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Sample records for imaging contrast based

  1. Complex dark-field contrast in grating-based x-ray phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Tang, Xiangyang

    2015-03-01

    Without assuming that the sub-pixel microstructures of an object to be imaged distribute in space randomly, we investigate the influence of the object's microstructures on grating-based x-ray phase contrast imaging. Our theoretical analysis and 3D computer simulation study based on the paraxial Fresnel-Kirchhoff theory show that the existing dark-field contrast can be generalized into a complex dark-field contrast in a way such that its imaginary part quantifies the effect of the object's sub-pixel microstructures on the phase of intensity oscillations. A method based on the phase-attenuation duality that holds for soft tissues to be imaged at high x-ray energies is proposed to retrieve the imaginary part of the complex dark-field contrast for imaging. In comparison to the existing dark-field contrast, the imaginary part of complex dark-field contrast exhibits significantly stronger selectivity on the shape of the object's sub-pixel microstructures. Thus the x-ray imaging corresponding to the imaginary part of complex dark-field contrast can provide additional and complementary information to that corresponding to the attenuation contrast, phase contrast and the existing dark-field contrast.

  2. Grid-Based Fourier Transform Phase Contrast Imaging

    NASA Astrophysics Data System (ADS)

    Tahir, Sajjad

    Low contrast in x-ray attenuation imaging between different materials of low electron density is a limitation of traditional x-ray radiography. Phase contrast imaging offers the potential to improve the contrast between such materials, but due to the requirements on the spatial coherence of the x-ray beam, practical implementation of such systems with tabletop (i.e. non-synchrotron) sources has been limited. One recently developed phase imaging technique employs multiple fine-pitched gratings. However, the strict manufacturing tolerances and precise alignment requirements have limited the widespread adoption of grating-based techniques. In this work, we have investigated a technique recently demonstrated by Bennett et al. that utilizes a single grid of much coarser pitch. Our system consisted of a low power 100 microm spot Mo source, a CCD with 22 microm pixel pitch, and either a focused mammography linear grid or a stainless steel woven mesh. Phase is extracted from a single image by windowing and comparing data localized about harmonics of the grid in the Fourier domain. A Matlab code was written to perform the image processing. For the first time, the effects on the diffraction phase contrast and scattering amplitude images of varying grid types and periods, and of varying the window function type used to separate the harmonics, and the window widths, were investigated. Using the wire mesh, derivatives of the phase along two orthogonal directions were obtained and new methods investigated to form improved phase contrast images.

  3. Mesh-based phase contrast Fourier transform imaging

    NASA Astrophysics Data System (ADS)

    Tahir, Sajjad; Bashir, Sajid; MacDonald, C. A.; Petruccelli, Jonathan C.

    2017-04-01

    Traditional x-ray radiography is limited by low attenuation contrast in materials of low electron density. Phase contrast imaging offers the potential to improve the contrast between such materials, but due to the requirements on the spatial coherence of the x-ray beam, practical implementation of such systems with tabletop (i.e. non-synchrotron) sources has been limited. One phase imaging technique employs multiple fine-pitched gratings. However, the strict manufacturing tolerances and precise alignment requirements have limited the widespread adoption of grating-based techniques. In this work, we have investigated a recently developed technique that utilizes a single grid of much coarser pitch. Our system consisted of a low power 100 μm spot Mo source, a CCD with 22 μm pixel pitch, and either a focused mammography linear grid or a stainless steel woven mesh. Phase is extracted from a single image by windowing and comparing data localized about harmonics of the mesh in the Fourier domain. The effects on the diffraction phase contrast and scattering amplitude images of varying grid types and periods, and of varying the width of the window function used to separate the harmonics were investigated. Using the wire mesh, derivatives of the phase along two orthogonal directions were obtained and combined to form improved phase contrast images.

  4. [Gadolinium-based contrast agents for magnetic resonance imaging].

    PubMed

    Carrasco Muñoz, S; Calles Blanco, C; Marcin, Javier; Fernández Álvarez, C; Lafuente Martínez, J

    2014-06-01

    Gadolinium-based contrast agents are increasingly being used in magnetic resonance imaging. These agents can improve the contrast in images and provide information about function and metabolism, increasing both sensitivity and specificity. We describe the gadolinium-based contrast agents that have been approved for clinical use, detailing their main characteristics based on their chemical structure, stability, and safety. In general terms, these compounds are safe. Nevertheless, adverse reactions, the possibility of nephrotoxicity from these compounds, and the possibility of developing nephrogenic systemic fibrosis will be covered in this article. Lastly, the article will discuss the current guidelines, recommendations, and contraindications for their clinical use, including the management of pregnant and breast-feeding patients.

  5. Image contrast enhancement based on a local standard deviation model

    SciTech Connect

    Chang, Dah-Chung; Wu, Wen-Rong

    1996-12-31

    The adaptive contrast enhancement (ACE) algorithm is a widely used image enhancement method, which needs a contrast gain to adjust high frequency components of an image. In the literature, the gain is usually inversely proportional to the local standard deviation (LSD) or is a constant. But these cause two problems in practical applications, i.e., noise overenhancement and ringing artifact. In this paper a new gain is developed based on Hunt`s Gaussian image model to prevent the two defects. The new gain is a nonlinear function of LSD and has the desired characteristic emphasizing the LSD regions in which details are concentrated. We have applied the new ACE algorithm to chest x-ray images and the simulations show the effectiveness of the proposed algorithm.

  6. A nonlinear image contrast sharpening approach based on Munsell's scale.

    PubMed

    Matz, Sean C; de Figueiredo, Rui J P

    2006-04-01

    Contrast is a measure of the variation in intensity or gray value in a specified region of an image. The region can be most or all of the image, giving rise to a global concept of contrast. The region might, on the other hand, be a small window in which case the concept of contrast is a locally defined expression. In this work, we introduce a nonlinear local contrast enhancement method. This method utilizes the Munsell value scale which is based upon human visual perception. Use of the Munsell value scale allows for the partitioning of the gray scale into ten discrete subintervals. Subsequent local processing occurs within each of these subintervals. Inside each subinterval, this method constructs a contrast enhancement function that is a smooth approximation to the threshold step function and which maps a given subinterval into itself. This function then thresholds the gray values in a subinterval in a smooth manner about a locally computed quantity called the mean edge gray value. By enhancing the contrast in this way, the original shades of gray are preserved. That is, the groupings of the gray values by subinterval are preserved. As a result, no gray value distortion is introduced into the image.

  7. Contrast-based sensorless adaptive optics for retinal imaging.

    PubMed

    Zhou, Xiaolin; Bedggood, Phillip; Bui, Bang; Nguyen, Christine T O; He, Zheng; Metha, Andrew

    2015-09-01

    Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In this study we show, for the first time, contrast-based NS-AO ophthalmoscopy for full-frame in vivo imaging of human and animal eyes. We suggest a robust image quality metric that could be used for any imaging modality, and test its performance against other metrics using (physical) model eyes.

  8. Contrast-based sensorless adaptive optics for retinal imaging

    PubMed Central

    Zhou, Xiaolin; Bedggood, Phillip; Bui, Bang; Nguyen, Christine T.O.; He, Zheng; Metha, Andrew

    2015-01-01

    Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In this study we show, for the first time, contrast-based NS-AO ophthalmoscopy for full-frame in vivo imaging of human and animal eyes. We suggest a robust image quality metric that could be used for any imaging modality, and test its performance against other metrics using (physical) model eyes. PMID:26417525

  9. Analyser-based phase contrast image reconstruction using geometrical optics.

    PubMed

    Kitchen, M J; Pavlov, K M; Siu, K K W; Menk, R H; Tromba, G; Lewis, R A

    2007-07-21

    Analyser-based phase contrast imaging can provide radiographs of exceptional contrast at high resolution (<100 microm), whilst quantitative phase and attenuation information can be extracted using just two images when the approximations of geometrical optics are satisfied. Analytical phase retrieval can be performed by fitting the analyser rocking curve with a symmetric Pearson type VII function. The Pearson VII function provided at least a 10% better fit to experimentally measured rocking curves than linear or Gaussian functions. A test phantom, a hollow nylon cylinder, was imaged at 20 keV using a Si(1 1 1) analyser at the ELETTRA synchrotron radiation facility. Our phase retrieval method yielded a more accurate object reconstruction than methods based on a linear fit to the rocking curve. Where reconstructions failed to map expected values, calculations of the Takagi number permitted distinction between the violation of the geometrical optics conditions and the failure of curve fitting procedures. The need for synchronized object/detector translation stages was removed by using a large, divergent beam and imaging the object in segments. Our image acquisition and reconstruction procedure enables quantitative phase retrieval for systems with a divergent source and accounts for imperfections in the analyser.

  10. Multifunctional photosensitizer-based contrast agents for photoacoustic imaging.

    PubMed

    Ho, Chris Jun Hui; Balasundaram, Ghayathri; Driessen, Wouter; McLaren, Ross; Wong, Chi Lok; Dinish, U S; Attia, Amalina Binte Ebrahim; Ntziachristos, Vasilis; Olivo, Malini

    2014-06-18

    Photoacoustic imaging is a novel hybrid imaging modality combining the high spatial resolution of optical imaging with the high penetration depth of ultrasound imaging. Here, for the first time, we evaluate the efficacy of various photosensitizers that are widely used as photodynamic therapeutic (PDT) agents as photoacoustic contrast agents. Photoacoustic imaging of photosensitizers exhibits advantages over fluorescence imaging, which is prone to photobleaching and autofluorescence interference. In this work, we examined the photoacoustic activity of 5 photosensitizers: zinc phthalocyanine, protoporphyrin IX, 2,4-bis [4-(N,N-dibenzylamino)-2,6-dihydroxyphenyl] squaraine, chlorin e6 and methylene blue in phantoms, among which zinc phthalocyanine showed the highest photoacoustic activity. Subsequently, we evaluated its tumor localization efficiency and biodistribution at multiple time points in a murine model using photoacoustic imaging. We observed that the probe localized at the tumor within 10 minutes post injection, reaching peak accumulation around 1 hour and was cleared within 24 hours, thus, demonstrating the potential of photosensitizers as photoacoustic imaging contrast agents in vivo. This means that the known advantages of photosensitizers such as preferential tumor uptake and PDT efficacy can be combined with photoacoustic imaging capabilities to achieve longitudinal monitoring of cancer progression and therapy in vivo.

  11. CO2-based in-line phase contrast imaging of small intestine in mice

    NASA Astrophysics Data System (ADS)

    Tang, Rongbiao; Li, Wei-Xia; Huang, Wei; Yan, Fuhua; Chai, Wei-Min; Yang, Guo-Yuan; Chen, Ke-Min

    2013-07-01

    The objective of this study was to explore the potential of CO2 single contrast in-line phase contrast imaging (PCI) for pre-clinical small intestine investigation. The absorption and phase contrast images of CO2 gas production were attained and compared. A further increase in image contrast was observed in PCI. Compared with CO2-based absorption contrast imaging (ACI), CO2-based PCI significantly enhanced the detection of mucosal microstructures, such as pits and folds. The CO2-based PCI could provide sufficient image contrast for clearly showing the intestinal mucosa in living mice without using barium. We concluded that CO2-based PCI might be a novel and promising imaging method for future studies of gastrointestinal disorders.

  12. Analysis of High Contrast Imaging Techniques for Space Based Direct Planetary Imaging

    NASA Technical Reports Server (NTRS)

    Lyon, Richard G.; Gezari, Dan Y.; Nisenson, P.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We report on our ongoing investigations of a number of techniques for direct detection and imaging of Earth-like planets around nearby stellar sources. Herein, we give a quantitative analysis of these techniques and compare and contrast them via computer simulations. The techniques we will be reporting on are Bracewell Interferometry, Nisenson Apodized Square Aperture, and Coronagraphic masking techniques. We parameterize our results with respect to wavelength, aperture size, effects of mirror speckle, both mid- and high-spatial frequency, detector and photon noise as well pointing error. The recent numerous detections of Jupiter and Saturn like planets has driven a resurgence in research of space based high contrast imaging techniques for direct planetary imaging. Work is currently ongoing for concepts for NASA's Terrestrial Planet Finder mission and a number of study teams have been funded. The authors are members of one team.

  13. Feature and contrast enhancement of mammographic image based on multiscale analysis and morphology.

    PubMed

    Wu, Shibin; Yu, Shaode; Yang, Yuhan; Xie, Yaoqin

    2013-01-01

    A new algorithm for feature and contrast enhancement of mammographic images is proposed in this paper. The approach bases on multiscale transform and mathematical morphology. First of all, the Laplacian Gaussian pyramid operator is applied to transform the mammography into different scale subband images. In addition, the detail or high frequency subimages are equalized by contrast limited adaptive histogram equalization (CLAHE) and low-pass subimages are processed by mathematical morphology. Finally, the enhanced image of feature and contrast is reconstructed from the Laplacian Gaussian pyramid coefficients modified at one or more levels by contrast limited adaptive histogram equalization and mathematical morphology, respectively. The enhanced image is processed by global nonlinear operator. The experimental results show that the presented algorithm is effective for feature and contrast enhancement of mammogram. The performance evaluation of the proposed algorithm is measured by contrast evaluation criterion for image, signal-noise-ratio (SNR), and contrast improvement index (CII).

  14. Feature and Contrast Enhancement of Mammographic Image Based on Multiscale Analysis and Morphology

    PubMed Central

    Wu, Shibin; Xie, Yaoqin

    2013-01-01

    A new algorithm for feature and contrast enhancement of mammographic images is proposed in this paper. The approach bases on multiscale transform and mathematical morphology. First of all, the Laplacian Gaussian pyramid operator is applied to transform the mammography into different scale subband images. In addition, the detail or high frequency subimages are equalized by contrast limited adaptive histogram equalization (CLAHE) and low-pass subimages are processed by mathematical morphology. Finally, the enhanced image of feature and contrast is reconstructed from the Laplacian Gaussian pyramid coefficients modified at one or more levels by contrast limited adaptive histogram equalization and mathematical morphology, respectively. The enhanced image is processed by global nonlinear operator. The experimental results show that the presented algorithm is effective for feature and contrast enhancement of mammogram. The performance evaluation of the proposed algorithm is measured by contrast evaluation criterion for image, signal-noise-ratio (SNR), and contrast improvement index (CII). PMID:24416072

  15. X-ray spatial frequency heterodyne imaging of protein-based nanobubble contrast agents.

    PubMed

    Rand, Danielle; Uchida, Masaki; Douglas, Trevor; Rose-Petruck, Christoph

    2014-09-22

    Spatial Frequency Heterodyne Imaging (SFHI) is a novel x-ray scatter imaging technique that utilizes nanoparticle contrast agents. The enhanced sensitivity of this new technique relative to traditional absorption-based x-ray radiography makes it promising for applications in biomedical and materials imaging. Although previous studies on SFHI have utilized only metal nanoparticle contrast agents, we show that nanomaterials with a much lower electron density are also suitable. We prepared protein-based "nanobubble" contrast agents that are comprised of protein cage architectures filled with gas. Results show that these nanobubbles provide contrast in SFHI comparable to that of gold nanoparticles of similar size.

  16. Phase Contrast Imaging

    SciTech Connect

    Menk, Ralf Hendrik

    2008-11-13

    All standard (medical) x-ray imaging technologies, rely primarily on the amplitude properties of the incident radiation, and do not depend on its phase. This is unchanged since the discovery by Roentgen that the intensity of an x-ray beam, as measured by the exposure on a film, was related to the relative transmission properties of an object. However, recently various imaging techniques have emerged which depend on the phase of the x-rays as well as the amplitude. Phase becomes important when the beam is coherent and the imaging system is sensitive to interference phenomena. Significant new advances have been made in coherent optic theory and techniques, which now promise phase information in medical imaging. The development of perfect crystal optics and the increasing availability of synchrotron radiation facilities have contributed to a significant increase in the application of phase based imaging in materials and life sciences. Unique source characteristics such as high intensity, monochromaticity, coherence and high collimating provide an ideal source for advanced imaging. Phase contrast imaging has been applied in both projection and computed tomography modes, and recent applications have been made in the field of medical imaging. Due to the underlying principle of X-ray detection conventional image receptors register only intensities of wave fields and not their phases. During the last decade basically five different methods were developed that translate the phase information into intensity variations. These methods are based on measuring the phase shift {phi} directly (using interference phenomena), the gradient {nabla}{sub {phi}}, or the Laplacian {nabla}{sup 2}{phi}. All three methods can be applied to polychromatic X-ray sources keeping in mind that the native source is synchrotron radiation, featuring monochromatic and reasonable coherent X-ray beams. Due to the vast difference in the coefficients that are driven absorption and phase effects (factor 1

  17. Infrared and color visible image fusion system based on luminance-contrast transfer technique

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Gong, Wenfeng; Wang, Chensheng

    2012-12-01

    In this paper, an infrared and color image fusion algorithm based on luminance-contrast transfer technique is presented. This algorithm shall operate YCbCr transform on color visible image, and obtain the luminance component. Then, the grey-scale image fusion methods are utilized to fuse the luminance component of visible and infrared images to acquire grey-scale fusion image. After that, the grey-scale fusion image and visible image are fused to form color fusion image based on inversed YCbCr transform. To acquire better details appearance, a natural-sense color transfer fusion algorithm based on reference image is proposed. Furthermore, a real-time infrared/visible image fusion system based on FPGA is realized. Finally, this design and achievement is verified experimentally, and the experimental results show that the system can produce a color fusion image with good image quality and real-time performance.

  18. Bisphosphonate-Based Contrast Agents for Radiological Imaging of Microcalcifications

    DTIC Science & Technology

    2006-03-01

    treatment of patients with bone metastases [5]. Two such commercially available compounds are pamidronate disodium, available as Aredia® from...reaction has superior yield (>70%) to the 18-21% yield for pamidronate - IRDye-78 (LI-COR) conjugation reported previously [6]. Representative images are

  19. [An adaptive ultrasound sound speed optimization based on image contrast analysis].

    PubMed

    Li, Xiaoying; Liu, Dongquan

    2011-12-01

    In order to get real time ultrasound images with clear structure and improved contrast, an adaptive ultrasound sound speed optimization method based on image contrast analysis was investigated. It firstly introduced the dynamic beamforming of ultrasound system, as well as the definition of assumed system's sound speed and the true sound speed propagated in tissues the degrade image quality due to their mismatch was also discussed. After given the pixel gray level value based ultrasound image contrast ratio, the basic idea to precisely estimate the true sound speed for real time system sound speed was proposed. Algorithms have been verified both in tissue-mimicking phantoms with known sound speeds and in vivo ultrasound images, compared with other existing method. The testing results showed that this new method not only produced accurate sound speed for ultrasound image optimization, but also finely met the critical computation requirement for real time applications.

  20. Modified Sigmoid Function Based Gray Scale Image Contrast Enhancement Using Particle Swarm Optimization

    NASA Astrophysics Data System (ADS)

    Verma, Harish Kumar; Pal, Sandeep

    2016-06-01

    The main objective of an image enhancement is to improve eminence by maximizing the information content in the test image. Conventional contrast enhancement techniques either often fails to produce reasonable results for a broad variety of low-contrast and high contrast images, or cannot be automatically applied to different images, because they are parameters dependent. Hence this paper introduces a novel hybrid image enhancement approach by taking both the local and global information of an image. In the present work, sigmoid function is being modified on the basis of contrast of the images. The gray image enhancement problem is treated as nonlinear optimization problem with several constraints and solved by particle swarm optimization. The entropy and edge information is included in the objective function as quality measure of an image. The effectiveness of modified sigmoid function based enhancement over conventional methods namely linear contrast stretching, histogram equalization, and adaptive histogram equalization are better revealed by the enhanced images and further validated by statistical analysis of these images.

  1. Grating-based X-ray phase contrast for biomedical imaging applications.

    PubMed

    Pfeiffer, Franz; Herzen, Julia; Willner, Marian; Chabior, Michael; Auweter, Sigrid; Reiser, Maximilian; Bamberg, Fabian

    2013-09-01

    In this review article we describe the development of grating-based X-ray phase-contrast imaging, with particular emphasis on potential biomedical applications of the technology. We review the basics of image formation in grating-based phase-contrast and dark-field radiography and present some exemplary multimodal radiography results obtained with laboratory X-ray sources. Furthermore, we discuss the theoretical concepts to extend grating-based multimodal radiography to quantitative transmission, phase-contrast, and dark-field scattering computed tomography.

  2. Sensitive segmentation of low-contrast multispectral images based on multiparameter space-resonance imaging method

    NASA Astrophysics Data System (ADS)

    Akhmetshin, Alexander M.; Akhmetshin, Lyudmila G.

    2001-10-01

    A new method of low contrast multispectral, hyperspectral and multiparameter images segmentation is outlined. The one has significant advantage in sensitivity and space resolving power of segmentation in comparison with known methods such as principal component transformation and fuzzy C-means clustering segmentation ones. New method is based on using of two important stages: 1) application virtual long-wave holographic transformation to each separate image of analyzed multispectral sequence (it is needed for increasing sensitivity of further analysis); 2) to each pixel of analyzed multispectral image is compare a virtual nonrecursive digital filter with complex coefficients. The one is characterized by its amplitude-frequency (AFC) and phase-frequency (PFC) characteristics. Information features used for visualization and segmentation are frequencies corresponded to maximum (resonance point) or minimum (antiresonance point) of AFC and group delay function calculated on base PFC. Information possibilities of new method are demonstrated on examples of multispectral remote sensing, various physical nature geophysical fields fusion and multiparameter MRI brain tumor hidden area influence detection.

  3. Beam hardening effects in grating-based x-ray phase-contrast imaging

    SciTech Connect

    Chabior, Michael; Donath, Tilman; David, Christian; Bunk, Oliver; Schuster, Manfred; Schroer, Christian; Pfeiffer, Franz

    2011-03-15

    Purpose: In this work, the authors investigate how beam hardening affects the image formation in x-ray phase-contrast imaging and consecutively develop a correction algorithm based on the results of the analysis. Methods: The authors' approach utilizes a recently developed x-ray imaging technique using a grating interferometer capable of visualizing the differential phase shift of a wave front traversing an object. An analytical description of beam hardening is given, highlighting differences between attenuation and phase-contrast imaging. The authors present exemplary beam hardening artifacts for a number of well-defined samples in measurements at a compact laboratory setup using a polychromatic source. Results: Despite the differences in image formation, the authors show that beam hardening leads to a similar reduction of image quality in phase-contrast imaging as in conventional attenuation-contrast imaging. Additionally, the authors demonstrate that for homogeneous objects, beam hardening artifacts can be corrected by a linearization technique, applicable to all kinds of phase-contrast methods using polychromatic sources. Conclusions: The evaluated correction algorithm is shown to yield good results for a number of simple test objects and can thus be advocated in medical imaging and nondestructive testing.

  4. Characterization of nanoparticle-based contrast agents for molecular magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Shan, Liang; Chopra, Arvind; Leung, Kam; Eckelman, William C.; Menkens, Anne E.

    2012-09-01

    The development of molecular imaging agents is currently undergoing a dramatic expansion. As of October 2011, 4,800 newly developed agents have been synthesized and characterized in vitro and in animal models of human disease. Despite this rapid progress, the transfer of these agents to clinical practice is rather slow. To address this issue, the National Institutes of Health launched the Molecular Imaging and Contrast Agents Database (MICAD) in 2005 to provide freely accessible online information regarding molecular imaging probes and contrast agents for the imaging community. While compiling information regarding imaging agents published in peer-reviewed journals, the MICAD editors have observed that some important information regarding the characterization of a contrast agent is not consistently reported. This makes it difficult for investigators to evaluate and meta-analyze data generated from different studies of imaging agents, especially for the agents based on nanoparticles. This article is intended to serve as a guideline for new investigators for the characterization of preclinical studies performed with nanoparticle-based MRI contrast agents. The common characterization parameters are summarized into seven categories: contrast agent designation, physicochemical properties, magnetic properties, in vitro studies, animal studies, MRI studies, and toxicity. Although no single set of parameters is suitable to define the properties of the various types of contrast agents, it is essential to ensure that these agents meet certain quality control parameters at the preclinical stage, so that they can be used without delay for clinical studies.

  5. Microbubbles as x-ray scattering contrast agents using analyzer-based imaging.

    PubMed

    Arfelli, F; Rigon, L; Menk, R H

    2010-03-21

    Conventional contrast agents utilized in diagnostic radiology are based on x-ray absorption properties; alternative physical principles capable of providing a contrast enhancement in radiographs have never been applied. This study exploits the possibility of using a novel type of contrast media based on x-ray scattering. The contrast agents consist of microbubble echo-enhancing agents, usually applied in ultrasound examinations, which are invisible with conventional x-ray absorption techniques. The experiment was carried out at the medical beamline of the synchrotron radiation laboratory ELETTRA in Trieste, Italy. A flat silicon analyzer crystal typically used for diffraction-enhanced imaging was utilized as a tool for detecting the scattering properties of the contrast agents. In analyzer-based imaging, it is possible to detect the scattering properties of the sample by shifting the analyzer crystal to selected positions of its reflectivity curve. In particular, when the sample consists of a large number of micro-particles an overall effect can be observed. Phantoms containing contrast agents based on microbubbles were imaged at different angular positions of the analyzer crystal. High visibility of the details was demonstrated, and a strong contrast enhancement was measured compared to normal x-ray absorption techniques.

  6. Optimization of propagation-based x-ray phase-contrast tomography for breast cancer imaging

    NASA Astrophysics Data System (ADS)

    Baran, P.; Pacile, S.; Nesterets, Y. I.; Mayo, S. C.; Dullin, C.; Dreossi, D.; Arfelli, F.; Thompson, D.; Lockie, D.; McCormack, M.; Taba, S. T.; Brun, F.; Pinamonti, M.; Nickson, C.; Hall, C.; Dimmock, M.; Zanconati, F.; Cholewa, M.; Quiney, H.; Brennan, P. C.; Tromba, G.; Gureyev, T. E.

    2017-03-01

    The aim of this study was to optimise the experimental protocol and data analysis for in-vivo breast cancer x-ray imaging. Results are presented of the experiment at the SYRMEP beamline of Elettra Synchrotron using the propagation-based phase-contrast mammographic tomography method, which incorporates not only absorption, but also x-ray phase information. In this study the images of breast tissue samples, of a size corresponding to a full human breast, with radiologically acceptable x-ray doses were obtained, and the degree of improvement of the image quality (from the diagnostic point of view) achievable using propagation-based phase-contrast image acquisition protocols with proper incorporation of x-ray phase retrieval into the reconstruction pipeline was investigated. Parameters such as the x-ray energy, sample-to-detector distance and data processing methods were tested, evaluated and optimized with respect to the estimated diagnostic value using a mastectomy sample with a malignant lesion. The results of quantitative evaluation of images were obtained by means of radiological assessment carried out by 13 experienced specialists. A comparative analysis was performed between the x-ray and the histological images of the specimen. The results of the analysis indicate that, within the investigated range of parameters, both the objective image quality characteristics and the subjective radiological scores of propagation-based phase-contrast images of breast tissues monotonically increase with the strength of phase contrast which in turn is directly proportional to the product of the radiation wavelength and the sample-to-detector distance. The outcomes of this study serve to define the practical imaging conditions and the CT reconstruction procedures appropriate for low-dose phase-contrast mammographic imaging of live patients at specially designed synchrotron beamlines.

  7. Optimization of propagation-based x-ray phase-contrast tomography for breast cancer imaging.

    PubMed

    Baran, P; Pacile, S; Nesterets, Y I; Mayo, S C; Dullin, C; Dreossi, D; Arfelli, F; Thompson, D; Lockie, D; McCormack, M; Taba, S T; Brun, F; Pinamonti, M; Nickson, C; Hall, C; Dimmock, M; Zanconati, F; Cholewa, M; Quiney, H; Brennan, P C; Tromba, G; Gureyev, T E

    2017-03-21

    The aim of this study was to optimise the experimental protocol and data analysis for in-vivo breast cancer x-ray imaging. Results are presented of the experiment at the SYRMEP beamline of Elettra Synchrotron using the propagation-based phase-contrast mammographic tomography method, which incorporates not only absorption, but also x-ray phase information. In this study the images of breast tissue samples, of a size corresponding to a full human breast, with radiologically acceptable x-ray doses were obtained, and the degree of improvement of the image quality (from the diagnostic point of view) achievable using propagation-based phase-contrast image acquisition protocols with proper incorporation of x-ray phase retrieval into the reconstruction pipeline was investigated. Parameters such as the x-ray energy, sample-to-detector distance and data processing methods were tested, evaluated and optimized with respect to the estimated diagnostic value using a mastectomy sample with a malignant lesion. The results of quantitative evaluation of images were obtained by means of radiological assessment carried out by 13 experienced specialists. A comparative analysis was performed between the x-ray and the histological images of the specimen. The results of the analysis indicate that, within the investigated range of parameters, both the objective image quality characteristics and the subjective radiological scores of propagation-based phase-contrast images of breast tissues monotonically increase with the strength of phase contrast which in turn is directly proportional to the product of the radiation wavelength and the sample-to-detector distance. The outcomes of this study serve to define the practical imaging conditions and the CT reconstruction procedures appropriate for low-dose phase-contrast mammographic imaging of live patients at specially designed synchrotron beamlines.

