Histological and 1H magnetic resonance spectroscopic imaging analysis of quinolinic acid-induced damage to the rat striatum

NAA has been described as a neuron-specific compound. NAA levels as determined by magnetic resonance spectroscopic imaging (MRSI) have been used to determine degree of neuronal loss in several neurological diseases, but there has been limited work to document the accuracy and reliability of this technique. This study addresses this question quantitatively with histological analysis of cell viability and tissue shrinkage in quinolinic acid (QA)-induced damage of the rat striatum compared with ¹H MRSI measurement of N-acetyl aspartate (NAA) as a noninvasive measure of neuronal loss. Both 'H MRSI and histology detect damage to the lesioned striatum; however, there are differences in the degree of damage as assessed by the two methods. Although partial-volume effects and tissue shrinkage may decrease the sensitivity of MR to such damage, the sparing of axons by QA may be another important factor in the differences in assessment. These results indicate that further studies of NAA metabolism and its distribution within neurons are warranted.     

Volumetric proton spectroscopic imaging of mild traumatic brain injury

BACKGROUND AND PURPOSE: Poor clinical outcomes without notable neuroimaging findings after mild traumatic brain injury (MTBI) suggest diffuse tissue damage and altered metabolism not observable with conventional MR imaging and CT. In this study, MTBI-associated metabolic changes were assessed over the entire brain by using volumetric proton MR spectroscopic imaging (MRSI) and the findings related to injury and outcome assessments. METHODS: Fourteen subjects with mild closed head injury (Glasgow Coma Scale [GCS] scores of 13-15) underwent structural MR imaging and proton MRSI at 1.5 T within 1 month of injury. Distributions of N-acetylaspartate (NAA), total creatine (Cr), and total choline (Cho) were mapped over a wide region of the brain, and metabolite ratios were calculated for 25 regions without MR imaging abnormalities. Results were compared with data from 13 control subjects. RESULTS: Significant changes (P <.05) were found for some, but not all, brain regions for the average values from all MTBI subjects, with reduced NAA/Cr, increased Cho/Cr, and reduced NAA/Cho. Global NAA/Cho obtained from the sum of all sampled regions in two subjects was significantly reduced. Metabolite ratios were not significantly correlated with GCS score at admission or Glasgow Outcome Scale (GOS) score at 6 months after injury, although they were weakly correlated with GOS score at discharge. CONCLUSION: These results show evidence of widespread metabolic changes following MTBI in regions that appear normal on diagnostic MR images. Although the association with injury assessment and outcome is weak, this preliminary study demonstrates the applicability of volumetric proton MRSI for evaluating diffuse injury associated with MTBI.     

Gray matter N-acetyl aspartate deficits in secondary progressive but not relapsing-remitting multiple sclerosis

BACKGROUND AND PURPOSE: Spectroscopic examination of multiple sclerosis (MS) patients has revealed abnormally low N-acetyl-aspartate (NAA) signal intensity, even in brain tissue that appears normal on high-resolution structural MR images but has yielded inconclusive evidence to distinguish the well-documented clinical differences between MS subtypes. This study used proton MR spectroscopic imaging (MRSI) and high-resolution MR imaging to characterize metabolite profiles in normal-appearing brain tissue of relapsing-remitting multiple sclerosis (RRMS) and secondary progressive (SP) MS. METHODS: Volumetric spiral MRSI was used together with high-resolution MR imaging to derive absolute measures of metabolite concentrations separately in normal-appearing supratentorial cerebral gray matter and white matter in five RRMS patients, five SPMS patients, and nine age-matched controls. Structural MR images were segmented into compartments of gray matter, white matter, CSF, and lesions, and metabolite signals per unit of tissue volume were calculated for gray matter and white matter separately. RESULTS: Only the SPMS group had significantly lower NAA concentrations in normal-appearing gray matter compared with concentrations in controls. NAA in normal-appearing white matter was equally reduced in RRMS and SPMS patients. The functional relevance of this brain metabolite measure was suggested by the observed but statistically nonsignificant correlation between higher disability scores on the Expanded Disability Status Scale and lower gray matter NAA concentrations. CONCLUSION: The otherwise occult abnormality in supratentorial gray matter in SPMS but not RRMS may explain the more severe physical and cognitive impairments afflicting patients with SPMS that do not correlate well with visible lesion burden.     

