bluuebunny/crossref_metadata_2025 huggingface dataset:
A proton relaxation enhancement investigation of the binding of fatty acid spin labels to human serum albumin
Authors: Slane Jean M. K. , Lai Ching‐San , Hyde James S.
Published: March 2007

Proton relaxation enhancement (PRE) values for fatty acid spin labels bound to human serum albumin have been investigated using the inversion‐recovery method at 24 MHz. At 0.1 mM protein concentration and a label‐to‐protein ratio of one‐to‐one, the PRE value for 12‐Doxylstearate‐albumin complex is 7.8 ± 2.3, whereas the PRE values for 5‐Doxylstearate and 16‐Doxylstearate‐albumin complexes are 1.5 ± 0.6 and 1.7 ± 0.7, respectively. Addition of 10‐fold excess of stearic acid reduced the PRE values nearly to 1, indicating that the strong enhancements arise from direct binding of fatty acid spin labels to human serum albumin. PRE values for all three labels exhibit maxima as a function of the label‐to‐protein ratio, suggesting multiple binding sites for fatty acid spin labels with labels in the tightest binding sites not resulting in the most effective relaxation. Based on the rates of reduction of ESR signal amplitudes by sodium ascorbate, the difference in PRE values for the three fatty acid spin labels bound to albumin is attributed to the difference in water accessibility of the nitroxide moieties at various positions along the acyl chain, being greater at the C‐12 position than at C‐5 or C‐16 position. The PRE value of 8 for 12‐Doxylstearate bound to human serum albumin indicates that this complex may be a suitable paramagnetic contrast agent for in vivo NMR imaging. © 1986 Academic Press, Inc.
Gd(DOTA): An alternative to Gd(DTPA) as a T1,2 relaxation agent for NMR imaging or spectroscopy
Authors: Magerstädt Michael , Gansow Otto A. , Brechbiel Martin W. , Colcher David , Baltzer Lars , Knop Richard H. , Girton Mary E. , Naegele Matthias
Published: March 2007

Methods have been devised for obtaining gadolinium(III) complexes of the ligands NOTA (1, 4, 7‐triazacyclononane‐N, N′, N″‐triacetic acid), DOTA (1, 4, 7, 10‐tetraazacyclododecane‐N, N′, N″, N‴‐tetraacetic acid), TETA (1,4,8,11‐tetraazacyclotetradecane‐N, N′, N″, N‴‐tetraacetic acid), and DTPA (diethylenetriaminepentaacetic acid) as solids for use as pharmaceuticals. Their effectiveness as in vitro and in vivo contrast agents for NMR imaging or T1,2 relaxation agents for spectroscopy has been investigated. The Gd(DOTA) complex was shown to be a more stable alternative to Gd(DTPA) by serum stability studies and measurement of stability constants. Images of tumors grown in athymic mice were obtained by NMR after injection of Gd(DOTA) and Gd(DTPA). © 1986 Academic Press, Inc.
31P NMR measurements of T2 relaxation times of ATP with surface coils: Suppression of J modulation
Authors: Albrand J. P. , Foray M. F. , Decorps M. , Remy C.
Published: March 2007

The efficiency of selective refocusing pulses to suppress J modulation of spin echoes when using the surface‐coil technique has been investigated. 31P T2 values obtained for ATP by the HAHN spin‐echo method remain in good agreement when the standard refocusing pulse is replaced by selective pulses based on the DANTE excitation method. © 1986 Academic Press, Inc.
Tissue distribution and stability of metalloporphyrin MRI contrast agents
Authors: Lyon R. C. , Faustino P. J. , Cohen J. S. , Katz A. , Mornex F. , Colcher D. , Baglin C. , Koenig S. H. , Hambright P.
Published: March 2007

Mn(III), Fe(III), and Gd(III) complexes of tetrakis(4‐sulfonatophenyl)porphyrin (TPPS) and several other porphyrins were evaluated as potential MRI contrast agents. Based on consideration of relaxivity and stability properties in solution, Mn TPPS was found to be the compound of choice. At pH 7 the Gd and Mn complexes significantly enhanced the water proton relaxation rate, while the relaxivity of Fe TPPS exhibited a significant loss of relaxivity above pH 6 due to oxy‐dimer formation. Although GdTPPS exhibited the highest relaxivity in solution, this property was rapidly lost due to dissociation of the metal ion. By contrast MnTPPS remained stable in human plasma after incubation for 9 days. Upon intravenous injection into athymic mice bearing subcutaneous human colon carcinoma xenografts, MnTPPS provided enhanced relaxation of the tissue water in several excised mouse tissues, notably kidney, liver, and tumor. The results at a fixed field (0.25 T) and relaxation dispersion studies showed decreases in water relaxation rates with time for kidney and liver, but an increase for the tumor, with a maximum near 4 days at the highest dose used.
The flip‐angle effect: A method for detection of sodium‐23 quadrupole splitting in tissue
Authors: Joseph Peter M. , Summers Ronald M.
Published: March 2007

A method is presented for the detection of quadrupole splitting in tissue, where the spectral line splittings are typically unobservable. The method used is a study of the rate of rotation of the flip angle as a function of radiofrequency (rf) amplitude. Our results with samples of skeletal muscle and cat brain indicate the absence of quadrupole splitting. © 1987 Academic Press, Inc.
Maximum entropy method in phase‐encoding NMR imaging
Authors: De Simone B. C. , De Luca F. , Maraviglia B.
Published: March 2007

