ISSN:0740-3194    

DOI:10.1002/mrm.1910380402

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe reduction of chromate (Cr(VI)) on the skin of living rats was investigated using the technique ofin vivoelectron paramagnetic resonance (EPR) spectroscopy with a surface coil resonator. Topical application of aqueous solution of Cr(VI) on the skin of rats generated the transient species, Cr(V). Partial removal of the stratum corneum increased the rates of formation and decay of Cr(V), as well as Cr(V) signal intensity. The results demonstrate that skin represents one route for chromium to enter into animals and humans. The generation of reactive Cr(V) species in the reduction of Cr(VI) by the skin may play an important role in the mechanism of Cr(VI)‐induced skin cancer. These findings indicate the potential forin vivoEPR spectroscopy for studying the metabolism of paramagnetic reactive species in chemical and biochemical reactions occurring in/on the skin of both small and large animals, and possibly human

ISSN:0740-3194    

DOI:10.1002/mrm.1910380403

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

年代:1997

数据来源: WILEY

摘要:

AbstractAlthough RARE and GRASE can produce single‐shot images of excellent quality, their utility has been restricted because preparation of the magnetization with interesting contrast before imaging can cause severe artifacts. These artifacts relate to the strong sensitivity of multiple spin echo sequences to the phase of the prepared magnetization. Modifications of the RARE sequence to eliminate these artifacts are discussed, and an approach that eliminates the artifact producing signals from the very first echo is presented. The approach is applied to diffusion imaging of the human brain in normal volunteers and one patien

ISSN:0740-3194    

DOI:10.1002/mrm.1910380404

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

年代:1997

数据来源: WILEY

摘要:

AbstractA modified BURST imaging technique with a nearly twofold reduction in acquisition time, improved signal‐to‐noise ratio and clear improvement of the image quality is introduced. The method applies half‐Fourier reconstruction and can be implemented on a standard clinical scanner. This approach allows the collection of single‐shot magnetization prepared images of the human brain with a matrix size of 112 × 128 within 86‐250 ms. The signal‐to‐noise properties of the pulse sequence are analyzed and compared with a standard BU

ISSN:0740-3194    

DOI:10.1002/mrm.1910380405

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

年代:1997

数据来源: WILEY

摘要:

AbstractQuantifiable MRI perfusion studies using the contrast agent Gd‐DTPA require measurement or estimation of the tissue partition coefficient (λ) for tracer kinetic modeling. Radiotracer techniques were used to obtain regional λ measurements from the left ventricles of five dogs. Measurements were analyzed to determine whether spatial heterogeneity was a major component of λ variability. No systematic variations were identified in terms of radial position, short‐axis slice location, or wall position. The high λ variability seen in this study and in cited data of others may be due in part to tissue heterogeneity in interstitial volume, plasma volume, and perfusate hem

ISSN:0740-3194    

DOI:10.1002/mrm.1910380406

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

年代:1997

数据来源: WILEY

摘要:

AbstractReduction of image‐to‐image signal fluctuations and imaging artifacts is important for fMRI studies. The imaging artifacts caused by respiration, cardiac pulsation, and gross head motion and the suppression of these artifacts have been studied for many years. However, the artifacts caused by eye movement and their effects on fMRI mapping are not well known. It is demonstrated in this report that involuntary eye movements during resting conditions can cause substantial signal fluctuations in the phase‐encoding direction even for a fast echo‐planar imaging sequence. An oblique slab presaturation technique is proposed for saturating the magnetization of eyes and suppressing the artifacts from eye movements with minimal signal loss of other brain tissues. The results show that the technique significantly reduces signal fluctuations and improves fMRI reliability for mapping functional activation in the huma

ISSN:0740-3194    

DOI:10.1002/mrm.1910380407

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

年代:1997

数据来源: WILEY

摘要:

Abstract31P magnetic resonance spectroscopy was used to investigate changes in high energy phosphate levels and creatine kinase (CK) kinetics induced in the human visual cortex during photic stimulation. CK kinetics was evaluated by measuring the apparent unidirectional rate constant (kf) in the “forward” direction (i.e., in the direction of ATP synthesis from phosphocreatine).kfincreased 34% in the visual cortex areas during stimulation without significant changes of steady‐state concentration of high energy phosphate compounds, indicating that CK turnover is elevated during increased neuronal act

ISSN:0740-3194    

DOI:10.1002/mrm.1910380408

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

年代:1997

数据来源: WILEY

摘要:

AbstractImperfections in the slice profile of the adiabatic inversion induced by relaxation effects are shown to cause signal variations in pulsed arterial tagging schemes on the order of magnitude of perfusion changes, and result in gross errors in perfusion quantitation. Significant improvement can be made with minor modifications to the inversion pulse which facilitate the acquisition of quantitative, multislice perfusion images, as demonstrated in both a phantom and a normal human volunteer.

ISSN:0740-3194    

DOI:10.1002/mrm.1910380409

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe authors have shown direct, real‐time,in vivomeasurement of nitric oxide (NO) in mice by using the water soluble metal chelator complex,N‐methyl‐D‐glucamine dithiocarbamate (MGD), and Fe(II) as monitored by EPR at L‐band. The three‐line EPR spectrum from the product [(MGD)2‐Fe(II)‐NO] was observed noninvasively in lipopolysaccharide (LPS)‐treated mice. The spectrum was markedly suppressed by the administration, before LPS injection, of phenylN‐tert‐butyl nitrone (PBN), an inhibitor of the expression of induced nitric oxide synthase (iNOS). When15N‐arginine was administered to LPS‐treated mice, a diagnostic EPR spectrum was observed, consisting of both three‐ and two‐line EPR signals, due to (MGD)2‐Fe(II)‐14NO and (MGD)2‐Fe(II)‐16NO, respectively. The results strongly suggested that the NO detected in these experiments was synthesized by iNOS.In vivoEPR measurements of [(MGD)2‐Fe(II)‐NO] at several regions in the body (from the head to the tail) indicated that the NO was generated mostly in the upper abdomen near the liver. These observations were confirmed byex vivoEPR measurements on isolated organs where higher NO levels were detectedin vivoin the liver and kidney. The spectroscopic results, combined with the pharmacokinetic data, support the model that NO detected in LPS‐treated mice was produced mainly in the liver, and that it did not reflect NO‐adduct complex accum

ISSN:0740-3194    

DOI:10.1002/mrm.1910380410

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

年代:1997

数据来源: WILEY

摘要:

AbstractProton (1H) magnetic resonance (MR) spectra ofex vivobiopsy samples of ovarian cancers provided biochemical information that was used to discriminate cancer from normal ovarian tissue. Possible differences present in intrinsically resistant tumors or changes in biochemistry after the induction of resistance were identified. Using multivariate techniques, in particular linear discriminant analysis (LDA), ovarian cancer was distinguished from normal ovarian tissue with a sensitivity of 100%, a specificity of 95% and an accuracy of 98%. Moreover, LDA was able to distinguish untreated ovarian cancer from recurrent ovarian cancer with a sensitivity of 92%, a specificity of 100%, and an accuracy of 97%; removal of the single “fuzzy” specimen increased the accuracy to 100%. Applications of this knowledge toin vivomeasurements could lead to noninvasive diagnosis of ovarian can

ISSN:0740-3194    

DOI:10.1002/mrm.1910380411

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

年代:1997

数据来源: WILEY