Markov random field segmentation of brain MR images

We describe a fully-automatic three-dimensional (3-D)-segmentation technique for brain magnetic resonance (MR) images. By means of Markov random fields (MRF's) the segmentation algorithm captures three features that are of special importance for MR images, i.e., nonparametric distributions of tissue intensities, neighborhood correlations, and signal inhomogeneities. Detailed simulations and real MR images demonstrate the performance of the segmentation algorithm. In particular, the impact of noise, inhomogeneity, smoothing, and structure thickness are analyzed quantitatively. Even single-echo MR images are well classified into gray matter, white matter, cerebrospinal fluid, scalp-bone, and background. A simulated annealing and an iterated conditional modes implementation are presented.     

MRI evaluation of the brain in infantile neuronal ceroid-lipofuscinosis. Part 2: MRI findings in 21 patients

The purpose of this study was to demonstrate the course of infantile neuronal ceroid-lipofuscinosis with brain magnetic resonance imaging (MRI) in children aged 3 months to 11 years. Twenty-one patients and 46 neurologically normal controls of the same age were examined. The images were evaluated visually; then signal intensities were measured and related to those of references. MRI abnormalities were detectable before clinical symptoms. The radiologic picture of the brain varied with the duration of the disease. Pathognomonic MRI findings in the early stage of the disease were generalized cerebral atrophy, strong thalamic hypointensity to the white matter and to the basal ganglia, and thin periventricular high-signal rims from 13 months onward on T2-weighted images. In patients over 4 years old, cerebral atrophy was extreme, and the signal intensity of the entire white matter was higher than that of the gray matter, which is the reverse of normal. This study showed that the abnormalities seen on MRI progress rapidly during the first 4 years of life, then stabilize, in conformity with the clinical and histopathologic pictures of infantile neuronal ceroid-lipofuscinosis.     

Deficits in gray matter volume are present in schizophrenia but not bipolar disorder

Studies using magnetic resonance (MR) imaging have provided strong evidence that patients with schizophrenia as a group have structural brain abnormalities, including enlarged ventricles and sulci as well as smaller cortical gray matter volumes. This study was undertaken to investigate whether the brain abnormalities found in schizophrenia could be distinguished from those seen in bipolar disorder. The MR scans of 23 patients with schizophrenia were compared to those of 17 healthy community volunteers and 14 patients with bipolar disorder. Images were processed using computer-based image processing techniques to generate quantitative measures of cerebrospinal fluid (CSF), gray matter and white matter volumes. Compared to the community volunteers, the schizophrenia group had larger total CSF volumes while the bipolar group had larger ventricles. Smaller cortical gray matter volumes were found in the schizophrenia group, but not in the bipolar group. The schizophrenia group had regional deficits in gray matter volumes in comparison with both the community volunteers and the bipolar group. These findings suggest that the brain tissue abnormalities found in schizophrenia and bipolar disorder may be distinguishable using MR imaging.     

Neurochemical alterations in asymptomatic abstinent cocaine users: a proton magnetic resonance spectroscopy study

Cocaine can cause a variety of neuropsychiatric and neurobehavioral complications; however, it is uncertain whether cocaine causes persistent cerebral structural and neurochemical abnormalities in asymptomatic users. We studied 52 African-American men (26 human immunodeficiency virus-negative asymptomatic heavy cocaine users and 26 normal subjects). Ventricle-to-brain ratio (VBR) and white matter lesions (WML) were quantified on magnetic resonance imaging. N-acetyl-containing compounds (NA), total creatine, choline-containing compounds, myo-inositol, and glutamate + glutamine were measured with in vivo proton magnetic resonance spectroscopy, VBR and WML were not significantly different in the cocaine users compared to the normal controls. Elevated creatine (+7%; p = .05) and myo-inositol (+18%; p = .01) in the white matter were associated with cocaine use. NA, primarily a measure of N-acetyl aspartate and neuronal content, was normal. Normal NA suggest no neuronal loss or damage in the brain regions examined in these cocaine users. Therefore, we conclude that neurochemical abnormalities observed might result from alterations in nonneuronal brain tissue.     

Estimating NAA in cortical gray matter with applications for measuring changes due to aging

N-acetylaspartic acid (NAA), a prominent peak in the proton spectrum, is an amino acid thought to be present almost exclusively in neurons and their dendritic and axonal extensions. While 1H MRS studies are showing promise in identifying NAA deficits in different patient groups, unwanted lipid signal from subcutaneous fat surrounding the skull, and necessarily large voxels have limited investigators' ability to assess NAA in cortical gray matter. Here we report a technique developed to derive estimates of NAA signal from cortical gray matter. This approach uses an inversion recovery imaging pulse sequence with a long TE to suppress lipid signal from the scalp and information from concurrently obtained structural MR images to determine the CSF, white and gray matter composition of each spectroscopic voxel. A regression analysis is then used to estimate what NAA levels would be in "pure" white and gray matter voxels. This technique has been applied to demonstrate reduced NAA gray/white levels in the brains of five healthy older compared with five healthy younger women.     

