bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrimination between different types of white matter edema with diffusion‐weighted MR imaging
Authors: Ebisu Toshihiko , Naruse Shoji , Horikawa Yoshiharu , Ueda Satoshi , Tanaka Chuzo , Uto Mitsuhiro , Umeda Masahiro , Higuchi Toshihiro 
Published: March 2007

AbstractBrain edema can be classified into three categories: vasogenic, cytotoxic, and interstitial. The mechanism of edema is thought to be different in each type. The authors studied the movement of water molecules in each type of white matter edema in a rat model by using diffusion‐weighted magnetic resonance imaging. Conventional T2‐weighted imaging did not allow distinction between the three types of white matter edema; the three types of edema were, however, distinguished by using diffusion‐weighted imaging. The apparent diffusion coefficient (ADC) of water was different in each type of edema. Water molecules in cytotoxic edema induced by triethyl‐tin intoxication showed a smaller and less anisotropic ADC than in normal white matter. In contrast, water in vasogenic edema induced by cold injury had a larger and more anisotropic ADC than in normal white matter. Water in interstitial edema due to kaolin‐induced hydrocephalus had an anisotropic and very large ADC.
Frequency response of retrospectively gated phase‐contrast MR imaging: Effect of interpolation
Authors: Frayne Richard , Rutt Brian K. 
Published: March 2007

AbstractRetrospectively gated phase‐contrast (PC) magnetic resonance velocity and volume flow measurements were evaluated in both in vitro and in vivo experiments. The accuracy of these measurements was found to be affected by the interpolation window width required in the reconstruction of retrospectively gated data. Interpolation modified the frequency content of the series of temporal measurements by decreasing the response at higher frequencies. With a series of sinusoidal flow waveforms, the frequency response of one specific implementation of retrospectively gated PC velocity measurements was experimentally determined. The experimental response agreed with the theoretical response predicted from an analysis of the interpolating function (2.2% root‐mean‐square difference). In vitro experiments with a simulated carotid flow waveform demonstrated errors in the systolic measurements that were a direct result of the modified frequency response. A volunteer study was also undertaken and confirmed the in vitro findings.
Diagnosis of bronchial rupture with MR imaging
Authors: Huson Henry , Sais Gerard J. , Amendola Marco A. 
Published: March 2007

AbstractTracheobronchial rupture is a serious injury occurring in approximately 1.5% of cases of major chest trauma. This injury is associated with significant mortality and morbidity and may be difficult to recognize both clinically and radiologically. Radiologic signs are mostly nonspecific, with pneumothorax and pneumomedi‐astinum being the most common. A high level of suspicion is required to make the diagnosis. Computed tomography (CT) can be helpful; however, it provides only indirect evidence for the diagnosis. This report describes a case of complete transection of the right main bronchus, suspected at plain radiography and CT and clearly shown on magnetic resonance (MR) images. MR imaging, with its multiplanar capabilities, can be helpful in defining the location and extent of injury and in diagnosing injury not suspected or clearly demonstrated with other imaging modalities.
Measurement of stroke volume and cardiac output within a single breath hold with echo‐planar MR imaging
Authors: Hunter George J. , Hamberg Leena M. , Weisskoff Robert M. , Halpern Elkan F. , Brady Thomas J. 
Published: March 2007

AbstractThe measurement of cardiac output and ejection fraction is useful in the treatment of diverse cardiac and cardiopulmonary disease states. Although several techniques are available for accurate measurement of left ventricular parameters, assessment of the right ventricle is less well represented. No single method is overwhelmingly superior, each having different strengths and weaknesses. In the present study, the applicability of an echo‐planar magnetic resonance (MR) imaging method in which a complete volumetric measurement of the right and left ventricles may be obtained during 12 heartbeats is demonstrated. This rapidity permits imaging during a 15‐second breath hold. The authors show in 12 volunteers that breath‐hold echo‐planar volume measurements of both ventricles were consistent with results obtained with conventional MR imaging methods.
Asymmetric‐Echo, Short TE, Retrospectively gated MR imaging of the heart and pulmonary vessels
Authors: Richardson Donna B. , MacFall James R. , Sostman H. Dirk , Spritzer Charles E. 
Published: March 2007