Proton MR spectroscopic imaging depicts diffuse axonal injury in children with traumatic brain injury

BACKGROUND AND PURPOSE: Diffuse axonal injury (DAI) after traumatic brain injury (TBI) is important in patient assessment and prognosis, yet they are underestimated with conventional imaging techniques. We used MR spectroscopic imaging (MRSI) to detect DAI and determine whether metabolite ratios are accurate in predicting long-term outcomes and to examine regional differences in injury between children with TBI and control subjects. METHODS: Forty children with TBI underwent transverse proton MRSI through the level of the corpus callosum within 1-16 days after injury. T2-weighted, fluid-attenuated inversion recovery, and susceptibility-weighted MR imaging was used to identify voxels as normal-appearing or as nonhemorrhagic or hemorrhagic injury. Neurologic outcome was evaluated at 6-12 months after injury. Metabolite ratios for total (all voxels), normal-appearing, and hemorrhagic brain were compared and used in a logistic regression model to predict long-term outcome. Total and regional metabolite ratios were compared with control data. RESULTS: A significant decrease in N-acetylaspartate (NAA)/creatine (Cr) and increase in choline (Cho)/Cr (evidence of DAI) was observed in normal-appearing (P < .05) and visibly injured (hemorrhagic) brain (P < .001) compared with controls. In normal-appearing brain NAA/Cr decreased more in patients with poor outcomes (1.32 +/- 0.54) than in those with good outcomes (1.61 +/- 0.50, P = .01) or control subjects (1.86 +/- 0.1, P = .00). In visibly injured brains, ratios were similarly altered in all patients. In predicting outcomes, ratios from normal-appearing and visibly-injured brain were 85% and 67% accurate, respectively. CONCLUSION: MRSI can depict injury in brain that appears normal on imaging and is useful for predicting long-term outcomes.     

Acute disseminated encephalomyelitis and multiple sclerosis: magnetic resonance imaging differentiation

The study was undertaken to compare the MR imaging features of acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) in a country with a high prevalence of ADEM. Magnetic resonance scans from 33 patients diagnosed clinically with MS (14 patients) or ADEM (19 patients) were reviewed concurrently by two radiologists blinded to the clinical diagnosis. The size, site, morphology and pattern of brain and spinal cord involvement were recorded and the MR imaging diagnosis was compared with the clinical diagnosis. The MR imaging findings matched with the clinical diagnosis in 11 of 14 patients with MS (sensitivity = 78.6%), and with the clinical diagnosis in 15 of 18 patients with ADEM (sensitivity = 78.9%). Three patients had non-specific findings and in a further three patients discordant imaging features were present. One patient with imaging features typical of Balo's concentric sclerosis was diagnosed clinically as suffering from ADEM. In a country with a high prevalence of ADEM, the majority of patients with ADEM and MS can be differentiated on MR imaging.     

Term neonate prognoses after perinatal asphyxia: contributions of MR imaging, MR spectroscopy, relaxation times, and apparent diffusion coefficients

PURPOSE: To retrospectively evaluate magnetic resonance (MR) imaging, hydrogen 1 (1H) MR spectroscopy, apparent diffusion coefficient (ADC), T1, and T2 measurements for prediction of late neurologic outcome in term neonates after severe perinatal asphyxia. MATERIALS AND METHODS: This study was approved by the local ethics committee. Informed consent from parents was not required. Thirty term neonates (12 boys, 18 girls; age range, 2-12 days) with severe hypoxic-ischemic encephalopathy were examined during the first 12 days of life with conventional and diffusion-weighted cerebral MR imaging, 1H MR spectroscopy with absolute quantification, and T1 and T2 measurements. Quantitative 1H MR spectroscopy, T1, and T2 data were acquired on one 10-mm slab positioned at the level of the basal ganglia. The neonates were assigned to one of two groups according to their late (>12-month follow-up) neurologic outcome: those with an unfavorable outcome-that is, death or severe disability-and those with a favorable outcome. Clinical data, MR signal intensity abnormalities, ADCs, 1H MR spectroscopy findings, and relaxation times were compared by using Chi2 testing and analysis of variance to individualize the prognostic indicators. RESULTS: The unfavorable (n=16) and favorable (n=14) outcome groups were similar in terms of clinical data (ie, Apgar scores, visceral hypoxic injuries), visualization of brain edema on MR images, and T1 and T2 relaxation times. Late unfavorable neurologic outcome was associated with a mixed pattern of cortical and basal ganglia signal intensity abnormalities on MR images (13 babies with unfavorable vs three babies with favorable outcomes, P=.001) and with decreased absolute N-acetylaspartate (NAA) and choline concentrations in all brain structures, especially the basal ganglia (mean NAA concentration: 2.72 mmol/L in unfavorable outcome group vs 4.66 mmol/L in favorable outcome group, P<5x10(-9)), as measured with MR spectroscopy. In the basal ganglia, an NAA concentration lower than 4 mmol/L indicated an unfavorable individual prognosis with 94% sensitivity and 93% specificity. Significantly reduced ADCs also were noted in the unfavorable outcome group, but only during the first 6 days of life. CONCLUSION: Conventional MR imaging findings, spectroscopically measured absolute NAA and choline concentrations, and ADCs are complementary tools for predicting the individual outcomes of severely asphyxiated term neonates.     