  8. Time-domain imaging with quench-based fluorescent contrast agents

    NASA Astrophysics Data System (ADS)

    Akers, Walter J.; Solomon, Metasebya; Sudlow, Gail P.; Berezin, Mikhail; Achilefu, Samuel

    2012-03-01

    Quench-based probes utilize unique characteristics of fluorescence resonance energy transfer (FRET) to enhance contrast upon de-quenching. This mechanism has been used in a variety of molecular probes for imaging of cancer related enzyme activity such as matrix metalloproteinases, cathepsins and caspases. While non-fluorescent upon administration, fluorescence can be restored by separation of donor and acceptor, resulting in higher intensity in the presence of activator. Along with decreased quantum yield, FRET also results in altered fluorescence lifetime. Time-domain imaging can further enhance contrast and information yield from quench-based probes. We present in vivo time-domain imaging for detecting activation of quench-based probes. Quench-based probes utilize unique characteristics of fluorescence resonance energy transfer (FRET) to enhance contrast upon de-quenching. This mechanism has been used in a variety of molecular probes for imaging of cancer related enzyme activity such as matrix metalloproteinases, cathepsins and caspases. While non-fluorescent upon administration, fluorescence can be restored by separation of donor and acceptor, resulting in higher intensity in the presence of activator. Along with decreased quantum yield, FRET also results in altered fluorescence lifetime. Time-domain imaging can further enhance contrast and information yield from quench-based probes. We present in vivo time-domain imaging for detecting activation of quench-based probes. Time-domain diffuse optical imaging was performed to assess the FRET and quenching in living mice with orthotopic breast cancer. Tumor contrast enhancement was accompanied by increased fluorescence lifetime after administration of quenched probes selective for matrix metalloproteinases while no significant change was observed for non-quenched probes for integrin receptors. These results demonstrate the utility of timedomain imaging for detection of cancer-related enzyme activity in vivo.

  9. Cuckoo search algorithm based satellite image contrast and brightness enhancement using DWT-SVD.

    PubMed

    Bhandari, A K; Soni, V; Kumar, A; Singh, G K

    2014-07-01

    This paper presents a new contrast enhancement approach which is based on Cuckoo Search (CS) algorithm and DWT-SVD for quality improvement of the low contrast satellite images. The input image is decomposed into the four frequency subbands through Discrete Wavelet Transform (DWT), and CS algorithm used to optimize each subband of DWT and then obtains the singular value matrix of the low-low thresholded subband image and finally, it reconstructs the enhanced image by applying IDWT. The singular value matrix employed intensity information of the particular image, and any modification in the singular values changes the intensity of the given image. The experimental results show superiority of the proposed method performance in terms of PSNR, MSE, Mean and Standard Deviation over conventional and state-of-the-art techniques.

  10. Quantitative breast tissue characterization using grating-based x-ray phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Willner, M.; Herzen, J.; Grandl, S.; Auweter, S.; Mayr, D.; Hipp, A.; Chabior, M.; Sarapata, A.; Achterhold, K.; Zanette, I.; Weitkamp, T.; Sztrókay, A.; Hellerhoff, K.; Reiser, M.; Pfeiffer, F.

    2014-04-01

    X-ray phase-contrast imaging has received growing interest in recent years due to its high capability in visualizing soft tissue. Breast imaging became the focus of particular attention as it is considered the most promising candidate for a first clinical application of this contrast modality. In this study, we investigate quantitative breast tissue characterization using grating-based phase-contrast computed tomography (CT) at conventional polychromatic x-ray sources. Different breast specimens have been scanned at a laboratory phase-contrast imaging setup and were correlated to histopathology. Ascertained tumor types include phylloides tumor, fibroadenoma and infiltrating lobular carcinoma. Identified tissue types comprising adipose, fibroglandular and tumor tissue have been analyzed in terms of phase-contrast Hounsfield units and are compared to high-quality, high-resolution data obtained with monochromatic synchrotron radiation, as well as calculated values based on tabulated tissue properties. The results give a good impression of the method’s prospects and limitations for potential tumor detection and the associated demands on such a phase-contrast breast CT system. Furthermore, the evaluated quantitative tissue values serve as a reference for simulations and the design of dedicated phantoms for phase-contrast mammography.

  11. Recent advances in synchrotron-based hard x-ray phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Nelson, J.; Holzner, C.; Andrews, J. C.; Pianetta, P.

    2013-12-01

    Ever since the first demonstration of phase contrast imaging (PCI) in the 1930s by Frits Zernike, people have realized the significant advantage of phase contrast over conventional absorption-based imaging in terms of sensitivity to ‘transparent’ features within specimens. Thus, x-ray phase contrast imaging (XPCI) holds great potential in studies of soft biological tissues, typically containing low Z elements such as C, H, O and N. Particularly when synchrotron hard x-rays are employed, the favourable brightness, energy tunability, monochromatic characteristics and penetration depth have dramatically enhanced the quality and variety of XPCI methods, which permit detection of the phase shift associated with 3D geometry of relatively large samples in a non-destructive manner. In this paper, we review recent advances in several synchrotron-based hard x-ray XPCI methods. Challenges and key factors in methodological development are discussed, and biological and medical applications are presented.

  12. Stochastic parallel gradient descent based adaptive optics used for a high contrast imaging coronagraph

    NASA Astrophysics Data System (ADS)

    Dong, Bing; Ren, De-Qing; Zhang, Xi

    2011-08-01

    An adaptive optics (AO) system based on a stochastic parallel gradient descent (SPGD) algorithm is proposed to reduce the speckle noises in the optical system of a stellar coronagraph in order to further improve the contrast. The principle of the SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of the SPGD algorithm is demonstrated by an experimental system featured with a 140-actuator deformable mirror and a Hartmann-Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array (LCA) based coronagraph to improve the contrast. The LCA can modulate the incoming light to generate a pupil apodization mask of any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10-3 to 10-4.5 at an angular distance of 2λ/D after being corrected by SPGD based AO.

  13. A Novel Mouse Segmentation Method Based on Dynamic Contrast Enhanced Micro-CT Images

    PubMed Central

    Yan, Dongmei; Zhang, Zhihong; Luo, Qingming; Yang, Xiaoquan

    2017-01-01

    With the development of hybrid imaging scanners, micro-CT is widely used in locating abnormalities, studying drug metabolism, and providing structural priors to aid image reconstruction in functional imaging. Due to the low contrast of soft tissues, segmentation of soft tissue organs from mouse micro-CT images is a challenging problem. In this paper, we propose a mouse segmentation scheme based on dynamic contrast enhanced micro-CT images. With a homemade fast scanning micro-CT scanner, dynamic contrast enhanced images were acquired before and after injection of non-ionic iodinated contrast agents (iohexol). Then the feature vector of each voxel was extracted from the signal intensities at different time points. Based on these features, the heart, liver, spleen, lung, and kidney could be classified into different categories and extracted from separate categories by morphological processing. The bone structure was segmented using a thresholding method. Our method was validated on seven BALB/c mice using two different classifiers: a support vector machine classifier with a radial basis function kernel and a random forest classifier. The results were compared to manual segmentation, and the performance was assessed using the Dice similarity coefficient, false positive ratio, and false negative ratio. The results showed high accuracy with the Dice similarity coefficient ranging from 0.709 ± 0.078 for the spleen to 0.929 ± 0.006 for the kidney. PMID:28060917

  14. Microbubbles as a scattering contrast agent for grating-based x-ray dark-field imaging.

    PubMed

    Velroyen, A; Bech, M; Malecki, A; Tapfer, A; Yaroshenko, A; Ingrisch, M; Cyran, C C; Auweter, S D; Nikolaou, K; Reiser, M; Pfeiffer, F

    2013-02-21

    In clinically established-absorption-based-biomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.

  15. Feasibility study of hidden flow imaging based on laser speckle technique using multiperspectives contrast images

    NASA Astrophysics Data System (ADS)

    Abookasis, David; Moshe, Tomer

    2014-11-01

    This paper demonstrates the insertion of lens array in the front of a CCD camera in a laser speckle imaging (LSI) like-technique to acquire multiple speckle reflectance projections for imaging blood flow in an intact biological tissue. In some of LSI applications, flow imaging is obtained by thinning or removing of the upper tissue layers to access blood vessels. In contrast, with the proposed approach flow imaging can be achieved while the tissue is intact. In the system, each lens from an hexagonal lens array observed the sample from slightly different perspectives and captured with a CCD camera. In the computer, these multiview raw images are converted to speckled contrast maps. Then, a self-deconvolution shift-and-add algorithm is employed for processing yields high contrast flow information. The method is experimentally validated first with a plastic tube filled with scattering liquid running at different controlled flow rates hidden in a biological tissue and then extensively tested for imaging of cerebral blood flow in an intact rodent head experience different conditions. A total of fifteen mice were used in the experiments divided randomly into three groups as follows: Group 1 (n=5) consisted of injured mice experience hypoxic ischemic brain injury monitored for ~40 min. Group 2 (n=5) injured mice experience anoxic brain injury monitored up to 20 min. Group 3 (n=5) experience functional activation monitored up to ~35 min. To increase tissue transparency and the penetration depth of photons through head tissue layers, an optical clearing method was employed. To our knowledge, this work presents for the first time the use of lens array in LSI scheme.

  16. Microbubbles as a scattering contrast agent for grating-based x-ray dark-field imaging

    NASA Astrophysics Data System (ADS)

    Velroyen, A.; Bech, M.; Malecki, A.; Tapfer, A.; Yaroshenko, A.; Ingrisch, M.; Cyran, C. C.; Auweter, S. D.; Nikolaou, K.; Reiser, M.; Pfeiffer, F.

    2013-02-01

    In clinically established—absorption-based—biomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.

  17. Simulation of single grid-based phase-contrast x-ray imaging (g-PCXI)

    NASA Astrophysics Data System (ADS)

    Lim, H. W.; Lee, H. W.; Cho, H. S.; Je, U. K.; Park, C. K.; Kim, K. S.; Kim, G. A.; Park, S. Y.; Lee, D. Y.; Park, Y. O.; Woo, T. H.; Lee, S. H.; Chung, W. H.; Kim, J. W.; Kim, J. G.

    2017-04-01

    Single grid-based phase-contrast x-ray imaging (g-PCXI) technique, which was recently proposed by Wen et al. to retrieve absorption, scattering, and phase-gradient images from the raw image of the examined object, seems a practical method for phase-contrast imaging with great simplicity and minimal requirements on the setup alignment. In this work, we developed a useful simulation platform for g-PCXI and performed a simulation to demonstrate its viability. We also established a table-top setup for g-PCXI which consists of a focused-linear grid (200-lines/in strip density), an x-ray tube (100-μm focal spot size), and a flat-panel detector (48-μm pixel size) and performed a preliminary experiment with some samples to show the performance of the simulation platform. We successfully obtained phase-contrast x-ray images of much enhanced contrast from both the simulation and experiment and the simulated contract seemed similar to the experimental contrast, which shows the performance of the developed simulation platform. We expect that the simulation platform will be useful for designing an optimal g-PCXI system.

  18. Optimum wavelet based masking for the contrast enhancement of medical images using enhanced cuckoo search algorithm.

    PubMed

    Daniel, Ebenezer; Anitha, J

    2016-04-01

    Unsharp masking techniques are a prominent approach in contrast enhancement. Generalized masking formulation has static scale value selection, which limits the gain of contrast. In this paper, we propose an Optimum Wavelet Based Masking (OWBM) using Enhanced Cuckoo Search Algorithm (ECSA) for the contrast improvement of medical images. The ECSA can automatically adjust the ratio of nest rebuilding, using genetic operators such as adaptive crossover and mutation. First, the proposed contrast enhancement approach is validated quantitatively using Brain Web and MIAS database images. Later, the conventional nest rebuilding of cuckoo search optimization is modified using Adaptive Rebuilding of Worst Nests (ARWN). Experimental results are analyzed using various performance matrices, and our OWBM shows improved results as compared with other reported literature.

  19. Chemical-contrast imaging with pulse-shaping based pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Flynn, Daniel C.; Bhagwat, Amar R.; Ogilvie, Jennifer P.

    2013-02-01

    Ultrafast pump-probe spectroscopy and pulse-shaping techniques are providing new modes of contrast for the field of multiphoton microscopy. Endogenous species such as heme proteins show rich nonlinear spectroscopic signatures of excited state absorption, stimulated emission and ground-state bleaching. Commercially available octave-spanning Ti:sapphire oscillators offer new opportunities for imaging based on pump-probe contrast. Spatial light modulators take advantage of this large bandwidth, shaping pulses of light to selectively excite molecular structures with similar spectral properties. We present two-color pump-probe imaging of heme proteins solutions and red blood cells.

  20. Region of interest extraction based on saliency detection and contrast analysis for remote sensing images

    NASA Astrophysics Data System (ADS)

    Lv, Jing; Zhang, Libao; Wang, Shuang

    2016-10-01

    Region of Interest (ROI) extraction is an important component in remote sensing images processing, which is useful for further practical applications such as image compression, image fusion, image segmentation and image registration. Traditional ROI extraction methods are usually prior knowledge-based and depend on a global searching solution which are time consuming and computational complex. Saliency detection which is widely used for ROI extraction from natural scene images in these years can effectively solve the problem of high computation complexity in ROI extraction for remote sensing images as well as retain accuracy. In this paper, a new computational model is proposed to improve the accuracy of ROI extraction in remote sensing images. Considering the characteristics of remote sensing images, we first use lifting wavelet transform based on adaptive direction evaluation (ADE) to obtain multi-scale orientation contrast feature map (MF). Secondly, the features of color are exploited using the information content analysis to provide a color information map (CIM). Thirdly, feature fusion is used to integrate multi-scale orientation contrast features and color information for generating a saliency map. Finally, an adaptive threshold segmentation algorithm is employed to obtain the ROI. Compared with existing models, our method can not only effectively extract detail of the ROIs, but also effectively remove mistaken detection of the inner parts of the ROIs.

  1. Co-registration and distortion correction of diffusion and anatomical images based on inverse contrast normalization.

    PubMed

    Bhushan, Chitresh; Haldar, Justin P; Choi, Soyoung; Joshi, Anand A; Shattuck, David W; Leahy, Richard M

    2015-07-15

    Diffusion MRI provides quantitative information about microstructural properties which can be useful in neuroimaging studies of the human brain. Echo planar imaging (EPI) sequences, which are frequently used for acquisition of diffusion images, are sensitive to inhomogeneities in the primary magnetic (B0) field that cause localized distortions in the reconstructed images. We describe and evaluate a new method for correction of susceptibility-induced distortion in diffusion images in the absence of an accurate B0 fieldmap. In our method, the distortion field is estimated using a constrained non-rigid registration between an undistorted T1-weighted anatomical image and one of the distorted EPI images from diffusion acquisition. Our registration framework is based on a new approach, INVERSION (Inverse contrast Normalization for VERy Simple registratION), which exploits the inverted contrast relationship between T1- and T2-weighted brain images to define a simple and robust similarity measure. We also describe how INVERSION can be used for rigid alignment of diffusion images and T1-weighted anatomical images. Our approach is evaluated with multiple in vivo datasets acquired with different acquisition parameters. Compared to other methods, INVERSION shows robust and consistent performance in rigid registration and shows improved alignment of diffusion and anatomical images relative to normalized mutual information for non-rigid distortion correction.

  2. High sensitivity phase retrieval method in grating-based x-ray phase contrast imaging

    SciTech Connect

    Wu, Zhao; Gao, Kun; Chen, Jian; Wang, Dajiang; Wang, Shenghao; Chen, Heng; Bao, Yuan; Shao, Qigang; Wang, Zhili; Zhang, Kai; Zhu, Peiping; Wu, Ziyu

    2015-02-15

    Purpose: Grating-based x-ray phase contrast imaging is considered as one of the most promising techniques for future medical imaging. Many different methods have been developed to retrieve phase signal, among which the phase stepping (PS) method is widely used. However, further practical implementations are hindered, due to its complex scanning mode and high radiation dose. In contrast, the reverse projection (RP) method is a novel fast and low dose extraction approach. In this contribution, the authors present a quantitative analysis of the noise properties of the refraction signals retrieved by the two methods and compare their sensitivities. Methods: Using the error propagation formula, the authors analyze theoretically the signal-to-noise ratios (SNRs) of the refraction images retrieved by the two methods. Then, the sensitivities of the two extraction methods are compared under an identical exposure dose. Numerical experiments are performed to validate the theoretical results and provide some quantitative insight. Results: The SNRs of the two methods are both dependent on the system parameters, but in different ways. Comparison between their sensitivities reveals that for the refraction signal, the RP method possesses a higher sensitivity, especially in the case of high visibility and/or at the edge of the object. Conclusions: Compared with the PS method, the RP method has a superior sensitivity and provides refraction images with a higher SNR. Therefore, one can obtain highly sensitive refraction images in grating-based phase contrast imaging. This is very important for future preclinical and clinical implementations.

  3. Noise in x-ray grating-based phase-contrast imaging

    SciTech Connect

    Weber, Thomas; Bartl, Peter; Bayer, Florian; Durst, Juergen; Haas, Wilhelm; Michel, Thilo; Ritter, Andre; Anton, Gisela

    2011-07-15

    Purpose: Grating-based x-ray phase-contrast imaging is a fast developing new modality not only for medical imaging, but as well for other fields such as material sciences. While these many possible applications arise, the knowledge of the noise behavior is essential. Methods: In this work, the authors used a least squares fitting algorithm to calculate the noise behavior of the three quantities absorption, differential phase, and dark-field image. Further, the calculated error formula of the differential phase image was verified by measurements. Therefore, a Talbot interferometer was setup, using a microfocus x-ray tube as source and a Timepix detector for photon counting. Additionally, simulations regarding this topic were performed. Results: It turned out that the variance of the reconstructed phase is only dependent of the total number of photons used to generate the phase image and the visibility of the experimental setup. These results could be evaluated in measurements as well as in simulations. Furthermore, the correlation between absorption and dark-field image was calculated. Conclusions: These results provide the understanding of the noise characteristics of grating-based phase-contrast imaging and will help to improve image quality.

  4. Source effects in analyzer-based X-ray phase contrast imaging with conventional sources

    SciTech Connect

    Hoennicke, M. G.; Manica, J.; Mazzaro, I.; Cusatis, C.; Huang, X.-R.

    2012-11-15

    Several recent papers have shown the implementation of analyzer based X-ray phase contrast imaging (ABI) with conventional X-ray sources. The high flux is always a requirement to make the technique useful for bio-medical applications. Here, we present and discuss three important parameters, which need to be taken into account, when searching for the high flux ABI: anisotropic magnification, double image, and source size spread due to intrinsic dispersive diffraction by asymmetrically cut crystals. These parameters, if not well optimized, may cause important features in the acquired images which can mislead the interpretation. A few ways to minimize these effects are implemented and discussed, including some experimental results.

  5. Source effects in analyzer-based X-ray phase contrast imaging with conventional sources

    NASA Astrophysics Data System (ADS)

    Hönnicke, M. G.; Manica, J.; Mazzaro, I.; Cusatis, C.; Huang, X.-R.

    2012-11-01

    Several recent papers have shown the implementation of analyzer based X-ray phase contrast imaging (ABI) with conventional X-ray sources. The high flux is always a requirement to make the technique useful for bio-medical applications. Here, we present and discuss three important parameters, which need to be taken into account, when searching for the high flux ABI: anisotropic magnification, double image, and source size spread due to intrinsic dispersive diffraction by asymmetrically cut crystals. These parameters, if not well optimized, may cause important features in the acquired images which can mislead the interpretation. A few ways to minimize these effects are implemented and discussed, including some experimental results.

  6. Fractal coding of wavelet image based on human vision contrast-masking effect

    NASA Astrophysics Data System (ADS)

    Wei, Hai; Shen, Lansun

    2000-06-01

    In this paper, a fractal-based compression approach of wavelet image is presented. The scheme tries to make full use of the sensitivity features of the human visual system. With the wavelet-based multi-resolution representation of image, detail vectors of each high frequency sub-image are constructed in accordance with its spatial orientation in order to grasp the edge information to which human observer is sensitive. Then a multi-level selection algorithm based on human vision's contrast masking effect is proposed to make the decision whether a detail vector is coded or not. Those vectors below the contrast threshold are discarded without introducing visual artifacts because of the ignorance of human vision. As for the redundancy of the retained vectors, different fractal- based methods are employed to decrease the correlation in single sub-image and between the different resolution sub- images with the same orientation. Experimental results suggest the efficiency of the proposed scheme. With the standard test image, our approach outperforms the EZW algorithm and the JPEG method.

  7. Multiscale image contrast amplification (MUSICA)

    NASA Astrophysics Data System (ADS)

    Vuylsteke, Pieter; Schoeters, Emile P.

    1994-05-01

    This article presents a novel approach to the problem of detail contrast enhancement, based on multiresolution representation of the original image. The image is decomposed into a weighted sum of smooth, localized, 2D basis functions at multiple scales. Each transform coefficient represents the amount of local detail at some specific scale and at a specific position in the image. Detail contrast is enhanced by non-linear amplification of the transform coefficients. An inverse transform is then applied to the modified coefficients. This yields a uniformly contrast- enhanced image without artefacts. The MUSICA-algorithm is being applied routinely to computed radiography images of chest, skull, spine, shoulder, pelvis, extremities, and abdomen examinations, with excellent acceptance. It is useful for a wide range of applications in the medical, graphical, and industrial area.

  8. A Fusion Algorithm for GFP Image and Phase Contrast Image of Arabidopsis Cell Based on SFL-Contourlet Transform

    PubMed Central

    Feng, Peng; Wang, Jing; Wei, Biao; Mi, Deling

    2013-01-01

    A hybrid multiscale and multilevel image fusion algorithm for green fluorescent protein (GFP) image and phase contrast image of Arabidopsis cell is proposed in this paper. Combining intensity-hue-saturation (IHS) transform and sharp frequency localization Contourlet transform (SFL-CT), this algorithm uses different fusion strategies for different detailed subbands, which include neighborhood consistency measurement (NCM) that can adaptively find balance between color background and gray structure. Also two kinds of neighborhood classes based on empirical model are taken into consideration. Visual information fidelity (VIF) as an objective criterion is introduced to evaluate the fusion image. The experimental results of 117 groups of Arabidopsis cell image from John Innes Center show that the new algorithm cannot only make the details of original images well preserved but also improve the visibility of the fusion image, which shows the superiority of the novel method to traditional ones. PMID:23476716

  9. [Measuring the contrast resolution limits of human vision based on the modern digital image processing].

    PubMed

    Wang, Zhifang; Liu, Yuhong; Wang, Ying; Li, Hong; Li, Zhangyong; Zhao, Zhiqiang; Xie, Zhengxiang

    2008-10-01

    In the literatures on the human vision physiology and physics, there were reports about space resolution limit of 1' visual angle, frequency resolution limit of 5 nm and time resolution limit of 0.1" of human vision. However, there has been no report about the contrast resolution limit of human vision,especially the report of measuring method and result about the contrast resolution limit of human vision based on the modern digital image processing. Here we report a modern method for measuring the contrast resolution limit of human vision based on computer digital image processing technology, and we present the measured results and their mathematical models. The function relationships of contrast resolution limit varying with background gray in a photopic or a scotopic sights were illuminated respectively. It can be expected that such investigations with regard to human vision will establish the physiological foundation of the theories and techniques in hiding bodies and hiding figures (stealth), in anti-hiding bodies and anti-hiding figures, in the night vision system independent of infrared, as well as in their relative industries.

  10. Development of Ultrasound-switchable Fluorescence Imaging Contrast Agents based on Thermosensitive Polymers and Nanoparticles

    PubMed Central

    Cheng, Bingbing; Wei, Ming-Yuan; Liu, Yuan; Pitta, Harish; Xie, Zhiwei; Hong, Yi; Nguyen, Kytai T.; Yuan, Baohong

    2015-01-01

    In this work we first introduced a recently developed high-resolution, deep-tissue imaging technique, ultrasound-switchable fluorescence (USF). The imaging principles based on two types of USF contrast agents were reviewed. To improve USF imaging techniques further, excellent USF contrast agents were developed based on high-performance thermoresponsive polymers and environment-sensitive fluorophores. Herein, such contrast agents were synthesized and characterized with five key parameters: (1) peak excitation and emission wavelengths (λex and λem), (2) the fluorescence intensity ratio between on and off states (IOn/IOff), (3) the fluorescence lifetime ratio between on and off states (τOn/τOff), (4) the temperature threshold to switch on fluorophores (Tth), and (5) the temperature transition bandwidth (TBW). We mainly investigated fluorescence intensity and lifetime changes of four environment-sensitive dyes [7-(2-Aminoethylamino)-N,N-dimethyl-4-benzofurazansulfonamide (DBD-ED), St633, Sq660, and St700] as a function of temperature, while the dye was attached to poly(N-isopropylacrylamide) linear polymers or encapsulated in nanoparticles. Six fluorescence resonance energy transfer systems were invented in which both the donor (DBD-ED or ST425) and the acceptor (Sq660) were adopted. Our results indicate that three Förster resonance energy transfer systems, where both IOn/IOff and τOn/τOff are larger than 2.5, are promising for application in future surface tissue bioimaging by USF technique. PMID:26052192

  11. Simulation tools for analyzer-based x-ray phase contrast imaging system with a conventional x-ray source

    NASA Astrophysics Data System (ADS)

    Caudevilla, Oriol; Zhou, Wei; Stoupin, Stanislav; Verman, Boris; Brankov, J. G.

    2016-09-01

    Analyzer-based X-ray phase contrast imaging (ABI) belongs to a broader family of phase-contrast (PC) X-ray imaging modalities. Unlike the conventional X-ray radiography, which measures only X-ray absorption, in PC imaging one can also measures the X-rays deflection induced by the object refractive properties. It has been shown that refraction imaging provides better contrast when imaging the soft tissue, which is of great interest in medical imaging applications. In this paper, we introduce a simulation tool specifically designed to simulate the analyzer-based X-ray phase contrast imaging system with a conventional polychromatic X-ray source. By utilizing ray tracing and basic physical principles of diffraction theory our simulation tool can predicting the X-ray beam profile shape, the energy content, the total throughput (photon count) at the detector. In addition we can evaluate imaging system point-spread function for various system configurations.

  12. Analysis of a deconvolution-based information retrieval algorithm in X-ray grating-based phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Horn, Florian; Bayer, Florian; Pelzer, Georg; Rieger, Jens; Ritter, André; Weber, Thomas; Zang, Andrea; Michel, Thilo; Anton, Gisela

    2014-03-01

    Grating-based X-ray phase-contrast imaging is a promising imaging modality to increase soft tissue contrast in comparison to conventional attenuation-based radiography. Complementary and otherwise inaccessible information is provided by the dark-field image, which shows the sub-pixel size granularity of the measured object. This could especially turn out to be useful in mammography, where tumourous tissue is connected with the presence of supertiny microcalcifications. In addition to the well-established image reconstruction process, an analysis method was introduced by Modregger, 1 which is based on deconvolution of the underlying scattering distribution within a single pixel revealing information about the sample. Subsequently, the different contrast modalities can be calculated with the scattering distribution. The method already proved to deliver additional information in the higher moments of the scattering distribution and possibly reaches better image quality with respect to an increased contrast-to-noise ratio. Several measurements were carried out using melamine foams as phantoms. We analysed the dependency of the deconvolution-based method with respect to the dark-field image on different parameters such as dose, number of iterations of the iterative deconvolution-algorithm and dark-field signal. A disagreement was found in the reconstructed dark-field values between the FFT method and the iterative method. Usage of the resulting characteristics might be helpful in future applications.

  13. Surface impedance based microwave imaging method for breast cancer screening: contrast-enhanced scenario.

    PubMed

    Güren, Onan; Çayören, Mehmet; Ergene, Lale Tükenmez; Akduman, Ibrahim

    2014-10-07

    A new microwave imaging method that uses microwave contrast agents is presented for the detection and localization of breast tumours. The method is based on the reconstruction of breast surface impedance through a measured scattered field. The surface impedance modelling allows for representing the electrical properties of the breasts in terms of impedance boundary conditions, which enable us to map the inner structure of the breasts into surface impedance functions. Later a simple quantitative method is proposed to screen breasts against malignant tumours where the detection procedure is based on weighted cross correlations among impedance functions. Numerical results demonstrate that the method is capable of detecting small malignancies and provides reasonable localization.

  14. Tissue sensitive imaging and tomography without contrast agents for small animals with Timepix based detectors

    NASA Astrophysics Data System (ADS)

    Trojanova, E.; Schyns, L. E. J. R.; Ludwig, D.; Jakubek, J.; Le Pape, A.; Sefc, L.; Lotte, S.; Sykora, V.; Turecek, D.; Uher, J.; Verhaegen, F.

    2017-01-01

    The tissue type resolving X-ray radiography and tomography can be performed even without contrast agents. The differences between soft tissue types such as kidney, muscles, fat, liver, brain and spleen were measured based on their spectral response. The Timepix based X-ray imaging detector WidePIX2×5 with 300 μm thick silicon sensors was used for most of the measurements presented in this work. These promising results are used for further optimizations of the detector technology and radiographic methods.

  15. Design of water-based ferrofluids as contrast agents for magnetic resonance imaging.

    PubMed

    Casula, Maria F; Corrias, Anna; Arosio, Paolo; Lascialfari, Alessandro; Sen, Tapas; Floris, Patrizia; Bruce, Ian J

    2011-05-01

    We report the synthesis, characterization and relaxometric study of ferrofluids based on iron oxide, with potential for use as magnetic resonance imaging (MRI) contrast agents (CAs). The effect of different cost-effective, water-based surface modification approaches which can be easily scaled-up for the large scale synthesis of the ferrofluids has been investigated. Surface modification was achieved by silanization, and/or coating with non-toxic commercial dispersants (a lauric polysorbate and a block copolymer with pigment affinic groups, namely Tween 20 and Disperbyk 190) which were added after or during iron oxide nanoparticle synthesis. It was observed that all the materials synthesized functioned as negative contrast agents at physiological temperature and at frequencies covered by clinical imagers. The relaxometric properties of the magnetic nanoparticles were significantly improved after surface coating with stabilizers compared to the original iron oxide nanoparticles, with particular reference to the silica-coated magnetic nanoparticles. The results indicate that the optimization of the preparation of colloidal magnetic ferrofluids by surface modification is effective in the design of novel contrast agents for MRI by enabling better or more effective interaction between the coated iron oxide nanoparticles and protons present in their aqueous environment.

