bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen‐1, sodium‐23, and carbon‐13 MR spectroscopy of cartilage degradation in vitro
Authors: Jelicks Linda A. , Paul Pradip K. , O'Byrne Elizabeth , Gupta Raj K. 
Published: March 2007

AbstractViable bovine nasal cartilage was examined with magnetic resonance (MR) spectroscopy. Digestion of the proteoglycan matrix by papain or trypsin was accompanied by substantial changes in carbon‐13, sodium‐23, and hydrogen‐1 MR spectra and relaxation parameters, with C‐13 MR spectra showing the most pronounced changes. These results indicate the potential of MR spectroscopy (and imaging) for noninvasive evaluation of cartilage disease and monitoring of patients with degenerative joint diseases.
Noise reduction in three‐dimensional phase‐contrast MR velocity measurementsl
Authors: Song Samuel M. , Napel Sandy , Glover Gary H. , Pelc Norbert J. 
Published: March 2007

AbstractThe authors have developed a method to reduce noise in three‐dimensional (3D) phase‐contrast magnetic resonance (MR) velocity measurements by exploiting the property that blood is incompressible and, therefore, the velocity field describing its flow must be divergence‐free. The divergence‐free condition is incorporated by a projection operation in Hilbert space. The velocity field obtained with 3D phase‐contrast MR imaging is projected onto the space of divergence‐free velocity fields. The reduction of noise is achieved because the projection operation eliminates the noise component that is not divergence‐free. Signal‐to‐noise ratio (S/N) gains on the order of 15%‐25% were observed. The immediate effect of this noise reduction manifests itself in higher‐quality phase‐contrast MR angiograms. Alternatively, the S/N gain can be traded for a reduction in imaging time and/or improved spatial resolution.
Correlation of cine MR velocity measurements in the internal carotid artery with collateral flow in the circle of willis: Preliminary study
Authors: Davis Wayne L. , Turski Patrick A. , Gorbatenko Kristina G. , Weber David 
Published: March 2007

AbstractThe velocity‐phase relationship intrinsic to phase‐contrast magnetic resonance (MR) angiography permits the quantitative and qualitative assessment of blood flow. The ability to measure velocity and vessel cross‐sectional area allows noninvasive assessment of volume flow rate (VFR) in the internal carotid artery (ICA). Phase‐contrast techniques also demonstrate flow direction. Using two‐dimensional cine phase‐contrast angiography, the authors evaluated VFR in the ICA and collateral flow about the circle of Willis in 15 patients with ischemic neurologic symptoms. The VFR in each carotid artery was correlated with the degree of stenosis and presence or absence of abnormal circle of Willis collateral flow. There was a correlation between a decrease in VFR and abnormal circle of Willis collateral flow. In addition, a correlation between severe stenosis and a decrease in VFR was found. In patients with ischemic neurologic symptoms without severe stenosis (<70% diameter stenosis), no decrease in VFR was seen. It is hoped that flow quantification and directional flow imaging with phase‐contrast angiography will help further characterize carotid artery occlusive disease by enabling assessment of VFR changes associated with ischemic neurologic symptoms. This study also supports the hypothesis that two mechanisms‐hemodynamic and embolic‐play a role in ischemic neurologic symptoms.
Three‐dimensional MR imaging and display of intracranial disease: Improvements with the MP‐RAGE sequence and gadolinium
Authors: Brant‐Zawadzki Michael N. , Gillan Gary D. , Atkinson Dennis J. , Edalatpour Nasrola , Jensen Maureen 
Published: March 2007

AbstractThree‐dimensional (3D) image rendering was performed in 14 patients who had undergone magnetic resonance (MR) imaging for focal brain lesions. The MR study included the magnetization‐prepared rapid gradient‐echo (MP‐RAGE) sequence with 64 or 128 partitions. Resultant contiguous sections 2.5 or 1.25 mm thick, respectively, were obtained. Images were acquired before and after administration of gadopen‐letate dimeglumine. Resultant 3D data sets were processed on a commercially available workstation. Correlative surgical observation was performed in four cases. All data sets were successfully processed into 3D images. The precontrast images proved superior to gadolinium‐enhanced images for brain surface rendering. Postcontrast images proved superior for reconstruction of tumors and vascular structures. The 64‐partition data set proved sufficient for all postprocessing. Coronal orientation was preferred to sagittal orientation for surface rendering because it provided optimal orthogonal orientation of sulcal and gyral brain surface features. Three‐dimensional rendition allowed easy superposition of lesion, brain, vessels, and scalp features‐all useful for surgical planning. The central sulcus was easily recognized in the mid‐line partitions and traced mediolaterally for projection on the cortical surface. MP‐RAGE provides a 3D data set that can be obtained in just over 3 minutes, from which clinically useful 3D renderings are possible. The rapidity of acquisition and capability for 3D rendering provides additional clinical utility.
MR imaging of knee hyaline cartilage: Evaluation of two‐ and three‐dimensional sequences
Authors: Tervonen Osmo , Dietz Mark J. , Carmichael Stephen W. , Ehman Richard L. 
Published: March 2007