Lipoprotein profile in canine pancreatitis induced with oleic acid

In the treatment of children with brain tumors, balancing the efficacy of treatment against commonly observed side effects is difficult because of a lack of quantitative measures of brain damage that can be correlated with the intensity of treatment. We quantitatively assessed volumes of brain parenchyma on magnetic resonance (MR) images using a hybrid combination of the Kohonen self-organizing map for segmentation and a multilayer backpropagation neural network for tissue classification. Initially, we analyzed the relationship between volumetric differences and radiologists' grading of atrophy in 80 subjects. This investigation revealed that brain parenchyma and white matter volumes significantly decreased as atrophy increased, whereas gray matter volumes had no relationship with atrophy. Next, we compared 37 medulloblastoma patients treated with surgery, irradiation, and chemotherapy to 19 patients treated with surgery and irradiation alone. This study demonstrated that, in these patients, chemotherapy had no significant effect on brain parenchyma, white matter, or gray matter volumes. We then investigated volumetric differences due to cranial irradiation in 15 medulloblastoma patients treated with surgery and radiation therapy, and compared these with a group of 15 age-matched patients with low-grade astrocytoma treated with surgery alone. With a minimum follow-up of one year after irradiation, all radiation-treated patients demonstrated significantly reduced white matter volumes, whereas gray matter volumes were relatively unchanged compared with those of age-matched patients treated with surgery alone. These results indicate that reductions in cerebral white matter: 1) are correlated significantly with atrophy; 2) are not related to chemotherapy; and 3) are correlated significantly with irradiation. This hybrid neural network analysis of subtle brain volume differences with magnetic resonance may constitute a direct measure of treatment-induced brain damage.     

Magnetic resonance in HTL-I associated myelopathy. Leukoencephalopathy and spinal cord atrophy

Cerebral white matter lesions and spinal cord atrophy have been frequently reported in patients with HTLV-I associated myelopathy (HAM). The exact frequency and the clinical relevance of these findings still remain to be elucidated. Twenty-nine patients with HAM were studied by magnetic resonance imaging of the brain and spine. Cerebral white matter lesions equal or over 3 mm in diameter were considered abnormal. The spinal cord size was evaluated using an index we have called "spinal cord index". The radiological findings were correlated to the clinical features of the myelopathy. Cerebral white matter lesions occurred in 52% of the patients, and spinal cord atrophy in 74%. There was no significant correlation between these abnormalities and the clinical features studied. These findings suggest that the resonance imaging is a useful method for detection of cerebral and spinal cord abnormalities in HAM patients. The absence of correlation between cerebral white matter lesions and either patient age or risk factors for cardiovascular disease suggests a possible association between the leukoencephalopathy and the infection.     

Measurement of brain activity with bolus administration of contrast agent and gradient-echo MR imaging

This study was performed to measure changes in cerebral blood volume (CBV) associated with visual activation by use of bolus administration of contrast agent and conventional, clinically configured magnetic resonance (MR) hardware and software. Fast gradient-recalled acquisition in the steady state technique was used to study five healthy subjects during visual activation and a control dark state. MR images were obtained every 2.048 seconds for 2 minutes. A bolus of gadopentetate dimeglumine was injected during visual stimulation and darkness. Cine images produced from the series of rapid images clearly depicted arterial, capillary, and venous phases. Analysis of serial concentration maps derived from the rapid images revealed expected differences between the relative CBV of gray matter and that of white matter, as well as significantly increased relative CBV in calcarine cortex during visual activation versus the control state (mean increase, 15.24%; range, 6.41%-27.78%; P < .05). These results confirm those reported in echo-planar imaging studies and demonstrate that brain function can be assessed with the bolus method by means of MR imaging hardware and software with conventional clinical configurations.     

