Magnetic resonance T2‐relaxometry and 2D L‐correlated spectroscopy in patients with minimal hepatic encephalopathy

Purpose:

To evaluate T₂‐relaxation changes in patients with minimal hepatic encephalopathy (MHE) using T₂ relaxometry and to correlate T₂ values with brain metabolites evaluated using 2D magnetic resonance spectroscopy (MRS).

Materials and Methods:

Eight MHE patients and 13 healthy subjects were evaluated using T₂ relaxometry, and eight patients and nine healthy subjects underwent 2D MRS in right frontal and left occipital regions. Whole‐brain T₂‐relaxation maps were compared between MHE and control subjects using analysis‐of‐covariance, with age and gender included as covariates. T₂ values derived from the right frontal and left occipital lobes were correlated with the metabolite ratios.

Results:

Multiple brain regions including anterior and mid cingulate cortices, right anterior and left posterior insular cortices, right prefrontal, medial frontal, and right superior temporal cortices showed significantly increased T₂ values in MHE patients compared to control subjects. MRS showed significantly increased ratios of glutamine/glutamate (Glx) and decreased ratios of myo‐inositol, taurine, choline, and myo‐inositol/choline (mICh) with respect to creatine (Cr_d) in patients compared to controls. Frontal Glx/Cr_d showed significantly positive correlation with T₂ values.

Conclusion:

MHE patients showed significantly increased T₂ values in multiple brain regions reflecting increased free water content and T₂ values in frontal lobe correlated with the increased Glx/Cr_d ratio. J. Magn. Reson. Imaging 2009;30:1034–1041. © 2009 Wiley‐Liss, Inc.     

T2* MRI of minimal hepatic encephalopathy and cognitive correlates in vivo

Purpose:

To evaluate regional brain iron deposition in minimal hepatic encephalopathy (MHE) patients using T2*‐weighted gradient‐echo imaging and to explore the relationship between T2* MR changes and cognitive performance.

Materials and Methods:

Forty hepatitis‐B virus (HBV)‐related cirrhotic patients and 22 age‐, sex‐, and education‐matched healthy controls were included in this study. Of the patients, twenty eight patients were diagnosed with MHE. All subjects were administered Number Connection Test‐A (NCT‐A), Letter Digit Substitution Test (LDST), Rey‐Osterrieth Complex Figure Test (RCFT), and the Mini‐Mental State Examination (MMSE). T2*‐weighted gradient‐echo images were acquired using 3 Tesla MRI. Phase values (putative iron levels) in the frontal–basal ganglia–thalamocortical circuits were measured. Spearman correlation and multiple linear regression analysis were performed.

Results:

MHE patients exhibited significantly prolonged NCT‐A time and decreased LDST, RCFT immediate and delayed recall scores. Significant decreases of phase values in the bilateral putamen were detected in MHE patients compared to without MHE patients and controls. Multiple linear regression analysis confirmed significant correlations between the phase values in the putamen and right frontal white matter and cognitive performances by MHE patients.

Conclusion:

Decreased phase values in the frontal cortical–basal ganglial circuits independently contribute to cognitive impairments in MHE patients. J. Magn. Reson. Imaging 2013;37:179–186. © 2012 Wiley Periodicals, Inc.     