AbstractMagnetic resonance (MR) imaging of cadaveric knees was performed to determine optimal sequences for visualization of hyaline cartilage. Full‐thickness cartilage lesions ranging in diameter from 1 to 5 mm and a partial‐thickness cartilage lesion 15 mm in diameter were created in the femoral articular surfaces of three cadaveric knees. The knees were then imaged with a 1.5‐T imager with various two‐dimensional and high‐resolution three‐dimensional (3D) techniques. After imaging, the knee specimens were sectioned for evaluation. Measurements of cartilage thickness in fast spin‐echo images correlated best with those in the gross specimen. Diffuse areas of cartilage thinning were also most accurately identified with fast spinecho images. Small, focal cartilage defects were best delineated in 3D SPGR (spoiled GRASS [gradient‐recalled acquisition in the steady state]) images.
Phase‐correction method for reduction of B0 instability artifacts
Authors: Foo Thomas K. F. , Hayes Cecil E. 
Published: March 2007

AbstractView‐to‐view phase shifts due to B0 instability are corrected by applying a phase correction to the low‐spatial‐frequency views. The algorithm described herein assumes that the signal intensity in the space outside of an object represents only noise. A set of phases for the low‐spatial‐frequency views are calculated by minimizing, in the image, the intensity of the induced artifacts in the space outside of the object.
Relative charaterisitics of MR angiography and competing vascular imaging modalities
Authors: Mistretta Charles A. 
Published: March 2007

AbstractThis article reviews the general characteristics of several vascular imaging modalities with the purpose of identifying the distinguishing features of magnetic resonance (MR) angiography. Brief discussions of conventional x‐ray film angiography, intravenous and intraarterial digital subtraction angiography (DSA), duplex and color Doppler flow ultrasound (US), computed tomographic (CT) angiography, transesophageal and intravascular US, angioscopy, and MR angiography are presented. The advantages and disadvantages of each are discussed. The general attributes and image quality features of MR angiography, intraarterial DSA, CT angiography, and US are compared. It is concluded that no single imaging modality will presently suffice for all purposes. Because of its noninvasiveness, rapidly improving image quality, and ability to directly provide velocity information, MR angiography is likely to play a role in an increasing number of clinical applications.
Flow velocity quantification in human coronary arteries with fast, breath‐hold MR angiography
Authors: Edelman Robert R. , Manning Warren J. , Gervino Ernest , Li Wei 
Published: March 2007

AbstractMeasurement of coronary artery flow velocities has, until now, largely required the use of invasive technologies. The authors have implemented a breath‐hold magnetic resonance (MR) angiography technique for depicting the coronary arteries and for quantifying flow velocities. The method was tested in flow phantoms and then applied to a series of subjects: 11 subjects were studied at rest, and four were studied before and during pharmacologic stress induced by intravenous adenosine. Flow velocities at rest in the midportion of the right coronary artery were 9.9 cm/sec ± 3.5 (n = 12); in the proximal left anterior descending coronary artery, they were significantly higher, measuring 20.5 cm/sec ± 5.2 (n = 6). With adenosine, flow velocities typically increased at least fourfold. The authors conclude that noninvasive measurement of coronary artery flow velocities is feasible with MR angiography; this method may prove useful for determining the physiologic significance of coronary artery stenosis.
MR imaging of silicone gel–filled breast implants in vivo with a method that visualizes silicone selectively
Authors: Mukundan Srinivasan , Thomas W. Dixon , Kruse Beth D. , Monticciolo Debra L. , Nelson Rendon C. 
Published: March 2007