Comparison of T(1) and T(2) metabolite relaxation times in glioma and normal brain at 3T

PURPOSE: To measure T(1) and T(2) relaxation times of metabolites in glioma patients at 3T and to investigate how these values influence the observed metabolite levels. MATERIALS AND METHODS: A total of 23 patients with gliomas and 10 volunteers were studied with single-voxel two-dimensional (2D) J-resolved point-resolved spectral selection (PRESS) using a 3T MR scanner. Voxels were chosen in normal appearing white matter (WM) and in regions of tumor. The T(1) and T(2) of choline containing compounds (Cho), creatine (Cr), and N-acetyl aspartate (NAA) were estimated. RESULTS: Metabolite T(1) relaxation values in gliomas were not significantly different from values in normal WM. The T(2) of Cho and Cr were statistically significantly longer for grade 4 gliomas than for normal WM but the T(2) of NAA was similar. These differences were large enough to impact the corrections of metabolite levels for relaxation times with tumor grade in terms of metabolite ratios (P < 0.001). CONCLUSION: The differential increase in T(2) for Cho and Cr relative to NAA means that the ratios of Cho/NAA and Cr/NAA are higher in tumor at longer echo times (TEs) relative to values in normal appearing brain. Having this information may be useful in defining the acquisition parameters for optimizing contrast between tumor and normal tissue in MR spectroscopic imaging (MRSI) data, in which limited time is available and only one TE can be used.     

MR-Perfusions- und spektroskopische Bildgebung bei WHO-Grad-II-Astrozytomen

BACKGROUND: This study evaluates whether MR perfusion imaging and spectroscopic imaging (MRSI) can depict anaplastic areas in WHO grade II astrocytomas, whether these areas are co-localized, and whether the prognosis can be better predicted. MATERIAL AND METHODS: Fifteen patients (nine female, six male, aged 42+/-14 years) with WHO grade II astrocytomas but without preceding radio- or chemotherapy were examined every 3 months with MR perfusion imaging and MRSI (mean follow-up 18 months). Using a region of interest analysis, the regional relative cerebral blood volume (rrCBV) and blood flow (rrCBF) were measured in tumor tissue. In the same areas, choline/creatine (Cho/Cr) and choline/N-acetyl-aspartate (Cho/NAA) ratios were quantified. RESULTS: During follow-up, nine patients had stable disease. In six patients, the tumor showed progression and contrast-enhancement. The progressing tumors had already had higher perfusion (rrCBF 2.1+/-1.4; rrCBV 1.9+/-1.1) parameters than the stable astrocytomas (rrCBF 1.2+/-0.6, p=0.01; rrCBV 1.4+/-0.8, p=0.05) at first examination. However, the Cho/NAA and Cho/Cr ratios only tended to be higher than in stable astrocytomas (Cho/NAA 2.4+/-1.0 vs. 2.0+/-1.5, p=0.23; Cho/Cr 1.7+/-0.6 vs. 1.4+/-0.5, p=0.06). In all six progressing tumors, areas of maximum perfusion and maximum Cho/NAA and Cho/Cr ratio were co-localized. During follow-up, contrast-enhancement was observed in these areas. CONCLUSIONS: MR perfusion imaging can depict anaplastic areas in WHO grade II astrocytomas earlier than conventional MRI and thus enables a better prediction of prognosis.     

