bluuebunny/crossref_metadata_2025 huggingface dataset:
T1,T2, and relative proton density at 0.35 T for spleen, liver, adipose tissue, and vertebral body: Normal values
Authors: Nyman Rickard , Ericsson Anders , Hemmingsson Anders , Jung Bo , Sperber Göran , Thuomas Karl Åke
Published: March 2007

An MRI installation (Magnetom, Siemens, software version B1 of NUMARIS) working at 0.35 T was used to estimate T1, T2, and relative proton density in the spleen, liver, adipose tissue, and vertebral body in 14 healthy volunteers. Two double‐echo sequences were applied for all subjects: TR = 500 ms, TE1 = 35 and TE2 = 70 ms; and TR = 1600 ms, TE1 = 35 and TE2 = 70 ms. The images were sampled in regions of interest and appropriate relaxation expressions fitted to the ROI data yielding relaxation parameters and relative proton densities. Relaxation expressions, included in standard software (Siemens), were compared to more elaborate functions, developed in parallel to this study. The latter were found more appropriate, especially for high T1 values, and gave the following mean values for the four tissues (estimated uncertainty of mean in parentheses) T1 (ms) 915(36), 428(5), 261(7), and 501(11); T2(ms) 79.7(8.8), 51.0(0.2), 59.8(1.0), and 64.7(0.8); and corresponding relative proton density (ρ, arbitrary units) 2088(136), 2182(10), 2915(49), and 2136(21). The uncertainty in the values was estimated in the fitting procedure and does not include systematic errors. The relative noise in the ROIs was about 9% and the reproducibility of the ROI mean values about 8%. © 1986 Academic Press, Inc.
Measurement of solute proton spin‐lattice relaxation times in water using the 1,3,3,1 sequence
Authors: Sankar S. S. , Molé P. A. , Coulson R. L.
Published: March 2007

1H NMR spin‐lattice relaxation times (T1) of the NCH3 proton resonances of phosphocreatine (PCr) and creatine (Cr) in water solutions were obtained using the 1,3,3,1 pulse sequence. These T1 values were equivalent to those obtained in D2O and water using either the conventional inversion‐recovery experiment or the 1,3,3,1 pulse sequence. Thus, the 1,3,3,1 sequence of proton NMR can provide an independent means along with phosphorous NMR for assess PCr and for the study of the creatine kinase reaction (PCr + ADP ⇌ ATP + Cr) in aqueous solutions and perhaps in biological preparations. © 1986 Academic Press, Inc.
The utilization of two frequency‐shifted sinc pulses for performing volume‐selected in vivo NMR spectroscopy
Authors: Doddrell David D. , Galloway Graham J. , Brooks William M. , Bulsing J. Mark , Field James C. , Irving Michael G. , Baddeley Hiram
Published: March 2007

A new approach to volume‐selected in vivo NMR spectroscopy uses two frequencyshifted sinc pulses, in conjunction with pulsed field gradients, to destroy the coherence of the unwanted signals. A hard π/2 pulse can then be used to read the z magnetization in the region of interest. This method is independent of T2, provides complete volume selection in a single acquisition, and can be readily implemented on most high‐field commercial imaging/spectroscopy systems. © 1986 Academic Press, Inc.
In vivo proton spin‐lattice relaxation times of normal and dystrophic muscles
Authors: Narayana P. A. , Brey W. W. , Kulkarni M. V. , Misra L. K.
Published: March 2007

In vivo spin‐lattice relaxation times (T1) of water and lipid protons were measured in normal and dystrophic chicken pectoralis muscles at different ages. Values were obtained with a surface coil used as both a receiver and a transmitter. A 2θ‐T1‐θ‐Acquisition sequence was used for these measurments. Accuracy was verified with an inversion‐recovery method using a slotted tube resonator as the transmitter and a surface coil as the receiver. It was observed that (1) the T1 values of water protons in normal muscles decrease with age, (2) the T1 values of water protons do not change with age in dystrophic muscles, and (3) the T1 values of lipid protons increase with age in normal and dystrophic muscles. These results indicate a failure of the normal maturation of dystrophic muscles. © 1987 Academic Press, Inc.
A pulse reflectometer for routine monitoring of transmitted and reflected power in physiological NMR studies
Authors: Funk Alex , Rippy Ronnie , London Robert E.
Published: March 2007

A simple circuit design is described which provides LED readout of transmitted and reflected pulsed of power. The utility of monitoring these variables in physiological NMR studies is discussed. © 1987 Academic Press, Inc.
Echo acquisition during frequency‐selective pulse trains for proton spectroscopy of metabolites in vivo
Authors: Meyer Ronald A.
Published: March 2007

Suppression of water and fat in proton spectra of rat skeletal muscle was achieved by acquisition of the spin echoes formed in the steady state after a series of frequency‐selective composite pulses of constant amplitude, phase, and interpulse interval. The method enables observation of lactate in the presence of fat without resorting to difference spectroscopy, and on spectrometers which permit data acquisition immediately prior to a pulse, enables much faster data accumulation compared to standard echo sequences. © 1987 Academic Press, Inc.
Analysis of spin‐echo rephasing with pulsatile flow in 2D FT magnetic resonance imaging
Authors: Katz J. , Peshock R. M. , McNamee P. , Schaefer S. , Malloy C. R. , Parkey R. W.
Published: March 2007