  16. Lattice and strain analysis of atomic resolution Z-contrast images based on template matching.

    PubMed

    Zuo, Jian-Min; Shah, Amish B; Kim, Honggyu; Meng, Yifei; Gao, Wenpei; Rouviére, Jean-Luc

    2014-01-01

    A real space approach is developed based on template matching for quantitative lattice analysis using atomic resolution Z-contrast images. The method, called TeMA, uses the template of an atomic column, or a group of atomic columns, to transform the image into a lattice of correlation peaks. This is helped by using a local intensity adjusted correlation and by the design of templates. Lattice analysis is performed on the correlation peaks. A reference lattice is used to correct for scan noise and scan distortions in the recorded images. Using these methods, we demonstrate that a precision of few picometers is achievable in lattice measurement using aberration corrected Z-contrast images. For application, we apply the methods to strain analysis of a molecular beam epitaxy (MBE) grown LaMnO₃ and SrMnO₃ superlattice. The results show alternating epitaxial strain inside the superlattice and its variations across interfaces at the spatial resolution of a single perovskite unit cell. Our methods are general, model free and provide high spatial resolution for lattice analysis.

  17. A Robust Range Grating Lobe Suppression Method Based on Image Contrast for Stepped-Frequency SAR

    PubMed Central

    Gao, Wen-Bin; Long, Teng; Ding, Ze-Gang; Wu, Yi-Rong

    2016-01-01

    The magnitude error and phase error (MEPE) in the transfer function of a stepped-frequency synthetic aperture radar (SAR) system results in a periodic MEPE in the synthesized wideband waveform (SWW), which induces the grating lobes in the high-resolution range profile (HRRP). In this paper, a robust data-driven grating lobe suppression (GLS) method is proposed. Based on a contrast-based error estimation method and the grating lobes of the brightest scatterers in the SAR image, the periodic MEPE can be robustly estimated using the proposed method. By compensating the estimated periodic MEPE, the range grating lobes can be suppressed to the background level of the SAR image. Simulation results and real data processing have demonstrated the superiority of the proposed method. PMID:27929411

  18. Analyzer-based phase-contrast imaging system using a micro focus x-ray source

    SciTech Connect

    Zhou, Wei; Majidi, Keivan; Brankov, Jovan G.

    2014-08-15

    Here we describe a new in-laboratory analyzer based phase contrast-imaging (ABI) instrument using a conventional X-ray tube source (CXS) aimed at bio-medical imaging applications. Phase contrast-imaging allows visualization of soft tissue details usually obscured in conventional X-ray imaging. The ABI system design and major features are described in detail. The key advantage of the presented system, over the few existing CXS ABI systems, is that it does not require high precision components, i.e., CXS, X-ray detector, and electro-mechanical components. To overcome a main problem introduced by these components, identified as temperature stability, the system components are kept at a constant temperature inside of three enclosures, thus minimizing the electrical and mechanical thermal drifts. This is achieved by using thermoelectric (Peltier) cooling/heating modules that are easy to control precisely. For CXS we utilized a microfocus X-ray source with tungsten (W) anode material. In addition the proposed system eliminates tungsten's multiple spectral lines by selecting monochromator crystal size appropriately therefore eliminating need for the costly mismatched, two-crystal monochromator. The system imaging was fine-tuned for tungsten Kα{sub 1} line with the energy of 59.3 keV since it has been shown to be of great clinical significance by a number of researchers at synchrotron facilities. In this way a laboratory system that can be used for evaluating and quantifying tissue properties, initially explored at synchrotron facilities, would be of great interest to a larger research community. To demonstrate the imaging capability of our instrument we use a chicken thigh tissue sample.

  19. In-line phase-contrast and grating-based phase-contrast synchrotron imaging study of brain micrometastasis of breast cancer

    NASA Astrophysics Data System (ADS)

    Huang, Sheng; Kou, Binquan; Chi, Yayun; Xi, Yan; Cao, Yixin; Cui, Wenli; Hu, Xin; Shao, Zhimin; Guo, Han; Fu, Yanan; Xiao, Tiqiao; Sun, Jianqi; Zhao, Jun; Wang, Yujie; Wu, Jiong

    2015-03-01

    Current bio-medical imaging researches aim to detect brain micrometastasis in early stage for its increasing incidence and high mortality rates. Synchrotron phase-contrast imaging techniques, such as in-line phase-contrast (IPC) and grating-based phase-contrast (GPC) imaging, could provide a high spatial and density imaging study of biological specimens' 3D structures. In this study, we demonstrated the detection efficiencies of these two imaging tools on breast cancer micrometastasis in an ex vivo mouse brain. We found that both IPC and GPC can differentiate abnormal brain structures induced by micrometastasis from the surrounding normal tissues. We also found that GPC was more sensitive in detecting the small metastasis as compared to IPC.

  20. Model-based pancreas segmentation in portal venous phase contrast-enhanced CT images.

    PubMed

    Hammon, Matthias; Cavallaro, Alexander; Erdt, Marius; Dankerl, Peter; Kirschner, Matthias; Drechsler, Klaus; Wesarg, Stefan; Uder, Michael; Janka, Rolf

    2013-12-01

    This study aims to automatically detect and segment the pancreas in portal venous phase contrast-enhanced computed tomography (CT) images. The institutional review board of the University of Erlangen-Nuremberg approved this study and waived the need for informed consent. Discriminative learning is used to build a pancreas tissue classifier incorporating spatial relationships between the pancreas and surrounding organs and vessels. Furthermore, discrete cosine and wavelet transforms are used to build texture features to describe local tissue appearance. Classification is used to guide a constrained statistical shape model to fit the data. The algorithm to detect and segment the pancreas was evaluated on 40 consecutive CT data that were acquired in the portal venous contrast agent phase. Manual segmentation of the pancreas was carried out by experienced radiologists and served as reference standard. Threefold cross validation was performed. The algorithm-based detection and segmentation yielded an average surface distance of 1.7 mm and an average overlap of 61.2 % compared with the reference standard. The overall runtime of the system was 20.4 min. The presented novel approach enables automatic pancreas segmentation in portal venous phase contrast-enhanced CT images which are included in almost every clinical routine abdominal CT examination. Reliable pancreatic segmentation is crucial for computer-aided detection systems and an organ-specific decision support.

  1. Analyzer-based phase contrast imaging and phase retrieval using a rotating anode x-ray source

    SciTech Connect

    Vine, D. J.; Paganin, D. M.; Pavlov, K. M.; Kraeusslich, J.; Wehrhan, O.; Uschmann, I.; Foerster, E.

    2007-12-17

    We have performed an analyzer crystal based phase contrast imaging (ABI) experiment using a rotating anode x-ray source. The use of such an incoherent source demonstrates the potential of ABI as a quantitative characterization tool for the laboratory environment. A phase contrast image of a plastic phantom was recorded on high resolution x-ray film and the projected thickness was retrieved from a single image. The projected thickness recovered from the phase contrast image was shown to quantitatively agree with a reference optical microscope measurement.

  2. Low contrast detectability performance of model observers based on CT phantom images: kVp influence.

    PubMed

    Hernandez-Giron, I; Calzado, A; Geleijns, J; Joemai, R M S; Veldkamp, W J H

    2015-11-01

    This paper studies low contrast detectability (LCD) performance of two model observers in CT phantom images acquired at different kVp levels and compares the results with humans in a 2-alternative forced choice experiment (2-AFC). Images of the Catphan phantom with objects of different contrasts (0.5 and 1%) and diameters (2-15 mm) were acquired in an Aquilion ONE 320-detector row CT (Toshiba Medical Systems, Tokyo, Japan), in two experiments, selecting (80-100-120-135 kV) with fixed mAs and varying the mAs to keep the dose constant, respectively. Four human observers evaluated the objects visibility obtaining a proportion correct (PC) for each case. LCD was also analyzed with two model observers (non-prewhitening matched filter with an eye filter, NPWE, and channelized Hotelling observer with Gabor channels, CHO). Object contrast was affected by kV, with differences up to 17% between the lowest and highest kV. Both models overestimated human performance and were corrected by efficiency and internal noise factors. The NPWE model reproduced better the human PC values trends showing Pearson's correlation coefficients ≥0.976 (0.954-0.987, 95% CI) for both experiments, whereas for CHO they were ≥0.706 (0.493-0.839). Bland-Altman plots showed better agreement between NPWE and humans being the average difference Δ and the range of the differences Δ±2σ (σ, standard deviation) of Δ=-0.3%, Δ±2σ = [-4.0%,4.5%]. For CHO, Δ=-1.2%, Δ± 2σ= [-10.7%,8.3%]. The NPWE model can be a useful tool to predict human performance in CT low contrast detection tasks in a standard phantom and be potentially used in protocol optimization based on kV selection.

  3. Task-based strategy for optimized contrast enhanced breast imaging: Analysis of six imaging techniques for mammography and tomosynthesis

    SciTech Connect

    Ikejimba, Lynda C.; Kiarashi, Nooshin; Ghate, Sujata V.; Samei, Ehsan; Lo, Joseph Y.

    2014-06-15

    Purpose: The use of contrast agents in breast imaging has the capability of enhancing nodule detectability and providing physiological information. Accordingly, there has been a growing trend toward using iodine as a contrast medium in digital mammography (DM) and digital breast tomosynthesis (DBT). Widespread use raises concerns about the best way to use iodine in DM and DBT, and thus a comparison is necessary to evaluate typical iodine-enhanced imaging methods. This study used a task-based observer model to determine the optimal imaging approach by analyzing six imaging paradigms in terms of their ability to resolve iodine at a given dose: unsubtracted mammography and tomosynthesis, temporal subtraction mammography and tomosynthesis, and dual energy subtraction mammography and tomosynthesis. Methods: Imaging performance was characterized using a detectability index d{sup ′}, derived from the system task transfer function (TTF), an imaging task, iodine signal difference, and the noise power spectrum (NPS). The task modeled a 10 mm diameter lesion containing iodine concentrations between 2.1 mg/cc and 8.6 mg/cc. TTF was obtained using an edge phantom, and the NPS was measured over several exposure levels, energies, and target-filter combinations. Using a structured CIRS phantom, d{sup ′} was generated as a function of dose and iodine concentration. Results: For all iodine concentrations and dose, temporal subtraction techniques for mammography and tomosynthesis yielded the highest d{sup ′}, while dual energy techniques for both modalities demonstrated the next best performance. Unsubtracted imaging resulted in the lowest d{sup ′} values for both modalities, with unsubtracted mammography performing the worst out of all six paradigms. Conclusions: At any dose, temporal subtraction imaging provides the greatest detectability, with temporally subtracted DBT performing the highest. The authors attribute the successful performance to excellent cancellation of

  4. Task-based strategy for optimized contrast enhanced breast imaging: Analysis of six imaging techniques for mammography and tomosynthesis

    PubMed Central

    Ikejimba, Lynda C.; Kiarashi, Nooshin; Ghate, Sujata V.; Samei, Ehsan; Lo, Joseph Y.

    2014-01-01

    Purpose: The use of contrast agents in breast imaging has the capability of enhancing nodule detectability and providing physiological information. Accordingly, there has been a growing trend toward using iodine as a contrast medium in digital mammography (DM) and digital breast tomosynthesis (DBT). Widespread use raises concerns about the best way to use iodine in DM and DBT, and thus a comparison is necessary to evaluate typical iodine-enhanced imaging methods. This study used a task-based observer model to determine the optimal imaging approach by analyzing six imaging paradigms in terms of their ability to resolve iodine at a given dose: unsubtracted mammography and tomosynthesis, temporal subtraction mammography and tomosynthesis, and dual energy subtraction mammography and tomosynthesis. Methods: Imaging performance was characterized using a detectability index d′, derived from the system task transfer function (TTF), an imaging task, iodine signal difference, and the noise power spectrum (NPS). The task modeled a 10 mm diameter lesion containing iodine concentrations between 2.1 mg/cc and 8.6 mg/cc. TTF was obtained using an edge phantom, and the NPS was measured over several exposure levels, energies, and target-filter combinations. Using a structured CIRS phantom, d′ was generated as a function of dose and iodine concentration. Results: For all iodine concentrations and dose, temporal subtraction techniques for mammography and tomosynthesis yielded the highest d′, while dual energy techniques for both modalities demonstrated the next best performance. Unsubtracted imaging resulted in the lowest d′ values for both modalities, with unsubtracted mammography performing the worst out of all six paradigms. Conclusions: At any dose, temporal subtraction imaging provides the greatest detectability, with temporally subtracted DBT performing the highest. The authors attribute the successful performance to excellent cancellation of inplane structures and

  5. Closed Loop, DM Diversity-based, Wavefront Correction Algorithm for High Contrast Imaging Systems

    NASA Technical Reports Server (NTRS)

    Give'on, Amir; Belikov, Ruslan; Shaklan, Stuart; Kasdin, Jeremy

    2007-01-01

    High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

  6. Study of quality perception in medical images based on comparison of contrast enhancement techniques in mammographic images

    NASA Astrophysics Data System (ADS)

    Matheus, B.; Verçosa, L. B.; Barufaldi, B.; Schiabel, H.

    2014-03-01

    With the absolute prevalence of digital images in mammography several new tools became available for radiologist; such as CAD schemes, digital zoom and contrast alteration. This work focuses in contrast variation and how the radiologist reacts to these changes when asked to evaluated image quality. Three contrast enhancing techniques were used in this study: conventional equalization, CCB Correction [1] - a digitization correction - and value subtraction. A set of 100 images was used in tests from some available online mammographic databases. The tests consisted of the presentation of all four versions of an image (original plus the three contrast enhanced images) to the specialist, requested to rank each one from the best up to worst quality for diagnosis. Analysis of results has demonstrated that CCB Correction [1] produced better images in almost all cases. Equalization, which mathematically produces a better contrast, was considered the worst for mammography image quality enhancement in the majority of cases (69.7%). The value subtraction procedure produced images considered better than the original in 84% of cases. Tests indicate that, for the radiologist's perception, it seems more important to guaranty full visualization of nuances than a high contrast image. Another result observed is that the "ideal" scanner curve does not yield the best result for a mammographic image. The important contrast range is the middle of the histogram, where nodules and masses need to be seen and clearly distinguished.

  7. Refracting Roentgen's rays: Propagation-based x-ray phase contrast for biomedical imaging

    SciTech Connect

    Gureyev, T. E.; Mayo, S. C.; Nesterets, Ya.; Pogany, A.; Stevenson, A. W.; Wilkins, S. W.; Myers, D. E.; Paganin, D. M.

    2009-05-15

    Absorption-contrast x-ray imaging serves to visualize the variation in x-ray attenuation within the volume of a given sample, whereas phase contrast allows one to visualize variations in x-ray refractive index. The former imaging mechanism has been well known and widely utilized since the time of Roentgen's Nobel prize winning work, whereas the latter mechanism--sought for, but not found, by Roentgen himself--has laid the foundation for a revolution in x-ray imaging which is the central topic of this review. We consider the physical imaging mechanisms underlying both absorption contrast and phase contrast, together with the associated inverse problem of how one may obtain quantitative two- or three-dimensional information regarding a sample, given one or more phase-contrast images of the same. Practical questions are considered, regarding optimized phase-contrast imaging geometries as a function of detector resolution, source size, x-ray spectrum, and dose. Experimental examples pertaining to biomedical applications are given, and prospects for the future outlined.

  8. A fusion method for visible and infrared images based on contrast pyramid with teaching learning based optimization

    NASA Astrophysics Data System (ADS)

    Jin, Haiyan; Wang, Yanyan

    2014-05-01

    This paper proposes a novel image fusion scheme based on contrast pyramid (CP) with teaching learning based optimization (TLBO) for visible and infrared images under different spectrum of complicated scene. Firstly, CP decomposition is employed into every level of each original image. Then, we introduce TLBO to optimizing fusion coefficients, which will be changed under teaching phase and learner phase of TLBO, so that the weighted coefficients can be automatically adjusted according to fitness function, namely the evaluation standards of image quality. At last, obtain fusion results by the inverse transformation of CP. Compared with existing methods, experimental results show that our method is effective and the fused images are more suitable for further human visual or machine perception.

  9. Optimization of propagation-based phase-contrast imaging at a laboratory setup.

    PubMed

    Bidola, Pidassa M; Zanette, Irene; Achterhold, Klaus; Holzner, Christian; Pfeiffer, Franz

    2015-11-16

    Single distance X-ray propagation-based phase-contrast imaging is considered as a simple method compared to those requiring additional precise instruments and sophisticated algorithms to retrieve phase images. It requires, however, a modicum of conditions within the setup which include partial coherence and small pixel size at the sample position. While these conditions are usually satisfied at synchrotron light sources, they are not always satisfied within laboratory setups. In fact, these setups are limited by the size of the polychromatic source that directly influences the partial coherence of the beam, the propagation distance and the photon flux. A prior knowledge of the sample refractive index, namely the ratio of delta (δ) and beta (β) values, are also essential for the phase retrieval but this method is powerful in the presence of noise compared to absorption-based imaging. An investigation of the feasibility and the efficient applicability of this method in a commercially available X-ray microscope is conducted in this work.

  10. Nulling interferometers for space-based high contrast visible imaging and measurement of exoplanetary environments

    NASA Astrophysics Data System (ADS)

    Hicks, Brian Andrew

    This dissertation presents the legacy, theory, design, characterization, and application prospects of a fully symmetric monolithic nulling interferometer (nuller). A nuller's function is to destructively interfere light originating from a bright, on-axis, unresolved source in order to lower its contrast with faint, off-axis sources of light in the field of view. The primary application lies in astronomical instrumentation, serving as an enabling technology for directly imaging exoplanets and measuring exozodiacal dust and debris disks, the planetary system evolutionary components around nearby stars. Typical on-sky planet/star flux ratios are 1:109 or less in the visible. Mitigating this contrast is key to spectroscopic study of exoplanets, which aims to characterize exoplanetary atmospheres and potentially locate biosignatures on exo-Earths. Within the past decade, adaptive optics-equipped breadboard demonstrations of nullers and other coronagraphs have shown the capability to image nearby (≤ 30 lightyears) extrasolar analogs to Jupiter with a 0.5 meter diameter telescope in the visible. The quiet laboratory environments that have been produced to demonstrate this capability do not reflect those of typical ground-based observatories where thermal drifts perturb optical alignment and atmospheric turbulence perturbs the source wavefront. Space-based platforms circumvent the atmosphere problem, but are still subjected to thermal instabilities and their associated risks. Robust optical systems must be designed and flight-tested in order to address such risks and provide grounds for their inclusion in the design of future exo-Earth imaging satellites. Sub-orbital platforms such as sounding rockets and high-altitude balloons provide a rapid, low-cost means of providing heritage for such optical systems while also delivering significant scientific results. The primary risk inherent with these platforms are harsh transient environmental conditions, for which, similar to

  11. Contrast based band selection for optimized weathered oil detection in hyperspectral images

    NASA Astrophysics Data System (ADS)

    Levaux, Florian; Bostater, Charles R., Jr.; Neyt, Xavier

    2012-09-01

    Hyperspectral imagery offers unique benefits for detection of land and water features due to the information contained in reflectance signatures such as the bi-directional reflectance distribution function or BRDF. The reflectance signature directly shows the relative absorption and backscattering features of targets. These features can be very useful in shoreline monitoring or surveillance applications, for example to detect weathered oil. In real-time detection applications, processing of hyperspectral data can be an important tool and Optimal band selection is thus important in real time applications in order to select the essential bands using the absorption and backscatter information. In the present paper, band selection is based upon the optimization of target detection using contrast algorithms. The common definition of the contrast (using only one band out of all possible combinations available within a hyperspectral image) is generalized in order to consider all the possible combinations of wavelength dependent contrasts using hyperspectral images. The inflection (defined here as an approximation of the second derivative) is also used in order to enhance the variations in the reflectance spectra as well as in the contrast spectrua in order to assist in optimal band selection. The results of the selection in term of target detection (false alarms and missed detection) are also compared with a previous method to perform feature detection, namely the matched filter. In this paper, imagery is acquired using a pushbroom hyperspectral sensor mounted at the bow of a small vessel. The sensor is mechanically rotated using an optical rotation stage. This opto-mechanical scanning system produces hyperspectral images with pixel sizes on the order of mm to cm scales, depending upon the distance between the sensor and the shoreline being monitored. The motion of the platform during the acquisition induces distortions in the collected HSI imagery. It is therefore

  12. Using the magnetosome to model effective gene-based contrast for magnetic resonance imaging.

    PubMed

    Goldhawk, Donna E; Rohani, Roja; Sengupta, Anindita; Gelman, Neil; Prato, Frank S

    2012-01-01

    Formation of iron biominerals is a naturally occurring phenomenon, particularly among magnetotactic bacteria which produce magnetite (Fe(3) O(4) ) in a subcellular compartment termed the magnetosome. Under the control of numerous genes, the magnetosome serves as a model upon which to (1) develop gene-based contrast in mammalian cells and (2) provide a mechanism for reporter gene expression in magnetic resonance imaging (MRI). There are two main components to the magnetosome: the biomineral and the lipid bilayer that surrounds it. Both are essential for magnetotaxis in a variety of magnetotactic bacteria, but nonessential for cell survival. Through comparative genome analysis, a subset of genes characteristic of the magnetotactic phenotype has been found both within and outside a magnetosome genomic island. The functions of magnetosome-associated proteins reflect the complex nature of this intracellular structure and include vesicle formation, cytoskeletal attachment, iron transport, and crystallization. Examination of magnetosome genes and structure indicates a protein-directed and stepwise assembly of the magnetosome compartment. Attachment of magnetosomes along a cytoskeletal filament aligns the magnetic particles such that the cell may be propelled along an external magnetic field. Interest in this form of magnetotaxis has prompted research in several areas of medicine, including magnetotactic bacterial targeting of tumors, MR-guided movement of magnetosome-bearing cells through vessels and molecular imaging of mammalian cells using MRI, and its hybrid modalities. The potential adaptation of magnetosome genes for noninvasive medical imaging provides new opportunities for development of reporter gene expression for MRI.

  13. SEM technique for imaging and measuring electronic transport in nanocomposites based on electric field induced contrast

    DOEpatents

    Jesse, Stephen [Knoxville, TN; Geohegan, David B [Knoxville, TN; Guillorn, Michael [Brooktondale, NY

    2009-02-17

    Methods and apparatus are described for SEM imaging and measuring electronic transport in nanocomposites based on electric field induced contrast. A method includes mounting a sample onto a sample holder, the sample including a sample material; wire bonding leads from the sample holder onto the sample; placing the sample holder in a vacuum chamber of a scanning electron microscope; connecting leads from the sample holder to a power source located outside the vacuum chamber; controlling secondary electron emission from the sample by applying a predetermined voltage to the sample through the leads; and generating an image of the secondary electron emission from the sample. An apparatus includes a sample holder for a scanning electron microscope having an electrical interconnect and leads on top of the sample holder electrically connected to the electrical interconnect; a power source and a controller connected to the electrical interconnect for applying voltage to the sample holder to control the secondary electron emission from a sample mounted on the sample holder; and a computer coupled to a secondary electron detector to generate images of the secondary electron emission from the sample.

  14. In vivo x-ray phase contrast analyzer-based imaging for longitudinal osteoarthritis studies in guinea pigs

    NASA Astrophysics Data System (ADS)

    Coan, Paola; Wagner, Andreas; Bravin, Alberto; Diemoz, Paul C.; Keyriläinen, Jani; Mollenhauer, Juergen

    2010-12-01

    Over the last two decades phase contrast x-ray imaging techniques have been extensively studied for applications in the biomedical field. Published results demonstrate the high capability of these imaging modalities of improving the image contrast of biological samples with respect to standard absorption-based radiography and routinely used clinical imaging techniques. A clear depiction of the anatomic structures and a more accurate disease diagnosis may be provided by using radiation doses comparable to or lower than those used in current clinical methods. In the literature many works show images of phantoms and excised biological samples proving the high sensitivity of the phase contrast imaging methods for in vitro investigations. In this scenario, the applications of the so-called analyzer-based x-ray imaging (ABI) phase contrast technique are particularly noteworthy. The objective of this work is to demonstrate the feasibility of in vivo x-ray ABI phase contrast imaging for biomedical applications and in particular with respect to joint anatomic depiction and osteoarthritis detection. ABI in planar and tomographic modes was performed in vivo on articular joints of guinea pigs in order to investigate the animals with respect to osteoarthritis by using highly monochromatic x-rays of 52 keV and a low noise detector with a pixel size of 47 × 47 µm2. Images give strong evidence of the ability of ABI in depicting both anatomic structures in complex systems as living organisms and all known signs of osteoarthritis with high contrast, high spatial resolution and with an acceptable radiation dose. This paper presents the first proof of principle study of in vivo application of ABI. The technical challenges encountered when imaging an animal in vivo are discussed. This experimental study is an important step toward the study of clinical applications of phase contrast x-ray imaging techniques.

  15. Fe-based nanoparticulate metallic alloys as contrast agents for magnetic resonance imaging.

    PubMed

    Bomatí-Miguel, Oscar; Morales, María P; Tartaj, Pedro; Ruiz-Cabello, Jesús; Bonville, Pierre; Santos, Martín; Zhao, Xinqing; Veintemillas-Verdaguer, Sabino

    2005-10-01

    Pharmaceutical grade magnetic colloidal dispersions have been prepared from iron alloys synthesized by laser pyrolysis. The colloids were obtained by simultaneous dispersion and coating of the particles with dextran in a strong alkaline solution. Both powders and dispersions have been analyzed in terms of microstructural characteristics, chemical composition and magnetic properties. The powders consist of uniform spherical nanoparticles (12 nm of diameter) showing a metallic core encapsulated into an iron-oxide shell. On the other hand, the colloidal dispersions consist of magnetic particles-aggregates with hydrodynamic sizes of approximately 75 nm. Magnetic resonance images of rats were taken after the intravenously administration of the Fe colloidal dispersions, and compared with those obtained using a commercial iron oxide magnetic resonance imaging contrast agent. The results showed a contrast improvement of 60% in the liver with respect to the commercial sample, which suggests that this product could be a suitable contrast agent for NMR imaging of liver and spleen.

  16. SU-E-J-16: Automatic Image Contrast Enhancement Based On Automatic Parameter Optimization for Radiation Therapy Setup Verification

    SciTech Connect

    Qiu, J; Li, H. Harlod; Zhang, T; Yang, D; Ma, F

    2015-06-15

    Purpose: In RT patient setup 2D images, tissues often cannot be seen well due to the lack of image contrast. Contrast enhancement features provided by image reviewing software, e.g. Mosaiq and ARIA, require manual selection of the image processing filters and parameters thus inefficient and cannot be automated. In this work, we developed a novel method to automatically enhance the 2D RT image contrast to allow automatic verification of patient daily setups as a prerequisite step of automatic patient safety assurance. Methods: The new method is based on contrast limited adaptive histogram equalization (CLAHE) and high-pass filtering algorithms. The most important innovation is to automatically select the optimal parameters by optimizing the image contrast. The image processing procedure includes the following steps: 1) background and noise removal, 2) hi-pass filtering by subtracting the Gaussian smoothed Result, and 3) histogram equalization using CLAHE algorithm. Three parameters were determined through an iterative optimization which was based on the interior-point constrained optimization algorithm: the Gaussian smoothing weighting factor, the CLAHE algorithm block size and clip limiting parameters. The goal of the optimization is to maximize the entropy of the processed Result. Results: A total 42 RT images were processed. The results were visually evaluated by RT physicians and physicists. About 48% of the images processed by the new method were ranked as excellent. In comparison, only 29% and 18% of the images processed by the basic CLAHE algorithm and by the basic window level adjustment process, were ranked as excellent. Conclusion: This new image contrast enhancement method is robust and automatic, and is able to significantly outperform the basic CLAHE algorithm and the manual window-level adjustment process that are currently used in clinical 2D image review software tools.

  17. Propagator based formalism for optimizing in-line phase contrast imaging in laboratory X-ray setups.

    PubMed

    Balles, Andreas; Zabler, Simon; Ebensperger, Thomas; Fella, Christian; Hanke, Randolf

    2016-09-01

    We derive a propagator based formalism for optimizing phase contrast imaging in laboratory setups as well as in synchrotron setups. We confirm based on five different setups the well known existence of an optimum position for the sample in terms of phase contrast by measuring two types of fibers and evaluating the fringe contrast. Furthermore, we demonstrate for these setups a correlation of our formula and the fringe contrast. Hence, an estimate of this optimum position is given by our formalism which only depends on the source size, the detector blurring, and the total distance between source and detector.

  18. Super-Gaussian apodization in ground based telescopes for high contrast coronagraph imaging.

    PubMed

    Cagigas, Miguel A; Valle, Pedro J; Cagigal, Manuel P

    2013-05-20

    We introduce the use of Super-Gaussian apodizing functions in the telescope pupil plane and/or the coronagraph Lyot plane to improve the imaging contrast in ground-based coronagraphs. We describe the properties of the Super-Gaussian function, we estimate its second-order moment in the pupil and Fourier planes and we check it as an apodizing function. We then use Super-Gaussian function to apodize the telescope pupil, the coronagraph Lyot plane or both of them. The result is that a proper apodizing masks combination can reduce the exoplanet detection distance up to a 45% with respect to the classic Lyot coronagraph, for moderately aberrated wavefronts. Compared to the prolate spheroidal function the Super-Gaussian apodizing function allows the planet light up to 3 times brighter. An extra help to increase the extinction rate is to perform a frame selection (Lucky Imaging technique). We show that a selection of the 10% best frames will reduce up to a 20% the detection angular distance when using the classic Lyot coronagraph but that the reduction is only around the 5% when using an apodized coronagraph.

