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Image Contrast (image + contrast)
Selected AbstractsImage contrast in X-ray reflection interface microscopy: comparison of data with model calculations and simulationsJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2008P. Fenter The contrast mechanism for imaging molecular-scale features on solid surfaces is described for X-ray reflection interface microscopy (XRIM) through comparison of experimental images with model calculations and simulated measurements. Images of elementary steps show that image contrast is controlled by changes in the incident angle of the X-ray beam with respect to the sample surface. Systematic changes in the magnitude and sign of image contrast are asymmetric for angular deviations of the sample from the specular reflection condition. No changes in image contrast are observed when defocusing the condenser or objective lenses. These data are explained with model structure-factor calculations that reproduce all of the qualitative features observed in the experimental data. These results provide new insights into the image contrast mechanism, including contrast reversal as a function of incident angle, the sensitivity of image contrast to step direction (i.e. up versus down), and the ability to maximize image contrast at almost any scattering condition defined by the vertical momentum transfer, Qz. The full surface topography can then, in principle, be recovered by a series of images as a function of incident angle at fixed momentum transfer. Inclusion of relevant experimental details shows that the image contrast magnitude is controlled by the intersection of the reciprocal-space resolution function (i.e. controlled by numerical aperture of the condenser and objective lenses) and the spatially resolved interfacial structure factor of the object being imaged. Together these factors reduce the nominal contrast for a step near the specular reflection condition to a value similar to that observed experimentally. This formalism demonstrates that the XRIM images derive from limited aperture contrast, and explains how non-zero image contrast can be obtained when imaging a pure phase object corresponding to the interfacial topography. [source] T1 -weighted magnetic resonance imaging shows fatty deposition after myocardial infarctionMAGNETIC RESONANCE IN MEDICINE, Issue 5 2007James W. Goldfarb Abstract Pathologic studies have shown an increased lipid content in areas of myocardial infarction (MI). We sought to show the ability of precontrast T1 -weighted MRI to noninvasively detect fat deposition in MI and show its association with infarct age. Thirty-two patients with MI were studied. Precontrast inversion-recovery (IR) cine steady-state free precession (SSFP) imaging was used to generate both fat- and muscle-nulled images to locate areas of fat deposition in the left ventricular (LV) myocardium. Postcontrast delayed hyperenhanced (DHE) imaging was also performed. Image contrast in regions of MI on precontrast images and postcontrast DHE images was measured. The association of image contrast with infarct age was determined by means of correlations and Student's t -test. We found a significant association between infarct age and image contrast in both fat- and muscle-nulled images. Precontrast T1 -weighted MRI is a promising method for detecting myocardial fat deposition in chronic MI, and can be used to assess myocardial infarct age. Magn Reson Med 57:828,834, 2007. © 2007 Wiley-Liss, Inc. [source] Analysis of b -value calculations in diffusion weighted and diffusion tensor imagingCONCEPTS IN MAGNETIC RESONANCE, Issue 1 2005Daniel Güllmar Abstract Diffusion weighted imaging has opened new diagnostic possibilities by using microscopic diffusion of water molecules as a means of image contrast. The directional dependence of diffusion has led to the development of diffusion tensor imaging, which allows us to characterize microscopic tissue geometry. The link between the measured NMR signal and the self-diffusion tensor is established by the so-called b matrices that depend on the gradient's direction, strength, and timing. However, in the calculation of b -matrix elements, the influence of imaging gradients on each element of the b matrix is often neglected. This may cause errors, which in turn leads to an incorrect extraction of diffusion coefficients. In cases where the imaging gradients are high (high spatial resolution), these errors may be substantial. Using a generic pulsed gradient spin-echo (PGSE) imaging sequence, the effects of neglecting the imaging gradients on the b -matrix calculation are demonstrated. By measuring an isotropic phantom with this sequence it can be analytically as well as experimentally shown that large deviations in single b -matrix elements are generated. These deviations are obtained by applying the diffusion weighting in the readout direction of the imaging dimension in combination with relatively large imaging gradients. The systematic errors can be avoided by a full b -matrix calculation considering all the gradients of the sequence or by generating cross-term free signals using the geometric average of two diffusion weighted images with opposite polarity. The importance of calculating the exact b matrices by the proposed methods is based on the fact that more precise diffusion parameters are obtained for extracting correct property maps, such as fractional anisotropy, volume ratio, or conductivity tensor maps. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part A 25A: 53,66, 2005 [source] Affinity-Based Protein Surface Pattern Formation by Ligand Self-Selection from Mixed Protein SolutionsADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Manish Dubey Abstract Photolithographically prepared surface patterns of two affinity ligands (biotin and chloroalkane) specific for two proteins (streptavidin and HaloTag, respectively) are used to spontaneously form high-fidelity surface patterns of the two proteins from their mixed solution. High affinity protein-surface self-selection onto patterned ligands on surfaces exhibiting low non-specific adsorption rapidly yields the patterned protein surfaces. Fluorescence images after protein immobilization show high specificity of the target proteins to their respective surface patterned ligands. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging further supports the chemical specificity of streptavidin and HaloTag for their surface patterned ligands from mixed protein solutions. However, ToF-SIMS did detect some non-specific adsorption of bovine serum albumin, a masking protein present in excess in the adsorbing solutions, on the patterned surfaces. Protein amino acid composition, surface coverage, density, and orientation are important parameters that determine the relative ToF-SIMS fragmentation pattern yields. ToF-SIMS amino acid-derived ion fragment yields summed to produce surface images can reliably determine which patterned surface regions contain bound proteins, but do not readily discriminate between different co-planar protein regions. Principal component analysis (PCA) of these ToF-SIMS data, however, improves discrimination of ions specific to each protein, facilitating surface protein pattern identification and image contrast. [source] Gold Nanocages for Biomedical Applications,ADVANCED MATERIALS, Issue 20 2007E. Skrabalak Abstract Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl4. The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where the optical attenuation caused by blood and soft tissue is essentially negligible. They are also biocompatible and present a well-established surface for easy functionalization. We have tailored the scattering and absorption cross-sections of Au nanocages for use in optical coherence tomography and photothermal treatment, respectively. Our preliminary studies show greatly improved spectroscopic image contrast for tissue phantoms containing Au nanocages. Our most recent results also demonstrate the photothermal destruction of breast cancer cells in vitro by using immuno-targeted Au nanocages as an effective photo-thermal transducer. These experiments suggest that Au nanocages may be a new class of nanometer-sized agents for cancer diagnosis and therapy. [source] Molecular imaging in small animals,roles for micro-CTJOURNAL OF CELLULAR BIOCHEMISTRY, Issue S39 2002Erik L. Ritman Abstract X-ray micro-CT is currently used primarily to generate 3D images of micro-architecture (and the function that can be deduced from it) and the regional distribution of administered radiopaque indicators, within intact rodent organs or biopsies from large animals and humans. Current use of X-ray micro-CT can be extended in three ways to increase the quantitative imaging of molecular transport and accumulation within such specimens. (1) By use of heavy elements, other than the usual iodine, attached to molecules of interest or to surrogates for those molecules. The accumulation of the indicator in the physiological compartments, and the transport to and from such compartments, can be quantitated from the imaged spatial distribution of these contrast agents. (2) The high spatial resolution of conventional X-ray attenuation-based CT images can be used to improve the quantitative nature of radionuclide-based tomographic images (SPECT & PET) by providing correction for attenuation of the emitted gamma rays and the accurate delineation of physiological spaces known to selectively accumulate those indicators. Similarly, other imaging modalities which also localize functions in 2D images (such as histological sections subsequently obtained from the same specimen), can provide a synergistic combination with CT-based 3D microstructure. (3) By increasing the sensitivity and specificity of X-ray CT image contrast by use of methods such as: K-edge subtraction imaging, X-ray fluorescence imaging, imaging of the various types of scattered X-ray and the consequences of the change in the speed of X-rays through different tissues, such as refraction and phase shift. These other methods of X-ray imaging can increase contrast by more than an order of magnitude over that due to conventionally-used attenuation of X-ray. To fully exploit their potentials, much development of radiopaque indicators, scanner hardware and image reconstruction and analysis software will be needed. J. Cell. Biochem. Suppl. 