Correlation of cerebral metabolites with functional outcome in experimental primate stroke using in vivo 1H-magnetic resonance spectroscopy

BACKGROUND AND PURPOSE: Ensuring the translatability of primate stroke models is critical for preclinical testing of cerebroprotective strategies, and such models would benefit from further characterization of the experimental ischemic tissue. Our purpose was to examine the cerebral metabolic response to stroke in baboons with MR spectroscopy and to correlate metabolite levels with functional neurologic outcomes. METHODS: Seven baboons underwent 1 hour of middle cerebral artery occlusion. At 3 and 10 days, each animal was imaged with traditional MR imaging and multivoxel proton (1)H-MR spectroscopy, and a neurologic examination was performed. Spectra obtained from the infarcted hemisphere of each animal were compared with the contralateral hemisphere, and metabolite levels were correlated with neurologic outcome scores. RESULTS: Spectra obtained at 3 days postischemia revealed prominent lactate (LAC) resonances and attenuated N-acetylaspartate (NAA) peaks in infarcted hemispheres. Ten-day spectra showed persistence of these findings in animals with large strokes (>30% of the hemisphere), with partial normalization of the spectra in animals with small strokes (<30% of the hemisphere). Mean area under the curve from LAC spectra had a negative correlation with functional outcome by 2 different scoring systems (r(2) = 0.72 and 0.73), whereas NAA showed a positive correlation (r(2) = 0.79 and 0.62). CONCLUSIONS: The metabolic alterations observed in our primate model of reperfused ischemia by (1)H-MR spectroscopy recapitulate those seen in clinical stroke. Furthermore, correlations between LAC and NAA peaks with functional outcome further suggest that MR spectroscopy may play a role in outcome prediction following cerebral infarction in higher primates.     

急性播散性脑脊髓炎的脑部MRI表现

目的　描述急性播散性脑脊髓炎的脑部MRI表现 ,探讨MRI对该病的诊断价值以及在评价疗效中的作用。方法　符合临床诊断标准的急性播散性脑脊髓炎患者 9例 ,男 8例 ,女 1例 ,年龄 9～ 47岁。 6例发病前有病毒感染或疫苗接种史。全部 9例行头部MRI检查 ,7例行MRI复查。结果　病变多发且分布不对称 ,9例大脑白质受累 ,6例同时累及丘脑 ,4例可见“垂直征” ,病变呈大小不等的片状或点状异常信号 ,6例可见异常对比增强 ,7例复查见异常信号缩小且数目减少。结论急性播散性脑脊髓炎的MRI脑部表现颇具特征性 ,结合病史及单时相病程可作出早期诊断 ,MRI随访是评价疗效的重要手段。MRI显示丘脑受累是鉴别本病与多发性硬化的主要依据。     

Spectroscopic imaging of the pilocarpine model of human epilepsy suggests that early NAA reduction predicts epilepsy.

Reduced hippocampal N-acetyl aspartate (NAA) is commonly observed in patients with advanced, chronic temporal lobe epilepsy (TLE). It is unclear, however, whether an NAA deficit is also present during the clinically quiescent latent period that characterizes early TLE. This question has important implications for the use of MR spectroscopic imaging (MRSI) in the early identification of patients at risk for TLE. To determine whether NAA is diminished during the latent period, we obtained high-resolution (1)H spectroscopic imaging during the latent period of the rat pilocarpine model of human TLE. We used actively detuneable surface reception and volume transmission coils to enhance sensitivity and a semiautomated voxel shifting method to accurately position voxels within the hippocampi. During the latent period, 2 and 7 d following pilocarpine treatment, hippocampal NAA was significantly reduced by 27.5 +/- 6.9% (P < 0.001) and 17.3 +/- 6.9% (P < 0.001) at 2 and 7 d, respectively. Quantitative estimates of neuronal loss at 7 d (2.3 +/- 7.7% reduction; P = 0.58, not significant) demonstrate that the NAA deficit is not due to neuron loss and therefore likely represents metabolic impairment of hippocampal neurons during the latent phase. Therefore, spectroscopic imaging provides an early marker for metabolic dysfunction in this model of TLE.     

