bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short TE hydrogen‐1 spectroscopic MR imaging of normal human brain: Reproducibility studies
Authors: Jackson Edward F. , Doyle Timothy J. , Wolinsky Jerry S. , Narayana Ponnada A. 
Published: March 2007

AbstractStudies have been performed to evaluate the reproducibility of longitudinal acquisitions with short TE spectroscopic magnetic resonance (MR) imaging of human brain. In healthy volunteers, the ratios of N‐acetyl‐aspartate (NAA) and choline (Cho) with respect to total creatine (Cr) (creatine and phosphocreatine) have been examined in terms of voxel‐to‐voxel, acquisition‐to‐acquisition, and subject‐to‐subject variation. Overall coefficients of variation for NAA/Cr ratios and Cho/Cr ratios were 18% and 16%, respectively. The interacquisition variation was not statistically significant (P = .05) for either ratio. In terms of F ratios, the dominant source of variation in the NAA/Cr ratio was intersubject variability, whereas for the Cho/Cr ratio the dominant source of variation was intervoxel variability. Consequences of spectroscopic processing with spatial apodization and postacquisition water suppression and resolution enhancement were also examined. Such reproducibility studies are crucial if longitudinal spectroscopic evaluations are to be performed in a clinical setting to follow the natural course of disease states or the effects of therapy.
Nodular sarcoidosis of the liver and spleen: Appearance on MR images
Authors: Warshauer David M. , Semelka Richard C. , Ascher Susan M. 
Published: March 2007

AbstractSmall nodular lesions in the liver and spleen have been reported as an infrequent manifestation of sarcoidosis. Five patients with this appearance on either dynamic contrast material—enhanced computed tomographic (CT) or ultrasound scans underwent magnetic resonance (MR) imaging with and without dynamic gadolinium enhancement. The lesions were relatively uniform in size, ranging from 0.5 to 1.5 cm. On CT scans, they were hypoattenuating relative to surrounding parenchyma. On MR images, the lesions were hypointense relative to background parenchyma with all sequences. No substantial enhancement was observed in the lesions, although lesion conspicuity decreased over time on serial postcontrast images. Lesion conspicuity was greatest on either T2‐weighted fat‐suppressed (T2FS) images or early‐phase dynamic contrast‐enhanced images. Abdominal adenopathy was seen in three of the five patients and was hyperintense relative to liver on T2FS images in two and intermediate in intensity in one patient.
Stress MR imaging for evaluation of popliteal artery entrapment
Authors: Cesare Ernesto Di , Marsili Luca , Marino Giovanni , Masciocchi Carlo , Morettini Giuseppe , Spartera Carlo , Lupattelli Luciano , Passariello Roberto 
Published: March 2007

AbstractThe popliteal artery entrapment (PAE) syndrome has been recognized as a cause of arterial occlusion in young people. It is the result of an anomaly of the relationship between the popliteal artery and the gastrocnemius muscle. Eight young healthy volunteers (16 legs) and six patients (10 legs) with suspected PAE underwent magnetic resonance (MR) imaging. Gradient‐echo images were obtained in axial planes with the leg at rest and during active plantar flexion against resistance. Imaging at rest allowed identification of PAE signs in only one leg, which had an anomalous medial course of the popliteal artery. In the other cases, only the stress technique was able to show signal loss in the popliteal artery due to muscular compression (two legs) or the presence of accessory muscle slip around the vessel (two legs), as confirmed at surgery. MR imaging is therefore a useful technique for the diagnosis of PAE because of its capability of combining information obtainable with other modalities.
Fragrance administration to reduce anxiety during MR imaging
Authors: Redd William H. , Manne Sharon L. , Peters Bruce , Jacobsen Paul B. , Schmidt Hilary 
Published: March 2007

AbstractFifty‐seven outpatients received either heliotropin (a vanillalike scent) with humidified air (n = 20) or humidified air alone (n = 37) via a nasal cannula during magnetic resonance imaging in the diagnostic workup for cancer. Delivery of heliotropin and air was determined by a computer‐controlled schedule. Fragrance administration resulted in a statistically significant reduction in average overall patientrated anxiety (on a visual analog scale) during imaging in patients who found the fragrance moderately to extremely pleasant. Administration of fragrance was associated with 63% less anxiety than administration of humidified air alone. Physiologic measures (pulse and heart rate) did not show a statistically significant effect with fragrance administration.
Reproducibility of nonparametric feature map segmentation for determination of normal human intracranial volumes with MR imaging data
Authors: Jackson Edward F. , Narayana Ponnada A. , Falconer James C. 
Published: March 2007