Results are reported which demonstrate that the maximum entropy method can be applied to phase‐encoding NMR imaging. © 1987 Academic Press, Inc.
In vivo31P NMR spectroscopy of agonist‐stimulated phosphatidylinositol metabolism in cat brain
Authors: Renshaw Perry F. , Schnall Mitchell D. , Leigh John S.
Published: March 2007

As a result of the agonist stimulation of muscarinic receptors, myc‐inositol‐1 ‐phosphate accumulates in the presence of millimolar lithium concentrations. This accumulation of myo‐inositol‐1 ‐phosphate can be detected by in vivo 31P NMR spectroscopy. Since myo‐inositol‐1‐phosphate is a breakdown product of phosphatidylinositol, this may provide a means of noninvasively monitoring phosphatidylinositol metabolism in vivo. © 1987 Academic Press, Inc.
Intracellular sodium and lithium NMR relaxation times in the perfused frog heart
Authors: Burstein Deborah , Fossel Eric T.
Published: March 2007

We have used a combination of a shift reagent and mathematical filtering or presaturation of the extracellular sodium resonance for the quantitative investigation of the intracellular sodium and lithium relaxation times in the perfused frog heart. While the T1 of the intracellular sodium was found to consist of a single‐exponential time constant (approximately 23 ms), the T2, was better fit as a double‐exponential decay with time constants of approximately 2 and 17 ms. However, the relative amplitudes of the two time constants in the T2 decay were found to be inconsistent with those which would be expected from a homogeneous pool of nuclei undergoing quadrupolar interactions. The relaxation times were not changed by a fivefold increase in the intracellular sodium level (due to perfusion with a ouabain‐containing buffer). The T1 and T2, of the intracellular lithium (after perfusion with lithium‐containing buffer) were both well fit by single exponentials (700‐ and 31‐ms time constants, respectively). © 1987 Academic Press, Inc.
Further improvement of high‐speed NMR flow‐velocity measurement using a differential phase‐encoding technique
Authors: Kim Y. S. , Mun C. W. , Jung K. J. , Cho Z. H.
Published: March 2007

An NMR imaging technique applicable to high‐velocity flow imaging is described. By subtraction of two phase images obtained by varying the flow‐encoding gradient, it is possible to extract much larger ranges of velocity components. This differential phase‐encoding technique is tested by experiments in a phantom as well as a human volunteer. © 1987 Academic Press, Inc.
31P NMR measurements of intracellular pH in erythrocytes: Direct comparison with measurements using freeze‐thaw and investigation into the influence of ionic strength and Mg2+
Authors: Petersen Aqqaluk , Jacobsen Jens Peter , Hørder Mogens
Published: March 2007

The pH‐dependent chemical shift behavior in 31P NMR spectroscopy of inorganic phosphate (P1) and methylphosphonic acid (MeP) in solutions of various composition at 37°C are presented. An ionic strength dependent lowering of the pKa. values of both P1 and MeP is observed. 3 mmol/liter Mg2+ did not affect the pH‐dependent chemical shift behavior of P1 and MeP in solutions containing 135 mmol/liter KCl and 5 mmol/liter NaCl. This finding: was reinforced by adding 5 mmol/liter 2,3‐diphosphoglycerate (2,3‐DPG) and 1.5 mmol/liter ATP to solutions with 3 mmol/liter Mg2+. The presence of these Mg+‐binding substances had no detectable effect on the chemical shift of P1 and MeP at various pH values The pH dependence of the chemical shift of MeP, P1 and 2,3‐DPG in oxygenated erythrolysates was compared to protein free model solutions. No significant differences could be detected for MeP and P1 whereas there was a change in the chemical shift of about 0.1–0.2 ppm for both phosphates in 2,3‐DPG. Finally intracellular pH estimated by 31P NMR were compared to pH measured by electrode in freeze‐thawed hemolysates. At an extracellular pH of 7.341 ± 0.045 (SD) (n = 6) the intracellular pH was 7.160 ± 0.014 (SD) by the freeze‐thaw procedure and 7.213 ± 0.027 (SD), 7.172 ± 0.029 (SD), and 7.152 ± 0.033 (SD) estimated by the chemical shift of MeP, and 3‐phosphorus and 2‐phosphorus of 2,3‐DPG, respectively. © 1987 Academic Press, Inc.
Three‐dimensional MRI microscopy of the normal rat brain
Authors: Johnson G. Allan , Thompson Morrow B. , Drayer Burton P.
Published: March 2007

Magnetic resonance imaging techniques have been developed to enable imaging of the live rat brain with thin (1.2‐mm) slices and microscopic pixels (115 × 115 μm). Signal‐to‐noise ratios high enough to realize the microscopic resolution are obtained with of coils designed for the subject and through the use of three dimensional Fourier spin warp imaging. The technique yields 16 contiguous slices. Correlation with fixed pathologic specimens enables unequivocal identification of gray and white matter structures in the brain of a live 200‐g rat. Structures clearly visible in the MR images include Ammon's horn, the hypothalamus, corpus callosum and substantia nigra, as well as a number of brainstem nuclei. © 1987 Academic Press, Inc.
Noninvasive evaluation of effects of an aldose reductase inhibitor in rat brain by 19F FDG NMR spectroscopy
Authors: Nakada Tsutomu , Kwee Ingrid L.
Published: March 2007

