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At least 595 records · Page 33Linked to original sources
PubMed2005

Hepatic triglyceride content and its relation to body adiposity: a magnetic resonance imaging and proton magnetic resonance spectroscopy study.

BACKGROUND: Hepatic steatosis is associated with obesity and type II diabetes. Proton magnetic resonance spectroscopy (1H MRS) is a non-invasive method for measurement of tissue fat content, including intrahepatocellular lipids (IHCL) and intramyocellular lipids (IMCL). PATIENTS AND METHODS: We used 1H MRS and whole body magnetic resonance imaging (MRI) to assess the relationship between IHCL accumulation, total body adipose tissue (AT) content/distribution, and IMCL content in 11 subjects with biopsy proven hepatic steatosis and 23 normal volunteers. RESULTS: IHCL signals were detectable in all subjects but were significantly greater in hepatic steatosis (geometric mean (GM) 11.5 (interquartile range (IQR) 7.0-39.0)) than in normal volunteers (GM 2.7 (IQR 0.7-9.3); p=0.02). In the study group as a whole, IHCL levels were significantly greater in overweight compared with lean subjects (body mass index (BMI) >25 kg/m2 (n=23): GM 7.7 (IQR 4.0-28.6) v BMI <25 kg/m2 (n=11): GM 1.3 (IQR 0.3-3.6; p=0.004)). There was a significant association between IHCL content and indices of overall obesity (expressed as a percentage of body weight) for total body fat (p=0.001), total subcutaneous AT (p=0.007), and central obesity (subcutaneous abdominal AT (p=0.001) and intra-abdominal AT (p=0.001)), after allowing for sex and age. No correlation between IHCL content and IMCL was observed. A significant correlation was observed between serum alanine aminotransferase and liver fat content (r=0.57, p=0.006). CONCLUSIONS: Our results suggest that hepatic steatosis appears to be closely related to body adiposity, especially central obesity. MRS may be a useful method for monitoring IHCL in future interventional studies.

Abdomen↗
PubMed2003

Plaque volume measurement by magnetic resonance imaging as an index of remodeling of middle cerebral artery: correlation with transcranial color Doppler and magnetic resonance angiography.

BACKGROUND: The feasibility of a noninvasive evaluation of remodeling of the middle cerebral artery (MCA) by magnetic resonance imaging (MRI) was assessed. The results were correlated with magnetic resonance angiography (MRA) and transcranial color Doppler (TCD) findings. METHODS: 26 patients (13 male and 13 female, age ranged from 46 to 82 years) who presented with symptoms of cerebrovascular accidents had TCD, MRA and MRI assessment of the MCA. The TCD and MRA findings of 40 MCAs accessible by TCD were correlated with the ratio of cross-sectional area of the vessel (VA), luminal area of the vessel (LA) and plaque load (PL). RESULTS: The VA ratio and LA showed no correlation with TCD or MRA results. PL however was shown to be associated with both TCD and MRA. CONCLUSIONS: MRI could be used to assess remodeling in MCAs. PL was found to be associated with TCD and MRA findings.

Aged↗
PubMed1998

Functional and metabolic evaluation of the athlete's heart by magnetic resonance imaging and dobutamine stress magnetic resonance spectroscopy.

