = 12). Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Comparative reliability of proton spectroscopy techniques designed to improve detection of J‐coupled metabolites

Improved detection of J‐coupled neurometabolites through the use of modified proton magnetic resonance spectroscopy (1H‐MRS) techniques has recently been reported. TE‐averaged point‐resolved spectroscopy (PRESS) uses the J modulation effects by averaging FIDs with differing echo times to improve detection of glutamate, while standard PRESS detection of glutamate can be improved by using an appropriate single echo determined from J‐modulation simulations. In the present study, the reliabilities of TE‐averaged PRESS, standard PRESS with TE = 40 ms, and standard PRESS with TE = 30 ms in detecting metabolite levels in the cingulate gyrus of the human brain at 3T were compared in six subjects. TE‐averaged PRESS measures showed a mean variability of 9% for N‐acetyl aspartate, choline, and creatine, compared with < 4% for the 30‐ and 40‐ms PRESS techniques. The coefficients of variation for glutamate were 10%, 7%, and 5% for TE‐averaged, 30‐ms, and 40‐ms PRESS, respectively. PRESS with a TE of 40 ms also demonstrated improved reliability for GABA and glutamine concentrations. These results show that with the appropriate selection of echo time standard PRESS can be a reliable ¹H‐MRS technique for the measurement of J‐coupled neurometabolites in the human brain and, moreover, compares favorably with at least one J‐edited technique. Magn Reson Med 60:964–969, 2008. © 2008 Wiley‐Liss, Inc.     

Diurnal stability of γ‐aminobutyric acid concentration in visual and sensorimotor cortex

Purpose:

To establish the diurnal stability of edited magnetic resonance spectroscopy measurements of gamma‐aminobutyric acid (GABA) in visual and sensorimotor regions of the brain.

Materials and Methods:

GABA measurements were made in two regions of the brain (an occipital, “visual” region and a “sensorimotor” region centered on the precentral gyrus) using the MEGA‐PRESS editing method, scanning eight healthy adults at five timepoints during a single day. GABA concentration was quantified from the ratio of the GABA integral to the unsuppressed water signal.

Results:

No significant effect of time on GABA concentration was seen (P = 0.35). GABA was shown to be significantly more concentrated in visual regions than in sensorimotor regions (1.10 i.u. and 1.03 i.u., respectively; P = 0.050). Coefficients of variability (CVs) across all subjects of 9.1% and 12% (visual and sensorimotor) were significantly higher than mean within‐subjects CVs of 6.5% and 8.8.

Conclusion:

This study demonstrates the excellent reproducibility of MEGA‐PRESS detection of GABA, demonstrating that the method is sufficiently sensitive to detect inter‐subject variability, and suggests that (within the sensitivity limits of current measurements) time of day can be ignored in the design of MRS studies of visual and sensorimotor regions. J. Magn. Reson. Imaging 2010;31:204–209. © 2009 Wiley‐Liss, Inc.     

Interindividual,repositioning, and time‐of‐day effects on single voxel proton MR spectroscopy of the anterior cingulate cortex

Purpose:

To measure interindividual, repositioning, and time‐of‐day effects of single voxel PRESS (P oint RES olved S pectroscopy) proton magnetic resonance spectroscopy (¹H‐MRS) acquisition of the anterior cingulate cortex (AC) in healthy human subjects.

Materials and Methods:

AC ¹H‐MRS measurements were performed in 15 healthy adult volunteers using a short echo PRESS sequence (GE Healthcare 3 Tesla, TE/TR = 30/2500 ms, 192 acquisitions, 6 cm³ voxels). For each individual, a total of eight spectra were obtained during two identical scanning sessions separated by 3.5 h. In each, two consecutive AC spectra were acquired. After the first two scans, the subject left the scanner, then immediately returned for repositioning and acquisition of two more consecutive spectra. The subject then left the imaging centre to return 3.5 h later for a repeated procedure. Spectroscopic postprocessing was done using LCmodel. Interindividual, repositioning and time‐of‐day effects were measured using restricted maximum likelihood (REML) models of variance components analysis, where response variables were levels of creatine/phosphocreatine (Cr), N‐acetyl‐aspartate (NAA), myo‐inositol (mI), choline (Cho), and the glutamate‐glutamine complex (Glx).

Results:

Interindividual effects were markedly higher than time‐of‐day and repositioning effects for all metabolites.

