bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo nmr diffusion spectroscopy: 31p application to phosphorus metabolites in muscle
Authors: Moonen Chrit T. W. , Van Zijl Peter C. M. , Bihan Denis Le , Despres Daryl
Published: March 2007

Apparent diffusion coefficients (Da) of individual metabolites can be studied in vivo by diffusion NMR spectroscopy using an echo sequence sensitized to molecular motion. The methods are based on the echo attenuation due to phase dispersion resulting from incoherent displacement during the diffusion time. As the displacement of metabolites by diffusion in vivo can be affected by compartment size, temperature, adsorption processes, etc., the presented methods are potentially useful in studying such phenomena in vivo. Here, the methods are applied to phosphocreatine in the rat quadriceps muscle. It is demonstrated that the displacement of phosphocreatine resembles free diffusion for short diffusion times but becomes limited as a result of boundaries due to compartmenta‐tion for longer diffusion times. The limit of the displacement indicates an apparent average size of 44 pm of the compartment in the direction of the diffusion gradient. As the gradient was applied approximately parallel (angle i 25o) to the muscle fiber, this result indicates that phosphocreatine moves freely in the cytosol but is limited by the boundaries of the muscle cells. Error analyses are performed with regard to motion artifacts and gradient performance. The methods were tested extensively for distilled water and free metabolites. © 1990 Academic Press, Inc.
Use of gel filtration in the preparation of biological fluids for magnetic resonance spectroscopy
Authors: Hoffman David W. , Venters Ronald A. , Shedd Suzanne F. , Spicer Leonard D.
Published: March 2007

Analysis of biological fluids by proton magnetic resonance spectroscopy is often complicated by dynamic range problems created from the large water resonance. Gel filtration chromatography is found to be a simple and nondestructive method for exchanging D2O for H2O and for removing low molecular weight molecules from both plasma and urine, significantly improving subsequent one‐ and two‐dimensional MRS spectra.
Proton magnetic resonance spectroscopy of human brain in vivo in the evaluation of multiple sclerosis: Assessment of the load of disease
Authors: Arnold Douglas L. , Matthews Paul M. , Francis Gordon , Antel Jack
Published: March 2007

Image localized, water‐suppressed proton magnetic resonance spectra were obtained from affected brain in patients with multiple sclerosis. In patients with moderate to severe chronic disease, spectra revealed a decreased ratio of N‐acetylaspartate to creatine resonance intensities. A normal ratio was obtained from a large recently symptomatic MRI plaque that resolved without sequelae. We propose that the observed metabolite changes can be useful as an index of irreversible CNS injury. © 1990 Academic Press, Inc.
Quantification of regional blood flow by monitoring of exogenous tracer via nuclear magnetic resonance spectroscopy
Authors: Kim Seong‐Gi , Ackerman Joseph J. H.
Published: March 2007

Deuterium and fluorine nuclear magnetic resonance spectroscopy have been employed for quantification of regional blood flow in concert with nonradiative, exogenous, freely diffusible tracers such as D2O and freon gas. Typically, the tracer residue washout was monitored by NMR over time following tracer administration by bolus injection or inhalation. The theory, including compartmental analysis, required to quantitatively derive volumetric tissue blood flow and perfusion is reviewed herein. Applications of NMR tissue blood flow measurement techniques to tumor, muscle, liver, and brain are presented with discussion of the advantages and disadvantages of NMR methods. © 1990 Academic Press, Inc.
Carotid‐CNS MR flow imaging
Authors: Masaryk Thomas J. , Laub Gerhard A. , Modic Michael T. , Ross Jeffrey S. , Haacke E. Mark
Published: March 2007

The authors present their 1‐year experience with the use of 3DFT, time‐of‐flight MR angiography for the evaluation of vascular diseases of the head and neck. Their experience with over 150 patients indicates that this examination may be performed in conjunction with standard spin‐echo imaging with only a minimal increase in patient examination time. This combined examination is most applicable to atherosclerotic disease of the carotid bifurcation, arterial occlusions of the primary and secondary branches of the intracranial circulation (particularly in pediatric patients such as those following ECMO or with sickle cell anemia), and patients with saccular berry aneurysms. This type of static, angiographic technique adds little to standard spin‐echo imaging in patients with arteriovenous fistulae, neoplasms, and giant intracranial aneurysms. Limitations of the present technique include the inability to visualize slow flow lesions (e.g., giant aneurysms) and selected high flow states (arteriovenous fistulae, some severe stenoses ). © 1990 Academic Press, Inc.
pH standardization for phosphorus‐31 magnetic resonance heart spectroscopy at different temperatures
Authors: Kost Gerald J.
Published: March 2007

Intracellular pH typically is measured by NMR using the calibrated chemical shift of the inorganic phosphate peak in phosphorus‐31 spectra. Heart Spectroscopy experiments often require measurements of intracellular pH at temperatures from 5 to 37°C. This paper provides NMR pH calibrations for this range of temperatures, a summary of calibration data reported to date, and a discussion of the factors influencing pH Standardization. © 1990 Academic Press, Inc.
Spectral editing of tumor 13C MRS in Situ
Authors: Xue Min , Ng Thian C. , Majors Anthony
Published: March 2007

The editing pulse sequence DEPT (D. T. Pegg, D. M. Doddrell, and M. R. Bendall, J Chem. Phys. 77, 2745 (1982)) was modified using a scheme of various composite pulses and a 16‐step phase cycling to obtain proton‐decoupled natural‐abundance 13C edited subspectra of solid tumors. A solenoidal probe including a Faraday shield and an orthogonal saddle decoupling coil was built for this purpose. © 1990 Academic Press, Inc.
Projection images of the position‐velocity joint spin density distribution
Authors: Xiang Q. S. , Nalcioglu O.
Published: March 2007