BACKGROUND: The question of whether training-induced left ventricular hypertrophy in athletes is a physiological rather than a pathophysiological phenomenon remains unresolved. The purpose of the present study was to detect any abnormalities in cardiac function in hypertrophic hearts of elite cyclists and to examine the response of myocardial high-energy phosphate metabolism to high workloads induced by atropine-dobutamine stress. METHODS AND RESULTS: We studied 21 elite cyclists and 12 healthy control subjects. Left ventricular mass, volume, and function were determined by cine MRI. Myocardial high-energy phosphates were examined by 31P magnetic resonance spectroscopy. There were no significant differences between cyclists and control subjects for left ventricular ejection fraction (59+/-5% versus 61+/-4%), left ventricular cardiac index (3.4+/-0.4 versus 3.4+/-0.4 L x min(-1) x m[-2]), peak early filling rate (562+/-93 versus 535+/-81 mL/s), peak atrial filling rate (315+/-93 versus 333+/-65 mL/s), ratio of early and atrial filling volumes (3.0+/-1.0 versus 2.6+/-0.6), mean acceleration gradient of early filling (5.2+/-1.4 versus 5.8+/-1.9 L/s2), mean deceleration gradient of early filling(-3.1 +/- 0.9 versus -3.2 +/- 0.7 L/s2), mean acceleration gradient of atrial filling (3.6+/-1.8 versus 4.5+/-1.7 L/s2), and atrial filling fraction (0.23+/-0.06 versus 0.26+/-0.04, respectively). Cyclists and control subjects showed similar decreases in the ratio of myocardial phosphocreatine to ATP measured with 31P magnetic resonance spectroscopy during atropine-dobutamine stress (1.41+/-0.20 versus 1.41+/-0.18 at rest to 1.21+/-0.20 versus 1.16+/-0.13 during stress, both P=NS). CONCLUSIONS: Left ventricular hypertrophy in cyclists is not associated with significant abnormalities of cardiac function or metabolism as assessed by MRI and spectroscopy. These observations suggest that training-induced left ventricular hypertrophy in cyclists is predominantly a physiological phenomenon.

Adaptation, Physiological↗
PubMed1992

Myocardial energetics during ventricular fibrillation investigated by magnetization transfer nuclear magnetic resonance spectroscopy.

Ventricular fibrillation (VF) is known to produce alterations in myocardial energetics, but the mechanism of these changes remains unclear. To investigate energy metabolism during VF, phosphorus nuclear magnetic resonance spectroscopy and magnetization transfer were applied to isolated perfused ferret hearts. VF was induced either by perfusion with digitalis (strophanthidin, 30 microM) or by high-frequency electrical stimulation. We measured the flux in two critical reactions: from inorganic phosphate (Pi) to ATP (ATP synthesis rate) and from phosphocreatine (PCr) to ATP (energy transfer capacity). During digitalis-induced VF, energy-related phosphates showed changes similar to those during hypoxia: myocardial [Pi] increased and [PCr] decreased. Concomitantly, the ATP synthesis rate increased to levels about threefold higher than control, whereas oxygen consumption increased by only 16%. The ATP synthesis rate exhibited a strong negative correlation with left ventricular pressure during VF (r = -0.95, n = 5, p < 0.02), whereas oxygen consumption did not (r = 0.19, p > 0.05). On the other hand, energy transfer capacity catalyzed by creatine kinase was significantly smaller during VF than in the control condition but still higher than the simultaneous ATP synthesis rate. In contrast to the marked energetic deterioration during VF induced by digitalis, electrically induced VF led to only a small increase in [Pi] and a small decrease in [PCr], and there were no significant changes in the ATP synthesis rate, energy transfer capacity, or O2 consumption. These results indicate that the rundown in energy metabolism during VF induced by digitalis was mainly attributable to a limitation of energy production through oxidative phosphorylation as well as to a marked increase in energy consumption. In contrast, myocardial energy generation remained unimpaired during VF induced by electrical stimulation. Intracellular calcium overload is more severe during VF induced by digitalis than during electrically induced VF (Circ Res 1991;68:1378-1389); severe calcium overload would be expected to compromise the capacity for energy generation by mitochondria. Thus, we propose that known differences in cellular calcium loading underlie the discrepant energetic patterns of the two types of VF.

Animals↗
PubMed2003

Semantic processing in the left inferior prefrontal cortex: a combined functional magnetic resonance imaging and transcranial magnetic stimulation study.

