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Now showing items 1 - 16 of 1895

  • Feasibility of LNG-IUS in a baboon model

    Jason D. Bell Jason   Ingrid L. Bergin   Melissa F. Natavio   Fatima Jibrel   Melissa K. Zochowski   William J. Weadock   Scott D. Swanson   David M. Aronoff   Dorothy L. Patton  

    Background The baboon (Papio hamadryas anubis) is an attractive model for intrauterine contraception research due to anatomic similarity to the human. Although non-human primates have previously been used for intrauterine contraception research, it was unknown whether modern intrauterine devices (IUDs) can be placed in an anatomically similar position in the baboon. This study sought to determine whether human-use IUDs could be seated correctly in the uterus of the baboon. Study Design The levonorgestrel-releasing intrauterine system (LNG-IUS) was placed ex vivo into two baboon uteri collected at necropsy and in 3 living, reproductively proven baboons. Results Correct placement of human-use IUDs in the baboon was confirmed by both MRI and ultrasound. This study establishes that a LNG-IUS can be inserted into the baboon uterus and maintained without clinically adverse effects for at least 6 months. The positioning of the device is similar to positioning found in women. Conclusion These findings provide important support for studying IUD safety and efficacy in the baboon.
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  • Distribution and dynamics of laser-polarized 129Xe magnetization in vivo

    Scott D. Swanson   Matthew S. Rosen   Kevin P. Coulter   Robert C. Welsh   Timothy E. Chupp  

    The first magnetic resonance imaging studies of laser-polarized (129)Xe, dissolved in the blood and tissue of the lungs and the heart of Sprague-Dawley rats, are described. (129)Xe resonances at 0, 192, 199, and 210 ppm were observed and assigned to xenon in gas, fat, tissue, and blood, respectively. One-dimensional chemical-shift imaging (CSI) reveals xenon magnetization in the brain, kidney, and lungs. Coronal and axial two-dimensional CSI show (129)Xe dissolved in blood and tissue in the thorax. Images of the blood resonance show xenon in the lungs and the heart ventricle. Images of the tissue resonance reveal xenon in lung parenchyma and myocardium. The (129)Xe spectrum from a voxel located in the heart ventricle shows a single blood resonance. Time-resolved spectroscopy shows that the dynamics of the blood resonance match the dynamics of the gas resonance and demonstrates efficient diffusion of xenon gas to the lung parenchyma and then to pulmonary blood. These observations demonstrate the utility of laser-polarized (129)Xe to detect exchange across the gas-blood barrier in the lungs and perfusion into myocardial tissue. Applications to measurement of lung function, kidney perfusion, myocardial perfusion, and regional cerebral blood flow are discussed. Magn Reson Med 42:1137-1145, 1999. Copyright 1999 Wiley-Liss, Inc.
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  • Protein Mediated Magnetic Coupling between Lactate and Water Protons

    Scott D. Swanson  

    The magnetic coupling between methyl lactate protons and water protons in samples of cross-linked bovine serum albumin (BSA) is studied. Cross-relaxation spectroscopy shows efficient magnetization transfer from immobilized BSA to both water and methyl lactate protons. Transient and steady-state NOE experiments reveal a negative intermolecular NOE between methyl lactate and water protons. Lactate is indirectly detected by selectively saturating the methyl lactate protons and measuring the decrease in water proton magnetization. Indirect detection of methyl lactate protons is an order of magnitude more sensitive than direct detection in these model systems. Lactate was indirectly imaged, via the water proton resonance, with 1.1-mul voxels in 2 min. Immobilized BSA reduces the intermolecular correlation time between water and lactate protons into the spin-diffusion limit where the NOE is negative. Possible molecular mechanisms for this coupling and applications to in vivo spectroscopy are discussed
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  • Magnetic resonance imaging of microvascular leakage induced by myocardial contrast echocardiography in rats