AbstractAlthough retrospectively cardiac‐gated (cine) magnetic resonance imaging has shown promise for large‐vessel pulmonary vascular imaging, it has not been able to depict the peripheral pulmonary vasculature, where signal is dephased because of susceptibility and/or motion artifacts. The authors developed a cine pulse sequence that uses asymmetric echoes and radio‐frequency envelopes to achieve reduced gradient moments and a short TE, thereby reducing signal losses due to disordered flow and susceptibility effects. The effects of TE (2.8–12 msec) and the degree of echo symmetry as measured by the echo symmetry fraction (ESF) (0.6–1.0) are considered in the pulmonary vasculature and the heart. In pulmonary vessels, the signal‐to‐noise ratio nearly doubled as TE was decreased from 12 to 2.8 msec, but there was only about a 15% difference as the ESF decreased from 1.0 to 0.6, consistent with T2* losses dominating gradient moment dephasing. At a TE of 2.8 msec, the sequence improves visualization of pulmonary vessels and may be helpful for diagnosing pulmonary emboll. In the heart, however, the contrast‐to‐noise ratio between blood and cardiac tissue decreased by 30% as TE decreased from 12 to 2.8 msec and was not affected by changes in ESF. Flow artifacts in the cardiac blood pool, including those that can aid in diagnosis (eg, signal loss due to “jet” flow), are much less pronounced when a small ESF and short TE are used, making this sequence less attractive for investigation of cardiac flow irregularities. The reduced flow artifacts in this case, however, permit excellent depiction of gross cardiac anatomy.
Comparison of T2‐weighted spin‐echo and fast spin‐echo techniques in the evaluation of myelination
Authors: Prenger Erin C. , Beckett William W. , Kollias Spyros S. , Ball William S. 
Published: March 2007

AbstractTo evaluate T2‐weighted fast spin‐echo (FSE) and conventional spin‐echo (CSE) magnetic resonance (MR) techniques in the assessment of brain myelination, 100 consecutive pediatric patients were imaged prospectively with both CSE and FSE sequences. All patients underwent a routine MR examination that included T2‐weighted CSE imaging (imaging time, 10 minutes 21 seconds) and T2‐weighted FSE imaging (imaging time, 2 minutes 5 seconds). The two techniques were compared for estimating the degree of myelination (using normal anatomic landmarks) by blind review. With T2‐weighted CSE images as the “gold standard” for estimation of normal myelination, FSE images were evaluated to determine if they showed the degree of myelination similarly to CSE images. There was a strong correlation (P <.01) between CSE and FSE images in the estimation of myelination over a wide range of patient ages.
Solitary hepatic metastasis: Comparison of dynamic contrast‐enhanced CT and MR imaging with fat‐suppressed T2‐weighted, Breath‐hold T1‐weighted FLASH, and dynamic gadolinium‐enhanced FLASH sequences
Authors: Semelka Richard C. , Shoenut J. Patrick , Ascher Susan M. , Kroeker Mervyn A. , Greenberg Howard M. , Yaffe Clifford S. , Micflikier Allan B. 
Published: March 2007

AbstractTwenty consecutive cancer patients with a solitary hepatic metastasis detected with dynamic contrast‐material—enhanced computed tomography (CT) who were considered for hepatic resection underwent magnetic resonance (MR) imaging within 18 days after CT. Histologic confirmation was obtained in all lesions. CT depicted 20 solitary lesions. MR imaging showed a solitary lesion in 14 patients, two lesions in three patients, and more than two lesions in three patients, for a total of 37 lesions. Twenty‐three lesions less than 2 cm in diameter were missed with CT, and six lesions less than 1.3 cm in diameter were missed with MR imaging. MR imaging was superior to CT in the detection of hepatic metastases on a patient‐by‐patient basis (P <.01). The results suggest that MR imaging is superior to dynamic contrast‐enhanced CT for the detection of hepatic metastases.
Enhancement effects of a hepatocyte receptor—specific MR contrast agent in an animal model
Authors: Small William C. , Nelson Rendon C. , Sherbourne Gillian M. , Bernardino Michael E. 
Published: March 2007