Conclusion:

Our findings show that ¹H‐MRS measurements of the AC are sensitive to interindividual differences, while time of day and repositioning are markedly less important. J. Magn. Reson. Imaging 2010;32:276–282. © 2010 Wiley‐Liss, Inc.     

Proton MR spectroscopy in neuroborreliosis: a preliminary study

We report results of a magnetic resonance spectroscopy (MRS) study in 12 patients with neuroborreliosis. We used a PRESS sequence, placing an 8 cm³ voxel in normal-appearing white matter of the frontal lobe. Peaks indicating N-acetylaspartate (NAA), choline (Cho), creatine (Cr), myo-inositol (mI), lipids (Lip) and lactate (Lac) were identified and ratios of NAA/Cr, Cho/Cr, mI/Cr, Lip/Cr, Lac/Cr calculated. Significant increases in Cho/Cr and Lip/Cr were noted. No abnormality was found in mean NAA/Cr and Lac/Cr, but in four patients there was a decreased NAA peak; mI/Cr ratio was slightly increased. Although the spectroscopic profile in patients with neuroborreliosis seems to be nonspecific, MRS might be useful for assessing tissue damage of the central nervous system.     

Edited MRS is sensitive to changes in lactate concentration during inspiratory hypoxia

Purpose:

To demonstrate the application of Mescher‐Garwood (MEGA) point‐resolved spectroscopy sequence (PRESS) editing to the detection of lactate in the brain at 3T and to investigate changes in lactate concentration associated with inspiratory gas challenges.

Materials and Methods:

Edited lactate measurements were made in six healthy volunteers while the subjects breathed normoxic (21% O₂), hypoxic (12% O₂), and hyperoxic (40% O₂) gas mixtures. Lactate concentration was quantified relative to the unsuppressed water signal from the same volume.

Results:

Lactate concentration was elevated in all subjects during hypoxia in a highly significant fashion (mean increase = 39%; P = 0.0003). There was no significant change seen in hyperoxia.

Conclusion:

MEGA‐PRESS editing at 3T is sufficiently sensitive to detect lactate in the healthy brain with good signal‐to‐noise ratio (SNR), and can be used to investigate changes in cerebral metabolism arising during inspiratory gas challenges. J. Magn. Reson. Imaging 2010;32:320–325. © 2010 Wiley‐Liss, Inc.     

A multicenter study of two magnetic resonance spectroscopy techniques in individuals with HIV dementia

PURPOSE: To evaluate single-voxel proton magnetic resonance spectroscopy (SV-MRS) and magnetic resonance spectroscopic imaging (MRSI) metabolite results in individuals with HIV dementia. MATERIALS AND METHODS: Twenty HIV-positive (HIV+) individuals underwent SV-MRS (TE 35 msec) and MRSI (TE 280 msec). Results were stratified according to serostatus, dementia severity, psychomotor speed performance, and functional impairment. RESULTS: HIV+ individuals with psychomotor slowing had an increased myoinositol/creatine (mI/Cr) ratio (0.63 vs. 0.45) in the frontal white matter using SV-MRS and an increased choline (Cho)/Cr ratio (1.88 vs. 1.41) in the mesial frontal gray matter using MRSI compared to HIV+ individuals without psychomotor slowing. Using MRSI, subjects with HIV dementia also had a decreased N-acetyl aspartate (NAA)/Cho ratio (1.55 vs. 2.53) compared to HIV+ individuals without cognitive impairment in the mesial frontal gray matter. Both techniques detected metabolite ratio abnormalities associated with abnormal functional performance. CONCLUSION: SV-MRS and MRSI offer complementary roles in evaluating individuals with HIV dementia. Short TE SV-MRS measures mI, which may be elevated in early HIV dementia, whereas MRSI provides wider spatial coverage to examine specific regional changes.     

Proton MR spectroscopic measurement of neurometabolites in hepatic encephalopathy during oral lactulose therapy.

