bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new perfluorocarbon for use in fluorine‐19 magnetic resonance imaging and spectroscopy
Authors: Sotak Christopher H. , Hees Paul S. , Huang Hsu‐Nan , Hung Ming‐H. , Krespan Carl G. , Raynolds Stuart 
Published: March 2007

AbstractA new perfluorocarbon, PTBD (perfluoro‐2,2, 2′, 2′‐tetrameth‐yl‐4,4′‐bis(1, 3‐dioxolane)), is described for use in 19F MR imaging and spectroscopy. Two‐thirds of the molecular fluorine in PTBD resonates at a single frequency and can be imaged without the use of frequency‐selective spin‐echo (SE) MRI pulse sequences to suppress chemical shift artifacts. The absence of strong homonuclear spin‐spin coupling to the imagable ‐CF3 groups in PTBD minimizes signal attenuation in 19F SE MRI due to J‐modulation effects. For equimolar concentrations of perfluorocarbon, PTBD gives an approximately 17% increase in sensitivity, relative to literature results for perfluorinated amines, at short values of TE (∼10 ms) in 19F SE MRI. These attributes allow 19F MRI of PTBD to be performed on standard clinical imaging instrumentation (without special hardware andJor software modification) and an in vivo example in a mouse is shown. This investigation involved characterizing the MR T1 and T2 relaxation times of PTBD as well as the MR spin‐lattice relaxation rate, R1 (1JT1), of PTBD as a function of dissolved oxygen concentration. The T1 and T2 relaxation times and R1 relaxation rates of perfluorooctyl bromide (PFOB) were also obtained, under similar experimental conditions, to compare and contrast PTBD with a representative perfluorocarbon that has been widely employed for 19F MRIJMRS applications.
A cylindrically symmetric magnetic shield for a large‐bore 3.0 Tesla magnet
Authors: Ewing James R. , Warner Rory , Helpern Joseph A. 
Published: March 2007

AbstractA 3.0 Tesla, 0.80‐m bore magnet replaced our previous 1.9 Tesla, 0.76‐m magnet. The 3.0 Tesla replacement magnet had a dipole moment of 1.7 with respect to that of the 1.9 Tesla magnet. The pre‐existing cylindrically symmetric passive steel shielding was modified to confine the fringe fields of the replacement magnet to match those of the previous magnet.A cylindrically symmetric inner shield insert of about 20,000 kg was designed, fabricated, and installed. Upon energization of the magnet, the combined shielding met all design criteria. Alternative designs, optimization of cylindrically symmetric designs, and costs of fabrication, are presented herein.
Phased spectroscopic images: Application to the characterization of the 1H 1.3‐ppm resonance in intracerbral tumors in the rat
Authors: Le Fur Y. , Ziegler A. , Bourgeois D. , Decorps M. , Remy C. 
Published: March 2007

AbstractSpectra obtained with phase‐encoding techniques show phase‐shifts varying from voxel to voxel. The procedure allowing voxel‐dependent phase‐shifts to be compensated is presented. The method has been applied to the characterization of the 1.3‐ppm resonance observed in intracerebral tumors in the rat.
Oxygen measurement inside an NMR magnet with a catheter electrode
Authors: Eijgelshoven M. H. J. , Lekkerkerk C. , van Beek J. H. G. M. , van Echteld C. J. A. 
Published: March 2007

AbstractIn this study we show the possibility of continuous oxygen tension measurement inside an NMR magnet without disturbance of simultaneous NMR data acquisition. Our modified Clark‐type oxygen electrode has a fast response (2 s) and can be inserted deep into small bore NMR systems thanks to its small diameter (2 mm).
Simultaneous multi‐site EPR spectroscopy in vivo
Authors: Smirnov Alex I. , Norby Shong‐Wan , Clarkson R. B. , Walczak Ted , Swartz Harold M. 
Published: March 2007

AbstractA gradient technique to measure electron paramagnetic resonance spectra simultaneously at several different locations is described. The technique is based on the use of point probes containing paramagnetic centers. The value of the magnetic field gradient is chosen to be sufficient to separate the EPR signals from the different paramagnetic probes yet at the same time small enough to change only minimally the shape of individual signals. The conditions to apply this technique are considered in detail. When experimental data have a high signal‐to‐noise ratio, the lineshape distortion induced by the gradient can be corrected with the aid of a known distribution function of paramagnetic centers within the probe. The maximum entropy deconvolution algorithm is successfully applied for the correction of significantly distorted lines. The technique is experimentally tested and applied to measure the concentration of oxygen in hypertrophied rat myocardium and normal rat kidney in vivo by low frequency EPR (L‐band, 1.2 GHz). No types of EPR oxygen‐sensitive probes‐lithium phthalocyanine crystals and synthetic carbohydrate chars‐were used.
A comparison of an inductively coupled implanted coil with optimized surface coils for in vivo NMR imaging of the spinal cord
Authors: Wirth III E. D. , Mareci T. H. , Beck B. L. , Fitzsimmons J. R. , Reier P. J. 
Published: March 2007

AbstractA study was performed to determine whether an implanted, inductively coupled nuclear magnetic resonance (NMR) imaging spine coil could provide a significant gain in signal‐to‐noise ratio (SNR) on images of the spinal cord relative to the SNR of optimized surface coils. Implanted coils were surgically affixed to the upper lumbar spine (first lumbar through third lumbar vertebrae) in a total of four adult cats. The implanted coil was inductively coupled to an external 12 × 12 cm square surface coil that was mounted on a 14‐cm diameter Plexiglas® cradle (Townsend Industries, Des Moines, IA). Two similar cradles were prepared with transmit‐only 12 × 12 cm surface coils and either a receive‐only 6 × 6 cm square surface coil or a receive‐only quadrature coil pair (two 4 × 6 cm coils overlapped slightly to minimize their mutual inductance) with 'the same surface area (6 × 6 cm). A total of five single‐slice, T1‐weighted spin‐echo images (TR = 500 ms, TE = 30 ms, 4‐mm slice thickness) were acquired from a 1‐liter saline phantom and from the second lumbar spinal level in an adult cat with a normal, uninjured spinal cord. On the spinal cord images, the quadrature coil exhibited a factor of 1.65 increase in SNR relative to the single‐turn surface coil, whereas the implanted coil achieved a factor of 2.19 increase in SNR. The improved SNR for the quadrature and implanted coils was observed as a dramatic improvement in the clarity of the images. The high SNR available with the implanted coils allows the acquisition of higher resolution NMR images and opens up the possibility of measuring localized spectroscopy in vivo within the spinal cord.
Asymmetric single‐turn solenoid for MRI of the wrist
Authors: Szeglowski Scott D. , Hornak Joseph P. 
Published: March 2007

AbstractA single‐turn solenoid, lacking the conventional cylindrical or rectangular symmetry, was constructed for magnetic imaging of the human wrist at 1.5 Tesla. As is characteristic of singleturn solenoids, this wedge‐shaped geometry solenoid was found to have a high filling factor and quality factor, as well as produce images with a favorable signal‐to‐noise ratio. The radio frequency (RF) transmitter power required to produce a 90° pulse in the solenoid was 130 mW. The asymmetric solenoid had a small variation in the intensity of the RF field across its volume, which is characteristic of symmetrical single‐turn solenoids. The combination of these four properties of the coil resulted in the production of excellent 1.5‐mm thick anatomical images of the wrist.
Continuous measurement of cell volume changes in perfused rat salivary glands by proton NMR
Authors: Larcombe‐McDouall Jacky B. , Seo Yoshiteru , Steward Martin C. 
Published: March 2007

AbstractChanges in intracellular and extracellular water content have been measured in perfused rat salivary glands by repetitive application of an inversion recovery (IR) pulse sequence. The relaxation reagent Gd‐DTPA (10 mM) was included in the per‐fusate so that the intracellular and extracellular water proton signals could be distinguished by their different longitudinal relaxation times. Changes in water content in response to altered perfusion pressure and perfusate osmolarity were determined at 30‐s intervals and indicated a clear separation of the intracellular and extracellular components. Using a modification of the IR pulse sequence, changes in intracellular water content were also measured at 6‐s intervals. With this time resolution, differences in the rates of cell shrinkage in response to hyperosmotic perfusates and the secretomotor agonist acetylcholine were observed. The results suggest that this approach offers a relatively noninvasive method for studying cell volume regulation in intact, perfused tissues and organs.
In vivo19F spin relaxation and localized spectroscopy of fluoxetine in human brain
Authors: Komoroski Richard A. , Newton Joseph E. O. , Cardwell David , Sprigg Jay , Pearce John , Karson Craig N. 
Published: March 2007