The inhibitory effects of an aldose reductase inhibitor, sorbinil (Pfizer, NY), on cerebral glucose metabolism were investigated noninvasively in rat brain using 19F nuclear magnetic resonance (NMR) spectroscopy and 2‐fluoro‐2‐deoxy‐D‐glucose (2‐FDG). Sorbinil given orally in the daily recommended doses (25 mg/kg) for man for the treatment of diabetic complications inhibited 2‐FDG flux into the aldose reductase sorbitol (ARS) pathway, demonstrated as a reduction in the intensity of the ARS index resonance as well as an increase in the resonance area ratio between the pentose monophosphate shunt (PMS) and ARS index resonances (PMS/ARS ratio). Spatial metabolite mapping using rotating frame one‐dimensional zeugmatography indicated that the inhibitory effect is spatially nonspecific. The present study is the first direct noninvasive observation of the effects of a pharmacological agent on cerebral enzymatic activities. © 1987 Academic Press, Inc.
The effect of moderate blood alcohol levels on T1 and T2 relaxation times in the brains of normal volunteers
Authors: Logsdail Stephen , Miller David , Macmanus David , Johnson Glyn , Lolin Yvette , O'Gorman Patrick
Published: March 2007

T1 and T2 measurements of the brains of six human volunteers did not change in the presence of moderate blood alcohol levels. © 1987 Academic press, Inc.
The effects of finite sampling in spin‐echo or field‐echo magnetic resonance imaging
Authors: Haacke E. M.
Published: March 2007

The artifacts associated with finite sampling in magnetic resonance imaging are shown to be significant when the ratio of half the sampling time, Ts/2, to transverse relaxation time, T2 is on the order of unity or greater. For both symmetric and asymmetric sampling, these artifacts include enhanced high spatial frequency image intensity (bright edges), induced systematic noise, loss of resolution, and changes in phase. Simple filtering of the raw data does not remove the problem in tissues with positiondependent T2 values. An exact deconvolution method is described to remove these problems associated with finite position‐dependent T2 values. © 1987 Academic Press, Inc.
NMR spectroscopy of heterogeneous solid‐liquid mixtures. Spin grouping and exchange analysis of proton spin relaxation in a tissue
Authors: Sobol W. T. , Pintar M. M.
Published: March 2007

An attempt to resolve the complicated proton NMR signal of a heterogeneous material is presented. Lung tissue is used to illustrate the approach to this problem, which is based on resolving the total proton magnetization into components according to their relaxation times. This procedure is utilized at both low and high magnetic fields. These results are then correlated and analyzed for the effect of exchange between spin groups. For example, the total proton NMR signal of lung tissue is shown to arise from three interacting proton groups: protons on solid macromolecules, bound water protons, and bulk water protons. The dynamics of water is modeled to satisfy the dispersivity and the values of the relaxation parameters obtained considering the effect of exchange. It is proposed that this approach is generally applicable. © 1987 Academic Press, Inc.
A comparison of the chemical analyses of cell lipids with their complete proton NMR spectrum
Authors: Holmes K. T. , Williams P. G. , King N. J. C. , May G. L. , Dyne M. , Bloom M. , Mountford E.
Published: March 2007

Whole cells are made up of molecules in different environments to which NMR spectroscopy is sensitive. In particular, malignant and transformed cells contain lipids not only in bilayers but in isotropically tumbling domains which give rise to high‐resolution spectra. We have recently developed a technique for simultaneously analyzing broadline and high‐resolution signals (M. Bloom, K. T. Holmes, C. E. Mountford, and P. G. Williams, J. Magn. Reson., in press) and we report here its application to a range of rat, mouse, and human cell lines. Some selected features of the NMR spectra were compared with the chemical analysis of the whole‐cell lipid. We found that in general the proportion of protons in the narrow methylene resonance at 1.3 ppm increased with the neutral lipid content of the cells. This peak was chosen because its T2 relaxation behavior correlates with metastatic potential in a rat model system. This new technique could be applied to other high‐resolution components both in healthy and in diseased states. © 1987 Academic Press, Inc.
Proton NMR spectroscopy in myocardial ischemic insult
Authors: Evanochko William T. , Reeves Russell C. , Sakai Ted T. , Canby Robert C. , Pohost Gerald M.
Published: March 2007

Proton NMR methods can monitor mobile lipids (e.g., fatty acids and glycerides) in intact tissue. Lipids play a major role in cardiac energy production, and elevated levels of myocardial lipids have been reported following an ischemic insult. The present study examines the potential of high‐resolution 1H NMR spectroscopy to monitor lipid alterations 24 h following coronary occlusion in dogs, and to correlate these finds with regional myocardial blood flow (RMBF) measured by radiolabeled microspheres. The dogs were killed, and samples of excised myocardium were studied by high‐resolution 1H NMR spectroscopic analysis using solvent suppression in combination with the Hahn spin‐echo pulse sequence. Mobile lipids levels in myocardium with moderate blood flow reduction (28.6 f 7, integral values, arbitrary units; flow 5–50% of control) were significantly elevated compared to the mobile lipid levels in control myocardium (5.3 ± 8, P < 0.001) and in myocardium with severe flow reduction (7.2 ± 10, P < 0.001; flow 5% of control). The mobile lipids in myocardium with severe flow reduction were not elevated significantly relative to control tissue. As anticipated, depression in the level of creatine paralleled the microsphere determined degree of ischemia, i.e., compared to control (9.0 ± 3); creatine levels were moderately decreased with flows 5–50% of control (5.5 ± 4, P < 0.001) and markedly decreased with flows < 5% of control (1.0 ± 2, P < 0.001). This study suggests that high‐resolution 1H NMR spectroscopy may be used to evaluate alterations in myocardial lipid levels following an ischemic insult. This observation, in addition to changes in other selected metabolites, may provide diagnostic and pathophysiologic insight into the severity of the myocardial injury. © 1987 Academic Press, Inc.
A general treatment of NMR imaging with chemical shifts and motion
Authors: Twieg Donald B. , Katz Jose , Peshock Ronald M.
Published: March 2007