轻微型肝性脑病患者脑的3T 1H-MRS研究

目的 利用3T氢质子磁共振波谱(1H-MRS)研究轻微型肝性脑病(MHE)与无MHE的肝硬化患者后扣带回和基底节代谢的改变,并评价其与Child-Pugh评分、静脉血氨及神经心理测试之间的关系.方法 对10例MHE患者、16例无MHE肝硬化患者和21例健康志愿者行后扣带回及右侧基底节单体素点分辨自旋回波波谱序列扫描.计算代谢物N-乙酰天门冬氨酸(NAA)、肌酐(Cr)、胆碱(Cho)、肌醇(mIns)、谷氨酰胺复合物(Glx)与Cr比值并进行三组间比较.所有研究对象在MRI检查前完成数字连接试验-A (NCT-A)、数字符号试验(DST).所有患者在MR检查前后三天内进行了静脉血氨水平检测.结果 在后扣带回,与正常对照组相比,MHE组和无MHE的肝硬化组的mIns/Cr(F=16.278,P＜0.001)及Cho/Cr(F =24.333,P＜0.001)都显著降低,Glx/Cr(F =0.908,P=0.411)有升高的趋势;与无MHE的肝硬化组相比,MHE组Cho/Cr进一步降低(P＜0,05).在右侧基底节区,与正常对照组相比,MHE组和无MHE的肝硬化组的mIns/Cr(F=19.083,P＜0.001)显著降低,只有MHE组Glx/Cr(P＜0.05)显著升高,Cho/Cr(F=1.677,P＜0.199)有降低趋势;与无MHE的肝硬化组相比MHE组各代谢物的差别无统计学意义.Pearson相关分析结果显示,仅右侧基底节的Cho/Cr与Child-pugh评分呈负相关(r=-0,444,P＜0,05).结论 肝硬化患者后扣带回及基底节区存在生化代谢的异常改变,且表现为区域不均质性,有MHE的肝硬化患者脑的生化代谢异常改变更加显著.后扣带回可作为检测肝硬化患者脑改变的一个敏感部位.     

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.     

Fire-Related Post-Traumatic Stress Disorder: Brain 1H-MR Spetroscopic Findings

Objective

To investigate the MR imaging and ¹H-MR spectroscopic findings of acute fire-related post-traumatic stress disorder (PTSD).

Materials and Methods

Sixteen patients (M:F=10:6; mean age, 16 years) with fire-related PTSD underwent MR imaging and ¹H-MR spectroscopy, and for control purposes, the procedures were repeated in eight age-matched normal volunteers. In all patients and controls, the regions of interest where data were acquired at MRS were the basal ganglia (BG), frontal periventricular white matter (FWM), and parietal periventricular white matter (PWM).

Results

In all patients with PTSD, MR images appeared normal. In contrast, MRS showed that in the BG, NAA/Cr ratios were significantly lower in patients than in volunteers. This decrease did not, however, show close correlation with the severity of the neuropsychiatric symptoms. In patients, neither NAA/Cr ratios in FWM nor PWM, nor Cho/Cr ratios in all three regions, were significantly different from those in the control group.

Conclusion

Decreased NAA/Cr ratios in the BG, as seen at ¹H-MRS, might be an early sign of acute fire-related PTSD.     

Reproducibility of MRI‐determined proton density fat fraction across two different MR scanner platforms

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.     

Volumetric MRI and 1H MRS study of hippocampus in unilateral MCAO patients: relationship between hippocampal secondary damage and cognitive disorder following stroke

Objective

To determine whether hippocampi alter in patients at the recovery stage of middle cerebral artery occlusion (MCAO) and whether the changes of hippocampi involve in the cognitive impairment in such patients.

Meterials and methods

Forty-four patients with unilateral infarction solely in MCAO territory and 44 age-, sex- and education background-matched healthy volunteers were enrolled in this study. All subjects underwent 3-dimensional fast spoiled gradient-echo (3D FSPGR) and sing-voxel proton magnetic resonance spectroscopy (¹H MRS) protocols at a 1.5 T MR scanner. The ratios of n-acetylaspartate/creatine (NAA/Cr) and myo-inositol/creatine (mI/Cr) were obtained by using software integrated in the MR scanner. The hippocampal volumes were estimated by manually measurement.

Results

The volume and NAA/Cr ratio were found significantly decreased and mI/Cr ratio significantly increased in the hippocampus ipsilateral to occluded middle cerebral artery (MCA) as compared with values in the contralateral hippocampus or healthy control. A reduced NAA/Cr ratio was also observed in contralateral hippocampus compared to controls. The shrinkage ratio of hippocampus ipsilateral to MCAO was found related to the Mini–Mental State Examination (MMSE) score.

Conclusion

Our study identified that the hippocampal secondary damage occurred in patients after MCAO, and it could be evaluated noninvasively by volumetric magnetic resonance imaging (MRI) and ¹H MRS. Moreover, the hippocampal secondary damage in MCAO patients indeed contributed to their cognitive impairment.     