AbstractThe enhancement characteristics of the liver and spleen produced by a hepatocyte‐specific magnetic resonance imaging agent, an arabinogalactan‐coated ultrasmall superparamagnetic iron oxide derivative, BMS 180550, were evaluated. Both heavily T1‐ and T2‐weighted sequences were used. Imaging was performed in the farm pig model, as a function of contrast agent concentration (5, 10, and 20 μmol of iron per kilogram) and delay (immediate, 0.5, 2.5, 5.0, 7.5, and 9.0 hours) after bolus injection of BMS 180550. BMS 180550 provided excellent contrast enhancement characteristics by producing marked positive enhancement with T1‐weighted sequences and marked negative enhancement with T2‐weighted sequences. The T1‐weighted enhancement immediately after contrast agent injection was of greater magnitude in the spleen (329% ± 83) than in the liver (66% ± 16). Postcontrast negative enhancement with T2‐weighted sequences was largely hepatocyte specific at 5 and 10 μmol/kg but was also seen within the spleen at 20 μmol/kg. The authors discuss the possible mechanisms that produce these changes and conclude that 10 μmol/kg BMS 180550 is near the optimum dose for maximizing the enhancement properties of this agent with all sequences in the farm pig.
Discrete signal processing of dynamic contrast‐enhanced MR imaging: Statistical validation and preliminary clinical application
Authors: Reddick Wilburn E. , Langston James W. , Meyer William H. , Gronemeyer Suzanne A. , Steen R. Grant , Chen Gang , Taylor June S. 
Published: March 2007

AbstractA high‐resolution image‐based method was developed to analyze dynamic contrast agent‐enhanced magnetic resonance images quantitatively. This method determines the initial rate of contrast agent accumulation, the delayed rate of accumulation, and the maximum enhancement in each pixel. These three parameters allow characterization of the dynamic signal features. Simulated noisy test sets of dynamic enhancement curves have shown this method to yield a fast and accurate characterization of the dynamic signal. Clinical examples of both qualitative image parameter maps and quantitative statistical analysis of the parameter distributions demonstrated the quality and potential of the technique. The technique is designed to yield imaging and quantitative information on contrast agent accumulation that can be useful in detecting residual tumor and evaluating response to therapy, while requiring less than 7 minutes of imaging time and 5 minutes of processing time per study.
Dynamics of tumor imaging with Gd‐DTPA—polyethylene glycol polymers: Dependence on molecular weight
Authors: Desser Terry S. , Rubin Daniel L. , Muller Holde H. , Qing Fan , Khodor Samer , Zanazzi George , Young Stuart W. , Ladd David L. , Wellons Jennifer A. , Kellar Kenneth E. , Toner John L. , Snow Robert A. 
Published: March 2007

AbstractMacromolecular contrast media offer potential advantages over freely diffusible agents in magnetic resonance (MR) imaging outside the central nervous system. To identify an optimum molecular weight for macromolecular contrast media, the authors studied a novel macromolecular contrast agent, gadolinium diethylenetriaminepentaacetic acid polyethylene glycol (DTPA‐PEG), synthesized in seven polymer (average) molecular weights ranging from 10 to 83 kd. Twenty‐eight rabbits bearing V2 carcinoma in thighs underwent T1‐weighted spin‐echo imaging before injection and 5–60 minutes and 24 hours after injection of the Gd‐DTPA‐PEG polymers or Gd‐DTPA at a gadolinium dose of 0.1 mmol/kg. Tumor region‐of‐interest measurements were obtained at each time point to determine contrast enhancement dynamics. Blood‐pool enhancement dynamics were observed for the Gd‐DTPA‐PEG polymers larger than 20 kd. Polymers smaller than 20 kd displayed dynamics similar to those of the freely diffusible agent Gd‐DTPA. Above the 20 kd threshold, tumor enhancement was more rapid for smaller polymers. The authors conclude that the 21.9‐kd Gd‐DTPA‐PEG polymer is best suited for clinical MR imaging.
Effect of a patellar realignment brace on patellofemoral relationships: Evaluation with kinematic MR imaging
Authors: Shellock Frank G. , Mink Jerrold H. , Deutsch Andrew L. , Fox James , Molnar Todd , Kvitne Ronald , Ferkel Richard 
Published: March 2007

AbstractThe effect of a newly developed patellar realignment brace was evaluated in 21 patellofemoral joints (19 patients) with patellar subluxation (13 joints with lateral subluxation and eight with medial subluxation) by using active‐movement, loaded kinematic magnetic resonance (MR) imaging. Sixteen patellofemoral joints (76%) demonstrated a qualitative correction of or improvement in patellar subluxation (ie, centralization of the patella or a decrease in the displacement of the patella) after application of the brace. Four of the five “failures” occurred in patellofemoral joints that had patella alta and/or dysplastic bone anatomy. These results indicate that the patellar realignment brace was able to counteract patellar subluxation in the majority of patellofemoral joints studied, as shown by active‐movement, loaded kinematic MR imaging. This brace appears to be useful for conservative treatment of patients with patellofemoral joint pain secondary to patellar malalignment and maltracking.
Oxygen tension mapping with F‐19 echo‐planar MR imaging of sequestered perfluorocarbon
Authors: Barker Bruce R. , Mason Ralph P. , Bansal Navin , Peshock Ronald M. 
Published: March 2007