39: 116,124, 2002. © 2002 Wiley-Liss, Inc. [source] 3D flow-independent peripheral vessel wall imaging using T2 -prepared phase-sensitive inversion-recovery steady-state free precessionJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2010Jingsi Xie BS Abstract Purpose: To develop a 3D flow-independent peripheral vessel wall imaging method using T2 -prepared phase-sensitive inversion-recovery (T2PSIR) steady-state free precession (SSFP). Materials and Methods: A 3D T2 -prepared and nonselective inversion-recovery SSFP sequence was designed to achieve flow-independent blood suppression for vessel wall imaging based on T1 and T2 properties of the vessel wall and blood. To maximize image contrast and reduce its dependence on the inversion time (TI), phase-sensitive reconstruction was used to restore the true signal difference between vessel wall and blood. The feasibility of this technique for peripheral artery wall imaging was tested in 13 healthy subjects. Image signal-to-noise ratio (SNR), wall/lumen contrast-to-noise ratio (CNR), and scan efficiency were compared between this technique and conventional 2D double inversion recovery , turbo spin echo (DIR-TSE) in eight subjects. Results: 3D T2PSIR SSFP provided more efficient data acquisition (32 slices and 64 mm in 4 minutes, 7.5 seconds per slice) than 2D DIR-TSE (2,3 minutes per slice). SNR of the vessel wall and CNR between vessel wall and lumen were significantly increased as compared to those of DIR-TSE (P < 0.001). Vessel wall and lumen areas of the two techniques are strongly correlated (intraclass correlation coefficients: 0.975 and 0.937, respectively; P < 0.001 for both). The lumen area of T2PSIR SSFP is slightly larger than that of DIR-TSE (P = 0.008). The difference in vessel wall area between the two techniques is not statistically significant. Conclusion: T2PSIR SSFP is a promising technique for peripheral vessel wall imaging. It provides excellent blood signal suppression and vessel wall/lumen contrast. It can cover a 3D volume efficiently and is flow- and TI-independent. J. Magn. Reson. Imaging 2010;32:399,408. © 2010 Wiley-Liss, Inc. [source] Controlling diffusion of 3He by buffer gases: A structural contrast agent in lung MRIJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2006Rodolfo H. Acosta PhD Abstract Purpose To study the influence of admixing inert buffer gases to laser-polarized 3He in terms of resulting diffusion coefficients and the consequences for image contrast and resolution. Materials and Methods The diffusion coefficient of 3He was altered by admixing buffer gases of various molecular weights (4He, N2, and SF6). The influence of the pulse sequence and the diffusion coefficient on the appearance of MRI of (laser-polarized) gases was analyzed by comparison of basic theoretical concepts with demonstrative experiments. Results Excellent agreement between theoretical description and observed signal in simple gradient echoes was observed. A maximum signal gain can be predicted and was experimentally validated. Images acquired under such conditions revealed improved resolution. The nature and concentration of the admixed gas defines a structural threshold for the observed apparent diffusion coefficient (ADC) as demonstrated with diffusion-weighted MRI on a pig's lung flooded with suitable gas mixtures. Conclusion A novel procedure is proposed to control the diffusion coefficient of gases in MRI by admixture of inert buffer gases. Their molecular mass and concentration enter as additional parameters into the equations that describe structural contrast. This allows for setting a structural threshold up to which structures contribute to the image. For MRI of the lung this enables images of very small structural elements (alveoli) only, or in the other extreme, all airways can be displayed with minimal signal loss due to diffusion. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Real-time MRI of joint movement with trueFISPJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2002Harald H. Quick MSc Abstract Purpose To develop a technique for dynamic magnetic resonance imaging (MRI) of joint motion based on a combination of real-time TrueFISP (fast imaging with steady state precession) imaging with surface radiofrequency (RF) coils. Materials and Methods The metacarpal, elbow, tarsal, and knee joint of five volunteers and the knees of four patients were examined with a real-time TrueFISP sequence during movement of the joints. Results All examined joints could be assessed under dynamic conditions with high image contrast and high temporal resolution. Conclusion Dynamic MRI of joints with TrueFISP is feasible and can provide information supplemental to static joint examinations. J. Magn. Reson. Imaging 2002;15:710,715. © 2002 Wiley-Liss, Inc. [source] Magnetic resonance microscopy at 17.6-Tesla on chicken embryos in vitroJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2001Bianca Hogers PhD Abstract The non-destructive nature and the rapid acquisition of a three-dimensional image makes magnetic resonance microscopy (MRM) very attractive and suitable for functional imaging investigations. We explored the use of an ultra high magnetic field for MRM to increase image quality per image acquisition time. Improved image quality was characterized by a better signal-to-noise ratio (SNR), better image contrast, and higher resolution compared to images obtained at lower magnetic field strengths. Fixed chicken embryos at several stages of development were imaged at 7.0-T (300 MHz) and at 17.6-T (750 MHz). Maximum intensity projection resulted in three-dimensional vascular images with ample detail of the embryonic vasculature. We showed that at 750 MHz frequency, an image with approximately three times better SNR can be obtained by T1 -weighting using a standard gadolinium contrast agent, compared to the same