A general treatment of nuclear magnetic resonance imaging (MRI) and spectroscopic imaging (MRSI), which takes into account the effects of chemical shift, motion, field inhomogeneity, and relaxation times, is presented. A graphical representation based on the k trajectory formalism which includes these effects is then developed for MRI and MRSI acquisition processes. These considerations should be useful in the study and design of flow‐sensitive MRI and MRSI methods and the accurate prediction of motion artifacts in conventional MRI and MRSI techniques. We conclude by presenting examples illustrating applications of the general theory to specific MRSI and flow imaging methods. © 1987 Academic Press, Inc.
Lipid and water suppression by selective 1H homonuclear polarization transfer
Authors: Hardy Christopher J. , Dumoulin Charles L.
Published: March 2007

A pulse sequence is presented which uses Polarization Transfer by a Selective Homo‐nuclear Technique (POTSHOT) to retain all resonances, in phase, from a selected coupled spin system while suppressing all other peaks, from both coupled and noncoupled spins. This technique, which is a selective form of Homonuclear Polarization Transfer (HPT), has been used in a 1.5‐T whole‐body system to generate edited 1H lactate spectra from lactate/oil phantoms and from excised dog hearts. © 1987 Academic Press, Inc.
Effects of age on apparent 31P spin–lattice relaxation times of rat brain phosphates
Authors: Stolk J. A. , Oolsen J. I. , Alderman D. W. , Schweizer M. P.
Published: March 2007

Apparent 31P spin–lattice relaxation times have been measured in vivo for brain phosphates in young adult, mature adult, and aged rats at 4.7 T and 35°C. Statistically significant differences were found for most phosphate species, except PCr and y‐ATP, among the three age groups, particularly between the young and mature adults. Age‐related changes in tissue composition and exchange reactions are discussed as possible contributors to these results. © 1987 Academic Press, Inc.
Spin echo imaging of multiple chemical shifts
Authors: Lohman J. A. B. , Ordidge R. J. , Connelly A.
Published: March 2007

A method to obtain separate cross‐sectional NMR images of chemically different species on the basis of their difference in chemical shift is presented. The total experiment time is no longer than that required for a conventional image and the method retains the full sensitivity of a spin‐echo 2DFI imaging experiment. Simple addition of the chemical‐shift selective images produces an image free from chemical‐shift artifacts. Results of an in vivo experiment on a human subject are presented. © 1987 Academic press, Inc.
The design of a multiple inversion recovery sequence for T1 measurement
Authors: Young I. R. , Hall A. S. , Bydder G. M.
Published: March 2007

Inversion recovery has the potential to be a powerful method of determining the values of T1 in in vivo studies. However, because of its relative slowness it is not practical to undertake several experiments with different values of the interval between the magnetization inverting 180o pulse and the interrogating 90o one. The multiple inversion recovery method described here uses a series of sampling pulses, most much less than 90o, to produce a series of images. It is shown that slice shape is relatively reproducible from one sample to another and that, largely as a result, the accuracy of the sequence in measuring TI is encouraging. © 1987 Academic Press, Inc.
NMR changes in experimental allergic encephalomyelitis: NMR changes precede clinical and pathological events
Authors: O'brien J. T. , Noseworthy J. H. , Gilbert J. J. , Karlik S. J.
Published: March 2007

In guinea pigs immunized with myelin basic protein (MBP) in complete Freund's adjuvant, experimental allergic encephalomyelitis (EAE) shows a characteristic clinical and pathological course. This study characterized the proton nuclear magnetic resonance (NMR) properties of the central nervous system prior to the onset of clinical signs of EAE. At this time (Days 7–9), the blood brain barrier is disrupted. The effects of the injection of paramagnetic contrast agents gadolinium‐DTPA and gadolinium‐deferoxamine on the tissue NMR relaxation times were examined. Both proton T1 and T2 relaxation times were prolonged in the spinal cord and the brain prior to the onset of clinical and pathological changes. The largest change was in the thoracolumbar spinal cord where T2 prolongation was 22.9%. Gadolinium‐DTPA produced a moderate (5‐11%) or marked (9‐19%) decrease in control and MBP‐treated animals, respectively. Gadolinium‐deferoxamine also decreased proton relaxation times but was toxic to all animals, producing respiratory arrest. Changes in proton T2 relaxation times in cord and cerebellum were sufficiently large (> 10%) to suggest that they might be visualized by magnetic resonance imaging techniques. We have previously described the changes in proton relaxation times during the acute phase of EAE (S. J. Karlik, G. Strejan, J. J. Gilbert, and J. H. Noseworthy, Neurology 36, 1112 (1986)). This study indicates that proton relaxation times are significantly altered at a time when blood brain barrier disruption occurs prior to the onset of clinical or pathological signs. © 1987 Academic Press, Inc.
An optimized head coil design for MR imaging at 0.15 T
Authors: Marrocco Bernard J. D. , Drost Dick J. , Prato Frank S.
Published: March 2007