The involvement of the left inferior prefrontal cortex (LIPC) in phonological processing is well established from both lesion-deficit studies with neurological patients and functional neuroimaging studies of normals. Its involvement in semantic processing, on the other hand, is less clear. Although many imaging studies have demonstrated LIPC activation during semantic tasks, this may be due to implicit phonological processing. This article presents two experiments investigating semantic functions in the LIPC. Results from a functional magnetic resonance imaging experiment demonstrated that both semantic and phonological processing activated a common set of areas within this region. In addition, there was a reliable increase in activation for semantic relative to phonological decisions in the anterior LIPC while the opposite comparison (phonological vs. semantic decisions) revealed an area of enhanced activation within the posterior LIPC. A second experiment used transcranial magnetic stimulation (TMS) to temporarily interfere with neural information processing in the anterior portion of the LIPC to determine whether this region was essential for normal semantic performance. Both repetitive and single pulse TMS significantly slowed subjects' reactions for the semantic but not for the perceptual control task. Our results clarify the functional anatomy of the LIPC by demonstrating that anterior and posterior regions contribute to both semantic and phonological processing, albeit to different extents. In addition, the findings go beyond simply establishing a correlation between semantic processing and activation in the LIPC and demonstrate that a transient disruption of processing selectively interfered with semantic processing.

Adult↗
PubMed2004

Proton magnetic resonance spectroscopy and magnetic resonance imaging findings in a patient with central nervous system paracoccidioidomycosis.

The authors describe a patient with brain paracoccidioidomycosis whose magnetic resonance image (MRI) showed multiple hypointense lesions on T2-weighted images with peripheral enhancement after gadolinium injection. Single-voxel proton magnetic resonance spectroscopy (1H-MRS) of one of the lesions showed 2 peaks at 0.9 and 1.32 ppm, corresponding to lipid signals, indicating intense necrosis. The other characteristic peaks of 1H-MRS were undifferentiated from baseline. These findings, although not specific, may help to differentiate fungal abscess from tumoral lesions and other types of abscess.

Adult↗
PubMed2006

Neural effects of MDMA as determined by functional magnetic resonance imaging and magnetic resonance spectroscopy in awake marmoset monkeys.

We used functional magnetic resonance imaging (fMRI) to investigate the acute effects of a recreational dose (1 mg/kg p.o.) of 3,4-methylenedioxymethamphetamine (MDMA) on regional brain activity in awake, restrained marmoset monkeys. In a second study, magnetic resonance spectroscopy (MRS) and postmortem measurements of serotonin transporter (SERT) binding and serotonin (5-HT) concentrations were used to determine the neurotoxic effects of low (4 x 1 mg/kg p.o.) and high (4 x 10 mg/kg i.m.) doses of MDMA. Several brain areas were significantly activated by the low oral dose of MDMA, including the midbrain raphe nuclei, hippocampus, hypothalamus, amygdala, and the corticostriatal circuit composed of the dorsal thalamus, sensory motor cortex, and basal ganglia. MDMA activated the primary visual cortex under baseline conditions and also enhanced the visual cortical response to photic stimulation. The onset of brain activation correlated well with the rise in plasma MDMA concentrations measured in separate monkeys given the same drug treatment. In the second study, the ratio of N-acetylaspartate (NAA; a putative neuronal marker) to creatine was significantly reduced in the hypothalamus following either MDMA treatment regimen, suggesting a particular vulnerability of this structure to MDMA-induced damage. Monkeys given the high-dose regimen also showed prolonged hyperthermia and reductions in 5-HT and SERT in a number of brain areas. These results are the first to identify the pattern of MDMA-induced brain activation in a nonhuman primate model, and they further suggest that even recreational doses of MDMA may have adverse consequences as indicated by the reduced hypothalamic NAA/creatine ratio.

Animals↗
PubMed1997

Functional magnetic resonance imaging and transcranial magnetic stimulation: complementary approaches in the evaluation of cortical motor function.

Functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) represent different approaches to mapping the motor cortex. fMRI identifies areas of hemodynamic changes during task performance while TMS provides electrophysiologic data concerning the localization and density of cortical motoneurons. Here we define the spatial correlation between fMRI and TMS maps and compared them with direct electrical cortical stimulation (ECS). We performed fMRI at 1.5 T on 3 normal subjects and 2 patients with mass lesions near the central sulcus using a multislice, asymmetric, spin-echo, echo-planar pulse sequence during the performance of a motor task. We also performed focal TMS with surface EMG recordings from the muscles primarily involved in the fMRI task. We coregistered the stimulation sites in real time with the fMRI maps using a frameless stereotactic system. In both patients we also performed ECS of the cortex during surgery under local anesthesia. fMRI maps were validated by the electrophysiologic data both pre- and intraoperatively. Our results suggest that regions of fMRI activation correspond spatially to areas of highest motoneuron density as demonstrated by electrophysiologic techniques.

Adult↗
PubMed2005

Proton magnetic resonance spectroscopic imaging integrated into image-guided surgery: correlation to standard magnetic resonance imaging and tumor cell density.

OBJECTIVE: In this study, we attempted to improve the delineation of the infiltration zone in gliomas using proton magnetic resonance spectroscopic imaging (1H MRSI). In conventional magnetic resonance imaging (MRI), the boundaries of gliomas sometimes are underestimated. 1H MRSI is a noninvasive tool that can be used to investigate the spatial distribution of metabolic changes in brain lesions. The purpose was to correlate tumor cell density from histopathological specimens with metabolic levels and the coregistered metabolic maps. METHODS: We developed a method to integrate spectroscopic data depicted as metabolic maps of biochemically pathological tissue into frameless stereotaxy. In seven patients harboring gliomas, we performed 1H MRSI with high spatial resolution and evaluated the spectral data. An algorithm was developed for user-independent calculation of pathological voxels and for visualization as metabolic maps. These maps were integrated into a three-dimensional MRI data set used for frameless stereotaxy. Stereotactic biopsies were taken from three different areas in and around the tumor involving the maximum pathological change, the border zone, and an area from outside the spectroscopically suspicious area. These specimens were correlated to the exact voxel positions in the stereotactic image space and evaluated histopathologically. RESULTS: In all cases, the implementation of the metabolic maps into frameless stereotaxy was successful, and stereotactic biopsies were acquired by use of the spectral data. A relation could be demonstrated between the metabolic changes and tumor cell density ranging from 60 to 100% in the maximum pathological area to 5 to 15% in the border zone. Interestingly, the tumor areas defined by the metabolic maps and histopathologically confirmed by biopsy exceeded the T2-weighted signal change in all cases, ranging from 6 to 32% in the examined volume. CONCLUSION: Our preliminary data suggest that 1H MRSI may be useful in combination with frameless stereotaxy to define more exactly the tumor infiltration zone in glioma surgery compared with conventional anatomic MRI alone.

Algorithms↗
PubMed1983

Nuclear magnetic resonance imaging: contrast-to-noise ratio as a function of strength of magnetic field.

The choice of the strength of the magnetic field for an imaging system based on the nuclear magnetic resonance of hydrogen is considered. It is shown by an analysis based on in vitro data that the quality, or contrast-to-noise ratio, of images based on T1 or T2 discrimination increases with field up to 1.5-2 T. After a brief discussion of potential high-field limitations, results are presented which show that images of the human head with excellent anatomic detail can be produced at 1.5 T or 64 MHz.

Magnetic Resonance Spectroscopy↗
PubMed1989

Magnetic resonance imaging and aneurysm clips. Magnetic properties and image artifacts.

The magnetic properties of 12 different types of aneurysm clip were investigated in order to identify which clips allow postoperative magnetic resonance (MR) imaging without risk. Clip-induced MR artifacts were also quantitatively studied using a geometrical phantom. Nonferromagnetic aneurysm clips like the Yaşargil Phynox, Sugita Elgiloy, and Vari-Angle McFadden clips do not appear to contraindicate MR studies performed with a FONAR beta-3000M imager. There is no clip movement upon introduction of the phantom into the MR imager, and the image artifacts caused by the clips are so limited that patients harboring such clips may well be considered for MR imaging. This examination may reveal information not obtainable by any other radiological modality.

Aneurysm↗
PubMed2006

Volvulus of the gall bladder diagnosed by ultrasonography, computed tomography, coronal magnetic resonance imaging and magnetic resonance cholangio-pancreatography.