Functional magnetic resonance imaging in macaque cortex

The ability to use fMRI in a monkey model would bridge the gap between the fMRI demonstration of cerebral activation in humans and the cumulative wealth of monkey data on the functional organization of the brain from single electrode mapping, radioisotope and histology studies. We report a new technique for fMRI in an awake co-operative rhesus macaque (Macaca mulatta) in a conventional clinical 1.5T MR scanner and present the first fMRI images from a macaque. Good resolution, signal-to-noise ratio and BOLD response (2.6-4.6%) have been achieved using the manufacturer's standard volume knee coil. T1 values of macaque gray and white matter (1490 ms, 1010 ms respectively) are higher than human brain, whereas T2 values are lower (55 ms, 48 ms respectively). An MR-compatible design for restraining the monkey is also described, along with a suitable EPI sequence for BOLD images, optimized for monkey T2, with voxel sizes from 29 to 61 microl, and MPRAGE sequence for anatomical studies with 0.8 mm isotropic resolution, optimized for monkey T1.     

Brain regional distribution pattern of metabolite signal intensities in young adults by proton magnetic resonance spectroscopic imaging

Proton magnetic resonance spectroscopy (1H-MRS) is evolving from single-volume localized acquisitions to multiple-volume acquisitions using magnetic resonance spectroscopic imaging (1H-MRSI). The normal regional patterns of 1H-MRSI-detectable metabolite signal intensities have yet to be established. We studied 13 healthy young adults with a multiple-section 1H-MRSI technique. The metabolite signals measured were N-acetylaspartate (NA), choline-containing compounds (CHO), creatine-phosphocreatine (CRE), and lactate. Ten neuroanatomic regions (nine bilateral) were identified in gray matter, white matter, and basal nuclei. Analysis of the data led to the following conclusions: (1) NA and CHO signals from centrum semiovale (CSO) can be used as a normalizing factor to reduce intersubject variability due to external causes; (2) in normal human brain, there is no left versus right asymmetry in the regions studied; (3) statistically significant patterns of signal distribution of NA, CHO, and CRE can be identified in normal human brain; and (4) CSO-normalized metabolite signal intensities and metabolite ratios complement each other for the detection of significant regional differences.     

The cognitive correlates of white matter abnormalities in normal aging: A quantitative review.

Cerebral white matter of asymptomatic people frequently exhibits circumscribed areas of hyperintensity on magnetic resonance (MR) images and hypodensity on computed tomography scans. However, behavioral implications of this phenomenon remain unclear. In this meta-analysis, the authors examine cumulative evidence regarding the cognitive sequelae of white matter abnormalities in adults without dementia. The influence of potential moderator variables, such as neuroimaging technique, location of the lesions, rating scale, and demographic characteristics of the sample on the association between the burden of white matter hyperintensities and cognitive performance was also examined. Results indicate that white matter abnormalities observed on MR images are associated with attenuated performance on tasks of processing speed, immediate and delayed memory, executive functions, and indices of global cognitive functioning. There was no significant link between the white matter hyperintensities and psychometric indices of intelligence or fine motor performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of the marmoset Callithrix jacchus (sagüi) as an experimental model for the dyslipoproteinemia of human Schistosomiasis mansoni

BACKGROUND: There have been only a few brain computed tomography imaging studies, with mostly negative findings, in subjects with borderline personality disorder (BPD). This is the first MRI study which evaluated the structural abnormalities of the brain in subjects with the sole diagnosis of BPD. METHODS: Twenty-five subjects with BPD were compared with age-, gender-matched healthy comparison subjects (n=25) on volumes of the frontal lobes, the temporal lobes, the lateral ventricles, and the cerebral hemispheres in brain magnetic resonance imaging. RESULTS: Subjects with BPD had a significantly smaller frontal lobe compared to comparison subjects (multivariate regression analysis, t=2.225, df=46, P=0.031). There were no significant differences in volumes of the temporal lobes, the lateral ventricles, and the cerebral hemispheres between subjects with and without BPD. LIMITATIONS: Strict inclusion and exclusion criteria employed in the present study may make it difficult to generalize our findings. The gray matter and white matter of the brain were not measured separately. Differences in head tilt during image acquisition were not corrected. CONCLUSIONS: The current study reports a smaller frontal lobe volume on brain MRI in subjects with BPD compared with healthy comparison subjects. This finding may serve as a potentially useful biological variable that may allow for subtyping BPD.     