Receive‐only head coils employing a modified solenoid design were developed for a 0.15‐T imager with horizontal main static and radiofrequency transmit fields. This coil design uses three or five identical horseshoe‐shaped elements, constructed of ½ outside diameter copper tubing, lying one above the other in equally spaced horizontal planes. Coils of this design were compared to the half‐saddle coil supplied with our imager and to the Hammersmith Hospital spherical coil (G. M. Bydder et al., J. Comput. Assist. Tomogr. 9, 987 (1985)). Compared to the half‐saddle coil, one of our new head coils has the same field of view while improving the signal‐to‐noise ratio (S/N) by 80% in the upper brain and 20% in the cervical vertebrae; compared to the spherical coil the S/N was up to 60% lower but the field of view was larger and patient comfort was better. © 1987 Academic Press, Inc.
Slice‐shape artifact changes with precession angle in rapid MR imaging
Authors: Young I. R. , Payne J. A.
Published: March 2007

One possible method of measuring TI in rapidly acquired magnetic resonance images using variants of the FLASH technique is by the manipulation of the magnetization precession angle. It is suggested here that this method is as prone to slice‐shape artifacts as many other approaches. © 1987 Academic Press, Inc.
Modified stimulated echo sequence for elimination of signals from stationary spins in MRI
Authors: Lahrech H. , Briguet A. , Graveron‐Demilly D. , Hiltbrand E. , Moran P. R.
Published: March 2007

Simple modification of the basic stimulated echo sequence (MSTE), including bipolar gradient modulation, permits one to generate relative motion phase modulations between the two STE magnetization components. It is shown how this self‐referencing process can provide flow enhancement without combination of separated images. © 1987 Academic Press, Inc.
Rapid scan magnetic resonance angiography
Authors: Dumoulin C. L. , Souza S. P. , Hart H. R.
Published: March 2007

The change in phase of transverse spin magnetization induced by macroscopic spin motion in the direction of an applied magnetic field gradient is used to generate projection angiograms. The method can provide a quantitative measure of laminar and pulsatile flow. Cardiac synchronization is not required provided that data are acquired at many points in the cardiac cycle. The use of short TR and a large number of excitations provides better suppression of stationary tissue and patient motion artifacts than is possible with cardiac gated studies. In addition to improvements in image quality, a substantial shortening of Scan time is obtained. © 1987 Academic Press, Inc.
Transverse relaxation of saline and plasma using Mn(II), HSA–EDTA–Mn, and HSA–EDTA–Gd: Application to erythrocyte water exchange
Authors: Caines G. Herbert , Morgan Courtney F. , Long Robert C. , Goldstein J. H.
Published: March 2007

Enhancements of 1H nuclear magnetic transverse relaxation rates by Mn(II)‐ and Gd(III)‐ethylenediaminetetraacetic acid (EDTA)‐human serum albumin (HSA) complexes are compared with MnCl2 in human plasma and isotonic saline. HSA–EDTA–Mn and HSA–EDTA–Gd in saline, at physiological concentrations of HSA, afforded T2's comparable to 2 mM MnCl2 in 4% HSA saline. The above reagents are new and potentially useful relaxation agents for the measurement of H2O exchange rates in erythrocyte suspensions. The exchange rate of water across the red cell membrane was determined using these new reagents over the temperature range from 20 to 37°C. © 1987 Academic Press, Inc.
23Na rotating frame imaging in the perfused rabbit heart using separate transmitter and receiver coils
Authors: Moonen C. T. W. , Anderson S. E. , Unger S.
Published: March 2007

One‐dimensional spatial localization of sodium absorption in the perfused rabbit heart was obtained using 23Na rotating frame imaging. A Dadok‐type coil was used as the receiver and a circular surface coil as the transmitter allowing regularly shaped slices and homogeneous reception sensitivity. The short time of spatial labeling in this technique results in minimal intensity losses due to relaxation processes. © 1987 Academic Press, Inc.
Localized imaging using stimulated echoes
Authors: Mills Pamela , Chew Wil , Litt Lawrence , Moseley Michael
Published: March 2007

Stimulated‐echo localized spectroscopy was combined with phase‐ and frequency‐encoding gradients to obtain “zoom” or magnified images of specific organsin situ. The technique requires neither surface coils nor an imaging coil arrangement that exclusively isolates the target organ. This technique can be readily applied to conventional spectrometer imagers that have limited computational capabilities. © 1987 Academic Press, Inc.
31P NMR spectroscopy of the stomach by zig–zag coil
Authors: Nakada Tsutomu , Kwee Ingrid L. , Miyazaki Toshiyuki , Iriguchi Norio , Maki Takeshi
Published: March 2007

Phosphorus‐31 (31P) nuclear magnetic resonance (NMR) spectroscopic investigations of the rat stomach were performed utilizing a 1‐cm2, three‐turn, zig‐zag coil. A zig‐zag coil of this dimension produced an effective Bl field that extends only within a 4‐mm distance from the plane of the surface coil, rendering it possible to obtain high‐resolution 31P spectra localized to the stomach without contamination from surrounding tissues. Normal stomach showed a characteristic spectral pattern with resonances reflecting inorganic phosphate (Pi), phosphocreatine (PCr), and the α‐, β‐, and γ‐phosphates of adenosine triphosphate (ATP). Ischemia‐induced changes in Pi, PCr, and ATP resonances were readily followed in vivo with a time resolution of 2.13 min. Indomethacin‐induced ulcer revealed a low intracellular pH and a decrease in the PCr to Pi ratio indicating the partially ischemic conditions of ulcerative lesions of the stomach as has been previously suggested. The present studies indicate that 31P NMR spectroscopy utilizing a zig‐zag coil is a powerful tool to study local pathology of the gastrointestinal (GI) tract. Since zig‐zag coils suitable for fiberscopic devices are easily constructed, clinical applications of the present technique are apparent. © Academic Press, Inc.
Diabetes insipidus secondary to intracranial sarcoidosis confirmed by low‐field magnetic resonance
Authors: Lewis R. , Wilson J. , Smith F. W.
Published: March 2007

