Central nervous system aspergillosis: magnetic resonance imaging, diffusion-weighted imaging, and magnetic resonance spectroscopy features

Aspergillus infection is invasive in nature in the immunosuppressed population and disseminates throughout the body, with the brain being a common site. Conventional magnetic resonance imaging (MRI) combined with diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) play a life-saving role in the early diagnosis and treatment monitoring of this potentially fatal infection. We present MRI, DWI, and MRS findings of a case of central nervous system aspergillosis with treatment follow-up.     

Correlation of spectroscopy and magnetization transfer imaging in the evaluation of demyelinating lesions and normal appearing white matter in multiple sclerosis

Magnetization transfer imaging (MT) and localized proton spectroscopy (¹H-MRS) were utilized in the evaluation of lesioins (high signal abnormalities on T₂-weighted images) and normal-appearing white matter (NAWM) in multiple sclerosis (MI). Eleven patients with a clinical diagnosis of MS were independently evaluated with both ¹H-MRS and MT. The magnetization transfer ratio (MTR) of lesions was compared with the relative concentration of Kacetyl-aspartate (NAA) and a composite peak at 2.1 to 2.6 ppm termed “marker peaks”. The MTR of white matter lesions in the MS patients was markedly decreased (6–34%; normal ≈?42%), and correlated well with increase in the marker peaks region (0.94–3.89). There was no correlation between the relative concentration of NAA and MTR. Increased resonance peaks in the 2.1 to 2.6 ppm range and marked decreases in MTR may be a relatively specific indicators of demyelination.     

Sturge-Weber syndrome: diffusion magnetic resonance imaging and proton magnetic resonance spectroscopy findings

We report on the diffusion magnetic resonance imaging (MRI) and proton MR spectroscopy findings of a 26-year-old female patient with Sturge-Weber syndrome. Echo-planar trace diffusion MRI revealed mildly high signal intensity changes at parieto-occipital lobes on b = 1000 s/mm² images, suggesting restricted diffusion. On corresponding apparent diffusion coefficient maps, those areas had moderately high signal intensity and high apparent diffusion coefficient values (around 0.9×10(-3) mm²/s) compared with the contralateral symmetrical normal side of the brain (0.776×10(-3) mm²/s). This finding was consistent with increased motion of water molecules (disintegration of the neural tissue) in these regions. Proton MR spectroscopy revealed decreased N-acetyl aspartate and increased choline peaks, indicating disintegration of neural tissue associated with neuronal loss as well.     

Magnetic resonance spectroscopy features of normal-appearing white matter in patients with acute brucellosis

We aimed to evaluate whether the subtle metabolic cerebral changes are present in normal-appearing white matter on conventional MRI, in patients with acute brucellosis, by using MR spectroscopy (MRS). Sixteen patients with acute brucellosis and 13 healthy control subjects were investigated with conventional MRI and single-voxel MRS. Voxels were placed in normal-appearing parietal white matter (NAPWM). N-Acetyl aspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from NAPWM. However, the Cho/Cr ratios were significantly higher in patients with acute brucellosis compared to controls (p=0.01). MRS revealed metabolic changes in normal-appearing white matter of patients with brucellosis. Brucellosis may cause subtle cerebral alterations, which may only be discernible with MRS. Increased Cho/Cr ratio possibly represents an initial phase of inflammation and/or demyelination process of brucellosis.     

Enhanced gray and white matter contrast of phase susceptibility-weighted images in ultra-high-field magnetic resonance imaging

PURPOSE: To evaluate if magnetic susceptibility sensitive phase postprocessed images can be used to enhance the inherent brain/gray white matter contrast in gradient echo (GE) images at 8-Tesla (T) magnetic resonance (MR). MATERIALS AND METHODS: Phase and magnitude images of high-resolution GE MR 8-T images were created. Comparisons were made between the magnitude, the product of the magnitude and phase, and pure phase images. RESULTS: The pure phase images significantly improved the contrast between the gray and white matter structures. In general, the higher the iron content or subvoxel field inhomogeneities, the higher was the contrast, and the greater were the resultant phase shifts. The phase images best demonstrated anatomy that was not apparent on the standard magnitude images. CONCLUSION: Phase imaging can significantly improve the demonstration of the internal anatomical brain structures over standard magnitude GE imaging techniques at high field.     