AbstractThe lack of an adequately sensitive method for detecting silicone leakage and reported serious complications due to silicone leakage were cited as justification by the U.S. Food and Drug Administration for imposing the current restrictions on silicone gel–filled breast prostheses. The authors report a new magnetic resonance imaging method for visualizing silicone leakage: the silicone‐only sequence (SOS). The method uses the conventional STIR (short‐inversion‐time inversion‐recovery) technique combined with a 1331 radio‐frequency pulse train widely used for water suppression in spectroscopy. With the SOS, silicone can be imaged while signals from fat and water are suppressed. The authors used the SOS to image phantoms and normal and ruptured silicone gel–filled breast prostheses.
Susceptibility effects in porous media in the presence of flow
Authors: Su Min‐Ying , Nalcioglu Orhan 
Published: March 2007

AbstractMagnetic resonance (MR) imaging of microvascular flow is an important topic in biomedicine because it permits access to the functional state of a biologic system. The internal heterogeneous magnetic field due to susceptibility differences within tissues is one of the factors that can affect signal intensity. A glass bead phantom simulating a porous medium was used to experimentally study the effect of the internal magnetic field on MR flow measurements. A physical model was developed to simulate the paths of the moving spins and the local magnetic field distribution in the medium to estimate the signal intensity with spin‐phase analysis. The susceptibility variation inside the glass bead phantom was estimated by comparing the simulation results with the experimental data. Experiments were also performed with a tissue‐simulating phantom, and the results indicated that the effect of the internal field inhomogeneity on in vivo microvascular flow measurements was negligible.
Acute spinal ligament disruption: MR imaging with anatomic correlation
Authors: Kliewer Mark A. , Gray Linda , Paver Jacqueline , Richardson William D. , Vogler James B. , McElhaney James H. , Myers Barry S. 
Published: March 2007

AbstractDisruption of spinal ligaments can lead to instability that jeopardizes the spinal cord and nerve roots. Magnetic resonance (MR) imaging can directly image spinal ligaments; however, the sensitivity with which this modality demonstrates ligament injury has, to the authors' knowledge, not been reported. On a biomechanical testing machine, 28 cadaveric spines were subjected to controlled injury that resulted in ligament tears. The spines were then imaged with plain radiography, computed tomography, and MR imaging (1.5 T). The images were analyzed for evidence of ligament injury before dissection of the specimen. Forty‐one of 52 (79%) ligament tears of various types were correctly identified at MR imaging. Disruptions of the anterior and posterior longitudinal ligaments were most conspicuous and were detected in all seven cases in which they were present (no false‐positive or false‐negative results); disruptions of the ligamentum flavum, capsular ligaments, and interspinous ligaments could also be identified but less reliably (three false‐positive and 11 false‐negative results). That MR imaging can reliably and directly allow assessment of spinal ligament disruption in this in vitro model suggests its potential utility for this assessment in patients.
Applications of reduced‐encoding MR imaging with generalized‐series reconstruction (RIGR)
Authors: Webb Andrew G. , Liang Zhi‐Pei , Magin Richard L. , Lauterbur Paul C. 
Published: March 2007

AbstractThe RIGR (reduced‐encoding imaging by generalized‐series reconstruction) technique for magnetic resonance imaging uses a high‐resolution reference image as the basis set for the reconstruction of subsequent images acquired with a reduced number of phase‐encoding steps. The technique allows increased temporal resolution in applications requiring repeated acquisitions, such as the dynamic imaging of contrast agent biodistribution, and in intrinsically time‐consuming protocols such as the acquisition of a series of T2‐weighted images. Several examples are presented to demonstrate that a four‐ to eightfold improvement in spatial or temporal resolution can be achieved with this technique.
T1, T2, and concentrations of brain metabolites in neonates and adolescents estimated with H‐1 MR spectroscopy
Authors: Toft Peter B. , Christiansen Pernille , Pryds Ole , Lou Hans C. , Henriksen Ole 
Published: March 2007