AbstractFluorine‐19 NMR spectroscopy was used to monitor the anti‐depressant drug fluoxetine (and its metabolite norfluoxetine) in vivo in human brain. A quadrature birdcage head coil, developed for operation at 60.1 MHz, yielded a signal from the head 2 to 4 times stronger than for surface coils. It was used to measure the in vivo 19F spin‐lattice relaxation time (T1) of fluoxetine for five patients by the inversion‐recovery technique. The individual T1s varied from 149 to 386 ms, which was attributed in part to interindividual differences based on the reproducibility of a phantom T1. The individual T1 correlated weakly with approximate brain concentration. A lower limit of 3 to 4 ms was found for the spin‐spin relaxation time from line width measurements. Low resolution 4‐dimensional spectroscopic imaging confirmed that the single in vivo 19F resonance for fluoxetine arose primarily from brain. The spectrum of a cerebral hemisphere (in formalin) obtained at autopsy from a patient on 40 mg/day of fluoxetine for 19 weeks was comparable with that seen for patients in vivo. The in vivo signal arose about equally from fluoxetine and the active me tabolite norfluoxetine, as demonstrated by the in vitro 19F NMR spectrum of the lipophilic extract of a small section of brain. In virto quantitation of frozen samples from three brain regions yielded combined fluoxetine/norfluoxetine concentrations of 12.3 to 18.6 μ/ml, which is higher than typically determined in vivo, and suggests that the fluorinated drugs may not be 100% visible in vivo.
Vascular interventions guided by ultrafast MR imaging: Evaluation of different materials
Authors: Köchli V. D. , McKinnon G. C. , Hofmann E. , von Schulthess Gustav K. 
Published: March 2007

AbstractThe ability of MRI to acquire not only anatomical but also functional information makes MRI guided vascular interventions an interesting goal. Recent developments in ultrafast MR imaging sequences such as fast gradient echo or echo planar (EPI) mean that not only real time MRI but also MRI guided vascular interventions are real possibilities for the not too distant future. However, currently available guide wires and catheters are potentially unusable in MRI because they are either ferromagnetic or MRI invisible. In order to find different materials suitable for real time MRI, various devices were examined with fast gradient echo and interleaved EPI pulse sequences. The measurements were performed using a continuously running, pseudo real time MRI system to investigate the dynamic imaging behavior under guide wire insertion. Suggestions are made as how to construct guide wires and catheters, which can be visualized with ultrafast imaging sequences, while not causing prohibitive artifacts or image distortions.
Scalar coupling and zero‐quantum coherence relaxation in STEAM: Implications for spectral editing of lactate
Authors: Kingsley Peter B. 
Published: March 2007

AbstractAccurate values were obtained for the lactate zero‐quantum coherence frequency, ωZQ = ωi‐ωs = CH3–CH chemical shift difference, and scalar coupling constant, J, by using the methyl signal's amplitude modulation during the TM period of a STEAM sequence, 90°–TE/2–90°–TM–90°–TE/2‐ Acquire. Although most previous work has used J= 7.35 Hz, or 1/J= 136 ms, the actual value is J= 6.93 ± 0.05 Hz or 1/J = 144.3 ± 1 ms. In addition, the CH3–CH chemical shift difference = 2.7956 ± 0.0005 ppm, and the relaxation time for zero‐quantum coherence, TZQ, was much shorter than either T2 or T1 for the methyl resonance. A small component of the signal with TE= 144 ms, which was not modulated at the zero‐quantum coherence frequency or by scalar coupling, was assigned to longitudinal two‐spin order magnetization (IzSz) created by imperfect radio frequency pulse profiles. This information will allow improved editing of the lactate signal and more accurate quantitation of lactate concentrations.
Time and frequency domain analysis of NMR data compared: An application to 1D 1H spectra of lipoproteins
Authors: van den Boogaart A. , Ala‐Korpela M. , Jokisaari J. , Griffiths J. R. 
Published: March 2007