A new concept of phase encoding called position‐velocity combined oblique Fourier phase encoding is introduced. It encodes both spatial and velocity information in a single oblique direction in the position‐velocity space. Using this method, two‐dimensional projection images of the three‐dimensional position‐velocity joint spin density distribution along different directions can be obtained. These projection images can provide detailed information on the flow system under study. The imaging of the two‐dimensional projection is less time consuming compared to three‐dimensional Fourier flow imaging and can be easily implemented on a conventional magnetic resonance imaging scannner. © 1990 Academic Press, Inc.
An apparatus for applying a mechanical massage to rat hearts inside a wide‐bore NMR spectrometer
Authors: Kushnir Tammar , Schwalb Herzl , Yaroslavsky Esther , Borman Joseph B. , Uretzky Gideon , Navon Gil
Published: March 2007

A device for applying mechanical massage to the isolated perfused rat heart inside a wide‐bore NMR spectrometer was developed. This device exerts a squeezing pressure on a fibrillating heart placed inside a NMR spectrometer without interfering with the NMR measurements. It appears that the apparatus is important for obtaining reliable results in the postischemic reperfusion period. © 1990 Academic Press, Inc.
Cooperative T1 and T2 effects on contrast using a new driven inversion spin‐echo (DISE) MRI pulse sequence
Authors: Conturo Thomas E. , Kessler Robert M. , Beth Albert H.
Published: March 2007

A pulse sequence is presented for obtaining a single image with combined T1/T2 weighting. T2 relaxation is made to increase intensity, in cooperation with the effect of T1 relaxation, by providing T2 weighting with a 90°‐180°‐90° driven inversion pulse triplet in an inversion recovery method. Unlike the inversion spin‐echo method having a short inversion time (TI), signals in the new driven inversion spin‐echo (DISE) method need not be negative and the most T1‐sensitive region of the recovery curve can be used. Selecting sensitivity to one relaxation time does not degrade the sensitivity to the other relaxation time. T1 sensitivity is thus extended to longer echo times (TE intervals), T2 sensitivity is extended to longer TI intervals, and the combined Tl / T2‐weighted technique with intermediate TE and T1 has highly cooperative and near‐maximal T1 and T2 effects on contrast. Intensity is not multiplicatively degraded by T1 and T2weighting so that the signal‐to‐noise of the combined T1/T2 ‐weighted method is high. High intensity and TI and T2 cooperatively occur for a much wider range of relaxation times, and especially for images heavily weighted to the pathologic intermediate and long T1 and T2 Rgime. © 1990 Academic Press, Inc.
NMR visibility of 39K and 35Cl in erythrocytes and kidney tubules
Authors: Boulanger Y. , Vinay P.
Published: March 2007

The NMR visibility of 39K and 35Cl has been investigated in erythrocytes and in dog renal tubules. In erythrocytes, the 39K NMR visibility was determined by comparing the signal intensities before and after hemolysis with water and by comparing the NMR and flame photometry results. Both procedures showed a NMR visibility of 100% for intracellular potassium. The visibility of intracellular chloride in erythrocytes was estimated at 40% by monitoring the intensity of the35Cl signal as a function of the hematocrit value. In the case of kidney proximal tubules, the 39K visibility appeared to be very low but could not he accurately determined due to the low sensitivity of the nucleus. The 35Cl signals for intracellular chloride in renal tubules were too broad to be detected. © 1990 Academic Press, Inc.
Spatial mapping of 23Na NMR signals by two‐dimensional rotating frame imaging
Authors: Boehmer John P. , Metz Kenneth R. , Mao Jintong , Briggs Richard W.
Published: March 2007

The reconstruction of two‐dimensional spatial images with 0.5‐mm resolution using radio frequency gradients generated by an NMR coil system rotated about the sample is demonstrated for 23Na. The method retains chemical shift, should be capable of mapping T1 and T2 information, and might offer sensitivity advantages for nuclides with short T2. © 1990 Academic Press, Inc.
Analysis of diabetic cataractogenesis using chemical‐shift nuclear magnetic resonance microscopy
Authors: Cheng Hong‐Ming , Aguayo James B. , Moore Gregory J. , Mattingly Mark
Published: March 2007

We here report the analysis of single rabbit lenses under high‐glucose stress using four‐dimensional 13C nuclear magnetic resonance (NMR) spectroscopy (three spatial and one chemical‐shift). We have produced spatial maps of lenticular metabolites (glucose, sorbitol, and lactate) with submillimeter in‐plane resolution. The production of sorbitol and its inhibition are also presented. This is the first study to report regional tissue metabolism. We expect further improvements in spatial resolution and acquisition times that will enable localized kinetic studies in intact tissues. © 1991 Academic Press, Inc.
19F nuclear magnetic resonance imaging of drug distribution in vivo: The disposition of an antifolate anticancer drug in mice
Authors: Maxwell R. J. , Frenkiel T. A. , Newell D. R. , Bauer C. , Griffiths J. R.
Published: March 2007

The application of 19F nuclear magnetic resonance imaging to the study of drug distribution in vivo is discussed. CB3988 (C2‐desamino‐C2‐methyl‐N 10‐propargyl‐2′‐trifluoromethyl‐5,8‐dideazafolic acid) is a fluorinated representative of a class of quinazoline an‐tifolates which act as inhibitors of thymidylate synthase and which are being evaluated for the treatment of human cancer. 19 F images were obtained in vivo from the abdomen of mice following intravenous injection of CB3988 (500 mg/kg). Time resolutions of 4 and 20 min were achieved for two‐ and three‐dimensional imaging, respectively. These images were consistent with the presence of high concentrations of drug (up to 26 mg/ml) in the gall bladder, urinary bladder, and small intestine, as confirmed ex vivo by extraction and HPLC analysis. The results indicate the potential value of 19F NMR imaging in pharmacokinetic Studies. © 1991 Academic Press, Inc.
Multisite Saturation transfer using DANTE and continuous wave
Authors: Clark Joseph F. , Harris Gale I. , Dillon Patrick F.
Published: March 2007

