Minimal hepatic encephalopathy in children with liver cirrhosis: diffusion-weighted MR imaging and proton MR spectroscopy of the brain

Introduction

The aim of this work was to detect minimal hepatic encephalopathy (minHE) in children with diffusion-weighted MR imaging (DWI) and proton magnetic resonance spectroscopy (¹H-MRS) of the brain.

Methods

Prospective study conducted upon 30 consecutive children (age range 6–16 years, 21 boys and 9 girls) with liver cirrhosis and 15 age- and sex-matched healthy control children. Patients with minHE (n?=?17) and with no minHE (n?=?13) groups and control group underwent DWI, ¹H-MRS, and neuropsychological tests (NPTs). The glutamate or glutamine (Glx), myoinositol (mI), choline (Cho), and creatine (Cr) at the right ganglionic region were determined at ¹H-MRS. The apparent diffusion coefficient (ADC) value and metabolic ratios of Glx/Cr, mI/Cr, and Cho/Cr were calculated.

Results

There was elevated ADC value and Glx/Cr and decreased mI/CI and Ch/Cr in patients with minHE compared to no minHE and control group. There was significant difference between minHE, no minHE, and control group in the ADC value (P?=?0.001 for all groups), GLx/Cr (P?=?0.001 for all groups), mI/Cr (P?=?0.004, 0.001, and 0.001, respectively), Ch/Cr (P?=?0.001 for all groups), and full-scale IQ of NPT (P?=?0.001, 0.001, and 0.143, respectively). The NPT of minHE had negative correlation with ADC value (r?=??0.872, P?=?0.001) and GLx/Cr (r?=??0.812, P?=?0.001) and positive correlation with mI/Cr (r?=?0.732, P?=?0.001).

Conclusion

DWI and ¹H-MRS are imaging modalities that can detect minHE in children with liver cirrhosis and correlate well with parameters of NPT.     

1H MR spectroscopy of the brain: absolute quantification of metabolites

Hydrogen 1 (1H) magnetic resonance (MR) spectroscopy enables noninvasive in vivo quantification of metabolite concentrations in the brain. Currently, metabolite concentrations are most often presented as ratios (eg, relative to creatine) rather than as absolute concentrations. Despite the success of this approach, it has recently been suggested that relative quantification may introduce substantial errors and can lead to misinterpretation of spectral data and to erroneous metabolite values. The present review discusses relevant methods to obtain absolute metabolite concentrations with a clinical MR system by using single-voxel spectroscopy or chemical shift imaging. Important methodological aspects in an absolute quantification strategy are addressed, including radiofrequency coil properties, calibration procedures, spectral fitting methods, cerebrospinal fluid content correction, macromolecule suppression, and spectral editing. Techniques to obtain absolute concentrations are now available and can be successfully applied in clinical practice. Although the present review is focused on 1H MR spectroscopy of the brain, a large part of the methodology described can be applied to other tissues as well.     

Monitoring of irradiated brain metastases using MR perfusion imaging and 1H MR spectroscopy

PURPOSE. In follow-up examinations of irradiated brain metastases conventional contrast-enhanced morphological MR imaging is often unable to distinguish between transient radiation effects, radionecrosis,and tumor recurrence. To evaluate changes of relative cerebral blood flow (rCBF) in irradiated brain metastases arterial spin-labeling techniques (ASL) were applied and compared to the outcome of (1)H MR spectroscopy and spectroscopic imaging ((1)H MRS, SI). PATIENTS AND METHODS. In 2 patients follow-up examinations of irradiated brain metastases were performed on a 1.5-T tomograph (average single dose: 20 Gy/80% isodose). Relative CBF values of gray matter (GM), white matter (WM),and metastases (Met) were measured by means of the ASL techniques ITS-FAIR and Q2TIPS. (1)H MRS was performed with PRESS 1500/135. RESULTS. In both patients with initially hyperperfused metastases (Met/GM >1) the reduction of rCBF after stereotactic radiosurgery indicated response to treatment--even if the contrast-enhancing region increased--while increasing rCBF values indicated tumor progression. The findings were confirmed by (1)H MRS, SI and subsequent follow-up. CONCLUSION. The ASL techniques ITS-FAIR and Q2TIPS are able to monitor changes of rCBF in irradiated brain metastases. The two cases imply a possible role for ASL-MR perfusion imaging and (1)H MR spectroscopy in differentiating radiation effects from tumor progression.     

