bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐order coils as transmitters for NMR imaging
Authors: Sotgiu Antonello , Hyde James S.
Published: March 2007

High‐order radiofrequency transmitter coils are described that permit, in the context of NMR imaging, a knowledgeable trade‐off between coil complexity and the degree of inhomogeneity over a specified volume of space. A mathematical formulation of high‐order coils is developed for an axially symmetric polarizing de field and transverse rf field. The field is created by a number of longitudinal current filaments with equal angular separations on the wall of a cylinder. In its most general form, each current can be independently specified. Circularly or linearly polarized fields can be created. Quadrature and saddleshaped coils emerge as special cases of the general formulation. The development has been tested experimentally and good agreement found. High‐order coils can also be used as receivers, permitting more equal weighting of the sensitivities of each pixel. © 1986 Academic Press, Inc.
Transmission line matching of surface coils
Authors: Martin Joel F. , Daly Charles P.
Published: March 2007

Tuning of surface coils is often difficult to accomplish in vivo since the exact coil loading is impossible to prediet in advance. This technical difficulty was obviated through use of a transmission line matching scheme. This technique has been successfully used at a variety of frequencies for imaging and spectroscopy. © 1986 Academic Press, Inc.
In vivo31P NMR studies of avian dystrophic muscles
Authors: Narayana P. A. , Delayre J. L. , Misra L. K.
Published: March 2007

In vivo 31P NMR studies of normal and dystrophic pectoralis muscles of chicks were carried out in the age group of 2 to 8 weeks. It was observed that the ratios [PCr]/[Pi] and [PCr]/[ATP] were essentially the same in both normal and dystrophic muscles. The cellular pH for normal muscles however, was found to be higher (7.24 ± 0.08) compared to the dystrophic muscles (7.0 ± 0.07). © 1986 Academic Press, Inc.
Relaxometry of ferritin solutions and the influence of the Fe3+ core ions
Authors: Koenig Seymour H. , Brown Rodney D. , Gibson John F. , Ward Roberta J. , Peters Timothy J.
Published: March 2007

The magnetic field dependence of 1/T1 over the range 0.01 to 50 MHz proton Larmor frequency (NMRD profile) is reported for water protons in solutions of horse spleen apoferritin, and of ferritin reconstituted at both low and high iron levels. The apoferritin results are in every way typical of diamagnetic spherical proteins of their size (K. Hallenga and S. H. Koenig, Biochemistry 15, 4255 (1976)). Titration of up to 24 ferrous ions per protein molecule, with subsequent oxidation to ferric, shows a nonlinear saturating contribution to the NMRD profile which is interpreted as arising from a small number of ferric ions (six to eight) bound close to the outside of each ferritin molecule, and a comparable number of interior sites. The latter become multiply occupied as the core grows and do not contribute measurably to 1/T1 in this state. The former sites are never more than singly occupied, and their contribution to the solvent proton relaxation rates is independent of the loading of the core. Measurements of 1/T2 at 20 MHz are quite in accord with theoretical expectations for apoferritin and ferritin with up to 24 ferric ions per molecule. However, a marked increase in 1/T2 is observed at higher iron loadings that we are unable to account for within the framework of the theory of outer sphere relaxation, even when the effects arising from inhomogeneities in the local magnetic field are included. A sample of human spleen hemosiderin was found to have the same 1/T1 NMRD profile as a comparable sample of ferritin. © 1986 Academic Press, Inc.
Fat and water separation at 0.23 T using simultaneous shift selective imaging
Authors: Hennig J. , Friedburg H.
Published: March 2007

Based on the principle of selective inversion of the fat or water signal we have developed a method which allows the simultaneous acquisition of separated fat and water images. In combination with multiecho techniques, this allows the determination of shift selective relaxation times. A detailed analysis of the relaxation behavior of a human leg at 0.23 T shows that T2 of fat and water can differ by a factor of two or more. We think, that the potential of MRI for differential diagnosis can be greatly enhanced using our method. © 1986 Academic Press, Inc.
In vivo determination of body iron stores by natural‐abundance deuterium magnetic resonance spectroscopy
Authors: Irving Michael G. , Brereton Ian M. , Field James , Doddrell David M.
Published: March 2007

Induction of iron overload in mice using 1% (w/w) dietary carbonyl iron resulted in marked decreases in 2H and 31P NMR relaxation times. Natural‐abundance deuterium (2H) NMR spectroscopy has been used to measure 2H T1 values in vivo in the presence of body paramagnetic iron. This procedure offers a method for noninvasive determination of body iron stores. © 1987 Academic Press, Inc.
Pseudo‐gating: Elimination of periodic motion artifacts in magnetic resonance imaging without gating
Authors: Haacke E. Mark , Lenz Gerald W. , Nelson A. Dennis
Published: March 2007

This note explains and illustrates a technique of reducing artifacts produced by periodic motion without using physiologic gating. The method is simple and can be applied on any standard MRI unit. For periodic motion, effective gating can be attained by setting the product of the number of acquisitions (at each phase‐encoding step), N, times the repeat time, TR, equal to the period of the motion, T. This pseudo‐gating can be used with any TR but, if changes in the period occur, is most robust with short TR values. The method is also applicable to multislice and volume imaging. For fast field echo methods, the above rule can be used if the period of the motion is smaller than the total scan time. Otherwise, the scan need only be repeated N times to avoid artifacts and improve signal‐to‐noise. The method has been implemented to remove both respiratory and/or cardiac motion artifacts. © 1987 Academic Press, Inc.
Oxygen‐17 compounds as potential NMR T2 contrast agents: Enrichment effects of H217O on protein solutions and living tissues
Authors: Hopkins A. L. , Barr R. G.
Published: March 2007