The DANTE pulse sequence was modified to produce selective resonance saturation similar to that produced by the continuous wave (CW) technique. A combined DANTE and CW saturation technique can be used to perform multisite saturation transfer experiments because of the similar saturation produced by the two techniques. © 1991 Academic Press, Inc.
In Vivo Brain Water Determination by T1 Measurements: Effect of Total Water Content, Hydration Fraction, and Field Strength
Authors: Fatouros P. P. , Marmarou A. , Kraft K. A. , Inao S. , Schwarz F. P.
Published: March 2007

This work is concerned with the accurate quantification of brain water content under routine clinical conditions. Gelatin solutions of varying water content are first employed as a model of an edematous brain and longitudinal relaxation measurements are performed at proton Larmor frequencies of 5, 41, 63, and 100 MHz. These are followed with in vivo measurements in an experimental animal model of brain edema at 41 MHz. The results underscore the dominant role of total water content Win the relaxation process and verify the expected linearity between 1/T1 and 1/W. A scheme is presented and experimentally verified at 41 MHz for deducing the exact relationship of 1/T1 vs 1/W at any frequency. Knowledge of this relationship along with precise measurements of 1/T1 at a given field strength permits quantitative in vivo measures of brain water content to be obtained with a precision of about 0.01. It is concluded that routine, accurate, and noninvasive brain water measurements are possible by magnetic resonance imaging in a clinical environment. © 1991 Academic Press, Inc.
Hepatic transport of the magnetic resonance imaging contrast agent Fe(III)‐N‐(3‐Phenylglutaryl)desferrioxamine B
Authors: Hoener Betty‐Ann , Tzika A. Aria , Englestad Barry L. , White David L.
Published: March 2007

We have studied the hepatic transport of Fe(III)‐N‐(3‐phenylglutaryl)desferrioxamine B (Fe‐PGDF). Using 59Fe‐PGDF in biliary cannulated rats we have shown that 32 ± 2% of an iv bolus dose was excreted into the bile. In animals pretreated with a saturating dose of taurocholate, oxyphenonium, or bromosulfophthalein (BSP), 25 ± 6%, 23 ± 1%, or 1.6 ± 0.8% of the dose, respectively, was excreted into the bile. Magnetic resonance images indicated that BSP blocked uptake of Fe‐PGDF by the hepatocytes. Possible enterohepatic recycling of 59Fe‐PGDF was investigated in linked rat experiments. All of the material excreted into the bile of the donor, 28 ± 10% of the dose, was recovered in the gastrointestinal tract of the recipient, but none was found in its bile or urine. These results suggested that uptake of Fe‐PGDF by the hepatocytes occurred via the BSP transporter and that no enterohepatic recycling of the contrast agent occurred. © 1991 Academic Press, Inc.
A reduced power selective adiabatic spin‐echo pulse sequence
Authors: Conolly Steven , Glover Gary , Nishimura Dwight , Macovski Albert
Published: March 2007

We introduce a selective adiabatic pulse sequence suitable for generating selective spin‐echoes for both MR imaging and spectroscopy. The technique is simple; one uses the echo generated by any pair of identical selective adiabatic inversion pulses. The nonlinear phase across the slice is compensated perfectly by the second π pulse. This compensation is immune to RF inhomogeneity and nonlinearity. For imaging applications, we concentrate on a reduced‐power version of the pulse sequence in which time is traded off variably for RF amplitude in the presence of a time‐varying gradient. This technique, known as variable‐rate excitation, mildly degrades the off‐resonant slice profile when applied to amplitude‐modulated pulses. We present theoretical explanations and experimental results that show that the variable‐rate adiabatic pulses are immune to off‐resonant degradation of the magnitude normally encountered in MR imaging. © 1991 Academic Press. Inc.
Comparison of human polymorphonuclear leukocytes from peripheral blood and purulent exudates by high resolution 1H MRS
Authors: May George L. , Sztelma Krystyna , Sorrell Tania C. , Mountford Carolyn E.
Published: March 2007

Human pus samples from various sites, including soft tissue and pleural cavity, as well as sputum from patients with cystic fibrosis have been analyzed by 1H magnetic resonance spectroscopy (MRS) and found to generate high resolution spectra. Assignments have been made for neutral lipid, amino acids, taurine, and lactate. Human peripheral blood polymorphonuclear leukocytes have also been examined and a similar spectrum containing these lipid and metabolite resonances was detected in cells stimulated with lipopolysaccharide. In unstimulated cells, only resonances from taurine and lactate were observed, suggesting that the presence of the lipid and metabolite resonances is an indicator of cellular activation of polymorphonuclear leukocytes. This is the first report of 1H MRS applied to intact human polymorphonuclear leukocytes and extends available documentation as to which types of normal and/or diseased tissue contain MR visible molecules. © 1991 Academic Press, Inc.
Diffusion of water in tissues and MRI
Authors: Hazlewood U. F. , Rorschach H. E. , Lin C.
Published: March 2007