(1)H MR spectroscopy of human brain tumours: a practical approach

Magnetic resonance spectroscopy (MRS) is proposed in addition to magnetic resonance imaging (MRI) to help in the characterization of brain tumours by detecting metabolic alterations that may be indicative of the tumour class. MRS can be routinely performed on clinical magnets, within a reasonable acquisition time and if performed under adequate conditions, MRS is reproducible and thus can be used for longitudinal follow-up of treatment. MRS can also be performed in clinical practice to guide the neurosurgeon into the most aggressive part of the lesions or to avoid unnecessary surgery, which may furthermore decrease the risk of surgical morbidity.     

(1)H MR spectroscopy in pediatrics

Spectral appearance and concentrations of the most prominent metabolites are affected by brain development. This knowledge is essential for the detection of pathological changes in pediatric patients. This paper discusses specific conditions of MR spectroscopic examination of children and the effects of age on MR spectra quality and quantitation of the studied metabolites. Clinical examples show several diseases that are reflected in changes in (1)H MR spectra due to pathological alterations in the biochemical pathways of the observed metabolites. Attention is given to the main metabolites such as N-acetylaspartate, creatine/phosphocreatine, cholines, lactate, inositol, etc.     

Metabolic disorders of the brain in chronic hepatic encephalopathy detected with H-1 MR spectroscopy.

Proton magnetic resonance (MR) spectroscopy of the brain was performed in 11 patients with chronic hepatic encephalopathy (CHE), and the results were compared with those of patients with liver disease but without CHE; clinical control subjects with diabetes, uremia, or cortical atrophy; and healthy subjects. The technique of water-suppressed stimulated-echo hydrogen-1 MR spectroscopy for detection of cerebral glutamate, glutamine, glucose, N-acetylaspartate, choline metabolites, (phospho)creatine, and myo-inositol is described. Specific changes in the brain of CHE patients included the anticipated elevation in cerebral glutamine levels (P less than or equal to .0001), a 23% reduction in choline metabolite levels (P less than or equal to .0001), and a more than 50% reduction in cerebral myo-inositol levels (P less than or equal to .0001). In four of the 15 patients with liver disease but without clinical CHE, a significant reduction in the myo-inositol level was detected, and in two of these patients an elevation in the glutamine concentration was also observed. These findings indicate a role for image-guided H-1 MR spectroscopy in the diagnosis and monitoring of both overt and preclinical CHE.     

MRS定量测量急性缺氧缺血脑损伤猪脑代谢物研究

目的 评价外标准法MRS结合LCModel软件绝对定量测量急性缺氧缺血脑损伤猪脑N-乙酰天冬氨酸(NAA)、肌酸(Cr)和乳酸(Lac)浓度变化的价值.方法 8头7日龄健康猪麻醉后未作任何处理(正常组),麻醉清醒后1 d制成缺氧缺血性脑病(HIE)模型(HIE组),先后与内含已知浓度物质的外标准模型一起行1H-MRS检查,数据采集完毕后用LCModel软件定量分析测量NAA、Cr、Lac浓度,HIE前、后猪脑代谢物NAA、Cr、Lac间比较采用多元方差分析,并对2头HIE猪缺氧缺血0、2 h脑代谢物动态变化情况作初步观察.结果 l头猪因麻醉过深死亡而剔除,最后统计数据为7头.小猪急性缺氧缺血前脑NAA、Cr、Lac分别为(6.86±0.49)、(4.65±0.73)、0.00 mmol/kg,缺氧缺血后即刻脑NAA、Cr、Lac分别为(5.73±0.88)、(4.40±0.80)、(0.43±0.39)mmol/kg.急性缺氧缺血后即刻猪脑NAA浓度下降,差异有统计学意义(F=8.608,P=0.013);Cr浓度有所下降,但差异无统计学意义(F=0.379,P=0.550);Lac浓度升高,差异有统计学意义(F=8.600,P=0.013).初步观察脑代谢物动态变化见HIE后即刻出现Lac峰,2 h Lac峰下降.结论 外标准法MRS结合LCModel定量分析软件能方便准确地定量测量脑内代谢物,NAA与Lac浓度的改变均能敏感地反映急性缺氧缺血脑损伤早期改变,且以NAA浓度的改变稍敏感.     

