bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Estimation of Local Brain Temperature by in Vivo1H Magnetic Resonance Spectroscopy
Authors: Cady Ernest B. , D'Souza Patricia C. , Penrice Juliet , Lorek Ann 
Published: March 2007

AbstractBrain temperature may be important for investigating pathology and cerebroprotective effects of pharmaceuticals and hypothermia. Two methods for estimating temperature using 1H magnetic resonance spectroscopy are described: a partially water‐suppressed binomial sequence and non‐water‐suppressed point‐resolved spectroscopy. Relative to N‐acetylaspartate (Naa), water chemical shift (θH2O‐Naa) in piglet brain depended linearly on temperature from 30° to 40°C: temperature was 286.9–94.0 θH2O‐Naa ° C. Thalamic temperature in six normal infants was 38.1° ± 0.4° C indicating that local brain temperature could be estimated with adequate sensitivity for studying pathologic and therapeutic changes.
Lactate production by human monocytes/macrophages determined by proton mr spectroscopy
Authors: López‐Villegas Dolores , Lenkinski Robert E. , , Wehrli Suzanne L. , Ho Wen‐Zhe , Douglas Steven D. 
Published: March 2007

AbstractElevated brain lactate has been observed by in vivo proton MRS in different pathological situations. The origin of this lactate remains controversial. The possibility that it was produced by the metabolism of phagocytic cells has been proposed. To investigate this hypothesis, the authors have employed high‐resolution proton MRS to monitor changes in glucose, lactate, and other metabolites in the medium used to culture human monocyte‐derived macrophages in vitro. Results show that the differentiation of human monocytes/macrophages in the presence of physiological stimulating factors (M‐CSF or GM‐CSF) was associated with an increase in lactate production and glucose utilization. The present results are consistent with the hypothesis that lactate detected by proton MRS in vivo may be produced by the metabolism of macrophages when infiltrates of these cells are present. The possible extrapolation of the authors' finding to the in vivo situation and its relevance are discussed.
Three‐dimensional spatial EPR imaging of the rat heart
Authors: Kuppusamy Periannan , Wang Penghai , Zweier Jay L. 
Published: March 2007

AbstractWhile instrumentation capable of performing three‐dimensional EPR imaging of free radicals in whole tissues and isolated organs has been developed at L‐band, important questions remain regarding the resolution and image quality that can be obtained in practice using the presently available free radical labels. Therefore, studies were performed applying three‐dimensional spatial EPR imaging at L‐band to image the distribution of free radical labels in the isolated heart and in phantoms of similar size. With nitroxide labels the obtainable resolution is limited by the presence of hyperfine structure in the EPR absorption function that in turn limits the maximum applicable gradient. The authors observed that with the nitroxide labels, resolutions in the range of 1–2 mm are possible, while with a single line glucose char label, resolutions of 0.2 mm are obtained. With the nitroxides, images were of sufficient resolution to resolve the overall global shape of the heart and the location of the left and right ventricular cavities; however, finer structures could not be resolved. With the glucose char much finer resolution could be obtained enabling visualization of the ventricles, aortic root, and proximal coronary arteries.
Double‐echo three‐point‐dixon method for fat suppression MRI
Authors: Szumowski Jerzy , Coshow William , Li Fang , Coombs Bernard , Quinn Stephen F. 
Published: March 2007

AbstractA double‐echo two‐excitation pulse sequence encoding fat and water signals for a phase‐sensitive three‐point Dixon‐type analysis (DE‐3PD) was developed and implemented on a 1.5 T MR imager. Data processing was performed using a previously developed two‐dimensional (2D) region‐growing algorithm, adapted to use double‐echo data. Density‐, T1, and T2‐weighted fat suppression images were obtained from six volunteers using the new fat suppression method. The images were compared with corresponding images obtained using frequency‐selective excitation fat suppression (FAT‐SAT) and a single‐echo three‐point‐Dixon method (SE‐3PD). The results demonstrate that the DE‐3PD sequence shortens the imaging time by one‐third compared with the SE‐3PD method, without loss in image quality. The data also show that a 2D region‐growing algorithm effectively unwraps the phase of DE‐3PD data sets, and that results of DE‐3PD fat signal suppression are consistently better than those obtained using a standard FATSAT method. The authors conclude that the double‐echo sequence provides density‐, T1, and T2‐weighted images that appear to be promising for routine clinical applications.
Quantitative analysis of regional left ventricular function after myocardial infarction in the pig assessed with cine magnetic resonance imaging
Authors: Holman Eduard R. , Vliegen Hubert W. , Van Geest Rob J. Der , H. C. Reiber Johan , Van Dijkman Paul R. M. , Laarse Arnoud Van Der , Roos Albert De , Van Wall Ernst E. Der 
Published: March 2007