BACKGROUND AND PURPOSEMR imaging and MR spectroscopy are increasingly being used to determine response to pharmacologic therapy. Hepatic encephalopathy (HE) is characterized by abnormal cerebral metabolites, yet the response to lactulose and other anti-HE measures is still primarily determined by using arbitrary categorical clinical rating scales, rather than MR spectroscopy. The purpose of this study was to determine whether MR spectroscopy could demonstrate relevant neurometabolic changes associated with lactulose therapy and thereby provide further support for the use of MR spectroscopy in clinical trials.METHODSTen control subjects and 23 patients with grades I to III HE were studied by proton MR spectroscopy with imaging parameters of 2000/26 (TR/TE). Metabolic ratios were calculated for myo-inositol (mI)/creatine (Cre), choline (Cho)/Cre, (glutamine + glutamate) (Glx)/Cre, N-acetylaspartate (NAA)/Cre, and (Cho + mI)/Glx. A time series design trial was used in which eight patients with HE were compared before and after lactulose therapy (60 mL by mouth three times per day).RESULTSRelative to control subjects, HE was characterized by 43%, 64%, and 5% reductions, respectively, in mI/Cre, (Cho + mI)/Glx, and Cho/Cre. In comparison, Glx/Cre was increased by 75% and NAA/Cre was not changed. Therapy with lactulose was associated with increases of 29%, 37%, and 7%, respectively, in mI/Cre, (Cho + mI)/Glx, and Cho/Cre, as well as respective decreases of 15% and 42%, respectively, in Glx/Cre and HE grade. NAA/Cre did not change with lactulose therapy.CONCLUSIONMR spectroscopy detects neurometabolic changes associated with pharmacologic therapy for HE. The metabolic ratios ml/Cre and (Cho + mI)/Glx are the most sensitive measures of lactulose effect. These data support the expanded use of MR spectroscopy as an adjunctive technique in pharmaceutical development and clinical trials for HE.     

Test‐retest reliability and reproducibility of short‐echo‐time spectroscopic imaging of human brain at 3T

A ¹H magnetic resonance spectroscopic imaging study at 3T and short echo time was conducted to evaluate both the reproducibility, as measured by the interscan coefficient of variation (CV), and test‐retest reliability, as measured by the intraclass correlation coefficient (ICC), of measurements of glutamate (Glu), combined glutamate and glutamine (Glx), myo‐inositol (mI), N‐acetylaspartate, creatine, and choline in 21 healthy subjects. The effect of partial volume correction on these measures and the relationship of reproducibility and reliability to data quality were also examined. A ¹H magnetic resonance spectroscopic imaging slice was prescribed above the lateral ventricles and single repeat scans were performed within 30 min to minimize physiologic variability. Interscan CVs based on all the voxels varied from 0.05 to 0.07 for N‐acetylaspartate, creatine, and choline to 0.10–0.13 for mI, Glu, and Glx. Findings on the reproducibility of gray and white matter estimates of N‐acetylaspartate, creatine, and choline are consistent with previous studies using longer echo times, with CVs in the range of 0.02–0.04 and ICC in the range of 0.65–0.90. CVs for Glu, Glx, and mI are much lower than reported in previous studies at 1.5T, while white matter mI (CV = 0.04, ICC = 0.93) and gray matter Glx (CV = 0.04, ICC = 0.68) demonstrated both high reproducibility and test‐retest reliability. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Effect of J-coupling on lipid composition determination with localized proton magnetic resonance spectroscopy at 9.4 T

Purpose:

To demonstrate, at 9.4 T, that J‐coupling interactions exhibited by lipid protons affects lipid composition determination with a point resolved spectroscopy (PRESS) sequence.

Materials and Methods:

Experiments were conducted on four oils (almond, corn, sesame, and sunflower), on visceral adipose tissue of a euthanized mouse, and on pure linoleic acid at 9.4 T. The 2.1, 2.3, and 2.8 ppm resonances were measured at multiple echo times (TEs) by a standard PRESS sequence and by a PRESS sequence consisting of narrow‐bandwidth refocusing pulses designed to rewind the J‐coupling evolution of the target peak protons in the voxel of interest. T₂ corrections were performed on both groups of data for the three peaks and lipid compositions for the oils and for the mouse tissue were determined. Lipid compositions were also calculated from a short‐TE standard PRESS spectrum.

Results:

A chemical analysis of the samples was not performed; however, the oil compositions calculated from resonance peaks acquired with the PRESS sequence designed to minimize J‐coupling effects, following T₂ relaxation correction, closely agreed with values in the literature, which was not the case for all of the compositions determined from the regular PRESS spectra.