(1)H MR spectroscopy of skeletal muscle, liver and bone marrow

Proton magnetic resonance spectroscopy ((1)H MRS) offers interesting metabolic information even from organs outside the brain. In the first part, applications in skeletal muscle for determination of intramyocellular lipids (IMCL), which are involved in the pathogenesis of insulin resistance, are described. Peculiarities of spectral pattern are discussed and studies for short-term regulation of IMCL, as dietary intervention, exercise and fasting are presented. The second part deals with quantification of small amounts of lipids in the liver (hepatic lipids, HL), which is also of increasing interest in the field of diabetes research. Recommendations for correct assessment of spectra in this "moving organ" are given and the importance of HL is described by examples of a cohort at increased risk for type 2 diabetes. Regulation of HL is described on the basis of a few studies. The third part concentrates on spectral characterization of bone marrow. Peripheral bone marrow of adults consists mainly of fat, while central marrow regions in the pelvis, spinal column and breast bone (and the peripheral bone marrow of children as well) contribute to blood formation and show a variable composition of adipocytes (fat cells), interstitial fluid and water containing precursor cells for erythrocytes, leucocytes and thrombocytes. Adapted (1)H spectroscopic techniques allow a semi-quantitative analysis of bone marrow composition.     

Systemic lupus erythematosus: brain MR imaging and single-voxel hydrogen 1 MR spectroscopy

PURPOSE: To evaluate the usefulness of magnetic resonance (MR) imaging and hydrogen 1 MR spectroscopy in the detection of brain involvement in patients with systemic lupus erythematosus (SLE) with or without neuropsychiatric symptoms. MATERIALS AND METHODS: Twenty-six patients who had SLE with (n = 17) or without (n = 9) neuropsychiatric symptoms were examined at MR imaging and (1)H MR spectroscopy. The voxel was placed in the basal ganglia and peritrigonal white matter. Eight healthy volunteers were included. RESULTS: Five of nine patients with major neuropsychiatric symptoms and one of eight patients with minor neuropsychiatric symptoms had abnormal MR imaging findings. (1)H MR spectroscopy showed a significantly decreased N:-acetylaspartate-creatine (Cr) ratio in the basal ganglia and an increased choline-Cr ratio in the peritrigonal white matter in patients with major symptoms compared with those with minor symptoms, those without symptoms, and healthy control subjects. Among patients with major symptoms, there was no difference in metabolite ratios between those with and those without abnormal MR imaging findings. Among patients with normal MR imaging findings, abnormal spectral changes were observed only in those with major neuropsychiatric symptoms. In patients without neuropsychiatric symptoms, results of (1)H MR spectroscopy and MR imaging were normal. CONCLUSION: In patients with SLE, (1)H MR spectroscopic findings seem to reflect the cerebral metabolic disturbance related to the severity of the neuropsychiatric symptoms and are not related to the presence of abnormal MR imaging findings.     

(1)H MR spectroscopy of inflammation, infection and ischemia of the brain

Different pathologic patterns in multiple sclerosis (MS) are reflected by alterations of metabolites in (1)H MR spectroscopy of the brain. Elevated choline (Cho), lactate (Lac), lipids and macromolecules are reliable markers for acute demyelination regardless of the clinical entity (also in acute disseminated encephalomyelitis). N-acetyl-aspartate (NAA) is a suitable marker for neuronal integrity. It is reduced in acute MS lesions and in normal appearing white matter, even distant to acute and chronic-lesions. Recovery from reduced NAA levels to subnormal values during remyelination, and varying time courses of NAA in normal appearing white matter during relapsing remitting disease indicate the value of this spectroscopic marker for monitoring activity and recovery. Inositol (Ins) is increased in chronic MS lesions being a marker for astrocytic gliosis. In viral disease, Cho and Ins are always increased, whereas a reduction of NAA mostly reflects an advanced or a detoriated clinical state. In bacterial brain abscesses, numerous amino acids, lipids and Lac can be elevated. In ischemia, especially the Lac/NAA in comparison with perfusion and diffusion weighted imaging seems to be a new measure for areas of metabolic need, and may help to better characterise the penumbra of the stroke and the final infarct size.     

