摘要:

AbstractMR images show a large range of contrast for various tissues in the body and are ideal for multispectral segmentation. Typically, only two MR images (dualecho series) are used for segmentation: however, other images are often available. We evaluated MR images from 40 patients to determine the optimal type and number of images required for segmentation of tissues associated with brain tumors (normal brain, edema, necrosis. and active tumor). Pattern recognition methods indicated that three MR images from the same slice location were adequate for segmentation. M defined by feature selection and feature extraction measures based on training fields. This result was also confirmed by visually examining segmented images for all 40 patients. The work demonstrates that by using existing imagelrtatistid analysis techniques (feature selection and feature extraction). one can systematically determine the optimal type and number of MR images for tissue segmentation.

ISSN:1053-1807    

DOI:10.1002/jmri.1880050502

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

年代:1995

数据来源: WILEY

摘要:

AbstractMagnetic reaonance velocity vector mapping was used to study flow patterns in dilated and healthy left ventricles. Eleven patients (age mean ± SD, 67 ± 12 yeare) with dilated left ventricle resulting from coronary artery diclease and 10 healthy volunteers (age 50 ± 9) were studied. Cine gradient echo images were acquired in the left ventricle vertical and horizontal long axes. Vertical and horizontal velocity components in the horizontal long axis plane of the left ventricle were encoded simultaneously. Maps of velocity components were then processed into multiple computer generated streaks whose orientation and length corresponded to velocity vectors. The following parameters (mean ± SD) differed significantly between the two groups: The heart rate (patients 70 211 beat/min. controls 57 ± 8, P<.001). end‐diastolic volume (patients 264 ± 83 ml. controls 143 ± 26 ml. P<.001). ejection fraction (patients 31% ± 7, controls 61% ± 6, P<.MI), diameter of the Mow stream (patients 1.7 ± 0.6 cm. controls 3.2 2 0.3 cm. P<.001). In normal subjects the predominant direction of diastouc now through the mitd valve was toward the apex with short‐lived vortices curling back behind each mitral ldet. The vortex beneath the anterior leaflet tended to be larger and more dominant. In patients with dilated left ventricle, the inflow was directed toward the free wall, giving rise to a well developed circular flow pattern turning back toward the septum and outflow tract and persisting through diastole. Magnetic resonance velocity vector mapping is an excellent method for studying left ventricular flow patterns. We have studied flow patterns in healthy volunteers and demonstrated abnormalities in patients with dilated left ventriclea resulting from coronary a

ISSN:1053-1807    

DOI:10.1002/jmri.1880050503

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe purpose of thls study was to evaluate efficacy and safety of a gadolinium (Gd) zeolite suspension aa an oral MRI contrast agent. Serial dilution of GADO‐ LITE@ orpl Suspdon 1.2500 pg of GdO/mL) were prepared. MRI (T1 and T2 welghted) of standards and dogs (precontrast and postcontraat) were performed. Toxicity and Gd absorption were also asmaued. Subsequently, 30 nod male adult volunteers were divided into six group of five subjects each. Gd zeolite po suspension waa adminlstered before and after MRI in volumes and concentrations ranging from 250 to 1600 mL; 6 to 80 pg ofGd+3/mL.The images were rated (efficacy score) by a bllnded reader. Vital signs, blood chemistries and urlnalysia were recorded. Gadollte Oral Suspension produced excellent enhancement of the dog gastrointestinal (GI) tract. No todclty or absorption of Gd wan obsenred in dogs receiving doses up to 4 times the anticipated human dose My for 14 consecutive days. In clinical tri.lr. Gd zeollte slgnlficantly lmproved the efficacy scores for all groups and all pulrina sequences (allPvalues<.05). Efflcacy scores and slgnal intendtics generally increased with concentration and volume. No Gd waa detected in blood or urine specimens. No signiftcant adverse events were reported. Gd zeolite 1s a promlsing contrast medium for enhancement of the GI tract in MR

ISSN:1053-1807    

DOI:10.1002/jmri.1880050504

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to assess the potential role of MR h@ng with polylysine‐Gd‐DTPA enhancement in the early detection of acute occlusive inteetinal ischemia in a rat model. After deveecularhtion Of the distal ileum in 12 rats. T2‐Weighted fart spinecho MR images were acquired, followed by T1‐ weighted imagea before and after IV administration of 0.1 mmol/kg polylysine‐Gd‐DTPA. The signal intensity of the ischemic intestine did not differ signiflcantly from that of the normal intestine before the admlnistration of the contrast material. No mucoeal or submucosal edema or hemorrhage was found in the ischemic intestine at histologic examination. After the administration of polylysine‐Gd‐DTPA, the ischemic intestine lacked enhancement and its signal intensity was significantly lower than that of the normal inteatine. MR imaging with polylysine‐Gd‐DTPA enhancement can detect acute occlusive ischemia of the rat intestin