AbstractSemiautomated segmentation of dual‐contrast magnetic resonance images was used to determine volumes of total brain, gray matter, white matter, and cerebrospinal fluid (CSF) in healthy volunteers. Reproducibility of the technique was evaluated in terms of intraobserver, interobserver, and study‐to‐study variations. Intraobserver coefficients of variation ranged from 0.4% to 6.0%, while interobserver values ranged from 0.8% to 9.9%. In both cases, the maximum variations were obtained in volume measurements of tissues with maximum complexity (ie, CSF), and the minimum variation was obtained in determining total brain volume. This was also true in the case of study‐to‐study variations in volume measurements, for which the coefficients of variation ranged from 0.5% to 8.7%. The use of appropriate preprocessing techniques, which are crucial to the accuracy and reproducibility of the segmentation technique, are described in detail.
In vivo comparison of two through‐plane MR velocity mapping methods: Fast fourier encoding and phase mapping
Authors: Mousseaux Elie , Idy‐Peretti Iiana , Bittoun Jacques , Jolivet Odile , Bourroul Eric , Tardivon Anne , Péronneau Pierre , Gaux Jean‐Claude 
Published: March 2007

AbstractMagnetic resonance imaging maps of velocity were acquired with a 1.5‐T system in 10 subjects in a plane perpendicular to the main pulmonary artery. Velocity images were successively acquired with a method developed from Fourier‐encoding velocity imaging (FEVI) principles with eight gradient steps and one excitation, and with two‐point phase‐subtraction mapping. Reconstruction in FEVI was implemented by zero‐filling interpolation around the eight gradient steps and then around the four central steps. The methods were compared by using estimates of noise in velocity measurements based on the difference between the experimental map and a smooth fitted map. For the same acquisition time, FEVI with four encoding steps was more precise in velocity measurements than phase mapping. Precision was further increased by the use of eight encoding steps, but acquisition time was doubled.
Reduction of partial‐volume artifacts with zero‐filled interpolation in three‐dimensional MR angiography
Authors: Du Yiping P. , Parker Dennis L. , Davis Wayne L. , Cao Guang 
Published: March 2007

AbstractPartial‐volume artifacts reduce vessel contrast and continuity (especially in small vessels) in magnetic resonance (MR angiography. The authors applied zero‐filled (band‐limited) interpolation to three‐dimensional (3D) MR angiograms to reduce partial‐volume artifacts. They demonstrated that zero‐filled interpolation can also be implemented by means of voxel shifting in real space. Voxel‐shifted interpolation is much less computer memory intensive than conventional zero‐filled interpolation. They numerically simulated the contrast loss due to partial‐volume artifacts and contrast recovery obtained with zero‐filled interpolation. Zero‐filled interpolation in all three orthogonal directions was applied to 3D MR angiography data sets from 29 human studies. These studies were obtained with the three commonly used 3D MR angiography techniques: 3D time of flight, multislab 3D time of flight, and 3D phase contrast. A substantial improvement in vessel contrast and vessel continuity was observed in all cases.
Guidelines and recommendations for MR imaging safety and patient management III. Questionnaire for screening patients before MR procedures
Authors: Shellock Frank G. , Kanal Emanuel ,   SMRI Safety Committee
Published: March 2007

AbstractThe authors present the third installment of the guidelines and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (now the Society of Magnetic Resonance) concerning various issues related to the safety and management of patients undergoing magnetic resonance (MR) procedures. This document was developed to provide standardized and consistent information for use by health practitioners involved in screening patients or other individuals for MR procedures.
Effect on fetal mouse development of exposure to MR imaging and gadopentetate dimeglumine
Authors: Rofsky Neil M. , Pizzarello Donald J. , Weinreb Jeffrey C. , Ambrosino Michael M. , Rosenberg Carl 
Published: March 2007