measurement at 300 MHz. The image contrast improved by around 20 percent and the contrast-to-noise ratio improved by almost a factor of 3.5. Smaller blood vessels of the vascular system were identified at the high field, which indicates a better image resolution. Thus, ultra high field is beneficial for MRM and opens new areas for functional imaging research, in particular when SNR, resolution, and contrast are limited by acquisition time. J. Magn. Reson. Imaging 2001;14:83,86. © 2001 Wiley-Liss, Inc. [source] Measurement of flow field in biofilm reactors by 3-D magnetic resonance imagingAICHE JOURNAL, Issue 11 2005Kevin P. Nott Abstract 3-D Magnetic resonance imaging (MRI) was used to measure the flow field of water in a packed-bed column containing Serratia sp. biofilm supported on polyurethane foam, and subsequently to follow a reaction which precipitates lanthanum phosphate on the biofilm. Sensitizing the MR image contrast to the fluid flow along the axis of the bioreactor provided better image-contrast between the foam and fluid compared to that based on MR signal intensity alone. After reaction, that same "velocity contrast" effectively defined the difference between blocked and unblocked regions by distinguishing between regions of flow and no flow. Data acquired during progressive blockage of reactors challenged at two different flow rates accord with reactor theory; thus, the faster flow rate replenished the reactants uniformly, whereas at the slower flow rate the reactants were concentration limited. MRI velocimetry was used to generate data that can be used to model reactors where the efficiency is progressively compromised by blockage due to precipitation. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Angle-resolved photoemission spectroscopy and imaging with a submicrometre probe at the SPECTROMICROSCOPY-3.2L beamline of ElettraJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2010Pavel Dudin The extensive upgrade of the experimental end-station of the SPECTROMICROSCOPY-3.2L beamline at Elettra synchrotron light source is reported. After the upgrade, angle-resolved photoemission spectroscopy from a submicrometre spot and scanning microscopy images monitoring the photoelectron signal inside selected acquisition angle and energy windows can be performed. As a test case, angle-resolved photoemission spectroscopy from single flakes of highly oriented pyrolitic graphite and imaging of the flakes with image contrast owing to rotation of the band dispersion of different flakes are presented. [source] Image contrast in X-ray reflection interface microscopy: comparison of data with model calculations and simulationsJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2008P. Fenter The contrast mechanism for imaging molecular-scale features on solid surfaces is described for X-ray reflection interface microscopy (XRIM) through comparison of experimental images with model calculations and simulated measurements. Images of elementary steps show that image contrast is controlled by changes in the incident angle of the X-ray beam with respect to the sample surface. Systematic changes in the magnitude and sign of image contrast are asymmetric for angular deviations of the sample from the specular reflection condition. No changes in image contrast are observed when defocusing the condenser or objective lenses. These data are explained with model structure-factor calculations that reproduce all of the qualitative features observed in the experimental data. These results provide new insights into the image contrast mechanism, including contrast reversal as a function of incident angle, the sensitivity of image contrast to step direction (i.e. up versus down), and the ability to maximize image contrast at almost any scattering condition defined by the vertical momentum transfer, Qz. The full surface topography can then, in principle, be recovered by a series of images as a function of incident angle at fixed momentum transfer. Inclusion of relevant experimental details shows that the image contrast magnitude is controlled by the intersection of the reciprocal-space resolution function (i.e. controlled by numerical aperture of the condenser and objective lenses) and the spatially resolved interfacial structure factor of the object being imaged. Together these factors reduce the nominal contrast for a step near the specular reflection condition to a value similar to that observed experimentally. This formalism demonstrates that the XRIM images derive from limited aperture contrast, and explains how non-zero image contrast can be obtained when imaging a pure phase object corresponding to the interfacial topography. [source] Quantitative studies of pyrocarbon-coated materials using synchrotron radiationJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2008Poonamlata S. Yadav Phase-contrast imaging provides enhanced image contrast and is important for non-destructive evaluation of structural materials. In this paper, experimental results on in-line phase-contrast imaging using a synchrotron source (ELETTRA, Italy) for objects required in material science applications are discussed. Experiments have been carried out on two types of samples, pyrocarbon-coated zirconia and pyrocarbon-coated alumina microspheres. These have applications in both reactor and industrial fields. The phase-contrast imaging technique is found to be very useful in visualizing