摘要:

AbstractProton NMR spectroscopy has proven useful in the detection of cancer in lymph node tissue. However, due to the high fat content of this type of tissue, 2D1H COSY measurements (requiring acquisition times of 4–5 h or longer) are necessary to obtain the spectral information necessary for diagnosis.T2‐filtered proton magic‐angle spinning (MAS) NMR spectros‐copy provides 1D spectra of lymph nodes in approximately 20 min with sufficient spectral resolution allowing for identification of changes in cellular chemistry due to the presence of malignant cells. MAS data from lymph nodes of five control and six rats with mammary adenocarcinoma (R13762) demonstrated increases in the signal intensity of resonances associated primarily with lactate (s̀ = 4.12 ppm)P<0.0004, creatines/lysine (s̀ = 3.04 ppm)P<0.0032, and glutamate/ glutamine (s̀ = 2.36 ppm)P<0.0002 in metastatic compared with normal lymph nodes. The infiltration of lymph nodes by malignant cells is an important prognostic factor for many cancers. The rapid assessment of node tissue without the introduction of sampling errors (inherent in currently employed histological procedures) would allow postoperative therapy decisions to be made more e

ISSN:0740-3194    

DOI:10.1002/mrm.1910360502

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

年代:1996

数据来源: WILEY

摘要:

AbstractBroadband proton decoupling of the entire13C spectrum was possible within power absorption guidelines and resulted in the detection of narrow (as low as 2–3 Hz), natural abundance signals from metabolites such asmyo‐inositol, glutamate,N‐acetyl‐aspartate, and glutamine from 72 cm3volumes in the human brain. To overcome the chemical shift displacement error, three‐dimensional localization on the1H z magnetization was combined with polarization transfer. Efficiency of the heteronuclear localization method was demonstrated by the elimination of all scalp lipid resonances. A signal‐to‐noise ratio of 5:1 for 0.07 mM[13C] was achieved in 12 min, which is approximately a fivefold improvement over the sensitivity reported

ISSN:0740-3194    

DOI:10.1002/mrm.1910360503

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

年代:1996

数据来源: WILEY

摘要:

AbstractGlycosaminoglycans (GAGs) are the main source of tissue fixed charge density (FCD) in cartilage, and are lost early in arthritic diseases. We tested the hypothesis that, like Na+, the charged contrast agent Gd‐DTPA2‐(and hence protonT1) could be used to measure tissue FCD and hence GAG concentration. NMR spectroscopy studies of cartilage explants demonstrated that there was a strong correlation (r>0.96) between protonT1in the presence of Gd‐DTPA2‐and tissue sodium and GAG concentrations. An ideal one‐compartment electrochemical (Donnan) equilibrium model was examined as a means of quantifying FCD from Gd‐DTPA2‐concentration, yielding a value 50% less but linearly correlated with the validated method of quantifying FCD from Na+. These data could be used as the basis of an empirical model with which to quantify FCD from Gd‐DTPA2‐concentration, or a more sophisticated physical model could be developed. Spatial distributions of FCD were easily observed inT1‐weighted MRI studies of trypsin and interleukin‐1 induced cartilage degradation, with good histological correlation. Therefore, equilibration of the tissue in Gd‐DTPA2‐gives us the opportunity to directly image (throughT1, weighting) the concentration of GAG, a major and critically important macromolecule in cartilage. Pilot clinical studies demonstrated Gd‐DTPA2‐penetration into cartilage, suggesting that this tec

ISSN:0740-3194    

DOI:10.1002/mrm.1910360504

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

年代:1996

数据来源: WILEY

摘要:

AbstractA standard differential calculus‐based propagation of error treatment is applied to the traditional chemical‐exchange Henderson‐Hasselbalch NMR pH model in which the reference shift is pH independent. It is seen naturally from this analysis that (i) the error minimum in derived pH occurs in the region where pH and indicator pKaare equal and that (ii) the dynamic range, or difference between the limiting chemical shifts of acid and base forms of indicator species, determines the insensitivity of the technique to propagation of errors. To extend the useful pH range and utility of NMR pH determination methodology, a more general model is developed in which the internal reference species is also considered as having a pH‐dependent chemical shift. Data from standard solution pH titrations are fitted to both models and parameters are estimated for the normally observed family of ionizable phosphorus metabolites (ATP, inorganic phosphate, phosphoethanolamine and phosphocholine) and the xenometabolite 2‐deoxyglucose‐6‐phosphate with either phospho‐creatine, the α‐phosphate of ATP, or H2O taken as the31P or1H chemical shift internal reference species as well as with an

ISSN:0740-3194    

DOI:10.1002/mrm.1910360505

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe partition coefficient of Gd‐DTPA was thought to vary with the amount of cellular membrane damage after an acute myocardial infarction. The relationship between the partition coefficient of Gd‐DTPA (λ) and the uptake of201TI (as a marker of tissue viability) was studied 2 h to 3 weeks after reperfusion of a 2‐h occlusion to the left anterior descending coronary artery in a canine model. Gd‐DTPA was infused as a bolus followed by a prolonged constant infusion, and this infusion protocol was optimized such that the concentration of Gd‐DTPA was directly related to λ. After this infusion, MR images of excised hearts showed regions of increased signal intensity corresponding to increased Gd‐DTPA concentration. At all time points, λ and201TI uptake were strongly negatively correlated indicating that λ is an accurate indicator of myocardial viability. Furthermore, λ in the infarcted regions was increased relative to normal regions after 2 h of reperfusion and stayed elevated up to 3 weeks. At all time points, λ in the infarcted and normal regions were significantly different. As well, this data showed a trend that λ in infarcted regions decreased monotonically from 1 day to 3 weeks. This trend was confirmed with MR imaging by examining the change in signal intensity ofin vivoimages from 4 days to 3 weeks in two animals. These results suggest that MRI with Gd‐DTPA could be used to measure the extent of myocardial damage after an acute m