AbstractPregnant mice were exposed to one of five regimens at 9.5 days of gestation: no treatment (group 1), intraperitoneal injection of normal saline (group 2), intraperitoneal injection of gadopentetate dimeglumine (group 3), intraperitoneal injection of gadopentetate dimeglumine and magnetic resonance (MR) exposure (group 4), and MR exposure alone (group 5). At 18 days of gestation, the mice were sacrifice and fetuses were removed and examined for the following end points: litter size, number alive or dead, fetal weight, extremity morphology, eye and ear development, and appearance of the head. A total of 739 fetuses were analyzed: group 1 (n = 161), group 2 (n = 149), group 3 (n = 142), group 4 (n = 136), and group 5 (n = 151). The only statistically significant difference was a lower mean fetal weight in the saline‐injection group compared with the control group. The results show that MR exposure with and without gadopentetate dimeglumine had no adverse effect on the end points analyzed.
Eddy current correction in volume‐localized MR spectroscopy
Authors: Lin Chen , Wendt Richard E. , Evans Harlan J. , Rowe Roger M. , Hedrick Thomas D. , LeBlanc Adrian D. 
Published: March 2007

AbstractThe quality of volume‐localized magnetic resonance spectroscopy is affected by eddy currents caused by gradient switching. Eddy currents can be reduced with improved gradient systems; however, it has been suggested that the distortion due to eddy currents can be compensated for during postprocessing with a single‐frequency reference signal. The authors propose modifying current techniques for acquiring the single‐frequency reference signal by using relaxation weighting to reduce interference from components that cannot be eliminated by digital filtering alone. Additional sequences with T1 or T2 weighting for reference signal acquisition are shown to have the same eddy current characteristics as the original signal without relaxation weighting. The authors also studied a new eddy current correction method that does not require a single‐frequency reference signal. This method uses two free induction decays (FIDs) collected from the same volume with two sequences with opposite gradients. Phase errors caused by eddy currents are opposite in these two FIDs and can be canceled completely by combining the FIDs. These methods were tested in a phantom. Eddy current distortions were corrected, allowing quantitative measurement of structures such as the –CHCH– component, which is otherwise undetectable.
Safety and optimum concentration of a manganese chloride–based oral MR contrast agent
Authors: Bernardino Michael E. , Weinreb Jeffrey C. , Mitchell Donald G. , Small William C. , Morris Marie 
Published: March 2007

AbstractTo determine the safety of a manganese chloride‐based oral magnetic resonance (MR) contrast agent and the ideal concentration of the agent for marking in three different anatomic sites (stomach, middle of the small bowel, and ileocecal region), six healthy volunteers were evaluated before and after administration of 900 mL of three different concentrations of the contrast agent. Images were evaluated subjectively and objectively. No adverse events were noted. There was a minimal rise in manganese blood levels at 6 hours after administration, with a return to baseline at 24 hours. The imaging data demonstrated good‐to‐excellent bowel marking on T1‐weighted images at all three concentrations. However, on T2‐weighted images, the 40 mg Mn+2/L concentration provided improved hypointense bowel marking relative to the 20 mg/L concentration. Little difference was seen between the 40 and 60 mg/L concentrations. Fast T1‐and T2‐weighted sequences provided superior image quality to that of conventional spin‐echo sequences.
MR imaging assessment of experimental hepatic dysfunction with mn‐DPDP
Authors: Coley Brian D. , Mattrey Robert F. , Baker Kristine G. , Peterson Thomas , Burgan Anthony R. 
Published: March 2007

