摘要:

AbstractA method is proposed for calculating images of spin densitypand relaxation timesT1T2from MR imaging sequencies with the following characteristics:•it avoids nonlinear iterative techniques and is consequently sufficiently fast to allow calculation ofp,T1and T2on a pixel by pixel basis routinely;•it uses all available data simultaneously in an approximately optimal fashion.The method is applied to the combined SE + IR sequence but can be used for other acquisition Schemes as Well. © Academic Press,

ISSN:0740-3194    

DOI:10.1002/mrm.1910050602

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

年代:1987

数据来源: WILEY

摘要:

AbstractWith an eye toward the development of nitroxides as potential contrast enhancing agents for MRI applications, we have compared the rates of reduction of 24 nitroxides of diverse structures by rat whole liver homogenate, hepatocytes, subcellular fractions, and ascorbate (10 eq excess). Our results indicate that five‐membered ring nitroxides and α‐carboxy α‐aryltert‐butyl nitroxides are significantly more resistant toward bioreduction than six‐membered ring and heterocyclic‐substituted nitroxides in all systems. In the case of six‐membered ring nitroxides the presence of either negatively charged or positively charged groups increases the susceptibility toward ascorbate reduction. The presence of carboxylate groups tends to enhance the resistance of all the nitroxides toward reduction by liver homogenate, hepatocytes, and subcellular fractions.trans‐Azethoxyl nitroxides exhibited the best overall resistance toward bioreduction. TheT1relaxivities of selected nitroxides were measured and found to be similar. © A

ISSN:0740-3194    

DOI:10.1002/mrm.1910050603

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

年代:1987

数据来源: WILEY

摘要:

AbstractTheT1andT2NMR relaxation times of water protons in plasma, obtained from patients with lung carcinoma, healthy volunteers, and patients with nontumor diseases were measured at a resonance frequency of 20 MHz. Additionally hematologic parameters were determined. In tumor patients the mean plasmaT2was shortened by about 20%, and an increase in the blood sedimentation rate (BSR) was noted. Similar but less pronounced results were found for the nontumor group of patients, indicating that the shortening ofT2in plasma is a secondary host response. However, a plot of plasma 1/T2versus BSR from tumor patients showed a significant correlation between these two parameters. No such correlation could be detected in the nontumor group of patients. The correlation of 1/T2with BSR, found solely in the tumor patient group, increased the diagnostic sensitivity ofT2measurements and may help to differentiate between malignant and nonmalignant disease. No significant variation in theT1spin‐lattice relaxation time was observed. © Academic Press, I

ISSN:0740-3194    

DOI:10.1002/mrm.1910050604

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn this study sequential1H and19F magnetic resonance imaging methods were used to map the distribution of fluorinated compoundsin vivo.An intravenously administered emulsion of perfluorooctylbromide (PFOB), an agent known to localize in the reticuloendothelial system, was detected in the liver and spleen of all studied hamsters and mice using19F MRI. Lungs and salivary glands were also affected in some animals. Using a G. E. NMR CSI 2‐T spectroscopy/imaging system, projection19F images were obtained in 4 to 8 min. Subsequent mouse studies using a thick‐slice driven equilibrium pulse sequence produced19F images with an improved signal‐to‐noise ratio in a shorter acquisition time. With PFOB,19F MRI has the capability of detecting macrophages in the reticuloendothelial system and in other sites where macrophages congregate. This is the first report where the reticuloendothelial system was specifically imaged in live animals and where driven equilibrium imaging techniques have been applied to19F MRI. © Academic Pr

ISSN:0740-3194    

DOI:10.1002/mrm.1910050605

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

年代:1987

数据来源: WILEY

摘要:

AbstractMost phantom media in current use exhibitT1relaxation times that are significantly dependent on both temperature and operating frequency. This can introduce undesirable variability into relaxation measurements due to temperature fluctuations, and complicates direct comparison of imagers operating at different magnetic field strengths. Our investigations of a nickel‐doped agarose gel system have demonstrated near independence of the proton relaxation rates to a wide range of temperatures and frequencies. We therefore propose the adoption of Ni2+as a relaxation modifier for phantom materials used as relaxometry standards. © Academic Press, I

ISSN:0740-3194    

DOI:10.1002/mrm.1910050606

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

年代:1987

数据来源: WILEY

摘要:

AbstractProton magnetic resonance (MR) body images of the normal, adult human which have total scan times of typically only 40 ms per image are presented. There is no loss of spatial or contrast resolution due to motional blurring or ghosting; rather, movie loops of multiple 40‐ms images directly demonstrate normal respiratory and peristaltic motion. Manifestation of „traditional”︁ relaxation time contrast is demonstrated for a variety of spin echo (TE) and image repetition (TR) times. The images, obtained at 2.0 T on a new high‐speed MR system, have a signal‐to‐noise ratio for muscle of approximately 30:1 (TE = 30 ms) for a 4.7‐mm slice thickness (voxel size = 0.08 cm3). In a study presented as an example, 140 images covering the body from diaphragm to pelvis were all obtained within approximately 10 min. This method may help improve the efficacy of MR body imaging in general, and may play a role in applications which require high temporal resolution. © Aca

ISSN:0740-3194    

DOI:10.1002/mrm.1910050607

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

年代:1987

数据来源: WILEY

摘要:

AbstractNMR studies of living cells and of perfused organs almost invariably require a major effort in the design of either the probe or the support system. For enriched13C studies of metabolism, it is sometimes possible to use a simpler approach, one amenable to use in narrow‐bore high‐resolution NMR spectrometers. Since some of the metabolic changes are reflected by changes in the chemical composition of the media, it may be necessary to provide only for NMR measurements of the perfusate. A simple apparatus is described which allows NMR measurement of the perfusate. A commercially available concentric NMR tube, modified to incorporate flow, is inserted in the flow loop and placed in the spectrometer. An example is given of the metabolism of13C‐enriched glucose to lactate by chick embryo fibroblasts grown in a hollow fiber bundle assembly. © Academic Pres

ISSN:0740-3194    

DOI:10.1002/mrm.1910050608

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

年代:1987

数据来源: WILEY

摘要:

AbstractAn intense peak is visible in the phosphodiester region of the31P NMR spectra of human colon adenocarcinoma HCT‐8R cells. A signal at the same frequency, partially deriving from mobile phospholipids, is also observable in the spectra of total membranes and of perchloric acid extracts prepared from the same cells. The phosphodiester signals of glycerophosphorylcholine, glycerophosphorylethanolamine, and glycerophosphorylserine resonate at lower fields with respect to this broader peak and appear only in aged samples. Enzymatic treatments of the extracts would indicate that ribonucleic acid also contributes to the broad phosphodiester signal. Moreover,1H NMR spectra show the presence of lipid structures, characterized by high mobility, in the cell and in the membrane samples, similar to what was already observed in other tumor cells and tissues. © Academic Press, I

ISSN:0740-3194    

DOI:10.1002/mrm.1910050609

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

年代:1987

数据来源: WILEY

摘要:

AbstractA novel method for reducing the rf power requirements of selective pulses employed forzmagnetization slice inversion in localized NMR spectroscopy is presented. Following slice preparation by the use of frequency‐incremented sine pulses, the slice gradient is reduced, which narrows the frequency width of the slice. This allows the use of relatively low‐power selective inversion pulses, an important consideration forin vivoapplications. © Academic Press,

ISSN:0740-3194    

DOI:10.1002/mrm.1910050610

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

年代:1987

数据来源: WILEY

ISSN:0740-3194    

DOI:10.1002/mrm.1910050601

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

年代:1987

数据来源: WILEY