    Scott D. Swanson   Chunyan Dou and Douglas L. Miller  

    The extent and magnitude of microvascular leakage induced by myocardial contrast echocardiography (MCE) were characterized with contrast-aided magnetic resonance imaging (MRI). Evans blue dye, Definity ultrasound contrast agent and Omniscan magnetic resonance contrast agent were injected intravenously in anesthetized rats suspended in a water bath. Diagnostic ultrasound B mode scans with 1:4 end-systolic triggering were performed at 1.5 MHz using a cardiac phased array scanhead to provide a short axis view of the left ventricle. The in situ peak rarefactional pressure amplitude (PRPA) was 2.0 MPa. Microvascular leakage was characterized by extraction of the dye from tissue samples and by imaging the distribution and concentration of Omniscan within the myocardium. The extracted Evans blue was 2.3 times greater than in shams (P<.05) for heart samples perfused with heparin saline, and 1.6 times greater than shams (not significant) for unperfused samples. The MRI showed the penetration of the ultrasound-induced capillary leakage throughout much of the scan plane. The overall gadolinium content measured by MR showed the same trends as the extracted Evans blue, but was more variable. For pooled data (perfused and unperfused), the exposed samples were significantly increased (P<.05) relative to the sham samples for both Evans blue and gadolinium content. Omniscan leakage was also discernable in two of four MRIs from intact rats (after sacrifice). These results demonstrate a potential for MR mapping of capillary leakage induced by contrast-aided ultrasound, with a possible application to spatial characterization of local drug delivery.
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  • Brain MRI with laser-polarized 129xe

    Scott D. Swanson   Matthew S. Rosen   Bernard W. Agranoff   Kevin P. Coulter   Robert C. Welsh   Timothy E. Chupp  

    Abstract The feasibility of brain MRI with laser-polarized 129Xe in a small animal model is demonstrated. Naturally abundant 129Xe is polarized and introduced into the lungs of Sprague-Dawley rats. Polarized xenon gas dissolves in the blood and is transported to the brain where it accumulates in brain tissue. Spectroscopic studies reveal a single, dominant, tissue-phase NMR resonance in the head at 194.5 ppm relative to the gas phase resonance. Images of 129Xe in the rat head were obtained with 98-μl voxels by 2D chemical shift imaging and show that xenon is localized to the brain. This work establishes that nuclear polarization produced in the gas phases survives transport to the brain where it may be imaged. Increases in polarization and delivered volume of 129Xe will allow clinical measurements of regional cerebral blood flow.
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  • Dynamics of lysine hydrochloride dihydrate measured by carbon-13 NMR spectroscopy

    Scott D. Swanson   Robert G. Bryant  

    Abstract The 13C NMR spectra for L-lysine hydrochloride dihydrate are reported for static samples and samples spinning at the magic angle, which provide resolution of each carbon resonance. The spectra and the T1s, T1p and T1 relaxation times for the carbon atoms demonstrate that there is little motion of the side-chain in this crystal environment. The carbon spin–lattice relaxation is approximately accounted for by rotational motions of the ammonium ions in the range 50–100 ns and motions of the water molecules in the region of 50 ps or 70 ns. The backbone motions are relatively unimportant for relaxation of the carbon spins.
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  • Proton-enhanced 13C imaging/spectroscopy by polarization transfer

    Scott D. Swanson   Leslie E. Quint   Hong N. Yeung  

    Abstract Carbon-13 magnetic resonance imaging/spectroscopy (CMRI/S) was performed using polarization transfer techniques where sensitivity of the carbon signal was enhanced by transferring the proton spin order to the carbon nuclei. The experimental feasibility of using polarization transfer techniques at 2.0 T was demonstrated with a phantom and an intact chicken egg. The potential clinical applications of CMRI/S with polarization transfer include the assessment of prostate cancer. Preliminary results using human prostate specimens are presented. © 1990 Academic Press, Inc.
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  • The hydration response of poly(L-lysine) dynamics measured by 13C-nmr spectroscopy

    Scott D. Swanson   Robert G. Bryant  

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  • Scott D Solomon MD

    Tofield, A.  

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  • Douglas D. Scott

    William B. Lees   Vergil E. Noble  

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  • Douglas D. Scott

    William B. Lees,Vergil E. Noble  

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  • FREDRICK D. SCOTT (Release No. 1306)

    Brenda P. Murray  

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  • Scott D. Seligman. Three Tough Chinamen.

    Hayford   Charles W.  

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  • FREDERICK D. SCOTT (Release No. 1363)

    Carol Fox Foelak  

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  • Scott D. Seligman. Three Tough Chinamen.

    Hayford, Charles W.  

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  • Book interview: Scott D Anthony

    Smith   N.  

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