A 32‐year‐old woman who had been diagnosed as having pulmonary sarcoidosis 18 months previously presented with thirst and polyuria. The diagnosis of diabetes insipidus was confirmed biochemically and magnetic resonance imaging (MRI) revealed sarcoid involvement of the pituitary stalk. © Academic Press, Inc.
A transformer‐coupled double‐resonant probe for NMR imaging and spectroscopy
Authors: Fitzsimmons Jeffrey R. , Brooker H. Ralph , Beck Barbara
Published: March 2007

A new type of double‐resonant coil which takes advantage of the properties of a radio‐frequency transformer is described. Two concentric loops are wound in close proximity to yield a high mutual inductance. The primary side is tuned to 34 MHz for 31P and the secondary side is tuned to 85 MHz for protons. A single lead allows program control over frequency without the need to rearrange cabling. Proton and phosphorus spectroscopy are made possible over essentially the same volume of interest without the need for repositioning the sample. © Academic Press, Inc.
0.1‐T human fat/water separation by SIDAC
Authors: Manabe Atsutaka , Miyazaki Toshiyuki , Toyoshima Hideo
Published: March 2007

High‐resolution human fat/water separated images were obtained in 17 min at a static magnetic field strength as low as 0.1 T. The sequence used was based on SIDAC (spectroscopic imaging by dephasing amplitude changing), which employs a stepwise changing dephase gradient for the separation of spectral and spatial information of magnetic spins. © Academic Press, Inc.
Instant images of the body by magnetic resonance
Authors: Richard Ian L. Pykett , Rzedzian R.
Published: March 2007

Proton 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. © Academic Press, Inc.
Low‐power NMR volume selection by slicing z magnetization
Authors: Brereton Ian M. , Brooks William M. , Marshman Margaret F. , Field James , Doddrell David M.
Published: March 2007

A novel method for reducing the rf power requirements of selective pulses employed for z magnetization 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 for in vivo applications. © Academic Press, Inc.
A versatile multinuclear probe designed for in vivo NMR spectroscopy: Applications to subcutaneous human tumors in mice
Authors: Lyon Robbe C. , Tschudin Rolf G. , Daly Peter F. , Cohen Jack S.
Published: March 2007

We describe a versatile NMR probe that is designed for a variety of in vivo spectroscopic studies on small animals in vertical wide‐bore magnets. Replaceable brackets enable the coils to be exchanged readily in order to observe 1H, 13C, 31P, and other nuclei, and to carry out double‐resonance experiments. Two solenoidal coil designs are described and applied to observe 31P, 13C, and 1H natural abundance spectra of subcutaneously implanted human tumors in mice. For 31P and 31C observation with 1H decoupling, a concentric coil arrangement was employed with a broadband inner coil and the outer coil tuned to 1H at 400 MHz. A single coil tuned to 400 MHz was used to observe 1H resonances. A thin copper foil design was found to be superior with respect to S/N and resolution to previously described Faraday shields used to shield the NMR signals originating from nontumor tissues. 31P spectra of in vivo tumor tissue were compared to spectra of in vitro perfused tumor cells of the same origin. Tumor tissue in vivo exhibited much higher levels of inorganic phosphate and phosphocreatine. Signals from [13C2]glucose and its major metabolite, [13C2]lactate, were readily observed and monitored in an unobstructed region of the 13C spectra of tumor tissue in vivo following the injection of [13C2]glucose in adjacent tissues. A 1H spectrum of tumor tissue, characterized by five broad resonances, was observed with excellent water suppression. © 1988 Academic Press, Inc.
Noninvasive measurement of molar concentrations of 31P metabolites in vivo, using surface coil NMR spectroscopy
Authors: Tofts Paul S. , Wray Susan
Published: March 2007

The measurement of absolute concentration of 31P metabolites is described, using water 1H as an internal concentration standard. An analysis of the effect of variations in coil Q on flip angle and sensitivity is presented and verified experimentally. Concentrations of nucleoside triphosphate in rat brain and muscle have been measured. © 1988 Academic Press, Inc.
Magnetic field mapping
Authors: Hornak Joseph P. , Szumowski Jerzy , Bryant Robert G.
Published: March 2007

Homogeneous radiofrequency magnetic fields are necessary for production of high‐quality magnetic images and for most forms of magnetic resonance spectroscopy. It is often convenient to map the radiofrequency homogeneity associated with a resonant device by measuring the magnetic image intensity of an aqueous phantom placed within the resonator. The rf field intensity is not related trivially to the magnetic image intensity, and the relationship is different for different image acquisition methods. In this report relationships between rf field intensity and magnetic image intensity are derived and radio‐frequency field maps presented for comparison using (1) an rf probe moved about within the resonant volume, (2) spin‐echo images, and (3) small tip angle gradient refocused echo images. © 1988 Academic Press, Inc.
Optimization of MR protocols: A statistical decision analysis approach
Authors: McVeigh Elliot R. , Bronskill Michael J. , Henkelman R. Mark
Published: March 2007