In vivo quantitative proton MRSI study of brain development from childhood to adolescence

PURPOSE: To quantify regional variations in metabolite levels in the developing brain using quantitative proton MR spectroscopic imaging (MRSI). MATERIALS and METHODS: Fifteen healthy subjects three to 19 years old were examined by in vivo multislice proton MRSI. Concentrations of N-acetyl aspartate (NAA), total choline (Cho), total creatine (Cr), and peak area ratios were determined in selected frontal and parietal gray and white matter regions, basal ganglia, and thalamus. RESULTS: In cortical gray matter regions, the ratio of NAA/Cho increased to a maximum at 10 years and decreased thereafter (P = 0.010). In contrast, in white matter, average ratios NAA/Cho increased linearly with age (P = 0.045). In individual brain regions, age-related changes in NAA/Cho were found in the putamen (P = 0.044). No significant age-related changes in NAA, Cho, Cr, or other metabolite ratios could be determined. CONCLUSION: Consistent with recent studies using other structural and functional neuroimaging techniques, our data suggest that small but significant changes occur in regional cerebral metabolism during childhood and adolescence. Non-linear age related changes of NAA/Cho in frontal and parietal areas, resembling previously reported age related changes in rates of glucose utilization and cortical volumes, may be associated with dendritic and synaptic development and regression. Linear age-related changes of NAA/Cho in white matter are also in agreement with age-related increases in white matter volumes, and may reflect progressive increases in axonal diameter and myelination.     

Analysis of the spatial characteristics of metabolic abnormalities in newly diagnosed glioma patients

PURPOSE: To evaluate the role of 3D MR spectroscopic imaging (MRSI) as a tool for characterizing heterogeneity within a lesion in glioma patients. MATERIALS AND METHODS: Forty-nine patients with newly diagnosed glioma were studied with 3D water-suppressed proton (1-H) MRSI. Signal intensities from choline (Cho), creatine (Cr), N-acytel aspartate (NAA), and lactate/lipid (LL) were estimated from the spectra. Regions of interest (ROIs) corresponding to the metabolic abnormalities were defined and compared with the anatomic lesions. RESULTS: This study showed that the tumor burden measured with either the volumes of the metabolic abnormalities or the metabolic levels in the most abnormal voxels was correlated with the degree of malignancy of the tumor. The volumes of elevated Cho and decreased NAA were useful for distinguishing low-grade from high-grade lesions. The volume of abnormal LL was correlated with the existence of necrosis and with the volume of contrast-enhancing lesions in high-grade lesions. The differences in the volume of abnormal LL were also statistically significant between patients in each grade. CONCLUSION: These 3D-MRSI data provide important additional information to conventional MRI for evaluating and characterizing gliomas.     

Changes in fiber integrity, diffusivity, and metabolism of the pyramidal tract adjacent to gliomas: a quantitative diffusion tensor fiber tracking and MR spectroscopic imaging study

BACKGROUND AND PURPOSE: The underlying changes in the neuronal connectivity adjacent to brain tumors cannot always be depicted by conventional MR imaging. The hypothesis of this study was that preoperative sensorimotor deficits are associated with impairment in pyramidal fiber bundles. Hence, we investigated the potential of combined quantitative diffusion tensor (DT) fiber tracking and MR spectroscopic imaging (MRSI) to determine changes in the pyramidal tract adjacent to gliomas. MATERIALS AND METHODS: Quantitative DT fiber tracking and proton MRSI were performed in 20 patients with gliomas with WHO grades II-IV. Eight patients experienced preoperative sensorimotor deficits. Mean diffusivity (MD), fractional anisotropy (FA), and number of fibers per voxel (FpV) were calculated for the pyramidal tract of the ipsilateral and contralateral hemisphere. Metabolite concentrations for choline-containing compounds (Cho), creatine (Cr), and N-acetylaspartate (NAA) were computed, using LCModel, for all voxels located at the pyramidal tracts. RESULTS: For the whole pyramidal tract, quantitative DT fiber tracking resulted in significantly lower FpV and FA values (P < .001), but not MD values, for the ipsilateral hemisphere. For the section of the fiber bundle closest to the lesion, we found significantly decreased FpV and FA (P < .001) and increased MD (P = .002). MRSI showed, for the same volumes of interest, significantly decreased NAA (P = .001), increased Cho (P = .034) and Cho/NAA (P = .001) for the ipsilateral pyramidal tract. In patients suffering sensorimotor deficits, we found significantly lower FA (P = .022) and higher MD values (P = .026) and a strongly negative correlation between FA and MD (R = -0.710, P = .024) but no correlation in patients without deficits (R = 0.078, ns). CONCLUSION: Quantitative DTI was able to show significant differences in diffusivity of the pyramidal tract in patients with sensorimotor deficits in relation to patients without them. The additional use of proton MRSI may be helpful to discern whether these diffusivity changes in fiber tracts are caused by tumor infiltration or peritumoral edema.     