AbstractTo assess the accuracy of quantitative analysis of global and regional wall motion and wall thickening of the left ventricle with cine magnetic resonance (MR), images obtained in eight pigs before and after myocardial infarction were compared with those obtained using gadolinium diethylenetriaminepen‐taacetic acid (Gd‐DTPA)‐enhanced multislice spin‐echo MR imaging and determination of pathology. The region with abnormal wall motion and wall thickening, as determined with cine MR imaging, identified the same region of infarction as indicated by Gd‐DTPA‐enhanced spin‐echo MR imaging and pathology. Within the infarcted region wall motion and wall thickening analyzed with the centerline method were significantly reduced. We conclude that the use of quantitative analysis of cine MR images accurately determines localization and extent of regional left ventricular dysfunction in the infarcted heartin vivo. This analysis using dedicated software including the centerline method allows sequential assessment of regional left ventricular function in normal and infarcted hearts.
Measurement of fluid‐shear rate by fourier‐encoded velocity imaging
Authors: Frayne Richard , Rutt Brian K. 
Published: March 2007

AbstractA new technique for estimating the blood fluid shear rate at the vessel wall is presented. The technique uses Fourier‐encoded velocity imaging to determine the velocity distribution within a spatial element (voxel) that straddles the bloodvessel wall interface. By appropriate processing, the velocity distribution (1) can determine the location of the wall‐blood interface within the voxel and (2) estimate the velocity profile across the spatial extent of the voxel. From this information, accurate estimates of fluid shear rate may be obtained. Simulations are presented to illustrate this technique and to show the effects of various error sources, including differences in proton densities between blood and wall tissues and flow‐related signal changes. Experimental evidence obtained for steady flow in straight tubes is also presented in support of the technique. The mean error in the experimental shear rate estimates found using the proposed technique was ‐15%. This represents a significant improvement over estimates obtained by extrapolation of the velocity profile over multiple voxels (mean error of ‐73%).
Magnetic resonance fluoroscopy using spirals with variable sampling densities
Authors: Spielman Daniel M. , Pauly John M. , Meyer Craig H. 
Published: March 2007

AbstractThe imaging of dynamic processes in the body is of considerable interest in interventional examinations as well as kinematic studies, and spiral imaging is a fast magnetic resonance imaging technique ideally suited for such fluoroscopic applications. In this manuscript, magnetic resonance fluoroscopy pulse sequences in which interleaved spirals are used to continuously acquire data and reconstruct one movie frame for each repetition time interval are implemented. For many applications, not all of k‐space needs to be updated each frame, and nonuniform k‐space sampling can be used to exploit this rapid imaging strategy by allowing variable update rates for different spatial frequencies. Using the appropriate reconstruction algorithm, the temporal updating rate for each spatial frequency is effectively proportional to the corresponding k‐space sampling density. Results from a motion phantom as well as in in vivo gadolinium diethylenetriaminopentaacetic acid (Gd‐DTPA) bolus tracking studies in a rat model demonstrate the high temporal resolution achievable using these techniques as well as the tradeoffs available with nonuniform sampling densities. This paper focuses on the acquisition of real‐time dynamic information, and all images presented are reconstructed retrospectively. The issues of real‐time data reconstruction and display are not addressed.
Proton spectroscopic imaging of the human brain using phased array detectors
Authors: Wald Lawrence L. , Moyher Susan E. , Day Mark R. , Nelson Sarah J. , Vigneron Daniel B. 
Published: March 2007