The isotopic enrichment of solutions, living tissues, and organisms with oxygen‐17 in the form of H217O shortens their proton NMR transverse relaxation times (T2) and produces changes in NMR image intensity. The transverse relaxation rate (1/T2) was found to be linearly dependent on the H217O concentration in biological solutions up to 5% enrichment. The longitudinal relaxation time (T1) is not affected by enrichment. Equal concentrations of H217O do not produce the same magnitude of T1 change in all physiological environments. The reasons for these differences are discussed. The results suggest that certain oxygen‐17 compounds should be explored as “contrast agents” in magnetic resonance imaging. © 1987 Academic Press, Inc.
The effects of a static magnetic field on DNA synthesis and survival of mammalian cells irradiated with fast neutrons
Authors: Ngo Frank Q. H. , Blue James W. , Roberts William K.
Published: March 2007

The effects of a static magnetic field (0.75 T) on DNA synthesis and survival were examined with Chinese hamster V79 cells in cultures with and without fast‐neutron irradiation. We found that the magnetic field applied alone for up to several hours did not cause a significant effect in either the rate of DNA synthesis or cell viability; the latter was assayed by colony formation. When cells were exposed simultaneously to the magnetic field and fast neutrons, the effects resembled those observed with neutrons alone. This was the case for both inhibition of DNA synthesis and cell killing. Cells irradiated first with neutrons followed immediately by 1 h of magnetic field exposure showed a dose‐survival response curve indistinguishable from that of neutrons alone. These data suggest that the biological effect due to the magnetic field is negligible and that the presence of the magnetic field either during or subsequent to fast‐neutron irradiation does not affect the neutron‐induced radiation damage or its repair. © 1987 Academic Press, Inc.
Natural abundance 13C NMR spectrum of glycogen in humans
Authors: Jue T. , Lohman J. A. B. , Ordidge R. J. , Shulman R. G.
Published: March 2007

In vivo NMR has focused on using 31P and 1H to study metabolism in humans. Comparable 31C NMR studies have not been undertaken, presumably, because of its insensitivity. We report herein that the natural abundance 13C signal from C1 glycogen is observable. The ability to observe the signal opens new opportunities to noninvasively study glycogen metabolism in man. © 1987 Academic Press, Inc.
NMR relaxation times T1 and T2 of water in plasma from patients with lung carcinoma: Correlation of T2 with blood sedimentation rate
Authors: Schuhmacher Jochen H. , Clorius John H. , Semmler Wolfhard , Hauser Harald , Matys Edmund R. , Maier‐Borst Wolfgang , Hull William E.
Published: March 2007

The T1 and T2 NMR 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 plasma T2 was 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 of T2 in plasma is a secondary host response. However, a plot of plasma 1/T2 versus 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/T2 with BSR, found solely in the tumor patient group, increased the diagnostic sensitivity of T2 measurements and may help to differentiate between malignant and nonmalignant disease. No significant variation in the T1 spin‐lattice relaxation time was observed. © Academic Press, Inc.
Some observations of the design of rf coils for human internal use
Authors: Harman R. R. , Butson P. C. , Hall A. S. , Young I. R. , Bydder G. M.
Published: March 2007

Some features of the design and implementation of NMR probes for insertion into peripheral orifices of the body are described. In particular, the possibilities of using parasitic coils without direct connections in conjunction with conventional whole body coils are examined. The use of windings around the NMR probe carrying gradient pulses as a means of eliminating the very high signals from tissue immediately adjacent to the coil windings is also evaluated. These approaches are, in practice, difficult to combine, and hence need to be viewed almost as alternative possibilities. Practical results of experimental investigations are presented using both phantoms and volunteers. © 1988 Academic Press, Inc.
Fast MRI data acquisition using multiple detectors
Authors: Hutchinson Michael , Raff Ulrich
Published: March 2007

We present a novel imaging procedure using multiple receiver coils. This circumvents the sequential acquisition of signals required by conventional imaging strategies. The advantage of this technique over existing subsecond imaging techniques is that (a) contrast can be maintained and (b) there is no magnetic field gradient switching involved. © 1988 Academic Press, Inc.
The noninvasive determination of linoleic acid content of human adipose tissue by natural abundance carbon‐13 nuclear magnetic resonance
Authors: Moonen Chrit T. W. , Dimand Robert J. , Cox Kenneth L.
Published: March 2007