Analysis of volume MRI and MR spectroscopic imaging data for the evaluation of patients with brain tumors.

The combination of volumetric MRI and multivoxel localized MR spectroscopic imaging (MRSI) data provides the potential for quantifying variations in tissue morphology and function. These techniques have numerous applications for the evaluation of neurological diseases. While state-of-the-art whole-body MR scanners are able to acquire both types of data, there have been relatively few reports which have presented clinical applications of the technology. One of the reasons for this has been the need to develop software for reconstruction and reliable interpretation of 3D imaging and spectral data. In this article, we describe the strategy developed for quantitative analysis of combined MRI and MRSI examinations from patients with brain tumors and evaluate the key components of this procedure using both simulations and empirical data from phantoms, normal volunteers, and patients. Important factors are the use of volume or interleaved multislice anatomic images as a reference, the reconstruction and correction of the spectral data for frequency, phase, and baseline distortions and consideration of the characteristics of the coil, RF pulses used for spatial selection, and phase encoding procedures. These studies show that the metabolic parameters most critical for distinguishing tumor from normal and necrotic tissue were relative levels of choline and NAA. Levels of creatine and lactate were found to be variable, both in terms of their spatial distribution within individual lesions and between different patients.     

Measurements of diagnostic examination performance using quantitative apparent diffusion coefficient and proton MR spectroscopic imaging in the preoperative evaluation of tumor grade in cerebral gliomas

Purpose

Tumor grading is very important both in treatment decision and evaluation of prognosis. While tissue samples are obtained as part of most therapeutic approaches, factors that may result in inaccurate grading due to sampling error (namely, heterogeneity in tissue sampling, as well as tumor-grade heterogeneity within the same tumor specimen), have led to a desire to use imaging better to ascertain tumor grade. The purpose in our study was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), area under the curve (AUC), and accuracy of diffusion-weighted MR imaging (DWI), proton MR spectroscopic imaging (MRSI) or both in grading primary cerebral gliomas.

Materials and methods

We performed conventional MR imaging (MR), DWI, and MRSI in 74 patients with newly diagnosed brain gliomas: 59 patients had histologically verified high-grade gliomas: 37 glioblastomas multiform (GBM) and 22 anaplastic astrocytomas (AA), and 15 patients had low-grade gliomas. Apparent diffusion coefficient (ADC) values of tumor and peritumoral edema, and ADC ratios (ADC in tumor or peritumoral edema to ADC of contralateral white matter, as well as ADC in tumor to ADC in peritumoral edema) were determined from three regions of interest. The average of the mean, maximum, and minimum for ADC variables was calculated for each patient. The metabolite ratios of Cho/Cr and Cho/NAA at intermediate TE were assessed from spectral maps in the solid portion of tumor, peritumoral edema and contralateral normal-appearing white matter. Tumor grade determined with the two methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic (ROC) curve analysis were performed to determine optimum thresholds for tumor grading. Measures of diagnostic examination performance, such as sensitivity, specificity, PPV, NPV, AUC, and accuracy for identifying high-grade gliomas were also calculated.

Results

Statistical analysis demonstrated a threshold minimum ADC tumor value of 1.07 to provide sensitivity, specificity, PPV, and NPV of 79.7%, 60.0%, 88.7%, and 42.9% respectively, in determining high-grade gliomas. Threshold values of 1.35 and 1.78 for peritumoral Cho/Cr and Cho/NAA metabolite ratios resulted in sensitivity, specificity, PPV, and NPV of 83.3%, 85.1%, 41.7%, 97.6%, and 100%, 57.4%, 23.1% and 100% respectively for determining high-grade gliomas. Significant differences were noted in the ADC tumor values and ratios, peritumoral Cho/Cr and Cho/NAA metabolite ratios, and tumoral Cho/NAA ratio between low- and high-grade gliomas. The combination of mean ADC tumor value, maximum ADC tumor ratio, peritumoral Cho/Cr and Cho/NAA metabolite ratios resulted in sensitivity, specificity, PPV, and NPV of 91.5%, 100%, 100% and 60% respectively.