AbstractThe protein and lipid content of the human brain increases dramatically from infancy to adolescence. The authors investigated whether this change influences the relaxation behavior of metabolites measurable with hydrogen‐1 magnetic resonance (MR) spectroscopy. H‐1 MR spectroscopy was performed in eight neonates and eight adolescents at 1.5 T with STEAM (stimulated‐echo acquisition mode) sequences. Five spectra were obtained in each volume of interest with different TE and TR values. T1 and T2 were subsequently calculated. T1 and T2 for inositols, choline‐containing compounds (Cho), phosphocreatine plus creatine (PCr + Cr), and N‐acetylaspartate (NAA) did not differ significantly between the two subject groups. Metabolite concentrations were estimated by using the fully relaxed water signal as an internal standard. Mean estimated concentrations of NAA and PCr + Cr were higher in the adolescent group, whereas the concentration of Cho was lower. The concentration of inositols was similar in the two groups.
Effect of MR imaging on the normal human pineal body: Measurement of plasma melatonin levels
Authors: Schiffman Jonathan S. , Lasch Hugh M. , Rollag Mark D. , Flanders Adam E. , Brainard George C. , Burk D. Lawrence 
Published: March 2007

AbstractProduction of melatonin, a hormone synthesized and secreted by the pineal body, has been suppressed by electromagnetic fields in some but not all animal studies. Magnetic resonance (MR) imaging at 1.5 T was evaluated for its ability to modulate the level of melatonin in eight male volunteers. Subjects were exposed to three conditions, respectively, between 1:00 and 2:00 AM on different nights: (a) a series of routine MR pulse sequences for brain imaging in dark conditions, (b) dark control conditions, and (c) bright‐light contro conditions. Plasma was analyzed for melatonin and cortisol levels. Hormonal changes were analyzed by one‐factor repeated measures within‐subject analysis of variance. These conditions were associated with significant differences in melatonin levels: F(2,6) = 7.95 and P =.021. Subjects exposed to darkness showed a typical increase in melatonin concentration. Subjects exposed to bright light showed a characteristic suppression of melatonin concentration. Those exposed to the MR imaging fields showed an increase in melatonin level similar to that seen in the dark control condition. Light and MR imaging had no significant effects on cortisol levels. Thus, MR imaging at field strengths known to modulate melatonin levels in rats did not suppress melatonin production in human subjects.
MR angiography of congenital heart disease: Value of segmented two‐dimensional inflow technique and maximum‐intensity‐projection display
Authors: Seelos Klaus C. , Smekal Alexander Von , Steinborn Marc , Gieseke Jürgen , Redel Dierk A. , Reiser Maximilian 
Published: March 2007

AbstractMagnetic resonance (MR) angiography of the cardiovascular system was evaluated in 41 patients with congenital heart disease by using a two‐dimensional (2D) inflow technique based on a magnetization‐prepared gradient‐echo pulse sequence with segmented k‐space data acquisition and electrocardiographic gating at 0.5 T. Inversion and saturation prepulses were used to suppress stationary tissue and enhance intravascular signal. Presaturation slabs were applied where certain vascular structures had to be suppressed. Sequence parameters were optimized by evaluating signal intensity and contrast characteristics for various flip angles and inversion and saturation delay times. The heart and intrathoracic vasculature were encompassed with 40–50 overlapping sections. Both 2D angiograms and maximum‐intensity‐projection images were evaluated. Combining data sets acquired in the sagittal and transverse orientations provided the most satisfactory information about the pulmonary arteries. The highest signal‐to‐noise ratios were obtained with a flip angle of 65° and short prepulse delay times. Two‐dimensional MR angiography can provide useful diagnostic information but requires a thorough understanding of in‐plane and hemodynamically induced signal intensity changes.
Carotid and vertebral artery blood flow in left‐ and right‐handed healthy subjects measured with MR velocity mapping
Authors: Bogren Hugo G. , Buonocore Michael H. , Gu Wei‐Zhong 
Published: March 2007

AbstractThe goal of the study was to establish normal carotid artery flow rates in left‐handed and right‐handed individuals as a standard against which patients with carotid artery disease could be compared. Antegrade and retrograde flow were measured in the ascending aorta, in the right and left common, internal, and external carotid arteries, and in the vertebral arteries of 12 healthy subjects. Five subjects were right‐handed, five left‐handed, and two ambidextrous. Measured flow rates were as follows: common carotid arteries, 360–557 mL/min (mean [± standard deviation], 465 mL/min ± 52); internal carotid arteries, 132–367 mL/min (mean, 265 mL/min ± 60); external carotid arteries, 113–309 mL/min (mean, 186 mL/min ± 51); vertebral arteries from 133–308 mL/min (mean, 244 mL/min ± 43); and cerebral circulation, 546–931 mL/min (mean, 774 mL/min ± 134). All right‐handed subjects had higher flow rates in the left internal carotid artery than in the right, and all left‐handed subjects had higher flow rates in the right internal carotid artery (P =.007). There were no significant differences in left and right common carotid artery flow rates between left‐ and right‐handed subjects. The standard deviation of a single measurement was 5%. The flow rates were similar to those obtained previously with other techniques and could be used as a normal standard.
Tissue temperature monitoring for thermal interventional therapy: Comparison of T1‐weighted MR sequences
Authors: Matsumoto Reiko , Mulkern Robert V. , Hushek Stephen G. , Jolesz Ferenc A. 
Published: March 2007