and determining the coating thickness of pyrocarbon on zirconia and alumina microspheres. The experiments were carried out at X-ray energies of 16, 18 and 20,keV and different object-to-detector distances. The results describe the contrast values and signal-to-noise ratio for both samples. A comprehensive study was carried out to determine the thickness of the pyrocarbon coating on zirconia and alumina microspheres of diameter 500,µm. The advantages of phase-contrast images are discussed in terms of contrast and resolution, and a comparison is made with absorption images. The results show considerable improvement in contrast with phase-contrast imaging as compared with absorption radiography. [source] Studies of the magnetic structure at the ferromagnet,antiferromagnet interfaceJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001A. Scholl Antiferromagnetic layers are a scientifically challenging component in magnetoelectronic devices, such as magnetic sensors in hard-disk heads, or magnetic random-access memory (RAM) elements. In this paper, it is shown that photoelectron emission microscopy (PEEM) is capable of determining the magnetic structure at the interface of ferromagnets and antiferromagnets with high spatial resolution (down to 20,nm). Dichroism effects at the L edges of the magnetic 3d transition metals, using circularly or linearly polarized soft X-rays from a synchrotron source, give rise to a magnetic image contrast. Images, acquired with the PEEM2 experiment at the Advanced Light Source, show magnetic contrast for antiferromagnetic LaFeO3, microscopically resolving the magnetic domain structure in an antiferromagnetically ordered thin film for the first time. Magnetic coupling between LaFeO3 and an adjacent Co layer results in a complete correlation of their magnetic domain structures. From field-dependent measurements, a unidirectional anisotropy resulting in a local exchange bias of up to 30,Oe in single domains could be deduced. The elemental specificity and the quantitative magnetic sensitivity render PEEM a perfect tool to study magnetic coupling effects in multilayered thin-film samples. [source] Reduction of errors in ASL cerebral perfusion and arterial transit time maps using image de-noisingMAGNETIC RESONANCE IN MEDICINE, Issue 3 2010Jack A. Wells Abstract In this work, the performance of image de-noising techniques for reducing errors in arterial spin labeling cerebral blood flow and arterial transit time estimates is investigated. Simulations were used to show that the established arterial spin labeling cerebral blood flow quantification method exhibits the bias behavior common to nonlinear model estimates, and as a result, the reduction of random errors using image de-noising can improve accuracy. To assess the effect on precision, multiple arterial spin labeling data sets acquired from the rat brain were processed using a variety of common de-noising methods (Wiener filter, anisotropic diffusion filter, gaussian filter, wavelet decomposition, and independent component analyses). The various de-noising schemes were also applied to human arterial spin labeling data to assess the possible extent of structure degradation due to excessive spatial smoothing. The animal experiments and simulated data show that noise reduction methods can suppress both random and systematic errors, improving both the precision and accuracy of cerebral blood flow measurements and the precision of transit time maps. A number of these methods (and particularly independent component analysis) were shown to achieve this aim without compromising image contrast. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] T1 -weighted magnetic resonance imaging shows fatty deposition after myocardial infarctionMAGNETIC RESONANCE IN MEDICINE, Issue 5 2007James W. Goldfarb Abstract Pathologic studies have shown an increased lipid content in areas of myocardial infarction (MI). We sought to show the ability of precontrast T1 -weighted MRI to noninvasively detect fat deposition in MI and show its association with infarct age. Thirty-two patients with MI were studied. Precontrast inversion-recovery (IR) cine steady-state free precession (SSFP) imaging was used to generate both fat- and muscle-nulled images to locate areas of fat deposition in the left ventricular (LV) myocardium. Postcontrast delayed hyperenhanced (DHE) imaging was also performed. Image contrast in regions of MI on precontrast images and postcontrast DHE images was measured. The association of image contrast with infarct age was determined by means of correlations and Student's t -test. We found a significant association between infarct age and image contrast in both fat- and muscle-nulled images. Precontrast T1 -weighted MRI is a promising method for detecting myocardial fat deposition in chronic MI, and can be used to assess myocardial infarct age. Magn Reson Med 57:828,834, 2007. © 2007 Wiley-Liss, Inc. [source] Enhanced T2 contrast for MR histology of the mouse brainMAGNETIC RESONANCE IN MEDICINE, Issue 4 2006Anjum Ali Sharief Abstract A 3D Carr-Purcell-Meiboom-Gill (CPMG) sequence was implemented to obtain enhanced T2 contrast in actively stained (perfusion with fixative and contrast agent) mouse brains at 9.4 T. Short interecho spacing was used to minimize diffusion and susceptibility losses. The sequence produced 16 3D volumes with an interecho spacing of 7 ms for isotropic 43-,-resolution images of the mouse brains in a scan time of 4 hr. To enhance the signal-to-noise ratio (SNR) and contrast, the multiecho frequency domain image contrast (MEFIC) method was applied, resulting in a composite image with T2 -weighted contrast. The high SNR and contrast thus achieved revealed aspects of mouse brain morphology, such as multiple cortical layers, groups of thalamic nuclei, layers of the inferior and superior colliculus, and molecular and granular layers of the cerebellum, with a high degree of definition and contrast that was not previously achieved in T2 -weighted acquisitions at high fields. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Visualization of ,-amyloid plaques in a transgenic mouse model of Alzheimer's disease using MR microscopy without contrast reagentsMAGNETIC RESONANCE IN MEDICINE, Issue 3 2004Sang-Pil Lee Abstract The visualization of ,-amyloid plaque deposition in brain, a key feature of Alzheimer's disease (AD), is important for the evaluation of disease progression and the efficacy of therapeutic interventions. In this study, ,-amyloid plaques in the PS/APP transgenic mouse brain, a model of human AD pathology, were detected using MR microscopy without contrast reagents. ,-Amyloid plaques were clearly visible in the cortex, thalamus, and hippocampus of fixed brains of PS/APP mice. The distribution of plaques identified by MRI was in excellent agreement with those found in the immunohistological analysis of the same brain sections. It was also demonstrated that image contrast for ,-amyloid plaques was present in freshly excised nonfixed brains. Furthermore, the detection of ,-amyloid plaques was achieved with a scan time as short as 2 hr, approaching the scan time considered reasonable for in vivo imaging. Magn Reson Med 52:538,544, 2004. © 2004 Wiley-Liss, Inc. [source] Complementary displacement-encoded MRI for contrast-enhanced infarct detection and quantification of myocardial function in miceMAGNETIC RESONANCE IN MEDICINE, Issue 4 2004Wesley D. Gilson Abstract MRI is emerging as an important modality for assessing myocardial function in transgenic and knockout mouse models of cardiovascular disease, including myocardial infarction (MI). Displacement encoding with stimulated echoes (DENSE) measures myocardial motion at high spatial resolution using phase-reconstructed images. The current DENSE technique uses inversion recovery (IR) to suppress T1 -relaxation artifacts; however, IR is ill-suited for contrast-enhanced infarct imaging in the heart, where multiple T1 values are observed. We have developed a modified DENSE method employing complementary acquisitions for T1 -independent artifact suppression. With this technique, displacement and strain are measured in phase-reconstructed images, and contrast-enhanced regions of infarction are depicted in perfectly coregistered magnitude-reconstructed images. The displacement measurements and T1 -weighted image contrast were validated with the use of a rotating phantom. Modified DENSE was performed in mice (N = 9) before and after MI. Circumferential (Ecc) and radial (Err) strain were measured, and contrast-enhanced infarcted myocardium was detected by DENSE. At baseline, Ecc was ,0.16 ± 0.01 and Err was 0.39 ± 0.07. After MI, Ecc was 0.04 ± 0.02 and Err was 0.03 ± 0.04 in infarcted regions, whereas Ecc was ,0.12 ± 0.02 and Err was 0.38 ± 0.09 in noninfarcted regions. In vivo Ecc as determined by DENSE correlated well with Ecc obtained by conventional tag analysis (R = 0.90). Magn Reson Med 51:744,752, 2004. © 2004 Wiley-Liss, Inc. [source] Comparison of new sequences for high-resolution cartilage imagingMAGNETIC RESONANCE IN MEDICINE, Issue 4 2003Brian A. Hargreaves Abstract The high prevalence of osteoarthritis continues to demand improved accuracy in detecting cartilage injury and monitoring its response to different treatments. MRI is the most accurate noninvasive method of diagnosing cartilage lesions. However, MR imaging of cartilage is limited by scan time, signal-to-noise ratio (SNR), and image contrast. Recently, there has been renewed interest in SNR-efficient imaging sequences for imaging cartilage, including various forms of steady-state free-precession as well as driven-equilibrium imaging. This work compares several of these sequences with existing methods, both theoretically and in normal volunteers. Results show that the new steady-state methods increase SNR-efficiency by as much as 30% and improve cartilage-synovial fluid contrast by a factor of three. Additionally, these methods markedly decrease minimum scan times, while providing 3D coverage without the characteristic blurring seen in fast spin-echo images. Magn Reson Med 49:700,709, 2003. © 2003 Wiley-Liss, Inc. [source] IR-SE and IR-MEMRI allow in vivo visualization of oscine neuroarchitecture including the main forebrain regions of the song control systemNMR IN BIOMEDICINE, Issue 1 2006Ilse Tindemans Abstract Songbirds share with humans the capacity to produce learned vocalizations (song). Recently, two major regions within the songbird's neural substrate for song learning and production; nucleus robustus arcopallii (RA) and area X (X) are visualized in vivo using Manganese Enhanced MRI (MEMRI). The aim of this study is to extend this to all main interconnected forebrain Song Control Nuclei. The ipsilateral feedback circuits allow Mn2+ to reach all main Song Control Nuclei after stereotaxic