Hypoxia-ischemic encephalopathy in full-term neonate: correlation proton MR spectroscopy with MR imaging

INTRODUCTION: To evaluate 1H Magnetic Resonance Spectroscopy (1HMRS) in the diagnosis of hypoxia-ischemic encephalopathy (HIE) of full-term neonates correlated with Magnetic Resonance Imaging (MRI). MATERIALS AND METHODS: Thirty-eight cases of full-term neonates diagnosed as HIE clinically were selected to perform MRI and 1HMRS examination. The ages ranged from 7 to 17 days, with median age of 8.2 days. In which, 26 cases were followed up and/or MRI reexamined at 6 months of age or later. Eight healthy neonates, with no evidence of birth asphyxia, also underwent 1HMRS for comparison. SE sequences were used for routine MR examination; point resolved spectroscopy sequence was required for 1HMRS. The metabolites in the spectra includes: N-acetylaspartate (NAA), choline compounds (CHO), creatine compounds (CR), myo-inositol (MI), lactate (LAC), glutamate and glutamine (Glu-Gln). RESULTS: The peaks of NAA were fall in two cases; the peaks of LAC, which were elevated, appeared as typical double-peaks appearance in 26 cases; the peaks of Glu-Gln, which were also elevated, appeared as zigzag appearance in nine cases. The peaks of CR were decreased in 11 cases, while those of MI were increased in seven cases. Mild type of lesions was present on MRI in 12 cases whose LAC/CR ratio lower than 0.5; mild and moderate types of lesions were present in 15 cases whose LAC/CR ratio between 0.5 and 1.5. Whereas, nine cases of severe lesions and two cases of moderate lesions were present on MRI in 11 cases whose LAC/CR ratio greater than 1.5. Twenty-six of 38 cases were followed up and/or MRI reexamined after 6 months, in which, sequelae were present in 12 cases. Among them, eight cases of sequelae in nine cases whose LAC/CR ratio greater than 1.5 were present (account for 88.89%). CONCLUSION: 1HMRS plays an important role to diagnose and predict outcome of HIE.     

Hematopoietic reconstitution after bone marrow transplantation: Assessment with MR imaging and H-1 localized spectroscopy

Magnetic resonance (MR) studies were performed in 14 patients as early as possible (21–110 days) after bone marrow transplantation (BMT). MR characteristics of lumbar vertebral bone marrow were studied with T1-weighted spin-echo imaging, water- and fatselective imaging with a frequency-selective excitation technique, and point-resolved spatially localized proton spectroscopy. Signals from water and fat protons and their T1 and T2 values were analyzed. Water proton signal intensity correlated well with cellularity within bone marrow, as determined with parallel iliac crest biopsies. The fraction of signal from water in red bone marrow of patients with allogeneic transplants from siblings (four cases) was significantly higher than in four patients with autologous transplants. The latter showed very low cellularity in the period of about 4 weeks after BMT because of the cytotoxic pretreatment of the bone marrow. The MR results in six patients with allogeneic transplants from unrelated donors ranged widely, depending on the complications after BMT. Analysis of data obtained with the different techniques showed that water- and fat-selective MR imaging and spectroscopic methods are useful for noninvasive monitoring of hematopoietic reconstitution after BMT.     

肝移植术后血管和胆系并发症的MRI诊断价值

目的探讨磁共振血管造影(MRA)和MR胰胆管成像(MRCP)对诊断肝移植术后血管及胆管并发症的价值。方法7例原位肝移植术后患者均用磁共振(MR)快速自旋回波(TSE)序列及快速小角度激发梯度回波(FLASH)序列常规扫描、MRCP、钆喷替酸葡甲胺(Gd-DTPA)动态增强3DMRA检查，分析各序列图像特点。结果术后正常2例，主要表现少量腹水，积血和轻度淋巴结增大。血管并发症4例：肝动脉过长迂曲1例，肝动脉供体端瘤样轻度扩张2例；门静脉轻度狭窄2例，位于吻合口；肝静脉末梢分支杵状扩张2例。胆系并发症3例：吻合口胆管狭窄3例；在吻合口以外的胆管狭窄2例，位于肝门及肝内；胆总管在吻合口扭曲2例；胆囊管残端黏液囊肿2例；胆漏1例。结论MRA和胆管造影作为1种非侵袭性影像检查方法，可准确、快速诊断肝移植术后出现的血管和胆管并发症，对指导临床诊断及治疗具有重要意义。     