Conclusion:

The presented work brings to attention the significance of J‐coupling effects when calculating lipid compositions from localized proton spectra. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

Proton MR spectroscopy in mild cognitive impairment and Alzheimer disease: comparison of 1.5 and 3 T

BACKGROUND AND PURPOSE: Theoretically, proton ((1)H) MR spectroscopy at a higher field strength has the advantages of higher signal-to-noise ratio and improved spectral resolution. We therefore compared the ability of single-voxel (1)H MR spectroscopy at 1.5 and 3 T to diagnostically discriminate among cognitively normal elderly subjects, patients with mild cognitive impairment (MCI), and patients with Alzheimer disease (AD). METHODS: At both 1.5 and 3 T, we studied 41 cognitively normal elderly subjects, 20 patients with MCI, and 20 patients with AD. In each subject, (1)H MR spectroscopy was performed at TEs of 30 and 135 ms and from voxels placed over the posterior cingulate gyri. RESULTS: Average line widths and interexamination variability of metabolite ratios were higher at 3 T than at 1.5 T. Consistent quantification of glutamine (Gln) + glutamate/creatine (Cr) and Gln/Cr peak ratios occurred at 3 T but not at 1.5 T. Choline (Cho)/Cr (at TE = 135 ms) and myo-inositol (MI)/Cr were higher and N-acetylaspartate (NAA)/Cr (at TE = 135 ms) and NAA/MI were lower in patients with MCI than in cognitively normal subjects only at 1.5 T. MI/Cr and Cho/Cr were higher and NAA/Cr and NAA/MI were lower in patients with AD than in cognitively normal subjects at both 1.5 and 3 T. Differentiation of patients with AD from cognitively normal subjects by using the NAA/MI data was similar at both field strengths (P >.05). CONCLUSION: With currently available technology, the diagnostic performance of (1)H MR spectroscopy in patients with MCI and those with AD was not better at 3 T than at 1.5 T.     

Dysembryoplastic neuroepithelial tumors: proton MR spectroscopy,diffusion and perfusion characteristics

Introduction We describe the magnetic resonance (MR) imaging characteristics of dysembryoplastic neuroepithelial tumors (DNT) and discuss their differential diagnosis. Material and methods Proton MR spectroscopy (TE 30 and 136 ms), diffusion-weighted and perfusion images were retrospectively evaluated in 22 patients with pathologically proven DNT (17 male and 5 female, mean age 18.7 years) and 14 control subjects (10 male and 4 female, mean age 16.9 years). The results from the DNT patients and from the control subjects were compared using an independent sample t-test and the degree of correlation was tested by Pearson’s correlation. Results All DNTs were solitary and in a supratentorial cortical or subcortical location (ten temporal, eight frontal and four parietal). They had low-signal on T1-weighted images and high-signal on T2-weighted images without a prominent mass effect. Additionally a cystic appearance (six patients, 27.3%), cortical dysplasia (six patients, 27.3%) and contrast enhancement (four patients, 18.2%) were also noted. No significant differences were detected in NAA/Cho, NAA/Cr, NAA/Cho+Cr or Cho/Cr ratios between DNT and normal brain. DNTs had a significantly higher mI/Cr ratio and apparent diffusion coefficient (ADC) values and lower cerebral blood values than normal parenchyma (P < 0.001). ADC had the highest correlation with the diagnosis of DNT (r = 0.996) followed by relative cerebral blood volume (rCBV) (r = −0.883) and mI/Cr ratio (r = 0.663). Conclusion Proton MR spectroscopy, diffusion-weighted and perfusion imaging characteristics of DNTs provide additional information to their MR imaging findings. The MR spectrum showing a slight increase in mI/Cr ratio, and higher ADC and lower rCBV values than normal parenchyma help to differentiate DNTs from other cortical tumors, which had higher rCBV and lower ADC values than DNTs. This work was presented at the ASNR 45th Annual Meeting 2007.     

双额叶脑代谢物浓度改变与轻度认知功能障碍的磁共振波谱量化研究

目的:用磁共振频谱(MRS)结合LCModel分析软件定量研究轻度认知功能障碍(MCI)患者双额叶脑代谢物浓度的变化及与脑白质脱髓鞘的关系。方法:前瞻性收集2016年5月至2018年12月于汕头大学医学院第二附属医院就诊的25例神经心理学测试结果为MCI者,记为A组[男12例,女13例,年龄(60.5±5.2)岁],按...