Prospective motion correction for magnetic resonance spectroscopy using single camera Retro-Grate reflector optical tracking

Purpose:

To introduce and evaluate a method of prospective motion correction for localized proton magnetic resonance spectroscopy (1H‐MRS) using a single‐camera optical tracking system.

Materials and Methods:

Five healthy participants were scanned at 3T using a point‐resolved spectroscopic sequence (PRESS) with a motion‐tracking module and phase navigator. Head motion in six degrees was tracked with a Retro‐Grate Reflector (RGR) tracking system and target via a mirror mounted inside the bore. Participants performed a series of three predetermined motion patterns during scanning.

Results:

Left–right rotation (Rz) (average 12°) resulted in an increase in the total choline to total creatine ratio (Cho/Cr) of +14.6 ± 1.5% (P = 0.0009) for scans without correction, but no change for scans with correction (+1.1 ± 1.5%; P = 0.76). Spectra with uncorrected Z‐translations showed large lipid peaks (skull) with changes in Cho/Cr of ?13.2 ± 1.6% (P = 0.02, no motion correction) and ?2.2 ± 2.4% (P = 0.51) with correction enabled. There were no significant changes in the ratios of N‐acetylaspartate, glutamate+glutamine, or myo‐inositol to creatine compared to baseline scans for all experiments.

Conclusion:

Prospective motion correction for 1H‐MRS, using single‐camera RGR tracking, can reduce spectral artifacts and quantitation errors in Cho/Cr ratios due to head motion and promises improved spectral quality and reproducibility. J. Magn. Reson. Imaging 2011. © 2011 Wiley‐Liss, Inc.

     

In vivo MRS study of intraventricular tumors

Purpose:

To evaluate the role of MR spectroscopy (MRS) as a noninvasive tool for characterization of intraventricular brain tumors.

Materials and Methods:

Twenty‐three intraventricular tumors, all histologically classified (11 central neurocytomas [CNC], 5 meningiomas [Men], other intraventricular tumors [OIV], including 2 anaplastic gliomas [WHO III], 1 tumor each of rhabdoid tumor, glioneuronal hamartoma, GBM, hemangiopericytoma, and subependymoma II), were studied by MRS before surgery using a point‐resolved spectroscopic sequence (PRESS).

Results:

Statistically significant differences (P < 0.03) were observed for NAA/Cr and Cho/Cr between CNCs and OIV. A significant difference (P < 0.01) was observed in the presence of Gly between the CNCs and meningiomas, and CNCs and OIV. In addition, the presence of Ala was also significantly different (P < 0.01) between OIV and meningiomas, and OIV and CNCs.

Conclusion:

The present study has shown that MRS can be useful in characterizing intraventricular tumor and distinguishing CNCs from meningiomas and other intraventricular tumors. Prior information about intraventricular tumor types could be useful to clinicians in planning treatment and resection strategy. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

Usefulness of Single Voxel Proton MR Spectroscopy in the Evaluation of Hippocampal Sclerosis

Objective

The purpose of our study was to determine the ability of H-1 MR spectroscopy (MRS) to lateralize the lesion in patients with hippocampal sclerosis.

Materials and Methods

Twenty healthy volunteers and 25 patients with intractable temporal lobe epilepsy whose MR imaging diagnosis was unilateral hippocampal sclerosis were included. This diagnosis was based on the presence of unilateral atrophy and/or high T2 signal intensity of the hippocampus. Single-voxel H-1 MRS was carried out on a 1.5-T unit using PRESS sequence (TE, 136 msec). Spectra were obtained from hippocampal areas bilaterally with volumes of interest (VOIs) of 6.0 cm³ and 2.25 cm³ in healthy volunteers, and of either 6.0 cm³ (n = 14) or 2.25 cm³ (n = 11) in patients. Metabolite ratios of NAA/Cho and NAA/Cr were calculated from relative peak height measurements. The capability of MRS to lateralize the lesion and to detect bilateral abnormalities was compared with MR imaging diagnosis as a standard of reference.

Results

In healthy volunteers, NAA/Cho and NAA/Cr ratios were greater than 0.8 and 1.0, respectively. In patients, the mean values of these ratios were significantly lower on the lesion side than on the contralateral side, and lower than those of healthy volunteers (p < .05). The overall correct lateralization rate of MRS was 72% (18/25); this rate was lower with a VOI of 6.0 cm³ than of 2.25 cm³ (64% versus 82%, p < .05). Bilateral abnormalities on MRS were found in 24% (6/25) of cases.

