bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of brain glutamate and glutamine in spectroscopic images at 4.1 T
Authors: Mason Graeme F. , Pan Jullie W. , Ponder Steven L. , Twieg Donald B. , Pohost Gerald M. , Hetherington Hoby P. 
Published: March 2007

AbstractBrain glutamate and glutamine were detected in healthy human volunteers in spectroscopic images with a nominal voxel size of 2.25 cm3 at an echo time of 15 ms. Due to the increased frequency separation and simplification of J‐coupling patterns, the separate detection of brain glutamate and glutamine at short echo times was possible. Creatine, choline, and N‐acetylaspartate with other N‐acetylated compounds were also detected. The ratios of the metabolite resonance intensities were in agreement with previously published values.
Analysis of macromolecule resonances in 1H NMR spectra of human brain
Authors: Behar Kevin L. , Rothman Douglas L. , Spencer Dennis D. , Petroff Ognen A. C. 
Published: March 2007

AbstractMacromolecule resonances underlying metabolites in 1H NMR spectra were investigated in temporal lobe biopsy tissue from epilepsy patients and from localized 1H spectra of the brains of healthy volunteers. The 1H NMR spectrum of brain tissue was cornpared with that of cytosol and dialyzed cytosol after removal of low molecular weight molecules (4500 daltons) at 8.4 and 2.1 Tesla. The assignment of specific resonances to macromolecules in 2.1 Tesla, short‐ TE, localized human brain 1H NMR spectra in vivo was made on the basis of a J‐editing method using the spectral parameters (δ, J) and connectivities determined from 2D experiments in vitro. Two prominent corinectivities associated with macromolecules in vitro (0.93–2.05 δ and 1.6–3.00 δ) were also detected in vivo by the J‐editing method. Advantage was taken of the large difference in measured T1 relaxation times between macromolecule and metabolite resonances in the brain spectrum to acquire ‘metabolite‐nulled’ macromolecule spectra. These spectra appear identical to the spectra of macromolecules isolated in vitro.
In vivo measurement of water diffusion in the human heart
Authors: Edelman Robert R. , Gaa Jochen , Wedeen Van J. , Loh Evan , Hare Joshua M. , Prasad Pottumarthi , Li Wei 
Published: March 2007

AbstractExisting magnetic resonance methods for diffusion imaging, including echo planar, are ineffective in the beating heart due to motion‐induced signal attenuation. To overcome this problem, we used a diffusion‐weighted stimulated echo‐echo planar magnetic resonance imaging sequence. The two lobes of the diffusion‐sensitizing gradient were synchronized to the same point in successive cardiac cycles in order to fix the cardiac position and avoid bulk motion effects. The apparent diffusion coefficients (ADCs) of the interventricular septum in 12 healthy subjects for diffusion gradients along the x‐, y‐, and z‐directions were 1.40 ± 0.27, 1.48 ± 0.35, and 1.78 ± 0.27 × 10−3 mm2/s. The ADCs of the interventricular septum in a second group of 15 healthy subjects for diffusion gradients along the short axis, horizontal and vertical long axes were 0.92 ± 0.15. 1.50 ± 0.15, and 1.10 ± 0.24 × mm2/s. Because the ADCs were less than the measured values for skeletal muscle and their standard deviations were low, it seems unlikely that bulk motion effects made the dominant contribution to the measured myocardial ADC for the interventricular septum, although motion and/or susceptibility artifacts frequently degraded measurements in the free wall of the left ventricle. Additional evidence that ADC was not predominantly determined by wall motion was obtained in a third group of patients with various cardiac abnormalities, in whom there was only a weak correlation between ADC and ejection fraction. Although further study is needed to better understand the factors contributing to the myocardial ADC, we hypothesize that the measured diffusional anisotropy in the septum might be explained largely on the basis of myofiber orientation.
Localized MR 1H spectroscopy reveals alterations of susceptibility in bone marrow with hemosiderosis
Authors: Schick Fritz , Einsele Hermann , Kost Renate , Duda Stephan H. , Horny Hans‐Peter , Lutz Otto , Claussen Claus D. 
Published: March 2007