AbstractTwo and four‐coil phased array detectors have been developed to increase the sensitivity of proton spectroscopic imaging of the human brain. These include a quadrature figure‐8 coil for the study of the vertex, several arrays of 2‐4 small overlapping (6‐8 cm diameter) circular coils and a combination figure‐8 coil plus circular coil. These were constructed in our laboratory and tested to assess their utility for brain spectroscopy. Methods for optimally combining the data from the independent receivers based on the analytical coil maps or measured signal to noise ratios (SNRs) of the data were investigated. High spatial resolution (0.2‐0.4 cm3 voxel size) two‐ or three‐dimensional chemical shift images of normal brain were obtained in 17‐minute acquisitions. These spatial resolutions are comparable to those previously obtained with conventional small surface coils, but the specialized detectors allow this sensitivity to be achieved for a larger region or for previously inaccessible areas such as the top of the head. The coverage and SNR increases demonstrated are similar to those obtained in magnetic resonance phased array imaging.
Error in MR volumetric flow measurements due to ordered phase encoding in the presence of flow varying with respiration
Authors: Wolf Ronald L. , Hangiandreou Nicholas J. , Felmlee Joel P. , Rossman Phillip J. , Julsrud Paul R. , Riederer Stephen J. , Ehman Richard L. 
Published: March 2007

AbstractRespiratory ordered phase encoding is often employed in MRI studies to reduce image artifacts due to breathing motion. The purpose of this work was to evaluate error caused by the use of respiratory ordering of phase encoding in MR cine phase‐contrast (CPC) volumetric flow measurements when the flow rate is sensitive to respiration. It was hypothesized that this effect is due to the systematic biasing of a respiratory‐induced phase modulation function in k‐space. A theoretical model for the effects of respiration was developed and then tested in flow phantom studies and in normal volunteer studies. In phantom experiments, the use of respiratory ordering induced an error of as much as 13% in CPC volumetric flow measurements. In preliminary volunteer studies, error was as high as 26% in superior vena cava flow measurements versus less than 1% error in the ascending aorta. It is concluded that a potential for error exists in CPC volumetric flow measurements obtained with the use of respiratory ordering schemes. Volunteer studies with larger numbers are warranted. Clinical applications in which this effect may be important include flow measurements in vessels subject to variations in flow due to respiration, such as the venae cavae, pulmonary vasculature, and portal vein.
Quantitative nmr microscopy of multicellular tumor spheroids and confrontation cultures
Authors: Brandl Matthias , Tonn JÖRg‐Christian , Kotitschke Klaus , Goldbrunner Roland , Kerkau Siglinde , Haase Axel 
Published: March 2007

AbstractIn cancer research, tumor spheroids are a well established system to study tumor metabolism resembling the situation in vivo more closely cell monolayers. Spherical aggregates of malignant melanoma cells (MV3) and their invasion into rat brain aggregates have been investigated by quantitative NMR microscopy. Relaxation times (T1, T2) and diffusion parameter images were acquired with an in‐plane resolution of 14 × 14 μm2. The authors were able to demonstrate that the morphology of the spheroids can be visualized on these NMR maps. The contrast was mainly manifested in relaxation maps, where average relaxation times T1 = 1.94 ± 0.17 s and T2 = 42.8 ± 6.3 ms were obtained for proliferating cells, and T1 = 2.49 ± 0.31 s and T2 = 104.3 ± 29.4 ms for the necrobiotic center. The mean diffusion coefficients were 0.59 ± 0.12 μm2/ms and 0.85 ± 0.14 μm2/ms, respectively. The authors could follow the dynamic process of tumor cell invasion in the investigated co‐culture system. Knowledge about tumor cell migration and tumor cell invasion is essential for the understanding of cancer and its therapy. Quantitative NMR microscopy can study this dynamic process noninvasively and therefore may help to assess the influence of therapy on the micromilieu of these spheroids.
The role of Na+/K+ ATPase activity during low flow ischemia in preventing myocardial injury: A 31P, 23Na and 87Rb NMR spectroscopic study
Authors: Cross Heather R. , Radda George K. , Clarke Kieran 
Published: March 2007