Conclusion

Although its rate of correct lateralization is low, single-voxel H-1 MRS is a useful and promising diagnostic tool in the evaluation of hippocampal sclerosis, particularly for the detection of bilateral abnormalities. To improve the diagnostic accuracy of H-1 MRS, further investigation, including the use of a smaller VOI and measurement of the absolute amount of metabolites, are needed.     

Comparison of 3 Tesla proton MR spectroscopy, MR perfusion and MR diffusion for distinguishing glioma recurrence from posttreatment effects

Purpose:

To compare 3 Tesla (3T) multi‐voxel and single‐voxel proton MR spectroscopy (MRS), dynamic susceptibility contrast perfusion MRI (DSC), and diffusion‐weighted MRI (DWI) for distinguishing recurrent glioma from postradiation injury.

Materials and Methods:

We reviewed all 3T MRS, DSC and DWI studies performed for suspicion of malignant glioma recurrence between October 2006 and December 2008. Maximum Cho/NAA and Cho/Cr peak‐area and peak‐height ratios were recorded for both multi‐voxel and single‐voxel MRS. Maximum cerebral blood volume (CBV) and minimum apparent diffusion coefficient (ADC) were normalized to white matter. Histopathology and clinical‐radiologic follow‐up served as reference standards. Receiver operating characteristic curves for each parameter were compared.

Results:

Forty lesions were classified as glioma recurrence (n = 30) or posttreatment effect (n = 10). Diagnostic performance was similar for CBV ratio (AUC = 0.917, P < 0.001), multi‐voxel Cho/Cr peak‐area (AUC = 0.913, P = 0.002), and multi‐voxel Cho/NAA peak‐height (AUC = 0.913, P = 0.002), while ADC ratio (AUC = 0.726, P = 0.035) did not appear to perform as well. Single‐voxel MRS parameters did not reliably distinguish tumor recurrence from posttreatment effects.

Conclusion:

A 3T DSC and multi‐voxel MRS Cho/Cr peak‐area and Cho/NAA peak‐height appear to outperform DWI for distinguishing glioma recurrence from posttreatment effects. Single‐voxel MRS parameters do not appear to distinguish glioma recurrence from posttreatment effects reliably, and therefore should not be used in place of multi‐voxel MRS. J. Magn. Reson. Imaging 2012;35:56‐63. © 2011 Wiley Periodicals, Inc.     

Human brain MR spectroscopy thermometry using metabolite aqueous‐solution calibrations

Purpose:

To estimate absolute brain temperature using proton MR spectroscopy (¹H‐MRS) and mean brain–body temperature difference of healthy human volunteers.

Materials and Methods:

Chemical shift difference between temperature‐dependent water spectral line position and temperature‐stable metabolite spectral reference was used for the estimations of absolute brain temperature. Temperature calibrations constants were obtained from the spectra of the N‐acetyl aspartate (NAA line at ～2.0 ppm), glycero‐phosphocholine (GPC line at ～3.2 ppm), and creatine (Cr line at ～3.0 ppm) aqueous solutions with pH values within physiologically pertinent ranges. Single‐voxel PRESS sequence (TR/TE 2000/80 ms) was used for this purpose. Brain temperature was determined by averaging the temperatures computed from water‐Cho, water‐Cr, and water‐NAA chemical shift differences.

Results:

The mean brain temperature of 18 healthy volunteers was 38.1 ± 0.4°C and mean brain–body (rectal) temperature difference was 1.3 ± 0.4°C.

Conclusion:

Improved accuracy of the temperature constants and averaging the temperatures computed from water‐Cho, water‐Cr, and water‐NAA chemical shift differences increased the reliability of the brain temperature estimations. J. Magn. Reson. Imaging 2010;31:807–814. ©2010 Wiley‐Liss, Inc.     

