bluuebunny/crossref_metadata_2025_split huggingface dataset:
Noninvasive temperature imaging using diffusion MRI
Authors: Delannoy J. , Chen Ching‐Nien , Turner R. , Levin R. L. , Le Bihan D. 
Published: March 2007

AbstractEfficacy 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractWe 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

AbstractAttempts 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

AbstractIn 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

AbstractThe 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.
A new two‐dimensional phase unwrapping algorithm for MRI images
Authors: Hedley Mark , Rosenfeld Dov 
Published: March 2007

AbstractThe 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

AbstractAs 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

AbstractThe 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

AbstractWe 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

AbstractIn 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

AbstractSynthesizing 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

AbstractTOMROP 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

AbstractSaponified 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

AbstractThis 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

AbstractUsing 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

AbstractA 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

AbstractProton 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

AbstractA 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

AbstractIn 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.