摘要:

AbstractA highly specific and powerful magnetic resonance imaging contrast agent has been prepared by coating magnetite (Fe3O4) particles with monoclonal antibodies directed against a tumor antigen. The preparation maintains both the immunoreactivity of the monoclonal antibody and the full relaxing capability of the magnetite particle. MRI image contrast by spin‐echo methods can be easily induced in a concentration range of 1–10 nMof the antibody‐coated magnetite particles. © 1989 Academic Pres

ISSN:0740-3194    

DOI:10.1002/mrm.1910120202

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

年代:1989

数据来源: WILEY

摘要:

AbstractA23Na NMR assay for measurement of erythrocyte Na+/K+ATPase activity is presented. Using the nonpermeant shift reagent dysprosium tripolyphosphate the signals of intra‐ and extracellular sodium are separated, enabling measurement of sodium fluxes nondestructively, without the need to physically separate the cells from their environment. By increasing membrane permeability with nystatin we have shown that the assay allows the detection of differences in membrane permeability. With low doses of nystatin the ouabain‐sensitive sodium flux increased more than twofold. With high doses of nystatin the Na+/K+pump could not prevent an almost total equilibration of intra‐ and extracellular sodium. All sodium that entered the cells remained NMR visible, proving that sodium influx can be measured quantitatively.31P NMR spectra taken before and after the assay revealed a slight acidification of the cells and no significant change in ATP concentration. No evidence of Dy3+entering the cell was observed. © 1989 Academic Pres

ISSN:0740-3194    

DOI:10.1002/mrm.1910120203

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

年代:1989

数据来源: WILEY

摘要:

AbstractFetal brain metabolism was investigatedin uterononinvasively using multinuclear nuclear magnetic resonance spectroscopy in rats at two representative prenatal stages: early (17‐18 days) and late (20‐21 days) stages. Phosphorus‐31 (31P) spectroscopy revealed that phosphocreatine is significantly lower in the early stage and increases to the level of early neonates by the late prenatal stage. Intracellular pH at the early stage was found to be strikingly high (7.52 ± 0.21) and decreased to a level similar to that of neonates by the late stage (7.29 ± 0.07). Phosphomonoester levels at both stages were similar to the values reported for early neonates. Water‐suppressed proton (1H) spectroscopy demonstrated a distinctivein vivofetal brain spectral pattern characterized by low levels ofN‐acetyl aspartate and high levels of taurine. High‐resolution proton spectroscopy and homonuclear chemical‐shift correlate spectroscopy of brain perchloric acid extracts confirmed thesein vivofindings.In vitro31P spectroscopy of acidified chloroform methanol extracts showed the characteristic membrane phospholipid profiles of fetal brain. The phosphatidylethanolamine (PE)‐to‐phosphatidylcholine (PC) ratio (PE/PC) did not show significant changes between the two stages at 0.40 ± 0.11, a value similar to that of early neonates. © 198

ISSN:0740-3194    

DOI:10.1002/mrm.1910120204

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

年代:1989

数据来源: WILEY

摘要:

AbstractSeventy‐six aortic and mitral valves, in 44 patients and 5 normal volunteers, were studied by Cine‐Flow MRI (on a 0.26‐T superconducting magnet system), utilizing compound oblique imaging planes and a Field Echo Even Rephasing sequence. All patients had had cardiac catheterization and echocardiography. All patients with valvular stenosis and aortic sclerosis (n= 45) showed complete signal loss distal to the respective valve. Length of signal loss distal to the aortic valve in those in whom it was measured (n= 15) allowed differentiation of aortic stenosis (n= 9) from sclerosis (n= 6). This also permitted grading of stenosis with highly significant correlation (T= 0.86;P<0.002) with pressure gradient measurement. In mitral stenosis (n= 12) calculation of the area of signal loss distal to the mitral valve as a percentage of left ventricular cross‐sectional area showed a highly significant correlation (T= 0.77;P= 0.001) with pressure gradient measurement. Clinically significant valvular regurgitation was graded by size and duration of signal loss proximal to the valve with concordance with angiocardiography. It is concluded that Cine‐Flow MRI has a clinical role in the diagnosis and assessment of valvular heart disease. © 1989 Academic

ISSN:0740-3194    

DOI:10.1002/mrm.1910120205

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

年代:1989

数据来源: WILEY

摘要:

AbstractSevere motion and flow artifacts are a problem in MRI of diffusionin vivodue to the application of strong magnetic field gradients. Here it is shown that image artifacts can be removed by using a modified fast‐scan MRI sequence (CE‐FAST) in conjunction with averaging of diffusion‐weighted images. In phantom studies slow (coherent) flow (<1 mm s‐1) in the presence of strong diffusion gradients is shown to cause signal losses in diffusion‐weighted images that depend on the relative orientations of the flow direction and the diffusion gradient. On the other hand, pulsatile motions of macroscopic dimensions (e.g. 1 mm, 1 Hz, in‐plane) lead to smearing and ghosting of signal intensities along the phase‐encoding direction of the images. In both phantoms and rabbit brainsin vivomotion artifacts were found to be reducible by averaging 8‐16 images. Unfortunately. the resulting image contrast no longer represents a “true” diffusion contrast but is affected by additional signal losses due to motion averaging. All experiments were performed on a 40‐cm‐borc 2.35‐T Bruker Medspee system.