AbstractA noninvasive investigation of the structure of hemopoietic bone marrow is based on the determination of the magnetic field distribution within small volume elements in vertebral bodies by localized 1H MR spectroscopy. In patients with he‐matological diseases the status of the bone marrow was found to considerably influence the homogeneity of the magnetic field in trabecular bone in vivo. The line widths of the 1H signals were evaluated in follow‐up studies during initial chemotherapy of eight patients with leukemia. lntraindividual comparison revealed significant broadening of the field distribution after a few weeks of cytotoxic treatment in five of the patients. Additionally, 19 patients after bone marrow transplantation showed significantly broader field distributions in the lipid signals than 13 matched healthy volunteers. These alterations of the microscopic field homogeneity were not caused by trabecular density effects. Iliac crest biopsies revealed high amounts of hemosiderin in the cases with broadened line widths. Ten of the 19 patients after bone marrow transplantation showed high amounts of hemosiderin and broad lines in the spectra. The content of hemosiderin of the other patients was not significantly increased.
Correlation between choline level and Gd‐DTPA enhancement in patients with brain metastases of mammary carcinoma
Authors: Sijens Paul E. , van Dijk Pieter , Oudkerk Matthijs 
Published: March 2007

AbstractSingle voxel 1HH double spin‐echo MR spectroscopy was used to examine 15 cases of brain metastasis of mammary carcinoma (18 lesions) in relation to Gd‐DTPA enhanced MR imaging. For lesions larger than 50% of MRS voxel size, there was significant correlation between Gd‐DTPA‐enhanced MRI signal and MRS‐detected signal of choline (Cho) containing compounds (r = 0.86, P < 0.01; n = 8). The observed loss of correlation when including the smaller lesions was overcome by correcting for partial volume effects (r = 0.69, P < 0.002; n = 18). Metastasis spectra showed increased Cho compared with control spectra, except for those lesions showing detectable lactate (Lact) signal. The detection of Lact in four of the larger lesions coincided with comparatively low levels of creatine (Cr) and Cho and heterogeneous Gd‐DTPA enhancement (ring‐enhancement). It was concluded that in brain metastases of mammary carcinoma Lact represents a product of ischemia preceding/during tissue decay resulting in central necrosis, rather than tumor specific metabolism resulting in increased glycolysis.
Radial turbo spin echo imaging
Authors: Rasche Volker , Holz Dietrich , Schepper Willi 
Published: March 2007

AbstractFast MR imaging methods should provide a familiar contrast behavior at a reduced scan time. The multi‐spin echo approach (TSE) is one of the most promising techniques satisfying this condition. Although the data acquisition time is significantly reduced, image quality may still suffer from artifacts due to patient motion and flow. The radial turbo spin echo (rTSE) approach combines TSE methods and projection reconstruction (PR) techniques. In PR images, artifacts induced by patient motion or flow are known to have a different appearance with lower level of intensity. The contrast and artifact behavior of the rTSE approach has been investigated. The new technique has been applied to abdominal imaging with acquisition times shorter than 30 s and to heart imaging in combination with cardiac triggering.
High speed bolus tagging: time resolved velocity quantification of pulsatile flow in a single breath hold
Authors: Chien Daisy , Saloner David , Laub Gerhard , Simonetti Orlando , Anderson Charles M. 
Published: March 2007

AbstractWe have implemented a high speed method for cardiac‐trig gered blood velocity quantification within a single breath hold on a conventional MR system. The method, based on bolus tagging, was tested using a pulsatile flow phantom and evaluated in vivo. The image acquisition time was reduced by a factor of N by acquiring N phase encode lines per bolus tag application. The clarity of the flow tag was found to vary with how k‐space was covered during data collection. The technique was optimized and multiple bolus tag images were obtained throughout the cardiac cycle within a single breath‐hold.
Echo‐volume imaging
Authors: Song Allen W. , Wong Eric C. , Hyde James S. 
Published: March 2007

AbstractTwo single‐shot volume imaging techniques are described. The first, single‐echo echo‐volume imaging, is essentially the echo‐volume imaging (EVI) sequence suggested by Mansfield (J. Phys. C. 10, L55 (1977)). The second is a multi‐spin‐echo approach in which one plane of k‐space is collected during each spin echo. In both techniques, phase encoding gradients are applied in the z direction, and three‐dimensional k‐space is filled by a raster pattern in Cartesian coordinates. Spatial saturation is used to avoid aliasing in the y direction, and a selective pulse is applied to excite the desired slab of tissue and eliminate aliasing in z. The average echo‐times, measured from the center of the 90° pulse to the center of the acquisition k‐space(kx= ky kz = 0), were 45 and 104 ms for single echo and multi‐echo methods, respectively. Images of the human brain using both sequences are shown.
Gradient moment nulling in fast spin echo
Authors: Hinks R. Scott , Constable R. Todd 
Published: March 2007

