bluuebunny/crossref_metadata_2025 huggingface dataset:
MR fluoroscopy: Technical feasibility
Authors: Riederer Stephen J. , Tasciyan Talin , Farzaneh Farhad , Lee James N. , Wright Ronald C. , Herfkens Robert J.
Published: March 2007

A method of magnetic resonance image acquisition and reconstruction is described in which high imaging rates and fast reconstruction times are allowed. The acquisition is a modification of the basic FLASH sequence but with a restricted number N of phase encodings. The encodings are applied sequentially, periodically, and continuously. Images are formed by sliding a window of width N encodings along the acquired data and reconstructing an image for each position of the window. In general the acquisition time per image exceeds the time between successive images, and the method thus has a temporal lag. Experimental studies were performed with a dynamic phantom using 48 phase encodings and a TR of 20 ms, for an image acquisition time of about 1 s. The image display rate in the reconstructed sequence was 12.5 images/s, and the image sequence portrayed the motion of the phantom. Additional studies were done with 24 encodings. It is shown how the sliding window technique lends itself to high‐speed reconstruction, with each newly acquired echo used to quickly update the image on display. The combination of the acquisition technique described and a hardware implementation of the reconstruction algorithm can result in realtime MR image acquisition and reconstruction. © 1988 Academic Press, Inc.
Integrated volume‐selective/spectral editing 1H NMR and postdetection signal processing for the sensitive determination of lactate
Authors: Knüttel A. , Rommel E. , Clausen M. , Kimmich R.
Published: March 2007

A new volume selection/spectral editing pulse sequence (VOSING) is presented. The features specific to the technique are that the volume selection and the editing intervals coincide and that no decoupling is necessary. The pulse sequence can be applied under both homo‐ and heteronuclear conditions. Phantom experiments with lactate solutions and human serum led to water suppression factors of about 20,000. A postdetection signal processing method has been implemented. The final sensitivity for lactate determinations could thus be improved by a factor of more than 4. Ischemia‐induced lactate could easily be detected in serum. At present, the lower detection limit of lactate is 1 mmol/liter for a(1.2cm)3 voxel and 32 scans in a 4.7‐T/40‐cmmagnet. © 1988 Academic Press, Inc.
Proton relaxation times in cancer diagnosis
Authors: Mariappan S. V. Santhana , Subramanian S. , Chandrakumar N. , Rajalakshmi K. R. , Sukumaran S. S.
Published: March 2007

Proton nuclear magnetic resonance relaxation parameters ( T1,T2) were measured for over 100 malignant and normal tissue samples of various organs of the human body. The purpose ofthis study was to estimate the reliability ofthe NMR technique in discriminating normal from malignant tissues. Breast and cervix samples were analyzed by using the malignancy index concept and we were able to distinguish malignant and normal tissue in 17 out of 18 breast samples and 5 out of 7 cervix samples. Since the relaxation data of a normal control population ofthe other organs were not available, the data for these are reported without any further analysis. The distinction between carcinomas and sarcomas was also made by using the estimated relaxation parameters. Malignancy indices of breast tissue samples for linear least‐squares and nonlinear two‐parameter and three‐parameter least‐squares procedures were calculated and used to evaluate the relative efficiencies in discriminating malignant from normal tissues. © 1988 Academic Press, Inc.
Elimination of transverse coherences in FLASH MRI
Authors: Crawley Adrian P. , Wood Michael L. , Henkelman R. Mark
Published: March 2007

Fast low‐angle shot (FLASH) imaging enables TI‐weighted scans to be acquired in a few seconds. However, the diagnostic image quality is severely compromised by the appearance of artifactual bands parallel to the frequency encode direction. We show that the band structure arises from differences in the ability of the phase encode gradient to spoil transverse coherences that build up between successive repetition intervals. A theoretical understanding of the mechanisms involved leads to a comparison between various methods of spoiling the unwanted echoes throughout the whole field of view. Spoiler gradients whose amplitudes change linearly with phase encode step number are treated in detail. The theory predicts that the spoilers will rotate and rescale the band structure and these results are confirmed experimentally. The effect of the spoilers at a given location along the gradient is equivalent to the effect on the entire field of view of an incremented phase shift applied to the radiofrequency pulse. An appropriate rf phase shift scheme should therefore provide ideal spoiling characteristics for FLASH imaging. © 1988 Academic Press, Inc.
Longitudinal proton relaxation rates in rabbit tissues after intravenous injection of free and chelated Mn2+
Authors: Spiller Marga , Brown Rodney D. , Koenig Seymour H. , Wolf Gerald L.
Published: March 2007

The factors that determine the field‐dependent increase in 1/T1 of tissue water protons were investigated for MnCl2, and Mn2+ (PDTA) (1, 3‐propylenediamine‐N,N′,N″,N‴‐tet‐ raacetic acid) introduced intravenously into rabbits. Mn2+ was used in preference to other paramagnetic ions in part because of the distinct NMRD profiles (magnetic field dependence of 1/T1) of free Mn2+ ions, their small chelate complexes, and their macromolecular conjugates, and in part because the relatively low toxicity of Mn2+ is favorable for animal studies. Tissue content of Mn2+ was determined in all samples by inductively coupled plasma analyses; the state of Mn2+ in excised tissues was determined from the form of the 1/T1 NMRD profile of water protons; and distribution of contrast agent within tissue and access of water on a T1 time scale were determined by double‐exponential analyses of proton relaxation behavior in intact doped tissue, as well as by the change of single‐exponential relaxation rates and proton signal intensity upon gentle disruption ofthe tissue. MnCl2 is found in all tissues, except fat and skeletal muscle, but liver is most avid at low dose, and Mn2+ accumulates in spleen after high doses. Chelation targets Mn2+ to liver and kidney, saturating the liver chemically at relatively low dose. We suggest that pronounced increase in tissue relaxivity results from irrotationally bound Mn2+, ostensibly associated with the polar head groups of cell membranes. Compartmentalization of contrast agent and restricted diffusion of tissue water influences the maximum relaxation rates attainable, so that there is an optimal dose of these contrast agents which is rather low. © 1988 Academic Press, Inc.
Dextran‐magnetite: A contrast agent for sodium‐23 MRI
Authors: Summers Ronald M. , Joseph Peter M. , Renshaw Perry F. , Kundel Harold L.
Published: March 2007