  19. Prediction of object detection, recognition, and identification [DRI] ranges at color scene images based on quantifying human color contrast perception

    NASA Astrophysics Data System (ADS)

    Pinsky, Ephi; Levin, Ilia; Yaron, Ofer

    2016-10-01

    We propose a novel approach to predict, for specified color imaging system and for objects with known characteristics, their detection, recognition, identification (DRI) ranges in a colored dynamic scene, based on quantifying the human color contrast perception. The method refers to the well established L*a*b*, 3D color space. The nonlinear relations of this space are intended to mimic the nonlinear response of the human eye. The metrics of L*a*b* color space is such that the Euclidian distance between any two colors in this space is approximately proportional to the color contrast as perceived by the human eye/brain. The result of this metrics leads to the outcome that color contrast of any two points is always greater (or equal) than their equivalent grey scale contrast. This meets our sense that looking on a colored image, contrast is superior to the gray scale contrast of the same image. Yet, color loss by scattering at very long ranges should be considered as well. The color contrast derived from the distance between the colored object pixels and to the nearby colored background pixels, as derived from the L*a*b* color space metrics, is expressed in terms of gray scale contrast. This contrast replaces the original standard gray scale contrast component of that image. As expected, the resulted DRI ranges are, in most cases, larger than those predicted by the standard gray scale image. Upon further elaboration and validation of this method, it may be combined with the next versions of the well accepted TRM codes for DRI predictions. Consistent prediction of DRI ranges implies a careful evaluation of the object and background color contrast reduction along the range. Clearly, additional processing for reconstructing the objects and background true colors and hence the color contrast along the range, will further increase the DRI ranges.

  20. Recent advances in ytterbium-based contrast agents for in vivo X-ray computed tomography imaging: promises and prospects.

    PubMed

    Liu, Yanlan; Liu, Jianhua; Ai, Kelong; Yuan, Qinghai; Lu, Lehui

    2014-01-01

    X-ray computed tomography (CT) imaging is one of the most widely used diagnostic imaging techniques in the clinic, and has raised significant interest in recent years both in research and practice owing to its many advantages such as deep penetration depth, high resolution and facile image processing. Developing heavy metal-based CT contrast agents, especially heavy metal-containing nanoparticulate CT contrast agents, has become a key focus in research fields to address issues of clinical iodinated agents involving short circulation time, low contrast efficiency and potential renal toxicity. In this review, we summarize the development of ytterbium (Yb)-based CT contrast agents and highlight the design and applications of Yb-based nanoparticulate CT contrast agents. Yb has high atomic number and higher abundance in the earth's crust relative to Au, Ta and Bi, which have received much attention as a CT contrast agents. In particular, in contrast to these metal elements, as well as I, Yb has K-edge energy that is located just within the higher-intensity region of X-ray spectra, which can induce significant enhancement in the contrast efficiency. When encapsulated in nanoparticles, Yb can remain in the circulation for a long time. This long in vivo circulation time, combined with the proper K-edge energy and a large absorption cross-section of Yb in the near-infrared region, makes Yb-based nanoparticles particularly promising in angiography, 'multicolor' spectral CT imaging, and multimodal imaging. Finally, we also discuss the prospects and the challenges in the development of Yb-based CT contrast agents.

  1. Content-Based Image Retrieval Using Spatial Layout Information in Brain Tumor T1-Weighted Contrast-Enhanced MR Images

    PubMed Central

    Huang, Meiyan; Yang, Wei; Wu, Yao; Jiang, Jun; Gao, Yang; Chen, Yang; Feng, Qianjin; Chen, Wufan; Lu, Zhentai

    2014-01-01

    This study aims to develop content-based image retrieval (CBIR) system for the retrieval of T1-weighted contrast-enhanced MR (CE-MR) images of brain tumors. When a tumor region is fed to the CBIR system as a query, the system attempts to retrieve tumors of the same pathological category. The bag-of-visual-words (BoVW) model with partition learning is incorporated into the system to extract informative features for representing the image contents. Furthermore, a distance metric learning algorithm called the Rank Error-based Metric Learning (REML) is proposed to reduce the semantic gap between low-level visual features and high-level semantic concepts. The effectiveness of the proposed method is evaluated on a brain T1-weighted CE-MR dataset with three types of brain tumors (i.e., meningioma, glioma, and pituitary tumor). Using the BoVW model with partition learning, the mean average precision (mAP) of retrieval increases beyond 4.6% with the learned distance metrics compared with the spatial pyramid BoVW method. The distance metric learned by REML significantly outperforms three other existing distance metric learning methods in terms of mAP. The mAP of the CBIR system is as high as 91.8% using the proposed method, and the precision can reach 93.1% when the top 10 images are returned by the system. These preliminary results demonstrate that the proposed method is effective and feasible for the retrieval of brain tumors in T1-weighted CE-MR Images. PMID:25028970

  2. In vivo confirmation of hydration based contrast mechanisms for terahertz medical imaging using MRI

    NASA Astrophysics Data System (ADS)

    Bajwa, Neha; Sung, Shijun; Garritano, James; Nowroozi, Bryan; Tewari, Priyamvada; Ennis, Daniel B.; Alger, Jeffery; Grundfest, Warren; Taylor, Zachary

    2014-09-01

    Terahertz (THz) detection has been proposed and applied to a variety of medical imaging applications in view of its unrivaled hydration profiling capabilities. Variations in tissue dielectric function have been demonstrated at THz frequencies to generate high contrast imagery of tissue, however, the source of image contrast remains to be verified using a modality with a comparable sensing scheme. To investigate the primary contrast mechanism, a pilot comparison study was performed in a burn wound rat model, widely known to create detectable gradients in tissue hydration through both injured and surrounding tissue. Parallel T2 weighted multi slice multi echo (T2w MSME) 7T Magnetic Resonance (MR) scans and THz surface reflectance maps were acquired of a full thickness skin burn in a rat model over a 5 hour time period. A comparison of uninjured and injured regions in the full thickness burn demonstrates a 3-fold increase in average T2 relaxation times and a 15% increase in average THz reflectivity, respectively. These results support the sensitivity and specificity of MRI for measuring in vivo burn tissue water content and the use of this modality to verify and understand the hydration sensing capabilities of THz imaging for acute assessments of the onset and evolution of diseases that affect the skin. A starting point for more sophisticated in vivo studies, this preliminary analysis may be used in the future to explore how and to what extent the release of unbound water affects imaging contrast in THz burn sensing.

  3. New generation ICG-based contrast agents for ultrasound-switchable fluorescence imaging

    PubMed Central

    Yu, Shuai; Cheng, Bingbing; Yao, Tingfeng; Xu, Cancan; Nguyen, Kytai T.; Hong, Yi; Yuan, Baohong

    2016-01-01

    Recently, we developed a new technology, ultrasound-switchable fluorescence (USF), for high-resolution imaging in centimeter-deep tissues via fluorescence contrast. The success of USF imaging highly relies on excellent contrast agents. ICG-encapsulated poly(N-isopropylacrylamide) nanoparticles (ICG-NPs) are one of the families of the most successful near-infrared (NIR) USF contrast agents. However, the first-generation ICG-NPs have a short shelf life (<1 month). This work significantly increases the shelf life of the new-generation ICG-NPs (>6 months). In addition, we have conjugated hydroxyl or carboxyl function groups on the ICG-NPs for future molecular targeting. Finally, we have demonstrated the effect of temperature-switching threshold (Tth) and the background temperature (TBG) on the quality of USF images. We estimated that the Tth of the ICG-NPs should be controlled at ~38–40 °C (slightly above the body temperature of 37 °C) for future in vivo USF imaging. Addressing these challenges further reduces the application barriers of USF imaging. PMID:27775014

  4. New generation ICG-based contrast agents for ultrasound-switchable fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Yu, Shuai; Cheng, Bingbing; Yao, Tingfeng; Xu, Cancan; Nguyen, Kytai T.; Hong, Yi; Yuan, Baohong

    2016-10-01

    Recently, we developed a new technology, ultrasound-switchable fluorescence (USF), for high-resolution imaging in centimeter-deep tissues via fluorescence contrast. The success of USF imaging highly relies on excellent contrast agents. ICG-encapsulated poly(N-isopropylacrylamide) nanoparticles (ICG-NPs) are one of the families of the most successful near-infrared (NIR) USF contrast agents. However, the first-generation ICG-NPs have a short shelf life (<1 month). This work significantly increases the shelf life of the new-generation ICG-NPs (>6 months). In addition, we have conjugated hydroxyl or carboxyl function groups on the ICG-NPs for future molecular targeting. Finally, we have demonstrated the effect of temperature-switching threshold (Tth) and the background temperature (TBG) on the quality of USF images. We estimated that the Tth of the ICG-NPs should be controlled at ~38–40 °C (slightly above the body temperature of 37 °C) for future in vivo USF imaging. Addressing these challenges further reduces the application barriers of USF imaging.

  5. Physicochemical characterization of a novel graphene-based magnetic resonance imaging contrast agent

    PubMed Central

    Kanakia, Shruti; Toussaint, Jimmy D; Chowdhury, Sayan Mullick; Lalwani, Gaurav; Tembulkar, Tanuf; Button, Terry; Shroyer, Kenneth R; Moore, William; Sitharaman, Balaji

    2013-01-01

    We report the synthesis and characterization of a novel carbon nanostructure-based magnetic resonance imaging contrast agent (MRI CA); graphene nanoplatelets intercalated with manganese (Mn2+) ions, functionalized with dextran (GNP-Dex); and the in vitro assessment of its essential preclinical physicochemical properties: osmolality, viscosity, partition coefficient, protein binding, thermostability, histamine release, and relaxivity. The results indicate that, at concentrations between 0.1 and 100.0 mg/mL, the GNP-Dex formulations are hydrophilic, highly soluble, and stable in deionized water, as well as iso-osmolar (upon addition of mannitol) and iso-viscous to blood. At potential steady-state equilibrium concentrations in blood (0.1–10.0 mg/mL), the thermostability, protein-binding, and histamine-release studies indicate that the GNP-Dex formulations are thermally stable (with no Mn2+ ion dissociation), do not allow non-specific protein adsorption, and elicit negligible allergic response. The r1 relaxivity of GNP-Dex was 92 mM−1s−1 (per-Mn2+ ion, 22 MHz proton Larmor frequency); ~20- to 30-fold greater than that of clinical gadolinium (Gd3+)- and Mn2+-based MRI CAs. The results open avenues for preclinical in vivo safety and efficacy studies with GNP-Dex toward its development as a clinical MRI CA. PMID:23946653

  6. Research on respiratory motion correction method based on liver contrast-enhanced ultrasound images of single mode

    NASA Astrophysics Data System (ADS)

    Zhang, Ji; Li, Tao; Zheng, Shiqiang; Li, Yiyong

    2015-03-01

    To reduce the effects of respiratory motion in the quantitative analysis based on liver contrast-enhanced ultrasound (CEUS) image sequencesof single mode. The image gating method and the iterative registration method using model image were adopted to register liver contrast-enhanced ultrasound image sequences of single mode. The feasibility of the proposed respiratory motion correction method was explored preliminarily using 10 hepatocellular carcinomas CEUS cases. The positions of the lesions in the time series of 2D ultrasound images after correction were visually evaluated. Before and after correction, the quality of the weighted sum of transit time (WSTT) parametric images were also compared, in terms of the accuracy and spatial resolution. For the corrected and uncorrected sequences, their mean deviation values (mDVs) of time-intensity curve (TIC) fitting derived from CEUS sequences were measured. After the correction, the positions of the lesions in the time series of 2D ultrasound images were almost invariant. In contrast, the lesions in the uncorrected images all shifted noticeably. The quality of the WSTT parametric maps derived from liver CEUS image sequences were improved more greatly. Moreover, the mDVs of TIC fitting derived from CEUS sequences after the correction decreased by an average of 48.48+/-42.15. The proposed correction method could improve the accuracy of quantitative analysis based on liver CEUS image sequences of single mode, which would help in enhancing the differential diagnosis efficiency of liver tumors.

  7. Accelerated susceptibility-based positive contrast imaging of MR compatible metallic devices based on modified fast spin echo sequences

    NASA Astrophysics Data System (ADS)

    Shi, Caiyun; Xie, Guoxi; Zhang, Yongqin; Zhang, Xiaoyong; Chen, Min; Su, Shi; Dong, Ying; Liu, Xin; Ji, Jim

    2017-04-01

    This study aims to develop an accelerated susceptibility-based positive contrast MR imaging method for visualizing MR compatible metallic devices. A modified fast spin echo sequence is used to accelerate data acquisition. Each readout gradient in the modified fast spin echo is slightly shifted by a short distance T shift. Phase changes accumulated within T shift are then used to calculate the susceptibility map by using a kernel deconvolution algorithm with a regularized ℓ1 minimization. To evaluate the proposed fast spin echo method, three phantom experiments were conducted and compared to a spin echo based technique and the gold standard CT for visualizing biopsy needles and brachytherapy seeds. Compared to the spin echo based technique, the data sampling speed of the proposed method was faster by 2–4 times while still being able to accurately visualize and identify the location of the biopsy needle and brachytherapy seeds. These results were confirmed by CT images of the same devices. Results also demonstrated that the proposed fast spin echo method can achieve good visualization of the brachytherapy seeds in positive contrast and in different orientations. It is also capable of correctly differentiating brachytherapy seeds from other similar structures on conventional magnitude images.

  8. Highly sensitive detection of the soft tissues based on refraction contrast by in-plane diffraction-enhanced imaging CT

    NASA Astrophysics Data System (ADS)

    Yuasa, Tetsuya; Hashimoto, Eiko; Maksimenko, Anton; Sugiyama, Hiroshi; Arai, Yoshinori; Shimao, Daisuke; Ichihara, Shu; Ando, Masami

    2008-07-01

    We discuss the recently proposed computed tomography (CT) technique based on refractive effects for biomedical use, which reconstructs the in-plane refractive-index gradient vector field in a cross-sectional plane of interest by detecting the angular deviation of the beam, refracted by a sample, from the incident beam, using the diffraction-enhanced imaging (DEI) method. The CT has advantages for delineating biological weakly absorbing soft tissues over the conventional absorption-contrast CT because of the use of phase sensitive detection. The paper aims to define the imaging scheme rigidly and to demonstrate its efficacy for non-destructive measurement of biomedical soft-tissue samples without imaging agent. We first describe the imaging principle of in-plane DEI-CT from the physico-mathematical viewpoints in detail, and investigate what physical quantities are extracted from the reconstructed images. Then, we introduce the imaging system using the synchrotron radiation as a light source, constructed at beamline BL-14B in KEK, Japan. Finally, we demonstrate the advantage of the refraction-based image for non-destructive analysis of biological sample by investigating the image of human breast cancer tumors obtained using the imaging system. Here, the refraction- and the apparent absorption-based images obtained simultaneously by the in-plane DEI-CT are compared. Also, the conventional absorption-based image obtained using micro-computed tomography (μCT) imaging system is compared with them. Thereby, it is shown that the refraction contrast much more sensitively delineates the soft tissues than the absorption contrast. In addition, the radiologic-histologic correlation study not only validates the efficacy for imaging soft tissues, but also produces the potential that the pathological inspection for the breast cancer tumors may be feasible non-destructively.

  9. Rapid contrast evaluation method based on affinity beads and backscattered electron imaging for the screening of electron stains.

    PubMed

    Kaku, Hiroki; Inoue, Kanako; Muranaka, Yoshinori; Park, Pyoyun; Ikeda, Kenichi

    2015-10-01

    Uranyl salts are toxic and radioactive; therefore, several studies have been conducted to screen for substitutes of electron stains. In this regard, the contrast evaluation process is time consuming and the results obtained are inconsistent. In this study, we developed a novel contrast evaluation method using affinity beads and a backscattered electron image (BSEI), obtained using scanning electron microscopy. The contrast ratios of BSEI in each electron stain treatment were correlated with those of transmission electron microscopic images. The affinity beads bound to cell components independently. Protein and DNA samples were enhanced by image contrast treated with electron stains; however, this was not observed for sugars. Protein-conjugated beads showed an additive effect of image contrast when double-stained with lead. However, additive effect of double staining was not observed in DNA-conjugated beads. The varying chemical properties of oligopeptides showed differences in image contrast when treated with each electron stain. This BSEI-based evaluation method not only enables screening for alternate electron stains, but also helps analyze the underlying mechanisms of electron staining of cellular structures.

  10. Mobile phone based laser speckle contrast imager for assessment of skin blood flow

    NASA Astrophysics Data System (ADS)

    Jakovels, Dainis; Saknite, Inga; Krievina, Gita; Zaharans, Janis; Spigulis, Janis

    2014-10-01

    Assessment of skin blood flow is of interest for evaluation of skin viability as well as for reflection of the overall condition of the circulatory system. Laser Doppler perfusion imaging (LDPI) and laser speckle contrast imaging (LASCI) are optical techniques used for assessment of skin perfusion. However, these systems are still too expensive and bulky to be widely available. Implementation of such techniques as connection kits for mobile phones have a potential for primary diagnostics. In this work we demonstrate simple and low cost LASCI connection kit for mobile phone and its comparison to laser Doppler perfusion imager. Post-occlusive hyperemia and local thermal hyperemia tests are used to compare both techniques and to demonstrate the potential of LASCI device.

  11. High-contrast active cavitation imaging technique based on multiple bubble wavelet transform.

    PubMed

    Lu, Shukuan; Xu, Shanshan; Liu, Runna; Hu, Hong; Wan, Mingxi

    2016-08-01

    In this study, a unique method that combines the ultrafast active cavitation imaging technique with multiple bubble wavelet transform (MBWT) for improving cavitation detection contrast was presented. The bubble wavelet was constructed by the modified Keller-Miksis equation that considered the mutual effect among bubbles. A three-dimensional spatial model was applied to simulate the spatial distribution of multiple bubbles. The effects of four parameters on the signal-to-noise ratio (SNR) of cavitation images were evaluated, including the following: initial radii of bubbles, scale factor in the wavelet transform, number of bubbles, and the minimum inter-bubble distance. And the other two spatial models and cavitation bubble size distributions were introduced in the MBWT method. The results suggested that in the free-field experiments, the averaged SNR of images acquired by the MBWT method was improved by 7.16 ± 0.09 dB and 3.14 ± 0.14 dB compared with the values of images acquired by the B-mode and single bubble wavelet transform (SBWT) methods. In addition, in the tissue experiments, the averaged cavitation-to-tissue ratio of cavitation images acquired by the MBWT method was improved by 4.69 ± 0.25 dB and 1.74± 0.29 dB compared with that of images acquired by B-mode and SBWT methods.

  12. A user-friendly LabVIEW software platform for grating based X-ray phase-contrast imaging.

    PubMed

    Wang, Shenghao; Han, Huajie; Gao, Kun; Wang, Zhili; Zhang, Can; Yang, Meng; Wu, Zhao; Wu, Ziyu

    2015-01-01

    X-ray phase-contrast imaging can provide greatly improved contrast over conventional absorption-based imaging for weakly absorbing samples, such as biological soft tissues and fibre composites. In this study, we introduced an easy and fast way to develop a user-friendly software platform dedicated to the new grating-based X-ray phase-contrast imaging setup at the National Synchrotron Radiation Laboratory of the University of Science and Technology of China. The control of 21 motorized stages, of a piezoelectric stage and of an X-ray tube are achieved with this software, it also covers image acquisition with a flat panel detector for automatic phase stepping scan. Moreover, a data post-processing module for signals retrieval and other custom features are in principle available. With a seamless integration of all the necessary functions in one software package, this platform greatly facilitate users' activities during experimental runs with this grating based X-ray phase contrast imaging setup.

  13. Increasing the field of view in grating based X-ray phase contrast imaging using stitched gratings.

    PubMed

    Meiser, J; Willner, M; Schröter, T; Hofmann, A; Rieger, J; Koch, F; Birnbacher, L; Schüttler, M; Kunka, D; Meyer, P; Faisal, A; Amberger, M; Duttenhofer, T; Weber, T; Hipp, A; Ehn, S; Walter, M; Herzen, J; Schulz, J; Pfeiffer, F; Mohr, J

    2016-03-17

    Grating based X-ray differential phase contrast imaging (DPCI) allows for high contrast imaging of materials with similar absorption characteristics. In the last years' publications, small animals or parts of the human body like breast, hand, joints or blood vessels have been studied. Larger objects could not be investigated due to the restricted field of view limited by the available grating area. In this paper, we report on a new stitching method to increase the grating area significantly: individual gratings are merged on a carrier substrate. Whereas the grating fabrication process is based on the LIGA technology (X-ray lithography and electroplating) different cutting and joining methods have been evaluated. First imaging results using a 2×2 stitched analyzer grating in a Talbot-Lau interferometer have been generated using a conventional polychromatic X-ray source. The image quality and analysis confirm the high potential of the stitching method to increase the field of view considerably.

  14. Performance analysis of the attenuation-partition based iterative phase retrieval algorithm for in-line phase-contrast imaging

    PubMed Central

    Yan, Aimin; Wu, Xizeng; Liu, Hong

    2010-01-01

    The phase retrieval is an important task in x-ray phase contrast imaging. The robustness of phase retrieval is especially important for potential medical imaging applications such as phase contrast mammography. Recently the authors developed an iterative phase retrieval algorithm, the attenuation-partition based algorithm, for the phase retrieval in inline phase-contrast imaging [1]. Applied to experimental images, the algorithm was proven to be fast and robust. However, a quantitative analysis of the performance of this new algorithm is desirable. In this work, we systematically compared the performance of this algorithm with other two widely used phase retrieval algorithms, namely the Gerchberg-Saxton (GS) algorithm and the Transport of Intensity Equation (TIE) algorithm. The systematical comparison is conducted by analyzing phase retrieval performances with a digital breast specimen model. We show that the proposed algorithm converges faster than the GS algorithm in the Fresnel diffraction regime, and is more robust against image noise than the TIE algorithm. These results suggest the significance of the proposed algorithm for future medical applications with the x-ray phase contrast imaging technique. PMID:20720992

  15. Adapted polarization state contrast image.

    PubMed

    Richert, Michael; Orlik, Xavier; De Martino, Antonello

    2009-08-03

    We propose a general method to maximize the polarimetric contrast between an object and its background using a predetermined illumination polarization state. After a first estimation of the polarimetric properties of the scene by classical Mueller imaging, we evaluate the incident polarized field that induces scattered polarization states by the object and background, as opposite as possible on the Poincar e sphere. With a detection method optimized for a 2-channel imaging system, Monte Carlo simulations of low flux coherent imaging are performed with various objects and backgrounds having different properties of retardance, dichroism and depolarization. With respect to classical Mueller imaging, possibly associated to the polar decomposition, our results show a noticeable increase in the Bhattacharyya distance used as our contrast parameter.

  16. Atmospheric visibility estimation and image contrast calibration

    NASA Astrophysics Data System (ADS)

    Hermansson, Patrik; Edstam, Klas

    2016-10-01

    A method, referred to as contrast calibration, has been developed for transforming digital color photos of outdoor scenes from the atmospheric conditions, illumination and visibility, prevailing at the time of capturing the image to a corresponding image for other atmospheric conditions. A photo captured on a hazy day can, for instance, be converted to resemble a photo of the same scene for good visibility conditions. Converting digital color images to specified lightning and transmission conditions is useful for image based assessment of signature suppression solutions. The method uses "calibration objects" which are photographed at about the same time as the scene of interest. The calibration objects, which (indirectly) provide information on visibility and lightning conditions, consist of two flat boards, painted in different grayscale colors, and a commercial, neutral gray, reference card. Atmospheric extinction coefficient and sky intensity can be determined, in three wavelength bands, from image pixel values on the calibration objects and using this information the image can be converted to other atmospheric conditions. The image is transformed in contrast and color. For illustration, contrast calibration is applied to sample images of a scene acquired at different times. It is shown that contrast calibration of the images to the same reference values of extinction coefficient and sky intensity results in images that are more alike than the original images. It is also exemplified how images can be transformed to various other atmospheric weather conditions. Limitations of the method are discussed and possibilities for further development are suggested.

  17. A grating-based single-shot x-ray phase contrast and diffraction method for in vivo imaging

    SciTech Connect

    Bennett, Eric E.; Kopace, Rael; Stein, Ashley F.; Wen Han

    2010-11-15

    Purpose: The purpose of this study is to develop a single-shot version of the grating-based phase contrast x-ray imaging method and demonstrate its capability of in vivo animal imaging. Here, the authors describe the principle and experimental results. They show the source of artifacts in the phase contrast signal and optimal designs that minimize them. They also discuss its current limitations and ways to overcome them. Methods: A single lead grid was inserted midway between an x-ray tube and an x-ray camera in the planar radiography setting. The grid acted as a transmission grating and cast periodic dark fringes on the camera. The camera had sufficient spatial resolution to resolve the fringes. Refraction and diffraction in the imaged object manifested as position shifts and amplitude attenuation of the fringes, respectively. In order to quantify these changes precisely without imposing a fixed geometric relationship between the camera pixel array and the fringes, a spatial harmonic method in the Fourier domain was developed. The level of the differential phase (refraction) contrast as a function of hardware specifications and device geometry was derived and used to guide the optimal placement of the grid and object. Both ex vivo and in vivo images of rodent extremities were collected to demonstrate the capability of the method. The exposure time using a 50 W tube was 28 s. Results: Differential phase contrast images of glass beads acquired at various grid and object positions confirmed theoretical predictions of how phase contrast and extraneous artifacts vary with the device geometry. In anesthetized rats, a single exposure yielded artifact-free images of absorption, differential phase contrast, and diffraction. Differential phase contrast was strongest at bone-soft tissue interfaces, while diffraction was strongest in bone. Conclusions: The spatial harmonic method allowed us to obtain absorption, differential phase contrast, and diffraction images, all from a

  18. Phase contrast portal imaging using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Umetani, K.; Kondoh, T.

    2014-07-01

    Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.

  19. Phase contrast portal imaging using synchrotron radiation

    SciTech Connect

    Umetani, K.; Kondoh, T.

    2014-07-15

    Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.

  20. Subject-specific patch-based denoising for contrast-enhanced cardiac MR images

    NASA Astrophysics Data System (ADS)

    Ma, Lorraine; Ebrahimi, Mehran; Pop, Mihaela

    2016-03-01

    Many patch-based techniques in imaging, e.g., Non-local means denoising, require tuning parameters to yield optimal results. In real-world applications, e.g., denoising of MR images, ground truth is not generally available and the process of choosing an appropriate set of parameters is a challenge. Recently, Zhu et al. proposed a method to define an image quality measure, called Q, that does not require ground truth. In this manuscript, we evaluate the effect of various parameters of the NL-means denoising on this quality metric Q. Our experiments are based on the late-gadolinium enhancement (LGE) cardiac MR images that are inherently noisy. Our described exhaustive evaluation approach can be used in tuning parameters of patch-based schemes. Even in the case that an estimation of optimal parameters is provided using another existing approach, our described method can be used as a secondary validation step. Our preliminary results suggest that denoising parameters should be case-specific rather than generic.

  1. High-resolution functional imaging with ultrasound contrast agents based on RF processing in an in vivo kidney experiment.

    PubMed

    Verbeek, X A; Willigers, J M; Prinzen, F W; Peschar, M; Ledoux, L A; Hoeks, A P

    2001-02-01

    Knowledge of the relative tissue perfusion distribution is valuable in the diagnosis of numerous diseases. Techniques for the assessment of the relative perfusion distribution, based on ultrasound (US) contrast agents, have several advantages compared to established nuclear techniques. These are, among others, a better spatial and temporal resolution, the lack of exposure of the patient to ionizing radiation and the relatively low cost. In the present study, US radiofrequency (RF) image sequences are acquired, containing the signal intensity changes associated with the transit of a bolus contrast agent through the microvasculature of a dog kidney. The primary objective is to explore the feasibility of calculating functional images with high spatial resolution. The functional images characterize the transit of the contrast agent bolus and represent distributions of peak time, peak value, transit time, peak area, wash-in rate and wash-out decay constant. For the evaluation of the method, dog experiments were performed under optimized conditions where motion artefacts were minimized and an IA injection of the contrast agent Levovist was employed. It was demonstrated that processing of RF signals obtained with a 3.5-MHz echo system can provide functional images with a high spatial resolution of 2 mm in axial resolution, 2 to 5 mm in lateral resolution and a slice thickness of 2 mm. The functional images expose several known aspects of kidney perfusion, like perfusion heterogeneity of the kidney cortex and a different peripheral cortical perfusion compared to the inner cortex. Based on the findings of the present study, and given the results of complimentary studies, it is likely that the functional images reflect the relative perfusion distribution of the kidney.

  2. Characterization of an x-ray phase contrast imaging system based on the miniature synchrotron MIRRORCLE-6X

    SciTech Connect

    Heekeren, Joop van; Kostenko, Alexander; Hanashima, Takayasu; Yamada, Hironari; Stallinga, Sjoerd; Offerman, S. Erik; Vliet, Lucas J. van

    2011-09-15

    Purpose: The implementation of in-line x-ray phase contrast imaging (PCI) for soft-tissue patient imaging is hampered by the lack of a bright and spatially coherent x-ray source that fits into the hospital environment. This article provides a quantitative characterization of the phase-contrast enhancement of a PCI system based on the miniature synchrotron technology MIRRORCLE-6X. Methods: The phase-contrast effect was measured using an edge response of a plexiglass plate as a function of the incident angle of radiation. We have developed a comprehensive x-ray propagation model based on the system's components, properties, and geometry in order to interpret the measurement data. Monte-Carlo simulations are used to estimate the system's spectral properties and resolution. Results: The measured ratio of the detected phase-contrast to the absorption contrast is currently in the range 100% to 200%. Experiments show that with the current implementation of the MIRRORCLE-6X, a target smaller than 30-40 {mu}m does not lead to a larger phase-contrast. The reason for this is that the fraction of x-rays produced by the material (carbon filament and glue) that is used for mounting the target in the electron beam is more than 25% of the total amount of x-rays produced. This increases the apparent source size. The measured phase-contrast is at maximum two times larger than the absorption contrast with the current set-up. Conclusions: Calculations based on our model of the present imaging system predict that the phase-contrast can be up to an order of magnitude larger than the absorption contrast in case the materials used for mounting the target in the electron beam do not (or hardly) produce x-rays. The methods described in this paper provide vital feedback for guiding future modifications to the design of the x-ray target of MIRRORCLE-type system and configuration of the in-line PCI systems in general.