The effects of pulsatile flow on spin phases in spin‐echo magnetic resonance imaging are considered. General expressions for the spin phases of the first four echoes are derived in terms of the Fourier coefficients of flow. These expressions are valid for any time‐dependent acceleration and, hence, are not restricted to constant acceleration. The derived expressions are then theoretically evaluated for aortic flow and examined at different points in the cardiac cycle. Our results show that rephasing may occur at certain points in the cardiac cycle for either even or odd echoes depending upon the particular Fourier coefficients of the velocity function and the spin‐echo delay time. However, even‐echo rephasing is not always necessarily valid. Furthermore, the possibility of determining the flow velocities in the body with an appropriate series of imaging studies is also discussed. © 1987 Academic Press, Inc.
MRI: The development of T2 contrast with rapid field echo sequences
Authors: Young I. R. , Payne J. A. , Collins A. G. , Bydder G. M.
Published: March 2007

The soft tissue contrast obtained in fast imaging using rapidly repeated partial saturation sequences is usually based on differences in T1. We describe here an extension of the method which results in the development of clinically useful T2‐based contrast. © 1987 Academic Press, Inc.
A comparison of some gradient‐encoded volume‐selection techniques for in vivo NMR spectroscopy
Authors: Galloway Graham J. , Brereton Ian M. , Brooks William M. , Field James , Irving Michael , Baddeley Hiram , Doddrell David M.
Published: March 2007

Four of the techniques proposed for in vivo volume‐selected NMR spectroscopy have been compared using a simple phantom with a large background water signal which was outside the region of interest. The methods VSE, SPACE, SPARS, and DIGGER all use pulsed field gradients for spatial encoding and were tested with a symmetric and an asymmetric phantom. SPACE was used to obtain volume‐selected 1H NMR spectra of a human leg, demonstrating excellent discrimination between bone marrow and muscle. © 1987 Academic Press, Inc.
Even‐echo rephasing and constant velocity flow
Authors: Katz J. , Peshock R. M. , Malloy C. R. , Schaefer S. , Parkey R. W.
Published: March 2007

It has been shown previously that for constant magnetic field gradients, constant velocity flow leads to even‐echo rephasing for all echo delay times. We show that for flow which is not pluglike, even‐echo rephasing also occurs for the pulsed readout gradients used in magnetic resonance imaging if and only if the gradients begin at the time the 90° pulse is applied. We also show for these gradients that even‐echo rephasing for all echo delay times in the case of nonpluglike flow implies a constant flow velocity at the point considered. Furthermore, it suffices to assume the vanishing of the spin‐echo phase for any even echo, since the vanishing of any even echo for all echo delay times implies that all other even echoes also vanish identically. The odd echoes are then all equal to each other and proportional to the flow velocity. If acceleration is present, it may then be seen that for nonpluglike flow, even‐echo rephasing may only be present for some but not all echo delay times.

However, for the typicall slice selection gradients used in magnetic resonance imaging or for usual readout gradients starting after the 90° pulse is applied, it is shown that for constant velocity flow the even‐echo phases do not vanish identically. Hence, rephasing cannot always ocur for nonpluglike flow in either of these situations. Furthermore, the spin‐echo phases are proportional to the flow in velocity. The converse is also showh; namely, if the phase of any even echo at given point is proportional to the velocity at the point considered for all echo delay times, then the flow velocity is constant at the point. Furthermore, the phases of all even echoes are also equal to each other and proportional to the flow velocity at that point. In addition, the odd echoes are then also equal to each other and proportional to the flow velocity, but with a proportionally constant different from that of the even echoes. © 1987 Academie Press, Inc.
Magnetic resonance imaging of parasitic tapeworm larvae Taenia crassiceps cysticerci in the peritoneal cavity of mice
Authors: Haselgrove John , Grun James , Owen Charles S. , Larralde Carlos
Published: March 2007

Because of their long T2 relaxation time (400 ms), larvae of the tapeworm Taenia crassiceps can be distinctly imaged in the mouse peritoneal cavity by NMR. An echo time of 400 ms sharply contrasted the parasites against the surrounding abdominal organs. A rapid, quantitative assay for parasite load can be obtained by recording the amplitude of a spin echo with no applied gradients at an echo time of 400–1000 ms. The T2 of the vesicular fluid of the human parasite Taenia solium was also long (600 ms), indicating that the same approach (long TE and long TR) can be used to image this parasite for diagnosis of human cysticercosis by NMR imaging. © 1987 Academic Press, Inc.
NMR investigation of hydroxyethyl starch‐induced aggregation of human erythrocytes
Authors: Caines G. Herbert , Goldstein J. H.
Published: March 2007

Aggregation of human erythrocytes at physiological hematocrit by hydroxyethyl starch (HES) was investigated with a 1H nuclear magnetic resonance method which measures the erythrocyte mean water exchange time, τa. A relationship that takes into account the effect of the aggregate as the water‐exchanging unit was used to transform τ. values into the number of cells per aggregate, n. The procedure permits the determination of the time course of aggregation as well as its initial and equilibrium status. The values of n at equilibrium range from about 2 to 4 cells over the concentration of 1 to 5% HES in isotonic saline. The aggregation of erythrocytes in the presence of HES was found to follow first‐order kinetics. The feasibility of this technique for application in the study of diseased states is indicated. © 1987 Academic Press, Inc.
Magnetic resonance imaging of midline brain tumors using inversion recovery sequences at 0.08 T (3.4 MHz)
Authors: Smith F. W.
Published: March 2007

