bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic image reconstruction: MR movies from motion ghosts
Authors: Xiang Qing‐San , Henkelman R. Mark 
Published: March 2007

AbstractIt has been previously shown that an image with motion ghost artifacts can be decomposed into a ghost mask superimposed over a ghost‐free image. The present study demonstrates that the ghost components carry useful dynamic information and should not be discarded. Specifically, ghosts of different orders indicate the intensity and phase of the corresponding harmonics contained in the quasi‐periodically varying spin‐density distribution. A summation of the ghosts weighted by appropriate temporal phase factors can give a time‐dependent dynamic image that is a movie of the object motion. This dynamic image reconstruction technique does not necessarily require monitoring of the motion and thus is easy to implement and operate. It also has a shorter imaging time than point‐by‐point imaging of temporal variation, because the periodic motion is more efficiently sampled with a limited number of harmonics recorded in the motion ghosts. This technique was tested in both moving phantoms and volunteers. It is believed to be useful for dynamic imaging of time‐varying anatomic structures, such as in the cardiovascular system.
Improved cine MR imaging of left ventricular wall motion with gadopentetate dimeglumine
Authors: Pennell Dudley J. , Richard Underwood S. , Longmore Donald B. 
Published: March 2007

AbstractThe assessment of left ventricular wall motion with cine magnetic resonance imaging in the cardiac long axes is useful; however, image quality is limited by reduced signal intensity due to saturation of blood flowing predominantly in plane. Twenty subjects were studied to evaluate the effects of gado‐pentetate dimeglumine on contrast between blood and myocardium. Contrast improved significantly on contrast agent –‐ enhanced images in the long axes, at both end‐systole (vertical axis, +62%, P <.0001; horizontal axis, +67%, P <.0001) and end‐diastole (vertical axis, +50%,P <.0001; horizontal axis, +26%, P <.004). The increase in the short axis was less and significant only at end‐systole (+25%, P <.0001). Subjective scoring of the cines also showed a significant and clinically useful improvement in the long axes (P <.0001 for both) on contrast‐enhanced images. Improved contrast was most evident for 10 minutes after injection, but persisted for up to 20 minutes at end‐systole in the long axes. Gadopentetate dimeglumine is useful for cine imaging of left ventricular wall motion when saturation effects prevent adequate clinical assessment.
Contribution of oral magnetic particles in MR imaging of the abdomen with spin‐echo and gradient‐echo sequences
Authors: Boudghëne Frank P. , Bach‐Gansmo Torre , Grange Jean‐Didier , Lame Samuel , Nantois Christine , Wallays Claudy , Bigot Jean‐Michel 
Published: March 2007

AbstractAn open phase III clinical trial of the oral contrast agent OMP (oral magnetic particles) was performed in 35 patients undergoing abdominal magnetic resonance (MR) imaging at 1.5 T with axial spin‐echo and gradient‐echo sequences. The diagnostic efficacy of OMP was examined by comparing pre‐ and postcontrast images. Bowel loops and abdominal organs were more easily recognizable after OMP ingestion, and the general quality of the images was improved because of fewer bowel‐related artifacts. The diagnostic value of the postcontrast abdominal MR examination was superior or equal to that of the precontrast study, and additional information was obtained in 44% of the cases. Postcontrast gradient‐echo sequences increased confidence in the MR examination in 18% of cases. OMP was well tolerated and increased the quality and amount of diagnostic information acquired during the examination. Gradient‐echo imaging was found to be a useful complement, but the need for a reduction in susceptibility artifacts was apparent and indicates that a decrease in TE or the use of rapid spin‐echo sequences might be advantageous.
Status of liposomes as MR contrast agents
Authors: Unger Evan C. , Shen De‐Kang , Fritz Thomas A. 
Published: March 2007

AbstractRecent work on the development of liposomal magnetic resonance (MR) contrast agents has yielded structures with higher overall relaxivity than that of other nanoparti‐cles of similar diameter. Liposomes incorporating membrane‐bound complexes of manganese (“memsomes”) produce greater hepatic enhancement per micromole of metal ion than either ferrite particles or paramagnetic chelates. Memsomes also hold promise for targeting of sites outside the liver. Work is in progress to take these agents into clinical trials.
Cirrhosis: Multiobserver analysis of hepatic MR imaging findings in a heterogeneous population
Authors: Mitchell Donald G. , Lovett Karen E. , Hann Hie‐Won L. , Ehrlich Saundra , Palazzo Juan , Rubin Raphael 
Published: March 2007