AbstractAn increase in intracellular Na+ during ischaemia has been associated with myocardial injury. In this study, we determined whether inhibition of Na+/K+ ATPase activity contributes to this increase and whether Na+/K+ ATPase activity can be maintained by provision of glucose to perfused rat hearts during low flow, 0.5 ml/min, ischemia. We used 31P NMR spectroscopy to determine changes in myocardial energetics and intracellular and extracellular volumes. 23Na NMR spectroscopy, with DyTTHA3‐ present as a shift reagent, was used to measure changes in intracellular Na+ and 87Rb NMR spectroscopy was used to estimate Na+/K+ ATPase activity from Rb+ influx rates, Rb+ being an NMR‐sensitive congener of K+. In hearts provided with 11 mM glucose throughout ischemia, glycolysis continued and ATP was twofold higher than in hearts without glucose. In the glucose‐hearts, Rb+ influx rate was threefold higher, intracellular Na+ was fivefold lower at the end of ischemia and functional recovery during reperfusion was twofold higher. We propose that continuation of glycolysis throughout low flow ischemia allowed maintenance of sufficient Na+/K+ ATPase activity to prevent the increase in intracellular Na+ that would otherwise have led to myocardial injury.
Reversible decreases in N‐acetylaspartate after acute brain injury
Authors: Stefano Nicola De , Matthews Paul M. , Arnold Douglas L. 
Published: March 2007

AbstractN‐Acetylaspartate (NAA), which constitutes the major proportion of the dominant resonance in proton MR spectra of brain, is localized in mature brain exclusively in neurons and neuronal processes. A decrease in NAA has been observed in many cerebral pathologies and has usually been interpreted as an index of irreversible neuronal loss. The authors report a follow‐up study of six patients with acute brain damage (four from demyelinating lesion and two from mitochondrial encephalopathy with lactic acidosis and stroke‐like episodes [MELAS]). All patients underwent serial MR spectroscopy examinations. The four patients with acute demyelinating lesions initially showed decreases in NAA in the centers of the lesions that ranged between 34‐72% of values from homologous brain volumes in the other hemisphere. All four patients subsequently showed substantial recovery of NAA as their clinical status improved. The two patients with MELAS syndrome had large decreases of NAA signal (50% and 20% of normal values, respectively) from their occipital lobe lesions during the acute stroke‐like episodes. After the acute phase of the illness a progressive increase of NAA in the same volumes was seen in both patients (to 76% and 60% of normal values, respectively). These results demonstrate that significant recovery of NAA can occur after acute brain damage. The potential contribution of reversible neuronal dysfunction (as well as neuronal loss) must be considered in the interpretation of decreases in the NAA resonance associated with acute brain pathology.
Locally focused mri
Authors: Cao Yue , Levin David N. , Yao Lian 
Published: March 2007

AbstractConventional magnetic resonance images are reconstructed by Fourier transformation and have uniform spatial resolution across the entire field of view (FOV). This paper describes a way of creating MR images that have higher spatial resolution in some areas than in others. High resolution imaging can be confined to just those areas where it is necessary to resolve strong edges without truncation artifact. Such locally focused images can be acquired in less scan time than that required to image the entire FOV with uniformly high resolution. Images are reconstructed from a subset of the usual phase‐encoded signals required to create a uniformly well‐resolved image. The measured signals are usually nonuniformly scattered ink‐space. Functional and interventional imaging may benefit from this technique, which makes it possible to acquire a rapid series of dynamical images that have high resolution in areas of expected change and lower resolution elsewhere. Spectroscopic images may be improved by using high resolution in the neighborhood of sharp edges (e.g., scalp lipids) that might otherwise cause truncation artifacts.
Local RBF‐FD solutions for steady convection–diffusion problems
Authors: Chandhini G. , Sanyasiraju Y. V. S. S. 
Published: March 2007

AbstractThis paper describes the application of radial basis function (RBF) based finite difference type scheme (RBF‐FD) for solving steady convection–diffusion equations. Numerical studies are made using multiquadric (MQ) RBF. By varying the shape parameter in MQ, the accuracy of the solution is seen to be highly improved for large values of Reynolds' numbers. The developed scheme has been compared with the corresponding finite difference scheme and found that the solutions obtained using the former are non‐oscillatory. Copyright © 2007 John Wiley & Sons, Ltd.
Sport for all?
Authors: Hardy K J , Kenyon R , Gillmsc G V 
Published: March 2007