  3. Intra-individual comparison of different gadolinium-based contrast agents in the quantitative evaluation of C6 glioma with dynamic contrast-enhanced magnetic resonance imaging.

    PubMed

    Li, Ying; Liu, Gang; Lou, Xin; Chen, Zhiye; Ma, Lin

    2017-01-01

    This experiment aimed to compare the ionic (Gadodiamide, Gd-DTPA-BMA) and non-ionic (Gadopentetate dimeglumine, Gd-DTPA) gadolinium-based contrast agents (GBCA) in the quantitative evaluation of C6 glioma with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). A C6 glioma model was established in 12 Wistar rats, and magnetic resonance (MR) scans were performed six days after tumor implantation. Imaging was performed using a 3.0-T MR scanner with a 7-inch handmade circular coil. Pre-contrast T1 mapping and dynamic contrast-enhanced T1WI after a bolus injection (0.2 mL s(-1)) of GBCA at 0.4 mmol kg(-1) were performed. Each rat received two DCE-MRI scans, 24 h apart. The first and second scans were performed using Gd-DTPA-BMA and Gd-DTPA, respectively. Image data were processed using the Patlak model. Both K (trans) and V p maps were generated. Tumors were manually segmented on all 3D K (trans) and V p maps. Pixel counts and mean values were recorded for use in a paired t-test. Three radiologists independently performed the tumor segmentation and value calculation. The agreements from different observers were subjective to the intra-class correlation coefficient (ICC). Readers demonstrated that the pixel counts of tumors in K (trans) maps were higher with Gd-DTPA-BMA than with Gd-DTPA (P<0.001, all readers). Although the K (trans) values were higher with Gd-DTPA-BMA than with Gd-DTPA, there was no statistical significance (P>0.05, all readers). The pixel counts of tumors in V p maps, as well as V p values, showed no obvious difference between the two agents (P>0.05, all readers). Excellent interobserver measurement reproducibility and reliability were demonstrated in the ICC tests. The Gd-DTPA-BMA contrast agent had significantly higher pixel counts of glioma in the K (trans) maps, and an increased tendency for average K (trans) values, indicating that DCE-MRI with Gd-DTPA-BMA may be more suitable and sensitive for the evaluation of glioma.

  4. High-contrast imaging testbed

    SciTech Connect

    Baker, K; Silva, D; Poyneer, L; Macintosh, B; Bauman, B; Palmer, D; Remington, T; Delgadillo-Lariz, M

    2008-01-23

    Several high-contrast imaging systems are currently under construction to enable the detection of extra-solar planets. In order for these systems to achieve their objectives, however, there is considerable developmental work and testing which must take place. Given the need to perform these tests, a spatially-filtered Shack-Hartmann adaptive optics system has been assembled to evaluate new algorithms and hardware configurations which will be implemented in these future high-contrast imaging systems. In this article, construction and phase measurements of a membrane 'woofer' mirror are presented. In addition, results from closed-loop operation of the assembled testbed with static phase plates are presented. The testbed is currently being upgraded to enable operation at speeds approaching 500 hz and to enable studies of the interactions between the woofer and tweeter deformable mirrors.

  5. Ex Vivo Perfusion-Simulation Measurements of Microbubbles as a Scattering Contrast Agent for Grating-Based X-Ray Dark-Field Imaging.

    PubMed

    Velroyen, Astrid; Bech, Martin; Tapfer, Arne; Yaroshenko, Andre; Müller, Mark; Paprottka, Philipp; Ingrisch, Michael; Cyran, Clemens C; Auweter, Sigrid D; Nikolaou, Konstantin; Reiser, Maximilian F; Pfeiffer, Franz

    2015-01-01

    The investigation of dedicated contrast agents for x-ray dark-field imaging, which exploits small-angle scattering at microstructures for contrast generation, is of strong interest in analogy to the common clinical use of high-atomic number contrast media in conventional attenuation-based imaging, since dark-field imaging has proven to provide complementary information. Therefore, agents consisting of gas bubbles, as used in ultrasound imaging for example, are of particular interest. In this work, we investigate an experimental contrast agent based on microbubbles consisting of a polyvinyl-alcohol shell with an iron oxide coating, which was originally developed for multimodal imaging and drug delivery. Its performance as a possible contrast medium for small-animal angiography was examined using a mouse carcass to realistically consider attenuating and scattering background signal. Subtraction images of dark field, phase contrast and attenuation were acquired for a concentration series of 100%, 10% and 1.3% to mimic different stages of dilution in the contrast agent in the blood vessel system. The images were compared to the gold-standard iodine-based contrast agent Solutrast, showing a good contrast improvement by microbubbles in dark-field imaging. This study proves the feasibility of microbubble-based dark-field contrast-enhancement in presence of scattering and attenuating mouse body structures like bone and fur. Therefore, it suggests a strong potential of the use of polymer-based microbubbles for small-animal dark-field angiography.

  6. High-contrast imaging of ɛ Eridani with ground-based instruments

    NASA Astrophysics Data System (ADS)

    Mizuki, T.; Yamada, T.; Carson, J. C.; Kuzuhara, M.; Nakagawa, T.; Nishikawa, J.; Sitko, M. L.; Kudo, T.; Kusakabe, N.; Hashimoto, J.; Abe, L.; Brander, W.; Brandt, T. D.; Egner, S.; Feldt, M.; Goto, M.; Grady, C. A.; Guyon, O.; Hayano, Y.; Hayashi, M.; Hayashi, S. S.; Henning, T.; Hodapp, K. W.; Ishii, M.; Iye, M.; Janson, M.; Kandori, R.; Knapp, G. R.; Kwon, J.; Matsuo, T.; McElwain, M. W.; Miyama, S.; Morino, J.; Moro-Martin, A.; Nishimura, T.; Pyo, T.; Serabyn, E.; Suenaga, T.; Suto, H.; Suzuki, R.; Takahashi, Y. H.; Takami, M.; Takato, N.; Terada, H.; Thalmann, C.; Turner, E. L.; Watanabe, M.; Wisniewski, J.; Takami, H.; Usuda, T.; Tamura, M.

    2016-11-01

    ɛ Eridani is one of the nearest solar-type stars. Its proximity and relatively young age allow high-contrast imaging observations to achieve sensitivities to planets at narrow separations down to an inner radius of 5 AU. Previous observational studies of the system report a dust disk with asymmetric morphology as well as a giant planet with large orbital eccentricity, which may require another massive companion to induce the peculiar morphology and to enhance the large orbital eccentricity. In this paper, we report results from deep high-contrastimaging observations to detect the previously reported planet and search for other unseen less massive companions with Subaru/HiCIAO, Gemini-South/NICI, and VLT/NACO. No positive detection was made, but high-contrast measurements with the CH4S narrow-band filter of HiCIAO achieved sensitivities at 14.7 mag differential magnitude level, at an angular separation of 1.0″. In terms of planetary mass, as determined by cooling evolutionary models, the highest sensitivities were achieved by the Lp broad-band filter of NACO, resulting in sensitivities corresponding to 1.8, 2.8, and 4.5 Mjup at the projected separation of 3 AU, if 200, 400, and 800 Myr is assumed for the age of the system, respectively. We also discuss origins of the dust disk from the detection sensitivity in the planetary mass and find that a less massive eccentric planet is preferred for disk stirring, which is consistent with the orbital parameters of ɛ Eri b claimed from the previous long-term radial velocity monitoring.

  7. Tensor-based tracking of the aorta in phase-contrast MR images

    NASA Astrophysics Data System (ADS)

    Azad, Yoo-Jin; Malsam, Anton; Ley, Sebastian; Rengier, Fabian; Dillmann, Rüdiger; Unterhinninghofen, Roland

    2014-03-01

    The velocity-encoded magnetic resonance imaging (PC-MRI) is a valuable technique to measure the blood flow velocity in terms of time-resolved 3D vector fields. For diagnosis, presurgical planning and therapy control monitoring the patient's hemodynamic situation is crucial. Hence, an accurate and robust segmentation of the diseased vessel is the basis for further methods like the computation of the blood pressure. In the literature, there exist some approaches to transfer the methods of processing DT-MR images to PC-MR data, but the potential of this approach is not fully exploited yet. In this paper, we present a method to extract the centerline of the aorta in PC-MR images by applying methods from the DT-MRI. On account of this, in the first step the velocity vector fields are converted into tensor fields. In the next step tensor-based features are derived and by applying a modified tensorline algorithm the tracking of the vessel course is accomplished. The method only uses features derived from the tensor imaging without the use of additional morphology information. For evaluation purposes we applied our method to 4 volunteer as well as 26 clinical patient datasets with good results. In 29 of 30 cases our algorithm accomplished to extract the vessel centerline.

  8. Hard X-ray phase-contrast imaging with the Compact Light Source based on inverse Compton X-rays

    PubMed Central

    Bech, Martin; Bunk, Oliver; David, Christian; Ruth, Ronald; Rifkin, Jeff; Loewen, Rod; Feidenhans’l, Robert; Pfeiffer, Franz

    2009-01-01

    The first imaging results obtained from a small-size synchrotron are reported. The newly developed Compact Light Source produces inverse Compton X-rays at the intersection point of the counter propagating laser and electron beam. The small size of the intersection point gives a highly coherent cone beam with a few milliradian angular divergence and a few percent energy spread. These specifications make the Compact Light Source ideal for a recently developed grating-based differential phase-contrast imaging method. PMID:19096173

  9. Line-scanning confocal microscopy for high-resolution imaging of upconverting rare-earth-based contrast agents

    NASA Astrophysics Data System (ADS)

    Higgins, Laura M.; Zevon, Margot; Ganapathy, Vidya; Sheng, Yang; Tan, Mei Chee; Riman, Richard E.; Roth, Charles M.; Moghe, Prabhas V.; Pierce, Mark C.

    2015-11-01

    Rare-earth (RE) doped nanocomposites emit visible luminescence when illuminated with continuous wave near-infrared light, making them appealing candidates for use as contrast agents in biomedical imaging. However, the emission lifetime of these materials is much longer than the pixel dwell times used in scanning intravital microscopy. To overcome this limitation, we have developed a line-scanning confocal microscope for high-resolution, optically sectioned imaging of samples labeled with RE-based nanomaterials. Instrument performance is quantified using calibrated test objects. NaYF4:Er,Yb nanocomposites are imaged in vitro, and in ex vivo tissue specimens, with direct comparison to point-scanning confocal microscopy. We demonstrate that the extended pixel dwell time of line-scanning confocal microscopy enables subcellular-level imaging of these nanomaterials while maintaining optical sectioning. The line-scanning approach thus enables microscopic imaging of this emerging class of contrast agents for preclinical studies, with the potential to be adapted for real-time in vivo imaging in the clinic.

  10. Line-scanning confocal microscopy for high-resolution imaging of upconverting rare-earth-based contrast agents

    PubMed Central

    Higgins, Laura M.; Zevon, Margot; Ganapathy, Vidya; Sheng, Yang; Tan, Mei Chee; Riman, Richard E.; Roth, Charles M.; Moghe, Prabhas V.; Pierce, Mark C.

    2015-01-01

    Abstract. Rare-earth (RE) doped nanocomposites emit visible luminescence when illuminated with continuous wave near-infrared light, making them appealing candidates for use as contrast agents in biomedical imaging. However, the emission lifetime of these materials is much longer than the pixel dwell times used in scanning intravital microscopy. To overcome this limitation, we have developed a line-scanning confocal microscope for high-resolution, optically sectioned imaging of samples labeled with RE-based nanomaterials. Instrument performance is quantified using calibrated test objects. NaYF4:Er,Yb nanocomposites are imaged in vitro, and in ex vivo tissue specimens, with direct comparison to point-scanning confocal microscopy. We demonstrate that the extended pixel dwell time of line-scanning confocal microscopy enables subcellular-level imaging of these nanomaterials while maintaining optical sectioning. The line-scanning approach thus enables microscopic imaging of this emerging class of contrast agents for preclinical studies, with the potential to be adapted for real-time in vivo imaging in the clinic. PMID:26603495

  11. Construction and evaluation of a high-energy grating-based x-ray phase-contrast imaging setup

    NASA Astrophysics Data System (ADS)

    Hauke, Christian; Horn, Florian; Pelzer, Georg; Rieger, Jens; Lachner, Sebastian; Ludwig, Veronika; Seifert, Maria; Schuster, Max; Wandner, Johannes; Wolf, Andreas; Weber, Thomas; Michel, Thilo; Anton, Gisela

    2016-03-01

    Interferometric x-ray imaging becomes more and more attractive for applications such as medical imaging or non-destructive testing, because it provides the opportunity to obtain additional information on the internal structure of radiographed objects.12 Therefore, three types of images are acquired: An attenuation image like in conventional x-ray imaging, an image of the differential phase-shift generated by the object and the so called dark-field image, which contains information about the object's granularity even on sub-pixel scale.3 However, most experiments addressing grating-based x-ray phase-contrast imaging with polychromatic sources are restricted to energies up to about 40 keV. For the application of this imaging method to thicker objects like human specimens or dense components, higher tube voltages are required. This is why we designed and constructed a laboratory setup for high energies, which is able to image larger objects.4 To evaluate the performance of the setup, the mean visibility of the field of view was measured for several tube voltages. The result shows that the mean visibility has a peak value of 23% at a tube voltage of 60 kV and is constantly greater than 16% up to a tube voltage of 120 kV. Thus, good image quality is provided even for high energies. To further substantiate the performance of the setup at high energies, a human ex-vivo foot was examined at a tube voltage of 75 kV. The interferometric x-ray images show a good image quality and a promising diagnostic power.

  12. A method for automatic segmentation of nuclei in phase-contrast images based on intensity, convexity and texture.

    PubMed

    Dewan, M Ali Akber; Ahmad, M Omair; Swamy, M N S

    2014-10-01

    This paper presents a method for automatic segmentation of nuclei in phase-contrast images using the intensity, convexity and texture of the nuclei. The proposed method consists of three main stages: preprocessing, h-maxima transformation-based marker controlled watershed segmentation ( h-TMC), and texture analysis. In the preprocessing stage, a top-hat filter is used to increase the contrast and suppress the non-uniform illumination, shading, and other imaging artifacts in the input image. The nuclei segmentation stage consists of a distance transformation, h-maxima transformation and watershed segmentation. These transformations utilize the intensity information and the convexity property of the nucleus for the purpose of detecting a single marker in every nucleus; these markers are then used in the h-TMC watershed algorithm to obtain segments of the nuclei. However, dust particles, imaging artifacts, or prolonged cell cytoplasm may falsely be segmented as nuclei at this stage, and thus may lead to an inaccurate analysis of the cell image. In order to identify and remove these non-nuclei segments, in the third stage a texture analysis is performed, that uses six of the Haralick measures along with the AdaBoost algorithm. The novelty of the proposed method is that it introduces a systematic framework that utilizes intensity, convexity, and texture information to achieve a high accuracy for automatic segmentation of nuclei in the phase-contrast images. Extensive experiments are performed demonstrating the superior performance ( precision = 0.948; recall = 0.924; F1-measure = 0.936; validation based on  ∼ 4850 manually-labeled nuclei) of the proposed method.

  13. Three-dimensional image contrast using biospeckle

    NASA Astrophysics Data System (ADS)

    Godinho, Robson Pierangeli; Braga, Roberto A., Jr.

    2010-09-01

    The biospeckle laser (BSL) has been applied in many areas of knowledge and a variety of approaches has been presented to address the best results in biological and non-biological samples, in fast or slow activities, or else in defined flow of materials or in random activities. The methodologies accounted in the literature consider the apparatus used in the image assembling and the way the collected data is processed. The image processing steps presents in turn a variety of procedures with first or second order statistics analysis, and as well with different sizes of data collected. One way to access the biospeckle in defined flow, such as in capillary blood flow in alive animals, was the adoption of the image contrast technique which uses only one image from the illuminated sample. That approach presents some problems related to the resolution of the image, which is reduced during the image contrast processing. In order to help the visualization of the low resolution image formed by the contrast technique, this work presents the three-dimensional procedure as a reliable alternative to enhance the final image. The work based on a parallel processing, with the generation of a virtual map of amplitudes, and maintaining the quasi-online characteristic of the contrast technique. Therefore, it was possible to generate in the same display the observed material, the image contrast result and in addiction the three-dimensional image with adjustable options of rotation. The platform also offers to the user the possibility to access the 3D image offline.

  14. Laser Image Contrast Enhancement System

    NASA Technical Reports Server (NTRS)

    Kurtz, Robert L. (Inventor); Holmes, Richard R. (Inventor); Witherow, William K. (Inventor)

    2002-01-01

    An optical image enhancement system provides improved image contrast in imaging of a target in high temperature surroundings such as a furnace. The optical system includes a source of vertically polarized light such as laser and a beam splitter for receiving the light and directing the light toward the target. A retardation plate is affixed to a target-facing surface of the beam splitter and a vertical polarizer is disposed along a common optical path with the beam splitter between the retardation plate and the target. A horizontal polarizer disposed in the common optical path, receives light passing through a surface of the beam splitter opposed to the target-facing surface. An image detector is disposed at one end of the optical path. A band pass filter having a band pass filter characteristic matching the frequency of the vertically polarized light source is disposed in the path between the horizontal polarizer and the image detector. The use of circular polarization, together with cross polarizers, enables the reflected light to be passed to the detector while blocking thermal radiation.

  15. Anti-biofouling polymer-decorated lutetium-based nanoparticulate contrast agents for in vivo high-resolution trimodal imaging.

    PubMed

    Liu, Zhen; Dong, Kai; Liu, Jianhua; Han, Xueli; Ren, Jinsong; Qu, Xiaogang

    2014-06-25

    Nanomaterials have gained considerable attention and interest in the development of novel and high-resolution contrast agents for medical diagnosis and prognosis in clinic. A classical urea-based homogeneous precipitation route that combines the merits of in situ thermal decomposition and surface modification is introduced to construct polyethylene glycol molecule (PEG)-decorated hybrid lutetium oxide nanoparticles (PEG-UCNPs). By utilizing the admirable optical and magnetic properties of the yielded PEG-UCNPs, in vivo up-conversion luminescence and T1 -enhanced magnetic resonance imaging of small animals are conducted, revealing obvious signals after subcutaneous and intravenous injection, respectively. Due to the strong X-ray absorption and high atomic number of lanthanide elements, X-ray computed-tomography imaging based on PEG-UCNPs is then designed and carried out, achieving excellent imaging outcome in animal experiments. This is the first example of the usage of hybrid lutetium oxide nanoparticles as effective nanoprobes. Furthermore, biodistribution, clearance route, as well as long-term toxicity are investigated in detail after intravenous injection in a murine model, indicating the overall safety of PEG-UCNPs. Compared with previous lanthanide fluorides, our nanoprobes exhibit more advantages, such as facile construction process and nearly total excretion from the animal body within a month. Taken together, these results promise the use of PEG-UCNPs as a safe and efficient nanoparticulate contrast agent for potential application in multimodal imaging.

  16. Oxidation-Responsive, EuII/III-Based, Multimodal Contrast Agent for Magnetic Resonance and Photoacoustic Imaging

    PubMed Central

    2017-01-01

    We report, for the first time, a multimodal, oxidation-responsive contrast agent for magnetic resonance imaging and photoacoustic imaging that uses the differences in the properties between Eu in the +2 and +3 oxidation states. The enhancement of contrast in T1-weighted magnetic resonance and photoacoustic imaging was observed in the +2 but not in the +3 oxidation state, and the complex is a known chemical exchange saturation transfer agent for magnetic resonance imaging in the +3 oxidation state. PMID:28393130

  17. [Contrastive analysis on soil alkalinization predicting models based on measured reflectance and TM image reflectance].

    PubMed

    Zhang, Fang; Xiong, Hei-Gang; Long, Tao; Lu, Wen-Juan

    2011-01-01

    Based on the monitored data of soil pH and measured Vis-NIR reflectance on spot in Qitai oasis alkalinized area in Xinjiang, as well as comparison of the relationship between measured reflectance and soil pH and the relationship between TM reflectance and soil pH, both of the reflectance multivariate linear regression models were built to evaluate soil alkalinization level, and the model accuracy of pH fitting was discussed with error inspection of post-sample. The results showed that there is a significant positive correlation between soil pH and reflectance. With pH rising the reflectance increased concurrently. So the alkalinization soil characterized by hardening had good spectral response characteristics. Both measured reflectance and TM image reflectance had good potential ability for change detection of the alkalinization soil. The pH predicting model of measured reflectance had higher accuracy and the major error was from different hardening state. If building model by TM reflectance directly, the accuracy of fitting was lower because of the vegetation information in image spectrum. With the vegetation factor removed with NDVI, the accuracy of TM predicting model was near the accuracy of measured reflectance predicting model, and both of the model levels were good.

  18. SU-E-T-407: Evaluation of the Stopping Power and Imaging Visibility for Iodine Based Contrast in Proton Therapy

    SciTech Connect

    Singh, H; Zhao, L; Rana, S; Chacko, M; Zheng, Y

    2015-06-15

    Purpose: The purpose of this study was to investigate the difference between calculated and measured relative linear stopping power (RLSP) for contrast medium in proton therapy. Furthermore, the visibility for different concentrations in prostate phantom on orthogonal X-ray system was evaluated Methods and Materials: In prostate cancer patient, rectal balloon along with the contrast media was used to visualize the balloon position, thus facilitating the patient setup during each fraction of the uniform scanning proton treatment. There were no fiducial markers implanted in the prostate for this patient. A blue wax phantom with outer dimensions 10cm(H) x 14.5cm(L) x 10cm(W) was made in house. To hold iodine based contrast solution, a rectangular shaped hole with dimensions 7cm(H) x 8cm(L) x 4cm(W) was made inside the phantom. Organically bound 8.5% iodine based Cystografin Dilute contrast agent with molecular formula C11H9I3N2O4.C7H17NO5 was used in this study. Six solutions were prepared; each mixture of water and iodine based contrast agent at different concentrations as 0%, 5%, 10%, 20%, 30% and 50%. During computed tomographic(CT) simulation, solutions were placed together at the isocenter of CT and scanned at 120kVp using the same protocol as for prostate cancer patients. The treatment planning was done in CMS-XiO system. Multi-layer-ion-chamber (MLIC) was used to measure residual proton range. Results: The 50% concentration contrast solution was used during treatment for better visualization on orthogonal X-ray image. The measured RLSP for 5%, 10%, 20%, 30% & 50% solutions were 1.005, 1.010, 1.018, 1.023 & 1.033; and similarly calculated RLSP from XiO were 1.090, 1.135, 1.222, 1.299 & 1.448 respectively. Conclusion: The treatment planning system could overestimates the relative stopping power of contrast solution with high concentrations. It is recommended to override the contrast with measured RLSP for high atomic number based contrast solution in treatment

  19. Simulations of x-ray speckle-based dark-field and phase-contrast imaging with a polychromatic beam

    SciTech Connect

    Zdora, Marie-Christine; Thibault, Pierre; Pfeiffer, Franz; Zanette, Irene

    2015-09-21

    Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by speckle tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.

  20. Simulations of x-ray speckle-based dark-field and phase-contrast imaging with a polychromatic beam

    NASA Astrophysics Data System (ADS)

    Zdora, Marie-Christine; Thibault, Pierre; Pfeiffer, Franz; Zanette, Irene

    2015-09-01

    Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by speckle tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.

  1. Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Choma, Michael A.; Suter, Melissa J.; Vakoc, Benjamin J.; Bouma, Brett E.; Tearney, Guillermo J.

    2010-09-01

    Drosophila melanogaster (fruit fly) is a central organism in biology and is becoming increasingly important in the cardiovascular sciences. Prior work in optical imaging of the D. melanogaster heart has focused on static and dynamic structural anatomy. In the study, it is demonstrated that Doppler optical coherence tomography can quantify dynamic heart wall velocity and hemolymph flow in adult D. melanogaster. Since hemolymph is optically transparent, a novel exogenous contrast technique is demonstrated to increase the backscatter-based intracardiac Doppler flow signal. The results presented here open up new possibilities for functional cardiovascular phenotyping of normal and mutant D. melanogaster.

  2. Spectral embedding based active contour (SEAC) for lesion segmentation on breast dynamic contrast enhanced magnetic resonance imaging

    PubMed Central

    Agner, Shannon C.; Xu, Jun; Madabhushi, Anant

    2013-01-01

    Purpose: Segmentation of breast lesions on dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) is the first step in lesion diagnosis in a computer-aided diagnosis framework. Because manual segmentation of such lesions is both time consuming and highly susceptible to human error and issues of reproducibility, an automated lesion segmentation method is highly desirable. Traditional automated image segmentation methods such as boundary-based active contour (AC) models require a strong gradient at the lesion boundary. Even when region-based terms are introduced to an AC model, grayscale image intensities often do not allow for clear definition of foreground and background region statistics. Thus, there is a need to find alternative image representations that might provide (1) strong gradients at the margin of the object of interest (OOI); and (2) larger separation between intensity distributions and region statistics for the foreground and background, which are necessary to halt evolution of the AC model upon reaching the border of the OOI. Methods: In this paper, the authors introduce a spectral embedding (SE) based AC (SEAC) for lesion segmentation on breast DCE-MRI. SE, a nonlinear dimensionality reduction scheme, is applied to the DCE time series in a voxelwise fashion to reduce several time point images to a single parametric image where every voxel is characterized by the three dominant eigenvectors. This parametric eigenvector image (PrEIm) representation allows for better capture of image region statistics and stronger gradients for use with a hybrid AC model, which is driven by both boundary and region information. They compare SEAC to ACs that employ fuzzy c-means (FCM) and principal component analysis (PCA) as alternative image representations. Segmentation performance was evaluated by boundary and region metrics as well as comparing lesion classification using morphological features from SEAC, PCA+AC, and FCM+AC. Results: On a cohort of 50

  3. Magnetic nanoparticles as contrast agents in biomedical imaging: recent advances in iron- and manganese-based magnetic nanoparticles.

    PubMed

    Felton, Charlette; Karmakar, Alokita; Gartia, Yashraj; Ramidi, Punnamchandar; Biris, Alexandru S; Ghosh, Anindya

    2014-05-01

    Improvements in diagnostic measures for biomedical applications have been investigated in various studies for better interpretations of biological abnormalities and several medical conditions. The use of imaging techniques, such as magnetic resonance imaging (MRI), is widespread and becoming a standard procedure for such specialized applications. A major avenue being studied in MRI is the use of magnetic nanoparticles (NPs) as contrast agents (CAs). Among various approaches, current research also incorporates use of superparamagnetic iron oxide NPs and manganese-based NPs with biocompatible coatings for improved stability and reduced biodegradation when exposed to a biological environment. In this review, recent advances with these types of magnetic NPs and their potential use as CAs in MRI are reported, as well as new insights into the selectivity and cellular transport mechanism that occurs following injection.

  4. In vivo detection of copper ions by magnetic resonance imaging using a prion-based contrast agent.

    PubMed

    Makino, Satoshi; Umemoto, Tomohiro; Yamada, Hiroshi; Yezdimer, Eric M; Tooyama, Ikuo

    2012-10-01

    Abnormal distributions of transition metals inside the body are potential diagnostic markers for several diseases, including Alzheimer's disease, Parkinson's disease, Wilson's disease, and cancer. In this article, we demonstrate that P57/Gd, a novel prion-based contrast agent, can selectively image tissues with excessive copper accumulation using magnetic resonance imaging (MRI). P57/Gd selectivity binds copper(II) over other physiologically relevant cations such as zinc, iron, manganese, and calcium. To simulate a metabolic copper disorder, we treated mice with an intraperitoneal injection of a CuSO(4) solution to induce a renal copper overload. The MRI signal intensities from the renal cortex and medulla of copper spiked animals that were administered P57/Gd were found to correlate with the ex vivo copper concentrations determined by inductively coupled plasma mass spectrometry.

  5. ESTIMATES OF THE PLANET YIELD FROM GROUND-BASED HIGH-CONTRAST IMAGING OBSERVATIONS AS A FUNCTION OF STELLAR MASS

    SciTech Connect

    Crepp, Justin R.; Johnson, John Asher

    2011-06-01

    We use Monte Carlo simulations to estimate the number of extrasolar planets that are directly detectable in the solar neighborhood using current and forthcoming high-contrast imaging instruments. Our calculations take into consideration the important factors that govern the likelihood for imaging a planet, including the statistical properties of stars in the solar neighborhood, correlations between star and planet properties, observational effects, and selection criteria. We consider several different ground-based surveys, both biased and unbiased, and express the resulting planet yields as a function of stellar mass. Selecting targets based on their youth and visual brightness, we find that strong correlations between star mass and planet properties are required to reproduce high-contrast imaging results to date (i.e., HR 8799, {beta} Pic). Using the most recent empirical findings for the occurrence rate of gas-giant planets from radial velocity (RV) surveys, our simulations indicate that naive extrapolation of the Doppler planet population to semimajor axes accessible to high-contrast instruments provides an excellent agreement between simulations and observations using present-day contrast levels. In addition to being intrinsically young and sufficiently bright to serve as their own beacon for adaptive optics correction, A-stars have a high planet occurrence rate and propensity to form massive planets in wide orbits, making them ideal targets. The same effects responsible for creating a multitude of detectable planets around massive stars conspire to reduce the number orbiting low-mass stars. However, in the case of a young stellar cluster, where targets are approximately the same age and situated at roughly the same distance, MK-stars can easily dominate the number of detections because of an observational bias related to small number statistics. The degree to which low-mass stars produce the most planet detections in this special case depends upon whether

  6. Magnetic resonance imaging findings of remnants of an intradural oil-based contrast agent: report of a case

    PubMed Central

    Oo, Myint; Wang, Zhuo; Sakakibara, Toshihiko; Kasai, Yuichi

    2012-01-01

    Background Myodil (iophendylate), an oil-based positive contrast media, now discontinued, was widely used for performing myelography 30–70 years ago. We identified this agent as the explanation for uncommon magnetic resonance imaging (MRI) findings in a patient with thoracic spinal fracture. Design Case report and literature review. Findings An 81-year-old man complained of back pain after falling down stairs. Anamnesis revealed that he had undergone myelography with an oil-based contrast agent about 60 years previously as a part of the diagnostic workup for back pain and sudden onset of gait difficulty. Plain radiography of the thoraco-lumbar spine showed a fracture of the eleventh thoracic vertebra and a radio-opaque, oval shadow at the level of the T9–T10 vertebrae. Many small radio-opaque dots with the appearance of a string of pearls were seen from T8 to L3 vertebrae. MRI revealed a sharply demarcated intradural extramedullary mass, of approximately 5 mm in diameter on the left side of the dura in the region of the T9–T10. The mass showed high signal intensity on T1-weighted MRI, and low signal intensity on T2-weighted MRI. Conclusions Increased awareness of this rare presentation of procedures performed in the past is essential when atypical radiographic images are encountered. This case illustrates rare sequelae of Myodil use manifesting decades after administration. PMID:22333888

  7. Equilibrium-phase MR angiography: Comparison of unspecific extracellular and protein-binding gadolinium-based contrast media with respect to image quality.

    PubMed

    Erb-Eigner, Katharina; Taupitz, Matthias; Asbach, Patrick

    2016-01-01

    The purpose of this study was to compare contrast and image quality of whole-body equilibrium-phase high-spatial-resolution MR angiography using a non-protein-binding unspecific extracellular gadolinium-based contrast medium with that of two contrast media with different protein-binding properties. 45 patients were examined using either 15 mL of gadobutrol (non-protein-binding, n = 15), 32 mL of gadobenate dimeglumine (weakly protein binding, n = 15) or 11 mL gadofosveset trisodium (protein binding, n = 15) followed by equilibrium-phase high-spatial-resolution MR-angiography of four consecutive anatomic regions. The time elapsed between the contrast injection and the beginning of the equilibrium-phase image acquisition in the respective region was measured and was up to 21 min. Signal intensity was measured in two vessels per region and in muscle tissue. Relative contrast (RC) values were calculated. Vessel contrast, artifacts and image quality were rated by two radiologists in consensus on a five-point scale. Compared with gadobutrol, gadofosveset trisodium revealed significantly higher RC values only when acquired later than 15 min after bolus injection. Otherwise, no significant differences between the three contrast media were found regarding vascular contrast and image quality. Equilibrium-phase high-spatial-resolution MR-angiography using a weakly protein-binding or even non-protein-binding contrast medium is equivalent to using a stronger protein-binding contrast medium when image acquisition is within the first 15 min after contrast injection, and allows depiction of the vasculature with high contrast and image quality. The protein-binding contrast medium was superior for imaging only later than 15 min after contrast medium injection.

  8. In-Vivo Imaging of Cell Migration Using Contrast Enhanced MRI and SVM Based Post-Processing.

    PubMed

    Weis, Christian; Hess, Andreas; Budinsky, Lubos; Fabry, Ben

    2015-01-01

    The migration of cells within a living organism can be observed with magnetic resonance imaging (MRI) in combination with iron oxide nanoparticles as an intracellular contrast agent. This method, however, suffers from low sensitivity and specificty. Here, we developed a quantitative non-invasive in-vivo cell localization method using contrast enhanced multiparametric MRI and support vector machines (SVM) based post-processing. Imaging phantoms consisting of agarose with compartments containing different concentrations of cancer cells labeled with iron oxide nanoparticles were used to train and evaluate the SVM for cell localization. From the magnitude and phase data acquired with a series of T2*-weighted gradient-echo scans at different echo-times, we extracted features that are characteristic for the presence of superparamagnetic nanoparticles, in particular hyper- and hypointensities, relaxation rates, short-range phase perturbations, and perturbation dynamics. High detection quality was achieved by SVM analysis of the multiparametric feature-space. The in-vivo applicability was validated in animal studies. The SVM detected the presence of iron oxide nanoparticles in the imaging phantoms with high specificity and sensitivity with a detection limit of 30 labeled cells per mm3, corresponding to 19 μM of iron oxide. As proof-of-concept, we applied the method to follow the migration of labeled cancer cells injected in rats. The combination of iron oxide labeled cells, multiparametric MRI and a SVM based post processing provides high spatial resolution, specificity, and sensitivity, and is therefore suitable for non-invasive in-vivo cell detection and cell migration studies over prolonged time periods.

  9. Visualization of small lesions in rat cartilage by means of laboratory-based x-ray phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Marenzana, Massimo; Hagen, Charlotte K.; Das Neves Borges, Patricia; Endrizzi, Marco; Szafraniec, Magdalena B.; Ignatyev, Konstantin; Olivo, Alessandro

    2012-12-01

    Being able to quantitatively assess articular cartilage in three-dimensions (3D) in small rodent animal models, with a simple laboratory set-up, would prove extremely important for the development of pre-clinical research focusing on cartilage pathologies such as osteoarthritis (OA). These models are becoming essential tools for the development of new drugs for OA, a disease affecting up to 1/3 of the population older than 50 years for which there is no cure except prosthetic surgery. However, due to limitations in imaging technology, high-throughput 3D structural imaging has not been achievable in small rodent models, thereby limiting their translational potential and their efficiency as research tools. We show that a simple laboratory system based on coded-aperture x-ray phase contrast imaging (CAXPCi) can correctly visualize the cartilage layer in slices of an excised rat tibia imaged both in air and in saline solution. Moreover, we show that small, surgically induced lesions are also correctly detected by the CAXPCi system, and we support this finding with histopathology examination. Following these successful proof-of-concept results in rat cartilage, we expect that an upgrade of the system to higher resolutions (currently underway) will enable extending the method to the imaging of mouse cartilage as well. From a technological standpoint, by showing the capability of the system to detect cartilage also in water, we demonstrate phase sensitivity comparable to other lab-based phase methods (e.g. grating interferometry). In conclusion, CAXPCi holds a strong potential for being adopted as a routine laboratory tool for non-destructive, high throughput assessment of 3D structural changes in murine articular cartilage, with a possible impact in the field similar to the revolution that conventional microCT brought into bone research.

  10. Contrast-enhanced Reformatted MR Images for Preoperative Assessment of the Bridging Veins of the Skull Base.

    PubMed

    Wangaryattawanich, Pattana; Chavali, Lakshmi S; Shah, Komal B; Gogia, Bhanu; Valenzuela, Raul F; DeMonte, Franco; Kumar, Ashok J; Hayman, L Anne

    2016-01-01

    Magnetic resonance (MR) venography and computed tomographic (CT) venography are suited for displaying the convexity veins that drain the medial and lateral surfaces of the brain hemispheres. However, such is not the case for the bridging veins of the skull base. Technical factors prevent contrast material-enhanced MR or CT images obtained in standard axial, coronal, and sagittal planes from fully displaying the curved pathways of these clinically important venous structures. This limitation can be overcome by using a reconstruction technique that depicts these venous structures and their interconnections. Curved and multiplanar reformatted images that distill the important venous features often require knowledgeable manipulation of source images by an operator who is familiar with numerous venous variants and their surgical implications. The normal anatomy of the draining veins is detailed-anatomy that radiologists must master before they can show the surgeon the important venous anatomy that is often missing at standard imaging; this information will foster better communication between radiologists and their surgical colleagues. As a practical matter, the skull base veins are arbitrarily subdivided into those that are at greatest risk with the pterional approach and the subtemporal approach, respectively. These approaches can be expanded to define connections between the superficial venous system and the other valveless venous networks that drain the deep portions of the cerebral hemisphere, the scalp, face, muscles of the neck, diploë of the skull, and meninges. As radiologists gain experience, their image interpretations should mature beyond simple analysis of the primary hemodynamic changes induced by intraoperative sacrifice or injury.

  11. Improving photoacoustic imaging contrast of brachytherapy seeds

    NASA Astrophysics Data System (ADS)

    Pan, Leo; Baghani, Ali; Rohling, Robert; Abolmaesumi, Purang; Salcudean, Septimiu; Tang, Shuo

    2013-03-01

    Prostate brachytherapy is a form of radiotherapy for treating prostate cancer where the radiation sources are seeds inserted into the prostate. Accurate localization of seeds during prostate brachytherapy is essential to the success of intraoperative treatment planning. The current standard modality used in intraoperative seeds localization is transrectal ultrasound. Transrectal ultrasound, however, suffers in image quality due to several factors such speckle, shadowing, and off-axis seed orientation. Photoacoustic imaging, based on the photoacoustic phenomenon, is an emerging imaging modality. The contrast generating mechanism in photoacoustic imaging is optical absorption that is fundamentally different from conventional B-mode ultrasound which depicts changes in acoustic impedance. A photoacoustic imaging system is developed using a commercial ultrasound system. To improve imaging contrast and depth penetration, absorption enhancing coating is applied to the seeds. In comparison to bare seeds, approximately 18.5 dB increase in signal-to-noise ratio as well as a doubling of imaging depth are achieved. Our results demonstrate that the coating of the seeds can further improve the discernibility of the seeds.

  12. Three-dimensional shear wave imaging based on full-field laser speckle contrast imaging with one-dimensional mechanical scanning.

    PubMed

    Chao, Pei-Yu; Li, Pai-Chi

    2016-08-22

    The high imaging resolution and motion sensitivity of optical-based shear wave detection has made it an attractive technique in biomechanics studies with potential for improving the capabilities of shear wave elasticity imaging. In this study we implemented laser speckle contrast imaging for two-dimensional (X-Z) tracking of transient shear wave propagation in agarose phantoms. The mechanical disturbances induced by the propagation of the shear wave caused temporal and spatial fluctuations in the local speckle pattern, which manifested as local blurring. By mechanically moving the sample in the third dimension (Y), and performing two-dimensional shear wave imaging at every scan position, the three-dimensional shear wave velocity distribution of the phantom could be reconstructed. Based on comparisons with the reference shear wave velocity measurements obtained using a commercial ultrasound shear wave imaging system, the developed system can estimate the shear wave velocity with an error of less than 6% for homogeneous phantoms with shear moduli ranging from 1.52 kPa to 7.99 kPa. The imaging sensitivity of our system makes it capable of measuring small variations in shear modulus; the estimated standard deviation of the shear modulus was found to be less than 0.07 kPa. A submillimeter spatial resolution for three-dimensional shear wave imaging has been achieved, as demonstrated by the ability to detect a 1-mm-thick stiff plate embedded inside heterogeneous agarose phantoms.

  13. Endoscopy imaging intelligent contrast improvement.

    PubMed

    Sheraizin, S; Sheraizin, V

    2005-01-01

    In this paper, we present a medical endoscopy video contrast improvement method that provides intelligent automatic adaptive contrast control. The method fundamentals are video data clustering and video data histogram modification. The video data clustering allows an effective use the low noise two channel contrast enhancement processing. The histogram analysis permitted to determine the video exposure type for simple and complicated contrast distribution. We determined the needed gamma value for automatic local area contrast improvement for the following exposure types: dark, normal, light, dark light, dark normal etc. The experimental results of medical endoscopy video processing allow defining the automatic gamma control range from 0.5 to 2.0.

  14. Pair-Wise, Deformable Mirror, Image Plane-Based Diversity Electric Field Estimation for High Contrast Coronagraphy

    NASA Technical Reports Server (NTRS)

    Give'on, Amir; Kern, Brian D.; Shaklan, Stuart

    2011-01-01

    In this paper we describe the complex electric field reconstruction from image plane intensity measurements for high contrast coronagraphic imaging. A deformable mirror (DM) surface is modied with pairs of complementary shapes to create diversity in the image plane of the science camera where the intensity of the light is measured. Along with the Electric Field Conjugation correction algorithm, this estimation method has been used in various high contrast imaging testbeds to achieve the best contrasts to date both in narrow and in broad band light. We present the basic methodology of estimation in easy to follow list of steps, present results from HCIT and raise several open quations we are confronted with using this method.

  15. Visual Performance-Based Image Enhancement Methodology: An Investigation of Contrast Enhancement Algorithms

    DTIC Science & Technology

    2006-03-01

    484 (April 2001). 8. F. Lamberti, B. Montrucchio, and A. Sanna, "BBFHE: Block-based binomial filtering histogram equalization", WSEAS Transaction on Information Science and Applications, 1(6), 1591-1596, 2004.

  16. Amyloid-β plaque deposition measured using propagation-based X-ray phase contrast CT imaging

    PubMed Central

    Astolfo, Alberto; Lathuilière, Aurélien; Laversenne, Vanessa; Schneider, Bernard; Stampanoni, Marco

    2016-01-01

    Amyloid beta accumulation into insoluble plaques (Aβp) is known to play a significant role in the pathological process in Alzheimer’s disease (AD). The presence of Aβp is also one of the neuropathological hallmarks for the disease. AD final diagnosis is generally acknowledged after the evaluation of Aβp deposition in the brain. Insoluble Aβp accumulation may also concur to cause AD as postulated in the so-called amyloid hypothesis. Therefore, the visualization, evaluation and quantification of Aβp are nowadays the keys for a better understanding of the disease, which may point to a possible cure for AD in the near future. Synchrotron-based X-ray phase contrast (XPC) has been demonstrated as the only imaging method that can retrieve the Aβp signal with high spatial resolution (up to 10 µm), high sensitivity and three-dimensional information at the same time. Although at the moment XPC is suitable for ex vivo samples only, it may develop into an alternative to positron emission tomography and magnetic resonance imaging in Aβp imaging. In this contribution the possibility of using synchrotron-based X-ray phase propagation computed tomography to visualize and measure Aβp on mouse brains is presented. A careful setup optimization for this application leads to a significant improvement of spatial resolution (∼1 µm), data acquisition speed (five times faster), X-ray dose (five times lower) and setup complexity, without a substantial loss in sensitivity when compared with the classic implementation of grating-based X-ray interferometry. PMID:27140162

  17. Facile Preparation of a New Gadofullerene-Based Magnetic Resonance Imaging Contrast Agent with High 1H Relaxivity

    PubMed Central

    Shu, Chunying; Corwin, Frank D.; Zhang, Jianfei; Chen, Zhijian; Reid, Jonathan E.; Sun, Minghao; Xu, Wei; Sim, Jae Hyun; Wang, Chunru; Fatouros, Panos P.; Esker, Alan R.; Gibson, Harry W.; Dorn, Harry C.

    2009-01-01

    A new magnetic resonance imaging (MRI) contrast agent based on the trimetallic nitride templated (TNT) metallofullerene, Gd3N@C80, was synthesized by a facile method in high yield. The observed longitudinal and transverse relaxivities, r1 and r2, for water hydrogens in the presence of the water-soluble gadofullerene 2, Gd3N@C80(OH)~26(CH2CH2COOM)~16 (M = Na or H), are 207 and 282 mM-1s-1 (per C80 cage) at 2.4 T, respectively; these values are 50 times larger than those of Gd3+ poly(aminocarboxylate) complexes, such as commercial Omniscan® and Magnevist®. This high 1H relaxivity for this new hydroxylated and carboxylated gadofullerene derivative provides high signal enhancement at significantly lower Gd concentration as demonstrated by in vitro and in vivo MRI studies. Dynamic light scattering data reveal a unimodal size distribution with an average hydrodynamic radius of ca. 78 nm in pure water (pH = 7), which is significantly different from other hydroxylated or carboxylated fullerene and metallofullerene derivatives reported to date. Agarose gel infusion results indicate that the gadofullerene 2 displayed diffusion properties different from that of commercial Omniscan® and those of PEG5000 modified Gd3N@C80. The reactive carboxyl functionality present on this highly efficient contrast agent may also serve as a precursor for biomarker tissue-targeting purposes. PMID:19445504

  18. Small intestine contrast injection (image)

    MedlinePlus

    ... and throat, through the stomach into the small intestine. When in place, contrast dye is introduced and ... means of demonstrating whether or not the small intestine is normal when abnormality is suspected.

  19. Image fusion for dynamic contrast enhanced magnetic resonance imaging

    PubMed Central

    Twellmann, Thorsten; Saalbach, Axel; Gerstung, Olaf; Leach, Martin O; Nattkemper, Tim W

    2004-01-01

    Background Multivariate imaging techniques such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been shown to provide valuable information for medical diagnosis. Even though these techniques provide new information, integrating and evaluating the much wider range of information is a challenging task for the human observer. This task may be assisted with the use of image fusion algorithms. Methods In this paper, image fusion based on Kernel Principal Component Analysis (KPCA) is proposed for the first time. It is demonstrated that a priori knowledge about the data domain can be easily incorporated into the parametrisation of the KPCA, leading to task-oriented visualisations of the multivariate data. The results of the fusion process are compared with those of the well-known and established standard linear Principal Component Analysis (PCA) by means of temporal sequences of 3D MRI volumes from six patients who took part in a breast cancer screening study. Results The PCA and KPCA algorithms are able to integrate information from a sequence of MRI volumes into informative gray value or colour images. By incorporating a priori knowledge, the fusion process can be automated and optimised in order to visualise suspicious lesions with high contrast to normal tissue. Conclusion Our machine learning based image fusion approach maps the full signal space of a temporal DCE-MRI sequence to a single meaningful visualisation with good tissue/lesion contrast and thus supports the radiologist during manual image evaluation. PMID:15494072

  20. Synthesis and Evaluation of GdIII-Based Magnetic Resonance Contrast Agents for Molecular Imaging of Prostate-Specific Membrane Antigen**

    PubMed Central

    Ngen, Ethel J.; Rotz, Matthew W.; Kakkad, Samata; Lisok, Ala; Pracitto, Richard; Pullambhatla, Mrudula; Chen, Zhengping; Shah, Tariq; Artemov, Dmitri; Meade, Thomas J.; Bhujwalla, Zaver M.; Pomper, Martin G.

    2016-01-01

    Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate-specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR-based molecular imaging. We have synthesized three new high-affinity, low-molecular-weight GdIII-based PSMA-targeted contrast agents containing one to three GdIII chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA-based MR molecular imaging. PMID:26212031

  1. High-Performance Hybrid Bismuth-Carbon Nanotube Based Contrast Agent for X-ray CT Imaging.

    PubMed

    Hernández-Rivera, Mayra; Kumar, Ish; Cho, Stephen Y; Cheong, Benjamin Y; Pulikkathara, Merlyn X; Moghaddam, Sakineh E; Whitmire, Kenton H; Wilson, Lon J

    2017-02-22

    Carbon nanotubes (CNTs) have been used for a plethora of biomedical applications, including their use as delivery vehicles for drugs, imaging agents, proteins, DNA, and other materials. Here, we describe the synthesis and characterization of a new CNT-based contrast agent (CA) for X-ray computed tomography (CT) imaging. The CA is a hybrid material derived from ultrashort single-walled carbon nanotubes (20-80 nm long, US-tubes) and Bi(III) oxo-salicylate clusters with four Bi(III) ions per cluster (Bi4C). The element bismuth was chosen over iodine, which is the conventional element used for CT CAs in the clinic today due to its high X-ray attenuation capability and its low toxicity, which makes bismuth a more-promising element for new CT CA design. The new CA contains 20% by weight bismuth with no detectable release of bismuth after a 48 h challenge by various biological media at 37 °C, demonstrating the presence of a strong interaction between the two components of the hybrid material. The performance of the new Bi4C@US-tubes solid material as a CT CA has been assessed using a clinical scanner and found to possess an X-ray attenuation ability of >2000 Hounsfield units (HU).

  2. Diffraction contrast imaging using virtual apertures.

    PubMed

    Gammer, Christoph; Burak Ozdol, V; Liebscher, Christian H; Minor, Andrew M

    2015-08-01

    Two methods on how to obtain the full diffraction information from a sample region and the associated reconstruction of images or diffraction patterns using virtual apertures are demonstrated. In a STEM-based approach, diffraction patterns are recorded for each beam position using a small probe convergence angle. Similarly, a tilt series of TEM dark-field images is acquired. The resulting datasets allow the reconstruction of either electron diffraction patterns, or bright-, dark- or annular dark-field images using virtual apertures. The experimental procedures of both methods are presented in the paper and are applied to a precipitation strengthened and creep deformed ferritic alloy with a complex microstructure. The reconstructed virtual images are compared with conventional TEM images. The major advantage is that arbitrarily shaped virtual apertures generated with image processing software can be designed without facing any physical limitations. In addition, any virtual detector that is specifically designed according to the underlying crystal structure can be created to optimize image contrast.

  3. Dendrimer-Based Responsive MRI Contrast Agents (G1-G4) for Biosensor Imaging of Redundant Deviation in Shifts (BIRDS)

    PubMed Central

    Huang, Yuegao; Coman, Daniel; Hyder, Fahmeed; Ali, Meser M.

    2016-01-01

    Biosensor imaging of redundant deviation in shifts (BIRDS) is a molecular imaging platform for magnetic resonance that utilizes unique properties of low molecular weight paramagnetic monomers by detecting hyperfine-shifted nonexchangeable protons and transforming the chemical shift information to reflect its microenvironment (e.g., via temperature, pH, etc.). To optimize translational biosensing potential of BIRDS we examined if this detection scheme observed with monomers can be extended onto dendrimers, which are versatile and biocompatible macromolecules with modifiable surface for molecular imaging and drug delivery. Here we report on feasibility of paramagnetic dendrimers for BIRDS. The results show that BIRDS is resilient with paramagnetic dendrimers up to the fourth generation (i.e., G1-G4), where the model dendrimer and chelate were based on poly(amido amine) (PAMAM) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA4−) complexed with thulium ion (Tm3+). Temperature sensitivities of two prominent signals of Gn-PAMAM-(TmDOTA−)x (where n = 1–4, x = 6–39) were comparable to that of prominent signals in TmDOTA−. Transverse relaxation times of the coalesced nonexchangeable protons on Gn-PAMAM-(TmDOTA−)x were relatively short to provide signal-to-noise ratio that was comparable to or better than that of TmDOTA−. A fluorescent dye, rhodamine, was conjugated to a G2-PAMAM-(TmDOTA)12 to create a dual-modality nanosized contrast agent. BIRDS properties of the dendrimer were unaltered with rhodamine conjugation. Purposely designed paramagnetic dendrimers for BIRDS in conjunction with novel macromolecular surface modification for functional ligands/drugs could potentially be used for biologically compatible theranostic sensors. PMID:26497087

  4. Phase contrast image guidance for synchrotron microbeam radiotherapy

    NASA Astrophysics Data System (ADS)

    Pelliccia, Daniele; Crosbie, Jeffrey C.; Larkin, Kieran G.

    2016-08-01

    Recent image guidance developments for preclinical synchrotron microbeam radiotherapy represent a necessary step for future clinical translation of the technique. Image quality can be further improved using x-ray phase contrast, which is readily available at synchrotron facilities. We here describe a methodology for phase contrast image guidance at the Imaging and Medical Beamline at the Australian Synchrotron. Differential phase contrast is measured alongside conventional attenuation and used to improve the image quality. Post-processing based on the inverse Riesz transform is employed on the measured data to obtain noticeably sharper images. The procedure is extremely well suited for applications such as image guidance which require both visual assessment and sample alignment based on semi automatic image registration. Moreover, our approach can be combined with all other differential phase contrast imaging techniques, in all cases where a quantitative evaluation of the refractive index is not required.

  5. Synthesis, Characterization, In Vitro Phantom Imaging, and Cytotoxicity of A Novel Graphene-Based Multimodal Magnetic Resonance Imaging - X-Ray Computed Tomography Contrast Agent

    PubMed Central

    Lalwani, Gaurav; Sundararaj, Joe Livingston; Schaefer, Kenneth; Button, Terry; Sitharaman, Balaji

    2014-01-01

    Graphene nanoplatelets (GNPs), synthesized using potassium permanganate-based oxidation and exfoliation followed by reduction with hydroiodic acid (rGNP-HI), have intercalated manganese ions within the graphene sheets, and upon functionalization with iodine, show excellent potential as biomodal contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). Structural characterization of rGNP-HI nanoparticles with low- and high-resolution transmission electron microscope (TEM) showed disc-shaped nanoparticles (average diameter, 200 nm, average thickness, 3 nm). Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of intercalated manganese. Raman spectroscopy and X-ray diffraction (XRD) analysis of rGNP-HI confirmed the reduction of oxidized GNPs (O-GNPs), absence of molecular and physically adsorbed iodine, and the functionalization of graphene with iodine as polyiodide complexes (I3− and I5−). Manganese and iodine content were quantified as 5.1 ± 0.5 and 10.54 ± 0.87 wt% by inductively-coupled plasma optical emission spectroscopy and ion-selective electrode measurements, respectively. In vitro cytotoxicity analysis, using absorbance (LDH assay) and fluorescence (calcein AM) based assays, performed on NIH3T3 mouse fibroblasts and A498 human kidney epithelial cells, showed CD50 values of rGNP-HI between 179-301 µg/ml, depending on the cell line and the cytotoxicity assay. CT and MRI phantom imaging of rGNP-HI showed high CT (approximately 3200% greater than HI at equimolar iodine concentration) and MRI (approximately 59% greater than equimolar Mn2+ solution) contrast. These results open avenues for further in vivo safety and efficacy studies towards the development of carbon nanostructure-based multimodal MRI-CT contrast agents. PMID:24999431

  6. Automated segmentation of middle hepatic vein in non-contrast x-ray CT images based on an atlas-driven approach

    NASA Astrophysics Data System (ADS)

    Kitagawa, Teruhiko; Zhou, Xiangrong; Hara, Takeshi; Fujita, Hiroshi; Yokoyama, Ryujiro; Kondo, Hiroshi; Kanematsu, Masayuki; Hoshi, Hiroaki

    2008-03-01

    In order to support the diagnosis of hepatic diseases, understanding the anatomical structures of hepatic lobes and hepatic vessels is necessary. Although viewing and understanding the hepatic vessels in contrast media-enhanced CT images is easy, the observation of the hepatic vessels in non-contrast X-ray CT images that are widely used for the screening purpose is difficult. We are developing a computer-aided diagnosis (CAD) system to support the liver diagnosis based on non-contrast X-ray CT images. This paper proposes a new approach to segment the middle hepatic vein (MHV), a key structure (landmark) for separating the liver region into left and right lobes. Extraction and classification of hepatic vessels are difficult in non-contrast X-ray CT images because the contrast between hepatic vessels and other liver tissues is low. Our approach uses an atlas-driven method by the following three stages. (1) Construction of liver atlases of left and right hepatic lobes using a learning datasets. (2) Fully-automated enhancement and extraction of hepatic vessels in liver regions. (3) Extraction of MHV based on the results of (1) and (2). The proposed approach was applied to 22 normal liver cases of non-contrast X-ray CT images. The preliminary results show that the proposed approach achieves the success in 14 cases for MHV extraction.

  7. Phase contrast imaging of cochlear soft tissue

    NASA Astrophysics Data System (ADS)

    Shintani Smith, Stephanie; Hwang, Margaret; Rau, Christoph; Fishman, Andrew J.; Lee, Wah-Keat; Richter, Claus-Peter

    2011-03-01

    A noninvasive technique to image soft tissue could expedite diagnosis and disease management in the auditory system. We propose inline phase contrast imaging with hard X-rays as a novel method that overcomes the limitations of conventional absorption radiography for imaging soft tissue. In this study, phase contrast imaging of mouse cochleae was performed at the Argonne National Laboratory Advanced Photon Source. The phase contrast tomographic reconstructions show soft tissue structures of the cochlea, including the inner pillar cells, the inner spiral sulcus, the tectorial membrane, the basilar membrane, and the Reissner's membrane. The results suggest that phase contrast X-ray imaging and tomographic techniques hold promise to noninvasively image cochlear structures at an unprecedented cellular level.

  8. Fast high-contrast imaging of animal development with scanned light sheet-based structured illumination microscopy

    PubMed Central

    Keller, Philipp J.; Schmidt, Annette D.; Santella, Anthony; Khairy, Khaled; Bao, Zhirong; Wittbrodt, Joachim; Stelzer, Ernst H.K.