A new method of optimizing MRI data acquisition protocols is presented. Tissues are modeled with probability density functions (PDFs) of tissue parameter values (such as T1, T2). The imaging data acquisition process is modeled as a mapping from a tissue parameter space to a signal strength space. Tissue parameter PDFs are mapped to signal strength PDFs for each tissue in a clinical problem. The efficacy of an MRI protocol is evaluated using the methods of statistical decision analysis applied to the signal strength PDFs, including the propagation of noise. This procedure evaluates the ability to discriminate different tissues based on the signal strengths produced with the protocol. The model can incorporate an arbitrary number of tissues, parameters, and pulse sequences in the protocol. The multivariate nature of MRI and the observed broad distribution of tissue parameter values makes this model more appropriate for optimizing data acquisition protocols than methods which maximize the signal‐difference‐to‐noise ratio between discrete values of the tissue parameters. It is shown that these two methods may calculate different optimal protocols. The method can be used to optimize data acquisition for quantitative computer‐based tissue classification, as well as imaging. Data acquisition and image processing philosophies are discussed in light of the method. © 1988 Academic Press, Inc.
Temporal physicochemical changes during in vitro relaxation time measurements: The cerebrospinal fluid
Authors: Grant R. , Condon B. , Moyns S. , Patterson J. , Hadley D. , Teasdale G.
Published: March 2007

Documented relaxation time measurements of body fluids such as cerebrospinal fluid (CSF) vary considerably. This may be largely due to lack of an appropriate method of maintaining the in vivo physiological and biochemical characteristics of the fluid. We have developed an in vitro technique that maintains the in vivo characteristics of body fluid samples for a sufficiently long period to establish the true relaxation times. To illustrate this we studied changes in CSF pH, pO2, and pO2, first as it equilibrated with air and then under anaerobic conditions as found in vivo. Relaxation times of CSF were then studied under aerobic and anaerobic conditions. Under the particular aerobic conditions used the pH and pO2 of CSF increased quickly and pO2 fell within the first 30 min. By 3–4 h equilibration with air was complete. The T1 and T2 relaxation times of CSF decreased by 14 and 16%, respectively, as a result of these physicochemical changes. It is important that such changes be considered when relaxation measurements of any body fluid are performed in vitro and efforts to maintain the in vivo milieu should not be neglected. © 1988 Academic Press, Inc.
Rapid local rectangular views and magnifications: Reduced phase encoding of orthogonally excited spin echoes
Authors: Conturo Thomas E. , Price Ronald R. , Beth Albert H.
Published: March 2007

A method is described for rapid, artifact‐free imaging and magnification of small regions within a larger sample. This combines a rectangular window, reconstructed from a reduced number of phase‐encoding steps, and confinement of spin echoes to a similar rectangular strip by orthogonal π/2 and π excitations. Phase encoding is along the width of the strip (along Y). Off‐center strips are excited by offsetting the Y slice‐selecting gradient, and the reconstruction window is kept coincident with excitation by similarly offsetting the Y phase‐encoding gradient. The excited strip is centered in the reconstruction window by setting the radiofrequency transmitter on resonance. The method is shown to be useful for long narrow structures such as the spine where the acquisition time is reduced by over a factor of 5 determined by the image aspect ratio. © 1988 Academic Press, Inc.
A comparison of one‐shot and recovery methods in T1 imaging
Authors: Crawley Adrian P. , Henkelman R. Mark
Published: March 2007

Spin–lattice (T1) relaxation times are conventionally estimated using inversion recovery or saturation recovery sequences. Such “recovery” methods are limited in magnetic resonance imaging by the long times required to collect multiple points along the T1 relaxation curve. This problem can be overcome by the use of “one‐shot” methods, which collect all points along the relaxation curve in a single excitation. We have compared the relative efficiency of these methods, on the basis of the signal‐to‐noise ratio obtained in the calculated T1 image from an exam time of fixed duration. We have found that a one‐shot method using stimulated echoes has a poor efficiency. However, a method based on a technique first proposed by Look and Locker has an efficiency that is almost equal to the inversion recovery method and therefore possesses highly favorable properties for T1 imaging. © 1988 Academic Press, Inc.
In vivo determination of T1 and T2 in the brain of patients with severe but stable multiple sclerosis
Authors: Larsson H. B. W. , Frederiksen J. , Kjær L. , Henriksen O. , Olesen J.
Published: March 2007

In vivo measurements of relaxation processes in multiple sclerosis (MS) lesions by magnetic resonance imaging (MRI) may be important for evaluation of the disease activity in individual MS plaques. To obtain information of presumably chronic plaques, 10 patients with severe, but stable MS were investigated, using a whole‐body superconductive MR scanner, operating at 1.5 T. By employing 12‐point (or 6‐point) partial saturation inversion recovery (PSIR) and 32‐echo multiple spin‐echo sequences we measured T1 and T2 in MS plaques, white matter, and cortical gray matter. We also focused on the issue, whether T1 and T2 relaxation processes in fact were monoexponential. T1 and T2 in plaques were found to cover a wide range, which could be explained only by inherent biophysical dis similarity of the plaques, possibly due to differences in disease activity, edema and gliosis. T1 appeared monoexponential in all the plaques, but in seven cases T2 showed biexponential behavior. This was found to be most pronounced near the cerebrospinal fluid of the ventricles, probably caused by partial volume effects or increased free water content. The T2 of apparently normal white matter was significantly longer in MS patients than in healthy subjects. © 1988 Academic Press, Inc.
Nonedited 1H NMR lactate/n‐acetyl aspartate ratios and the in vivo determination of lactate concentration in brain
Authors: Vink Robert , McIntosh Tracy K. , Faden Alan I.
Published: March 2007

The 1H lactate/n‐acetyl aspartate ratio is commonly used for the quantitation of brain lactate under pathological conditions. We demonstrate that the intensity of the lactate methyl region in water‐suppressed, nonedited 1H spectra increases following mild brain trauma as a result of factors other than lactate accumulation. © 1988 Academic Press, Inc.
Efficient algorithms for generating interpolated (zoomed) MR images
Authors: Smith M. R. , Nichols S. T.
Published: March 2007