Dextran‐magnetite, a superparamagnetic compound, is a powerful relaxation reagent for sodium. Administered intravenously, it is confined mainly to the vasculature and eliminates the signal from plasma sodium, a significant component of the tissue sodium signal. Applications ofdextran‐magnetite for in vivo sodium imaging ofa normal rat and rats with a tumor and experimentally induced peripheral edema are shown. Our results indicate that dextran‐magnetite may be useful for improving tumor detection and for imaging of edema. To our knowledge, this is the first report of a contrast agent suitable for sodium magnetic resonance imaging. © 1988 Academic Press, Inc.
High‐resolution 1H NMR spectroscopy in the diagnosis of breast cancer
Authors: Bradamante Silvia , Barchiesi Emma , Pilotti Silvana , Borasi Giovanni
Published: March 2007

Surgical specimens from 22 patients with infiltrating ductal carcinoma of the breast were analyzed by high‐resolution 1H NMR spectroscopy at 80 and 300 MHz. Results were compared with those obtained from 9 benign (proliferative dysplasia without atypia) breast samples. NMR spectra at 80 MHz showed well‐resolved water and lipid peaks so it was possible to calculate specific T1 and T2 relaxation times. The longitudinal T1, relaxation process of the water was found to be properly represented by a monoexponential function, whereas the transverse T2 decay was well accounted for by a biexponential model. Relaxation time measurements of the water were found to be a valuable tool in breast tissue characterization, in particular (a) mean T1, values from malignant and control populations are well distinguished (P < 0.0008): (b) mean T2, values of both fast and slow components from the two populations are statistically different (P < 0.0001) and no overlap exists in the distributions of the second component. Three‐hundred‐meg‐ ahertz spectra allowed a detailed analysis of the lipidic component of the sample: malignant tumors were found to present in the region 1.3–1.2 ppm a species characterized by a very slow transverse relaxation time ( T2 = 200–1000 ms). © 1988 Academic Press, Inc.
1HNMR studies on human plasma lipids from newborn infants, healthy adults, and adults with tumors
Authors: Eskelinen S. , Hiltunen Y. , Jokisaari J. , Virtanen S. , Kiviniittys K.
Published: March 2007

The 1HNMR spectra of the lipid region of human plasma from healthy adults, neonates, and patients with malignant and nonmalignant tumors have been recorded on a JNM‐GX400 FT spectrometer operating at 399.6 MHz for protons. The chemical shifts of methylene and methyl groups of plasma lipids were measured with respect to the higher field component of the methyl proton resonance of the lactate molecule. The results show that there are changes in the chemical shifts of the methylene proton resonances among the plasma from healthy adults, adults with tumors, and neonates. The shifts observed in the case of cancer patients and neonates are in the direction opposite to the shift measured from the plasma of healthy adults. Thus, the observed changes cannot be explained by the activity in the cell proliferation of tissues which is high in the cases of both healthy neonates and patients with malignant tumors, but they most probably reflect the different lipoprotein compositions of neonates, healthy adults, and adults with tumors. © 1989 Academic Press, Inc.
The unequivocal determination of lactic acid using a one‐ dimensional zero‐quantum coherence‐transfer technique
Authors: Doddrell David M. , Brereton Ian M. , Moxon Leith N. , Galloway Graham J.
Published: March 2007

A method based on zero‐quantum coherence transfer for spectral editing of metabolites in aqueous solution in a one‐dimensional experiment is described. Water suppression factors of approximately 8000 were achieved by the use of pulsed B0 field gradients and excellent editing was obtained in a single acquisition. The methyl resonances of both lactate and acetaldehyde were readily observed in a mouse brain homogenate by generat‐ ing zero‐quantum coherence using Gaussian pulses for selective excitation of the respective CH resonances. © 1989 Academic Press, Inc.
In vivo proton nuclear magnetic resonance imaging and spectroscopy studies of halocarbon‐induced liver damage
Authors: Brauer Manfred , Towner Rheal A. , Renaud Ian , Janzen Edward G. , Foxall David L.
Published: March 2007

Proton magnetic resonance imaging and localized NMR spectroscopy were used to study the rat liver in situ. Respiratory gating was used in both the imaging and the localized spectroscopy studies to control for the movement of the upper abdomen of the rat during breathing. After administration of carbon tetrachloride, bromotrichloromethane, or halothane, localized regions of high proton signal intensity were observed in the NMR images of the liver. Localized (VOSY) proton NMR spectra from within these regions indicated that the increase in a signal intensity was due to a longer T2 relaxation time for the water resonance, indicating acute edema in the region of tissue damage. © 1989 Academic Press, Inc.
Unified multiple‐feature color display for MR images
Authors: Kamman R. L. , Stomp G. P. , Berendsen H. J. C.
Published: March 2007