AbstractManganese (II) N, N'‐dipyridoxylethylenediamine‐N, N'‐diacetate 5,5′‐bis(phosphate) (DPDP) is a paramagnetic magnetic resonance (MR) contrast agent that enhances the liver and is predominantly excreted through the biliary tree. The authors evaluated its utility in diffuse liver disease by assessing liver and gallbladder enhancement in 24 rabbits. Total (n = 6) or segmental (n = 6) biliary occlusion or galactosamine‐induced hepatitis (n = 6) was induced 3 days before imaging. Six rabbits served as normal controls. T1‐ and T2‐weighted axial MR images were acquired at baseline, followed by T1‐weighted images every 10 minutes for 1 hour after the intravenous administration of 20 μmol/kg Mn‐DPDP. Except for the segmental occlusion group, the baseline study did not allow distinction between normal and abnormal livers. The temporal hepatic enhancement pattern was statistically different for each group. The normal, segmental occlusion, and hepatitis groups showed patterns similar to one another but markedly higher signal intensity than the total‐occlusion group throughout the observation period. In contrast, the gallbladder showed a greater difference in both degree of enhancement and time to peak enhancement among the four groups. Mn‐DPDP produces a temporal hepatic enhancement pattern that allows recognition of markedly impaired livers, and gallbladder enhancement patterns that allow distinction of more subtly impaired livers.
Nonsusceptibility artifacts due to metallic objects in MR imaging
Authors: Camacho Christopher R. , Plewes Donald B. , Henkelman R. Mark 
Published: March 2007

AbstractThe authors investigated eddy current artifacts due to metallic objects within the magnetic resonance imaging field. The problem was simplified by using a circular copper loop as a model for the more complex eddy current pathways present in a metallic implant. With this simple geometry, the authors show that radio‐frequency (RF)‐induced eddy currents in the metal produce a significant local artifact. However, no appreciable artifacts due to the switching magnetic field gradients were observed. A detailed quantitative analysis of the mechanism of RF‐induced eddy current artifact due to the the copper loop was performed. The artifact was demonstrated experimentally to result from perturbations of the transmit and receive sensitivities of the RF coil. Theoretical calculations of these perturbations showed excellent agreement with experimental results. With an understanding of the artifact mechanism, methods for correcting the RF‐induced eddy current artifact were applied.
Mr angiography artifact due to metal joint of ventriculoperitoneal shunt mimicking severe carotid stenosis
Authors: Kuta A. John , Smoker Wendy R. K. , Cole Timothy J. , Beskin Robert R. 
Published: March 2007

AbstractAn artifact due to the metal joint of a ventriculoperitoneal shunt resulted in a diagnosis of severe internal carotid artery stenosis at magnetic resonance angiography. Conventional x‐ray angiography showed the presence of the metal joint and revealed that the artery was not stenotic.
Surface coil MR imaging of the human brain with an analytic reception profile correction
Authors: Moyher Susan E. , Vigneron Daniel B. , Nelson Sarah J. 
Published: March 2007

AbstractAn analytic correction method was developed and applied to correct the signal intensity nonuniformity caused by the inhomogeneous reception profile of surface coils used—because of their higher sensitivity—for magnetic resonance imaging of the brain at 1.5 T. The reception profile was analytically modeled by using the Blot–Savart law. The correction considerably improved visual interpretation of the images by modeling and removing the dependence of signal intensity on distance from the coil. The method can be used for single or multiple coils of any planar geometry and in any orientation. Application of this technique allows imaging of the brain with surface coils, yielding increased resolution and signal‐to‐noise ratio, without the penalty of image nonuniformity.
Unsuppressed fat in the right anterior diaphragmatic region on fat‐suppressed T2‐weighted fast spin‐echo MR images
Authors: Yoshimitsu Kengo , Varma Datla G. K. , Jackson Edward F. 
Published: March 2007

AbstractThe authors retrospectively evaluated magnetic resonance Images of the abdomen obtained In 52 consecutive patients. All cases included fast spinecho (FSE) T2‐weighted images acquired with a frequency‐selective fat saturation technique. All imaging was performed with a 1.5‐T unit. In 42 patients (81%), fat was not suppressed in the right anterior diaphragmatic region on the T2‐welghted FSE images with fat suppression. In 11 (26%) of these 42 patients, subcutaneous fat adjacent to the unsuppressed anterior diaphragmatic fat was well suppressed. Hence, the fat In the diaphragmatic region mimicked fluid or peritoneal implants. The cause of the artifact appears to be the juxtaposition of liver, fat, and lung parenchymal air within a small anatomic space, creating a localized inhomogeneity of the magnetic field and susceptibility effects. Radiologists should be aware of this phenomenon to prevent confusion of an artifact with fluid or neoplasms.
Vessel enhancement filtering in three‐dimensional MR angiography
Authors: Du Yiping P. , Parker Dennis L. , Davis Wayne L. 
Published: March 2007