AbstractA comparison between a time domain analysis algorithm (VARPRO) and a frequency domain analysis algorithm (FITPLAc) for parameter estimation of magnetic resonance spectroscopy (MRS) data series is presented. VARPRO analyses the measured MRS signal (free induction decay; FID); FITPLAc analyses the discrete Fourier transform of the FID, the frequency domain magnetic resonance spectrum. A rapid time domain method, used to subtract the dominating water resonance from a 1H MRS FID, without affecting the metabolites of interest, is outlined and applied. Also a new “pseudo‐frequency selective” approach to time domain fitting is introduced. The possibilities of combining the most favorable features of time and frequency domain processing into one single MRS signal processing method are assessed. The 1H MRS signals of ultracentrifuged very low (VLDL), intermediate (IDL), and high (HDL) density lipoprotein fractions from human blood plasma were used for the comparisons. The results from both algorithms were in good agreement.
Dual contrast GRASE (gradient‐spin echo) imaging using mixed bandwidth
Authors: Feinberg David A. , Kiefer Berthold , Litt Andrew W. 
Published: March 2007

AbstractEqual time spacing of RF pulses in the CPMG sequence imposes a constraint of equal signal read periods in spin‐echo train imaging. GRASE imaging differs by using multiple read gradients in each π‐π time interval, which are not constrained to be equal in number or duration. This additional degree of freedom is developed in dual contrast imaging. Closely spaced read periods are used for the PDW image to reduce T2 decay effects, while fewer low‐bandwidth read periods in each of several π‐π intervals are used to raise the signal‐to‐noise ratio and avoid signal averaging in the T2‐weighted image. Key words: magnetic resonance imaging; gradient‐spin echo; fast imaging.
In vivo visualization of myelin water in brain by magnetic resonance
Authors: Mackay Alex , Whittall Kenneth , Adler Julian , Li David , Paty Donald , Graeb Douglas 
Published: March 2007

AbstractWe exploit the intrinsic difference in magnetic resonance spin‐spin relaxation time, T2, between water associated with myelin sheaths and water in other central nervous system tissue in order to measure myelin water content within any region of an image or to generate indirectly a myelin map of the brain. In normal volunteers, myelin water maps give the expected myelin distribution. In multiple sclerosis patients, lesions exhibit different myelin water contents providing insight into the de‐myelination process unavailable from conventional magnetic resonance images. In vivo myelin measurement has important applications in the clinical management of multiple sclerosis and other white matter diseases.
A novel saturation transfer contrast method for 3D time‐of‐flight magnetic resonance angiography: A slice‐selective off‐resonance sinc pulse (SORS) technique
Authors: Miyazaki Mitsue , Kojima Fumitoshi , Ichinose Nobuyasu , Onozato Yukio , Igarashi Hiromitsu 
Published: March 2007

AbstractSaturation transfer contrast (STC) techniques have been employed to decrease the signal intensity of observed water by saturating a broad proton component. The STC pulse, generally spatially nonselective, reduces the signal of brain background tissues as well as inflowing blood in 3D time‐of‐flight (TOF) angiography. We present a novel technique, a slice‐selective off‐resonance sinc pulse (SORS), which is employed to enhance inflowing blood and to suppress the signal of stationary background tissues. The STC effects of the SORS and other spatially nonselective methods influencing inflowing blood is discussed in detail. Angiograms using the SORS method are also presented to demonstrate improved vessel conspicuity. In addition, the SORS method is applicable to imagers with a whole‐body RF transmitter system.
31P NMR assessment of orthotopic liver rejection in a rat model
Authors: Bowers John L. , Kawano Katsunori , Metz Kenneth R. , Teramoto Kenichi , McCullough Ann , Clouse Melvin E. 
Published: March 2007

Abstract31P NMR spectroscopy was used serially to study rejecting (ACI→LEW) and nonrejecting (ACl→ACl) orthotopic liver transplants in rats. Recipients were evaluated on post‐transplant days 1,3, 5, 7, 9, and 11. The relative changes in phosphomonoester (PME), inorganic phosphate (Pi), high‐energy phosphates and pH were studied. The earliest significant difference between the rejecting and nonrejecting groups was a decrease in the α‐NTP peak area on Day 5. This was followed by significant decreases in β‐NTP and pH, and increases in PME and Pi on Day 7. High‐resolution 31P NMR spectra of perchloric acid extracts demonstrated the PME increase to be due mainly to elevated phosphoethanolamine. Using the parameter (Pi + PME)/(α + β + γ‐NTP), rejecting livers were distinguished from nonrejecting livers at a moderate stage of rejection.
A MRI bolus tagging method for observing helical flow in the descending aorta
Authors: Hoydu Alison K. , Bergey Philip D. , Haselgrove John C. 
Published: March 2007