A new method to assess noninvasively the proportionate storage of poly‐ and mono‐unsaturated fatty acids in human adipose tissue is described. The method is based on in vivo natural abundance 13C NMR at 1.9 T using a TMR 32/200. Data were acquired with a concentric coil system placed below subcutaneous adipose tissue of the calf or the lower arm. Continuous single‐frequency decoupling was used to optimize the signal in the spectral region of interest and minimize potential heating effects. Only adipose triglycerides contributed significantly to the resonance intensities. Typical linewidths for the in vivo13C resonances were 10‐14 Hz resulting in excellent resolution in the region of the unsaturated carbons. Signal‐to‐noise ratios for the resonance at 128.4 ppm (due to carbon atoms of polyunsaturated fatty acids) were typically 50‐90 in 8 min using 0.25s repetition time. The relative storage of polyunsaturated fatty acids was determined by comparing the peak intensity at 128.4 ppm with the intensities of the peaks due to the carbonyl, the glycerol, or the main methyl carbons. High‐resolution in vitro NMR of adipose biopsies and various mixtures of triglycerides studied with the in vivo NMR protocols provided further evidence that the described in vivo NMR methods allowed precise information on the relative storage of linoleic acid, the main constituent of the pool of polyunsaturated fatty acids. Conventional gas chromatography was performed on adipose biopsies of two volunteers and resulted in close agreement with the in vivo NMR methods. The average polyunsaturated fatty acid concentration in adipose tissue in seven healthy volunteers was 19.83 mol% ± 1.74 (SD) as determined by in vivo NMR, consistent with conventional studies based on gas chromatography of biopsied material. Preliminary data on three cystic fibrosis patients showed a decreased polyunsaturated fatty acid concentration of 13.12 mol% ± 2.73 (SD). The high accuracy of this method and its noninvasive character should be especially valuable in clinical research and diagnosis as repetitive adipose biopsies can be avoided. © 1988 Academic Press, Inc.
Dynamic range compression in MRI by means of a nonlinear gradient pulse
Authors: Wedeen Van J. , Chao Yong‐Sheng , Ackerman Jerome L.
Published: March 2007

In current magnetic resonance imaging (MRI), valuable information must often be discarded because the NMR signal has greater dynamic range than the analog‐to‐digital converter (ADC) hardware. Typically, a small set of high‐intensity data points near the center of the spin echo is responsible for most of the MRI data dynamic range. We predict that it is possible to reduce the dynamic range of the MRI spin echo by incorporating an identical nonlinear gradient pulse into each repetition of the imaging pulse sequence, prior to data sampling. This pulse converts the phase distribution of the subject, ordinarily a linear function of image coordinates, into a nonlinear function. A nonlinear phase distribution can have a negligible impact on image magnitude and yet a profound impact on spin‐echo magnitude. Given a nonlinear phase distribution, there will no longer be a single data point at which all of the protons have an identical phase (the echo center). Instead, the protons become phase coherent on a piecemeal basis, the echo peak is smoothed out, and its maximum amplitude and dynamic range are greatly diminished. Using gradient pulses of quadratic spatial variation, we estimate that maximum echo amplitude and dynamic range can be reduced in most cases by an order of magnitude. © 1988 Academic Press, Inc.
Localized double‐quantum filter and correlation spectroscopy experiments
Authors: McKinnon G. C. , Bosiger P.
Published: March 2007

Problems with in vivo proton spectroscopy include strong water and lipid signals, and the very complicated structures of the spectra. Multiple‐quantum experiments can be designed to overcome these difficulties. Using a volume selective refocusing technique, one can demonstrate how multiple‐quantum experiments can be performed in a spatially localized manner. Rather than trying to integrate a localization procedure into a particular spectroscopy experiment itself, the approach here is to leave the basic experiment intact and to add a volume selective “block” to the end of the sequence. This “block” must, of course, preserve the integrity of the particular experiment. The volume selective refocusing method, presented here, does just this for a wide variety of proton NMR experiments. The advantage of this approach is that the analysis of the particular experiment is not changed. This is very important considering the complexity involved. Using this procedure, two very elementary multiple‐quantum experiments have been performed on a 1.5‐T whole‐body scanner. These experiments are a localized double‐quantum filter experiment (for water suppression) and a localized two‐dimensional correlation spectroscopy experiment. © 1988 Academic Press, Inc.
Magnetic resonance imaging of rabbit brain after intracarotid injection of large multivesicular liposomes containing paramagnetic metals and DTPA
Authors: Turski Patrick , Kalinke Tom , Strother Lars , Perman William , Scott Grayson , Kornguth Steven
Published: March 2007

A procedure has been developed for the preparation of large (10‐ to 80‐μm‐diameter) multivesicular liposomes that contain magnetic resonance contrast agent (DTPA and either manganese or gadolinium). Blue dextran was observed to induce the formation of the large liposomes with dioleoylphosphatidylcholine and cholesterol (1:1 molar ratio) and with dipalmitoylphosphatidylcholine and cholesterol (1:1 molar ratio). The formation of the large liposomes is dependent upon mixing the blue dextran with the lipid films at temperatures above the transition point of the lipids. Tracer amounts of 153Gd were added to the aqueous phase to permit quantitation of the recovery of encapsulated materials. Liposomes that were prepared using equimolar ratios of phospholipid and cholesterol were stable in serum for more than 12 h. The ultrastructure of the large multivesicular liposomes reveals the existence of individual vesicles (12 μm diameter) bound together by a multi‐lamellar coating. When injected into the internal carotid artery of the rabbit, the large liposomes became entrapped in the vascular bed primarily in the frontal and occipital regions of brain. The resulting emboli may provide a means to deliver drugs to a specific site in brain, such as a tumor, if the vascular bed of the site can be cannulated precisely. © 1988 Academic Press, Inc.
Simultaneous monitoring of coronary blood flow and 31P NMR detected myocardial metabolites
Authors: Portman Michael A. , James Susan , Heineman F. W. , Balaban Robert S.
Published: March 2007