A 54-year-old woman was admitted to our hospital with the complaint of right upper quadrant pain. Upon physical examination the vital signs of the patient were within normal ranges. Ultrasonography and computed tomography (CT) examination of the abdomen was obtained, which demonstrated a large dilatated cystic structure, measuring approximately 68.6 mm multiply 48.6 mm, with marked distension and inflammation. Additionally, the enhanced CT was characterized by the non-enhanced wall of the gallbladder. As the third examination in this study, magnetic resonance imaging (MRI), namely coronal MRI and magnetic resonance cholangio-pancreatogra (MRCP), were performed. The MRCP demonstrated a dilatation of the gallbladder but detected no neck of the gallbladder. Simple cholecystectomy was performed. Macroscopic findings included a distended and gangrenous gallbladder, and closer examination revealed a counterclockwise torsion of 360 degrees on the gallbladder mesentery. Coronal MRI and MRCP showing characteristic radiography may be useful in making a definitive diagnosis.

Cholangiopancreatography, Magnetic Resonance↗
PubMed1999

Role of magnetic resonance imaging and magnetic resonance angiography in patients with hemifacial spasm.

Vascular compression of the facial nerve is a well recognized cause of hemifacial spasm (HFS). In this study, we described the magnetic resonance imaging (MRI) and three-dimensional magnetic resonance angiography (MRA) techniques used and findings in 34 patients with hemifacial spasm. A vascular abnormality, defined as a vessel seen in close proximity, touching or compressing the facial nerve, was identified in 22 of the 25 patients (88%) who had both MRI and MRA studies. Vessels identified were anterior inferior cerebellar artery (59.2%), posterior inferior cerebellar artery (13.6%), vertebral artery (18.2%) and basilar artery (4.5%). All vascular abnormalities were ipsilateral to the side of the HFS. Only 3 of the 12 controls (25%) had a vascular abnormality in both MRI and MRA studies. One of the 9 HFS patients (11.1%) who had MRI only had an ipsilateral vascular abnormality. There is a role for combined MRI and MRA studies in the non-invasive evaluation of patients with HFS.

Adult↗
PubMed1992

[Experimental study on pathophysiology and treatment of congenital hydrocephalus evaluated by magnetic resonance imaging and magnetic resonance spectroscopy].

I. Experimental Study on Pathophysiology of Congenital Hydrocephalus It is well known that the major pathogenic mechanism of hydrocephalus is disturbance in cerebrospinal fluid (CSF) circulation. For this reason, many studies on hydrocephalus were intended from the viewpoint of CSF circulation both experimentally and clinically. However, few studies have yet been done on the correlation between the morphological changes and the changes in cerebral energy metabolism in hydrocephalus in vivo. So, in this study, the correlation between the morphological changes and the changes in cerebral energy metabolism in congenital hydrocephalic rats was evaluated experimentally. The morphological changes were estimated by using magnetic resonance imaging (MRI), and the longitudinal relaxation time (T1) of brain tissue at parietal area was also measured. The cerebral energy metabolism was evaluated by using 31P magnetic resonance spectroscopy (MRS) method, and cerebral phospholipid membrane metabolism was also evaluated by using 31P-MRS method. The region of interest (ROI) giving rise to the 31P spectra was placed at fore-brain and parietal area. The PCr/Pi ratio was used as the chosen indicator of cellular bioenergetic status. The PME/beta-ATP ratio and PDE/beta-ATP ratio were used as the chosen indicator of cerebral phospholipid membrane metabolism. The intracellular pH was also evaluated by using 31P-MRS method. Fifty congenital hydrocephalic rats of the HTX strain were used. The animals were divided into two groups--non-hydrocephalic group (n = 15) and hydrocephalic group (n = 35)--. The rats of hydrocephalic group were subdivided into three smaller groups according to the degree of hydrocephalus--mild (n = 15), moderate (n = 10) and severe (n = 10)--, which was estimated by using the cerebro-ventricular ratio (CVR) in coronal section of MRI. Experimental results were as follows: 1) The T1 values in rats of mild, moderate and severe hydrocephalic groups showed significant elongation in comparison with the value in non-hydrocephalic group (p less than 0.01), which indicated the expansion of interstitial edema in cerebral cortex. 2) The correlation between the T1 value and the CVR was evaluated and the correlation coefficient (r) was 0.932 which indicated high correlation. 3) The PCr/Pi ratios in rats of mild, moderate and severe hydrocephalic groups were decreased significantly in comparison with the value in non-hydrocephalic group (p less than 0.01), which demonstrated the disturbance of cerebral energy metabolism in congenital hydrocephalic rats. 4) The PCr/Pi ratio seemed to give the indicative data concerning the prognosis of congenital hydrocephalus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Magnetic resonance imaging and proton magnetic resonance spectroscopy in neuro-Behçet's disease.