Use and misuse of syringes in anaesthesia

OBJECTIVE: To assess whether the cerebral gray and white matter volume deficits described in patients with anorexia nervosa (AN) are fully reversible with weight rehabilitation. DESIGN: A prospective cohort study using magnetic resonance imaging to examine the brains of female adolescents after weight recovery from AN. SETTING: An adolescent eating disorder program located in a tertiary care children's hospital. PARTICIPANTS: Of 13 patients who underwent a previous magnetic resonance imaging study at a low weight, 6 patients were weight recovered and underwent rescanning. All brain measures were corrected for the effects of intracranial volume and age, based on a regression analysis of a group of 34 healthy female control subjects. Scans from the patients with AN were also compared with scans from an age-matched subset of 16 healthy female controls. MAIN OUTCOME MEASURES: White matter volumes, gray matter volumes, and cerebrospinal fluid volumes in the weight-recovered AN group. RESULTS: Quantitative analysis showed that white matter and ventricular cerebrospinal fluid volumes changed significantly (P = .03 for both) on weight recovery from AN. The weight-recovered patients had significant gray matter volume deficits (P = .01) and elevated cerebrospinal fluid volumes (P = .005) compared with those of the age-matched controls. They no longer had significant (P = .30) white matter volume deficits. CONCLUSION: The finding of persistent gray matter volume deficits in patients who have recovered their weight after AN suggests an irreversible component to the structural brain changes associated with AN, in addition to a component that resolves on weight recovery.     

Phosphocreatine and creatine kinase in piglet cerebral gray and white matter in situ

Rates of adenosine triphosphate (ATP) metabolism are higher in cerebral gray matter than in white matter. Like other excitable tissues, brain contains a phosphocreatine (PCr)/creatine kinase (CK)/ATP system including cytosolic (B-CK) and mitochondrial (Mi-CK) isozymes. High B-CK activity is present in white and gray matter while Mi-CK is mostly in gray matter. An in situ localizing 31P-NMR technique, one-dimensional chemical shift imaging (1D-CSI), has been used to study the PCr/CK/ATP system in these regions. In the metabolically mature 4-week-old piglet, the PCr/nucleoside triphosphate (NTP) ratio measured by the 1D-CSI technique is at least 50% higher in white than gray matter. Total creatine (Cr), ATP, and total NTP concentrations are the same in rapidly frozen rat white and gray matter, suggesting that PCr/Cr ratio is much higher in white matter. The PCr increases more in gray than white matter between 4 days and 4 weeks of age in piglet brain. The CK catalyzed reaction rate constant, measured by combining the saturation transfer experiment with the 1D-CSI, is also much higher in white than gray matter at both ages. The postnatal maturational increase in the CK rate constant is greater in gray matter. In summary, these differences in PCr concentration and CK reaction rates and isozymes characterize two physiologically different PCr/CK/ATP systems in gray and white matter.     

The plasticity of human maternal brain: Longitudinal changes in brain anatomy during the early postpartum period.

Animal studies suggest that structural changes occur in the maternal brain during the early postpartum period in regions such as the hypothalamus, amygdala, parietal lobe, and prefrontal cortex and such changes are related to the expression of maternal behaviors. In an attempt to explore this in humans, we conducted a prospective longitudinal study to examine gray matter changes using voxel-based morphometry on high resolution magnetic resonance images of mothers' brains at two time points: 2–4 weeks postpartum and 3–4 months postpartum. Comparing gray matter volumes across these two time points, we found increases in gray matter volume of the prefrontal cortex, parietal lobes, and midbrain areas. Increased gray matter volume in the midbrain including the hypothalamus, substantia nigra, and amygdala was associated with maternal positive perception of her baby. These results suggest that the first months of motherhood in humans are accompanied by structural changes in brain regions implicated in maternal motivation and behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pathogenesis of leukoaraiosis: a review

BACKGROUND: Changes in the cerebral hemispheric white matter, detectable with increasing frequency by modern neuroimaging methods, are associated with aging and conceivably may contribute to the development of specific cognitive deficits. The pathogenesis of these cerebral white matter abnormalities (sometimes described as leukoaraiosis) is unknown. This review evaluates the available evidence in support of the hypothesis that the etiology of leukoaraiosis is related to a specific type of cerebral ischemia and highlights mechanisms by which ischemic injury to the brain may induce selected structural alterations limited to the cerebral white matter. SUMMARY OF REVIEW: The review is based on the critical analysis of over 100 publications (most appearing in the last decade) dealing with the anatomy and physiology of the arterial circulation to the cerebral white matter and with the pathogenesis of leukoaraiosis. CONCLUSIONS: A significant number of clues support the hypothesis that some types of leukoaraiosis may be the result of ischemic injury to the brain. Structural changes affecting the small intraparenchymal cerebral arteries and arterioles that are associated with aging and with stroke risk factors, altered cerebral blood flow autoregulation, and the conditions created by the unique arterial blood supply of the hemispheric white matter each seem to contribute to the development of leukoaraiosis. To the best of our ability to interpret current information, the type of ischemic injury that is most likely responsible for these white matter changes involves transient repeated events characterized by moderate drops in regional cerebral blood flow that induce an incomplete form of infarction. This hypothesis could be tested in appropriate experimental models.     