A display method is proposed in which the spin‐lattice relaxation time T1, the spinspin relaxation time T2, and the proton density ρ of each pixel in a MR image are simultaneously expressed in color features in a unified way that allows international standardization. MR images were made from a phantom, a healthy volunteer, and patients in such a way that T1 and T2 and proton density images could be derived. T1 and T2 data were compared with accurate relaxation time measurements of the phantom content. Color images were computed from the acquired T1 and T2 images using matrix multiplication on a pixel base. In this way the color combination in each pixel represents the properties of that particular pixel by a unique mixing of the elementary colors red, green, and blue. Color resolution could be modified using different choices of the reference triangle in which the color combinations were defined. This method of representation offers a means for displaying multiple features as T1, and T2 in one directly interpretable image, independent of instrumental settings. © 1989 Academic Press, Inc.
A fuse for magnetic resonance imaging probes
Authors: Hedges L. Kyle
Published: March 2007

In a research environment, a magnetic resonance imaging system's manufacturer‐supplied protection against excessive rf power deposition in the sample is often compromised. This paper presents a widely applicable scheme, based on a commonly available fuse, that simply and effectively limits the average rf power into a magnetic resonance imaging probe. © 1989 Academic Press, Inc.
31P NMR bayesian spectral analysis of rat brain in vivo
Authors: Bretthorst G. Larry , Kotyk John J. , Ackerman Joseph J. H.
Published: March 2007

Bayesian spectrum analysis for parameter estimation is a rigorous statistical (non‐ Fourier‐based) method. Herein the Bayesian quadrature NMR model is introduced and applied to analysis of 31P NMR time domain data from in vivo rat brain. Immunity to both the brain spectrum “baseline hump” and the phase twist is demonstrated. © 1989 Academic Press, Inc.
Computer simulation of MRS localization techniques: An analysis of ISIS
Authors: Lawry T. J. , Karczmar G. S. , Weiner M. W. , Matson G. B.
Published: March 2007

Computer simulations were used to evaluate the ISIS localization technique as implemented with both head and surface coils. The effects ofchemical shift, B1 inhomogeneity, repetition time, T2 relaxation, a postacquisition saturation pulse, and a B1 insensitive observation pulse were examined. Integrals of ISIS signals over the sample volume showed that significant signal loss from the volume of interest (VOI) and contamination from outside the VOI can occur for both head and surface coil ISIS experiments. The results showed that the saturation pulse, order of the various ISIS acquisitions, and repetition time affect contamination but not signal loss. In addition, short T2 and high RF power can combine synergistically to degrade the selective inversion pulses, causing further contamination and signal loss. © 1989 Academic Press, Inc.
The use of band‐selectable digital filtering in magnetic resonance image enhancement
Authors: Mitchell D. K. , Nichols S. T. , Smith M. R. , Scott K.
Published: March 2007

Manipulation of the data describing two‐dimensional magnetic resonance (MR) images can be used to zoom an image, decrease image noise and artifacts by modeling, or emphasize object edges in the field of view. In this paper, a two‐dimensional band‐selectable digital filtering (2D‐BSDF) technique is detailed. This can be used to decrease the computational burden and increase algorithm stability associated with such data manipulation. Many display devices have the ability of expanding an image by pixel or linear interpolation. Application of the efficient zooming fast Fourier transformation algorithms provides a superior quality sinc‐function interpolated image. In 2D‐BSDF, the ideal rectangular windows used in sinc‐function interpolation are replaced by windows with a more gradual roll‐off. This gradual roll‐off results in a slight degradation of the image edges but substantially reduces the computation time. Modeling of MRI data has been attempted to remove noise and artifacts from the image. These algorithms are computationally expensive and frequently unstable because of the high model orders required. The 2D‐BSDF can be used to prepare a reduced data set, without loss ofinformation. A lower order model may be applied to the subset and computation times approaching that required for normal fast Fourier transform algorithms result. The absence of noise and signal from objects outside the region of interest can considerably enhance the stability of the modeling algorithms. The use of BSDF is equally applicable when used in association with the modeling of 2D NMR spectroscopy data or with edge enhancement or any other data manipulation of magnetic resonance imaging images. In this paper an explanation of ID‐BSDF is provided and an algorithm for 2D‐BSDF is developed. A comparison of filter designs and computational times is given when applying the technique to zooming and modeling of MR images. Images from medical MRI data are provided. © 1989 Academic Press, Inc.
Magnetic resonance imaging using a ribbonator: Hand and wrist
Authors: Marshall Eric A. , Listinsky Jay J. , Ceckler Toni L. , Szumowski Jerzy , Bryant Robert G. , Hornak Joseph P.
Published: March 2007

A modified version of a single‐turn solenoid with rectangular symmetry, which we call a ribbonator, provides excellent magnetic resonance images of the hand and wrist when used as both the transmitter and the receiver in a 1.5‐T clinical imaging system. The very high RF efficiency provides excellent signal‐to‐noise and anatomical resolution. Design equations and RF properties of the resonator are discussed. © 1989 Academic Press, Inc.
Hybrid methods of chemical‐shift imaging
Authors: Szumowski Jerzy , Eisen Jane K. , Vinitski Simon , Haake Peter W. , Plewes Donald B.
Published: March 2007

We propose a family of hybrid chemical‐shift sequences which combines two physical principles for water/lipid separation to minimize artifacts introduced by B0 and B1 inho‐mogeneities. Hybrid sequences provide improved species discrimination over earlier methods without resorting to postprocessing while maintaining a multislice/multiecho capability. © 1989 Academic Press, Inc.
Variable excitation angle AFP pulses
Authors: Norris David G. , Haase Axel
Published: March 2007

RF pulses employing the principle of adiabatic fast passage are finding increasing application with surface coils. A small modification to existing AFP pulses that allows the excitation angle to be chosen largely independently of B1 strength is described here. Rapid 3D imaging applications of such pulses are presented. © 1989 Academic Press, Inc.
Interleaved 31P NMR with transcutaneous nerve stimulation (tns): a method of monitoring compliance‐independent skeletal muscle metabolic response to exercise
Authors: Helpern J. A. , Kao W. , Gross B. , Kensora T. G. , Welch K. M. A.
Published: March 2007

31P NMR spectroscopy was used to monitor the metabolic response of the tibialis anterior muscle group to transcutaneous nerve stimulation of the peroneal nerve at a rate of 4 Hz for 5 min in human volunteers (n = 8). It is demonstrated that this technique can be used as a method of investigating effort‐free and compensation‐independent skeletal muscle exercise. © 1989 Academic Press, Inc.
A perfusion system developed for 31p NMR study of melanoma cells at tissue‐like density
Authors: Minichiello Margaret M. , Albert Daniel M. , Kolodny Nancy H. , Lee Moon‐Soo , Craft Joseph L.
Published: March 2007

A perfusion culture system has been developed for 31P NMR study of human uveal melanoma metabolism by adapting the Vitafiber I cartridge system (Amicon). 31P NMR spectra collected weekly during periods of up to 10 weeks demonstrated increasing levels of phosphorus metabolites as the anchorage‐dependent cells grew to tissue‐like density. © 1989 Academic Press, Inc.
The influence of pulse sequence on the relaxation effects of superparamagnetic iron oxide contrast agents
Authors: Majumdar S. , Zoghbi S. S. , Gore J. C.
Published: March 2007

The effects of different pulse sequences and timing parameters on the increase in transverse relaxation rate produced by superparamagnetic iron oxide particles have been studied. Gradient‐echo, single spin‐echo, and multiple‐echo images recorded at 2.0 T were used to evaluate the reduction in signal intensity per unit concentration of iron oxide for different echo times and in different media. For the same echo time, gradient‐echo sequences were found to be more than twice as sensitive to the effects of the agent as single spin‐echo imaging sequences, while multiple‐echo sequences were much less affected than either. Using measurements of the relative effects on different sequences, the contributions of different relaxation mechanisms have been quantified. © 1989 Academic Press, Inc.
Bone marrow uptake of liposome‐entrapped spin label after liver blockade with empty liposomes
Authors: Federico Massimo , Iannone Anna , Chan Hsiao C. , Magin Richard L.
Published: March 2007

Using an ESR spectrometer, we studied the time course of the uptake of the liposomeentrapped spin label 2,2,6,6‐tetramethylpipendine‐N‐oxyl‐4‐tnmethylammonium in liver, spleen, and bone marrow following reticuloendothelial liver blockade. Our results show that suppression of the phagocytic activity of the liver increases the delivery of liposomes to the spleen and bone marrow without substantially altering uptake by the liver. © 1989 Academic PITS, Inc. © 1989 Academic Press, Inc.
Evaluation of a newly discovered water suppression pulse sequence for high‐field in vivo1H surface coil NMR spectroscopy
Authors: Alger J. R. , Brunetti A. , Nagashima G. , Hossmann K.‐A.
Published: March 2007

The use of a water‐suppressing spin‐echo pulse sequence reported recently (V. Sklenar and A. Bax, J. Magn. Reson. 74, 469 (1987); M. von Kienlin, M. DeCorps, J. P. Albrand, M. F. Foray, and P. Blondet, J. Magn. Reson. 76, 169 (1987)) was evaluated for in vivo brain proton surface coil NMR spectroscopy. The studies were performed on cat brain using surface coils at 4.7 T. The sequence produced brain spectra with adequate water suppression, and a broader excitation profile than sequences which form spin echoes using 1331 pulses (P. J. Hore, J. Magn. Reson. 54, 539 (1983); H. P. Hetherington, M. J. Avison, and R. G. Shulman, Proc. Natl. Acad. Sci. USA 82, 3115 (1985)). The phase artifacts were smaller than those produced in 1331 methods, but theoretical analysis showed they should not be completely absent. The effectiveness of lengthening the spin‐echo delay in the new sequence for suppression of unwanted lipid resonances was demon‐strated. The sequence was shown to be capable of detecting lactate formation and clearance in a global cerebral ischemia experiment. © 1989 Academic WSS, Inc.
Androgen sensitivity of rat prostate carcinoma studied by 31P NMR spectroscopy, 1H MR imaging, and 23Na MR imaging
Authors: Vigneron D. B. , Hricak H. , James T. L. , Jajodia P. B. , Nunes L. , Narayans P.
Published: March 2007

31P NMR spectroscopy, 1H magnetic resonance (MR) imaging, and 23Na MR imaging were used to study the biochemical difference between nine hormone‐sensitive and six hormone‐resistant rat prostate cancers and to follow bioenergetic and morphologic changes subsequent to androgen deprivation in the hormone‐sensitive model. Neither 1H nor 23Na MR image characteristics were useful in distinguishing androgen‐sensitive from androgen‐resistant prostate cancer nor in identifying androgen deprivation. 31P NMR spectroscopy did detect bioenergetic differences between the hormone‐sensitive and hormone‐resistant tumors. Baseline spectra showed a significantly higher PCr/ATP ratio (mean 0.86 ± 0.09 SEM) for hormone‐sensitive tumors than for hormone‐resistant tumors (mean 0.26 ± 0.07 SEM). By 3 days after androgen deprivation (orchiectomy (castration)), PCr/ATP ratios had decreased noticeably; by 1 week, the decrease was statistically significant and remained so for the rest of the study (3 weeks). It appears that 31P NMR spectroscopy is useful in detecting androgen sensitivity of prostatic carcinoma. © 1989 Academic Press, Inc.
1H NMR studies of urine from premature and sick babies
Authors: Brown Judith C. C. , Mills Graham A. , Sadler Peter J. , Walker Valerie
Published: March 2007

High‐frequency proton nuclear magnetic resonance (1H NMR) has been applied to a study of urine from premature and sick newborn babies with a variety of clinical disorders. These included severe birth asphyxia, necrotizing enterocolitis, ketosis, and drug treatment. Abnormal levels of metabolites such as lactate, ketone bodies, betaine, dicarboxylic acids, and 4‐hydroxyphenolic acids were detected, as was the antibiotic metronidazole and one of its metabolites. The assignment of betaine was confirmed by two dimensional 1H NMR studies of urine obtained from two adults with homocystinuria receiving treatment with oral betaine. High‐resolution 1H NMR spectroscopy of urine is a potentially useful research technique for monitoring metabolism during early life.
Transrectal probe for 1H MRI and 31P MR spectroscopy of the prostate gland
Authors: Narayan Perinchery , Vigneron Daniel B. , Jajodia Prahalad , Anderson Charles M. , Hedgcock Marcus W. , Tanagho Emil A. , James Thomas L.
Published: March 2007

A transrectal probe for 1H imaging and 31P MR spectroscopy of the prostate gland is described. The probe is covered with plastic and consists of an insertional portion containing an rf coil and a handle containing a tuning and matching circuit. Using this transrectal probe, 1H MR images and the first 31P MR spectra of the in situ canine prostate were obtained. Serial alterations in prostate size and changes in the ratio of phosphomonoesters to ATP ratio following orchiectomy were observed. Transrectal images of the prostate appear to be superior to conventional whole body coil images in the canine. For the first time a device to obtain high signal‐to‐noise 1H images and 31P spectra of the in situ prostate has been constructed. This will allow the assessment oftransrectal imaging and spctroscopy as tools for medical studies of prostate pathophysiology.
Imaging tumors with respect to a grid coordinate system by proton magnetic resonance using lipid suppression and T2 weighting
Authors: Block Ronald E. , Parekh Barbara C.
Published: March 2007

Experimental tumors can be located with respect to a grid coordinate system by using lipid‐suppressed T2‐weighted proton imaging with thick coronal slices and a plexiglass grid containing a solution of paramagnetic ions. Most normal tissues except the brain. eyes, and CNS are essentially transparent under these conditions, allowing thick sections to be rapidly searched for tumors. Use of this approach to monitor tumor growth is demonstrated.
1H image‐guided localized 31P MR spectroscopy of human brain: Quantitative analysis of 31P MR spectra measured on volunteers and on intracranial tumor patients
Authors: Segebarth Christoph M. , Balériaux Danielle F. , De Beer Ron , Van Ormondt Dirk , Mariën Ad , Luyten Peter R. , Den Hollanders Jan A.
Published: March 2007

1H image‐guided 31P MR spectra of normal human brain and of intracranial tumors have been analyzed quantitatively. Tumor types examined include prolactinoma, lymphoma, and various grade gliomas. The experimental signals were processed by means of a time‐domain least‐square fitting procedure, which yields the spectral parameters, as well as a prediction of the standard deviations. Significant spectral variations are observed within both populations of normal brain and of intracranial tumor 31P MR spectra. The metabolic ratios derived from the glioma 31P MR spectra and from corresponding unin‐filtrated brain tissue do not differ significantly. Significant differences are, however, observed between the metabolic ratios of prolactinoma and uninfiltrated tissue 31P MR spectra. Alkaline pH values are found for the prolactinoma and the high‐grade gliomas. Furthermore. spectral differences are observed between the patient' uninfiltrated tissue 31P MR spectra and those of an unmatched population of volunteers. This underscores the necessity for control measurements on the uninfiltrated tissue of the patient and for controls from a matched population of healthy individuals.
Localized volume selection technique using an additional radial gradient coil
Authors: Lee S. Y. , Cho Z. H.
Published: March 2007

A volume selection technique for the localized NMR imaging using an additional radial gradient is proposed. This volume selection gradient is the fourth gradient in addition to the usual 3‐dimensional imaging gradients, i.e., x‐, y‐, and z‐directional gradients, and is of the radial form. The principle of the proposed method is the use of the radial gradient in conjunction with the selective RF pulse thereby selecting a small cylindrical volume which can be used for the 3‐dimensional volume imaging with fewer encoding steps than those of the conventional full 3‐dimensional volume imaging. The present technique combined with the fast steady state free precession gradient echo imaging sequence allows us to reduce the total scan time to several minutes for the 3‐dimensional volume imaging with the spatial resolution of 1 X 1 X 1 mm or to spend the same scan time for the 3‐dimensional imaging with improved spatial resolution. The basic principle of the radial gradient coil consisting of a main circular loop coil and an offset compensating Helmholtz coil is discussed and the construction details are presented. Some experimental results of the proposed volume selection imaging technique as well as computer simulation results are also given. © 1989 Academic Press, Inc.
Multiple‐output chemical shift imaging (MOCSI): A practical technique for rapid spectroscopic imaging
Authors: Twieg D. B.
Published: March 2007

A new technique for rapid multiple‐frame chemical shift imaging and localized spectroscopy is reported. Unlike phase‐encoding techniques and multiple‐delay chemical shift imaging techniques, this technique permits spectroscopic imaging at high spatial resolution and moderately high spectral resolution with acquisition times as short as 10 min or less. Unlike other rapid spectroscopic imaging techniques which have been reported, it uses cyclic trapezoidal gradient waveforms achievable in standard clinical magnetic resonance imaging systems. Multiple‐output chemical shift imaging images and spectra from a human study are shown. © 1989 Academic Press, Inc.
Monoclonal antibody‐coated magnetite particles as contrast agents in magnetic resonance imaging of tumors
Authors: Cerdan Sebastian , Lötscher Hans Ruedi , Künnecke Basil , Seelig Joachim
Published: March 2007

A highly specific and powerful magnetic resonance imaging contrast agent has been prepared by coating magnetite (Fe3 O4) particles with monoclonal antibodies directed against a tumor antigen. The preparation maintains both the immunoreactivity of the monoclonal antibody and the full relaxing capability of the magnetite particle. MRI image contrast by spin‐echo methods can be easily induced in a concentration range of 1–10 nM of the antibody‐coated magnetite particles. © 1989 Academic Press, Inc.
Erythrocyte Na+/K+ ATPase activity measured with 23Na NMR
Authors: Ouwerkerk Ronald , Echteld Cees J. A. Van , Staal Gerard E. J. , Rijksen Gert
Published: March 2007

A 23Na NMR assay for measurement of erythrocyte Na+/K+ ATPase activity is presented. Using the nonpermeant shift reagent dysprosium tripolyphosphate the signals of intra‐ and extracellular sodium are separated, enabling measurement of sodium fluxes nondestructively, without the need to physically separate the cells from their environment. By increasing membrane permeability with nystatin we have shown that the assay allows the detection of differences in membrane permeability. With low doses of nystatin the ouabain‐sensitive sodium flux increased more than twofold. With high doses of nystatin the Na+/K+ pump could not prevent an almost total equilibration of intra‐ and extracellular sodium. All sodium that entered the cells remained NMR visible, proving that sodium influx can be measured quantitatively. 31P NMR spectra taken before and after the assay revealed a slight acidification of the cells and no significant change in ATP concentration. No evidence of Dy3+ entering the cell was observed. © 1989 Academic Press, Inc.
The use of an improved inversion pulse with the Spin‐Echo/ inversion‐recovery sequence to give increased accuracy and reduced imaging time for T1 measurements
Authors: Gowland P. A. , Leach M. O. , Sharp J. C.
Published: March 2007

The hyperbolic secant inversion pulse has been incorporated into the interleaved saturation‐recovery/inversion‐recovery sequence to provide T1 measurements combining high precision with a significantly reduced imaging time (a mean accuracy of 2% over a T1 range of 300 to 1650 ms for standard gel phantoms, with Tr1 = Tr2 = 2.0 s, Ti = 0.67 s). © 1989 Academic Press, Inc.
An incubation system for the NMR study of kidney tubules
Authors: Ammann H. , Boulanger Y. , Legault P. , Vinay P.
Published: March 2007

Isolated kidney cortical tubules require a very rapid oxygen supply and mechanical agitation to be optimally functional. A sample chamber in which a tubule suspension is oxygenated by recirculating oxygen gas inside a coil of dialysis fibers to avoid cell loss through bubbling and in which the tubules are agitated by a gas‐driven turbine has been designed. In such a system, dog cortical tubules (35‐45 mg/ml) were found to be metabolically stable for more than 3 h as indicated by linear lactate consumption and glucose production. Small pH variations resulting from carbon dioxide and bicarbonate productions were measured. Good‐quality 23Na NMR spectra of dog kidney cortical tubules were recorded with such a system, allowing a I‐min time resolution.

The authors are particularly grateful to Mr. Michel Brunette, Groupe de Recherche en Transport Membranaire, for the construction of the NMR chamber. The technical assistance of Mrs. Pierrette Fournel, Mr. Jacques Sénécal, and Mrs. Josette Noël is gratefully acknowledged. This project was supported by the Kidney Foundation of Canada and the Medical Research Council of Canada. H.A. is the recipient of a Medical Research Council studentship. Y.B. is chercheur‐boursier of the Fonds de la Recherche en Santé du Québec. © 1989 Academic Press, Inc.
A comparison of three radiofrequency coils for NMR studies of conductive samples
Authors: Murphy Marilee K. , Frnandez Erik J. , Clark Douglas S.
Published: March 2007

Three rf coil designs of equal volume (approximately 15 ml) were compared using conductive samples. Magnetic loss into the sample was the dominant noise source. At physiological conductivity the sensitivity of the horizontally aligned solenoid and loop‐gap resonator was only 1.3 ± 0.2 times that of the vertically aligned slotted tube resonator. © 1989 Academic Press, Inc.
Extraction of cardiac and respiratory motion cycles by use of projection data and its applications to nmr imaging
Authors: Kim W. S. , Mun C. W. , Kim D. J. , Cho Z. H.
Published: March 2007

A technique of extracting cardiac and respiratory motion cycles by use of projection data is proposed and studied. These extracted cardiac and respiratory motion cycles are applied to the cine imaging of heart and motion artifact reduction in abdominal imaging instead of the conventional ECG gating devices. The basic concepts and their applications are discussed, Experimental results on human volunteers obtained with the KAIS 2.0‐T whole‐body NMR imaging system together with the pulse sequences used for the experiments are presented.
Detection of metabolic heterogeneity of human intracranial tumors in vivo by 1h nmr spectroscopic imaging
Authors: Segebarth Christoph M. , Balériaux Danielle F. , Luyten Peter R. , Den Hollander Jan A.
Published: March 2007