We report a method of dynamically measuring coronary blood flow in lambs, while simultaneously monitoring cardiac phosphate metabolism with 31P NMR at 81 MHz. This method uses an ultrasonic transit time probe in conjunction with a 4.7‐T CSI spectrometer with a 33‐cm magnet bore. © 1988 Academic Press, Inc.
Fast gradient‐echo chemical‐shift imaging
Authors: Park H. W. , Kim Y. H. , Cho Z. H.
Published: March 2007

A fast chemical‐shift imaging using the gradient‐echo technique is proposed for the separation of the water and fat in human in vivo imaging. This technique also incorporates magnetic field inhomogeneity correction in the fast chemical‐shift imaging. Experimental results of the proposed imaging technique demonstrate that the method would be useful for quick in vivo water‐fat separation imaging with a substantially shorter time than the conventional spin‐echo imaging sequence. © 1988 Academic Press, Inc.
Fast SSFP gradient echo sequence for simultaneous acquisitions of FID and echo signals
Authors: Lee S. Y. , Cho Z. H.
Published: March 2007

Recently, the gradient echo imaging sequence in conjunction with small flip angle excitations and short repetition times has been widely used for fast NMR imaging. As the repetition time decreases to an extent comparable to the spin‐spin relaxation time T2, the residual phase coherency of the transverse spin magnetization tends to form another nuclear signal which is heavily weighted by T2 and similar to a long TR/long TE spin‐echo signal. This effect, although expected, has not been utilized in the conventional fast gradient echo imaging. When this residual phase coherency is utilized in conjunction with the fast SSFT (steady‐state free precession) technique, both the FID and the echo signals can be obtained. In this paper, we have proposed a new technique by which simultaneous acquisitions of both the H D and the echo signals are possible. Experiments on this fast SSFP mode imaging have shown that the FTD signal is TI‐weighted while the echo signal is strongly T2‐weighted. The flip angle optimal for maximizing signal and related contrast are also studied in conjunction with the proposed sequence and the experimental results are presented. © 1988 Academic Press, Inc.
Delivery of nitroxide spin label to cultured cells by liposomes
Authors: Chan H. C. , Magin R. L. , Swartz H. M.
Published: March 2007

The positively charged nitroxide spin label, 2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl‐4‐ trimethylammonium (Cat1), was encapsulated in two types of liposomes, phosphatidylserine/phosphatidylcholine (PS/PC) and phosphatidylserine/distearoylphosphatidylcholine/dipalmitoylphosphatidylcholine (PS/DSPC/DPPC). The liposomes were incubated with mouse thymus‐bone marrow (TB) cells to study the uptake and metabolism of nitroxides entrapped in Iiposomes. The effects of temperature, metabolic inhibitors, and fixation of cells were investigated. The results indicate that different mechanisms are involved in the uptake of these two types of liposomes. PS/PC liposomes interact predominately with the plasma membrane of TB cells and release Cat1 continuously, whereas the majority of PS/DSPC/DPPC liposomes are taken into the cells intact via endocytosis. These findings suggest that it may be possible to deliver nitroxides selectively, either to the membrane of cells or to their interior by manipulating the lipid com‐ position of the liposomes. This study also found that the rate of reduction of Cat 1 delivered using liposomes was increased under hypoxic conditions. Thus, the use of liposomes for in vivo delivery of nitroxides has the potential to provide NMR contrast that reflects different metabolic conditions. © 1988 Academic Press, Inc.
A general approach to selection of multiple cubic volume elements using the ISIS technique
Authors: Ordidge R. J. , Bowley R. M. , McHale G.
Published: March 2007

The ISIS method is used regularly for the selection of a single cubic volume of tissue for in vivo investigation by high‐resolution NMR spectroscopy. This technique has been extended on a theoretical basis to include the simultaneous selection of a number of cubes, the signals from which can be either assessed individually or in certain circumstances coadded to produce improvement in signal‐to‐noise ratio. The modification requires additional selective RF pulses in the spatial encoding prepulse period, and spatially localized spectra are produced by addition and subtraction of NMR signals in a manner similar to the original ISIS technique. © 1988 Academic Press, Inc.
Acute and repair stage characteristics of magnetic resonance relaxation times in oxygen‐induced pulmonary edema
Authors: Shioya Sumie , Haida Munetaka , Tsuji Chizuko , Ohta Yasuyo , Yamabayashi Hajime , Fukuzaki Minoru , Kimula Yuji
Published: March 2007

Proton magnetic relaxation times, T1, and T2, were determined for rat lungs exposed to 80% oxygen for a duration of 2 weeks. The transverse magnetization decay curve of the lung tissue was multiexponential. A linear combination of two decay curves with different T2 values fits the multiexponential decay suggesting that there are at least two different components of tissue water in the lung. Remarkable prolongation of T1 and T2 was demonstrated as lung injuries progressed in the acute stage of pulmonary edema. Both 1/T1, and 1/T2 were significantly correlated with 1/water content of the lung tissue. In the repair stage, T1, and T2 were significantly shortened. Shortening coincided with the spontaneous resolution of pulmonary edema. Relaxation rates showed no significant correlation with 1/water content in this stage. These results indicate that the physical state ofwater in the tissue is affected not only by the water content but also by the derange‐ ment of macromolecules in pulmonary edema. T2, was more sensitive than T1 for detecting pulmonary damage. © 1988 Academic Press, Inc.
Spectroscopic imaging and spatial localization using adiabatic pulses and applications to detect transmural metabolite distribution in the canine heart
Authors: Robitaille Pierre‐Marie , Merkle Hellmut , Hendrich Kristy , Sublett Eugene , Lew Brian , Path Gregory , From Arthur H. L. , Bache Robert J. , Garwood Michael , Uǧubil Kâmil
Published: March 2007

Adiabatic pulses have been employed in spectroscopic imaging and relaxation rate measurements at 4.7 T to demonstrate the feasibility of obtaining spectroscopic data from the complete sensitive volume of a surface coil using the surface coil as a transmitter and receiver. With conventional B1 sensitive pulses, spectroscopic localization or imaging techniques, such as chemical‐shift imaging, yield resonance intensities that are distorted severely as a function of space, and maximal signal is detected from a small region within the complete sensitive volume of the coil. With adiabatic pulses, however, this problem is eliminated completely. In addition, a new method of spatial localization is introduced. This method, referred to as FLAX‐ISIS, is a derivative of longitudinally modulated Fourier series window and ISIS approaches and utilizes adiabatic inversion and excitation pulses. The method allows construction of localized spectra for multiple regions along the surface coil axis by postacquisition data manipulation of a single set of free induction decays. These techniques were applied to the study of the myocardium using an implanted surface coil in an instrumented closed‐chest canine model and in an open‐chest preparation. The results demonstrate that one‐dimensional techniques are adequate for transmural detection of metabolites provided signal origin is restricted to a column perpendicular to the left ventricle wall. © 1989 Academic Press, Inc.
Transmural metabolite distribution in regional myocardial ischemia as studied with 31p NMR
Authors: Robitaille Pierre‐Marie , Lew Brian , Merkle Hellmut , Sublett Eugene , Lindstrom Paul , From Arthur H. L. , Garwood Michael , Bache Robert J. , Uǧubil Kâmil
Published: March 2007

Phosphorus‐31 nuclear magnetic resonance (31P NMR) has been applied to study the canine heart prior to and during regional myocardial ischemia induced by partial flow reduction in the left anterior descending coronary artery (LAD). NMR data were acquired in a transmural fashion by restricting the signal to a column perpendicular to the heart wall using B0 gradients and obtaining spectroscopic spatial resolution along the third dimension using the B1 gradient and adiabatic excitation. With this approach, transmural spectra were accumulated in five separate voxels spanning the wall of the left ventricle from the epicardium to the endocardium. In the normal canine myocardium the levels of high‐energy phosphates CP and ATP were relatively constant throughout the left ventricular wall, with only minor evidence of free inorganic phosphate in any of the transmural voxels. However, during sustained partial occlusion of the LAD, significant regional differences between the epi‐ and the endocardium were noted. The data demonstrate the importance of studying cardiac bioenergetics with transmural differentiation. © 1989 Academic Press, Inc.
Quantitative and qualitative fat analysis in human leg muscle of neuromuscular diseases by 1H MR spectroscopy in vivo
Authors: Bárány M. , Venkatasubramanian P. N. , Mok E. , Siegel I. M. , Abraham E. , Wycliffe N. D. , Mafee M. F.
Published: March 2007

1H MR spectra were recorded from human gastrocnemius muscle at 63.86 MHz using the body coil of the Signa scanner as transmitter and a 3‐in. surface coil as receiver. The fat content of the muscle was quantified relative to that of water in a selected volume or slice. The fat/water ratio was 0.05−0.07 for normal muscle but increased to 0.5−6.0 in primary and secondary muscular disorders such as Duchenne and myotonic dystrophy, Charcot‐Marie‐Tooth and polio muscular atrophy, cerebral palsy, and spina bifida. In Werdnig‐Hoffmann spinal atrophy the ratio was above 10. Water‐suppressed and sliceselective 1H spectroscopy was used for qualitative analysis of fat. The 1H profile of gastrocnemius muscles between healthy individuals and patients with neuromuscular diseases showed two major differences. In the normal muscle spectra, the resonance from the –(CH2)n– protons at 1.6 ppm was the most pronounced, whereas in the diseased muscle spectra resonances also appeared between 1.1 and 1.4 ppm. Some diseased muscle spectra showed multiple resonances from CHCH– in polyunsaturated fatty acids between 5.5 and 7.0 ppm. The corresponding resonances from CH‐CH2–, 1.9−2.0 ppm, and CH‐CH2‐CH, 2.7−2.9 ppm, were also seen. These peaks are usually not detected in normal muscle. © 1989 Academic Press, Inc.
Relaxometry of lens homogenates. II. temperature dependence and comparison with other proteins
Authors: Beaulieu Christopher F. , Brown Rodney D. , Clark John I. , Spiller Marga , Koenig Seymour H.
Published: March 2007

