bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Fe‐HBED and Fe‐EHPG as hepatobiliary MR contrast agents
Authors: Hoener Betty‐Ann , Engelstad Barry L. , Ramos Emiliano C. , Macapinlac Homer A. , Price David C. , Johnson Thomas R. , White David L. 
Published: March 2007

AbstractThe authors studied the biodisposition and hepatobiliary transport of two potential magnetic resonance imaging contrast agents, the iron (III) chelates of N,N′‐bis(2‐hydroxybenzyl)ethylenediamine‐N,N′‐diacetic acid (HBED) and diastereomeric N,N′‐ethylenebis(2‐hydroxyphenylglycine) (EHPG). Fecal and urinary excretion (mean ± standard deviation), respectively, of FE‐59 over 7 days in rats given tracer doses of the contrast agents were 67% ± 2% and 22% ± 1% for Fe‐59‐HBED and 22% ± 2% and 26% ± 5% for Fe‐59‐EHPG. In bile duct‐cannulated rats given 0.05‐mmol/kg doses labeled with Fe‐59, 52% ± 8% of Fe‐59 from Fe‐59‐HBED but only 17% ± 3% of that from Fe‐59‐EHPG was excreted into the bile within 90 minutes. Bromosulfophtha‐lein, but not taurocbolate or oxyphenonium, was shown to compete with both agents for hepatobiliary transport. Enterohepatic recirculation of both agents was less than 1%.
Simultaneous acquisition of phase‐contrast angiograms and stationary‐tissue images with Hadamard encoding of flow‐induced phase shifts
Authors: Dumoulin Charles L. , Souza Steven P. , Darrow Robert D. , Pelc Norbert J. , Adams William J. , Ash Stephen A. 
Published: March 2007

AbstractA technique for the simultaneous acquisition of three‐dimensional phase‐contrast angiograms and stationary‐tissue images is described. Hadamard multiplexed encoding of flow information permits image acquisition times that are a third shorter than those of previous phase‐contrast methods. The encoding scheme described also enables differentiation of flow‐induced phase shifts from phase shifts due to resonance offset conditions such as field inhomogeneities and chemical shift. Display strategies that combine this phase information with the flow image are described.
Encoding strategies for three‐direction phase‐contrast MR imaging of flow
Authors: Pelc Norbert J. , Bernstein Matt A. , Shimakawa Ann , Glover Gary H. 
Published: March 2007

AbstractThree encoding strategies for the measurement of flow velocities in arbitrary directions with phase‐contrast magnetic resonance imaging are presented; their noise and dynamic range performance are compared by means of theoretical analysis and computer simulation. A six‐point measurement strategy is shown to be quite inefficient in terms of velocity variance per unit time. A simple four‐point method exhibits equal dynamic range; its noise depends on flow direction but on average is equal to that of the six‐point method. An alternate, balanced four‐point method has noise that is direction independent and has, depending on implementation, possibly lower noise levels. Either four‐point method is more efficient and is preferred over the six‐point approach.
MR image contrast at high field strength
Authors: Vinitski Simon , Griffey Richard H. 
Published: March 2007

AbstractThe T1 of soft tissues increases with magnetic field strength. Some tissue contrast may be diminished on high‐field‐strength magnetic resonance (MR) images when conventional TRs are used, because of altered T1 effects on the MR signals. This necessitates longer TRs in techniques that use long TRs, which prolongs the examination excessively. Behavior of macroscopic magnetization is governed by the Bloch equations. Therefore, T1 contributions to the MR signal can be modulated by means of both timing intervals and radio‐frequency pulses. The analytic solution to the Bloch equations allowed calculation of white matter/gray matter and gray matter/cerebrospinal fluid contrast in both spin‐echo and inversion‐recovery (IR) imaging. Rabbit brains (normal and tumor‐containing) were then imaged in vivo at 1.5 and 4.7 T. In addition, MR images of a human head were obtained at 4.O T. Experimental results supported the theoretical predictions that brain contrast on long TR spinecho or IR images increases with field strength. However, varying the excitation flip angle allowed optimization of the T1 contribution to the MR signals, improving image contrast and/or reducing examination time. Thus, the dependence of T1 on field strength determines the optimum choice of imaging techniques and parameters in a predictable fashion.
MR imaging of Hippel‐Lindau disease: Value of gadopentetate dimeglumine
Authors: Nelson David R. , Yuh William T. C. , Wazirim Mary H. , Ryals Tony J. , Sato Yutaka , Kao Simon C. S. , Hawes Donald R. , Williams Richard D. 
Published: March 2007