腹膜透析患者脑白质病变的初步研究

目的 评估腹膜透析患者脑白质病变的患病率及严重程度.方法 选择无明确脑血管疾病病史的38例腹膜透析患者及38例没有肾脏疾病的对照组行头颅常规MR扫描.2名有丰富经验的放射科医师在不知道临床资料的情况下进行独立阅片,按照Manolio量表分别对脑白质病变、脑沟增宽程度、脑室大小进行半定量分级(脑白质病变和脑萎缩的严重程度分为0～9分),2组评分比较采用非参数秩和检验.结果 2组患者年龄和性别差异均无统计学意义(P=0.639,P=0.818).腹膜透析组与对照组的脑白质病变评分(1.78±0.74 vs 1.13±0.41)、脑沟增宽程度(2.05±0.61 vs 1.45±0.60)和脑室大小评分(2.05±0.66 vs 1.37±0.54)的差异均有统计学意义(P＜0.001).结论 脑白质病变和脑萎缩在腹膜透析患者中患病率和严重程度显著高于对照组.     

Magnetization transfer ratio in early period of Parkinson disease

RATIONALE AND OBJECTIVES: The aim of this study is to determine the role of magnetization transfer ratio (MTR) in the early period of Parkinson disease (PD). MATERIALS AND METHODS: Clinically diagnosed 33 patients with PD in the first year of diagnosis, and 30 healthy volunteers were assessed. Magnetic resonance imaging (MRI) was performed without and with magnetization transfer (MT) imaging. Signal intensity measurements were obtained from 15 anatomic regions (substantia nigra pars compacta [SNPC], substantia nigra pars reticulate [SNPR], red nucleus, dentate nucleus, cerebellum, pons, globus pallidus, putamen, caudate nucleus, thalamus, internal capsule posterior horn, forceps major, forceps minor, and genu and splenium of corpus callosum) and MTR was calculated. Comparisons of the findings between each anatomic location of the patients with PD and normal subjects were performed. RESULTS: Most prominent decrease of MTR was found in SNPC (p < 0.001). A significant decrease of MTR was also found in the SNPR (p = 0.006), red nucleus (p = 0.037), and pons (p = 0.046). The other regions lack significance. CONCLUSION: MTR analysis is a useful technique for initial PD assessment. Even in the first year of diagnosis, significant reduction of MTR is found in substantia nigra, red nucleus, and pons compared with that of the control group.     

Concentrations and magnetization transfer ratios of metabolites in gray and white matter.

The concentrations and magnetization transfer ratios (MTRs) in gray matter (GM) and white matter (WM) of N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (Ins), and glutamate plus glutamine (Glx) were investigated using magnetic resonance spectroscopic imaging (MRSI). The macromolecule (MM) baseline was studied separately using a metabolite-nulling inversion. Three data sets were collected from a point-resolved spectroscopy (PRESS)-selected volume (TE/TR = 30/3000 ms) of human frontal lobe in vivo: one with MT pulses applied, one with an inversion pulse to null small metabolites, and one with no inversion or MT pulses. The MM signal, which was analyzed by integrating the metabolite-nulled spectrum between 0 and 3 ppm, was estimated to be 38% higher in GM than in WM. MM subtraction decreased the signal-to-noise ratio (SNR) and also decreased the reliability of LCModel quantification of most metabolites, but may have improved the accuracy of quantification of Glx. Glx and Cr were both found to correlate strongly with the GM volume fraction of the voxels. Cr showed the highest MTR, but the other metabolites also showed some attenuation of signal when the MT pulses were applied. The MTRs did not correlate with the GM volume fraction, which implies that the local environment of metabolites does not differ markedly between GM and WM.     

卒中后抑郁患者小脑磁共振波谱成像改变的临床研究

目的 应用氢质子磁共振波谱成像(1H-MRS)技术,探讨卒中后抑郁(PSD)患者小脑代谢的改变及其与抑郁严重程度的关系.方法 以卒中患者作为研究对象,回顾性收集人口学、个人疾病史和生活方式的数据,对40例卒中患者及20例健康志愿者进行自评抑郁量表(SDS)和汉密尔顿抑郁量表(HAMD)评分.根据评分结果,将卒中患者分为卒中后抑郁(PSD)组和卒中后无抑郁(CONT)组.对PSD组、CONT组和正常对照(NORM)组进行T1WI、T2WI、DWI及1H-MRS检查,评估脑梗死体积和脑白质病变部位及严重程度,测定小脑半球N-乙酰天冬氨酸(NAA)/肌酸(Cr)、胆碱复合物(Cho)/Cr、Cho/NAA比值,并分析卒中后小脑代谢改变与HAMD评分间的关系.结果 CONT组双侧小脑NAA/Cr、Cho/Cr、Cho/NAA比值与NORM组比较差异均无统计学意义(P＞0.05).与NORM组和CONT组比较,PSD组病灶对侧小脑Cho/Cr、Cho/NAA比值均较高(P＜0.05),病灶同侧小脑Cho/Cr、Cho/NAA比值差异无统计学意义(P＞0.05),而双侧小脑NAA/Cr比值差异无统计学意义(P＞0.05).PSD组家庭APGAR问卷评分、ARWMC总分、发病14d时NIHSS评分、病灶对侧小脑Cho/Cr和Cho/NAA比值与CONT组比较差异有统计学意义(P＜0.05).多重线性回归分析显示,病灶对侧小脑Cho/Cr、Cho/NAA比值与HAMD评分具有相关性(P＜0.05).结论 小脑可能参与了卒中后抑郁的发生.     

Characterization of white matter alterations in phenylketonuria by magnetic resonance relaxometry and diffusion tensor imaging.

A multimodal MR study including relaxometry, diffusion tensor imaging (DTI), and MR spectroscopy was performed on patients with classical phenylketonuria (PKU) and matched controls, to improve our understanding of white matter (WM) lesions. Relaxometry yields information on myelin loss or malformation and may substantiate results from DTI attributed to myelin changes. Relaxometry was used to determine four brain compartments in normal-appearing brain tissue (NABT) and in lesions: water in myelin bilayers (myelin water, MW), water in gray matter (GM), water in WM, and water with long relaxation times (cerebrospinal fluid [CSF]-like signals). DTI yielded apparent diffusion coefficients (ADCs) and fractional anisotropies. MW and WM content were reduced in NABT and in lesions of PKU patients, while CSF-like signals were significantly increased. ADC values were reduced in PKU lesions, but also in the corpus callosum. Diffusion anisotropy was reduced in lesions because of a stronger decrease in the longitudinal than in the transverse diffusion. WM content and CSF-like components in lesions correlated with anisotropy and ADC. ADC values in lesions and in the corpus callosum correlated negatively with blood and brain phenylalanine (Phe) concentrations. Intramyelinic edema combined with vacuolization is a likely cause of the WM alterations. Correlations between diffusivity and Phe concentrations confirm vulnerability of WM to high Phe concentrations.     

Incidental high-intensity foci in white matter on T2-weighted magnetic resonance imaging

Summary The clinical significance of high-intensity foci in the white matter on magnetic resonance images of the brain was studied in 351 adults. The foci frequently occurred in the corona radiata and centrum semiovale. The frequency and extent of the foci were closely related to age and to a previous history of cerebrovascular disease. Patients without such a history but with risk factors for cerebrovascular disease tended to have these foci more frequently than those without risk factors.     