We have extended our earlier work (C. F. Beaulieu, J. I. Clark, R. D. Brown III, M. Spiller, and S. H. Koenig, Magn. Reson. Med. 8, 45 (1988)) on the magnetic field dependence of 1/T1 (NMRD profiles) of calf lens nuclear homogenates, at 25°C, to 5°C, and to other protein systems as well. These include concentrated solutions of myoglobin and bovine serum albumin, both globular proteins, the first compact and roughly spherical, the other extended, flexible, and with weak internal bonding; chicken lens homogenate, for which the dominant crystallins (lens proteins) are ∼ 70% α‐helical compared with calf crystallins, which are essentially all β‐sheet; and hen egg white, both native and heat‐ denatured. Our earlier conjectures regarding a reversible change in protein organization of the calf lens crystallins as a function of solute protein concentration is given added support. Our findings suggest that cytoplasmic homogenate can be characterized as a heterogeneous and polymorphic solution of crystallins. At high concentrations the NH moieties of the protein backbone become accessible to solvent with water (not NH proton) exchange rates > 104s−1. This conclusion is based on two aspects of the observed NMRD profiles. At low crystallin concentration, the profiles of calf and chicken lens homogenates are similar in form to those of myoglobin and native hen egg white, a form that has been studied previously for a range of diamagnetic globular proteins and has been demonstrated to arise from the rotational thermal motion of the solute molecules. At high crystallin concentrations, the NMRD profiles of the lens homogenates develop a monotonic background (high rates at low fields), much like that of the heat‐denatured egg‐white sample and those of most tissues. In addition, there is a set of peaks in the central part of the profiles of the concentrated crystallins, seen also in the denatured egg white and some tissues but not in the myoglobin sample, which is known to arise from cross‐relaxation interactions between the water protons and (through the intermediary of the NH proton) the 14N quadrupolar levels. The magnitude of these peaks, which is larger by an order of magnitude for native calf lens homogenates than for any tissue, requires that the majority of the NH moieties be accessible to water. Finally, going to 5°C for the native calf lens homogenate takes the sample below the temperature of reversible phase separation, and it becomes opaque. However, there is no change in the profile that can be attributed to this transition and its associated opacity. © 1989 Academic Press, Inc.
Magnetic shielding of magnetic resonance systems
Authors: Andrew E. R. , Szczesniak E.
Published: March 2007

Basic theoretical concepts of static magnetic shielding are summarized. Expressions describing the magnetic field produced by a solenoidal coil confined coaxially inside a long thin ferromagnetic cylinder of constant permeability are derived. Conditions for the optimum arrangement of a magnetic screen for whole‐body NMR systems are discussed. © 1989 Academic Press, Inc.
The synthesis of pulse sequences yielding arbitrary magnetization vectors
Authors: Shinnar Meir , Eleff Scott , Subramanian Harihara , Leigh John S.
Published: March 2007

A new procedure and algorithm are presented to allow the synthesis of a pulse sequence which will generate an arbitrary frequency‐dependent spin excitation. This procedure is a generalization of our previous paper, where this was done subject to the restriction that the spin excitation was symmetric about zero offset frequency, and pulses were restricted to being about a fixed axis. The required final z‐magnetization vector (Mz) is expressed as a function of the off‐resonance frequency as an Nth order complex Fourier series. We then form a consistent Fourier series for (Mxy). As many as 2 2N different pulse sequences may be directly generated all of which produce a different Mxy(f), but the same Mz(f). A pulse sequence is then generated which will yield the desired Mz(f) and Mxy(f). This is done by an analytic inversion of the Bloch equation, not by the classical Fourier approximation. This technique enables us to generate any Mz which is potentially realizable by a pulse sequence. © 1989 Academic Press, Inc.
Studies of the metabolism of human breast cancer spheroids by NMR
Authors: Ronen S. , Degani H.
Published: March 2007

Spheroids present a model for tumor behavior in vivo. In NMR studies, a problem of spheroid adhesion occurs. Here, we present a method which overcomes this problem and show the variations in phosphate metabolite concentrations as well as the rate of glucose metabolism as a function of spheroid age. © 1989 Academic Press, Inc.
Inhibition of lymphocyte stimulation by shift reagents
Authors: Sze Daniel Y. , Corbelletta Nancy L. , Shochat Stephen J. , Jardetzky Oleg
Published: March 2007

Lanthanide shift reagents have opened a new avenue in the study of membrane biochemistry, but their stabilities and biological reactivities remain questionable. We present evidence that shift reagents are not biologically inert, and that they exhibit the ability to inhibit stimulation of human peripheral lymphocytes at commonly used concentrations. A survey of various mitogens yielded no shift reagent‐resistant modes of stimulation, and a survey of various shift reagents yielded no effective and nontoxic alternatives. Involvement of calcium‐regulating mechanisms was not apparent. The assumption that lanthanide shift reagents used in NMR studies are nondestructive and physiologically innocuous is thus shown to be unwarranted.
Spatial localization for motion‐rejected nmr imaging: slo‐motion
Authors: Blackband S. J.
Published: March 2007

A new method of eliminating NMR image artifacts caused by random or sporadic motion is presented. The method uses only NMR techniques. A combination of a spatial localization method and a standard 2DFT imaging sequence is employed and consequently named SLO‐MOTION. Alternatively, the sequence may be used to aid motion artifact reduction by postprocessing methods. The feasibility of the method is demonstrated on a phantom.
Uterine cervical punch biopsy specimens can be analyzed by 1h mrs
Authors: Mountford Carolyn E. , James Delikatny E. , Dyne Marlen , Holmes Kerry T. , Mackinnon Wanda B. , Ford Robert , Christopher Hunter J. , Truskett Ian D. , Russell Peter
Published: March 2007