The purpose of this paper is to present an overview of the diffusive behavior of water in biological tissues. The analysis shows that obstructive barriers would have to occupy very large volume fractions in order to account for the reduction in the diffusion coefficient (D) observed in biological systems. Generally, most models lead to the supposition that a substantial fraction (20–40%) of the cell water is hydration water, or that the diffusion coefficient of the cytoplasmic water is reduced substantially from the free water value. Thus, the conclusion that a substantial fraction of cell water has diffusive properties that are altered by the macromolecules of the cytoplasm seems inescapable. The impact of these findings on MRI remain to be determined. © 1991 Academic Press, Inc.
Analytical solution and verification of diffusion effect in SSFP
Authors: Carney C. E. , Wong S. T. S. , Patz S.
Published: March 2007

Assuming that the SSFP magnetization response maintains a steady state which is penodic in the presence of diffusion, we can solve for the diffusion effect in such sequences. Formulating a Fourier series decomposition solution to the Bloch‐Torrey equation and imposing the steady‐state condition, analytical expressions describing the signal decay due to diffusion are developed. Magnetization responses for any system and sequence parameters can then be obtained. Also, sensitivity to b factor changes is quite different than standard diffusion measurement techniques. Assumptions made in the solution are verified via finite difference solutions and simulations of the Bloch‐Torrey equation.
Studies of restricted diffusion in heterogeneous media containing variations in susceptibility
Authors: Zhong Jianhui , Gore John C.
Published: March 2007

Measurements of water self‐diffusion in heterogeneous media by pulsed gradient spin‐echo methods depend on the precise choice of experimental parameters. This variation may reflect the presence of restricted or anisotropic diffusion, or the presence of intrinsic magnetic field gradients. In experiments at 2.0 T, restricted diffusion effects have been demonstrated in freshly excised tissues with an effective barrier radius of order 10 μm. In samples with intrinsic susceptibility variations such as tissues or gels containing dispersions of iron oxide particles, the reduction of apparent diffusion coefficient with diffusion interval can be used to estimate the degree of heterogeneity of the magnetic field in the sample. The implications of these effects for diffusion‐weighted MRI as well as their use to derive novel tissue parameters are discussed. © 1991 Academic Press, Inc.
Noninvasive temperature imaging using diffusion MRI
Authors: Delannoy J. , Chen Ching‐Nien , Turner R. , Levin R. L. , Le Bihan D.
Published: March 2007

Efficacy and safety considerations for cancer therapy with hyperthermia require accurate temperature measurements throughout the heated volume. We report the use of molecular diffusion, whose temperature dependence is well known. A dedicated hyperthermia applicator was built, combining a MRI gradient coil and a rf coil. Diffusion and derived temperature images were obtained with a 1 × 2 mm pixel size on a polyacrylamide gel phantom using a clinical 1.5‐T whole body MRI system. Temperatures determined from these images using 1 cm2 regions of interest were found to be within 0.2° of those recorded from the thermocouples and fiber‐optic probes placed inside the gel. © 1991 Academic Press, Inc.
Improvement of spectral resolution in shift‐reagent‐aided 23Na NMR spectroscopy in the isolated perfused rat heart system
Authors: Miller Sandra K. , Chu Wen‐Jang , Pohost Gerald M. , Elgavish Gabriel A.
Published: March 2007

The level of intracellular sodium (Nai) is maintained at approximately 14 m M in healthy myocytes. When myocytes are damaged, Nai increases and therefore the level of Nai may be a means of evaluating myocardial cell integrity. A particularly useful method to monitor Nai levels is 23Na NMR spectroscopy. However, because of the isochronous nature of the extracellular sodium (Nao) and Nai NMR signals, paramagnetic lanthanide shift reagents (LSR), such as dysprosium triphosphate, Dy(PPP)72, have been used to shift the Nao signal. This reveals the unshifted Nai signal and allows the NMR monitoring of Nai in isolated perfused hearts and other systems. A major shortcoming of this method (the “shift‐only” method) is in the need to minimize the Nao signal by not submerging the perfused hearts in Na+‐containing buffer. An equally undesirable alternative is the utilization of relatively high concentrations of LSR to shift a large Nao signal sufficiently to enable reasonable resolution and quantitation of Nai. We present here a method, the “shiftrelaxation” method, which is a combination of using a mixture of Dy(PPP)72, a shift reagent, and gadolinium triphosphate, Gd(PPP)72, a relaxation agent, with data acquisition using an inversion‐recovery (IR) pulse sequence. This combination allows differentiation between Nao and Nai by the difference in their respective T1 values in addition to the shift between them. With this technique we can selectively minimize the extracellular signal and therefore minimize the need for a large Dy‐induced shift, as well as allow data acquisition on a heart submerged in Na+ ‐containing perfusate. The resulting improved discrimination between Nai and Nao at relatively low levels of LSR should be helpful for ultimate in vivo application and potential clinical applications, where a lower dose of LSR also means a decreased possibility of physiologically deleterious effects. Also included in this paper is a method for the quick determination of an accurate 180° pulse which is required for the optimization of the IR method. © 1991 Academic Press, Inc.
Magnetic resonance imaging of the efficacy of specific inhibition of 5α‐reductase in canine spontaneous benign prostatic hyperplasia
Authors: Cohen S. M. , Taber K. H. , Malatesta P. F. , Shpungin J. , Berman C. , Carlin J. R. , Werrmann J. G. , Prahalada S. , Bryan R. N. , Cordes E. H.
Published: March 2007

