ISSN:1053-1807    

DOI:10.1002/jmri.1880020202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:1053-1807    

DOI:10.1002/jmri.1880020203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:1053-1807    

DOI:10.1002/jmri.1880020204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe accuracy and reproducibility of cardiac ejection fraction (EF) measurements based on cine magnetic resonance (MR) imaging, radionuclide multigated acquisition (MUGA) blood pool imaging, and angiographic ventriculography were evaluated by comparing them with a volumetrically determined standard. A biventricular, compliant, fluid‐filled heart phantom was developed to mimic normal cardiac anatomy and physiology. Ventricular EFs were measured with cine MR imaging by summation of nine contiguous 10‐mm‐thick sections in short and long axis, with single‐plane ventriculography, and with MUGA. Three measurements were performed with each modality for each of three EFs. Ventriculography was least accurate, with average relative errors ranging from 7.9% for the largest EF to 60.1% for the smallest. Cine MR was most accurate, with average relative errors ranging from 4.4% to 8.5%. MUGA EF measurements showed good correlation, with average relative errors ranging from 7.1% to 22.4%. Comparison of the error variances for the three modalities with the F test revealed that MR and MUGA EF measurements were significantly more accurate than those based on ventriculography (P<.01). No significant difference was demonstrated between the accuracy of short‐ and long‐axis cine MR a

ISSN:1053-1807    

DOI:10.1002/jmri.1880020205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThree‐dimensional (3D) velocity maps acquired with 3D phase‐contrast magnetic resonance (MR) imaging contain information regarding complex motions that occur during imaging. A technique calledsimulated streamlines, Which facilitates the display and comprehension of these velocity data, is presented. Single or multiple seed points may be identified within blood vessels of interest and tracked through the velocity field. The resulting trajectories are combined with a 3D MR angiogram and displayed with 3D volume visualization software. Mathematical analysis highlights potential applications and pitfalls of the technique, which was implemented both in phantoms and in vivo with excellent results. For example, single streamlines reveal helical flow patterns in aneurysms, and multiple streamlines seeded in the common carotid artery reveal branch filling‐time relationships and slow filling of the carotid bulb. The technique is helpful in understanding these complex flow pat

ISSN:1053-1807    

DOI:10.1002/jmri.1880020206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:1053-1807    

DOI:10.1002/jmri.1880020207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA technique for rapid assessment of tissue motion was developed by combining spatially selective radio‐frequency tagging pulses with centric phase‐encoding view ordering in a T1‐weighted, magnetization‐prepared gradient‐echo acquisition sequence. This sequence allowed labeling and tracking of tissue motion with single‐image acquisition times of less than 3 seconds. Multiple tagged bands 3 mm thick were superimposed orthogonal to the imaging plane. Motion in the interval between tagging and the start of image acquisition could then be precisely determined. The technique was evaluated with phantom studies and then applied to human volunteers for assessment of skeletal muscle motion, phonation, and pelvic f

ISSN:1053-1807    

DOI:10.1002/jmri.1880020208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe noninvasive measurement of time‐resolved three‐dimensional (3D) strains throughout the myocardium could greatly improve the clinical evaluation of cardiac disease and the ability to mathematically model the heart. On the basis of orthogonal arrays of tagged magnetic resonance (MR) images taken at several times during systole, such strains can be determined, but only after heart motion through the image planes is taken into account. An iterative material pointtracking algorithm is presented to solve this problem. It is tested by means of mathematical models of the heart with cylindric and spherical geometries that undergo deformations and bulk motions. Errors introduced by point‐tracking interpolation were found to be negligible compared with those due to marker identification on the images. In a human heart studied with this technique, the corrected radial strains at the left ventricular base were approximately 2.5 times the two‐dimensional estimates derived from the fixed image planes. The authors conclude that material point tracking allows accurate, timeresolved 3D strains to be calculated from tagged MR images, and that prior correction for motion of the heart through image planes is ne

ISSN:1053-1807    

DOI:10.1002/jmri.1880020209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe dynamic effects of three different superparamagnetic magnetic resonance (MR) contrast agents on liver signal were evaluated with an echo‐planar imaging technique. The contrast agents were (a) USPIO (ultrasmall superparamagnetic iron oxide), which has a long blood half‐life and was developed for MR imaging of lymph nodes and bone marrow; (b) AG (arabinogalactan)‐USPIO, an asialoglycoprotein receptor directed iron oxide with hepatocyte uptake; and (c) AMI‐25, a conventional reticuloendothelial iron oxide agent. Dynamic liver signal intensity (SI) curves reflect different uptake mechanisms for the different agents. Receptor blocking experiments indicate that intracellular redistribution or clustering of the AG‐USPIO (known to occur from electron microscopy studies) does not contribute to the decrease in liver SI. Monitoring liver SI over time with echo‐planar imaging may provide a better understanding of the kinetics of the growing number of MR contrast agents and allow optimization of imaging protocols to exploit peak

ISSN:1053-1807    

DOI:10.1002/jmri.1880020210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

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

ISSN:1053-1807    

DOI:10.1002/jmri.1880020211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY