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Phase Images (phase + image)
Kinds of Phase Images Selected AbstractsPositive contrast imaging of iron oxide nanoparticles with susceptibility-weighted imagingMAGNETIC RESONANCE IN MEDICINE, Issue 4 2010Frank Eibofner Abstract Superparamagnetic iron oxide particles can be utilized to label cells for immune cell and stem cell therapy. The labeled cells cause significant field distortions induced in their vicinity, which can be detected with magnetic resonance imaging (MRI). In conventional imaging, the signal voids arising from the field distortions lead to negative contrast, which is not desirable, as detection of the cells can be masked by native low signal tissue. In this work, a new method for visualizing magnetically labeled cells with positive contrast is proposed and described. The technique presented is based on the susceptibility-weighted imaging (SWI) post-processing algorithm. Phase images from gradient-echo sequences are evaluated pixel by pixel, and a mask is created with values ranging from 0 to 1, depending on the phase value of the pixel. The magnitude image is then multiplied by the mask. With an appropriate mask function, positive contrast in the vicinity of the labeled cells is created. The feasibility of this technique is proved using an agar phantom containing superparamagnetic iron oxide particles,labeled cells and an ex vivo bovine liver. The results show high potential for detecting even small labeled cell concentrations in structurally inhomogeneous tissue types. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Flexible Organic Solar Cells: Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar Cells (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Mater. The inside cover of this issue illustrates the fabrication of lightweight and flexible organic solar cells, developed by B. Walker et al. on page 3063, from a solution of fullerene and diketopyrrolopyrrole-based materials. The texture of the organic film on the substrate was taken from an atomic force microscope phase image of the high performance device (4.4% power conversion efficiency), showing the phase separation behavior of the two molecular semiconducting materials. [source] Fabrication of Oriented Multilayers of Photosystem I Proteins on Solid Surfaces by Auto-Metallization,ADVANCED MATERIALS, Issue 2 2008L. Frolov AFM phase image of PS I (Top) and platinized PS I (bottom) monolayers. The Pt patches serve as junctions for fabrication of oriented multilayer by covalent binding of cysteine mutants through the formation of sulfide bonds with the Pt. A larger absorption cross section and the serial arrangement resulted in an increase in the photopotential generated by the dry multilayers. [source] Self-assembly and morphology of polydimethylsiloxane supramolecular thermoplastic elastomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008Nicole E. Botterhuis Abstract Functionalization of polydimethylsiloxanes (PDMS) polymers with hydrogen-bonding ureidopyrimidinone (UPy) groups leads to supramolecular thermoplastic elastomers. In previous studies, no lateral stacking of UPy dimers was observed in UPy-functionalized polymers, unless additional urethane or urea groups were built into the hard block. However, we have shown that when PDMS is used as the soft block, this lateral aggregation of UPy dimers does take place, since long fibers could be observed in the atomic force microscopy (AFM) phase image. Also in bulk, the presence of these interactions was proven by oscillatory shear experiments. We attribute this aggregation to the incompatibility of soft block and hard block, leading to phase separation. Moreover, we have shown that additional urethane or urea groups in the hard block do lead to materials with more fibers and higher melting points. For the UPy-urea functionalized PDMS even single fibers are observed with AFM when dropcasted from a very diluted solution. When the length of the soft block is increased, the morphology changes from fibrous to spherical. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3877,3885, 2008 [source] Multiple-beam X-ray interferometry for phase-contrast microtomographyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2001Ulrich Bonse The first successful operation of an X-ray interferometer under conditions of non-planar three-beam diffraction for phase-contrast X-ray microtomography is reported. Intrinsic phase differences of the reflections used cancel from the three-dimensional phase image of the specimen. With simultaneous hkl and reflections of a synchrotron radiation beam in a side-by-side geometry, the size of the usable field of view is doubled and the investigated specimen volume is increased by a factor of four. As an example, the reconstructed slice of a mouse kidney