    2015-01-01

    Recording light microscopic images of large, non-transparent specimens, such as developing multi-cellular organisms, is complicated by decreased contrast due to light scattering. Early zebrafish development can be captured by standard light sheet microscopy; however, new imaging strategies are required to obtain high-quality data of late development or of less transparent organisms. We combined Digital Scanned Laser Light Sheet Fluorescence Microscopy (DSLM) with incoherent structured illumination microscopy and created structured illumination patterns with continuously adjustable frequencies (DSLM-SI). Our method discriminates the specimen-related scattered background from signal fluorescence, thereby removing out-of-focus light and optimizing the contrast of in-focus structures. DSLM-SI provides rapid control of the illumination pattern, exceptional imaging quality and high imaging speeds. We performed long-term imaging of zebrafish development for 58 hours and fast multiple-view imaging of early Drosophila development. We reconstructed cell positions over time from the Drosophila DSLM-SI data and created a Fly Digital Embryo. PMID:20601950

  9. Contrast optimization in broadband polarimetric imaging

    NASA Astrophysics Data System (ADS)

    Thomas, Lijo; Hu, Haofeng; Boffety, Matthieu; Goudail, François

    2016-05-01

    For the sake of polarimetric accuracy, polarization imaging systems based on liquid crystal modulators often work at one given wavelength due to the strong chromatic properties of the liquid crystal retarders. This often requires the use of narrowband filters which reduces the amount of light in the system and thus the signal-to-noise ratio. For applications where the main parameter of interest is the target/background discriminability rather than polarimetric accuracy, spectral filtering may not be the best option. In this work, we investigate the impact of broadening the spectrum of the light entering the system on the discriminability performance of passive and active polarimetric systems. Through simulations, we show that broadening the bandwidth of the illumination can increase the contrast between two regions, as the increase of light flux compensates for the loss of polarimetric precision. Moreover, we show that taking into account the chromatic characteristics of the components of the imaging system can further enhance the contrast. We validate these findings through experiments in passive and active configurations, and demonstrate that the illumination bandwidth can be seen as an additional parameter to optimize polarimetric imaging set-ups.

  10. Enhancement of multispectral thermal infrared images - Decorrelation contrast stretching

    NASA Technical Reports Server (NTRS)

    Gillespie, Alan R.

    1992-01-01

    Decorrelation contrast stretching is an effective method for displaying information from multispectral thermal infrared (TIR) images. The technique involves transformation of the data to principle components ('decorrelation'), independent contrast 'stretching' of data from the new 'decorrelated' image bands, and retransformation of the stretched data back to the approximate original axes, based on the inverse of the principle component rotation. The enhancement is robust in that colors of the same scene components are similar in enhanced images of similar scenes, or the same scene imaged at different times. Decorrelation contrast stretching is reviewed in the context of other enhancements applied to TIR images.

  11. Evaluation of microbubble contrast agents for dynamic imaging with x-ray phase contrast.

    PubMed

    Millard, T P; Endrizzi, M; Everdell, N; Rigon, L; Arfelli, F; Menk, R H; Stride, E; Olivo, A

    2015-07-29

    X-rays are commonly used as a means to image the inside of objects opaque to visible light, as their short wavelength allows penetration through matter and the formation of high spatial resolution images. This physical effect has found particular importance in medicine where x-ray based imaging is routinely used as a diagnostic tool. Increasingly, however, imaging modalities that provide functional as well as morphological information are required. In this study the potential to use x-ray phase based imaging as a functional modality through the use of microbubbles that can be targeted to specific biological processes is explored. We show that the concentration of a microbubble suspension can be monitored quantitatively whilst in flow using x-ray phase contrast imaging. This could provide the basis for a dynamic imaging technique that combines the tissue penetration, spatial resolution, and high contrast of x-ray phase based imaging with the functional information offered by targeted imaging modalities.

  12. Preliminary comparison of grating-based and in-line phase contrast X-ray imaging with synchrotron radiation for mouse kidney at TOMCAT

    NASA Astrophysics Data System (ADS)

    Sun, J.; Liu, P.; Irvine, S.; Pinzer, B.; Stampanoni, M.; Xu, L. X.

    2013-06-01

    Phase contrast imaging has been demonstrated to be advantageous in revealing detailed structures inside biological specimens without contrast agents. Grating-based differential phase contrast (DPC) and in-line phase contrast (ILPC) X-ray imaging are the two modalities frequently used at the beamline of TOmographic Microscopy and Coherent rAdiology experimenTs (TOMCAT) at the Swiss Light Source (SLS). In this paper, we preliminarily compared the abilities of two types of phase contrast imaging in distinguishing micro structures in mouse kidneys. The 3D reconstructions showed that the microstructures in kidney, such as micro vessels and renal tubules, were displayed clearly with both imaging modalities. The two techniques may be viewed as complementary. For larger features with very small density variations DPC is the desirable method. In cases where dose and time limits may prohibit the multiple steps required for DPC, and when the focus is on finer features, the ILPC method may be considered as a more viable alternative. Moreover, high resolution ILPC images are comparable with histological results.

  13. Analyzing indirect secondary electron contrast of unstained bacteriophage T4 based on SEM images and Monte Carlo simulations

    SciTech Connect

    Ogura, Toshihiko

    2009-03-06

    The indirect secondary electron contrast (ISEC) condition of the scanning electron microscopy (SEM) produces high contrast detection with minimal damage of unstained biological samples mounted under a thin carbon film. The high contrast image is created by a secondary electron signal produced under the carbon film by a low acceleration voltage. Here, we show that ISEC condition is clearly able to detect unstained bacteriophage T4 under a thin carbon film (10-15 nm) by using high-resolution field emission (FE) SEM. The results show that FE-SEM provides higher resolution than thermionic emission SEM. Furthermore, we investigated the scattered electron area within the carbon film under ISEC conditions using Monte Carlo simulation. The simulations indicated that the image resolution difference is related to the scattering width in the carbon film and the electron beam spot size. Using ISEC conditions on unstained virus samples would produce low electronic damage, because the electron beam does not directly irradiate the sample. In addition to the routine analysis, this method can be utilized for structural analysis of various biological samples like viruses, bacteria, and protein complexes.

  14. In vivo physiological saline-infused hepatic vessel imaging using a two-crystal-interferometer-based phase-contrast X-ray technique.

    PubMed

    Takeda, Tohoru; Yoneyama, Akio; Wu, Jin; Momose, Atsushi; Hyodo, Kazuyuki

    2012-03-01

    Using a two-crystal-interferometer-based phase-contrast X-ray imaging system, the portal vein, capillary vessel area and hepatic vein of live rats were revealed sequentially by injecting physiological saline via the portal vein. Vessels greater than 0.06 mm in diameter were clearly shown with low levels of X-rays (552 µGy). This suggests that in vivo vessel imaging of small animals can be performed as conventional angiography without the side effects of the presently used iodine contrast agents.

  15. Imaging of Hydrogel Microsphere Structure and Foreign Body Response Based on Endogenous X-Ray Phase Contrast

    DOE PAGES

    Appel, Alyssa A.; Ibarra, Veronica; Somo, Sami I.; ...

    2016-10-31

    Transplantation of functional islets encapsulated in stable biomaterials has the potential to cure Type I diabetes. However, the success of these materials requires the ability to understand their stability in vivo. Imaging techniques that enable monitoring of biomaterial performance are critical to further development in the field. In this study, we demonstrate for the first time that X-ray phase contrast (XPC) imaging techniques enable 3D imaging and evaluation of islet volume, alginate hydrogel structure and local soft tissue response. Islets were encapsulated in alginate systems prepared in methods used in clinical trials and implanted in a rodent omentum pouch modelmore » as a treatment for type I diabetes. Microbeads were imaged with XPC prior to implantation and following implantation into an omentum pouch. Islets could be identified within alginate beads and the islet volume quantified. Omental adipose tissue could be distinguished from inflammatory regions resulting from implanted beads. Individual beads and the local encapsulation response were visualized and quantifiable. Measurements were in agreement with histology. The 3D structure of the microbeads could be characterized with XPC and failed beads could also be identified. These results point to the substantial potential of XPC as a tool for imaging biomaterials in small animal models.« less

  16. Imaging of Hydrogel Microsphere Structure and Foreign Body Response Based on Endogenous X-Ray Phase Contrast

    SciTech Connect

    Appel, Alyssa A.; Ibarra, Veronica; Somo, Sami I.; Larson, Jeffery C.; Garson, Alfred B.; Guan, Huifeng; McQuilling, John Patrick; Zhong, Zhong; Anastasio, Mark A.; Opara, Emmanuel C.; Brey, Eric M.

    2016-10-31

    Transplantation of functional islets encapsulated in stable biomaterials has the potential to cure Type I diabetes. However, the success of these materials requires the ability to understand their stability in vivo. Imaging techniques that enable monitoring of biomaterial performance are critical to further development in the field. In this study, we demonstrate for the first time that X-ray phase contrast (XPC) imaging techniques enable 3D imaging and evaluation of islet volume, alginate hydrogel structure and local soft tissue response. Islets were encapsulated in alginate systems prepared in methods used in clinical trials and implanted in a rodent omentum pouch model as a treatment for type I diabetes. Microbeads were imaged with XPC prior to implantation and following implantation into an omentum pouch. Islets could be identified within alginate beads and the islet volume quantified. Omental adipose tissue could be distinguished from inflammatory regions resulting from implanted beads. Individual beads and the local encapsulation response were visualized and quantifiable. Measurements were in agreement with histology. The 3D structure of the microbeads could be characterized with XPC and failed beads could also be identified. These results point to the substantial potential of XPC as a tool for imaging biomaterials in small animal models.

  17. Multiparametric MR imaging of prostate cancer foci: assessing the detectability and localizability of Gleason 7 peripheral zone cancers based on image contrasts

    NASA Astrophysics Data System (ADS)

    Gibson, Eli; Gaed, Mena; Hrinivich, Thomas; Gómez, José A.; Moussa, Madeleine; Romagnoli, Cesare; Mandel, Jonathan; Bastian-Jordan, Matthew; Cool, Derek W.; Ghoul, Suha; Pautler, Stephen E.; Chin, Joseph L.; Crukley, Cathie; Bauman, Glenn S.; Fenster, Aaron; Ward, Aaron D.

    2014-03-01

    Purpose: Multiparametric magnetic resonance imaging (MPMRI) supports detection and staging of prostate cancer, but the image characteristics needed for tumor boundary delineation to support focal therapy have not been widely investigated. We quantified the detectability (image contrast between tumor and non-cancerous contralateral tissue) and the localizability (image contrast between tumor and non-cancerous neighboring tissue) of Gleason score 7 (GS7) peripheral zone (PZ) tumors on MPMRI using tumor contours mapped from histology using accurate 2D-3D registration. Methods: MPMRI [comprising T2-weighted (T2W), dynamic-contrast-enhanced (DCE), apparent diffusion coefficient (ADC) and contrast transfer coefficient images] and post-prostatectomy digitized histology images were acquired for 6 subjects. Histology contouring and grading (approved by a genitourinary pathologist) identified 7 GS7 PZ tumors. Contours were mapped to MPMRI images using semi-automated registration algorithms (combined target registration error: 2 mm). For each focus, three measurements of mean +/- standard deviation of image intensity were taken on each image: tumor tissue (mT+/-sT), non-cancerous PZ tissue < 5 mm from the tumor (mN+/-sN), and non-cancerous contralateral PZ tissue (mC+/-sC). Detectability [D, defined as mT-mC normalized by sT and sC added in quadrature] and localizability [L, defined as mT-mN normalized by sT and sN added in quadrature] were quantified for each focus on each image. Results: T2W images showed the strongest detectability, although detectability |D|>=1 was observed on either ADC or DCE images, or both, for all foci. Localizability on all modalities was variable; however, ADC images showed localizability |L|>=1 for 3 foci. Conclusions: Delineation of GS7 PZ tumors on individual MPMRI images faces challenges; however, images may contain complementary information, suggesting a role for fusion of

  18. Fluorescence lifetime contrast in small animal imaging

    NASA Astrophysics Data System (ADS)

    Ramanujan, V. Krishnan; Bandyopadhyay, Abhik; Sun, LuZhe; Herman, Brian A.

    2007-02-01

    Early detection of primary tumors is the key for effective therapeutic intervention and successful patient survival. Small animal models emulating human diseases are powerful tools for our comprehensive understanding of the pathophysiology of tumor formation and metastasis to distant sites. Our long-term goal is to develop a non-invasive, multiphoton-fluorescence lifetime imaging (MP-FLIM) modality that can precisely quantify these steps in animal tumor models at a very early stage. The specific hypothesis is that fluorescence lifetime can be employed as reliable contrast parameter for providing higher detection sensitivity as compared with conventional intensity-based tumor imaging approaches and therefore it is possible to detect smaller tumor volumes (early detection) than those achieved by other prevailing methods. We base this hypothesis on our recent observations that (1) fluorescence lifetime is "intrinsic" to the fluorophore and its measurement is not affected by concentration and/or spectral artifacts as in intensity-based methods, (2) multiphoton excitation can enable increased tissue penetrability and reduced phototoxicity and (3) MP-FLIM approach can discriminate background autofluorescence from the fluorescent proteins in thick tissues thereby achieving a ten-fold increase in signal-to-background ratio over the intensity-based approaches. We present our preliminary data to support this hypothesis in primary tumor detection in nu/nu athymic mouse models.

  19. Microscopic identification of Chinese medicinal materials based on X-ray phase contrast imaging: from qualitative to quantitative

    NASA Astrophysics Data System (ADS)

    Xue, Y.; Liang, Z.; Tan, H.; Ni, L.; Zhao, Z.; Xiao, T.; Xu, H.

    2016-07-01

    Although a variety of methods, ranging from simple morphological examination to physical and chemical analysis, and DNA molecular biology, exist for authenticating Chinese medicinal materials(CMMs), no methods can achieve both the source species identification and quality evaluation of CMMs simultaneously. Furthermore, the methods that are currently available for the identification of CMMs, including both optical and electronic microscopy, usually entail strict requirements for sample preparation or testing environment, such as the slicing of super-thin sections, or processing with specific chemical reagents. These treatments not only damage the CMMs but may also cause some of the original microstructures to be missed. Additionally, they may even yield false results. Owing to the unique penetrating character of X-rays, X-ray phase contrast imaging(XPCI) can be used to realize the inner microstructures of CMMs through nondestructive imaging. With the higher flux and luminance of the third generation of synchrotron radiation facility, XPCI can provides clearer and finer microstructures of CMMs, which are mainly composed of C, H, O, and N elements, with better spatial and density resolutions. For more than ten years, the X-ray imaging group at the Shanghai Institute of Applied Physics has investigated the microstructures of CMMs by XPCI and they have established and developed a quantitative X-ray phase contrast micro-CT for investigating the characteristic microstructures of CMMs. During this period, a variety of typical CMMs have been investigated, from two-dimensional (2D) radiography to three-dimensional (3D) micro-CT, from qualitative to quantitative. Taken together, these results verify that quantitative X-ray phase contrast micro-CT is a practical tool for the microscopic investigation of CMMs. Additionally, further efforts are being made to find the relationship between the microstructures' quantitative factors and active chemical components. At present

  20. High-contrast fluorescence imaging based on the polarization dependence of the fluorescence enhancement using an optical interference mirror slide.

    PubMed

    Yasuda, Mitsuru; Akimoto, Takuo

    2015-01-01

    High-contrast fluorescence imaging using an optical interference mirror (OIM) slide that enhances the fluorescence from a fluorophore located on top of the OIM surface is reported. To enhance the fluorescence and reduce the background light of the OIM, transverse-electric-polarized excitation light was used as incident light, and the transverse-magnetic-polarized fluorescence signal was detected. As a result, an approximate 100-fold improvement in the signal-to-noise ratio was achieved through a 13-fold enhancement of the fluorescence signal and an 8-fold reduction of the background light.

  1. Advances in Magnetic Resonance Imaging Contrast Agents for Biomarker Detection

    NASA Astrophysics Data System (ADS)

    Sinharay, Sanhita; Pagel, Mark D.

    2016-06-01

    Recent advances in magnetic resonance imaging (MRI) contrast agents have provided new capabilities for biomarker detection through molecular imaging. MRI contrast agents based on the T2 exchange mechanism have more recently expanded the armamentarium of agents for molecular imaging. Compared with T1 and T2* agents, T2 exchange agents have a slower chemical exchange rate, which improves the ability to design these MRI contrast agents with greater specificity for detecting the intended biomarker. MRI contrast agents that are detected through chemical exchange saturation transfer (CEST) have even slower chemical exchange rates. Another emerging class of MRI contrast agents uses hyperpolarized 13C to detect the agent with outstanding sensitivity. These hyperpolarized 13C agents can be used to track metabolism and monitor characteristics of the tissue microenvironment. Together, these various MRI contrast agents provide excellent opportunities to develop molecular imaging for biomarker detection.

  2. Advances in Magnetic Resonance Imaging Contrast Agents for Biomarker Detection

    PubMed Central

    Sinharay, Sanhita; Pagel, Mark D.

    2016-01-01

    Recent advances in magnetic resonance imaging (MRI) contrast agents have provided new capabilities for biomarker detection through molecular imaging. MRI contrast agents based on the T2 exchange mechanism have more recently expanded the armamentarium of agents for molecular imaging. Compared with T1 and T2* agents, T2 exchange agents have a slower chemical exchange rate, which improves the ability to design these MRI contrast agents with greater specificity for detecting the intended biomarker. MRI contrast agents that are detected through chemical exchange saturation transfer (CEST) have even slower chemical exchange rates. Another emerging class of MRI contrast agents uses hyperpolarized 13C to detect the agent with outstanding sensitivity. These hyperpolarized 13C agents can be used to track metabolism and monitor characteristics of the tissue microenvironment. Together, these various MRI contrast agents provide excellent opportunities to develop molecular imaging for biomarker detection. PMID:27049630

  3. Feasibility of 3D harmonic contrast imaging.

    PubMed

    Voormolen, M M; Bouakaz, A; Krenning, B J; Lancée, C T; ten Cate, F J; de Jong, N

    2004-04-01

    Improved endocardial border delineation with the application of contrast agents should allow for less complex and faster tracing algorithms for left ventricular volume analysis. We developed a fast rotating phased array transducer for 3D imaging of the heart with harmonic capabilities making it suitable for contrast imaging. In this study the feasibility of 3D harmonic contrast imaging is evaluated in vitro. A commercially available tissue mimicking flow phantom was used in combination with Sonovue. Backscatter power spectra from a tissue and contrast region of interest were calculated from recorded radio frequency data. The spectra and the extracted contrast to tissue ratio from these spectra were used to optimize the excitation frequency, the pulse length and the receive filter settings of the transducer. Frequencies ranging from 1.66 to 2.35 MHz and pulse lengths of 1.5, 2 and 2.5 cycles were explored. An increase of more than 15 dB in the contrast to tissue ratio was found around the second harmonic compared with the fundamental level at an optimal excitation frequency of 1.74 MHz and a pulse length of 2.5 cycles. Using the optimal settings for 3D harmonic contrast recordings volume measurements of a left ventricular shaped agar phantom were performed. Without contrast the extracted volume data resulted in a volume error of 1.5%, with contrast an accuracy of 3.8% was achieved. The results show the feasibility of accurate volume measurements from 3D harmonic contrast images. Further investigations will include the clinical evaluation of the presented technique for improved assessment of the heart.

  4. Speckle-Based X-Ray Phase-Contrast and Dark-Field Imaging with a Laboratory Source

    NASA Astrophysics Data System (ADS)

    Zanette, I.; Zhou, T.; Burvall, A.; Lundström, U.; Larsson, D. H.; Zdora, M.; Thibault, P.; Pfeiffer, F.; Hertz, H. M.

    2014-06-01

    We report on the observation and application of near-field speckles with a laboratory x-ray source. The detection of speckles is possible thanks to the enhanced brilliance properties of the used liquid-metal-jet source, and opens the way to a range of new applications in laboratory-based coherent x-ray imaging. Here, we use the speckle pattern for multimodal imaging of demonstrator objects. Moreover, we introduce algorithms for phase and dark-field imaging using speckle tracking, and we show that they yield superior results with respect to existing methods.

  5. Radiogenomic analysis of breast cancer: dynamic contrast enhanced - magnetic resonance imaging based features are associated with molecular subtypes

    NASA Astrophysics Data System (ADS)

    Wang, Shijian; Fan, Ming; Zhang, Juan; Zheng, Bin; Wang, Xiaojia; Li, Lihua

    2016-03-01

    Breast cancer is one of the most common malignant tumor with upgrading incidence in females. The key to decrease the mortality is early diagnosis and reasonable treatment. Molecular classification could provide better insights into patient-directed therapy and prognosis prediction of breast cancer. It is known that different molecular subtypes have different characteristics in magnetic resonance imaging (MRI) examination. Therefore, we assumed that imaging features can reflect molecular information in breast cancer. In this study, we investigated associations between dynamic contrasts enhanced MRI (DCE-MRI) features and molecular subtypes in breast cancer. Sixty patients with breast cancer were enrolled and the MR images were pre-processed for noise reduction, registration and segmentation. Sixty-five dimensional imaging features including statistical characteristics, morphology, texture and dynamic enhancement in breast lesion and background regions were semiautomatically extracted. The associations between imaging features and molecular subtypes were assessed by using statistical analyses, including univariate logistic regression and multivariate logistic regression. The results of multivariate regression showed that imaging features are significantly associated with molecular subtypes of Luminal A (p=0.00473), HER2-enriched (p=0.00277) and Basal like (p=0.0117), respectively. The results indicated that three molecular subtypes are correlated with DCE-MRI features in breast cancer. Specifically, patients with a higher level of compactness or lower level of skewness in breast lesion are more likely to be Luminal A subtype. Besides, the higher value of the dynamic enhancement at T1 time in normal side reflect higher possibility of HER2-enriched subtype in breast cancer.

  6. Contrast sensitivity function and image discrimination.

    PubMed

    Peli, E

    2001-02-01

    A previous study tested the validity of simulations of the appearance of a natural image (from different observation distances) generated by using a visual model and contrast sensitivity functions of the individual observers [J. Opt. Soc. Am. A 13, 1131 (1996)]. Deleting image spatial-frequency components that should be undetectable made the simulations indistinguishable from the original images at distances larger than the simulated distance. The simulated observation distance accurately predicted the distance at which the simulated image could be discriminated from the original image. Owing to the 1/f characteristic of natural images' spatial spectra, the individual contrast sensitivity functions (CSF's) used in the simulations of the previous study were actually tested only over a narrow range of retinal spatial frequencies. To test the CSF's over a wide range of frequencies, the same simulations and testing procedure were applied to five contrast versions of the images (10-300%). This provides a stronger test of the model, of the simulations, and specifically of the CSF's used. The relevant CSF for a discrimination task was found to be obtained by using 1-octave Gabor stimuli measured in a contrast detection task. The relevant CSF data had to be measured over a range of observation distances, owing to limitations of the displays.

  7. Quantification of signal detection performance degradation induced by phase-retrieval in propagation-based x-ray phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Chou, Cheng-Ying; Anastasio, Mark A.

    2016-04-01

    In propagation-based X-ray phase-contrast (PB XPC) imaging, the measured image contains a mixture of absorption- and phase-contrast. To obtain separate images of the projected absorption and phase (i.e., refractive) properties of a sample, phase retrieval methods can be employed. It has been suggested that phase-retrieval can always improve image quality in PB XPC imaging. However, when objective (task-based) measures of image quality are employed, this is not necessarily true and phase retrieval can be detrimental. In this work, signal detection theory is utilized to quantify the performance of a Hotelling observer (HO) for detecting a known signal in a known background. Two cases are considered. In the first case, the HO acts directly on the measured intensity data. In the second case, the HO acts on either the retrieved phase or absorption image. We demonstrate that the performance of the HO is superior when acting on the measured intensity data. The loss of task-specific information induced by phase-retrieval is quantified by computing the efficiency of the HO as the ratio of the test statistic signal-to-noise ratio (SNR) for the two cases. The effect of the system geometry on this efficiency is systematically investigated. Our findings confirm that phase-retrieval can impair signal detection performance in XPC imaging.

  8. Contrast optimization in broadband passive polarimetric imaging.

    PubMed

    Boffety, Matthieu; Hu, Haofeng; Goudail, François

    2014-12-01

    Polarimetric imaging is often performed using light with a narrow spectrum for the sake of polarization measurement accuracy. However, due to the use of narrowband filters, this reduces the amount of light entering the system and thus the signal-to-noise ratio. This may not be the best choice for target detection applications, where a high target contrast is required rather than polarimetric accuracy. We address contrast optimization for broadband passive polarimetric imaging. We show through simulation and experiments that polarimetric contrast can be significantly increased by broadening the spectrum of analyzed light. In addition, we show that the contrast can be optimized by taking into account the spectral dependence of the scene and of the polarization analysis devices.

  9. Automated segmentation of mammary gland regions in non-contrast torso CT images based on probabilistic atlas

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Kan, M.; Hara, T.; Fujita, H.; Sugisaki, K.; Yokoyama, R.; Lee, G.; Hoshi, H.

    2007-03-01

    The identification of mammary gland regions is a necessary processing step during the anatomical structure recognition of human body and can be expected to provide the useful information for breast tumor diagnosis. This paper proposes a fully-automated scheme for segmenting the mammary gland regions in non-contrast torso CT images. This scheme calculates the probability for each voxel belonging to the mammary gland or other regions (for example pectoralis major muscles) in CT images and decides the mammary gland regions automatically. The probability is estimated from the location of the mammary gland and pectoralis major muscles in CT images. The location (named as a probabilistic atlas) is investigated from the pre-segmentation results in a number of different CT scans and the CT number distribution is approximated using a Gaussian function. We applied this scheme to 66 patient cases (female, age: 40-80) and evaluated the accuracy by using the coincidence rate between the segmented result and gold standard that is generated manually by a radiologist for each CT case. The mean value of the coincidence rate was 0.82 with the standard deviation of 0.09 for 66 CT cases.

  10. Contrast dispersion imaging for cancer localization.

    PubMed

    Mischi, Massimo; Wijkstra, Hessel

    2014-01-01

    Cancer growth is associated with angiogenic processes in many types of cancer. Several imaging strategies have therefore been developed that target angiogenesis as a marker for cancer localization. To this end, intravascular and extravascular tissue perfusion is typically assessed by dynamic contrast enhanced (DCE) ultrasound (US) and MRI. All the proposed strategies, however, overlook important changes in the microvascular architecture that result from angiogenic processes. To overcome these limitations, we have recently introduced a new imaging strategy that analyzes the intravascular dispersion kinetics of contrast agents spreading through the microvasculature. Contrast dispersion is mainly determined by microvascular multi-path trajectories, reflecting the underlying microvascular architecture. This paper reviews the results obtained for prostate cancer localization by US and MRI dispersion imaging, also presenting the latest new developments and future perspectives.

  11. NASA High Contrast Imaging for Exoplanets

    NASA Technical Reports Server (NTRS)

    Lyon, Richard G.

    2008-01-01

    Described is NASA's ongoing program for the detection and characterization of exosolar planets via high-contrast imaging. Some of the more promising proposed techniques under assessment may enable detection of life outside our solar system. In visible light terrestrial planets are approximately 10(exp -10) dimmer than the parent star. Issues such as diffraction, scatter, wavefront, amplitude and polarization all contribute to a reduction in contrast. An overview of the techniques will be discussed.

  12. High-contrast imaging with METIS

    NASA Astrophysics Data System (ADS)

    Kenworthy, Matthew A.; Absil, Olivier; Agócs, Tibor; Pantin, Eric; Quanz, Sascha; Stuik, Remko; Snik, Frans; Brandl, Bernhard

    2016-08-01

    The Mid-infrared E-ELT Imager and Spectrograph (METIS) for the European Extremely Large Telescope (E-ELT) consists of diffraction-limited imagers that cover 3 to 14 microns with medium resolution (R 5000) long slit spectroscopy, and an integral field spectrograph for high spectral resolution spectroscopy (R 100,000) over the L and M bands. One of the science cases that METIS addresses is the characterization of faint circumstellar material and exoplanet companions through imaging and spectroscopy. We present our approach for high contrast imaging with METIS, covering diffraction suppression with coronagraphs, the removal of slowly changing optical aberrations with focal plane wavefront sensing, interferometric imaging with sparse aperture masks, and observing strategies for both the imagers and IFU image slicers.

  13. Factors influencing real time internal structural visualization and dynamic process monitoring in plants using synchrotron-based phase contrast X-ray imaging

    PubMed Central

    Karunakaran, Chithra; Lahlali, Rachid; Zhu, Ning; Webb, Adam M.; Schmidt, Marina; Fransishyn, Kyle; Belev, George; Wysokinski, Tomasz; Olson, Jeremy; Cooper, David M. L.; Hallin, Emil

    2015-01-01

    Minimally invasive investigation of plant parts (root, stem, leaves, and flower) has good potential to elucidate the dynamics of plant growth, morphology, physiology, and root-rhizosphere interactions. Laboratory based absorption X-ray imaging and computed tomography (CT) systems are extensively used for in situ feasibility studies of plants grown in natural and artificial soil. These techniques have challenges such as low contrast between soil pore space and roots, long X-ray imaging time, and low spatial resolution. In this study, the use of synchrotron (SR) based phase contrast X-ray imaging (PCI) has been demonstrated as a minimally invasive technique for imaging plants. Above ground plant parts and roots of 10 day old canola and wheat seedlings grown in sandy clay loam soil were successfully scanned and reconstructed. Results confirmed that SR-PCI can deliver good quality images to study dynamic and real time processes such as cavitation and water-refilling in plants. The advantages of SR-PCI, effect of X-ray energy, and effective pixel size to study plant samples have been demonstrated. The use of contrast agents to monitor physiological processes in plants was also investigated and discussed. PMID:26183486

  14. Factors influencing real time internal structural visualization and dynamic process monitoring in plants using synchrotron-based phase contrast X-ray imaging.