ISSN:0740-3194    

DOI:10.1002/mrm.1910120206

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

年代:1989

数据来源: WILEY

摘要:

AbstractA method for the volume‐and resonance line‐selective determination of the longitudinal relaxation time in the rotating frame,T1ρ, is described. The spin‐lock pulse intrinsic to theT1ρsequence simultaneously replaces the first slice‐selective pulse of the VOSY method for localized spectroscopy. This is a further parameter suitable for the local characterization of tissue. On the same basis,T1ρ, can be used as a new contrast parameter for biomedical imaging purposes. An appropriate pulse sequence forT1ρimagingis presented. Test experiments which promise some striking advantages compared with conventional magnetic resonance imaging are reported. © 1989 Academi

ISSN:0740-3194    

DOI:10.1002/mrm.1910120207

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

年代:1989

数据来源: WILEY

摘要:

AbstractSurface coil NMR spectroscopy was used to monitor the hyperglycemia‐induced alterations in pH and blood flowin vivoin C6 gliomas implanted both subcutaneously and intracerebrally in rats. Tumor pH was calculated from the chemical shift difference between PCr andPiin the31P NMR spectra. Subcutaneous glioma pH decreased 0.8 units by 1 h after intraperitoneal administration of an aqueous 50% glucose solution (6 g glucose per kg body weight). In contrast, hyperglycemia failed to significantly alter the pH of intracerebral gliomas which were monitored for 90 min following administration of glucose. Tumor blood flow (TBF) was determined both pre‐ and post‐glucose administration using deuterium NMR by monitoring the time course of D2O washout following intratumoral injection of saline D2O. Subcutaneous and intracerebral TBF were found to have an average change of‐78.1 % (range ‐47.4 to ‐93.3%,n =5) and ‐21.1% (range +6.0 to ‐37.8%,n= 9), respectively. In addition, laser Doppler blood flow measurements of rat skin and subcutaneous glioma revealed a dramatic reduction in blood flow in both tissues following glucose administration. These results indicate that the effects of acute hyperglycemia are site dependent and that hyperglycemia alone is not beneficial for inducing intracellular acidosis in intracerebral tumors. © 1989 Aca

ISSN:0740-3194    

DOI:10.1002/mrm.1910120208

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

年代:1989

数据来源: WILEY

摘要:

AbstractLineshapes of spectra obtained through chemical‐shift imaging are often distorted due to the delay in sampling necessary for application of phase‐encoding gradients. We have developed an automated fitting procedure which simultaneously performs signal quantification, phase correction, and baseline deconvolution of such spectra. The fit is based on the maximum likelihood method and can be implemented in either the time or the frequency domain. © 1989 Academic Press,

ISSN:0740-3194    

DOI:10.1002/mrm.1910120209

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

年代:1989

数据来源: WILEY

摘要:

AbstractHydrogen, sodium, and fluorine (added F‐) NMR spectra of venous and oxygenated blood were measured. The fluorine resonance was seen as a single peak in both samples, and all three resonances exhibited the same deoxy‐oxy shift. Because F‐exchanges slowly across the red cell membrane, and because sodium is 95% extracellular, these results suggest that the intra‐extracellular field differenceΔBis less than 0.1 ppm. A small value ofΔBtends to rule out transmembrane exchange as an important contributor to relaxation in MRI of blood and hematomas. However, the broadening of the resonances with deoxygenation, by 0.3‐0.4 ppm, indicates that both intra‐ and extracellular gradients are of comparable and sufficient magnitude to produce the T2‐weighted hypointensity seen in clinical magnetic resonance images of hematomas at high fields. © 1989 Aca

ISSN:0740-3194    

DOI:10.1002/mrm.1910120210

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe efficiency of31P homonuclear decouplingin vivois demonstrated. In low‐field clinical situations, whenJppis equal to or greater than Δvsignificant improvements in the precision of measuring the ATP resonance area can be expected upon decoupling due to the increase in signal‐to‐noise produced upon collapse of theJcoupling. The sensitivity loss due to time sharing between the decoupler and receiver is discussed. © 1989 Academic Pre

ISSN:0740-3194    

DOI:10.1002/mrm.1910120211

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

年代:1989

数据来源: WILEY