is shown in phase contrast at 71,keV. Optimized choices of three-beam reflections and matching interferometer geometries useful for applications are presented. [source] Magnetic force microscopy of iron oxide nanoparticles and their cellular uptakeBIOTECHNOLOGY PROGRESS, Issue 4 2009Yu Zhang Abstract Magnetic force microscopy has the capability to detect magnetic domains from a close distance, which can provide the magnetic force gradient image of the scanned samples and also simultaneously obtain atomic force microscope (AFM) topography image as well as AFM phase image. In this work, we demonstrate the use of magnetic force microscopy together with AFM topography and phase imaging for the characterization of magnetic iron oxide nanoparticles and their cellular uptake behavior with the MCF7 carcinoma breast epithelial cells. This method can provide useful information such as the magnetic responses of nanoparticles, nanoparticle spatial localization, cell morphology, and cell surface domains at the same time for better understanding magnetic nanoparticle-cell interaction. It would help to design magnetic-related new imaging, diagnostic and therapeutic methods. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Design of an MR-compatible piezoelectric actuator for MR elastographyCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2002Kai Uffmann Abstract Magnetic Resonance (MR) elastography is a method for measuring tissue elasticity via phase images acquired with an MR scanner. The propagation of periodic mechanical waves through the tissue can be captured by means of a modified phase contrast sequence. These waves are generated with a mechanical oscillator (actuator) and coupled into the tissue through the skin. The actuator must be capable of generating a sinusoidal excitation with excellent phase and amplitude stability, while not disturbing the MR imaging process. In this work, an actuator based on a piezoelectric principle was developed. Based on the imaging evaluation of several material samples, the housing for the piezoelectric ceramic was constructed of aluminum. Smaller parts of the housing were manufactured from brass and titanium to fulfill the mechanical constraints. A lever was used to transfer the oscillation generated by the piezoelectric ceramic to the point of excitation. The lever amplifies the piezoelectric motion, allowing for a more compact design. Three different lever designs were characterized by an acceleration sensor both outside and inside the magnet. It was shown that the rigidity of the lever, as determined by its material and form, was decisive in determining the resonant frequency of the system and therefore the maximum practical frequency of operation. It was also shown that the motion of the oscillator is unaffected by the electromagnetic fields of the MR imager. The final design can be placed directly in the magnet bore within a few centimeters of the tissue volume to be imaged without generating significant artifacts. An amplitude range of 0,1 mm in the frequency range from 0 to over 300 Hz was achieved, sufficient for performing most MR elastography applications. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 239,254, 2002 [source] Blending of NR/BR/EPDM by reactive processing for tire sidewall applications.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Abstract Cure incompatibility in NR/BR/EPDM blends is a crucial problem, affecting blend properties. In a previous study, it was demonstrated that the mechanical properties of such blends can be significantly improved by utilizing a reactive processing technique, in which a pretreated EPDM is first prepared by incorporating all compounding ingredients in the EPDM and subsequent preheating, prior to crossblending with premasticated NR/BR. In the present article, the pretreated EPDM-moieties are prepared using two different accelerators, N -cyclohexyl-2-benzothiazole sulfenamide (CBS) and 6-nitro MBTS. The latter was synthesized and applied for the purpose of IR characterization. The infrared (IR) spectra of the pretreated, extracted EPDM demonstrate absorption peaks associated with the IR absorption of the functional groups in the accelerator fragments, attached to the EPDM. NR/BR/EPDM (35/35/30) ternary blends are prepared by reactive mixing of the pretreated EPDM with CBS fragments attached with premasticated NR/BR on a two-roll mill. Their blend morphological features are studied using the atomic force microscopy (AFM) and transmission electron microscopy (TEM) microscopic techniques, in comparison with those of blends prepared by a conventional straight mixing method. Both the tapping mode AFM phase images and TEM micrographs clearly show that reactive mixing leads to more homogeneous blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:2547,2554, 2007 [source] Can MR fluoroscopic triggering technique and slow rate injection provide appropriate arterial phase images with reducing artifacts on gadoxetic acid-DTPA (Gd-EOB-DTPA)-enhanced hepatic MR imaging?JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2010Hiroki Haradome MD Abstract Purpose: To evaluate whether using MR fluoroscopic triggering technique and slow rate injection improves the quality of arterial phase images in gadoxetic acid-DTPA-enhanced (Gd-EOB-DTPA) MR imaging because of proper acquisition timing and reduction of artifacts. Materials and Methods: Two hundred sixteen patients undergoing examination for liver diseases were retrospectively reviewed. All MR images were obtained with two Gd-EOB-DTPA injection protocols: (i) a combination protocol, in which the MR fluoroscopic triggering technique and slow rate injection (1 mL/s) were used; and for comparison, (ii) a conventional protocol, in which adjusted fixed scan delay and ordinary rate injection (2 mL/s) were adopted. Signal-to-noise ratio (SNR) of aorta, portal vein, and liver parenchyma on arterial phase images were calculated. Two blinded readers independently evaluated the obtained arterial phase images in terms of acquisition timing and degree of artifacts. Results: The SNRs of aorta and portal vein on arterial phase images were significantly higher in the combination protocol group (aorta/portal: 221.9 ± 91.9/197.1 ± 89.8) than that in the conventional protocol group (aorta/portal: 169.8 ± 97.4/92.7 ± 48.5) (P < 0.05). The acquisition timing for arterial phase images with the combination protocol was significantly better than that with the conventional protocol (P < 0.01). The image quality of the combination protocol was significantly higher than that of the conventional protocol (P < 0.01). The occurrence rate of moderate or severe degree of artifacts in the conventional protocol (38.0%) was more prominent than that in the combination protocol (18.5%). Conclusion: The combination of the MR fluoroscopic triggering technique and slow rate injection provides proper arterial phase images and reduces the artifacts in Gd-EOB-DTPA MR imaging. J. Magn. Reson. Imaging 2010;32:334,340. © 2010 Wiley-Liss, Inc. [source] Design and development of a prototype endocavitary probe for high-intensity focused ultrasound delivery with integrated magnetic resonance imagingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007Iain P. Wharton MRCS Abstract Purpose To integrate a high intensity focused ultrasound (HIFU) transducer with an MR receiver coil for endocavitary MR-guided thermal ablation of localized pelvic lesions. Materials and Methods A hollow semicylindrical probe (diameter 3.2 cm) with a rectangular upper surface (7.2 cm × 3.2 cm) was designed to house a HIFU transducer and enable acoustic contact with an intraluminal wall. The probe was distally rounded to ease endocavitary insertion and was proximally tapered to a 1.5-cm diameter cylindrical handle through which the irrigation tubes (for transducer cooling) and electrical connections were passed. MR compatibility of piezoceramic and piezocomposite transducers was assessed using gradient-echo (GRE) sequences. The radiofrequency (RF) tuning of identical 6.5 cm × 2.5 cm rectangular receiver coils on the upper surface of the probe was adjusted to compensate for the presence of the conductive components of the HIFU transducers. A T1-weighted (T1-W) sliding window dual-echo GRE sequence monitored phase changes in the focal zone of each transducer. High-intensity (2400 W/cm,2), short duration (<1.5 seconds) exposures produced subtherapeutic temperature rises. Results For T1-W images, signal-to-noise ratio (SNR) improved by 40% as a result of quartering the conductive surface of the piezoceramic transducer. A piezocomposite transducer showed a further 28% improvement. SNRs for an endocavitary coil in the focal plane of the HIFU trans-ducer (4 cm from its face) were three times greater than from a phased body array coil. Local shimming improved uniformity of phase images. Phase changes were detected at subtherapeutic exposures. Conclusion We combined a HIFU transducer with an MR receiver coil in an endocavitary probe. SNRs were improved by quartering the conductive surface of the piezoceramic. Further improvement was achieved with a piezocomposite transducer. A phase change was seen on MR images during both subtherapeutic and therapeutic HIFU exposures. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc. [source] A study of sulfamerazine single crystals using atomic force microscopy, transmission light microscopy, and Raman spectroscopyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2005Xiaoping Cao Abstract Sulfamerazine (SMZ) Form I and II single crystals were prepared from aqueous dispersions of SMZ bulk samples and studied using several microscopic and spectroscopic techniques. Transmission light microscopy and Raman spectroscopy were used to observe and identify single crystals. The results indicated that Form I single crystals tended to be rectangular laths while Form II ones tended to be hexagonal laths. Surface morphology of individual single crystals was further investigated by atomic force microscopy (AFM). AFM images revealed a smooth top surface, a uniform height, and sharp edges for both forms of single crystals. Both height and phase images showed crystalline terraces with different step heights for the top surface of Form I. Surface properties of single crystals were evaluated using AFM force measurements. Experimental results indicated that the top surface of Form I single crystals was more hydrophilic than that of Form II. Theoretical calculations predicted a dominant crystal face of (020) for the Form I single crystals and (002) for the Form II ones. The correlations between calculation predictions and experimental results were discussed. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1881,1892, 2005 [source] Synthesis and properties of novel sulfonated polyimides containing binaphthyl groups as proton-exchange membranes for fuel cellsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2007Yuhan Li Abstract A novel sulfonated diamine monomer, 2,2,-bis(p -aminophenoxy)-1,1,-binaphthyl-6,6,-disulfonic acid (BNDADS), was synthesized. A series of sulfonated polyimide copolymers containing 30,80 mol % BNDADS as a hydrophilic component were prepared. The copolymers showed excellent solubility and good film-forming capability. Atomic force microscopy phase images clearly showed hydrophilic/hydrophobic microphase separation. The relationship between the proton conductivity and degree of sulfonation was examined. The sulfonated polyimide copolymer with 60 mol % BNDADS showed higher proton conductivity (0.0945,0.161 S/cm) at 20,80 °C in liquid water. The membranes exhibited methanol permeability from 9 × 10,8 to 5 × 10,7 cm2/s at 20 °C, which was much lower than that of Nafion (2 × 10,6cm2/s). The copolymers were thermally stable up to 300 °C. The sulfonated polyimide copolymers with 30,60 mol % BNDADS showed reasonable mechanical strength; for example, the maximum tensile strength at break of the sulfonated polyimide copolymer with 40 mol % BNDADS was 80.6 MPa under high moisture conditions. The optimum concentration of BNDADS was found to be 60 mol % from the viewpoint of proton conductivity, methanol permeability, and membrane stability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 222,231, 2007 [source] Spatial refractive index measurement of porcine artery using differential phase optical coherence microscopyLASERS IN SURGERY AND MEDICINE, Issue 10 2006Jeehyun Kim PhD Abstract Background and Objectives We describe a methodology to record spatial variation of refractive index of porcine renal artery using differential phase optical coherence microscopy (DP-OCM). Study Design/Materials and Methods The DP-OCM provides quantitative measurement of thin specimen phase retardation and refractive index by measuring optical path-length changes on the order of a few nanometers and with a lateral resolution of 3 µm. The DP-OCM instrumentation is an all-fiber, dual-channel Michelson interferometer constructed using a polarization maintaining (PM) fiber. Results Two-dimensional en face dual-channel phase images are taken over a 150,×,200 µm region on a microscopic slide, and the images are reconstructed by plotting a two-dimensional refractive index map as the OCM beam is moved across the sample. Conclusions Because the DP-OCM can record transient changes in the optical path-length, the system may be used to record quantitative optical path-length alterations of tissue in response to various stimuli. A fiber-based DP-OCM may have the potential to substantially improve in vivo imaging of individual cells for a variety of clinical diagnostics, and monitoring applications. Lasers Surg. Med. © 2006 Wiley-Liss, Inc. [source] Magnetic resonance elastography in the liver at 3 Tesla using a second harmonic approachMAGNETIC RESONANCE IN MEDICINE, Issue 2 2009D.A. Herzka Abstract Magnetic resonance elastography (MRE) using mechanical stimulation has demonstrated diagnostic value and clinical promise in breast, liver, and kidney at 1.5 Tesla (T). However, MRE at 1.5T suffers from long imaging times and would benefit from greater signal-to-noise for more robust postprocessing. We present an MRE sequence modified for liver imaging at 3.0T. To avoid artifacts in the phase images, the sequence maintains a short TE by using a second harmonic approach, including stronger motion encoding gradients, shorter radio frequency pulses and an echo-planar readout. Scan time was decreased by a factor of ,2 relative to 1.5T by using an EPI readout and a higher density sampling of the phase waveform was used to calculate shear stiffness and viscosity. Localized (small region of interest) and global (whole-liver region of interest) measurements in normal healthy subjects compared very favorably with previously published results at 1.5T. There was no significant difference between global and localized measures. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Time-resolved, undersampled projection reconstruction imaging for high-resolution CE-MRA of the distal runoff vesselsMAGNETIC RESONANCE IN MEDICINE, Issue 3 2002J. Du Abstract Imaging of the blood vessels below the knee using contrast-enhanced (CE) MRI is challenging due to the need to coordinate image acquisition and arrival of the contrast in the targeted vessels. Time-resolved acquisitions have been successful in consistently capturing images of the arterial phase of the bolus of contrast agent in the distal extremities. Although time-resolved exams are robust in this respect, higher spatial resolution for the depiction of tight stenoses and the small vessels in the lower leg is desirable. A modification to a high-spatial-resolution T1 -weighted pulse sequence (projection reconstruction-time resolved imaging of contrast kinetics (PR-TRICKS)) that improves the through-plane spatial resolution by a factor of 2 and maintains a high frame rate is presented. The undersampled PR-TRICKS pulse sequence has been modified to double the spatial resolution in the slice direction by acquiring high-spatial-frequency slice data only after first pass of the bolus of contrast agent. The acquisition reported in the present work (PR-hyperTRICKS) has been used to image healthy volunteers and patients with known vascular disease. The temporal resolution was found to be beneficial in capturing arterial phase images in the presence of asymmetric filling of vessels. Magn Reson Med 48:516,522, 2002. © 2002 Wiley-Liss, Inc. [source] Three-dimensional refractive index reconstruction with quantitative phase tomographyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2008N.M. Dragomir Abstract Optical tomography based on quantitative phase microscopy is used to determine nondestructively and with high spatial resolution the three-dimensional (3D) refractive index distributions within optical fiber devices. After obtaining a series of phase images of the fiber as it is rotated around its longitudinal axis at regularly-spaced angular positions, filtered backprojection is used to reconstruct a 3D map of the refractive index. The 3D refractive index distribution of the join region between two fusion spliced optical fibers is reconstructed with accuracy better than 10,3. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [source] Measuring SPIO and Gd contrast agent magnetization using 3,T MRINMR IN BIOMEDICINE, Issue 8 2009Pádraig Cantillon-Murphy Abstract Traditional methods of measuring magnetization in magnetic fluid samples, such as vibrating sample magnetometry (VSM), are typically limited to maximum field strengths of about 1,T. This work demonstrates the ability of MRI to measure the magnetization associated with two commercial MRI contrast agents at 3,T by comparing analytical solutions to experimental imaging results for the field pattern associated with agents in cylindrical vials. The results of the VSM and fitted MRI data match closely. The method represents an improvement over VSM measurements since results are attainable at imaging field strengths. The agents investigated are Feridex, a superparamagnetic iron oxide suspension used primarily for liver imaging, and Magnevist, a paramagnetic, gadolinium-based compound used for tumors, inflammation and vascular lesions. MR imaging of the agents took place in sealed cylindrical vials in the presence of a surrounding volume of deionized water where the effects of the contrast agents had a measurable effect on the water's magnetization in the vicinity of the compartment of contrast agent. A pair of phase images were used to reconstruct a B0 fieldmap. The resultant B0 maps in the water region, corrected for shimming and container edge effects, were used to predict the agent's magnetization at 3,T. The results were compared with the results from VSM measurements up to 1.2,T and close correlation was observed. The technique should be of interest to those seeking quantification of the magnetization associated with magnetic suspensions beyond the traditional scope of VSM. The magnetization needs to be sufficiently strong (Ms , 50 Am2/kg Fe for Feridex and Xm , 5 × 10,5 m3/kg Gd for Magnevist) for a measurable dipole field in the surrounding water. For this reason, the technique is mostly suitable for undiluted agents. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||