AbstractFor thermal interventional therapy, near real‐time monitoring of temperature changes in the treated area is desirable. In this study, various fast T1‐weighted magnetic resonance (MR) imaging protocols were compared to determine the sensitivity and resolution of signal intensity for temperatures within the range of 36°C–66°C in gel phantoms and in vitro porcine liver specimens. The results showed that a T1‐weighted fast spin‐echo sequence with a TR of 100 msec had better temperature sensitivity and resolution than other sequences with comparable temporal resolutions. The longer imaging times required for fast spin‐echo sequences with a TR of 300 msec did not improve temperature sensitivity. The methods introduced to evaluate temperature sensitivity and resolution should prove useful in selecting appropriate MR protocols for monitoring thermal treatment modalities such as interstitial laser therapy, focused ultrasound therapy, or radio‐frequency heating.
Hematopoietic reconstitution after bone marrow transplantation: Assessment with MR imaging and H‐1 localized spectroscopy
Authors: Schick Fritz , Einsele Hermann , Kost Renate , Duda Stephan , Jung Wulf‐Ingo , Lutz Otto , Claussen Claus D. 
Published: March 2007

AbstractMagnetic resonance (MR) studies were performed in 14 patients as early as possible (21–110 days) after bone marrow transplantation (BMT). MR characteristics of lumbar vertebral bone marrow were studied with T1‐weighted spin‐echo imaging, water‐ and fatselective imaging with a frequency‐selective excitation technique, and point‐resolved spatially localized proton spectroscopy. Signals from water and fat protons and their T1 and T2 values were analyzed. Water proton signal intensity correlated well with cellularity within bone marrow, as determined with parallel iliac crest biopsies. The fraction of signal from water in red bone marrow of patients with allogeneic transplants from siblings (four cases) was significantly higher than in four patients with autologous transplants. The latter showed very low cellularity in the period of about 4 weeks after BMT because of the cytotoxic pretreatment of the bone marrow. The MR results in six patients with allogeneic transplants from unrelated donors ranged widely, depending on the complications after BMT. Analysis of data obtained with the different techniques showed that water‐ and fat‐selective MR imaging and spectroscopic methods are useful for noninvasive monitoring of hematopoietic reconstitution after BMT.
MR Angiographic guidance for transjugular intrahepatic portosystemic shunt procedures
Authors: Müller Markus F. , Siewert Bettina , Stokes Kenneth R. , Lewis W. David , Jenkins Roger L. , Stehling Michael K. , Finn J. Paul 
Published: March 2007

AbstractThe authors used magnetic resonance (MR) angiography to guide catheter placement in transjugular intrahepatic portosystemic shunt (TIPS) procedures in nine of 18 patients and compared the results with those of the nine patients for whom prior planning based on MR angiography was not done. Two‐dimensional time‐of‐flight MR venography was performed during breath hold, and projection venograms were formatted in sagittal, coronal, and axial planes. MR angiography defined venous anatomy sufficiently to shorten the procedure and help minimize invasiveness. With MR angiographic guidance, intrahepatic needle punctures were significantly fewer (without MR guidance: mean, 12.1; with MR guidance: mean, 3.6; P < 0.001) and associated complications were absent (without MR guidance: failed placement, n = 1; bleeding requiring blood transfusions, n = 1; death due to intraperitoneal hemorrhage with hemobilia, n = 1; and death due to hepatic capsular perforation, n = 1). The average time for the procedure was 2.9 hours without MR angiographic guidance and 1.8 hours with MR angiographic guidance (P < 0.001). The authors conclude that MR angiography is a useful technique for defining portal and hepatic venous anatomy before the TIPS procedure and that planning based on MR angiography may decrease the difficulty and length of the procedure.