Radium in drinking water and the risk of death from bone cancer among Ontario youths

Using a 4.1T whole body system, we have acquired 1H spectroscopic imaging (SI) data of N-acetyl (NA) compounds, creatine (CR), and choline (CH) with nominal voxel sizes of 0.5 cc (1.15 cc after filtering). We have used the SI data to estimate differences in cerebral metabolites of human gray and white matter. To evaluate the origin of an increased CR/NA and CH/NA ratios in gray matter relative to white matter, we measured the T1 and T2 of CR, NA, and CH in gray and white matter using moderate resolution SI imaging. In white matter the T2s of NA, CR, and CH were 233 +/- 27, 141 +/- 18, and 167 +/- 20 ms, respectively, and 227 +/- 27, 140 +/- 16, and 189 +/- 25 ms in gray matter. The T1 values for NA, CR, and CH were 1267 +/- 141, 1487 +/- 146, and 1111 +/- 136 ms in gray matter and 1260 +/- 154, 1429 +/- 233, and 1074 +/- 146 ms in white matter. After correcting for T1 and T2 losses, creatine content was significantly lower in white matter than gray (P < 0.01, t-test), with a white/gray content ratio of 0.8, in agreement with biopsy and in vivo measurements at 1.5 and 2.0T.     

Metabolic and hemodynamic evaluation of brain metastases from small cell lung cancer with positron emission tomography

Brain metastases from small cell lung cancer respond to chemotherapy, but response duration is short and the intracerebral concentration of chemotherapy may be too low because of the characteristics of the blood-brain barrier. Positron emission tomography has been applied in a variety of tumors for studies of metabolic and hemodynamic features. This study was performed to determine regional cerebral metabolic rate of glucose (rCMRglu), regional cerebral blood flow (rCBF), and regional cerebral blood volume (rCBV) in brain metastases from small cell lung cancer and the surrounding brain. Tumor rCMRglu, rCBF, and rCBV exerted a broad variability, but were higher than the corresponding values in white matter and higher than or similar to those of gray matter. Tumor rCMRglu and rCBF were highly correlated (P < 0.01, r = 0.79). No correlation between survival and metabolic or hemodynamic parameters could be demonstrated. After radiotherapy, mean tumor rCMRglu decreased from 0.40 to 0.31 micromol/g/min (not significant), and rCBF and rCBV remained unchanged. However, cortical rCBF demonstrated a trend of increased values after radiotherapy from 0.37 to 0.49 ml/g/min (P = 0.13). No change in rCMRglu was observed in gray or white matter after radiotherapy. Global CBF seems to be reversibly depressed by the metastases, but local hemodynamic changes in the tumor could not be detected with positron emission tomography in this study. An association between high tumor rCMRglu and rCBF as an indicator of hypoxia was not observed. Other methods for noninvasive in vivo analysis of tumor hemodynamics are needed, especially for discrimination between tumor necrosis and hypoxia.     

Regional dynamic signal changes during controlled hyperventilation assessed with blood oxygen level-dependent functional MR imaging

PURPOSE: To quantitate the amplitude changes and temporal dynamics of regional functional MR imaging signals during voluntary hyperventilation using blood oxygen level-dependent contrast echo-planar imaging. METHODS: Seven male subjects were studied during voluntary hyperventilation (PetCO2 = 20 mm Hg) regulated by capnometry. Measurements were made on multisection echo-planar MR images obtained with parameters of 1000/66 (repetition time/echo time), flip angle of 30 degrees, and voxel size of 3 x 3 x 5 mm3. Sensitivity of the functional MR imaging signal to changes in PetCO2, time delays in relation to PetCO2 changes, and time constants of functional MR imaging signal changes were assessed on a region-by-region basis. RESULTS: Within 20 seconds of starting hyperventilation, rapid and substantial decreases in the functional MR imaging signal (by as much as 10%) were measured in areas of gray matter, which were significantly greater than the modest changes observed in white matter. Regional-specific effects in areas of the frontal, occipital, and parietooccipital cortex were stronger than in subcortical regions or in the cerebellum. Signal decreases measured with functional MR imaging were significantly delayed with respect to the reduction in PetCO2. Apparent differences between regional time constants did not reach statistical significance. CONCLUSION: Regional and gray-white matter differences in functional MR imaging signal changes during controlled hyperventilation may reflect differences in metabolic activity, vascular regulation, and/or capillary density. When measuring brain activation with functional MR imaging, arterial PCO2 differences due to unregulated respiration may confound interpretation of activation-related functional MR imaging signal changes.