Patients with intracranial tumors (gliomas) were examined by means of localized water‐suppressed 1H NMR single volume spectroscopy and spectroscopic imaging. The 1H NMR spectra of the tumors exhibit signal intensities of the N‐acetyl aspartate, choline compounds, and creatine plus phosphocreatine resonance lines that are different from the corresponding intensities observed on normal brain tissue. Also, for 6 out of the 10 patients examined so far, lactate resonance lines were detected in the tumor spectra. For one patient, abnormal 1H NMR spectra were obtained of a hemisphere which appeared normal with 1H NMR imaging. Metabolic heterogeneity of the tumorous regions could be demonstrated with 1H NMR spectroscopic imaging, using a spatial resolution in the order of 1 cm. These results suggest a spectrum of metabolic observations that may ultimately provide an important means for characterizing brain tumors.
Comparison of 31p mrs and 1h mri at 1.5 and 2.0 T
Authors: Boska M. D. , Hubesch B. , Meyerhoff D. J. , Twieg D. B. , Karczmar G. S. , Matson G. B. , Weiner M. W.
Published: March 2007

The goals of this study were to compare 31P magnetic resonance spectroscopy (MRS) and 1H magnetic resonance imaging (MRI) of human subjects and phantoms at 1.5 and 2.0 T. The 31P signal‐to‐noise (S/N) ratios in phantom standards and in localized volumes in human brain and liver were compared at 1.5 and 2.0 T. In addition, T1 values for 31P resonances in human brain, 31P linewidths of metabolites in human brain and liver, 1H S/N in a phantom standard, and MR image quality in human head and body were compared at the two field strengths. The results of our study showed that at the higher strength field, (1) in vivo 31P MRS studies benefited from up to 32% improvement in S/N; (2) in vivo 31P MRS studies also benefited from increased spectral dispersion; (3) the quality of MR head images remained comparable; and (4) body images showed some decrease in image quality due to increased chemical shift, and flow and motion artifacts.
Numerical analysis of multislice mr excitation and inversion with multifrequency selective rf pulses
Authors: Hafner Hans‐Peter , Müler Stephan , Seelig Joachim
Published: March 2007

Multifrequency selective excitation and inversion were recently described and tested for multislice imaging and multivolume selective spectroscopy (Magn. Reson. Med. 6, 364 (1988), J. Magn. Reson. 76, 155 (1988)). The technique is based on the assumption that a multifrequency rf pulse, a linear superposition of several selective rf pulses with different frequencies, generates a MR signal which can be separated into the spin responses due to each individual frequency. This assumption is investigated theoretically by analyzing the effect of multifrequency selective rf pulses on the magnetization of a homogeneous phantom as a function of slice separation, pulse shape, and rf amplitude using computer simulations of the Bloch equations. It is found that multifrequency selective excitation with sinc pulses–up to eight slices are investigated–and two‐frequency inversion with hyperbolic secant pulses lead to profiles comparable in quality and selectivity to those of conventional single‐frequency pulses.
Triple‐quantum‐coherence‐filtered imaging of sodium ions in vivo at 4.7 tesla
Authors: Griffey Richard H. , Griffey Beatrice V. , Matwiyoff Nicholas A.
Published: March 2007

The tissue distribution of sodium ions which generate triple‐quantum coherence (TQC) in vivo is determined from images. A technique for filtering conventional sodium images, so that signal is obtained only from sodium ions which have a correlation time appropriate for producing TQC, is described. The utility of TQC‐filtered sodium images is demonstrated in a study of tumors implanted in a nude rat model, where the intensity of the TQC signal from sodium ions in the growing margin of the tumor is observed to be 200‐250% greater than that from surrounding tissue.
Quality: quantification improvement by converting lineshapes to the lorentzian type
Authors: De Graaf A. A. , Van Dijk J. E. , BoéE W. M. M. J.
Published: March 2007

A method of time domain deconvolution, QUALITY, is described for general use in quantitative NMR spectroscopy. By division of the experimental NMR time domain signal by a reference signal, which may be obtained either in a separate experiment or via inverse Fourier transformation of an isolated single resonance in the experimental spectrum, perfect Lorentzian lineshapes can be obtained regardless of the magnetic field inhomogeneity. Experiments, both in vivo using a surface coil and in vitro using a surface coil and a HR NMR probe, show excellent performance of the method.
Switched array coils
Authors: Requardt H. , Offermann J. , Erhard P.
Published: March 2007

Switched array coils (SACs) are a useful tool in local coil imaging since they allow in a user‐friendly manner one to make the best choice in the trade‐off between field of view and signal‐to‐noise ratio. This is done by selecting the current path within a conductor array equipped with suitable switches. Since the switching can be controlled by the system, this allows changing of the coil dimensions within multislice sequences. Thus image quality can be improved due to smaller coil dimensions for a given slice and a larger area can be covered by electronically shifting this sensitive area. The principle can be applied to surface–as Well as volume–coil designs. © 1990 Academic Press, Inc.
In situ assessment of tumor vascularity using fluorine nmr imaging
Authors: Ceckler Toni L. , Gibson Scott L. , Hilf Russell , Bryant Robert G.
Published: March 2007