Magnetization spoiling in radial FLASH contrast-enhanced MR digital subtraction angiography

Purpose:

To increase the in‐plane spatial resolution and image update rates of 2D magnetic resonance (MR) digital subtraction angiography (DSA) pulse sequences to 0.57 × 0.57 mm and 6 frames/sec, respectively, for intracranial vascular disease applications by developing a radial FLASH protocol and to characterize a new artifact, not previously described in the literature, which arises in the presence of such pulse sequences.

Materials and Methods:

The pulse sequence was optimized and artifacts were characterized using simulation and phantom studies. With Institutional Review Board (IRB) approval, the pulse sequence was used to acquire time‐resolved images from healthy human volunteers and patients with x‐ray DSA‐confirmed intracranial vascular disease.

Results:

Artifacts were shown to derive from inhomogeneous spoiling due to the nature of radial waveforms. Gradient spoiling strategies were proposed to eliminate the observed artifact by balancing gradient moments across TR intervals. The resulting radial 2D MR DSA sequence (2.6 sec temporal footprint, 6 frames/sec with sliding window factor 16, 0.57 × 0.57 mm in‐plane) demonstrated small vessel detail and corroborated x‐ray DSA findings in intracranial vascular imaging studies.

Conclusion:

Appropriate gradient spoiling in radial 2D MR DSA pulse sequences improves intracranial vascular depiction by eliminating circular banding artifacts. The proposed pulse sequence may provide a useful addition to clinically applied 2D MR DSA scans. J. Magn. Reson. Imaging 2012;36:249–258. © 2012 Wiley Periodicals, Inc.     

T(1) independent, T(2) (*) corrected chemical shift based fat-water separation with multi-peak fat spectral modeling is an accurate and precise measure of hepatic steatosis

Purpose:

To determine the precision and accuracy of hepatic fat‐fraction measured with a chemical shift‐based MRI fat‐water separation method, using single‐voxel MR spectroscopy (MRS) as a reference standard.

Materials and Methods:

In 42 patients, two repeated measurements were made using a T₁‐independent, T‐corrected chemical shift‐based fat‐water separation method with multi‐peak spectral modeling of fat, and T₂‐corrected single voxel MR spectroscopy. Precision was assessed through calculation of Bland‐Altman plots and concordance correlation intervals. Accuracy was assessed through linear regression between MRI and MRS. Sensitivity and specificity of MRI fat‐fractions for diagnosis of steatosis using MRS as a reference standard were also calculated.

Results:

Statistical analysis demonstrated excellent precision of MRI and MRS fat‐fractions, indicated by 95% confidence intervals (units of absolute percent) of [?2.66%,2.64%] for single MRI ROI measurements, [?0.81%,0.80%] for averaged MRI ROI, and [?2.70%,2.87%] for single‐voxel MRS. Linear regression between MRI and MRS indicated that the MRI method is highly accurate. Sensitivity and specificity for detection of steatosis using averaged MRI ROI were 100% and 94%, respectively. The relationship between hepatic fat‐fraction and body mass index was examined.

Conclusion:

Fat‐fraction measured with T₁‐independent T‐corrected MRI and multi‐peak spectral modeling of fat is a highly precise and accurate method of quantifying hepatic steatosis. J. Magn. Reson. Imaging 2011;33:873–881. © 2011 Wiley‐Liss, Inc.

     

Fast T2*-weighted MRI of the prostate at 3 Tesla

Purpose:

To describe a rapid T2*‐weighted (T2*W), three‐dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1‐weighted turbo‐spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS).

Materials and Methods:

B₀ susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k‐space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six‐channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed.

Results:

Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W‐positive areas. Post‐biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS.

Conclusion:

The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T. J. Magn. Reson. Imaging 2011;33:902–907. © 2011 Wiley‐Liss, Inc.     

Evaluation of metabolic changes within the normal appearing gray and white matters in neurologically asymptomatic HIV-1-positive and HCV-positive patients: Magnetic resonance spectroscopy and immunologic correlation

Objective

The aim of the study was to evaluate early metabolic changes using proton MR spectroscopy (MRS) in asymptomatic HIV-1-positive and HCV-positive patients without abnormalities in the structural MR examination.