脑白质纤维成像的基础研究和临床应用新进展

脑白质纤维成像是目前唯一能直观显示脑白质纤维束的非侵入性检查方法，基础是弥散加权威像，基本原理为脑白质水分子弥散的各向异性。应用最多的方法主要有线性延展法和椭球体表示法。在临床方面的应用主要集中在监测脑白质的发育、成熟及生理性老化；观察脑肿瘤与白质纤维束的关系；显示急性中风、炎症、脑外伤病变引起的脑白质改变；显示精神分裂症病入局部神经联合的中断。     

Magnetization transfer effect on human brain metabolites and macromolecules.

A pulse sequence was implemented to observe the magnetization transfer (MT) effect on metabolites, water, and macromolecules in human frontal lobes in vivo at 1.5 Tesla. Signals were compared following the application of three hard pulses of 0.745 muT amplitude, applied at frequency offsets of either 2500 Hz or 30 kHz, preceding a conventional point-resolved spectroscopy (PRESS)-localized acquisition with an echo time (TE) of 30 ms and repetition time (TR) of 3 s. This gave an MT effect on water in vivo of 46%, while direct saturation by the MT pulses at 2.5 kHz offset was confirmed to be under 4% for all metabolites. We observed significant MT saturation in vivo for N-acetylated compounds, choline (Cho), myo-inositol, and lactate (Lac); a trend of an effect on glutamate + glutamine (Glx); and the typically observed effect on creatine (Cr). No significant MT effect was seen on the macromolecule signal, which was observed using metabolite nulling.     

Pattern recognition in magnetic resonance imaging of white matter disorders inchildren and young adults

Summary Magnetic resonance imaging (MRI) is considered to be a highly sensitive modality for visualizing white matter abnormalities. Estimations of its specificity are far less positive. However, diagnostic specificity depends upon both the inherent qualities of MRI and on the quality of image interpretation. Systematic and detailed analysis of many image elements, and substantial prior experience improve the quality of image interpretation and thus improve diagnostic specificity. The present study has been set up to develop a pattern recognition system which combines sensitivity and specificity, systematic analysis of image elements and prior experience. This pattern recognition is based on the data of 277 patients with white matter disorders referred for MRI. The information was stored in a data base and computer analyzed. Twenty-two MRI patterns were discerned in as many disease categories. The frequency of occurrence of each MRI abnormality was assessed per disease category to establish the pattern of abnormalities characteristic for each separate disease category. The pattern recognition program was also written so that: (a) when fed data about MRI abnormalities observed in a new case, the computer produces a differential diagnosis with probabilities and 95% confidence intervals for each differential diagnosis; (b) specific data on the MRI findings of new cases could be added to the data base to improve the experience and accuracy of the program. This program for pattern recognition of abnormalities in the MR images of white matter disorders enhances the specificity of image interpretation and provides a wonderful aid for teaching purposes.     

Magnetisation transfer ratio is low in normal-appearing cerebral white matter in patients with normal pressure hydrocephalus

We measured the magnetisation transfer ratios (MTR) of normal-appearing rostral (PR) and caudal (PC) periventricular white matter, the genu (CG) and the splenium (CS) of the corpus callosum and the thalamus (TH) in 12 patients with normal-pressure hydrocephalus (NPH) and compared them with 16 healthy control subjects. We found a significantly lower MTR in the NPH group than in the normal group for PR, PC, CG, and CS but not for TH. MT measurements give additional information which cannot be gained by conventional MRI, suggesting that NPH is associated with diffuse white matter damage, even in normal-appearing cerebral white matter. Received: 2 July 1999/Accepted: 13 July 1999     

Magnetization exchange observed in human skeletal muscle by non‐water‐suppressed proton magnetic resonance spectroscopy