AbstractWe present a MRI bolus tagging method for exploring the helical nature of blood flow in the aorta. Two image series are collected, the first to quantify longitudinal flow (coronal/sagittal imaging plane‐transverse saturation plane), the second to measure rotational flow (transverse imaging plane‐coronal/sagittal saturation plane). The experimental protocol has been established in healthy adult volunteers and children with normal vasculature. Our results permit immediate visualization of the unique nature of helical flow in each volunteer. We demonstrate evidence of rapid helical twist, no helical twist, and reversal of twist.
Real‐Time Functional Magnetic Resonance Imaging
Authors: Cox Robert W. , Jesmanowicz Andrzej , Hyde James S. 
Published: March 2007

AbstractA recursive algorithm suitable for functional magnetic resonance imaging (FMRI) calculations is presented. The correlation coefficient of a time course of images with a reference time series, with the mean and any linear trend projected out, may be computed with 22 operations per voxel, per image; the storage overhead is four numbers per voxel. A statistical model for the FMRI signal is presented, and thresholds for the correlation coefficient are derived from it. Selected images from the first real‐time functional neuroimaging experiment (at 3 Tesla) are presented. Using a 50‐MHz workstation equipped with a 14‐bit analog‐to‐digital converter, each echo planar image was acquired, reconstructed, correlated, thresh‐olded, and displayed in pseudocolor (highlighting active regions in the brain) within 500 ms of the RF pulse.
ATP production and mechanical work in exercising skeletal muscle: A theoretical analysis applied to 31P magnetic resonance spectroscopic studies of dialyzed uremic patients
Authors: Kemp Graham J. , Thompson Campbell H. , Taylor Doris J. , Radda George K. 
Published: March 2007

Abstract31P magnetic resonance spectroscopy (31P MRS) can yield much information about bioenergetics in skeletal muscle. During mixed aerobic/glycolytic exercise, changes in phos‐phocreatine (PCr) concentration and pH may be abnormal because of reduced muscle mass or reduced efficiency (which the authors combine here as “effective muscle mass”) or because of reduced oxidative capacity. The authors show how these can be distinguished by calculating the nonoxidative and oxidative costs of mechanical work, and also of work per unit of effective muscle mass (measured using the initial rate of ATP turnover). These quantities are substantially time‐independent during incremental exercise, and so can be used to compare exercise studies of differing duration. The authors illustrate this analysis by showing that in dialyzed patients with chronic renal failure, the substantial exercise abnormalities seen by 31P MRS are due mainly to a decrease in effective muscle mass, which outweighs the oxidative defect implied by the abnormal PCr recovery kinetics.
Chemical Shift Imaging from Simultaneous Acquisition of a Primary and a Stimulated Echo
Authors: Franconi Florence , Akoka Serge 
Published: March 2007

AbstractAn imaging method is presented for obtaining chemical shift images from only one acquisition. Images are acquired with the same spatial resolution as in regular spin‐echo imaging. The sequence is based on the simultaneous acquisition of a spin echo and a stimulated echo in a single pass. The use of 90° radiofrequency pulse flip angles results in the same proton density, T2 and T1 weighting for the two echoes. Application of this sequence to chemical shift imaging is discussed for three fat suppression techniques (chopper, CHESS, and hybrid). Imaging was performed on phantoms and volunteers. The image quality was the same as those obtained by the chopper and the hybrid methods and the acquisition time was reduced by a factor of two.
An improved quadrature or phased‐array coil for MR cardiac imaging
Authors: Fayad Zahi A. , Connick Thomas J. , Axel Leon 
Published: March 2007

AbstractA tailored receive‐only coil for cardiac imaging has been designed. The coil consists of two overlapping coil elements and can be used either as a quadrature surface coil or as a phased‐array coil. Through phantom experiments and images of the heart, the authors have shown that the improved cardiac coil provided a signal‐to‐noise ratio 1.6 times higher than a conventional quadrature spine coil, 1.4 times higher than that of a single coil (having the same shape and total dimension), and three times higher than the body coil at the depth of the posterior wall of the heart. The authors have also shown that the cardiac coil improved image quality everywhere in the heart. This coil will enhance routine clinical cardiac studies as well as other examinations such as myocardial perfusion, wall motion, and coronary artery imaging.