Biopsy specimens of the uterine cervix, including colposcopically directed punch biopsy specimens of females with atypical Papanicolaou smear tests, are suitable for analysis by magnetic resonance (MR) spectroscopy. A narrow lined lipid MR spectrum, characteristic of malignant tissue, is obtained from a 6‐mm3 biopsy specimen of histologically confirmed squamous carcinoma of the cervix. In contrast, specimens containing inflammatory cells generate a broad component only centered at 1.3 ppm with a T2 relaxation value of less than 350 ms. Most biopsy specimens which contain dysplastic cells or evidence of human papilloma virus (HPV) infection have a discernible lipid spectrum similar to that of the malignant tissue specimen. Long T2 relaxation values found in malignant tissue specimens at 1.3 and 1.2 ppm are observed in some but not all of the biopsies which show evidence of HPV infection. The suitability of small tissue samples, such as punch biopsy specimens, for study by MR illustrates the sensitivity of this technique and its potential as an aid to histopathological discrimination between the various precursor states of cervical cancer.
High‐field localized in vivo proton spectroscopy on micro volumes
Authors: Doddrell David M. , Field James , Crozier Stuart , Brereton Ian M. , Galloway Graham J. , Rose Stephen E.
Published: March 2007

A water‐suppressed volume‐selected in vivo 1H spectrum of 0.2 ml of a rat brain has been obtained at 200 MHz using the SPACE localization method. Good signal‐to‐noise and spectral resolution were obtained by averaging 256 acquisitions. The spectrum shows little T2 weighting effect.
Proton NMR study of the state of water in fibrin gels, plasma, and blood clots
Authors: Blinc A. , Lahajnar G. , Blinc R. , Zidanš A. , Sepe A.
Published: March 2007

A proton NMR relaxation and pulsed field gradient self‐diffusion study of water in fibrin gels, plasma, and blood clots has been performed with special emphasis on the effect of the sol‐gel and shrinkage transitions. Deuteron NMR in fibrin gels was also studied to supplement the proton data. It is shown that a measurement of the water proton or deuteron T1 / T2 ratio allows for a determination of the bound water fraction in all these systems. The change in the T1 / T2 ratio at the shrinkage transition further allows for a determination of the surface fractal dimension of the gel if the change in the volume of the gel is known. The self‐diffusion coefficient of water in these systems, which determines the transport properties of the gel, is found to be proportional to the free water fraction in both the nonshrunken and shrunken state. © 1990 Academic Press, Inc.
A homonuclear shift correlated and spatially localized spectroscopy using stimulated echoes
Authors: Desmoulin F. , Seelig J.
Published: March 2007

A new method which combines localized high‐resolution proton NMR spectroscopy with two‐dimensional correlated spectroscopy using stimulated echoes is presented. Stimulated‐echo correlated spectroscopy (STECSY) is a straightforward extension of the STEAM method. Experiments with phantoms illustrate the efficacy of STECSY. An in situ application on rat adipose tissue demonstrates that STECSY is a helpful tool with which to select and assign resonances in complex 1H NMR spectra. © 1990 Academic Press, Inc.
Nuclear magnetic resonance velocity spectra of steady flow
Authors: Wendt Richard E. , Nitz Wolfgang R. , Murphy Paul H.
Published: March 2007

Nuclear magnetic resonance (NMR) velocity spectra are a compact way to represent the flow information in a velocity‐resolved image set. Fully developed steady flow in long tubes gives NMR velocity spectra with average velocities which correlate well with the values derived from the flow rate. The ratio of average velocity to peak velocity correlates well with the Reynolds number. Tubes with compressed cross sections have velocity spectra similar to those of circular tubes. Tubes with irregular walls have velocity spectra in the entrance region that are markedly different from those from smooth‐walled tubes. © 1990 Academic Press, Inc.
A simple design for a double‐tunable probe head for imaging and spectroscopy at high fields
Authors: Gruetter Rolf , Boesch Chris , Müri Marcel , Martin Ernst , Wüthrich Kurt
Published: March 2007

A double‐tunable probe head based on the slotted tube resonator is described. Its performance at 2.35 T is comparable to that of single‐tunable designs. The main advantages are a large tuning range, a probe volume that is not reduced by the second circuit, and a simple design. © 1990 Academic Press, Inc.
31P NMR spectra of extremity sarcomas: Diversity of metabolic profiles and changes in response to chemotherapy
Authors: Koutcher Jason A. , Ballon Douglas , Graham Martin , Healey John H. , Casper Ephraim S. , Heelan Robert , Gerweck Leo E.
Published: March 2007

We have used 31P NMR spectroscopy to study 22 patients with suspected sarcomas prior to any treatment. The spectra are characterized by the same peaks noted in murine tumors. The mean pH was 7.14 ± 0.08 and PCr/Pi was 1.18 ± 0.83. Comparison of pH and PCr/Pi, ratios in human and a murine tumor with a low hypoxic cell fraction revealed no significant differences. Six patients subsequently received chemotherapy and three responded to therapy (based on pathologic examination and/or tumor reduction greater than 50%). The three responding patients were noted to have significantly lower PDE/ PME in their pretreatment spectra than the three nonresponding patients. The three responding patients with sarcomas also showed a rise of > 100% in PDE/PME during the first cycle of therapy. Two of the responding patients had an increase of 0.37 pH units during this interval, which was not detected in the nonresponding patients. These data suggest that 31P NMR spectroscopy may be a useful prognostic indicator in conjunction with other clinical parameters. © 1990 Academic Press, Inc.
Quantitation of blood‐brain barrier defect by magnetic resonance imaging and gadolinium‐DTPA in patients with multiple sclerosis and brain tumors
Authors: Larsson H. B. W. , Stubgaard M. , Frederiksen J. L. , Jensen M. , Henriksen O. , Paulson O. B.
Published: March 2007