ISSN:0740-3194    

DOI:10.1002/mrm.1910360506

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe use of pH‐sensitive probes permits the measurement of the proton activity in biological systems by EPR spectroscopy. To illustrate the potential of this technique forin vivopurposes, the authors took advantage of the oral administration of nitroxides to monitor the pH value inside the stomach of mice after administration of different antacidics. The results indicate that EPR can be a valuable tool to characterize the pHin vivoin a continuous and noninvasive wa

ISSN:0740-3194    

DOI:10.1002/mrm.1910360507

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

年代:1996

数据来源: WILEY

摘要:

AbstractUncertainty regarding the intracellular/extracellular distribution of inorganic phosphate (Pi) in tumors has raised concerns that pH calculated from the tumorPichemical shift may not accurately represent the intracellular pH (pHin). This issue was addressed in subcutaneously transplanted murine radiation induced fibrosarcoma‐1 by directly comparing pH measured viaPiwith pH measured via thein situgeneratedintracellularxenometabolite 2‐deoxyglucose‐6‐phosphate (2DG6P). In 131 comparative measurements employing eight tumor‐bearing mice under both control and hyperglycemic conditions (the latter to extend the range of tumor pH examined), the pH as derived from either 2DG6P orPishowed only a small, but statistically significant, difference (0.07 ± 0.11 SD;P= 0.0001). Scatter in the comparative analysis over the pH range examined (ca.5.5‐7.5) was not uniform. Above pH 6.6, 2DG6P indicated a pH lower than that ofPiby 0.088 ± 0.105 SD (n= 107,P= 0.0001); below pH 6.6, 2DG6P indicated a pH essentially identical to and not statistically different from that ofPi(mean difference 0.003 ± 0.128 SD (n= 24,P= 0.92)). Evidence is presented in support of this differential arising from a systematic measurement error due to peak overlap between 2DG6P and endogenous phosphomonoester species. These results support the use ofPias a tumor31P NMR pHinindicator, at least in RIF‐1 tumors under control and hypergly

ISSN:0740-3194    

DOI:10.1002/mrm.1910360508

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

年代:1996

数据来源: WILEY

摘要:

AbstractFinite element analysis was used to calculate the static magnetic field within the three‐dimensional head model. Localized field distributions were evaluated by using the magnetic field histogram technique. Experimental field maps and histograms of the human head were also obtained to validate the simulation results. Field deviations and gradients inside the human head cause NMR signal frequency shifts and line broadening, respectively. Voxels 2 × 2 × 0.5 cm may have frequency differences of more than 2.0 ppm. The linewidth of a single voxel may be broadened by more than 0.5 ppm. Calculated and experimental field maps are in excellent agreement. The global field distortion in the human head is primarily due to the susceptibility difference between air and tissues and their corresponding geometrical sha

ISSN:0740-3194    

DOI:10.1002/mrm.1910360509

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe authors review the theoretical basis of determination of cerebral blood flow (CBF) using dynamic measurements of nondiffusible contrast agents, and demonstrate how parametric and nonparametric deconvolution techniques can be modified for the special requirements of CBF determination using dynamic MRI. Using Monte Carlo modeling, the use of simple, analytical residue models is shown to introduce large errors in flow estimates when actual, underlying vascular characteristics are not sufficiently described by the chosen function. The determination of the shape of the residue function on a regional basis is shown to be possible only at high signal‐to‐noise ratio. Comparison of several nonparametric deconvolution techniques showed that a nonparametric deconvolution technique (singular value decomposition) allows estimation of flow relatively independent of underlying vascular structure and volume even at low signal‐to‐noise ratio associated with pixel‐by‐pixel de

ISSN:0740-3194    

DOI:10.1002/mrm.1910360510

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

年代:1996

数据来源: WILEY

摘要:

AbstractThis report evaluates several methods to map relative cerebral blood flow (rCBF) by applying both parametric and non‐parametric techniques to deconvolve high resolution dynamic MRI measurements of paramagnetic bolus passages with noninvasively determined arterial inputs. We found a nonparametric (singular value decomposition (SVD)) deconvolution technique produced the most robust results, giving mean gray:white flow ratio of 2.7 ± 0.5 (SEM) in six normal volunteers, in excellent agreement with recent PET literature values for age‐matched subjects. Similar results were obtained by using a model‐dependent approach that assumes an exponential residue function, but not for a Gaussian‐shaped residue function or for either Fourier or regularization‐based model‐independent approaches. Pilot studies of our CBF mapping techniques in patients with tumor, stroke, and migraine aura demonstrated that these techniques can be readily used on data routinely acquired by using current echo planar imaging technology. By using these techniques, the authors visualized important regional hemodynamic changes not detectable with rCBV mappin

ISSN:0740-3194    

DOI:10.1002/mrm.1910360511

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

年代:1996

数据来源: WILEY