injection of very small doses of MnCl2 (10,nl of 10,mM) into HVC of one and MAN (nucleus magnocellularis nidopallii anterioris) of the other hemisphere. Application of a high resolution (80,µ) Spin Echo Inversion Recovery sequence instead of conventional T1-weighted Spin Echo images improves the image contrast dramatically such that some Song Control Nuclei, ventricles, several laminae, fibre tracts and other specific brain regions can be discerned. The combination of this contrast-rich IR-SE sequence with the transsynaptic transport property of Manganese (Inversion Recovery based MEMRI (IR-MEMRI)) enables the visualization of all main interconnected components of the Song Control System in telencephalon and thalamus. Copyright © 2006 John Wiley & Sons, Ltd. [source] Glare susceptibility test results correlate with temporal safety margin when executing turns across approaching vehicles in simulated low-sun conditionsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2007Rob Gray Abstract The purpose of this study was to compare the results of a laboratory glare susceptibility test with the execution of turns at an intersection (turns that required the driver to cross a lane containing approaching traffic). We measured glare susceptibility by means of low and high-contrast letter charts with and without a glare source. Driving performance in the absence and presence of simulated low sun was assessed using a simulator. In particular, we measured the difference between the time taken to complete a turn across the path of an approaching vehicle and the time to collision (TTC) with the approaching vehicle (the safety margin). The presence of glare resulted in a significant reduction in the safety margin used by drivers (by 0.65 s on average) and the mean number of collisions was significantly higher in the glare conditions than in the non-glare conditions. The effect of glare was larger for low-contrast than for high-contrast oncoming vehicles. Older drivers (45,60 years) had a significantly greater reduction in safety margin than younger drivers (19,29 years), though there was a large inter-individual variability in both age groups. We suggest that the reduction in retinal image contrast caused by low-sun caused drivers to overestimate the TTC with approaching vehicles. [source] Supplementation with the carotenoids lutein or zeaxanthin improves human visual performanceOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2006Jessica Kvansakul Abstract Background:, Macular pigment (MP) is found in diurnal primate species when vision spans a range of ambient illumination and is mediated by cone and rod photoreceptors. The exact role of MP remains to be determined. In this study we investigate two new hypotheses for possible MP functions. Objective:, As MP absorption coincides partly with that of rhodopsin, MP may reduce rod signal effectiveness in the mesopic range, thus extend the usefulness of cone-mediated vision into the mesopic range. Forward light scatter in the eye can reduce retinal image contrast. If blue light contributes significantly to intraocular scatter, selective blue light absorption by MP could reduce the effects of scatter. Design:, We investigated 34 subjects from a carotenoid supplementation trial. The measurements included high mesopic contrast acuity thresholds (CATs), macular pigment optical density (MPOD), wavefront aberrations, and scattered light. The measurements were made after 6 months of daily supplementation with zeaxanthin (Z, OPTISHARPÔ), lutein (L), a combination of the two (C), or placebo (P), and again after a further 6 months of doubled supplementation. Results:, The data reveal a trend toward lower CATs in all groups supplemented, with a statistically significant improvement in the lutein group (p = 0.001), although there was no correlation with MPOD. Light scattering in the eye and the root-mean-square wavefront aberrations show decreasing trends as a result of supplementation, but no correlation with MPOD. Conclusions:, The results suggest that supplementation with L or Z increases MPOD at the fovea and at 2.5°, and that supplementation can improve CATs at high mesopic levels and hence visual performance at low illumination. [source] Pretargeted radioimmunoscintigraphy in patients with primary colorectal cancer using a bispecific anticarcinoembryonic antigen CEA X anti-di-diethylenetriaminepentaacetic acid F(ab,)2 antibody,,CANCER, Issue S4 2010Frits Aarts PhD Abstract BACKGROUND: Antibody-based imaging agents are available commercially, but their success has been limited, mainly because of low contrast and the emergence of 2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) scanning. In pretargeting, administration of the radionuclide is separated from the antibody, thereby enhancing image contrast and allowing detection at earlier time points after injection. METHODS: The authors conducted an open-label, single-arm trial that assessed a pretargeting procedure in which an anticarcinoembryonic antigen x (anti-CEA x) anti-diethylenetriaminepentaacetic acid (anti-DTPA)-indum (In) antibody was used in combination with a 111In-labeled di-DTPA peptide for the diagnostic imaging of CEA-expressing colorectal cancer. Three patients received the 111In peptide alone to investigate tumor targeting, organ distribution, and clearance of the peptide. Thereafter, 11 patients received the bispecific antibody (bsAb) (5 mg) to pretarget