AbstractThe fast spin echo sequence combines data from many echo signals in a Carr‐Purcell‐Meiboom‐Gill echo train to form a single image. Much of the signal in the second and later echoes results from the coherent addition of stimulated echo signal components back to the spin echo signal. Because stimulated echoes experience no dephasing effects during the time that they are stored as M, magnetization, they experience a different gradient first moment than does the spin echo. This leads to flow‐related phase differences between different echo components and results in flow voids and ghosting, even when the first moment is nulled for the spin echo signal. A method of gradient moment nulling that correctly compensates both spin echo and stimulated echo components has been developed. The simplest solution involves nulling the first gradient moment at least at the RF pulses and preferably at both the RF pulses and the echoes. Phantom and volunteer studies demonstrate good suppression of flowrelated artifacts.
Echo‐Planar Diffusion Spectroscopic Imaging
Authors: Bito Yoshitaka , Hirata Satoshi , Nabeshima Takayuki , Yamamoto Etsuji 
Published: March 2007

AbstractHigh‐speed diffusion spectroscopic imaging based on an echo‐planar technique is presented. A pair of diffusion gradients is applied prior to a rapidly oscillating magnetic field gradient which encodes both chemical shift and spatial information. By applying this technique to a phantom consisting of acetone and water, a diffusion spectroscopic image is obtained in about 15 min, about 64 times faster than the time required in the conventional method. The measured diffusion coefficients show good agreement with previously reported values. This kind of diffusion spectroscopic imaging is expected to provide a way to observe more specific metabolism.
Coronary MRI with a Respiratory Feedback Monitor: The 2D Imaging Case
Authors: Wang Yi , Christy Paul S. , Korosec Frank R. , Alley Marcus T. , Grist Thomas M. , Polzin Jason A. , Mistretta Charles A. 
Published: March 2007

AbstractThe inability to return the heart to the same position for all breath‐holds during 2D coronary MR imaging can result in imaging different locations than desired. This can lead to problems such as (i) missing a whole vessel, or a part of it, (ii) misaligning segments of vessels imaged in different breath‐holds, and (iii) degrading image quality when a single slice is acquired in multiple breath‐holds. To reduce inconsistencies in the breath‐hold level, we designed a respiratory feedback monitor (RFM) that uses a bellows to monitor the circumference of the subject's chest. When the circumference of the subject's chest is within preset limits, an audio signal alerts subjects to hold their breath at that position. Use of the RFM significantly reduces the problems caused by inconsistent breath‐holds and the number of breath‐holds for an examination in 2D coronary MR imaging.
The Voxel Sensitivity Function in Fourier Transform Imaging: Applications to Magnetic Resonance Angiography
Authors: Parker Dennis L. , Du Yiping P. , Davis Wayne L. 
Published: March 2007

AbstractIn this paper the problem of small structure visualization in magnetic resonance imaging (MRI) is considered. The relationship between the structure and the image intensities is defined in terms of the voxel sensitivity function (VSF). Using the VSF, the spatial dependence of the voxel signal for small spheres and cylinders is computed. Although the spatial fluctuation is smaller in the MRI VSF than that which would be obtained from a uniformly sensitive cubical voxel, the deviation still results in significant signal loss near the edges and corners of the voxels. Finally, the VSF formalism is used to demonstrate the improvement in signal uniformity that can be obtained by using zero‐filled (band‐limited or sinc) interpolation.
In Vivo Dynamic MRI Tracking of Rat T‐Cells Labeled with Superparamagnetic Iron‐Oxide Particles
Authors: Yeh Tzu‐Chen , Zhang Weiguo , Ildstad Suzanne T. , Ho Chien 
Published: March 2007

AbstractDynamic MRI tracking of rat T‐cells in vivo is performed in rat testicles after labeling isolated rat T‐cells in vitro with superparamagnetic dextran‐coated iron‐oxide particles, BMS180549. Tissue inflammation induced by the local injection of the calcium ionophore, A23187, is used to attract labeled T‐cells. Gradient‐echo MR images of rat testicles show a statistically significant decrease (4%) of the signal intensity in areas of injection of A23187 as early as 30 min after intravenous infusion of 2 x 108 labeled T‐cells. The signal change reaches its maximum (6–7% decrease) at about 60–120 min after cell infusion. T2‐mapping also shows a decrease of T2 in the areas with A23187. Image quantitation, which includes a chemical‐shift effect, significantly enhances the sensitivity for detection of superparamagnetically labeled T‐cells. Localization of labeled T‐cells in rat testicles has been verified by fluorescence microscopy studies of T‐cells co‐labeled with a lipophilic fluorescent carbocyanine dye, 1,1‐dioctadecyl‐3,3,3',3'‐tetramethyl‐lindocarbocyanine perchlorate. These results represent the first successful demonstration of dynamic tracking of specific cells in vivo using MRI.
Computerized Consensus Diagnosis: A Classification Strategy for the Robust Analysis of MR Spectra. I. Application to 1H Spectra of Thyroid Neoplasms
Authors: Somorjai Ray L. , Nikulin Alexander E. , Pizzi Nic , Jackson Dick , Scarth Gordon , Dolenko Brion , Gordon Heather , Russell Peter , Lean Cynthia L. , Delbridge Leigh , Mountford Carolyn E. , Smith Ian C. P. 
Published: March 2007