AbstractTo investigate the magnetic resonance (MR) imaging findings of hepatic cirrhosis and the potential of MR imaging in differentiating cirrhosis from other hepatic abnormalities, three observers with different levels of expertise in MR imaging (specialist, experienced radiologist, and novice with special training) reviewed hepatic MR imaging examinations of 52 patients with biopsy‐proved presence (n = 29) or absence (n = 23) of cirrhosis. All examinations included motion‐compensated T1‐weighted, T2‐weighted, and flow‐sensitive gradientecho images. For all three observers, linear signal irregularity was more accurate than other findings. For the final diagnosis of cirrhosis, the specialist was most sensitive (76% at high threshold, 97% at low threshold), followed by the novice with special training (31% and 79%, respectively). Specificity was 100% for all observers at high threshold and 78%, 96%, and 87% for expert, experienced, and trained novice observers, respectively, at low threshold. Sensitivity did not vary regardless of severity of fibrosis, as determined independently by a hepatopathologist. MR imaging has the potential of offering a comprehensive noninvasive evaluation of patients with suspected cirrhosis, but considerable expertise is required at present.
Optimization of submillimeter‐resolution MR imaging methods for the inner ear
Authors: Schmalbrock Petra , Brogan Martha A. , Chakeres Donald W. , Hacker Vicky A. , Ying Kui , Clymer Bradley D. 
Published: March 2007

AbstractSubmillimeter‐resolution magnetic resonance (MR) imaging of the inner ear is valuable for diagnosis and treatment planning. Its main advantage for investigations of underlying disease is that it can directly depict the fluid spaces of the membranous labyrinth rather than define only the bony canal, as does computed tomography. A systematic evaluation of factors influencing high‐resolution three‐dimensional (3D) gradient‐echo imaging of the inner ear with a standard clinical MR system is presented. This includes the evaluation of various radio‐frequency coils, the design of steady‐state pulse sequences, and the optimization of acquisition parameters. A quantitative analysis was facilitated by computer simulations and image processing. The highest signal‐to‐noise ratio for the membranous labyrinth was obtained with a single 3‐inch (7.6‐cm) receiver coil and a 3D GRASS (gradient‐recalled acquisition in the steady state) sequence with the minimal achievable TR msec/TE msec of 25/7 and a 40°–60° flip angle, which yielded acceptable images with minimal voxel volumes of 0.1 mm3 in 14 minutes.
MR imaging of blood oxygenation‐dependent changes in focal renal ischemia and transplanted liver tumor in rat
Authors: Vexler Vladimir S. , De Crespigny Alexander J. S. , Wendland Michael F. , Kuwatsuru Ryonei , Mühler Andreas , Brasch Robert C. , Moseley Michael E. 
Published: March 2007

AbstractThe potential of using fast magnetic resonance (MR) imaging in conjunction with apnea‐induced blood deoxygenation for the noninvasive monitoring of relative perfusion in the rat abdomen has been studied with two experimental models: glycer‐ol‐induced focal renal ischemia and transplanted liver tumor. Gradient‐echo echo‐planar imaging (GRE‐EPI) (TE of 20 msec at 2 T) of liver and kidney was performed before, during, and after a 60‐second apnea episode and then was followed in the same rat by contrast‐enhanced (a) GRE‐EPI and (b) T1‐weighted spin‐echo imaging (TR msec/TE msec = 200/6) with polylysine‐(gadolmium‐DTPA [diethylenetriaminepentaacetic acid]). The results indicate that a noninvasive vascular challenge due to apnea can be used for the detection of focal tissue perfusion abnormalities in rat kidney and liver tumor.
MR imaging of Ho:YAG laser diskectomy with histologic correlation
Authors: Phillips Jeffrey J. , Kopchok George E. , Peng Shi‐Kaung , Mueller Mark P. , White Rodney A. 
Published: March 2007

AbstractTwelve cadaveric vertebral specimens were imaged after holmium yttrium aluminum garnet (Ho:YAG) laser diskectomy to determine the usefulness of magnetic resonance (MR) imaging in evaluating treatment outcome. The Ho:YAG laser was operated at 1.0‐2.0 J per pulse, 5 Hz, and 250‐usec pulse width. The total energy varied between 600 and 2,700 J. Two distinct patterns emerged on MR images. Tissue ablation at higher power (1.5 and 2.0 J per pulse) produced discrete signal voids that correlated with areas of laser‐induced ablation identified at gross inspection. More subtle changes, characterized by a high‐signal‐intensity ring, were seen in the specimens lased at 1.0 J per pulse. The latter appearance corresponded to incomplete vaporization of diskal tissue, a broader zone of minimal thermal injury, and sparing of adjacent vertebral endplates. Total mass loss did not appear to be affected by the choice of power setting (1.0 vs 1.5 J per pulse), with total laser energy held constant.
Semiautomated method for noise reduction and background phase error correction in MR phase velocity data
Authors: Walker Peter G. , Cranney Gregory B. , Scheidegger Markus B. , Waseleski Gena , Pohost Gerald M. , Yoganathan Ajit P. 
Published: March 2007

AbstractBackground phase distortion and random noise can adversely affect the quality of magnetic resonance (MR) phase velocity measurements. A semiauto‐mated method has been developed that substantially reduces both effects. To remove the background phase distortion, the following steps were taken: The time standard deviations of the phase velocity images over a cardiac cycle were calculated. Static regions were identified as those in which the standard deviation was low. A flat surface representing an approximation to the background distortion was fitted to the static regions and subtracted from the phase velocity images to give corrected phase images. Random noise was removed by setting to zero those regions in which the standard deviation was high. The technique is demonstrated with a sample set of data in which the in‐plane velocities have been measured in an imaging section showing the left ventricular outflow tract of a human left ventricle. The results are presented in vector and contour form, superimposed on the conventional MR angiographic images.
Characterization of focal fatty change in the liver with a fat‐enhanced inversion‐recovery sequence
Authors: Kane Arthur G. , Redwine Michael D. , Cossi Alda F. 
Published: March 2007

AbstractA T1‐weighted inversion‐recovery (IR) sequence was used to study 15 patients with possible fatty change in the liver. The inversion time (TI) was calculated for optimal suppression of normal liver signal (t‐null). Conventional spin‐echo (SE) and short TI IR (STIR) sequences were also performed. For seven documented benign focal fatty liver lesions, the T1‐weighted IR (fatenhanced)sequence clearly enabled differentiation of normal from fat‐infiltrated liver, whereas three of these lesions were isointense to normal liver with all other sequences. The livers of the other nine patients (two normal, one with diffuse fatty change, two with metastatic disease, one with hemangioma, one with focal nodular hyperplasia, one with simple cyst, and one with micronodular cirrhosis) showed homogeneous reduction of liver signal with the fat‐enhanced IR sequence.
MR imaging of muscle and tender points in fibromyalgia
Authors: Kravis Marc M. M. , Munk Peter L , McCain Glenn A. , Dale Vellet A. , Levin Morris F. 
Published: March 2007

AbstractFibromyalgia is a syndrome manifested by chronic, diffuse muscu‐loskeletal aching and soreness, palpable muscle tender points, and other symptoms. Standardized clinical diagnostic criteria have recently been developed. Skeletal muscle has been postulated as the end organ in this disease. Biochemical, histologic, electromyographic, and conventional radiographic studies have demonstrated no definitive abnormality. This study sought to establish whether magnetic resonance (MR) imaging could demonstrate any abnormality in these patients. Eighteen patients were entered in the study, 14 of whom were able to complete their examinations. T1 ‐weighted, T2‐weighted, gradient‐echo, and STIR (short‐tau inversion‐recovery) sequences were performed in all patients, with selected patients examined with T1weighted, gadopentetate dimeglu‐mine‐enhanced sequences. The trapezius and suboccipital regions were imaged in patients who, clinically, had active fibro‐myalgia. No abnormalities could be detected. The authors conclude that the conventional MR imaging used in this study was unable to depict any primary skeletal muscle abnormality in fibromyalgia.
Automated myocardial edge detection on MR images: Accuracy in consecutive subjects
Authors: Fleagle Steven R. , Thedens Daniel R. , Stanford William , Thompson Brad H. , Weston John M. , Patel Pranav P. , Skorton David J. 
Published: March 2007