A leading role for prostatic levels of dihydrotestosterone (DHT) in the pathogenesis of benign prostatic hyperplasia is well established, if incompletely understood. The present study provides initial confirmation that 5α‐reductase inhibition alone is sufficient to prevent prostatic accumulation of DHT and to produce epithelial regression in the canine prostate. In dogs treated with the specific 5α‐reductase inhibitor finasteride, prostatic volume decreased to one‐third of the baseline volume, while the prostatic concentration of DHT fell fivefold: both were constant in placebo control dogs. Demonstration that MR imaging can serve as an accurate modality to assess prostatic volume was provided by serial measurements of the canine prostate and by correlation of the last imaging measurement with the weight of the excised prostate. Significant intensity changes were observed in T2‐weighted images measured post‐treatment; these changes correlated with the histopathology of the prostate. These results suggest that beyond quantifying regression, multiecho T2 measurements can be useful in probing accompanying changes occurring on the cellular level. © 1991 Academic Press, Inc.
The stability of proton T2 effects of oxygen‐17 water in experimental cerebral ischemia
Authors: Hopkins A. L. , Lust W. D. , Haacke E. M. , Wielopolski P. , Barr R. G. , Bratton C. B.
Published: March 2007

The gerbil model of unilateral cerebral ischemia has been used to test the temporal and spatial stability of the MRI T2 effects of oxygen‐17 water. Following unilateral carotid ligation, symptomatic animals were given a single large intraperitoneal injection of H2 17O and the distribution and stability of the brain T2 effects were followed with a spin‐echo sequence. In contrast to the ischemic areas, the perfused tissue shows a marked and prolonged loss in intensity with little evidence of diffusion of the T2 effect of 17O into the ischemic tissue. © 1991 Academic Press, Inc.
The magnetic properties of some materials affecting MR images
Authors: Josephson Lee , Bigler Jeffrey , White David
Published: March 2007

We have compared the magnetic properties of various types of materials known to affect MR images. The materials compared were: (i) MR contrast agents based on chelates of paramagnetic metals (Gd‐DTPA, Dy‐DTPA); (ii) biological forms of iron (horse spleen ferritin and deoxyhemoglobin); and (iii) a superparamagnetic iron oxide (AMI‐25). The properties compared were the magnetic susceptibility and the magnetization. The magnetization and susceptibility of superparamagnetic AMI‐25 are far larger than that of ferritin or low molecular weight, paramagnetic chelates. Superparamagnetic iron oxide colloids, like AMI‐25, are a uniquely powerful class of magnetic materials. © 1991 Academic Press, Inc.
The dependence of proton longitudinal and transvese relaxation times on cell‐cycle phase: Mouse MCA‐transformed 10T½ 5 TCL‐15 cells
Authors: Belfi Charles A. , Medendorp Sharon V. , Ngo Frank Q. H.
Published: March 2007

Attempts to determine proton NMR tongitudinal relaxation times (T1) as a function of cell‐cycle stage using cells synchronized by chemical methods have yielded conficting results (P. T. Beall, C. F. Hazlewood, and P. N. Rao), Science 192, 904 (1976); R. N. Muller et al., FEBS Lett. 114, 231 (1980); D. N. Wheatley, et al., J. Cell. Sci. 88, 13 (1987). This has raised the question whether a truc dependence of T1 on cell‐cycle phase exists. In the present study, the centrifugal elutriation technique was used to obtain relatively pure, synchronized cell populations of TCL‐15 cells (a methylcholanthrene‐transformed line of mouse 10T 5 cells) for measurement of proton NMR relaxation rates. This tecnique provides a means to procure synchronized cell populations without the use of chemical agents as in the above‐cited investigations and therefore avoid possible effects caused by the chemical agents on the NMR relaxations processes. Both T1 and the transverse relaxation time, T2, of water protons in synchronized‐cell pellets obtained in this study, exhibited a dependence on cell‐cycle phase at least for the first half of the cell cycle (G1 to S). Cells in G1 phase exhibited quantitatively higher T1 and T2 relaxation times compared to those measured for cells in mid S phase. Such changes were found to correlate with changes in water content. The distribution of cell‐cycle phases of each cell population was determined by the DNA histogram using flow cytometric methods. Possible relaxation mechanisms which may contribute to the cell‐cycle‐specific phenomena of the intracellular T1 and T2 times are discussed. © 1991 Academic Press, Inc.
On the nature and reduction of the displacement artifact in flow images
Authors: Nishimura Dwight G. , Jackson John I. , Pauly John M.
Published: March 2007

In flow‐imaging experiments with 2‐D Fourier transform sequences, the time difference between phase encoding and readout leads to a potentially misleading displacement artifact. This artifact arises in regions of rapid flow and high shear, and manifests as an intensity distortiion in additton to a bulk shift. We have studied methods of mitigating the artifact, including offset‐echo acquisition, backward‐evolving phase encoding, moment‐compensated phase encoding, and projection‐reconstruction imaging. Experiments on flow phantoms verified the nature and reduction of this displacement artifact. Of the four methods studied, the projection‐reconstruction sequence proved to be the most effective, completely eliminating the artifact. © 1991 Academic Press, Inc.
In vivo sodium chemical shift imaging
Authors: Kohler Susan. J. , Kolodny Nancy H. , Celi Ann C. , Burr Tracey A. , Weinberg David , D'amico Donald J. , Gragoudas Evangelos S.
Published: March 2007

The shift reagents thulium(III) 1,4,7,10‐tetraazacyclododecane N, N′, N″, N‴ tetramethylenephosphonate (TmDOTPS5−), and dysprosium(III) triethylenetetraminehexaacetate (DyTTHA3−) are compared in this work for their uses in sodium chemical shift imaging (NaCSI). In a series of experiments using phantoms we evaluated the relative contributions of bulk magnetic susceptibility (BMS) effects and hyperfine shifts to the induced 23Na chemical shift for these two shift reagents. The ratios of BMS effects to hyperfine shifts suggest that TmDOTP5− should be a more effective shift reagent than DyTTHA3− for 23Na NMR spectroscopy as well as NaCSI. The dependence on pH and free Ca2+ concentration of the 23Na NMR frequency shift induced by TmDOTP5− was evaluated. It was found that TmDOTP5− produces good spectral resolution under physiologic conditions. Examples presented from in vivo NaCSI experiments using TmDOTP5− to study diffusion in the posterior chamber of the rabbit eye and to monitor the rate of clearance of aqueous fluid from the anterior chamber demonstrate the effectiveness of this new shift reagent and of the NaCSI technique for in vivo studies. © 1992 Academic Press, Inc.
Noise correlations exist for independent RF coils
Authors: Harpen Michael D.
Published: March 2007