AbstractHippel‐Lindau disease is an autosomal dominant disorder characterized by tumors of the central nervous system and abdominal viscera. Frequent multisystem radiologic evaluation of persons at risk is desirable. Twenty‐seven patients with Hippel‐Lindau disease or a family history of the disease were examined with both unenhanced and gadopentetate dimeglumine‐enhanced magnetic resonance (MR) imaging to study the usefulness of the contrast medium in the evaluation of these patients. The MR studies were correlated with computed tomographic (CT) scans in seven patients and cerebral angiograms in five. Twelve patients had hemangioblastomas in the brain, and eight of these patients also had spinal cord lesions (most were multiple), well demonstrated with gadopentetate dimeglumine. Contrast‐enhanced MR imaging enabled detection of more central nervous system lesions and provided better delineation than unenhanced MR imaging, CT, or angiography. In addition, four patients with multiple renal cysts seen on CT scans and unenhanced MR images had enhancing lesions that were later proved to be renal cell carcinoma at angiography and/or surgery. Four patients had cystic lesions in the pancreas that did not enhance and were later proved to be pancreatic cysts. The authors conclude that gadopentetate dimeglumine‐enhanced MR imaging appears to be a useful method for evaluating and following up patients with Hippel‐Lindau disease.
Assessing response to therapy of spinal metastases with gadolinium‐enhanced MR imaging
Authors: Sugimura Kazuro , Kajitani Akiko , Okizuka Hiromi , Sugihara Masaki , Mizutani Masami , Ishida Tetsuya 
Published: March 2007

AbstractThe utility of gadolinium‐enhanced magnetic resonance (MR) imaging in assessing the response of spinal metastases to therapy was evaluated. Fifteen patients (62 affected vertebral bodies) with spinal metastases were evaluated with gadopentetate dimeglumineenhanced imaging before and after irradiation or chemotherapy. Signal intensities of the lesions and of adjacent normal vertebral bodies were compared. Before therapy, metastatic foci enhanced significantly more than did normal vertebral bodies. After therapy, the lesions were divided into 37 responding lesions (group 1) and 25 nonresponding lesions (group 2). In group 1, lesion enhancement diminished considerably and the patients with these lesions remained clinically asymptomatic for 2–6 months. In group 2, lesion enhancement did not diminish much, and the difference between the groups was significant. Gadolinium‐enhanced MR imaging may thus be a useful method for assessing the effectiveness of therapy for spinal me. tastases.
TE interleaving: New multisection imaging technique
Authors: Bishop Jonathan E. , Plewes Donald B. 
Published: March 2007

AbstractA new pulse sequence that increases the number of sections that can be acquired with a T2‐weighted multisection imaging prescription is presented. The sequence achieves a higher efficiency in section acquisition per unit time by interleaving excitation and data collection for up to three separate sections during the long TE (⩾ 80 msec) of a T2‐weighted spin‐echo pulse sequence. The necessary modifications of the section‐select and readout gradient waveforms for the implementation of TE‐interleaved (TEI) sequences, with and without flow compensation, are described. Secondary‐ and stimulated‐echo artifacts are present on some TEI images, but these can be controlled with appropriate spoiler gradients. The signal‐to‐noise ratio for contiguous sections is slightly reduced compared with that of a standard multisection pulse sequence. These observations indicate that the effects of radio‐frequency section interference are enhanced by the TEI sequence.
MR imaging of poststenotic flow phenomena: Experimental studies
Authors: Krug Barbara , Kugel Harald , Friedmann Gerd , Bunke Juergen , van Dijk Peter , Schmidt Rainer , Hirche Hans Juergen 
Published: March 2007

AbstractPoststenotic flow patterns were analyzed in a flow phantom with a 1.5‐T magnetic resonance (MR) imager, with use of different MR imaging and MR angiographic pulse sequences. Spin‐echo, fast field‐echo, two‐dimensional inflow (multiple single‐section technique), and flow‐adjusted‐gradient sequences were applied. For the spin‐echo sequences, modulus and phase images were reconstructed from each data set. The length of the region of poststenotic changes in signal amplitude and phase measured at a constant flow rate increased with stenosis grade. Likewise, the length of the region of poststenotic changes measured at a constant stenosis grade increased with flow rate. Moreover, the results depended on the alignment of the flow direction with the readout gradient. Comparison of modulus and phase images allowed discrimination of turbulent and nonturbulent flow, which yields additional information on stenosis grade in clinical MR angiography.
Theoretical aspects of motion sensitivity and compensation in echo‐planar imaging
Authors: Duerk Jeffrey L. , Simonetti Orlando P. 
Published: March 2007