Methods

Sixty-five asymptomatic patients: 21 HIV-1-positive naive, 20 HIV-1-positive with combination antiretroviral therapy (cART), 9 HIV-1/HCV-positive naive, 15 HCV-positive naive and 18 normal subjects were enrolled in the study. The MRS examinations were performed with a 1.5 T MR scanner. Voxels were located in the following regions: posterior cingulate gyrus (PCG), anterior cingulate gyrus (ACG), parietal white matter (PWM), left basal ganglia (BG) and frontal white matter (FWM). The NAA/Cr, Cho/Cr, mI/Cr ratios and correlations of MRS measurements with the immunologic data were analyzed.

Results

There was a significant decrease (p < 0.05) of the NAA/Cr ratios in PCG, ACG and PWM regions in HIV-1-positive cART treated patients compared to the normal subjects. The significantly decreased NAA/Cr ratios in PWM and FWM were observed in HCV infected patients. The subjects with HIV-1/HCV co-infection revealed significantly lower NAA/Cr ratios in the ACG area. Other metabolite ratios in all analyzed regions, as well as the NAA/Cr ratios in BG showed no significant differences. The decrease of CD4n T cell count was associated with the decease of the NAA/Cr ratio in the PCG area and the increase of Cho/Cr ratio in the FWM region.

Conclusions

The metabolic changes – reduction of NAA/Cr ratios are most pronounced in HIV-1-positive patients using cART. The low CD4n T cell count is a risk factor for neurocognitive impairment in HIV-1-positive patients.     

Metabolic alterations: A biomarker for radiation‐induced normal brain injury—an MR spectroscopy study

Purpose

To assess if interval changes in metabolic status in normal cerebral tissue after radiation therapy (RT) can be detected by 2D CSI (chemical shift imaging) proton spectroscopy.

Materials and Methods

Eleven patients with primary brain tumors undergoing cranial radiation therapy (RT) were included. 2D‐CSI MRS was performed before, during, and after the course of RT with the following parameters: TE/TR 144/1500 ms, field of view (FOV) 24, thickness 10 mm, matrix 16 × 16. The metabolic ratios choline/creatine (Cho/Cr), N‐acetylaspartate (NAA)/Cr, and NAA/Cho in normal brain tissue were calculated.

Results

NAA/Cr and Cho/Cr were significantly decreased at week 3 during RT and at 1 month and 6 months after RT compared to values prior to RT (P < 0.01). The NAA/Cr ratio decreased by ?0.19 ± 0.05 (mean ± standard error [SE]) at week 3 of RT, ?0.14 ± 0.06 at the last week of RT, ?0.14 ± 0.05 at 1 month after RT, and ?0.30 ± 0.08 at 6 months after RT compared to the pre‐RT value of 1.43 ± 0.04. The Cho/Cr ratio decreased by ?0.27 ± 0.05 at week 3 of RT, ?0.11 ± 0.05 at the last week of RT, ?0.26 ± 0.05 at 1 month after RT and ?0.25 ± 0.07 at 6 months after RT from the pre‐RT value of 1.29 ± 0.03. Changes in Cho/Cr were correlated with the interaction of the radiation dose and dose‐volume at week 3 of RT, during the last week of RT (P < 0.005), and at 1 month after RT (P = 0.017).

Conclusion

The results of this study suggest that MRS can detect early metabolic changes in normal irradiated brain tissue. J. Magn. Reson. Imaging 2009;29:291–297. © 2009 Wiley‐Liss, Inc.

     

Impact of cerebrospinal fluid contamination on brain metabolites evaluation with 1H‐MR spectroscopy: A single voxel study of the cerebellar vermis in patients with degenerative ataxias

Purpose

To investigate the impact of cerebrospinal fluid (CSF) contamination on metabolite evaluation in the superior cerebellar vermis with single‐voxel ¹H‐MRS in normal subjects and patients with degenerative ataxias.

Materials and Methods

Twenty‐nine healthy volunteers and 38 patients with degenerative ataxias and cerebellar atrophy were examined on a 1.5 Tesla scanner. Proton spectra of a volume of interest placed in the superior vermis were acquired using a four TE PRESS technique. We calculated N‐acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, and NAA/Cho ratios, T₂ relaxation times and concentrations of the same metabolites using the external phantom method. Finally, concentrations were corrected taking into account the proportion of nervous tissue and CSF, that was determined as Volume Fraction (VF).