In situ fluorine NMR imaging has been used to measure vascularity in subcutancously implanted mammary tumors. Oxyferol, a perfluorinated blood substitute comprised of an emulsion of 25% w/v perfluorotributylamine, was used as a tracer. Following iv administration, this perfluorocarbon emulsion remains primarily in the vasculature during the image acquisition period. The distribution of the PFTA in the 19F NMR image gives a map of tissue regions with intact vascularity. This technique has been used to demonstrate decreased blood flow in necrotic regions of R3230AC mammary tumors in which vasculature had been damaged either as a result of spontaneous necrosis or by photodynamic therapy (PDT). Damage to tumor vascularity following PDT was observed prior to the development of necrosis.
Multinuclear nmr investigations of probe construction materials at 4.7 t
Authors: Babcock E. E. , Vaughan J. T. , Lesan And B. , , Nunnally R. L.
Published: March 2007

Since background signal from NMR probes can overwhelm the signal from a sample, the NMR analysis of plastics or machinable ceramics is a prerequisite to their use in probe implementations. The contributions from a variety of materials to proton, fluorine, and carbon NMR spectra are presented.
Signal loss induced by superparamagnetic iron oxide particle in NMR spin‐echo images: The role of diffusion
Authors: Rozenman Yoseph , Zou Xueming , Kantor Howard L.
Published: March 2007

MR contrast agents are used to improve the detectability of pathologic conditions. In this study we clarify the mechanism of action of a newly developed superparamagnetic agent (AMI‐25, Advanced Magnetics Inc., Cambridge, MA). Transverse relaxation rates were measured from segments of rat brain, heart, and liver using a CPMG pulse sequence. Relaxation rates varied with the time interval between the refocusing pulses in the sequence ( τ)The diffusion effect on signal intensity was quantitated from the variation of T2with τ. We find that diffusion in the presence of microscopic field gradients reduces T2 and that this effect differs in magnitude among tissues. Superparamagnetic iron oxide particles enhance this T2reduction. The dependence of T2upon τ suggests a model of restricted diffusion. Tissue image contrast induced by superparamagnetic iron oxide in spin‐echo NMR studies is the result of a combination of diffusion‐dependent and diffusion‐independent differences in transverse relaxation. © 1990 Academic Press, Inc.
Perfusion imaging with NMR contrast agents
Authors: Rosen Bruce R. , Belliveau John W. , Vevea James M. , Brady Thomas J.
Published: March 2007

Knowledge of regional hemodynamics has widespread application for both physiological research and clinical assessment. Here we review the use of MR contrast agents to measure tissue perfusion. Two primary mechanisms of image contrast are discussed: relaxivity and susceptibility effects. Relaxivity effects result from dipolar enhancement of T1 and T2 rates. Because tissue T1 rates are intrinsically smaller, the dominant effect is shortening of T1 relaxation times. The second mechanism of image contrast is the variation in tissue magnetic field produced by heterogeneous distribution of high magnetic susceptibility agents. Quantitation of tissue perfusion requires a detailed understanding of the relation between contrast agent concentration and associated MR signal changes. Studies to date show a linear relationship between contrast agent concentration and rate change in most organs. The exact nature of this relationship in the dynamic setting of rapid contrast agent passage through the microcirculatory bed is less well established. If this relationship is known, tracer kinetic modeling can be used to calculate regional blood flow and blood volume. Data are presented which indicate that this approach is feasible, and suggest the potential of contrast‐enhanced NMR for high resolution in vivo mapping of both physiology and anatomy. © 1990 Academic Press, Inc.
A 1‐year time course study of the relaxation times and histology for irradiated rat lungs
Authors: Shioya Sumie , Haida T Munetaka , Fukuzaki Minoru , Ono Yoshiaki , Tsuda Masayuki , Ohta Yasuyo , Yamabayashi Hajime
Published: March 2007

To investigate the NMR relaxation times for irradiated rat lung tissue, we measured T1, and T2 at 11 different times during the injury's 1‐year time course. A biexponential analysis of T2 was used to determine T2 fast (T2f) and T2 slow (T2s). In addition, we measured water content and correlated changes in the relaxation times with pathological changes. The correlation indicates the following: (1) Shortly after irradiation, the biexponential T2 decay for 1/3 of the samples became monoexponential and there were no noticeable pathological changes observed using light microscopy. (2) During radiation pneumonitis, T2f and T2s were prolonged. This accompanied acute edematous changes and inflammatory cell infiltration. (3) Finally, during radiation fibrosis T1 shortened and collagen increased. We observed no significant correlation between relaxation time changes and water content changes throughout the 1‐year time course. © 1990 Academic Press, Inc.
Magnetic resonance imaging of experimental demyelinating lesions
Authors: Ford Corey C. , Ceckler Toni L. , Karp Juliana , Herndon Robert M.
Published: March 2007

An animal model of central nervous system demyelination was created by injecting rat internal capsules with lysophosphatidylcholine (LPC). The resulting chemically induced demyelinating lesions were readily visible in T1 ‐weighted spin‐echo, T2 weighted spin‐echo, and inversion‐recovery magnetic resonance imaging (MRI) sequences. Changes in lesions were followed over 8 weeks and correlated with histopathology. Histologically, lesions were characterized initially by an acute, inflammatory phase with edema and blood‐brain barrier breakdown, followed by macrophage‐mediated removal of myelin debris and finally by remyelination after 3 to 4 weeks. MRI can differentiate lesion stages in the LPC model and may be useful in investigating mechanistic aspects of the demyelinating process. In addition the well‐localized lesions may be amenable to study by techniques of volume‐localized NMR Spectroscopy. © 1990 Academic Press, Inc.