Many metabolites in the proton magnetic resonance spectrum undergo magnetization exchange with water, such as those in the downfield region (6.0–8.5 ppm) and the upfield peaks of creatine, which can be measured to reveal additional information about the molecular environment. In addition, these resonances are attenuated by conventional water suppression techniques complicating detection and quantification. To characterize these metabolites in human skeletal muscle in vivo at 3 T, metabolite cycled non‐water‐suppressed spectroscopy was used to conduct a water inversion transfer experiment in both the soleus and tibialis anterior muscles. Resulting median exchange‐independent T₁ times for the creatine methylene resonances were 1.26 and 1.15 s, and for the methyl resonances were 1.57 and 1.74 s, for soleus and tibialis anterior muscles, respectively. Magnetization transfer rates from water to the creatine methylene resonances were 0.56 and 0.28 s^?1, and for the methyl resonances were 0.39 and 0.30 s^?1, with the soleus exhibiting faster transfer rates for both resonances, allowing speculation about possible influences of either muscle fibre orientation or muscle composition on the magnetization transfer process. These water magnetization transfer rates observed without water suppression are in good agreement with earlier reports that used either postexcitation water suppression in rats, or short CHESS sequences in human brain and skeletal muscle. Magn Reson Med, 70:916–924, 2013. © 2012 Wiley Periodicals, Inc.     

大脑胶质瘤病磁共振成像结合磁共振波谱成像的诊断价值

目的：探讨磁共振成像（MRI）结合磁共振波谱成像（MRS）对大脑胶质瘤病的诊断价值。方法对15例经活体组织检查或手术病理证实的大脑胶质瘤病患者的临床表现及MRI平扫、增强,MRS影像学资料进行回顾性分析。MRI常规行T1WI、T2WI及FLAIR序列,采用时间飞跃法（TOF）的磁共振血管成像（MRA）,T1WI增强扫描。氢质子MRS采用单体素STEAM序列,并分析N-乙酰天门冬氨酸（NAA）、肌酸（Cr）、胆碱复合物（Cho）等物质峰值改变。结果所有病例均侵犯2个或2个以上脑叶,以颞叶、枕叶、胼胝体、基底节和丘脑等部位侵犯受累常见。病变区T1WI呈低或等低信号、T2WI呈高或混杂高信号、FLAIR上为高信号,未见明显坏死、钙化,受累区域脑组织肿胀,占位效应轻。注射钆喷酸葡胺增强扫描示10例无明显强化、3例斑片状强化、1例结节状强化、1例线状轻度强化。病变区域MRS表现为不同程度NAA降低,NAA/Cr比值降低;Cho上升,Cho/Cr和Cho/NAA的比值上升。结论 MRI结合MRS对大脑胶质瘤病的诊断及鉴别诊断具有临床价值,是目前诊断大脑胶质瘤病的首选影像学方法。     

Region and tissue differences of metabolites in normally aged brain using multislice 1H magnetic resonance spectroscopic imaging.

Quantitative measurements of regional and tissue specific concentrations of brain metabolites were measured in elderly subjects using multislice proton magnetic resonance spectroscopic imaging ((1)H MRSI). Selective k-space extrapolation and an inversion-recovery sequence were used to minimize lipid contamination and linear regression was used to account for partial volume problems. The technique was applied to measure the concentrations of N-acetyl aspartate (NAA), and creatine (Cr)- and choline (Cho)-containing compounds in cortical gray and white matter, and white matter lesions of the frontal and the parietal lobe in 40 normal elderly subjects (22 females and 18 males, 56-89 years old, mean age 74 +/- 8). NAA was about 15% lower in cortical gray matter and 23% lower in white matter lesions when compared to normal white matter. Cr was 11% higher in cortical gray matter than in white matter, and also about 15% higher in the parietal cortex than in the frontal cortex. Cho was 28% lower in cortical gray matter than in white matter. Furthermore, NAA and Cr changes correlated with age. In conclusion, regional and tissue differences of brain metabolites must be considered in addition to age-related changes when interpreting (1)H MRSI data.