AbstractThe authors used fluorine‐19 inversion‐recovery (IR) echo‐planar imaging (EPI) to map oxygen tension on the basis of the spin‐lattice relaxation rate (R1) of sequestered perfluorocarbon. R1 measured with IR‐EPI varied as a linear function of oxygen tension and temperature, and the relationship agreed well with earlier spectroscopic findings. Oxygen tension maps of a mouse that had received a dose of perflubron emulsion were acquired before, during, and after the mouse breathed pure oxygen. Results showed low liver oxygen tension during air breathing, which increased during breathing of pure oxygen, with distinct regional heterogeneity, to 8–17%atm (60–130 torr [8.0–17.3 kPa]).
Precise and accurate measurement of proton T1 in human brain in vivo: Validation and preliminary clinical application
Authors: Steen R. Grant , Gronemeyer Suzanne A. , Kingsley Peter B. , Reddick Wilbum E. , Langston James S. , Taylor June S. 
Published: March 2007

AbstractPrecise and accurate inversion‐recovery (PAIR) magnetic resonance (MR) measurements of T1 were obtained in eight brain regions and cerebrospinal fluid of 26 healthy volunteers. Accuracy of the technique was assessed by measuring T1 in small fluid volumes with the PAIR technique and with two independent spectroscopic techniques. The mean difference between T1 measured with PAIR and with the two spectroscopic techniques was 3.1% ± 1.3. The precision (reproducibility) of measurements with the PAIR technique was excellent. The coefficient of variation (CV) across 16 measurements in a head phantom was 2.0%, compared with a CV of 2.7% across 45 separate measurements in a single subject. The within‐subject CV was 1.8% ± 0.6 in white matter and 1.4% ± 1.0 in basal ganglia. The between‐subject CV in 26 healthy volunteers was 3.6% ± 0.6 in white matter and 4.1% ± 1.9 in basal ganglia. Comparison between a patient with an active recurrent brain tumor and an agematched patient with an inactive brain tumor showed that T1 was significantly elevated throughout the brain of the active‐tumor patient, especially in white matter tracts, even though no tumor or edema was detected in the white matter on standard MR images. Comparisons between five brain tumor patients and four healthy volunteers of similar age showed that T1 was significantly and substantially elevated throughout the white matter tracts and in the caudate nucleus, putamen, and thalamus. These results are consistent with the hypothesis that white matter tracts are selectively vulnerable to edema and that T1 increases in white matter are a sensitive indicator of patient status or tumor aggressiveness.
Pulsation artifact in short TR MR imaging and angiography: Exacerbation with signal averaging
Authors: Mitchell Donald G. , Tasciyan Talin , Ortega Hector V. , Outwater Eric , Vinitski Simon 
Published: March 2007

AbstractAveraging the signals from more than one excitation per phase‐encoding view increases the signal‐to‐noise ratio and, in conventional spin‐echo magnetic resonance imaging, reduces most motion artifacts. To determine the effects of signal averaging on two‐dimensional gradient‐echo images, acquisitions with different TRs and with no averaging versus multiple‐signal averaging were compared in a pulsatile flow phantom and the human abdominal aorta. Intraview (each view repeated before changing the phase‐encoding value) and interview (obtaining all views sequentially and then repeating the entire set) averaging methods were used. Pulsation artifacts were present on all images of the flow phantom and the aorta. Intraview signal averaging, the method most commonly used, exacerbated rather than ameliorated pulsation artifacts with short TR sequences. Pulsation artifacts on two‐dimensional images obtained with a short TR can be minimized by completing the acquisition as rapidly as possible, avoiding signal averaging. If signal averaging is used for short TR images, it should be interview averaging.
Ex vivo evaluation of ferromagnetism, heating, and artifacts produced by heart valve prostheses exposed to a 1.5‐T MR system
Authors: Shellock Frank G. , Morisoli Stacy M. 
Published: March 2007