The use of inversion recovery sequences to highlight intracranial tumors in children is illustrated. The effect of changing the inversion time (TI) to produce the best spatial resolution and to highlight the contrast resolution between different tumors and normal brain is analyzed. The normal appearances and clinical examples in the central nervous system are used to illustrate the options that are available using IR sequences. Variation of TI for providing a means of differentiating short T1 lesions from long T1 lesions is discussed, short TI sequences being best for demonstrating gliomas and astrocytomas whilst medium/ long TI sequences are best for demonstrating vascular abnormalities and short T, tumors. Inversion recovery imaging is considered to be an accurate alternative to spin‐echo imaging as Currently applied. © 1987 Academic Press, Inc.
Surface coil holder for Signa
Authors: Bárány Michael , Mertz George T. , Ivicic Joseph , Mok Evelyn , Spigos Dimitrios G. , Kleps Robert A.
Published: March 2007

A surface coil holder is described for the General Electric Signa spectrometer. This allows for accurate positioning of the 31P coil relative to that of the 1H coil used for tissue slice localization. © 1987 Academic Press, Inc.
31P NMR studies on recovery from hypoxia of human tumor cells
Authors: West‐Jordan J. A. , Smith A. , Myint S. , Gardner J. A. , Abraham R. J. , Edwards R. H. T. , Warenius H. M.
Published: March 2007

We describe the use of 31P NMR spectroscopy in the study of metabolic changes related to hypoxia in cultured human tumor cells in vitro. The 31P NMR spectrum can easily distinguish between metabolically active cells, metabolically inactive “dormant” cells, and necrotic cells. A crucial observation was that of the ability of the “dormant” cells to resume active metabolism on incubation with oxygen after long periods of hypoxia. © 1987 Academic Press. Inc.
RAPID—A new method for fast imaging using a single slice of 2‐magnetization
Authors: Brooks William M. , Brereton Ian M. , Doddrell David M.
Published: March 2007

A single slice of z‐magnetization is used to generate high‐speed images. The slice selection step is achieved using two sin–sinc pulses. This procedure eliminates the need for continual slice gradient reversal, a requirement for the FLASH technique. The RAPID imaging method has less inherent T1 and/or T2 dependence than current fast imaging methods and is more sensitive. © 1987 Academic Press, Inc.
A complication in prescan strategy when using surface coils
Authors: Jesmanowicz A. , Froncisz W. , Hyde James S.
Published: March 2007

The “prescan” process for setting the gain of an MRI scanner can be confounded by an effect arising from the spatial variation of the angle between the vector reception field of a local or surface coil and the excitation field of a whole‐body coil. It is most pronounced when the phase‐encoding direction is parallel to the plane of the coil but not along the magnetic field. The largest signal is shown to reside in a data row that is shifted from the one that corresponds to zero phase‐encoding gradient. The effect depends on the field‐of‐view and the dimensions of the receiving coil. Strategies are suggested by which manufacturers of scanners can cope with this intrinsic problem. In the meantime, users of surface coils should be aware of the difficulty. © 1987 Academic Press, Inc.
31P magnetic resonance spectroscopy of traumatic spinal cord injury
Authors: Vink Robert , Knoblach Susan M. , Faden Alan I.
Published: March 2007

31P magnetic resonance spectroscopy (MRS) was applied in vivo to study metabolic changes in spinal cord after experimental traumatic injury. Severe trauma, resulting in spastic paraplegia, caused an early and sustained loss of high energy phosphates with profound intracellular acidosis. Early metabolic changes after traumatic spinal injury may predict irreversible tissue damage. © 1987 Academic Press, Inc.
MR microscopy on rats in vivo at 4.7 T using surface coils
Authors: Rudin Markus
Published: March 2007

MR microscopy on intact rats using a single surface coil is reported. The use of the same coil for excitation and detection is experimentally very simple and results in a smaller field‐of‐view than the conventional setup using homogeneous excitation (whole‐body coil or a large surface coil) and a small receiver surface coil. Images at 4.7 T with 60 × 60‐m̈m pixels and an 800‐m̈m slice thickness have been obtained from the eye and ankle joint of a living rat with good anatomical definition. This corresponds to a four‐ to eightfold reduction in voxel size as compared to high‐resolution images obtained with a 30‐mm resonator probe. Many of the basic MRI experiments (spin‐echo, FLASH, chemical‐shift selective MRI) may be carried out in a straightforward way with this one‐coil setup. Sequences relying on a homogeneous flip angle distribution require a whole‐body excitation Coil. © Academic Press, Inc.
Surface coil for MR imaging of the skin
Authors: Hyde James S. , Jesmanowicz A. , Kneeland J. Bruce
Published: March 2007

A strategy for the design of surface coils for the imaging of extended superficial planar anatomic structures including skin and subcutaneous fat is presented. The central concept is to create an array of closely spaced coplanar radiofrequency current filaments parallel to B0 the polarizing field, with opposite current directions in adjacent filaments. A specific coil design with four such filaments for imaging at 1.5 T is presented. It consists of two pairs of counterrotating current (CRC) coils. Phantom images as well as representative images of normal skin are shown. © Academic Press, Inc.
Water‐suppressed volume‐selected 1H NMR spectroscopy in viva: Application to study tumor metabolism
Authors: Haseler Luke J. , Galloway Graham J. , Field James , Irving Michael G. , Doddrell David M.
Published: March 2007

Volume selection using SPACE has been combined with water suppression techniques to provide high‐resolution 1H NMR spectra from aqueous solutions. The technique developed was used to obtain spectra from a tumor growing on the hind leg of a rat. Water suppression factors of between 1000 and 2000 were achieved simultaneously with excellent volume selection.
Mobile phospholipid signals in NMR spectra of cultured human adenocarcinoma cells
Authors: Guidoni L. , Mariutti G. , Rampelli G. M. , Rosi A. , Viti V.
Published: March 2007