AbstractFor a variety of reasons, small vessels have low signal Intensity in magnetic resonance angiography. When the vessel signal intensity is lower than the signal intensity of background tissues, these vessels tend not to be visible on maximum‐intensity‐projection images. The authors developed a nonlinear second‐difference spatial filtering technique that enhances the details of small vessels while suppressing both noise and uniform background tissue. Two similar nonlinear second‐difference filters are presented and compared with the linear Laplacian second‐difference filter. To evaluate the performance of these filters, they were applied to intracranial three‐dimensional time‐of‐flight MR angiographic data and the results compared with the vessel enhancement obtained with a simple second‐difference Laplacian filter and with magnetization transfer contrast (MTC) techniques. The comparisons demonstrated that nonlinear filtering and MTC techniques result in similar Improvement in small‐vessel visibility and apparent continuity. A quantitative comparison demonstrated that the improvement in the contrast‐to‐noise ratio is much greater with the nonlinear filters than the Laplacian filter.
Delineation of pancreas with MR imaging: Multiobserver comparison of five pulse sequences
Authors: Mitchell Donald G. , Winston Corrine B. , Outwater Eric K. , Ehrlich Saundra M. 
Published: March 2007

AbstractThe authors compared five magnetic resonance (MR) imaging pulse sequences for their ability to depict the pancreas in 59 patients, each evaluated with at least two of the five sequences. Focal pancreatic carcinomas were present in eight patients. The five sequences were T1‐weighted spin echo (T1‐SE), fat‐suppressed T1‐SE (T1‐FS). T1‐weighted gradient echo (T1‐GRE). T2‐weighted SE (T2‐SE), and T2‐weighted fast spin echo (T2‐FSE). Using repeated‐measures analysis, three blinded observers independently reviewed 198 separate MR imaging series and rated them on a 5‐point scale with regard to image quality and depiction of pancreatic borders and the number of sections containing pancreatic and common bile ducts. The most superior and most inferior sections containing pancreas were recorded for each sequence in each patient. The results were compared with analysis of variance, and interobserver agreement was measured with the intraclass correlation coefficient (ICC). For image quality, all sequences were rated good to excellent, with the T1‐SE sequence having the highest rating. For clarity of pancreatic borders, however, the T1‐FS sequence was rated significantly higher (P<.006) than the other sequences; the T2‐SE sequence was least satisfactory. Common bile and pancreatic ducts were seen in the most sections with the T2‐FSE sequence. There were no significant differences regarding identification of the most superior and inferior sections containing pancreas, and the ICC was high (.91–.97) for all sequences. For detecting focal carcinomas, no single pulse sequence was sufficient.
Multiparametric display of spin‐echo data from MR studies of brain
Authors: Alfano Bruno , Brunetti Arturo , Arpaia Margherita , Ciarmiello Andrea , Covelli Eugenic M. , Salvatore Marco 
Published: March 2007

AbstractA magnetic resonance (MR) image processing technique that uses a single color image for simultaneous presentation of spin‐echo information and its application to MR studies of the brain is described. Relaxation rate and proton‐density maps were calculated from 160 brain MR studies performed at 1.5 and 1.0 T with standard spin‐echo sequences. Maps were fused into single color images, with R1, R2. and proton density coded, respectively, by red, green, and blue. The possibility of standardizing the technique was evaluated. Comparative analysis of color and conventional MR images of white matter disease and brain tumors was performed to assess intra‐ and interob‐server variability. Unequivocal and reproducible chromatic characterization of normal brain structures and a variety of lesions was obtained. Intra‐and interobserver analysis showed that color images can be used as a diagnostic tool. The technique may provide a simplified and timesaving approach for interpretation and presentation of brain MR studies.
MR imaging of viscoelastic properties
Authors: Lewa Czeslaw J. , de Certaines Jacques D. 
Published: March 2007

AbstractMechanical waves in magnetic resonance imaging, which have been suggested for possible clinical applications, were analyzed with regard to imaging of the viscoelastic properties of large objects. The method is based on the Larmor frequency modulation caused by the application of mechanical waves. Possible clinical applications include all diseases that result in a change in the mechanical properties of biologic tissues (eg, atherosclerosis).