AbstractEx vivo testing techniques were used to determine the ferromagnetic qualities of, presence of heating in, and artifacts produced by 13 different heart valve prostheses exposed to a 1.5‐T (64‐MHz) magnetic resonance (MR) system. None of the heart valve prostheses showed a measurable deflection in the 1.5‐T static magnetic field. Only minimal artifacts were produced during MR imaging with a fast spoiled GRASS (gradient‐recalled acquisition in the steady state) pulse sequence. The largest temperature changes measured during a “worst case” MR imaging sequence (estimated average specific absorption rate, 2.5 W/kg; estimated spatial peak specific absorption rate, 7.6 W/kg) were +0.2°C with the implant imaged “in air” and +0.3°C with the implant imaged in normal saline. Therefore, MR procedures performed with a 1.5‐T (64‐MHz) MR system may be performed safely in patients with any of the 13 different heart valve prostheses evaluated in this study.
Comparison of breath‐hold T1‐weighted MR sequences for imaging of the liver
Authors: Semelka Richard C. , Willms Ann Bagley , Brown Mark A. , Brown Elizabeth D. , Finn J. Paul 
Published: March 2007

AbstractThree rapid T1‐weighted gradient‐echo techniques for imaging of the liver were compared: fast low‐angle shot (FLASH) and section‐selective (SSTF) and non‐section‐selective (NSTF) inversion‐recovery TurboFLASH. Ten healthy volunteers were imaged at 1.5 T, with breath‐hold images acquired in the transaxial and coronal planes and non‐breath‐hold images in the transaxial plane. Breath‐hold images were evaluated quantitatively and qualitatively, and non–breath‐hold images were evaluated qualitatively. FLASH images had significantly higher (P <.001) spleenliver signal difference–to‐noise ratios (SD/Ns) than NSTF and SSTF images. Liver signal‐to‐noise ratios (S/Ns) were significantly higher (P <.001) on FLASH images than on NSTF and SSTF images. With breath hold. FLASH images were rated as having the highest quality in the axial plane, followed by NSTF and SSTF images. In the coronal plane, NSTF images were rated as having the highest quality. For images acquired during patient respiration, NSTF images had the highest quality and showed the least degradation. The results suggest that FLASH images have the highest SD/N and S/N for liver imaging and have the highest quality in the axial plane. In patients who cannot suspend respiration, NSTF images may be least affected by breathing artifact and provide reasonable image quality.
Determination of Background Gradients with Diffusion MR Imaging
Authors: Jara Hernán , Wehrli Felix W. 
Published: March 2007

AbstractA new magnetic resonance (MR) imaging technique, opposite‐polarity pulsed‐field‐gradient technique, with which the effects of background magnetic field gradients can be separated from the effects of diffusion, is described. It is based on the processing of two sets of diffusion‐weighted images, the acquisition parameters of which differ only in the polarity of the applied diffusion pulses. The two effects can be separated because the cross term (bc) of the gradient factor function is antisymmetric with respect to reversal of the sign of the applied diffusion pulses. The technique permits simultaneous measurement of the spatial distribution of both the diffusion constants and background magnetic field gradients, with the same spatial resolution as the parent images from which they were derived. The technique has been validated with a phantom in which the spatial distribution of susceptibility‐induced background gradients is known, the results showing excellent agreement with theory. The technique was applied to two systems in which the spatial distribution of the background gradient is unknown. Sources of error in the measurement of background gradients and (unrestricted) diffusion constants are analyzed, including the effects of voxel size, partial volumes, and interactions between background and imaging gradients.
Effects of MR exposure on cell proliferation and migration of chick motoneurons
Authors: Yip Yee Ping , Capriotti Christine , Norbash Sepideh Gilani , Talagala S. Lalith , Yip Joseph W. 
Published: March 2007

AbstractThe effect of magnetic resonance (MR) exposure on the proliferation and migration of motoneurons was examined in chick embryos. Embryos were exposed in ovo to a static magnetic field of 1.5 T for 6 hours and to 64‐MHz radio‐frequency field pulses and a switched magnetic field gradient with an amplitude of 0.6 G/cm for 4 hours. For cell proliferation studies, embryos were exposed to MR fields during the developmental stage at which motoneuron proliferation is most active. For cell migration studies, embryos were exposed to MR fields at the developmental stage just before lateral motoneuron migration. The results show that the birth dates, migration, and proliferation of lateral motoneurons were unaffected by the MR exposure conditions in this study.