OBJECTIVE: Neuro-Behcet's disease (NBD) is one of the most serious complications of Behcet's disease (BD). Proton magnetic resonance spectroscopy (1H MRS) has been proved to be useful in detecting neuro-metabolic abnormalities in various diseases affecting the brain. In this study, we attempted to characterize the magnetic resonance imaging (MRI) findings in Korean patients with NBD and then examined the usefulness of 1HMRS in evaluating the MRI-negative brain area of NBD patients. METHODS: We performed brain MRI in 18 BD patients with neurologic symptoms and signs. Seven NBD patients without thalamic lesions and 8 healthy controls underwent brain 1H MRS, in which an 8 ml voxel was placed in the left thalamus and the N-acetylaspartate (NAA)/creatine (Cr) ratio was measured. RESULTS: Fourteen of 18 BD patients were diagnosed as having NBD and 12 NBD patients (86%) had brain lesions on MRI. Most lesions were of high signal intensity on T2-weighted images and located in the midbrain, pons, basal ganglia, and white matter. On 1H MRS, the thalamic area without gross abnormalities on MRI showed a significantly lower NAA/Cr ratio in NBD patients compared to healthy controls (1.07 +/- 0.08 versus 1.54 +/- 0.27, P < 0.01). In 2 NBD patients, the NAA/Cr ratios, monitored serially, were normalized along with clinical improvement 6 months after treatment with prednisolone and immune suppressive agents. CONCLUSION: MRI is a very sensitive diagnostic method for NBD, and 1H MRS may be useful for the early detection and follow-up of MRI-negative NBD.

Adult↗
PubMed2004

Magnetic resonance imaging and proton magnetic resonance spectroscopy of intracranial epidermoid tumors.

Intracranial epidermoid tumors or cysts are considered benign lesions. Differentiation of epidermoid tumors from arachnoid cysts is important for appropriate patient care because the treatment is different for each lesion. Arachnoid cysts can appear very similar to epidermoid tumors on computed tomography (CT). Epidermoid tumors can grow in the cerebellopontine angle (CPA) cistern, the most common location of these lesions, resulting in trigeminal neuralgia and facial paralysis. Treatment for epidermoid tumors is exclusively surgery. Arachnoid cyst, on the other hand, is a benign condition that rarely produces symptoms. Recent advances in magnetic resonance imaging (MRI) have allowed more accurate imaging diagnosis of epidermoid tumors. This article reviews the recent advances in MRI using conventional T1W, post-contrast T1W, T2W, steady-state free precession imaging, fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and proton magnetic resonance spectroscopy (MRS) in the imaging diagnosis of epidermoid tumors.

Arachnoid Cysts↗
PubMed2006

Moyamoya disease--magnetic resonance imaging and magnetic resonance angiographic features.

A rare case of moyamoya disease in a 9-year-old female presented with behavioural disturbances and recurrent hemiparetic attacks is reported. Moyamoya disease is an uncommon form of arteritis which affects the cerebrovascular circulation. Magnetic resonance angiography is a non-invasive technique for evaluation of the carotid and vertebrobasilar circulation. The magnetic resonance angiography findings are typical and characteristic of this disease.

Cerebrovascular Circulation↗