ISSN:1053-1807    

DOI:10.1002/jmri.1880050505

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe purpose of this study was (1) to monitor the dynamic effects Of T1 ‐enhancing and magnetic SUSCCPtibility contrast material on normal canine myocardium using inversion recovery (IR)‐ and driven equilibrium @E)‐prepared fast gradient‐recalled echo (GRE) sequences and (2) to determine the relative value of T1‐enhancing and magnetic eusceptibflity contrast material in detecting regions of ischemia in the same animal. Normal dogs (n = 5) and dogs with acute occlusion of the left anterior descending (LAD] coronary artery [n = 11) were studied using a 1.5‐T NIR imager. ECG‐gated fast IR‐prepared GRE images were acquired using TI/TR/TE of 700/7.0/2.9 msec and a flip angle of 7°. Fast DE‐prepared GRE images were obtained using a flip angle of 12° and a DE delay /TR/TE of 60/10.2/4.2 msec. Sequential images were acquired to monitor transit of 0.06 mmol/kg gadodiamide injection and 0.2 and 0.4 mmol/kg sprodiamide injection. On slice‐nonselective IR fast GRE images. gadodiamide caused signiflcant enhancement of the normal myocardium and the left ventricular (LV) chamber blood. In dogs with LAD occlusion, the ischemic region was defined as an area of low signal intensity (SI). On DE‐prepared GRE sequences, administration of sprodiamide resulted in a substantial decrease in signal from normal myocardium and LV chamber blood in normal dogs. In animals subjected to LAD occlusion, this contrast medium produced a transient decrease in SI from normal myocardium [P<.06) and no signiflcant change in SI from ischemic myocardium. IR‐ and DE‐prepared taet GRE imaging can be used to monitor the transit of Tl‐enhancing and magnetic susceptibility contrast material in the heart. respectively. Cardiac image quality was much better when slice‐nonselective IR‐prepared fast GRE sequences were used

ISSN:1053-1807    

DOI:10.1002/jmri.1880050506

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

年代:1995

数据来源: WILEY

ISSN:1053-1807    

DOI:10.1002/jmri.1880050507

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe describe two methods of breast immobilization using the lateral decubitus position to increase patient comfort and access to the axillary tail for MR‐guided biopsy in the postsurgical or irradiated breast. The First method uses a compression device with good immobilization but poor patient tolerance. The second approach uses a thermoplastic mesh material to form a rigid exoskeleton around the breast: immobilization is adequate and patient acceptability is good. The latter method is prderred and requires formal evaluation in larger scale trial

ISSN:1053-1807    

DOI:10.1002/jmri.1880050508

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

年代:1995

数据来源: WILEY

摘要:

AbstractA simple algorithm named temporal phase unwrapping (TPU) is introduced to address the phase aliasing problem in time‐dependent pa contrast (CINE‐PC) velocity imaging. The method exploits the temporal continuity of velocity field and unwraps the phmc along time. TPU only involver a one‐dimensional (1D) temporal integration: therefore. many complications in 2D or 3D spatial phpee unwrapping are avoided. Differential velocity map (DVM) between adjacent movie framer arc first calculated from the complex MR imager. The DVM. have no phase aliasing no the differential velocities arc much smaller than the absolute velocities. ‐–free velocity maps are obtained by integrating the DVMs along the time direction provided M aliasing‐free reference velocity map (RVM) is found as a starting point of the integration. typically, much RVMs are always available within the cardiac cycle, especially in diastole where the blood flow is the lowest. In vivo rceults from fully automated processing and detailed discussion on noise behavior ar

ISSN:1053-1807    

DOI:10.1002/jmri.1880050509

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

年代:1995

数据来源: WILEY

摘要:

AbstractExperimental allergic encephalomyelitis (EAE) is a T cell‐mediated autoimmune disease of the CNS characterized by blood‐brain barrier breakdown. cerebral edema formation, lymphocyte infiltration, and demy‐elination, and is used as an animal model of multiple sclerosis (MS). MR imaging is important for the diagnosis of MS and for the evaluation of potential new therapier. In this study, T2‐weighted and T1‐weighted contrast‐enhanced MR imaging was used to evaluate the effectiveness of an antiadhesion therapy in EAE. Leukocyte‐endothelial adhesion at the blood‐brain barrier is considered an essential step in the mediation of CNS leukocyte infiltration in EAE.AN100226m. a monoclonal antibody to α4 integrin has been previously shown to reverse the clinical and histologic signs of EAE by blocking this interaction. In the present study, AN100226m treatment in acute EAE significantly decreased contrast enhancement of the CNS parenchyma indicating closure of the blood‐brain barrier. The percentage of pixele due to leakage of contrast material in T1‐weighted images decreased to<4% in AN100226m‐treated animals whereas it was increased to 15% in control animal (P<.05. Mann‐Whitney rank sum test). A decrease in CNS abnormalities associated with cerebral edema and inflammation was also obsaved on T2‐weighted images (P<‐05, Mann‐Whitney rank sum test). Thus, an antibody to α4 integrin reversed the blood‐brain barrier permeability changes characteristic of acute EAE. In addition, the further accumulation of innammatory edema was prevented a

ISSN:1053-1807    

DOI:10.1002/jmri.1880050510

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

年代:1995

数据来源: WILEY

ISSN:1053-1807    

DOI:10.1002/jmri.1880050511

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

年代:1995

数据来源: WILEY