MR imaging and in vivo proton spectroscopy of the brain in neonates with hypoxic ischemic encephalopathy

INTRODUCTION: A number of studies have suggested the potential utility of in vivo proton MR spectroscopy for the evaluation of brain injury in the asphyxiated neonates. We present our initial experience with in vivo proton MR spectroscopy in neonates who were diagnosed as having hypoxic injury on clinical examination and the severity of the insult was graded using Sarnat staging. METHODS AND MATERIAL: MR imaging and in vivo proton MR spectroscopy was performed in 16 neonates with hypoxic ischemic encephalopathy (HIE) to correlate the imaging and metabolite abnormality with clinical severity of the condition at the time of insult and with outcome at 2 months of age. The ratios of different metabolites were calculated as observed on MR spectroscopy from an 8 ml voxel that included thalami, basal ganglia and part of the ventricular system using spin echo technique with an echo time of 135 ms. RESULTS AND DISCUSSION: The results of the spectroscopy were compared with imaging abnormalities and Sarnat's clinical staging of HIE. MR Imaging abnormalities included basal ganglia, thalamic and periventricular hemorrhage and periventricular hyperintensities and were noticed in 8/16 neonates with different stages of HIE. Maximum imaging abnormalities were noted in stage II (6/9) followed by stage III (1/2) and stage I (1/5), respectively. The alpha-Glx resonance at 3.76 ppm was seen in 14/16, Glycine at 3.56 ppm (Gly) was seen in 10/16 and Lactate (L) at 1.33 ppm was observed in 4/16 neonates with HIE. CONCLUSION: MR spectroscopy was more sensitive than imaging in detecting the insult due to HIE and increased concentration of alpha-Glx/Cr and Gly/Cr correlated better with severity of the HIE. The demonstration of L was associated with poor outcome.     

Subcortical ischemic vascular dementia: assessment with quantitative MR imaging and 1H MR spectroscopy

BACKGROUND AND PURPOSE: Subcortical ischemic vascular dementia is associated with cortical hypometabolism and hypoperfusion, and this reduced cortical metabolism or blood flow can be detected with functional imaging such as positron emission tomography. The aim of this study was to characterize, by means of MR imaging and 1H MR spectroscopy, the structural and metabolic brain changes that occur among patients with subcortical ischemic vascular dementia compared with those of elderly control volunteers and patients with Alzheimer's disease. METHODS: Patients with dementia and lacunes (n = 11), cognitive impairment and lacunes (n = 14), and dementia without lacunes (n = 18) and healthy age-matched control volunteers (n = 20) underwent MR imaging and 1H MR spectroscopy. 1H MR spectroscopy data were coanalyzed with coregistered segmented MR images to account for atrophy and tissue composition. RESULTS: Compared with healthy control volunteers, patients with dementia and lacunes had 11.74% lower N-acetylaspartate/creatine ratios (NAA/Cr) (P = .007) and 10.25% lower N-acetylaspartate measurements (NAA) in the cerebral cortex (P = .03). In white matter, patients with dementia and lacunes showed a 10.56% NAA/Cr reduction (P = .01) and a 12.64% NAA reduction (P = .04) compared with control subjects. NAA in the frontal cortex was negatively correlated with the volume of white matter signal hyperintensity among patients with cognitive impairment and lacunes (P = .002). Patients with dementia, but not patients with dementia and lacunes, showed a 10.33% NAA/Cr decrease (P = .02) in the hippocampus compared with healthy control volunteers. CONCLUSION: Patients with dementia and lacunes have reduced NAA and NAA/Cr in both cortical and white matter regions. Cortical changes may result from cortical ischemia/infarction, retrograde or trans-synaptic injury (or both) secondary to subcortical neuronal loss, or concurrent Alzheimer's pathologic abnormalities. Cortical derangement may contribute to dementia among patients with subcortical infarction.