It is shown that contrary to the contention of Jesmanowicz et al. (Magn. Reson. Med. 20, 36, 1991), noise voltages from coupled magnetic resonance imaging coils may exhibit cross correlation. © 1992 Academic Press, Inc.
A new two‐dimensional phase unwrapping algorithm for MRI images
Authors: Hedley Mark , Rosenfeld Dov
Published: March 2007

The phase of an image obtained with many magnetic resonance imaging techniques is related to some physical variable of interest. This phase needs to be unwrapped, which is complicated by the presence of noise and multiple objects of irregular shape. A new two‐dimensional phase unwrapping algorithm is presented, along with simulation results. © 1992 Academic Press, Inc.
Cardiac cycle extraction from projection data using static signal suppression
Authors: Kim W. S. , Cho Z. H.
Published: March 2007

As an extension of the projection‐data‐based cardiac cycle extraction that we developed previously (W. S. Kim, K. J. Jung, K. D. Lee, J. B. Ra, and Z. H. Cho, “Proceedings, Seventh Annual Meeting of the Society of Magnetic Resonance in Medicine, 1988”, p. 958; W. S. Kim, C. W. Mun, D. J. Kim, and Z. H. Cho, Magn. Reson. Med. 13, 25, 1990), a new technique with which one can extract the cardiac cycle by flow‐based projection data measurements is described. Because the method uses flow‐dependent projection data, it is possible to obtain the cardiac cycle even from regions such as the head, which has virtually no geometrically varying parts, unlike the cardiac region. The signal‐to‐noise of this flow (such as blood and CSF) based projection data acquisition is further enhanced by the use of the static sample signal suppression technique developed for angiography (J. H. Kim and Z. H. Cho, Magn. Reson. Med. 14, 554, 1990). © 1992 Academic Press, Inc.
Brain maturation and response to anoxia: 31P NMR spectroscopic studies in rat pups
Authors: Suzuki Nobuyuki , Kwee Ingrid L. , Nakada Tsutomu
Published: March 2007

The differential effects of systemic anoxia on the immature rat brain in two postnatal developmental age groups, group I (1–2 days postnatal) and group II (9—10 days postnatal), were studied utilizing phosphorus‐31 nuclear magnetic resonance spectroscopy. While all pups in group I survived the 15‐min anoxic period, only half of the pups in group II survived. Brain adenosine triphosphate and intracellular pH of pups in group I remained essentially unchanged throughout the anoxic period, while phosphocreatine and inorganic phosphate were sensitive indicators of anoxia. These parameters were all more drastically affected in group II pups than in group I pups. Group II pups also exhibited a significant increase in phosphomonoester, indicating developmental differences in phospholipid metabolism. © 1992 Academic Press, Inc.
Slice thickness reduction by partial overlapping presaturation
Authors: Matsuda Tetsuya , Doyle Mark , Pohost Gerald M.
Published: March 2007

We present a new approach to slice thickness reduction that does not require strengthening the selection gradient or increasing the RF pulse duration. The basis of the approach is to employ a thick slice and suppress a portion of its width, thereby forming a thin slice. Two distinct implementations of the technique are introduced and demonstrated by imaging slice profiles in a phantom and generating images of a volunteer's knee. © 1992 Academic Press, Inc.
Contribution of cytoplasmic polypeptides to the 1H NMR spectrum of developing rat cerebral cortex
Authors: Kauppinen Risto A. , Palvimo Jorma
Published: March 2007

In the present study the contribution of cytoplasmic polypeptides thymosins β4 and β10 to the 1H NMR spectrum during the maturation of the rat cerebral cortex was assessed. In the proton spectrum intense broad peaks at 0.9, 1.22, and 1.40 ppm from thymosins decreased in size relative to the signal at 2.02 ppm in parallel to the reciprocal increase in the concentration of N‐acetyl aspartate. Levels of thymosins β4 and β10 were under developmental regulation. It is concluded that peaks from thymosins may provide extended information for an NMR spectroscopist and thus they have to be taken into account in the interpretation of the newborn cerebral 1H NMR spectrum. © 1992 Academic Press, Inc.
Single‐input double‐tuned foster‐type probe circuit
Authors: Kan Siew , Jehenson Philippe , Leroy‐Willig Anne
Published: March 2007

Synthesizing two different values of inductance from a given sample coil for use in a single‐input double‐tuned circuit is possible by means of three extra LC elements. A detailed analysis with derived equations shows how to calculate the circuit component values and what to expect from this kind of probe. It also derives the upper limit of the trap coil/sample coil inductance ratio beyond which no solution exists to double‐tune the 31P‐1H probe. The general expression for the channel efficiency shows that the latter is a function not only of the inductance of the coils, but also of their quality factor and of the operating frequencies. A numerical example is given illustrating good agreement between experiment and theory provided high quality rf capacitors are used. © 1991 Academic Press, Inc.
Fast and accurate measurements of T1 using a multi‐readout single inversion‐recovery sequence
Authors: Gowland P. A. , Leach M. O.
Published: March 2007