AbstractHypoglycaemia may complicate exercise in insulin‐treated diabetic patients. An exercise‐induced fall in blood glucose has been well documented in the laboratory, but little has been published on the prevalence of clinically significant exercise‐induced hypoglycaemia. We studied the prevalence of exercise‐induced hypoglycaemia in patients attending our adolescent diabetes clinic by means of a questionnaire. Of the 55 respondents (mean age 16.9±1.6 years and mean diabetes duration 7.2±3.9 years), 45 took regular exercise. Only four (9%) patients were troubled by hypoglycaemia: one had proven factitious hypoglycaemia and three had better blood glucose control than the group as a whole (mean glycated haemoglobin (HbA1) for the hypoglycaemic patients 8.4±1.4 v 10.3±2.3% for the group as a whole). Forty‐two (93%) of the patients took precautions against hypoglycaemia: 31 altered their diet, three altered insulin and eight altered both. The diabetic patients performed as much sport as their non‐diabetic peers (4.2±3.1 v 4.4±3.7 hours/week). We conclude that exercise‐induced hypoglycaemia is uncommon in adolescent diabetic patients with satisfactory blood glucose control and that hypoglycaemia need not limit exercise in these young people provided appropriate precautions have been taken.
Metabolic control during Ramadan fasting
Authors: Beshyah S A , Jowett N I , Burden A C 
Published: March 2007

AbstractFifteen diabetic Muslim patients were studied to assess diabetic control during the fasting of Ramadan and the changes in the various haematological and biochemical blood parameters. No specific instructions were given to adjust their medications during the fast: six considered their diabetic control unchanged; seven improved; and two worsened. Mean weight fell from 69.1 to 68 kg (NS). Six mild episodes of hypoglycaemia were reported. No patient showed ketonuria and none needed admission to hospital. Plasma glucose and serum triglycerides fell with fasting, serum fructosamine and cholesterol levels did not alter significanly.Conclusions: most diabetics can safely fast but more medical attention to adjust their medication by increased dosage in the evening to combat hyperglycaemia and reduced dosage in early morning to prevent hypoglycaemia.
A new semiquantitative rapid test for screening for microalbuminuria
Authors: Agardh Carl‐David 
Published: March 2007

AbstractMicroalbuminuria is a predictor for later development of clinical nephropathy in both Type 1 and Type 2 diabetes mellitus, and therefore important to screen for.In this study, a new semiquantitative test‐strip (Micral‐Test®) method was compared with the results measured with a quantitative laboratory method in urine samples from 117 diabetic patients attending an out‐patient ward. When 20mg/I was chosen as the cut‐off point for pathological albumin concentration as determined by the laboratory method, pathological urinary concentrations were recorded by Micral‐Test® with a sensitivity of 87.8% and specificity of 97.4%. At higher readings, the comparison method tended to show higher values.It is concluded that the semiquantitative method tested can be used for screening for the presence of microalbuminuria. When microalbuminuria occurs, a quantitative method is recommended.
Capillary blood sampling: How much pain is necessary?. Part 2: Relation between penetration depth and puncture pain
Authors: Fruhstorfer H , Müller T , Scheer E 
Published: March 2007

AbstractThe relation between penetration depth and puncture pain was studied in 30 healthy subjects with a lancing device which allowed adjustment of depth (0.3–1.1mm). Pain was linearly related to depth as was the blood volume obtained. In about half of the individuals tested, an actual penetration depth of less than 1.0 mm provided sufficient blood for a glucose test.
Fatal cardiac arrest following acute hypoglycaemia in a diabetic patient
Authors: Frier BM , Barr StCG , Walker JD 
Published: March 2007

AbstractA patient is described who had long‐standing insulin‐dependent diabetes with multiple diabetic complications, and also had known coronary heart disease. While receiving treatment for acute severe hypoglycaemia he sustained a cardiac arrest and died. The haemodynamic effects and the risk of inducing cardiac arrhythmia imposed by acute hypoglycaemia is discussed. Measurement of capillary blood glucose is advised in any insulin‐treated diabetic patient presenting with an acute cardiac event.