AbstractWe introduce and apply a new classification strategy we call computerized consensus diagnosis (CCD). Its purpose is to provide robust, reliable classification of biomedical data. The strategy involves the cross‐validated training of several classifiers of diverse conceptual and methodological origin on the same data, and appropriately combining their outcomes. The strategy is tested on proton magnetic resonance spectra of human thyroid biopsies, which are successfully allocated to normal or carcinoma classes. We used Linear Discriminant Analysis, a Neural Net‐based method, and Genetic Programming as independent classifiers on two spectral regions, and chose the median of the six classification outcomes as the consensus. This procedure yielded 100% specificity and 100% sensitivity on the training sets, and 100% specificity and 98% sensitivity on samples of known malignancy in the test sets. We discuss the necessary steps any classification approach must take to guarantee reliability, and stress the importance of fuzziness and undecidability in robust classification.
MR Imaging with Hyperpolarized 3He Gas
Authors: Middleton Hunter , Black Robert D. , Saam Brian , Cates Gordon D. , Cofer Gary P. , Guenther Robert , Happer William , Hedlund Lawrence W. , Alan Johnson G. , Juvan Kim , Swartz John 
Published: March 2007

AbstractMagnetic resonance images of the lungs of a guinea pig have been produced using hyperpolarized helium as the source of the MR signal. The resulting images are not yet sufficiently optimized to reveal fine structural detail within the lung, but the spectacular signal from this normally signal‐deficient organ system offers great promise for eventual in vivo imaging experiments. Fast 2D and 3D GRASS sequences with very small flip angles were employed to conserve the nonrenewable longitudinal magnetization. We discuss various unique features associated with performing MRI with hyperpolarized gases, such as the selection of the noble gas species, polarization technique, and constraints on the MR pulse sequence.
Changes in T2*‐Weighted Images During Hyperoxia Differentiate Tumors from Normal Tissue
Authors: Kuperman Vadim Y U. , River Jonathan N. , Lewis Martha Z. , Lubich Leslie M. , Karczmar Gregory S. 
Published: March 2007

AbstractExperiments were performed to determine whether changes in T2*‐weighted MR images during and after hyperoxia differentiate tumors from normal tissue. Mammary adenocarcinomas implanted in the right hind limbs of rats were studied. Gradient echo images were obtained at 2 Tesla with an evolution time of 20 ms and a recycle time of 1 s. Breathing gas was either air or 100% O2. Significant increases in image intensity were observed in tumor centers and rims during hyperoxia while much smaller changes were detected in the surrounding muscle. The relaxation rate (1/T2*) in tumors decreased during hyperoxia by an average of 2.5 ± 1.0 s−1, while in muscle the average change was an increase of 0.6 ± 2.1 s−1. The largest decreases in relaxation rate were detected in non‐necrotic tumor regions with relatively low density of blood vessels. Immediately following hyperoxia significant decreases in intensity were detected in tumors while much smaller decreases were detected in the surrounding muscle.
Effect of Radio Frequency Inhomogeneity Correction on the Reproducibility of Intra‐Cranial Volumes Using MR Image Data
Authors: Narayana Ponnada A. , Borthakur Arijitt 
Published: March 2007

AbstractThe volumes of total brain, white matter, gray matter, and cerebrospinal fluid in normal volunteers were determined using a supervised nonparametric feature map segmentation of dual‐contrast MR images after correcting for the radio frequency (RF) inhomogeneity. Reproducibility of the segmentation was evaluated in terms of inter‐observer and scan‐to‐scan variations. A comparison with the published results indicates that the scan‐to‐scan and inter‐observer variabilities in the determination of tissue volumes are substantially reduced following the RF inhomogeneity correction.
Dynamic Monitoring of Total‐Body Absorption by 19F NMR Spectroscopy: One Hour Ventilation of HFA‐134a in Male and Female Rats
Authors: Finch John R. , Dadey Eric J. , Smith Stanford L. , Harrison Lester I. , Digenis George A. 
Published: March 2007