AbstractMagnetic resonance (MR) imaging can be performed on or below the time scale of most anatomic motion via echo‐planar imaging (EPI) techniques and their derivatives. The goal is to image rapidly and reduce artifacts that typically result from view‐to‐view changes in the spatial distribution of spins due to motion. However, the required time‐dependent magnetic field gradient waveforms remain sensitive to the dephasing effects of motion. Sources of motion artifact are simulated for spins moving along the imaging axes and are shown to be an important source of reduced image quality in EPI. A novel method of EPI is proposed that (a) refocuses single or multiple derivatives of motion at all echoes and (b) prevents accumulation of velocity (or higher derivative)‐induced dephasing along the phase‐encoding axis by moment nulling all phase‐encoding‐step waveforms about a single instant of time. Theoretical EPI sequences with considerable reductions in ghosts, blurring, and signal loss due to motion sensitivity are produced and compared with other EPI methods. Their time efficiency is presented as a function of available (relative) gradient strength for a variety of sequence waveforms.
MR imaging of normal rat brain at 0.35 T and correlated histology
Authors: Fiel Robert J. , Alletto James J. , Severin Charles M. , Nickerson Peter A. , Acara Margaret A. , Pentney Roberta J. 
Published: March 2007

AbstractA custom‐built small‐animal transceiver was used for in vivo imaging of normal rat brain at 0.35 T, with the objective of identifying anatomic components by comparison of images with corresponding histologic sections. The cerebrum, cerebellum, brain stem, ventricles, hippocampus, and subarachnoid space were identified and cerebrospinal fluid (CSF) was differentiated from gray matter and white matter on coronal and transaxial magnetic resonance (MR) images. These images compare favorably with those obtained by others at higher field strengths in regard to delineating major neuroanatomic structures. It is concluded that this technique will be useful for investigating smallanimal models of human neurologic disease involving morphologic and morphometric changes in gray matter, white matter, and CSF‐filled spaces.
Endorectal surface coil MR imaging of prostatic carcinoma with the inversion‐recovery sequence
Authors: Parivar Farhad , Rajanayagam Vasanthan , Waluch Victor , Eto Ross T. , Jones Lawrence W. , Ross Brian D. 
Published: March 2007

AbstractThe value of inversion‐recovery (IR) sequences in the diagnosis and staging of prostatic carcinoma with magnetic resonance (MR) imaging was studied. Twenty‐six patients with carcinoma of the prostate were imaged at 1.5 T with an endorectal surface coil and with a variety of IR sequences and a set of spin‐echo (SE) sequences for comparison. Ex vivo prostate specimens were imaged again at the same field strength. The two images were correlated with histologic sections. Cancer was identified with MR imaging in 96% of patients. Of the tumors more than 4 mm in diameter, 87% were identified on T2‐weighted SE images, whereas only 26% were identified on IR images. However, IR images may be more useful in local staging of carcinoma. Gross capsular infiltration was present in only two patients; however, it was detectable (and excluded in five other patients) by means of IR images. It was not detectable on SE images. The high quality of images obtained with the endorectal coil was confirmed. The authors conclude that addition of the IR sequence to MR imaging with the endorectal coil may improve the usefulness of this examination.
Quantitation of structural distortion of the cervical neural foramina in gradient‐echo MR imaging
Authors: Tien Robert D. , Buxton Richard B. , Schwaighofer Bernard W. , Chu Pauline K. 
Published: March 2007

AbstractQuantitative errors (due to magnetic susceptibility artifacts) in the measurement of the cervical spinal neural foramina with fast gradient‐echo (GRE) magnetic resonance imaging were assessed. Cylindric phantoms of different materials were used to demonstrate the nature of magnetic susceptibility artifacts, emphasizing the dependence of the artifact on tissue geometry. Neural foramina diameters measured on thin, sagittal GRE and spin‐echo (SE) images through the neural foramina of a fresh human cervical spine specimen were then compared with direct measurements with calipers. The GRE images showed more apparent narrowing than did the SE images. The absolute distortion of seven neural foramina was rather constant (less than two pixels) on the GRE images; therefore, the relative distortion was inversely proportional to the size of the neural foramen, ranging up to 10% in the upper cervical region at a short TE. The absolute and relative distortion increased as TE increased. At a constant TE, the structural distortion did not change with different TRs or flip angles. The shortest possible TE is recommended in evaluation of the cervical spine.
T2‐weighted three‐dimensional MP‐RAGE MR imaging
Authors: Mugler John P. , Spraggins Thomas A. , Brookeman James R. 
Published: March 2007