In this study quantitation of the degree of deficiency of the blood‐brain barrier (BBB) in patients with multiple sclerosis or brain tumors, by using MRI, is shown to be possible. As a measure of permeability of the BBB to Gadolinium‐DTPA (Gd‐DTPA) the flux per unit of distribution volume per unit of brain mass was used. This quantity was found by introducing the longitudinal relaxation rate (R1) as a measure of concentration of Gd‐DTPA in the brain tissue in the mathematical model for the transcapillary transport over the BBB. High accordance between the observed data points and the model was found, and the results were comparable to results obtained from similar studies using positron emission tomography. The improved possibility of quantitating the defect of the BBB by MRI may give new information about pathogenesis or etiology, and leads to improved methods in monitoring the efficacy of treatments in intracranial diseases. © 1990 Academic Press, Inc.
The NMR phased array
Authors: Roemer P. B. , Edelstein W. A. , Hayes C. E. , Souza S. P. , Mueller O. M.
Published: March 2007

We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the “NMR phased array.” The NMR phased array offers the signal‐to‐noise ratio (SNR) and resolution of a small surface coil over fields‐of‐view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 × 512, 48‐cm FOV, and 32‐cm FOV) spin‐echo images of the thoracic and lumbar spine. Data were acquired from four‐element linear spine arrays, the first made of 12‐cm square coils and the second made of 8‐cm square coils. When compared with images from a single 15 × 30‐cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine ( ∼ 7 cm). © 1990 Academic Press, Inc.
High‐speed multislice T1 mapping using inversion‐recovery echo‐planar imaging
Authors: Ordidge R. J. , Gibbs P. , Chapman B. , Stehling M. K. , Mansfield P.
Published: March 2007

Tissue contrast in MR images is a strong function of spin‐lattice (T1) and spin‐spin (T2) relaxation times. However, the T1 relaxation time is rarely quantified because of the long scan time required to produce an accurate T1 map of the subject. In a standard 2D FT technique, this procedure may take up to 30 min. Modifications of the echo‐planar imaging (EPI) technique which incorporate the principle of inversion recovery (IR) enable multislice T1 maps to be produced in total scan times varying from a few seconds up to a minute. Using IR‐EPI, rapid quantification of T1 values may thus lead to better discrimination between tissue types in an acceptable scan time. © 1990 Academic Press, Inc.
Localized Proton NMR spectroscopy using stimulated echoes: Applications to human skeletal muscle in vivo
Authors: Bruhn H. , Frahm J. , Gyngell M. L. , Merboldt K. D. , Hänicke W. , Sauter R.
Published: March 2007

Localized proton NMR spectroscopy using stimulated echoes (STEAM) has been used to study metabolites in different proximal skeletal muscles of normal volunteers at rest. Single scan water‐suppressed proton NMR spectra obtained at 1.5 and 2.0 T (Siemens Magnetom) from a 64‐ml volume‐of‐interest (VOI) yield resonances due to triglycerides, phosphocreatine plus a minor contribution from creatine, and betaines comprising carnitine and choline‐containing compounds. The observation of the pH‐dependent resonances of carnosine required multiple acquisitions and echo times as short as 20 ms. T1 and T2 relaxation times of muscle metabolites were obtained by varying the repetition time and echo time of the STEAM sequence, respectively. Although rather long T2 values such as 180 ms for (phospho‐) creatine correspond to natural resonance line widths of only 2 Hz, the observed line widths of typically 10‐12 Hz are entirely determined by the short T2 relaxation times (25‐30 ms) of the water protons used for shimming. The spectroscopic results from 24 muscle studies on 17 young male volunteers show remarkable intra‐ and interindividual differences in the absolute signal intensities of mobile lipids. Further metabolic variations were observed for the relative concentrations of betaines (by a factor of 2) and carnosine (by a factor of 3) when total creatine is assumed to be constant. © 1991 Academic Press, Inc.
Data extrapolation for truncation artifact removal
Authors: Constable R. T. , Henkelman R. M.
Published: March 2007

Clinicians typically obtain high‐resolution clinical MR images in an effort to avoid the truncation artifacts that often arise in Fourier transform reconstruction of limited data. A method for reducing these artifacts in MR images, at the reconstruction stage, would allow for reduced imaging times, through the collection of fewer phase encode steps and increased signal‐to‐noise ratios, through increased pixel size. The approach to reducing truncation artifacts in MR images is developed and a simple algorithm is presented which significantly reduces truncation artifacts in images with as few as 96 phase encode steps. The algorithm is compared with a more sophisticated method of reconstructing truncation‐free images and is shown to be equivalently effective. Three clinical examples are shown illustrating the Success of the method. © 1991 Academic Press, Inc.