TOMROP is a multiple readout single inversion‐recovery sequence which may potentially allow the measurement of multi‐exponential T1 recoveries in vivo by NMR imaging. It is shown that several important modifications must be made to this sequence to permit T1 to be measured accurately and reliably. With these modifications it is possible to measure T1 with a mean systematic error of ‐1.5% (‐0.3% for samples with T1 > 300 ms), a mean accuracy of 3.1% (2.1% for samples with T1 > 300 ms) and a mean repeatability of 1.4% (1.4% for samples with T1 > 300 ms), using data collected in 6.4 min from sixteen 128 × 128 matrix images.
Phosphodiesters in saponified extracts of human breast and colon tumors using 31P magnetic resonance spectroscopy
Authors: Merchant Thomas E. , Characiejus Dainius , Kasimos John N. , Otter Willem Den , Gierke Louis W. , Glonek Thomas
Published: March 2007

Saponified phospholipid extracts of malignant and normal human breast and colon surgical tissue specimens (n = 45) generate characteristic phosphodiester profiles using 31P magnetic resonance (MR) spectroscopy. The resultant 31P MR spectroscopic profiles of the analyzed tissues are used to differentiate malignant from normal. The appearance of an uncharacterized resonance at 0.29 δ in the malignant tissue spectra (50% of breast and 75% of colon specimens) is the most notable qualitative finding. Quantitatively, malignant colon tissues differ from normal colon tissues with depressed levels of phosphatidylserine and elevated levels of glycerol 3‐phosphorylglycerol and an index measuring the summation of phospholipid polar head group residues with free hydroxyl groups. Malignant breast tissues have significantly elevated levels of glycerol 3‐phosphorylethanolamine and significantly depressed levels of glycerol 3‐phosphorylcholine compared to normal breast tissues, reflecting a perturbation in the balance of lipid residues that are the respective breakdown products of phosphatidylethanolamine and phosphatidylcholine. The concentration of the polar head group residues is compared to 31P MR spectroscopic profiles of colon and breast tissue phospholipids, in order to demonstrate the quantitative nature of the technique employed.
Signal‐to‐noise, resolution, and bias function analysis of asymmetric sampling with zero‐padded magnitude ft reconstruction
Authors: Hurst Gregory C. , Hua Jianmin , Simonetti Orlando P. , Duerk Jeffrey L.
Published: March 2007

This report describes NMR image effects due to sampling asymmetry when using zero‐padded magnitude FT reconstruction. With this method, the MTF is not flat over the spatial frequency passband, so resolution cannot be accurately described by a single variable such as voxel size. At small to moderate asymmetry, shortened (reduced window duration) asymmetry provides increased S/N and decreased resolution, whereas shifted (constant window duration) asymmetry yields essentially constant S/N with simultaneously increased and decreased resolution. A bias function expression describes image distortion due to sampling in terms separable from the imaged object. The analyses are consistent with previous descriptions of perceived image differences related to data asymmetry.
Solid‐State 31P NMR Spectroscopy of Bone and Bone Substitutes
Authors: Marchandise Xavier , Belgrand Patrick , Legrand André‐Pierre
Published: March 2007

Using magic angle sample spinning 31P NMR spectroscopy, we studied NMR parameters of hydroxyapatite, calcium‐deficient hydroxyapatite, and β‐tricalcium phosphate. These data were compared to rabbit bone parameters. Rabbit bone spectrum is similar to deficient hydroxyapatite spectrum but high‐power proton decoupling did not modify its linewidth. Moreover, both bone T1 and deficient hydroxyapatite T1 were much longer than pure hydroxyapatite T1 and β‐tricalcium phosphate T1. We used these results to develop quantitative analysis of newly deposited bone inside β‐tricalcium phosphate implants in rabbit. This method made it possible to demonstrate the effect of porosity on osteoinduction of biomaterials.© 1992 Academic Press,Inc.
An NMR Phased Array for Human Cardiac 31P Spectroscopy
Authors: Hardy Christopher J. , Bottomley Paul A. , Rohling Ken W. , Roemer Peter B.
Published: March 2007

A four‐coil phased‐array 31P NMR receiver was designed and tested for human cardiac applications, to determine whether the combination of relatively high signal‐to‐noise ratio (SNR) and large field of view produced in 1H imaging is also realized for in vivo 31P spectroscopy. Spectra were acquired in parallel from an array of four overlapping 6.5‐cm surface coils using one‐ and two‐dimensional phase‐encoding pulse sequences and were optimally combined to yield composite spectroscopic images. The phased array was found to generate useful 31P spectra from a 2.5‐fold wider lateral region around the anterior myocardium than a single receiver of the same size as the array elements, with no increase in imaging time. In addition, the sensitive depth was increased by up to 2 cm over that of a single coil. Spectra could be acquired in roughly 15 min from a region extending to the middle of the heart, with voxel sizes of 2 X 2 X 4 cm3. For the average heart voxel, the SNR of the combined spectrum was higher than that of the best spectrum from any one coil in the array by 30%, with some voxels showing an increase as high as 60%.© 1992 Academic Press,Inc.
Proton Relaxation Studies of Water Compartmentalization in a Model Neurological System
Authors: Menon R. S. , Rusinko M. S. , Allen P. S.
Published: March 2007

Proton relaxation measurements from 18 crayfish abdominal nerve cords (a model of human CNS) are used to demonstrate that the transverse (though not the longitudinal) relaxation can be decomposed into four reproducible components that, in conjunction with optical and electron microscopy of the morphology, can be assigned to three water compartments within the cord and possibly to the mobile lipid protons. The assignments are extraaxonal water protons (32 ± 9% and mean T2 = 600 ± 200 ms), axonal water protons (59 ± 12% and mean T2 = 200 ± 30 ms), intramyelinic water protons (7 ± 4% and mean T2 = 50 ± 20 ms), and finally an unsubstantiated assignment of lipid protons (2.0 ± 2.0% and mean T2 = 7 ± 4 ms).© 1992 Academic Press,Inc.
Cardiac Tagging with Breath‐Hold Cine MRI
Authors: McVeigh Elliot R. , Atalar Ergin
Published: March 2007