AbstractSix male and six female Sprague‐Dawley rats were ventilated head‐only for 1 h on a 15% atmosphere of 1, 1, 1, 2‐tetrafluoroethane (HFA‐134a) in air in a magnetic resonance imaging spectrometer. Results from these dynamic 19F NMR studies suggest that a steady‐state in vivo concentration of HFA‐134a was approached at approximately 25 min into the exposure. Quantitative integration analysis using an external standard estimated this plateau to be 58.3 ± 11.9 mg of absorbed HFA‐134a per rat. The HFA‐134a 19F NMR signal disappeared rapidly following removal of the test atmosphere, with an elimination half‐life of 4.6 ± 0.6 min in the male rats and 4.9 ± 1.5 min in the female rats. The data suggest that there was no statistical difference between the sexes in amount absorbed or in elimination half‐lives.
EPI Imaging of Global Increase of Brain MR Signal with Breath‐hold Preceded by Breathing O2
Authors: Kwong Kenneth K. , Wanke Isabel , Donahue Kathleen M. , Davis Timothy L. , Rosen Bruce R. 
Published: March 2007

AbstractBrain MR signal has been observed to decrease during cessation of breathing due to the increase of deoxyhemoglobin in the blood. However, for both animal and human studies, we have demonstrated that if the subjects breathed 100% oxygen in advance of apnea for a short time, T2*‐weighted MR brain signal increased when breathing was stopped for a period of 30–60 s. This demonstrates the possibility of measuring responses to hemodynamic change throughout the entire brain with a single respiratory perturbation in a rapid, reliable, and robust manner.
Motion Artifacts in fMRI: Comparison of 2DFT with PR and Spiral Scan Methods
Authors: Glover Gary H. , Lee Adrian T. 
Published: March 2007

AbstractActivation signals based on BOLD contrast changes consequent to neuronal stimulation typically produce cortical intensity differences of < 10% at 1.5T. Hemodynamically driven pulsation of the brain can cause highly pulsatile phase shifts, which in turn result in motion artifacts whose intensity is larger than the activation signals in 2DFT scan methods. This paper presents a theoretical and experimental comparison of the magnitude of such artifacts for 2DFT and two other methods using non‐Cartesian k‐space trajectories. It is shown that artifacts increase with TR for 2DFT methods, and that projection reconstruction (PR) and spiral methods have significantly reduced artifact intensities, because these trajectories collect low spatial frequencies with every view. The spiral technique is found to be superior in terms of efficiency and motion insensitivity.
Magnetic Resonance Imaging of Microwave Induced Tissue Heating
Authors: Schwarzmaier Hans‐Joachim , Kahn Thomas 
Published: March 2007

AbstractMR‐guided interstitial thermotherapy offers a minimally invasive treatment for localized tumors and tissue structures exhibiting functional abnormalities. In this study, microwaves (2.45 GHz) were used for tissue irradiation to overcome some limitations of the heating sources used so far. To this end, a microwave antenna was positioned in a specimen of porcine myocardium and irradiated for 10 min under MRI control using a T1‐weighted FLASH sequence. The heating procedure resulted in a spherical tissue lesion of 26 mm in diameter. Thus, we could demonstrate the feasibility to monitor the microwave‐induced coagulation process by MR‐imaging in vitro.
MR Microscopy of the Rat Carotid Artery after Balloon Injury by Using an Implanted Imaging Coil
Authors: Summers Ronald M. , Hedlund Laurence W. , Cofer Gary P. , Gottsman Michael B. , Manibo Jose F. , Allan Johnson G. 
Published: March 2007

AbstractNeointimal hyperplasia after angioplasty was followed in vivo in rats by using MR microscopy and surgically implanted RF imaging coils. By using an inductively coupled pick‐up coil, the arteries were imaged 4 days before and 3, 7, and 14 days after angioplasty with a 3DFT spin echo sequence. Eight of 10 angioplastied rats showed moderate to severe stensois based MR measures of lumen diameter reduction from baseline images. There was a good correlation between total wall thickness between MR and hematoxylin and eosin (H&E)‐stained sections obtained on the last day. Arteries in the intact and sham groups remained unchanged from baseline measurements. Because this imaging technique examines the artery under in vivo conditions of arterial pressure and flow, it promises to be a useful tool for evaluating pharmacological and mechanical methods of reducing the incidence of vascular stenosis.