An intense peak is visible in the phosphodiester region of the 31P NMR spectra of human colon adenocarcinoma HCT‐8R cells. A signal at the same frequency, partially deriving from mobile phospholipids, is also observable in the spectra of total membranes and of perchloric acid extracts prepared from the same cells. The phosphodiester signals of glycerophosphorylcholine, glycerophosphorylethanolamine, and glycerophosphorylserine resonate at lower fields with respect to this broader peak and appear only in aged samples. Enzymatic treatments of the extracts would indicate that ribonucleic acid also contributes to the broad phosphodiester signal. Moreover, 1H NMR spectra show the presence of lipid structures, characterized by high mobility, in the cell and in the membrane samples, similar to what was already observed in other tumor cells and tissues. © Academic Press, Inc.
Acquisition order and motional artifact reduction in spin warp images
Authors: Dixon W. Thomas , Brummer Marijn E. , Malko John A.
Published: March 2007

Multiple averaging can be a powerful tool against motional artifacts if significant motion occurs between the redundant acquisitions taken at a given gradient strength. However, if the time delay between these redundant measurements is too short, data or images depicting the patient is exactly the same position will be combined. Pooling such identical data has no effect on motional artifacts. This problem can be solved by increasing TR, increasing the number of redundant acquisitions, or changing the order in which acquisitions are taken. Usually all acquisitions at a particular value of the warp gradient are taken before proceeding to the next gradient value. This order minimizes motion between redundant acquisitions and so maximizes artifacts. The effect of other acquisition orders on both periodic and nonrepetitive motion is discussed. Human images for breathing and phantom results for Single‐Occurrence motions are presented. © 1988 Academic Press, Inc.
Accurate quantification of in vivo31P NMR signals using the variable projection method and prior knowledge
Authors: van der Veen J. W. C. , de Beer R. , Luyten P. R. , van Ormondt D.
Published: March 2007

Free induction decay signals are analyzed by fitting a model function directly in the time domain. No starting values are needed for linear model parameters, and omission of corrupted data points poses no problems. A significant gain of accuracy is achieved by imposing prior knowledge about the model parameters. © 1988 Academic Press, Inc.
Multiline chemical‐shift (MULCH) imaging
Authors: Johnson G. , Tofts P. S.
Published: March 2007

A fast chemical‐shift imaging technique is presented. The method involves saturating all spins outside a plane, selectively exciting individual lines, phase encoding along each line, sampling the FID without gradients, and interleaving interrogation of multiple lines. A 64 × 64 array of spectra with 5 Hz resolution can be obtained in 17 min. © 1988 Academic Press, Inc.
Non‐Brownian water self‐diffusion in lung tissue
Authors: Kveder M. , Lahajnar G. , Blinc R. , Zupančič I.
Published: March 2007

Pulsed field gradient NMR measurements of rat lung tissue have shown that the apparent water self‐diffusion coefficient is nearly an order of magnitude smaller than that of free water and moreover is not constant but vanes as the inverse square root of the diffusion time. The mean square displacement of water molecules is similarly proportional to the square root of the diffusion time. Possible origins of this non‐Brownian behavior are discussed. © 1988 Academic Press, Inc.
Determinants of water proton T1 in blood serum
Authors: Raeymaekers H. H. , Borghys D. , Eisendrath H.
Published: March 2007

Water proton T1 (10.7 MHz; 7°C) and albumin and globulin contents were measured in the blood serum of 30 normal volunteers. The T1 relaxivity of serum albumin and globulin (i.e., the change of water relaxation rate l/T1 per concentration unit) was determined in pure albumin and globulin solutions. It is shown that more than 90% of the serum relaxation rate 1/Tl is due to the proteins, making T1 a nonspecific blood parameter. In addition five pathological serum samples were examined, explaining clearly why serum T1is not a clinically useful measurement. © 1988 Academic Press, Inc.
Sodium NMR imaging of lung water in rats
Authors: Kundel Harold L. , Shetty Anil , Joseph Peter M. , Summers Ronald M. , Kassab Eleanor A. , Moore Bethanne
Published: March 2007

Coronal proton and sodium images of control rats and rats with either increased permeability edema produced by intravenous alloxan (300 mg/kg) or increased pressure edema produced by saline infusion (2 ml/min) were obtained. Axial chest CT images were used to monitor the development of pulmonary edema. Immediately after the imaging session compartmental lung water was measured gravimetrically. The sodium and proton imaging were done sequentially in a 31‐cm‐bore 1.9‐T magnet without moving the animal. The anatomical boundaries of the lung on the proton images were transferred to the sodium images for calculation of the average sodium signal intensity which was determined by extrapolating the mean values from five echoes to time zero. The sodium signal intensity was correlated (r = 0.7) with the total water fraction. There was poor correlation (r = 0.56) with the extravascular water due to confounding by the sodium vascular signal. © 1988 Academic Press, Inc.
Effect of phase‐encoding direction upon magnetic resonance image quality of the heart
Authors: Thickman David , Rubinstein Ronald , Askenase Alan , Cabellero‐Saez Annette
Published: March 2007

In order to optimize overall cardiac image quality on MR images experienced observers were asked to rank and rate MR images of the heart. The effect of phase‐encoding direction and use of cardiac triggering with and without respiratory gating was examined in three orthogonal imaging planes. Results indicate that use of both respiratory and cardiac gating yields the best images. Adequate images of the heart can be obtained without respiratory gating. The quality of images of the heart can be optimized by proper selection of the direction of the phase‐encoding gradient. These are improved by using horizontal phase encoding in the sagittal plane and vertical phase encoding in transverse and coronal planes. © 1988 Academic Press, Inc.
Magnetic field shimming by fourier analysis
Authors: Brateman Libby , Bowman Thomas T. , Dønstrup Sune , Scott Katherine N.
Published: March 2007

The homogeneity of the magnetic field of an Oxford 85/310HR magnet was optimized with the use of passive shims (i.e., pieces of steel) and room‐temperature electronic shims. Both the characteristics of the passive shims and the current settings for the room‐temperature electronic shims were calculated with the goal of minimizing field inhomogeneities as assessed by Fourier analysis of data from circular field plots. The measurement techniques, the methods of data analysis, and the techniques employed in correcting the magnetic field are presented. Difficulties and constructive approaches are suggested in these descriptions. The final results show a field of excellent homogeneity over a 10‐cm‐diameter spherical volume, with a peak‐to‐peak variation of 3.2 ppm, which is better than the manufacturer's expected specification of 5 ppm. A water‐filled sphere of 10 cm diameter gave a half‐height linewidth of 0.14 ppm after a small amount of additional touch‐up shimming. The field homogeneity as corrected is much improved over its original state, allowing the acquisition of improved spectra from samples of a size several centimeters in each linear dimension. Thus the field homogeneity is more useful for in vivo spectroscopy, the purpose for which the magnet was intended. © 1988 Academic Press, Inc.
In vivo magnetic resonance imaging of sodium in the human body
Authors: Ra J. B. , Hilal S. K. , Oh C. H. , Mun I. K.
Published: March 2007

Sodium magnetic resonance imaging of the human body in vivo has been tried and its clinical application is considered. A short T2 imaging algorithm with total volume excitation and a specialized RF coil focused to the region of interest have been adopted to improve the signal‐to‐noise ratio. Using a 1.5‐T human body imaging system, several important organs including heart, liver, gallbladder, kidney, and spine have been examined to demonstrate their sodium concentration in vivo. © 1988 Academic Press, Inc.
Very rapid lactate measurement in ischemic perfused hearts using 1H MRS continuous negative echo acquisition during steady‐state frequency selective excitation
Authors: Keller Andrew M. , Sorce Dennis J. , Sciacca Robert R. , Barr Mark L. , Cannon Paul J.
Published: March 2007

Using 1H MRS continuous negative echo acquisition during steady‐state frequency selective excitation (CASTLE) myocardial lactate accumulation was followed in a globally ischemic perfused rat heart model. 1H MRS CASTLE derived lactate determinations were verified biochemically and were measured during ischemia and reperfusion (both in the absence and in the presence of a known inhibitor of glycolysis). In addition, using the Bloch equations modified for the effect of diffusion in the presence of a magnetic field gradient the theoretical dependency of measurements made with CASTLE upon T1 T2 and the flip angle α were demonstrated. It was found that 1H MRS CASTLE allowed for rapid identification of the lactate ‐CH3 resonance in an isolated perfused heart with little shimming required, and excellent water and lipid suppression. Measurements of lactate using this technique reflected a true difference in myocardial lactate as evidenced by biochemical analysis and the expected changes in tissue lactate that accompanied reperfusion and ischemia in the presence of a glycolytic inhibitor. Theoretical calculations demonstrated that the dependency of the relative signal intensity obtained with 1H MRS CASTLE was a complex function of T1 T2, and α These calculations also demonstrated the theoretical feasibility of applying 1H MRS CASTLE to localized spectroscopy using a surface coil. © 1988 Academic Press, Inc.
The application of depth‐pulse localized 31P NMR spectroscopy to monitor tumor metabolism and response to chemotherapy in the rat kidney
Authors: Stewart C. A. , Hanstock C. C. , Allen P. S.
Published: March 2007

To illustrate the spatial variations in metabolism within tumors, 31P spectral data are presented from a predefined, depth‐pulse localized region of a rat kidney impregnated with Walker sarcoma cells. These data display the changes in energy metabolism during infiltration of the kidney by the tumor and during treatment of the tumor with cyclophosphamide. © 1988 Academic Press, Inc.
31P NMR relaxation time studies of 2,3‐diphosphoglycerate in solution and intact erythrocytes
Authors: Christensen Marianne , Jacobsen Jens Peter
Published: March 2007

The 31P T1 spin‐lattice relaxation times and nuclear Overhauser effects of 3‐P and 2‐P in 2,3‐diphosphoglycerate (2,3‐DPG) have been measured in pure water solutions and in suspensions of intact erythrocytes. It was found that extremely careful purification of the water solutions from paramagnetic impurities was necessary in order to obtain reproducible results. The dominant relaxation mechanism in purified samples was shown to be the dipole‐dipole interaction. Contributions from the chemical‐shift anisotropy mechanism were demonstrated to be important at higher magnetic field strengths. Based upon the measurements in water solutions and intact erythrocyte suspensions it was concluded that there could be observed no significant influence of the oxygenation state of hemoglobin on the 31P T1 values of 2,3‐DPG. © 1988 Academic Press, Inc.
NMR measurement of the degree of oil/water partition of paramagnetic contrast media
Authors: Hall Laurance D. , Hogan Patrick G.
Published: March 2007

Magnetic resonance imaging techniques have been used to evaluate the oil/water partition of a series of stable nitroxide free radicals. The degree of partition, K, closely parallels the order of chemical polarity and lipophilicity of these compounds. This method also provides insight into both their nuclear magnetic resonance relaxation characteristics and pharmacokinetics. © 1988 Academic Press, Inc.
Paramagnetic contrast enhancement at 0.02 T: An experimental study using Gd‐DOTA in normal and hydronephrotic kidneys
Authors: Niemi Pekka , Paajanen Hannu , Määttänen Heli , Komu Markku , Erkintalo Minna , Alanen Anu , Dean Peter B. , Kormano Martti
Published: March 2007

Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd‐DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd‐DOTA injection. The enhancement pattern was similar in 1‐ and 3‐week‐old hydronephrosis. The effect of Gd‐DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd‐DOTA injection (0.1 mmol/kg) the TI times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd‐DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fieldss (>0.15 T). © 1988 Academic Press, Inc.
31P FLASH NMR Imaging
Authors: Haase A. , Leibfritz D. , Werk W.
Published: March 2007

A method of 31P FLASH NMR imaging is described using a low flip angle excitation pulse and three‐dimensional Fourier transform spectroscopic imaging (3DlT). In vivo high‐resolution 31P NMR spectra are obtained for each of 32 × 32 image elements using a minimum measuring time of 1.5 min. 31P FLASH images of a rat showing the spatial distribution of phosphocreatine, α‐, β‐, and γ‐ATP have been measured in a 4.7‐T magnet with a spatial resolution of 6 mm. © 1988 Academic Press, Inc.
Differentiation of human tumors from nonmalignant tissue by natural‐abundance 13C NMR spectroscopy
Authors: Halliday Karen R. , Fenoglio‐Preiser Cecllla , Sillerud Laurel O.
Published: March 2007

High‐quality, high‐resolution, proton‐decoupled natural‐abundance 13C NMR spectra have been obtained in vitro at 100.6 MHz from unprocessed human pathology specimens of tumors and adjacent nonneoplastic control tissues from lung, colon, and prostate. In these preliminary studies, specific molecular parameters were identified from the spectra that distinguished neoplastic from nonneoplastic tissue of a given organ in all sites studied. The NMR results were congruent with data derived from histochemical and biochemical examinations of the tissues and with previous studies using non‐NMR methods. In particular, a comparison of the spectra of prostatic adenocarcinoma with that of adjacent hyperplastic tissue revealed the following differences: The tumors contained (1) larger amounts of triacylglycerols, (2) smaller amounts of citrate, and (3) acidic mucins. These transformation‐associated deviations from the normally high amounts of citrate and low amounts of lipids in the prostate are consistent with an alteration in either the concentration or the activity of ATP‐citrate lyase in the tumors. The 13C NMR spectra of colonic adenocarcinoma tissue showed that this tumor type contained (1) smaller signals from triacylglycerols, (2) larger signals from phospholipids and lactate, and (3) decreased lipid fatty acyl chain saturation, when compared to spectra from adjacent normal colon. Colloid carcinoma, another variant of colonic carcinoma, showed prominent 13C resonances from glycoproteins, which were absent from the spectra of normal colon, and from spectra from the more common pattern of colonic adenocarcinoma. Smaller 13C NMR signals from mucins and other proteins, and the presence of triacylglycerol signals distinguished poorly differentiated lung carcinoma and from nonmalignant lung tissue. These results indicate that natural‐abundance 13C NMR spectroscopy may constitute a unique, nondestructive method, for the simultaneous measurement of a large number of tissue metabolites and structural components of significance to the study and diagnosis of a wide range of human tumors. © 1988 Academic Press, Inc.
Analysis by the Carr–Purcell–Meiboom–Gill sequence of the influence of P388 leukemia and of cis‐diamminedichloroplatinum(II) nephrotoxicity on water compartmentalization in kidneys and spleens of mice
Authors: François A. , Van Gerven L. , Atassi G. , Eisendrath H. , Gielen M. , Willem R.
Published: March 2007

The multiexponential behavior of the decay curves obtained in vitro by a Carr‐Purcell‐Meiboom‐Gill (CPMG) sequence from spleens and kidneys of mice is analyzed. The mice were inoculated with the acute lymphocytic P388 leukemic cells and treated with the anticancer drug cis‐diamminedichloroplatinum(II), cis‐Pt. Kidneys and spleens of control animals display four relaxation components. The two longest ones were assigned, in the kidneys, in decreasing order of their relaxation time value, to intracellular and extracellular water, respectively. In spleens, the reversed assignment resulted. The two shortest ones are assigned to different tightly bound hydration water compartments, the fastest relaxing one being more greatly influenced by the unobservable crystalline water. No significant systemic effect on the intra‐ and extracellular water relaxation times could be observed in the kidneys under P388 leukemia inoculation, despite an apparent increase in the intracellular water content. In contrast, drug administration results in the apparent decrease in or even disappearance of the extracellular water component, with an increase in both relaxation time and apparent fraction of the intracellular water. These effects correlate well with changes in the usual nephrotoxicity parameters and are explained in terms of the well‐known cell damage in kidneys under cis‐platinum administration. A systemic effect under P388 leukemia disease is observed for the spleen, resulting again in the disappearance of the extracellular water component. The latter is related to splenomegaly due to invasion of the organ by leukemic cells during disease development. © 1988 Academic Press, Inc.
Relaxometry of calf lens homogenates, including cross‐relaxation by crystallin NH groups
Authors: Beaulieu Christopher F. , Clark John I. , Brown Rodney D. , Spiller Marga , Koenig Seymour H.
Published: March 2007

We studied the magnetic field dependence of the longitudinal relaxation rates of water protons (1/T1 nuclear magnetic relaxation dispersion (NMRD) profiles) in transparent homogenates of calf lens. The samples included nuclear homogenates with total (heterogeneous) crystallin contents between 34% (v/v) (native) and 14% (diluted) as well as cortical homogenate, 21% (native) and 34% (concentrated). The NMRD profiles had two components: a monotonic dispersive component (analogous to that of both globular protein solutions and diamagnetic tissue) and “14N quadrupolar peaks.” 14N peaks have never been reported for protein solutions, only for tissues and dehydrated proteins. These peaks occur between 0.5 and 5 MHz proton Larmor frequency and arise from interactions of solvent water protons with NH moieties of proteins. The 14N peaks in lens cytoplasm are very large and may correlate with the crystallin structure and interactions required to maintain short‐range order and lens transparency. The monotonic and 14N quadrupolar components were largest in concentrated samples, but with different concentration dependencies. The dispersive components of samples above ≈ 19% protein concentration had a fixed functional form, the amplitude of which vaned with protein volume fraction, f, by the multiplicative factor f/(1 ‐ f), suggesting spatial organization and dynamics of the solute proteins that are relatively independent of water content. In contrast, at concentrations less than 19%, the NMRD profiles are concentration dependent, indicating a dependence of the orientational relaxation time of the proteins on protein‐protein interactions seen previously in other globular proteins at these concentrations. The 14N peaks are not resolved below ≈ 19% protein and increase linearly with incremental volume fraction at protein concentrations above 19%. In addition, the 14N peaks in nuclear homogenates are 50–100% larger than those ofcortical homogenates at the same concentrations. Partial substitution of solvent D2O for H2O decreases the peak heights, indicating that an exchangeable proton mediates the interaction between solvent protons and protein 14N nuclei. © 1988 Academic Press, Inc.
Number of inner‐sphere water molecules in Gd3+ and Eu3+ complexes of DTPA‐amide and ‐ester conjugates
Authors: Geraldes Carlos F. G. C. , Sherry A. Dean , Cacheris William P. , Kuan Kah‐Tiong , Brown Rodney D. , Koenic Seymour H. , Spillers Marga
Published: March 2007

The inner‐sphere water coordination number for Eu3+ and Gd3+ complexed with five DTPA analogs, in which one or two terminal carboxylate groups are functionalized as propyl amides or propyl esters, have been studied using phosphorescence lifetime and nuclear magnetic relaxation dispersion (NMRD) measurements. Both methods show that the water coordination number does not increase above that observed for the analogous DTPA complexes. The phosphorescence lifetime results indicate that all five Eu3+ complexes have one inner‐sphere water molecule at 25°C. The NMRD profiles for three of the Gd3+ complexes at 25°C are also consistent with one inner‐sphere water molecule, whereas two complexes have profiles consistent only with a mixture of complexes, 50% containing a single water molecule and 50% with none. Lowering the temperature alters the population of these species such that all five Gd3+ complexes have significantly less bound water on average at 5°C. These results explain the anomalous temperature dependencies of the NMRD curves reported previously for the Gd(DTPA)–protein conjugates. We suggest that the Gd(DTPA)–conjugate systems have a fluxional coordination sphere whereby the amount of inner‐sphere coordinated water vanes from near zero at 5°C to a high Of two near 37°C. © 1988 Academic Press, Inc.
In Vivo13C NMR Spectroscopy of the Human Prostate
Authors: Sillerud Laurel O. , Halliday Karen R. , Griffey Richard H. , Fenoglio‐Preiser Cecilia , Sheppardy Scott
Published: March 2007

The metabolism of the normal and hyperplastic human and rat prostate differs from that of other tissues in that this organ supports and secretes high concentrations of citrate. During the dedifferentiation process that is characteristic of neoplasia, the ability of the prostate to maintain these high citrate levels is markedly diminished. We undertook a natural abundance 13C NMR study of the human and rat prostate in vitro and the human organ in vivo in order to determine whether the amounts of citrate in the nonmalignant prostate were sufficiently high to be detected. We report here our success at detecting citrate via 13C NMR in all three of these systems. © 1988 Academic Press, Inc.
13C nuclear magnetic resonance spectroscopy of glucose metabolism in human red blood cells
Authors: Ghai Geetha , Gonnella Nina C.
Published: March 2007

Glucose metabolism of human red blood cells was investigated using carbon‐13 nuclear magnetic resonance spectroscopy under both oxygenated and nonoxygenated conditions. These results show that under oxygenated conditions reversal of 3‐phospho‐glyceraldehyde to glucose is in competition with its catabolism to lactate. © 1988 Academic Press, Inc.
Evaluation of polyaza macrocyclic methylene phosphonate chelates of Gd3+ ions as MRI contrast agents
Authors: Geraldes Carlos F. G. C. , Brown Rodney D. , Cacheris William P. , Koenig Seymour H. , Sherry A. Dean , Spiller Marga
Published: March 2007

Gd(DTPA)2− (diethylenetriaminepentaacetic acid) and the polyaza macrocyclic Gd(DOTA)− (1,4,7,10‐tetraazacyclododecane‐N, N′,N″,N′″) are paradigms of general purpose paramagnetic complexes useful for enhancing contrast in magnetic resonance imaging (MRI). It is of both fundamental and practical interest to determine how one might modify the chemical structure of these chelate complexes to improve their utility for MRI in specific circumstances. In the present work, we investigated polyaza methylene phosphonate complexes of Gd3+ ions to compare their NMRD profiles with those of their carboxylate analogs and with Gd(DTPA)2−. We find that the number q of exchangeable water molecules coordinated directly to the Gd3+ ions tends to be smaller in the phosphonates, in principle reducing their utility in MRI. However, these phosphonates have a tendency to oligomerize, and the resulting decrease in rotational mobility of the paramagnetic oligomers increases their relaxivity at higher fields, offsetting the effect of decreases in q. In particular, Gd(DOTRP)3− (1,5,9‐triazacyclododecane N, N′,N″,‐tris (methylenephosphonic acid) would be an increasingly effective contrast agent above ∼ 10 MHz if the oligomerization was stable in vivo (and the Gd3+ ions were sufficiently well bound). At lower fields, the relaxivity of these small chelate complexes is dominated by τso, the relaxation time of the spin moments of the paramagnetic ions. We find this to be favorably long for complexes of Gd3+ with the macrocyclic phosphonate ligands, as was found earlier by us for Gd( DOTA)−. This situation, ostensibly related to the relatively high symmetry and rigidity of the macrocyclic complexes, can increase the low‐field relaxivity of the phosphonates almost a factor of 2 beyond that of Gd(DTPA)2−. © 1989 Academic Press, Inc.
Increased rf power absorption in MR imaging due to rf coupling between body coil and surface coil
Authors: Buchli R. , Saner M. , Meier D. , Boskamp E. B. , Boesiger P.
Published: March 2007

Fears have been voiced that excessive tissue heating could occur in the event that first, a surface coil is placed with its axis parallel to the transmitting rffield leading to a maximal coupling of the two coils and second, the decoupling circuit of the surface coil breaks down. To avoid an rf coupling of the transmitting body coil to the receive‐only surface coil, conventionally applied surface coils are equipped with an active electronic rf decoupling circuit. In extensive worst‐case experiments on phantoms we have shown that no tissue heating occurs for surface coils which are equipped with semiconductor varicap diodes for tuning and matching. These coils should be safe for patient applications even if the decoupling circuit fails. Surface coils equipped with mechanically variable capacitors are generally passively decoupled. To simulate the worst‐case situation phantom experiments were performed in which a surface coil of this type having no passive decoupling circuit was coupled to the transmitter coil by its geometric position. Theoretical calculations, in agreement with the experimental results achieved during a 15‐min measurement in a 1.5‐T MRI whole‐body imager, show that a significant rfpower deposition in the tissue underneath the coil wire occurs, leading typically to a local specific absorption rate of 24 W /kg and a local temperature rise of 52°C. © 1989 Academic Press, Inc.
Multiple short‐echo (2.5‐ms) quantitation of in vivo sodium T2 relaxation
Authors: Perman William H. , Thomasson David M. , Bernstein Matt A. , Turski Patrick A.
Published: March 2007

The MR behavior of the sodium‐23 nucleus in vivo is a complex problem which has generated considerable interest over the last 20 years. Early studies on excised tissue samples revealed that the sodium nucleus exhibited a two‐component T2 relaxation. This biexponential T2 relaxation was characterized by a short component with a T2=0.7–4.8 ms, and a long component with a T2=7.0−26.0 ms. We have developed a 3D pulse sequence capable of performing multiple Hahn echo in vivo sodium‐23 imaging at echo times as short as 2.5 ms. This sequence obtains the shorter spin echo times by presaturating the spins outside of the desired imaging region, allowing the use of nonselective rf pulses. Using this sequence we have been able to quantify the long and short T2 components of normal brain tissue, vitreous humor of the eye, and a rabbit VX‐2 carcinoma. We found that gray matter and white matter of normal brain have a monoexponential T2 relaxation with T2=17.6 ± 2.4 ms. The vitreous humor T2 relaxation is also monoex‐ ponential with T2=56.8 ± 2.1 ms. However, we find that some of the rabbit VX2 carcinomas exhibit a biexponential T2 decay with a short component of 3.3 ± 4.6 ms and a long component of 22.0 ± 9.0 ms. © 1989 Academic Press, Inc.
A quantitative study of relaxation rate enhancement produced by iron oxide particles in polyacrylamide gels and tissue
Authors: Majumdar S. , Zoghbi S. , Pope C. F. , Gore J. C.
Published: March 2007

The proton relaxation rate enhancements produced by two types of iron oxide particles, M4125 and AM125 (Advanced Magnetics, Cambridge, MA) designed as potential MR contrast agents, have been measured in polyacrylamide gels and in liver and spleen. The organ uptakes, time courses, and biodistributions of these materials have been measured using radiolabeling. The relaxation rate enhancements produced by these particles have been related to the concentration of iron per gram material at different magnetic field strengths. The relaxation rates increase linearly as a function of concentration at field strengths varying from 0.15 to 7 T. The relaxation effects of these particles in tissue are significantly different from the behavior in vitro. These results suggest that several different mechanisms contribute to relaxation effects in the presence of iron oxide particles and they depend strongly on the way the particles are sequestered. Diffusion effects for a specified TE may be enhanced using gradient or single‐spin echoes rather than multiple echoes. AMI25 is significantly more effective as a relaxation agent than paramagnetic metal ions only at relatively high fields, while M4125 is less effective per unit concentration. © 1989 Academic Press, Inc.