AbstractThe authors previously demonstrated the feasibility of graph‐searching‐based automated edge detection in cardiac magnetic resonance (MR) imaging. To further assess the clinical utility of this method, unselected images from 11 consecutive subjects undergoing clinically indicated (except for one healthy volunteer) short‐axis spin‐echo MR imaging were analyzed. A total of 142 images from the 11 subjects, encompassing the left ventricle from apex to outflow tract, were analyzed. The computer algorithm correctly identified complete endocardial and epicardial contours in 121 of 142 images (85%). Correlations between observerbraced and computer‐derived epicardial areas for all images were good (r = .71 for epicardium, r = .83 for endocardium); they improved for a subset of higherquality images (r = .82 for epicardium, r = .92 for endocardium). The authors conclude that the current data further support the usefulness of computer digital image processing in geometric analysis of cardiac MR image data.
Differentiation between hemangiomas and cysts of the liver with nonenhanced MR imaging: Efficacy of T2 values at 1.5 T
Authors: Li Wei , Nissenbaum Michael A. , Stehling Michael K. , Goldmann Alexander , Edelman Robert R. 
Published: March 2007

AbstractThe authors studied the utility of non‐contrast‐agent‐enhanced magnetic resonance (MR) imaging for differentiating cysts and cavernous hemangiomas of the liver. Nineteen patients with hemangiomas (51 lesions) and 16 with cysts (30 lesions) were studied with a 1.5‐T MR imager. T2 values were calculated with the two‐point method to evaluate the efficacy of T2 values in the differentiation between hemangiomas and cysts of the liver. For lesions larger than 1 cm, the mean T2 value of cysts (306 msec ± 156) was significantly longer than that of hemangiomas (113 msec ± 15) (P < .0001); there was no overlap of the ranges for T2 values of hemangiomas and cysts. All cysts larger than 1 cm could be differentiated from hemangiomas by using a threshold T2 value of 140 msec. This study suggests that calculated T2 values permit differentiation between hemangiomas and cysts larger than 1 cm at 1.5 T.
Gadolinium phosphonates as MR imaging contrast agents: Physiologic effects in rabbit hearts
Authors: Adzamli I. Kofi , Weinstein Howard , Leppo Jeffrey A. 
Published: March 2007

AbstractThe hemodynamic effects of the diphosphonate terminus of a new infarct‐avid magnetic resonance (MR) imaging agent, gadolinium‐DTPA (diethylenetriamine‐pentaacetic acid) HPDP (1‐hydroxo‐3‐aminopropane‐1,1‐diphosphonate), and HEDP (hydroxyethyl‐1,1‐diphosphonate) (a simple diphosphonate terminus model) have been evaluated at MR imaging doses in both isolated and intact rabbit hearts. Rapid injections of the sodium salt of the diphosphonates reversibly depressed left ventricular developed pressure and its first derivative (dP/df) but did not affect the in vivo heart rate. Hemodynamic depression was prevented by the co‐administration of two equivalents of calcium ion per diphosphonate terminus in the isolated heart and by either slow infusion or co‐administration of one equivalent of calcium ion per diphosphonate terminus in the in vivo heart. Therefore, if these agents are to be used in MR imaging of acute myocardial infarction, appropriate measures should be taken to prevent negative inotropic effects.
Dynamic gadolinium‐enhanced three‐dimensional abdominal MR arteriography
Authors: Prince Martin R. , Yucel E. Kent , Kaufman John A. , Harrison David C. , Geller Stuart C. 
Published: March 2007

AbstractThe abdominal aorta and renal, visceral, and iliac arteries were evaluated in 16 patients with three‐dimensional Fourier transform imaging enhanced with gadopentetate dimeglumine. By imaging dynamically during the arterial phase of a 5‐minute injection (0.2 mmol/kg), highly significant (P < .0001) preferential arterial enhancement (signal‐to‐noise ratio ± standard deviation, 10 ± 0.9), with minimal enhancement of the inferior vena cava (5.1 ± 1.4) or background tissues (fat, 4.3 ± 0.7; muscle, 2.4 ± 0.5), was achieved in every patient. In six patients with angiographic and/or surgical correlation, 10 of 10 stenoses and two of two occlusions were correctly identified. No inplane saturation or pulsatility artifact was identified in any of the 16 patients. In conclusion, dynamic imaging during the injection of gadopentetate dimeglumine is a promising technique for evaluation of the abdominal aorta and branch vessels.
Statistical description of microcirculatory flow as measured with an MR method
Authors: Su Min‐Ying , Nalcioglu Orhan 
Published: March 2007