AbstractThe application of three‐dimensional (3D) magnetization‐prepared rapid‐gradientecho (MP‐RAGE) imaging to the acquisition of T2‐weighted 3D data sets has been investigated, with a 90x°–180y°−90−x° pulse set (driven equilibrium) for the T2 contrast preparation. A theoretical model was used to study the contrast behavior of brain tissue. The effects of radiofrequency and static‐field inhomogeneities and eddy currents on the T2 contrast preparation and the effects of eddy currents on the gradientecho acquisition resulted in blurring and intensity banding artifacts. With a multistep gradient preparation, these artifacts could be suppressed. With further development, this technique may yield a clinically practical method for obtaining T2‐weighted 3D data sets of relatively large volumes (eg, the whole head) suitable for multiplanar reformatting.
Normal and degenerating articular cartilage: In vitro correlation of MR imaging and histologic findings
Authors: Monson Nancy L. , Haughton Victor M. , Modi Jean M. , Sether Lowell A. , PhD Khang‐Cheng Ho 
Published: March 2007

AbstractHistologic correlation of the different magnetic resonance (MR) appearances of articular cartilage has not been studied extensively. Therefore, the authors correlated thin (high‐resolution) MR sections of articular cartilage with histologic sections. Human cadaver lumbar facet joints were imaged with a 1‐mm section thickness and a 4‐cm field of view, then sectioned and stained for histologic comparison. MR imaging patterns were identified that correlated with normal cartilage and three histologically different patterns of degeneration.
Hepatic focal nodular hyperplasia: MR imaging at 1.0 and 1.5 T
Authors: Haggar Allan M. , Bree Robert L. 
Published: March 2007

AbstractTen cases of hepatic focal nodular hyperplasia (FNH) were studied with magnetic resonance (MR) imaging. Proof of diagnosis was by needle biopsy or follow‐up of as long as 5 years. Both short TR/TE and long TR/TE images were obtained. The most common finding was isointen‐sity of the lesion relative to liver parenchyma with all pulse sequences. A central scar was seen in only one patient and was hyperintense on long TR/TE images. Slight hyperintensity of the lesion on short TR/TE and long TR/TE images was seen in two cases. Textural heterogeneity was present in only one of these. The most common presentation in our series was a visually isointense lesion relative to liver on short TR/TE images and an isointense or slightly hyperintense lesion on long TR/TE images. A review of the literature and the present findings suggest that FNH has a variable appearance on MR images.
Quantitative P‐31 MR spectroscopy of the liver in alcoholic cirrhosis
Authors: Rajanayagam Vasanthan , Lee Roland R. , Ackerman Zvi , Bradley William G. , Ross Brian D. 
Published: March 2007

AbstractTo determine the cause of reduced urea synthesis in cirrhosis, absolute concentrations of phosphorus metabolites in the human liver have been measured in vivo with magnetic resonance (MR) spectroscopy. One‐dimensional chemical shift imaging was used to obtain phosphorus‐31 spectra from five healthy volunteers and five patients with alcoholic cirrhosis. A reference standard included in all studies enabled the calculation of absolute concentrations. In contrast to hepatic metabolite ratios, absolute concentrations reveal that in the cirrhotic patients, concentrations of adenosine triphosphate (ATP) were significantly reduced and concentrations of phosphomonoesters slightly reduced. Intracellular pH was unchanged. Histologic evidence suggests that the amount of ATP per cell was unchanged and could not account for the reduced urea production. Instead, urea synthesis depends on the functional liver cell mass, which was reduced by 31% in alcoholic cirrhosis. Quantitative in vivo P‐31 MR spectroscopy of liver has potential clinical applications and can supplement the more generally used P‐31 metabolite ratios.
Improved receiver coil for upper thoracic spine imaging in a vertical magnetic field
Authors: Malmgren Lars , Ståhlberg Freddy , Holtås Stig , Larsson Elna‐Marie , Persson Bertil R. R. 
Published: March 2007