A method is presented for measuring myocardial deformation in a breath‐hold with tagged cine MRI. Tagged cine images of human hearts are obtained in arbitrary oblique planes on a standard imager with as few as four heartbeats. The scan time has been reduced 16‐ to 64‐fold from previous techniques.© 1992 Academic Press,Inc.
Comparison of localized proton NMR signals of skeletal muscle and fat tissue in vivo: Two lipid compartments in muscle tissue
Authors: Schick Fritz , Eismann Beate , Jung Wulf‐Ingo , Bongers Hilmar , Bunse Michael , Lutz Otto
Published: March 2007

In vivo 1H NMR spectra of small volumes‐of‐interest (VOI) were localized in human soleus muscle (8 ml) and compared with volume selective spectra of subcutaneous fat tissue and femoral yellow bone marrow (2 ml). All examinations were performed by the double spin echo (PRESS) localization technique. To provide comparability, spectra of different tissues were recorded using identical sequence timing. Clearly improved resolution of the lipid signals of muscle tissue was obtained using long echo times TE > 200 ms. The spectra of muscle tissue exhibit lipid signals that stem from two compartments with a difference of their resonance frequencies of about 0.2 ppm (Larmor frequency difference 12‐13 Hz at 1.5 T). The existence of two fatty acid compartments is supported by measurements of the relaxation times and line shape analysis. Both compartments contain fatty acids or triglycerides with similar composition. Probably one compartment corresponds to fat cells within muscle tissue, the other compartment with lower Larmor frequency is located within muscle cells.
Aortic ghost artifact in ultrashort te multislice gradient echo MR images is not increased by paramagnetic enhancement
Authors: Mitchell Donald G. , Ortega Hector , Mohamed Feroze , Tascyian Talin , Vinitski Simon
Published: March 2007

Pulsation artifact on gradient echo images with ultrashort TE (i.e., <3 msec) and intermediate TR is primarily from view‐to‐view amplitude modulation. Paramagnetic contrast agents increase the signal from blood during diastole without increasing the intensity of unsaturated systolic blood, decreasing signal modulation between systole and diastole. In a phantom and in humans, artifact decreased or remained the same following contrast enhancement.
In vitro high resolution 1h‐spectroscopy of the human prostate: Benign prostatic hyperplasia, normal peripheral zone and adenocarcinoma
Authors: Schiebler Mark L. , Miyamoto Kent K. , White Mark , Maygarden Susan J. , Mohler James L.
Published: March 2007

1H‐spectra at 360 MHz from perchloric extracts of 35 human prostate specimens were obtained. First, we sought to define what peaks can be assigned in vitro, and thus, potentially seen in vivo. Second, we sought to try to discriminate between adenocarcinoma, normal peripheral zone and benign prostatic hyperplasia using spectral fingerprints. Thirteen samples of adenocarcinoma, 11 samples of benign prostatic hyperplasia, and 11 samples of normal contralateral peripheral zone were analyzed by obtaining a ratio from the maximum area of each major peak and the area of an added standard (3‐trimethyl‐silyl‐propionic acid). There was a significantly larger benign prostate hyperplasia citrate standardized peak area when compared to the adenocarcinoma citrate standardized peak area for each patient (P < 0.05). However, the citrate standardized peak areas from the normal peripheral zones were not significantly different from those found in the adenocarcino‐mas. Four out of 13 cases of stromal hyperplasia had similarly low levels of citrate as their respective gland's adenocarcinoma. We also found a sharp peak at 2.05 ppm that was seen in 4 out of 13 adenocarcinoma samples and in only 1 out of 13 of the benign prostate hypertrophy samples which has tentatively been assigned to N‐acetyl neuraminic acid. Further studies are required to assess whether low citrate levels alone can serve to exclusively diagnose adenocarcinoma of the prostate.
Assessment of changes in murine tumor oxygenation in response to nicotinamide using 19F NMR relaxometry of a perfluorocarbon emulsion
Authors: Hees Paul S. , Sotak Christopher H.
Published: March 2007

The oxygen dependencies of the 19F NMR spin‐lattice relaxation rates (R1 = 1/T1) of a perfluorocarbon emulsion sequestered in a murine tumor model has been used to evaluate nicotinamide, a radiosensitizer believed to act through enhanced tissue oxygenation. Fluorine‐19 NMR spectroscopic measurements from solid Radiation‐Induced Fibrosarcoma (RIF‐1) tumors in C3H mice showed a statistically significant improvement in tumor pO2 for a Nicotinamide‐treated group, with a ΔpO2 = 4.7 ± 3 torr (=mm Hg) (Mean ± SEM) at t = 60 min (P <.01), and 4.5 ± 3 at t = 70 min post intraperitoneal injection (P < 0.02) as compared with saline‐treated Controls, while several other time points for which t > 30 min were significant at the P < 0.05 level. Both groups had n = 10, and the statistics were based on Student's one‐tailed group t test. By comparison, in another study group where breathing gas was switched from air to 100% O2, a statistically insignificant increase of 2 torr was realized in tumor pO2 (n = 9). The maximal treatment effect occurs at a delay of 60 to 70 min, consistent with results obtained by other investigators using radiobiology techniques. Fluorine‐19 spectroscopic relaxometry can measure therapeutically meaningful changes in in vivo tumor pO2 and represents an improvement in expenditures of time, animal resources, and statistical power over conventional radiobiological methods.