Results

In healthy subjects, a significant difference was observed between metabolite concentrations with and without correction for VF. As compared to controls, patients with ataxias showed significantly reduced NAA/Cr and NAA concentrations, while only corrected Cr concentration was significantly increased. The latter showed an inverse correlation with VF.

Conclusion

CSF contamination has a not negligible effect on the estimation of brain metabolites. The increase of Cr concentration in patients with cerebellar atrophy presumably reflects the substitutive gliosis which takes place along with loss of neurons. J. Magn. Reson. Imaging 2009;30:11–17. © 2009 Wiley‐Liss, Inc.     

Quantification of vertebral bone marrow fat content using 3 Tesla MR spectroscopy: reproducibility, vertebral variation, and applications in osteoporosis

Purpose:

To determine the reproducibility of proton MR spectroscopy (¹H‐MRS) for assessing vertebral bone marrow adiposity at 3 Tesla (T); to evaluate variation of marrow adiposity at different vertebral levels; and to demonstrate the feasibility of using ¹H‐MRS at 3T for evaluating marrow adiposity in subjects with low bone density.

Materials and Methods:

Single voxel MRS was acquired at vertebral body L1 to L4 at 3T in 51 postmenopausal females including healthy controls (n = 13) and patients with osteoporosis/osteopenia (n = 38). Marrow fat contents were compared between vertebral levels and between groups using analysis of variance (ANOVA). Six subjects were scanned twice to evaluate technique reproducibility.

Results:

The average coefficient of variation of vertebral marrow fat content quantification was 1.7%. Marrow fat content significantly increased from L1 to L4. The average fat content was significantly elevated in patients with osteoporosis/osteopenia compared with controls, adjusted for age and body mass index (P < 0.05).

Conclusion:

In vivo MRS at high field strength provides reliable measurement of marrow adiposity with excellent reproducibility and can be a valuable tool for providing complementary information on bone quality and potentially also fracture risk. J. Magn. Reson. Imaging 2011;33:974–979. © 2011 Wiley‐Liss, Inc.     

Hepatic fat quantification using chemical shift MR imaging and MR spectroscopy in the presence of hepatic iron deposition: validation in phantoms and in patients with chronic liver disease

Purpose:

To compare the accuracy of four chemical shift magnetic resonance imaging (MRI) (CS‐MRI) analysis methods and MR spectroscopy (MRS) with and without T2‐correction in fat quantification in the presence of excess iron.

Materials and Methods:

CS‐MRI with six opposed‐ and in‐phase acquisitions and MRS with five‐echo acquisitions (TEs of 20, 30, 40, 50, 60 msec) were performed at 1.5 T on phantoms containing various fat fractions (FFs), on phantoms containing various iron concentrations, and in 18 patients with chronic liver disease. For CS‐MRI, FFs were estimated with the dual‐echo method, with two T2*‐correction methods (triple‐ and multiecho), and with multiinterference methods that corrected for both T2* and spectral interference effects. For MRS, FF was estimated without T2‐correction (single‐echo MRS) and with T2‐correction (multiecho MRS).

Results:

In the phantoms, T2*‐ or T2‐correction methods for CS‐MRI and MRS provided unbiased estimations of FFs (mean bias, ?1.1% to 0.5%) regardless of iron concentration, whereas the dual‐echo method (?5.5% to ?8.4%) and single‐echo MRS (12.1% to 37.3%) resulted in large biases in FFs. In patients, the FFs estimated with triple‐echo (R = 0.98), multiecho (R = 0.99), and multiinterference (R = 0.99) methods had stronger correlations with multiecho MRS FFs than with the dual‐echo method (R = 0.86; P ≤ 0.011). The FFs estimated with multiinterference method showed the closest agreement with multiecho MRS FFs (the 95% limit‐of‐agreement, ?0.2 ± 1.1).

Conclusion:

T2*‐ or T2‐correction methods are effective in correcting the confounding effects of iron, enabling an accurate fat quantification throughout a wide range of iron concentrations. Spectral modeling of fat may further improve the accuracy of CS‐MRI in fat quantification. J. Magn. Reson. Imaging 2011;33:1390–1398. © 2011 Wiley‐Liss, Inc.