the tumor. After 3 to 5 days, patients were injected with 185 megabecquerels of 111In-labeled peptide to assess the optimal interval for best image quality. RESULTS: Fourteen patients with primary colorectal cancer were enrolled. One of 3 patients who received 111In peptide alone had low-level tumor uptake. In 9 of 11 other patients, tumors were observed. In 1 patient, FDG-PET,positive lymph nodes were observed clearly with pretargeted immunoscintigraphy. Peptide pharmacokinetics revealed enhanced circulating levels of 111In-labeled peptide in patients in the 3-day interval cohort compared with the other cohorts. Tumor-to-background ratios ranged from 3.5 to 6.4 in the 3-day interval group, from 5.1 to 14.2 in the 4-day interval group, and from 3.5 to 3.9 in the 5-day interval group. The best images were acquired with a 4-day interval at 24 hours after injection of the radiolabeled peptide. Grade 1 adverse events were observed in 2 patients. CONCLUSIONS: Imaging of colorectal cancer using a 2-step, pretargeting system produced the best imaging results 24 hours after peptide administration using a 4-day interval between injection of the bsAb and the peptide. Cancer 2010;116(4 suppl):1111,7. © 2010 American Cancer Society. [source] 2114: AO adapted to SD-OCTACTA OPHTHALMOLOGICA, Issue 2010W DREXLER Purpose Optical coherence tomography (OCT) has emerged as a leading technique in ophthalmic imaging due to its capability to non-invasively resolve tissue morphology with high sensitivity and high axial resolution. Despite increases in axial resolution, monochromatic ocular aberrations limited the transverse resolution for retinal imaging to ~20 ,m, which is too large for visualization of cellular structures. Adaptive optics (AO) may be used to correct such aberrations, leading to an improvement in image contrast and lateral resolution. Methods A successful combination of ultra-high speed (120,000 depth scans/s), ultra-high resolution optical coherence tomography with adaptive optics and an achromatizing lens for compensation of monochromatic and longitudinal chromatic ocular aberrations, respectively, allows for non-invasive volumetric imaging in normal and pathologic human retinas at cellular resolution. Results The capability of this imaging system is demonstrated through preliminary studies by probing cellular intraretinal structures that have not been accessible so far with in vivo, non-invasive, label-free imaging techniques, including pigment epithelial cells, micro-vasculature of the choriocapillaris, single nerve fibre bundles and collagenous plates of the lamina cribrosa in the optic nerve head. In addition, the volumetric extent of cone loss in two colour-blinds can be quantified for the first time. Conclusion AO OCT might provide opportunities to enhance the understanding of retinal pathogenesis and early diagnosis of retinal diseases. Commercial interest [source] IMAGING LUNG AERATION AND LUNG LIQUID CLEARANCE AT BIRTH USING PHASE CONTRAST X-RAY IMAGINGCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1 2009Stuart B Hooper SUMMARY 1The transition to extra-uterine life at birth is critically dependent on airway liquid clearance to allow the entry of air and the onset of gaseous ventilation. We have used phase contrast X-ray imaging to identify factors that regulate lung aeration at birth in spontaneously breathing term and mechanically ventilated preterm rabbit pups. 2Phase contrast X-ray imaging exploits the difference in refractive index between air and water to enhance image contrast, enabling the smallest air-filled structures of the lung (alveoli; < 100 µm) to be resolved. Using this technique, the lungs become visible as they aerate, allowing the air,liquid interface to be observed as it moves distally during lung aeration. 3Spontaneously breathing term rabbit pups rapidly aerate their lungs, with most fully recruiting their functional residual capacity (FRC) within the first few breaths. The increase in FRC occurs mainly during individual breaths, demonstrating that airway liquid clearance and lung aeration is closely associated with inspiration. We suggest that transpulmonary pressures generated by inspiration provide a hydrostatic pressure gradient for the movement of water out of the airways and into the surrounding lung tissue after birth. 4In mechanically ventilated preterm pups, lung aeration is closely associated with lung inflation and a positive end-expiratory pressure is required to generate and maintain FRC after birth. 5In summary, phase contrast X-ray imaging can image the air-filled lung with high temporal and spatial resolution and is ideal for identifying factors that regulate lung aeration at birth in both spontaneously breathing term and mechanically ventilated preterm neonates. [source] Photolithography: Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved Surfaces (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Mater. The front cover image shows a photolithographically defined gold pattern on the curved surface of a cylindrical glass lens (12.5-mm radius) using a photomask made by using the soft lithography protocols reported by Bowen and Nuzzo on page 3243. The described methods provide highly flexible photomasks, of both positive and negative image contrasts, that serve as amplitude masks for large area photolithographic patterning on a variety of curved (and planar) surfaces. [source] | ||||||||||||||||