AbstractQuantification of microcirculatory flow is important for the functional assessment of biologic systems. The authors describe a method of analyzing the dependence of the magnetic resonance (MR) signal intensity on microcirculatory flow. A gel bead phantom was used to simulate the randomly oriented flow capillaries, and the MR signal intensity of the phantom was studied at different flow velocities by using velocity‐sensitized and ‐compensated spin‐echo pulse sequences. A theoretical model based on the spin‐phase phenomenon is proposed to elucidate the effect of flow on signal intensity. The velocity phase of a spin depends on its path and the corresponding velocity‐encoding gradients. A Monte Carlo simulation was used to generate the path of a spin on the basis of a statistical model for flow through a random capillary network. From the velocity‐phase distribution of a group of spins within a voxel, the signal attenuation due to flow can be calculated. The results of the statistical model and experimental measurements agreed well. Also, T1 and T2 effects in MR flow measurements were investigated. The current study provides a theoretical framework for understanding MR measurements of micro‐circulatory flow.
Magnetization transfer imaging with pulsed off‐resonance saturation: Variation in contrast with saturation duty cycle
Authors: McGowan, III Joseph C. , Schnall Mitchell D. , Leigh John S. 
Published: March 2007

AbstractMagnetization transfer contrast (MTC) can be generated in magnetic resonance images of water‐containing macromolecular structures. Results obtained with the pulsed off‐resonance saturation technique for achieving MTC are presented, allowing comparison of this technique with others. The magnetization transfer effect is demonstrated in newborn piglet brain and bovine muscle tissue, as well as in human subjects. MTC increases nonlinearly with the duty cycle of the off‐resonance irradiation, approaching a maximum value corresponding to continuous irradiation. However, approximately half of the available contrast can be obtained at a given saturation offset frequency, with 16% irradiation duty cycle. Examples of MTC in various human tissues demonstrate the specificity of this technique at power levels within U.S. Food and Drug Administration guidelines. Plots of MTC versus the irradiation offset frequency demonstrate the effects of magnetization transfer and are compared with the curve generated by a control phantom that does not show magnetization transfer. Magnetization transfer imaging with pulsed off‐resonance saturation is effective and easily implemented and may be useful in the investigation of saturation transfer phenomena in tissue.
Improved T1‐weighted two‐dimensional MP‐GRE imaging of the liver with variable flip angles for shaping the signal evolution
Authors: Epstein Frederick H. , Mugler John P. , Brookeman James R. 
Published: March 2007

AbstractThe recently introduced method of shaping the transient signal evolution in magnetization‐prepared gradient‐echo (MP‐GRE) imaging with variable flip angles has been applied to two‐dimensional (2D) MP‐GRE imaging of the abdomen. The technique was analyzed by using theoretical models and was implemented on a standard 1.5‐T whole‐body imager with a segmented acquisition. Theoretical models predicted that the variable‐flip‐angle 2D MP‐GRE sequence would increase liver‐spleen signal difference–to‐noise ratios by 290%, 110%, and 160% compared with a 2D MP‐GRE sequence with a flip angle of 10° and sequential phase encoding, a 2D MP‐GRE sequence with a flip angle of 30° and centric phase encoding, and the fast low‐angle shot sequence, respectively. Experimental measurements supported the theoretical predictions.
Recurrent biliary cystadenoma: MR imaging appearance
Authors: Stoupis Christophoros , Ros Pablo R. , Dolson David J. 
Published: March 2007

AbstractThe authors report the case of a 37‐year‐old woman with a biliary cystadenoma that mimicked a liver cyst. The magnetic resonance (MR) imaging features of this rare lesion were correlated with the pathologic findings, showing the potential of MR imaging for depicting and aiding in the diagnosis of biliary cystadenoma and its recurrence.
Simpler locally focused tomography in MR imaging
Authors: Hu Xiaoping 
Published: March 2007

AbstractThe author describes a simple technique for performing locally focused tomography with magnetic resonance imaging. In contrast to a previous technique, which utilized wave functions to represent k‐space data, the one described here does not require complicated experimental design and reconstruction procedures and is easy to implement and understand. The technique is verified with an experimental study. Technical details and experimental results are presented.
Angle‐dependent utilization of gradient hardware for oblique MR imaging
Authors: Bernstein Matt A. , Licato Paul E. 
Published: March 2007

AbstractA straightforward method for calculating maximum gradient amplitudes for the frequency‐encoding, phase‐encoding, and section‐select functions in oblique magnetic resonance (MR) imaging is presented. The calculated amplitude values depend on the prescribed angulation and on which of the three functions are simultaneously active. The derived expressions are optimal in most cases, and when not optimal, they still offer substantial improvement over calculations that do not incorporate angular information. Both matrix‐based and geometric interpretations are presented.