Conclusion

Combining DWI and MRSI increases the accuracy of preoperative imaging in the determination of glioma grade. MRSI had superior diagnostic performance in predicting glioma grade compared with DWI alone. The predictive values are helpful in the clinical decision-making process to evaluate the histologic grade of tumors, and provide a means of guiding treatment.     

Delayed MR imaging changes in acute disseminated encephalomyelitis.

BACKGROUND AND PURPOSE: White matter lesions on MR images obtained from patients with acute disseminated encephalomyelitis (ADEM) have been reported to appear shortly after symptom onset, and their resolution has been claimed to parallel recovery. To elucidate the temporal evolution of these lesions and to associate the changes on MR images to the patients' clinical condition, we performed serial MR imaging on patients with ADEM. METHODS: Several consecutive T2-weighted and fluid-attenuated inversion recovery scans were obtained from four previously healthy adult patients with ADEM within the first days after the onset of symptoms and again during the recovery period. MR imaging was done first on a weekly to biweekly basis and later at 1- to 2-month intervals for up to 8 months. RESULTS: MR scans of three of these patients did not show any specific abnormalities until several weeks after the onset of the disease. As the lesions later appeared, their number increased during the recovery period. CONCLUSION: MR imaging performed during the first days after the onset of the disease may not reveal any pathologic findings. The appearance of the ADEM-associated MR imaging changes may be associated with recovery rather than decline. It remains to be studied whether the new MR imaging techniques reveal the lesions associated with ADEM faster than the conventional T2-weighted imaging.     

MR spectroscopy of normative premature newborns

Purpose

To establish normative metabolite ratios throughout the newborn brain using three‐dimensional (3D) MR spectroscopic imaging (MRSI).

Materials and Methods

MRI and MRSI have been valuable tools for assessing normal and abnormal neuronal maturation for newborns. In this study, we performed whole brain 3D MRSI in addition to comprehensive anatomic and other functional imaging methods to examine maturation. Fifty‐five newborn subjects (28.4 ± 2.6 weeks postconception age at birth, 34.1 ± 3.1 weeks postconception age at scan, 32 males and 23 females) had high quality MRSI studies (104 exams) and normal neurodevelopmental outcome (neuromotor score = 0, mental development index score > 85) at age 12 months.

Results

The NAA to Cho ratio increased significantly with age for all regions. Lac to NAA ratio decreased significantly with age in the regions of thalamus, basal ganglia, cortical spinal tract, and parietal white matter, and showed a decreasing trend in the other regions.

Conclusion

Brain metabolites can be obtained through in vivo 3D MRSI and used to monitor newborn brain maturation. J. Magn. Reson. Imaging 2011;33:306–311. © 2011 Wiley‐Liss, Inc.     

急性胰腺炎累及肾周间隙的MRI研究

目的:研究急性胰腺炎(AP)向肾周间隙扩展的MRI表现,以及肾周间隙受累与AP严重程度的关系.方法:回顾性分析119例急性胰腺炎患者的MRI表现.每例AP患者在MRI上的严重程度用MRI严重程度指数(MRSI)进行分级,MRS10～2分为轻症,3～6分中症,7～10分为重症.在MRI上观察肾周间隙有无受累,并对受累程度分级:无受累记为0分,肾周间隙内条索状高信号记为1分,积液记为2分.分析肾周间隙受累程度与MRSI的相关性.结果:119例急性胰腺炎中,轻症急性胰腺炎例48例,中症59例,重症急性胰腺炎12例.73.95%(88/119)的AP患者在MRI上有肾周间隙受累,表现为肾周间隙内条索状、斑片状或大片状异常信号.其中轻症急性胰腺炎肾周间隙受累率47.92%(23/48),中症为91.52%(54/59),重症为91.67%(11/12).肾周间隙MRI评分为1分时在轻症为41.67%(20/48),中症及重症为19.72%(14/71)(χ~2=7.249,P=0.007);肾周间隙MRI评分为2分者轻症和中症共为42.06%(45/107),而在重症为75.00%(9/12)(χ~2=4.724,P=0.030).在MRI上肾周间隙受累的严重程度与MRSI成正相关(r=0.714,P=0.000).结论:在MRI上急性胰腺炎肾周间隙受累率高于文献报道的CT上的受累率,肾周间隙受累反映了AP的严重程度.