This paper discusses the two‐dimensional implementation of a number of modified fast Fourier transform (FFT) algorithms that efficiently interpolate (zoom) magnetic resonance (MR) images. If the original image was sampled at a rate satisfying the Nyquist criterion, these algorithms would effectively increase the sampling rate, permitting image details to be more easily discerned. The Skinner interpolating fast Fourier transform (SIFIT) avoids many of the computationally unnecessary complex multiplications that occur when interpolating using the normal fast Fourier transform algorithm. The novel interpolating fast Fourier transform (NIFFT) offers further savings when a subimage is required. Theoretical and experimental timings that compare the use of the normal FFT, SIFFT, and NIFFT algorithms for interpolation are given using magnetic resonance image reconstruction examples. Time savings of a factor of 2 to 4 are possible in typical experimental situations. Time savings of factors of 5 to 20 are possible when zooming images using two‐dimensional band selectable digital filtering (2D‐BSDF) in combination with decimation and the SIFFT algorithm. In 2D‐BSDF, the original MRI data set is reduced in size to retain only those frequency components corresponding to a desired subimage, thereby decreasing the computational load associated with further processing. A significant reduction in computation time is achieved when modeling is combined with 2D‐BSDF and SIFFT as fewer points require modeling. © 1988 Academic Press, Inc.
Characterization of high‐energy phosphate compounds during reperfusion of the irreversibly injured myocardium using 31P MRS
Authors: Wendland Michael F. , White Richard D. , Derugin Nikita , Finkbeiner Walter E. , McNamara Michael T. , Moseley Michael E. , Lipton Martin J. , Higgins Charles B.
Published: March 2007

Phosphorus‐31 magnetic resonance spectroscopy (MRS) was used to monitor regional changes in high‐energy phosphorus compounds and intracellular pH during 60 min of acute regional ischemia (acute occlusion of left anterior descending artery) and reperfusion in open‐chest cats using a 1.2‐cm two‐turn coil sutured to the myocardium. During the 60‐min ischemic phase, phosphocreatine (PCr) intensity was reduced to 47 ± 4.9% (mean ± SE) of control (p < 0.01) by 15 min postocclusion while adenosine triphosphate (ATP) intensity decreased more slowly with the decrease (66 ± 5.6%) achieving significance (p < 0.05) only at 60 min postocclusion. Inorganic phosphate (Pi) increased to a maximum of 397 ± 42% of control (p < 0.01) while the pH decreased progressively from 7.36 ± 0.02 to 6.02 ± 0.14 (p < 0.01). After release of occlusion PCr intensity recovered to 86 ± 12% of the initial control value at 15 min postreperfusion but showed a subsequent downward trend to 79 ± 8.8%. The ATP did not recover but tended to decline further during reperfusion. The Pi intensity decreased to 260 ± 38% of control while the pH increased to 7.01 ± 0.23 by 15 min postreperfusion. Thus, the reperfused irreversibly injured myocardium is characterized by persistent depletion of PCr and ATP and elevation of Pi. Phosphorus‐31 MRS provides a nondestructive method for characterizing the reperfused irreversibly damaged myocardium. © 1988 Academic Press, Inc.
Adaptation of culture methods for NMR studies of anchorage‐dependent cells
Authors: Neeman M. , Rushkin E. , Kadouri A. , Degani H.
Published: March 2007

Two methods for growing anchorage‐dependent cells were adapted for nuclear magnetic resonance (NMR) measurements: growing cells on agarose polyacrolein microsphere beads and on “filters” made of nonwoven polyester fabric. Both were found to be convenient and most suitable for NMR studies in any conventional spectrometer without probe modification. These methods were employed in studies of human breast cancer T47D‐A11 cells, using scanning electron microscopy and 31P NMR spectroscopy. The results show that the contents per cell of phosphorylcholine, phosphorylethanolamine, and their glycerol derivatives depend on the mode of cell assembly and decrease gradually with the increase in cell‐cell interaction along the growth curve. © 1988 Academic Press, Inc.
Sodium influxes in renal epithelial LLC‐PK1/CI4 cells monitored by 23Na NMR
Authors: Jans A. W. H. , Willem R. , Kellenbach E. R. , Kinne R. K. H.
Published: March 2007

23Na NMR experiments with a suspension of the renal epithelial cell line, LLC‐PK1/ CI4 in the presence of the shift reagent dysprosium polyphosphate showed that the intra‐cellular sodium was only NMR visible for 64 ± 4%. Intracellular sodium content was found to be 30.6 ± 1.2 mM (25oC). Examination of the sodium influx during recovery from intracellular acidification showed that sodium is transported not only by Na+/H+ exchange but also by sodium‐D‐glucose cotransport with a stoichiometry of 1:1. © 1988 Academic Press, Inc.
MRI of extremities using perforated single‐turn solenoids
Authors: Hornak Joseph P. , Marshall Eric , Szumowski Jerzy , Bryant Robert G.
Published: March 2007

A class of single‐turn solenoids that permits magnetic imaging of the extremities in horizontal bore magnets with improved coupling between the imaged anatomy and the rf section of the imager is described and demonstrated. These devices differ from more conventional designs primarily by the placement of one or more access holes in the side of the generally cylindrical resonant structure to permit extremity insertion. The image quality is excellent, rf efficiency and homogeneity are good, and signal‐to‐noise is high, permitting rapid acquisition of magnetic images with small fields of view. © 1988 Academic Press, Inc.