AbstractTo improve image quality in the upper thoracic spine, an anatomically shaped copper wire loop coil, made to fit over the patient's shoulders, was constructed. The coil was permanently mounted on a foam‐rubber vest to facilitate attachment to the patient. Phantom and in vivo studies of the performance of the coil in healthy volunteers showed as much as a two times greater signal‐to‐noise ratio relative to that of standard coils for the upper thoracic spine. In a patient with lesions in the upper thoracic cord, the coil gave better image quality in the region of interest than did the standard coils. The coil has been integrated into the authors' routine imaging equipment and has been the coil of choice for imaging of the upper thoracic spine on their 0.3‐T vertical field system.
Tissue specificity of low‐field‐strength magnetization transfer contrast imaging
Authors: Niemi Pekka T. , Komu Markku E. S. , Koskinen Seppo K. 
Published: March 2007

AbstractThe time‐dependent saturation transfer technique was used to measure the transfer of magnetization in several rat tissues at 0.1 T. The length of the saturation pulse was varied from 0 to 510 msec. The magnetization transfer contrast effect was characteristic for each type of tissue. A substantial reduction of image intensity was obtained in skeletal muscle (74%), heart (71%), spleen (64%), brain (65%), pancreas (64%), liver (64%), kidneys (62%), and lungs (56%) with the longest saturation pulse available. Much smaller declines occurred in stagnant blood and peritoneal fat. The potential of this imaging technique for clinical conditions is discussed.
Change in red blood cell relaxation with hydration: Application to MR imaging of hemorrhage
Authors: Taber Katherine H. , Ford Joseph J. , Jensen Ray S. , Chin Hsiao Yang , Udden Mark M. , Plishker Gordon A. , Contant Charles F. , Hayman L. Anne 
Published: March 2007

AbstractT1 and T2 were measured in unclotted blood samples with 0.24‐ and 4.7‐T spectrometers. The fraction by weight of intracellular water in the red blood cells (RBCs) was varied by either osmotic manipulation or density separation in concentrated (packed RBCs) and dilute (RBCs suspended in buffer or serum) samples. Reducing the cell water content caused a moderate decrease in T1 and a profound decrease in T2 at both 0.24 and 4.7 T. Conversely, increasing the cell water content caused an increase in both T1 and T2. The authors conclude that dehydrated RBCs in an area of hemorrhage would cause a substantial decrease in signal intensity on long TR/TE (T2‐weighted) images. Overhydration of RBCs would have the opposite effect.
MR imaging of the pelvis with an endorectal‐external multicoil array
Authors: Schnall Mitchell D. , Connick Tom , Hayes Cecil E. , Lenkinski Robert E. , Kressel Herbert Y. 
Published: March 2007

AbstractMagnetic resonance (MR) images of the pelvis obtained with an endorectal coil have improved resolution relative to that of body coil images; however, they have limited spatial coverage. The sensitivity profile can be improved by using the endorectal coil combined with an external anterior coil as part of a multicoil array. If each coil is connected to a separate receiver, the individual images can be combined to provide an optimal signal‐to‐noise ratio (S/N). The authors have investigated a 5‐inch (12.7‐cm) surface coil or a two‐coil array as the anterior coil. In both of these configurations, the S/N is improved relative to that of the endorectal coil alone at distances greater than 3 cm from the endorectal coil. The anterior two‐coil array provides more lateral coverage. The improved spatial coverage available with this technique expands potential clinical applications of endorectal MR imaging.
MR microscopy of chick embryo vasculature
Authors: Smith Bradley R. , Effmann Eric L. , Allan Johnson G. 
Published: March 2007

AbstractSix‐day‐old chick embryos were examined with magnetic resonance microscopy after vascular perfusion fixation and perfusion with gadolinium‐doped gelatin to highlight the developing vascular anatomy. Gadolinium gelatin, with its short T1, provided a source of signal contrast within the vessels. The entire embryo was embedded in gelatin to minimize susceptibility artifacts that are prevalent at the high field strength (7.0 T) used. A series of single‐section spin‐echo images were acquired with various TRs to determine the optimal imaging sequence for a three‐dimensional (3D) acquisition. The combination of gadolinium gelatin in the vascular spaces, gelatin embedding of the specimen, and optimal acquisition parameters yielded a 3D stack of high‐resolution images that was readily reconstructed and rendered to effectively demonstrate the developing thoracic vessels in the embryo.