    PubMed

    Karunakaran, Chithra; Lahlali, Rachid; Zhu, Ning; Webb, Adam M; Schmidt, Marina; Fransishyn, Kyle; Belev, George; Wysokinski, Tomasz; Olson, Jeremy; Cooper, David M L; Hallin, Emil

    2015-07-17

    Minimally invasive investigation of plant parts (root, stem, leaves, and flower) has good potential to elucidate the dynamics of plant growth, morphology, physiology, and root-rhizosphere interactions. Laboratory based absorption X-ray imaging and computed tomography (CT) systems are extensively used for in situ feasibility studies of plants grown in natural and artificial soil. These techniques have challenges such as low contrast between soil pore space and roots, long X-ray imaging time, and low spatial resolution. In this study, the use of synchrotron (SR) based phase contrast X-ray imaging (PCI) has been demonstrated as a minimally invasive technique for imaging plants. Above ground plant parts and roots of 10 day old canola and wheat seedlings grown in sandy clay loam soil were successfully scanned and reconstructed. Results confirmed that SR-PCI can deliver good quality images to study dynamic and real time processes such as cavitation and water-refilling in plants. The advantages of SR-PCI, effect of X-ray energy, and effective pixel size to study plant samples have been demonstrated. The use of contrast agents to monitor physiological processes in plants was also investigated and discussed.

  15. Factors influencing real time internal structural visualization and dynamic process monitoring in plants using synchrotron-based phase contrast X-ray imaging

    NASA Astrophysics Data System (ADS)

    Karunakaran, Chithra; Lahlali, Rachid; Zhu, Ning; Webb, Adam M.; Schmidt, Marina; Fransishyn, Kyle; Belev, George; Wysokinski, Tomasz; Olson, Jeremy; Cooper, David M. L.; Hallin, Emil

    2015-07-01

    Minimally invasive investigation of plant parts (root, stem, leaves, and flower) has good potential to elucidate the dynamics of plant growth, morphology, physiology, and root-rhizosphere interactions. Laboratory based absorption X-ray imaging and computed tomography (CT) systems are extensively used for in situ feasibility studies of plants grown in natural and artificial soil. These techniques have challenges such as low contrast between soil pore space and roots, long X-ray imaging time, and low spatial resolution. In this study, the use of synchrotron (SR) based phase contrast X-ray imaging (PCI) has been demonstrated as a minimally invasive technique for imaging plants. Above ground plant parts and roots of 10 day old canola and wheat seedlings grown in sandy clay loam soil were successfully scanned and reconstructed. Results confirmed that SR-PCI can deliver good quality images to study dynamic and real time processes such as cavitation and water-refilling in plants. The advantages of SR-PCI, effect of X-ray energy, and effective pixel size to study plant samples have been demonstrated. The use of contrast agents to monitor physiological processes in plants was also investigated and discussed.

  16. GADOLINIUM(Gd)-BASED and Ion Oxide Nanoparticle Contrast Agents for Pre-Clinical and Clinical Magnetic Resonance Imaging (mri) Research

    NASA Astrophysics Data System (ADS)

    Ng, Thian C.

    2012-06-01

    It is known that one strength of MRI is its excellent soft tissue discrimination. It naturally provides sufficient contrast between the structural differences of normal and pathological tissues, their spatial extent and progression. However, to further extend its applications and enhance even more contrast for clinical studies, various Gadolinium (Gd)-based contrast agents have been developed for different organs (brain strokes, cancer, cardio-MRI, etc). These Gd-based contrast agents are paramagnetic compounds that have strong T1-effect for enhancing the contrast between tissue types. Gd-contrast can also enhance magnetic resonance angiography (CE-MRA) for studying stenosis and for measuring perfusion, vascular susceptibility, interstitial space, etc. Another class of contrast agents makes use of ferrite iron oxide nanoparticles (including Superparamagnetic Ion Oxide (SPIO) and Ultrasmall Superparamagnetic Iron Oxide (USPIO)). These nanoparticles have superior magnetic susceptibility effect and produce a drop in signal, namely in T2*-weighted images, useful for the determination of lymph nodes metastases, angiogenesis and arteriosclerosis plaques.

  17. High Resolution X-Ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2007-06-01

    Contrast and resolution in imaging with microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray ...water jet of carbon suspension and imaged using a microfocus x - ray source coupled in-line with a synchronously gated intensified optically coupled...

  18. Translation of Atherosclerotic Plaque Phase-Contrast CT Imaging from Synchrotron Radiation to a Conventional Lab-Based X-Ray Source

    PubMed Central

    Saam, Tobias; Herzen, Julia; Hetterich, Holger; Fill, Sandra; Willner, Marian; Stockmar, Marco; Achterhold, Klaus; Zanette, Irene; Weitkamp, Timm; Schüller, Ulrich; Auweter, Sigrid; Adam-Neumair, Silvia; Nikolaou, Konstantin; Reiser, Maximilian F.; Pfeiffer, Franz; Bamberg, Fabian

    2013-01-01

    Objectives Phase-contrast imaging is a novel X-ray based technique that provides enhanced soft tissue contrast. The aim of this study was to evaluate the feasibility of visualizing human carotid arteries by grating-based phase-contrast tomography (PC-CT) at two different experimental set-ups: (i) applying synchrotron radiation and (ii) using a conventional X-ray tube. Materials and Methods Five ex-vivo carotid artery specimens were examined with PC-CT either at the European Synchrotron Radiation Facility using a monochromatic X-ray beam (2 specimens; 23 keV; pixel size 5.4 µm), or at a laboratory set-up on a conventional X-ray tube (3 specimens; 35-40 kVp; 70 mA; pixel size 100 µm). Tomographic images were reconstructed and compared to histopathology. Two independent readers determined vessel dimensions and one reader determined signal-to-noise ratios (SNR) between PC-CT and absorption images. Results In total, 51 sections were included in the analysis. Images from both set-ups provided sufficient contrast to differentiate individual vessel layers. All PCI-based measurements strongly predicted but significantly overestimated lumen, intima and vessel wall area for both the synchrotron and the laboratory-based measurements as compared with histology (all p<0.001 with slope >0.53 per mm2, 95%-CI: 0.35 to 0.70). Although synchrotron-based images were characterized by higher SNRs than laboratory-based images; both PC-CT set-ups had superior SNRs compared to corresponding conventional absorption-based images (p<0.001). Inter-reader reproducibility was excellent (ICCs >0.98 and >0.84 for synchrotron and for laboratory-based measurements; respectively). Conclusion Experimental PC-CT of carotid specimens is feasible with both synchrotron and conventional X-ray sources, producing high-resolution images suitable for vessel characterization and atherosclerosis research. PMID:24039969

  19. In vivo long-term magnetic resonance imaging activity of ferritin-based magnetic nanoparticles versus a standard contrast agent.

    PubMed

    Valero, Elsa; Fiorini, Silvia; Tambalo, Stefano; Busquier, Heriberto; Callejas-Fernández, José; Marzola, Pasquina; Gálvez, Natividad; Domínguez-Vera, José M

    2014-07-10

    New long-circulating maghemite nanoparticles of 4 and 6 nm, coated with an apoferritin protein capsid, exhibit useful properties to act as magnetic resonance imaging (MRI) contrast agents. A full in vivo study of the so-called apomaghemites reveals that their long-term MRI properties are better than those of a standard superparamagnetic iron oxide (SPIO) widely used in biomedical applications. The biodistribution of apomaghemites and standard SPIO was investigated by MRI in mice at two different concentrations, 6 and 2.5 mg of Fe·kg(-1), over 60 days. Significant differences are found at low dose (2.5 mg of Fe·kg(-1)). Thus, whereas apomaghemites are active for MR bioimaging of liver for 45 days, standard SPIO is not effective beyond 7 days. On the basis of our data, we may concluded that apomaghemites can act as new long-term MRI liver contrast agents, allowing first the diagnosis of a liver pathology and then monitoring after treatment without the need for a second injection.

  20. Local adaptive contrast enhancement for color images

    NASA Astrophysics Data System (ADS)

    Dijk, Judith; den Hollander, Richard J. M.; Schavemaker, John G. M.; Schutte, Klamer

    2007-04-01

    A camera or display usually has a smaller dynamic range than the human eye. For this reason, objects that can be detected by the naked eye may not be visible in recorded images. Lighting is here an important factor; improper local lighting impairs visibility of details or even entire objects. When a human is observing a scene with different kinds of lighting, such as shadows, he will need to see details in both the dark and light parts of the scene. For grey value images such as IR imagery, algorithms have been developed in which the local contrast of the image is enhanced using local adaptive techniques. In this paper, we present how such algorithms can be adapted so that details in color images are enhanced while color information is retained. We propose to apply the contrast enhancement on color images by applying a grey value contrast enhancement algorithm to the luminance channel of the color signal. The color coordinates of the signal will remain the same. Care is taken that the saturation change is not too high. Gamut mapping is performed so that the output can be displayed on a monitor. The proposed technique can for instance be used by operators monitoring movements of people in order to detect suspicious behavior. To do this effectively, specific individuals should both be easy to recognize and track. This requires optimal local contrast, and is sometimes much helped by color when tracking a person with colored clothes. In such applications, enhanced local contrast in color images leads to more effective monitoring.

  1. Monitoring stem cells in phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Lam, K. P.; Dempsey, K. P.; Collins, D. J.; Richardson, J. B.

    2016-04-01

    Understanding the mechanisms behind the proliferation of Mesenchymal Stem cells (MSCs) can offer a greater insight into the behaviour of these cells throughout their life cycles. Traditional methods of determining the rate of MSC differentiation rely on population based studies over an extended time period. However, such methods can be inadequate as they are unable to track cells as they interact; for example, in autologous cell therapies for osteoarthritis, the development of biological assays that could predict in vivo functional activity and biological action are particularly challenging. Here further research is required to determine non-histochemical biomarkers which provide correlations between cell survival and predictive functional outcome. This paper proposes using a (previously developed) advanced texture-based analysis algorithm to facilitate in vitro cells tracking using time-lapsed microscopy. The technique was adopted to monitor stem cells in the context of unlabelled, phase contrast imaging, with the goal of examining the cell to cell interactions in both monoculture and co-culture systems. The results obtained are analysed using established exploratory procedures developed for time series data and compared with the typical fluorescent-based approach of cell labelling. A review of the progress and the lessons learned are also presented.

  2. Phased Contrast X-Ray Imaging

    ScienceCinema

    Erin Miller

    2016-07-12

    The Pacific Northwest National Laboratory is developing a range of technologies to broaden the field of explosives detection. Phased contrast X-ray imaging, which uses silicon gratings to detect distortions in the X-ray wave front, may be applicable to mail or luggage scanning for explosives; it can also be used in detecting other contraband, small-parts inspection, or materials characterization.

  3. Diffusible iodine-based contrast-enhanced computed tomography (diceCT): an emerging tool for rapid, high-resolution, 3-D imaging of metazoan soft tissues.

    PubMed

    Gignac, Paul M; Kley, Nathan J; Clarke, Julia A; Colbert, Matthew W; Morhardt, Ashley C; Cerio, Donald; Cost, Ian N; Cox, Philip G; Daza, Juan D; Early, Catherine M; Echols, M Scott; Henkelman, R Mark; Herdina, A Nele; Holliday, Casey M; Li, Zhiheng; Mahlow, Kristin; Merchant, Samer; Müller, Johannes; Orsbon, Courtney P; Paluh, Daniel J; Thies, Monte L; Tsai, Henry P; Witmer, Lawrence M

    2016-06-01

    Morphologists have historically had to rely on destructive procedures to visualize the three-dimensional (3-D) anatomy of animals. More recently, however, non-destructive techniques have come to the forefront. These include X-ray computed tomography (CT), which has been used most commonly to examine the mineralized, hard-tissue anatomy of living and fossil metazoans. One relatively new and potentially transformative aspect of current CT-based research is the use of chemical agents to render visible, and differentiate between, soft-tissue structures in X-ray images. Specifically, iodine has emerged as one of the most widely used of these contrast agents among animal morphologists due to its ease of handling, cost effectiveness, and differential affinities for major types of soft tissues. The rapid adoption of iodine-based contrast agents has resulted in a proliferation of distinct specimen preparations and scanning parameter choices, as well as an increasing variety of imaging hardware and software preferences. Here we provide a critical review of the recent contributions to iodine-based, contrast-enhanced CT research to enable researchers just beginning to employ contrast enhancement to make sense of this complex new landscape of methodologies. We provide a detailed summary of recent case studies, assess factors that govern success at each step of the specimen storage, preparation, and imaging processes, and make recommendations for standardizing both techniques and reporting practices. Finally, we discuss potential cutting-edge applications of diffusible iodine-based contrast-enhanced computed tomography (diceCT) and the issues that must still be overcome to facilitate the broader adoption of diceCT going forward.

  4. Phase contrast portal imaging for image-guided microbeam radiation therapy

    NASA Astrophysics Data System (ADS)

    Umetani, Keiji; Kondoh, Takeshi

    2014-03-01

    High-dose synchrotron microbeam radiation therapy is a unique treatment technique used to destroy tumors without severely affecting circumjacent healthy tissue. We applied a phase contrast technique to portal imaging in preclinical microbeam radiation therapy experiments. Phase contrast portal imaging is expected to enable us to obtain higherresolution X-ray images at therapeutic X-ray energies compared to conventional portal imaging. Frontal view images of a mouse head sample were acquired in propagation-based phase contrast imaging. The phase contrast images depicted edge-enhanced fine structures of the parietal bones surrounding the cerebrum. The phase contrast technique is expected to be effective in bony-landmark-based verification for image-guided radiation therapy.

  5. A Brief Account of Nanoparticle Contrast Agents for Photoacoustic Imaging

    PubMed Central

    Pan, Dipanjan; Kim, Benjamin; Wang, Lihong V.; Lanza, Gregory M

    2014-01-01

    Photoacoustic imaging (PAI) is a hybrid, nonionizing modality offering excellent spatial resolution, deep penetration, and high soft tissue contrast. In PAI, signal is generated based on the absorption of laser-generated optical energy by endogenous tissues or exogenous contrast agents leading to acoustic emissions detected by an ultrasound transducer. Research in this area over the years has shown that PAI has the ability to provide both physiological and molecular imaging, which can be viewed alone or used in a hybrid modality fashion to extend the anatomic and hemodynamic sensitivities of clinical ultrasound. PAI may be performed using inherent contrast afforded by light absorbing molecules such as hemoglobin, myoglobin, and melanin or exogenous small molecule contrast agent such as near infrared dyes and porphyrins. However, this review summarizes the potential of exogenous nanoparticle-based agents for PAI applications including contrast based on gold particles, carbon nanotubes, and encapsulated copper compounds. PMID:23983210

  6. A brief account of nanoparticle contrast agents for photoacoustic imaging.

    PubMed

    Pan, Dipanjan; Kim, Benjamin; Wang, Lihong V; Lanza, Gregory M

    2013-01-01

    Photoacoustic imaging (PAI) is a hybrid, nonionizing modality offering excellent spatial resolution, deep penetration, and high soft tissue contrast. In PAI, signal is generated based on the absorption of laser-generated optical energy by endogenous tissues or exogenous contrast agents leading to acoustic emissions detected by an ultrasound transducer. Research in this area over the years has shown that PAI has the ability to provide both physiological and molecular imaging, which can be viewed alone or used in a hybrid modality fashion to extend the anatomic and hemodynamic sensitivities of clinical ultrasound. PAI may be performed using inherent contrast afforded by light absorbing molecules such as hemoglobin, myoglobin, and melanin or exogenous small molecule contrast agent such as near infrared dyes and porphyrins. However, this review summarizes the potential of exogenous nanoparticle-based agents for PAI applications including contrast based on gold particles, carbon nanotubes, and encapsulated copper compounds.

  7. Wave propagation simulation based on the Fourier diffraction integral for X-ray refraction contrast imaging-computed tomography

    NASA Astrophysics Data System (ADS)

    Chang, Won-Seok; Kim, Jong-Ki; Cho, Jin-Ho; Lim, Jae-Hong

    2016-09-01

    With the advent of coherent X-ray sources, X-ray refraction has begun to be utilized for X-ray imaging of unprecedented sensitivity. The aim of this study was to develop a wave propagation simulator that provides a map of X-ray refraction after passing through an object. We applied the Fresnel diffraction integral for calculating the propagated wave and then obtained the refraction map by differentiating the phase in the refraction-analyzing direction. The simulation was validated by comparing the computed tomography (CT) reconstruction of a virtual phantom with its map of refractive index: the deviations were below 0.7% for soft tissues under our test condition. The simulator can be used for testing and developing highly-sensitive X-ray imaging techniques based on X-ray refraction analysis prior to experimentation.

  8. Validity of computational hemodynamics in human arteries based on 3D time-of-flight MR angiography and 2D electrocardiogram gated phase contrast images

    NASA Astrophysics Data System (ADS)

    Yu, Huidan (Whitney); Chen, Xi; Chen, Rou; Wang, Zhiqiang; Lin, Chen; Kralik, Stephen; Zhao, Ye

    2015-11-01

    In this work, we demonstrate the validity of 4-D patient-specific computational hemodynamics (PSCH) based on 3-D time-of-flight (TOF) MR angiography (MRA) and 2-D electrocardiogram (ECG) gated phase contrast (PC) images. The mesoscale lattice Boltzmann method (LBM) is employed to segment morphological arterial geometry from TOF MRA, to extract velocity profiles from ECG PC images, and to simulate fluid dynamics on a unified GPU accelerated computational platform. Two healthy volunteers are recruited to participate in the study. For each volunteer, a 3-D high resolution TOF MRA image and 10 2-D ECG gated PC images are acquired to provide the morphological geometry and the time-varying flow velocity profiles for necessary inputs of the PSCH. Validation results will be presented through comparisons of LBM vs. 4D Flow Software for flow rates and LBM simulation vs. MRA measurement for blood flow velocity maps. Indiana University Health (IUH) Values Fund.

  9. An auto-tuning method for focusing and astigmatism correction in HAADF-STEM, based on the image contrast transfer function.

    PubMed

    Baba, N; Terayama, K; Yoshimizu, T; Ichise, N; Tanaka, N

    2001-01-01

    An auto-tuning method for high-angle annular detector dark field scanning transmission electron microscopy (HAADF-STEM) is proposed which corrects the defocus to the optimum Scherzer focus and compensates the astigmatism. Because the method is based on the image contrast transfer function formulated for the HAADF-STEM, the defocus and the astigmatism are accurately measured from input of two different defocus images. The method is designed to work independent of object function in the linear imaging model by analysing the spectral ratio between two Fourier spectra of their images, which is useful for cases where the spectrum of object function is not uniformly spread out over the reciprocal space. The method was preliminarily tested in a Hitachi HD-2000 STEM, and successful results of the auto-tunings from the viewpoint of verification of the algorithm were obtained using general specimens of Au fine particles and a thin section of a semiconductor device.

  10. Gd(DOTAlaP): Exploring the Boundaries of Fast Water Exchange in Gadolinium-Based Magnetic Resonance Imaging Contrast Agents

    PubMed Central

    2015-01-01

    Here, we describe the synthesis of the single amino acid chelator DOTAlaP and four of its derivatives. The corresponding gadolinium(III) complexes were investigated for their kinetic inertness, relaxometric properties at a range of fields and temperatures, water exchange rate, and interaction with human serum albumin (HSA). Derivatives with one inner-sphere water (q = 1) were determined to have a mean water residency time between 8 and 6 ns in phoshate-buffered saline at 37 °C. The corresponding europium complexes were also formed and used to obtain information on the hydration number of the corresponding coordination complexes. Two complexes capable of binding HSA were also synthesized, of which one, Gd(5b), contains no inner-sphere water, while the other derivative, Gd(4b), is a mixture of ca. 15% q =1 and 85% q = 0. In the presence of HSA, the latter displayed a very short mean water residency time (τM310 = 2.4 ns) and enhanced relaxivity at intermediate and high fields. The kinetic inertness of Gd(4b) with respect to complex dissociation was decreased compared to its DOTAla analogue but still 100-fold more inert than [Gd(BOPTA)(H2O)]2–. Magnetic resonance imaging in mice showed that Gd(4b) was able to provide 38% better vessel to muscle contrast compared to the clinically used HSA binding agent MS-325. PMID:24922178

  11. Development of neutron tomography and phase contrast imaging technique

    SciTech Connect

    Kashyap, Y. S.; Agrawal, Ashish; Sarkar, P. S.; Shukla, Mayank; Sinha, Amar

    2013-02-05

    This paper presents design and development of a state of art neutron imaging technique at CIRUS reactor with special reference for techniques adopted for tomography and phase contrast imaging applications. Different components of the beamline such as collimator, shielding, sample manipulator, digital imaging system were designed keeping in mind the requirements of data acquisition time and resolution. The collimator was designed in such a way that conventional and phase contrast imaging can be done using same collimator housing. We have done characterization of fuel pins, study of hydride blisters in pressure tubes hydrogen based cells, two phase flow visualization, and online study of locomotive parts etc. using neutron tomography and radiography technique. We have also done some studies using neutron phase contrast imaging technique on this beamline.

  12. Intraoperative imaging using intravascular contrast agent

    NASA Astrophysics Data System (ADS)

    Watson, Jeffrey R.; Martirosyan, Nikolay; Garland, Summer; Lemole, G. Michael; Romanowski, Marek

    2016-03-01

    Near-infrared (NIR) contrast agents are becoming more frequently studied in medical imaging due to their advantageous characteristics, most notably the ability to capture near-infrared signal across the tissue and the safety of the technique. This produces a need for imaging technology that can be specific for both the NIR dye and medical application. Indocyanine green (ICG) is currently the primary NIR dye used in neurosurgery. Here we report on using the augmented microscope we described previously for image guidance in a rat glioma resection. Luc-C6 cells were implanted in a rat in the left-frontal lobe and grown for 22 days. Surgical resection was performed by a neurosurgeon using augmented microscopy guidance with ICG contrast. Videos and images were acquired to evaluate image quality and resection margins. ICG accumulated in the tumor tissue due to enhanced permeation and retention from the compromised bloodbrain- barrier. The augmented microscope was capable of guiding the rat glioma resection and intraoperatively highlighted tumor tissue regions via ICG fluorescence under normal illumination of the surgical field.

  13. Variational contrast enhancement guided by global and local contrast measurements for single-image defogging

    NASA Astrophysics Data System (ADS)

    Zhou, Li; Bi, Du-Yan; He, Lin-Yuan

    2015-01-01

    The visibility of images captured in foggy conditions is impaired severely by a decrease in the contrasts of objects and veiling with a characteristic gray hue, which may limit the performance of visual applications out of doors. Contrast enhancement together with color restoration is a challenging mission for conventional fog-removal methods, as the degrading effect of fog is largely dependent on scene depth information. Nowadays, people change their minds by establishing a variational framework for contrast enhancement based on a physically based analytical model, unexpectedly resulting in color distortion, dark-patch distortion, or fuzzy features of local regions. Unlike previous work, our method treats an atmospheric veil as a scattering disturbance and formulates a foggy image as an energy functional minimization to estimate direct attenuation, originating from the work of image denoising. In addition to a global contrast measurement based on a total variation norm, an additional local measurement is designed in that optimal problem for the purpose of digging out more local details as well as suppressing dark-patch distortion. Moreover, we estimate the airlight precisely by maximization with a geometric constraint and a natural image prior in order to protect the faithfulness of the scene color. With the estimated direct attenuation and airlight, the fog-free image can be restored. Finally, our method is tested on several benchmark and realistic images evaluated by two assessment approaches. The experimental results imply that our proposed method works well compared with the state-of-the-art defogging methods.

  14. The TRENDS High-Contrast Imaging Program

    NASA Astrophysics Data System (ADS)

    Crepp, Justin

    2014-08-01

    We have established a multi-disciplinary program that combines precise Doppler measurements with high-contrast imaging. Using long-term RV accelerations (or 'trends'), we take a much-needed short-cut for identifying promising high-contrast imaging targets. The goal of this project is to directly detect and characterize the companions responsible for accelerating their host stars. By working at the interface of two powerful and complementary planet detection techniques, we are able to construct 3d-orbits, calculate dynamical masses, and explicitly calibrate theoretical atmospheric models for substellar objects in a regime where they currently break-down (low temperatures). Using a sample of non-detections, the TRENDS program also provides the ability to robustly determine the occurrence rate of giant planets from 0-20 AU through statistical inference.

  15. APT-Weighted and NOE-Weighted Image Contrasts in Glioma with Different RF Saturation Powers Based on Magnetization Transfer Ratio Asymmetry Analyses

    PubMed Central

    Zhou, Jinyuan; Hong, Xiaohua; Zhao, Xuna; Gao, Jia-Hong; Yuan, Jing

    2013-01-01

    Purpose To investigate the saturation-power dependence of amide proton transfer (APT)-weighted and nuclear Overhauser enhancement (NOE)-weighted image contrasts in a rat glioma model at 4.7 T. Methods 9L tumor-bearing rats (n = 8) and fresh eggs (n = 4) were scanned on a 4.7-T animal MRI scanner. Z-spectra over an offset range of ±6 ppm were acquired with different saturation powers, followed by the magnetization transfer-ratio (MTR) asymmetry analyses around the water resonance. Results The NOE signal upfield from the water resonance (−2.5 to −5 ppm) was clearly visible at lower saturation powers (e.g., 0.6 μT) and was larger in the contralateral normal brain tissue than in the tumor. Conversely, the APT effect downfield from the water resonance was observed at relatively higher saturation powers (e.g., 2.1 μT) and was larger in the tumor than in the contralateral normal brain tissue. The NOE decreased the APT-weighted image signal, based on the MTR asymmetry analysis, but increased the APT-weighted image contrast between the tumor and contralateral normal brain tissue. Conclusion The APT and NOE image signals in tumor are maximized at different saturation powers. The saturation power of roughly 2 μT is ideal for APT-weighted imaging at clinical B0 field strengths. PMID:23661598

  16. Experimental setup and the system performance for single-grid-based phase-contrast x-ray imaging (PCXI) with a microfocus x-ray tube

    NASA Astrophysics Data System (ADS)

    Lim, Hyunwoo; Park, Yeonok; Cho, Hyosung; Je, Uikyu; Hong, Daeki; Park, Chulkyu; Woo, Taeho; Lee, Minsik; Kim, Jinsoo; Chung, Nagkun; Kim, Jinwon; Kim, Jinguk

    2015-08-01

    In this work, we investigated a simplified approach to phase-contrast x-ray imaging (PCXI) by using a single antiscatter grid and a microfocus x-ray tube, which has potential to open the way to further widespread use of PCXI into the related application areas. We established a table-top setup for PCXI studies of biological and non-biological samples and investigated the system performance. The PCXI system consists of a focused-linear grid having a strip density of 200 lines/in. (JPI Healthcare Corp.), a microfocus x-ray tube having a focal spot size of about 5 μm (Hamamatsu, L7910), and a high-resolution CMOS imaging detector having a pixel size of 48 μm (Rad-icon Imaging Corp., Shad-o-Box 2048). By using our prototype system, we successfully obtained attenuation, scattering, and differential phase-contrast x-ray images of improved visibility from the raw images of several samples at x-ray tube conditions of 50 kVp and 6 mAs. Our initial results indicate that the single-grid-based approach seems a useful method for PCXI with great simplicity and minimal requirements on the setup alignment.

  17. High Resolution X-Ray Phase Contrast Imaging With Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2006-06-01

    microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray source for mammography: Feasibility study...W81XWH-04-1-0481 TITLE: High Resolution X - ray Phase Contrast Imaging With Acoustic Tissue-Selective Contrast Enhancement PRINCIPAL...REPORT TYPE Annual 3. DATES COVERED (From - To) 1 Jun 2005 – 31 May 2006 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER High Resolution X - ray

  18. Endogenous contrast blood flow imaging in embryonic hearts using hemoglobin contrast subtraction angiography

    PubMed Central

    Deniz, Engin; Jonas, Stephan; Khokha, Mustafa; Choma, Michael A.

    2013-01-01

    The genetic basis of congenital heart disease (CHD) is yet to be defined, and the interactions between the malformed heart and biomechanical cardiac performance remain poorly understood. Functional optical imaging enables detailed biomechanical phenotyping of cardiac dysfunction in small animal models, which in turn enables specific gene-phenotype relationship. We have developed a new microangiography technique based on flow imaging using endogenous hemoglobin contrast enabling in vivo assessment and biomechanical phenotyping of Xenopus tropicalis embryonic heart. We demonstrated that hemoglobin contrast angiography can be used to quantify physiological response to treatment with well-established cardioactive drugs. PMID:22825198

  19. Motility contrast imaging of live porcine cumulus-oocyte complexes

    NASA Astrophysics Data System (ADS)

    An, Ran; Turek, John; Machaty, Zoltan; Nolte, David

    2013-02-01

    Freshly-harvested porcine oocytes are invested with cumulus granulosa cells in cumulus-oocyte complexes (COCs). The cumulus cell layer is usually too thick to image the living oocyte under a conventional microscope. Therefore, it is difficult to assess the oocyte viability. The low success rate of implantation is the main problem for in vitro fertilization. In this paper, we demonstrate our dynamic imaging technique called motility contrast imaging (MCI) that provides a non-invasive way to monitor the COCs before and after maturation. MCI shows a change of intracellular activity during oocyte maturation, and a measures dynamic contrast between the cumulus granulosa shell and the oocytes. MCI also shows difference in the spectral response between oocytes that were graded into quality classes. MCI is based on shortcoherence digital holography. It uses intracellular motility as the endogenous imaging contrast of living tissue. MCI presents a new approach for cumulus-oocyte complex assessment.

  20. Angular Differential Imaging: a Powerful High-Contrast Imaging Technique

    SciTech Connect

    Marois, C; Lafreniere, D; Doyon, R; Macintosh, B; Nadeau, D

    2005-11-07

    Angular differential imaging is a high-contrast imaging technique that reduces speckle noise from quasi-static optical aberrations and facilitates the detection of faint nearby companions. A sequence of images is acquired with an altitude/azimuth telescope, the instrument rotator being turned off. This keeps the instrument and telescope optics aligned, stabilizes the instrumental PSF and allows the field of view to rotate with respect to the instrument. For each image, a reference PSF obtained from other images of the sequence is subtracted. All residual images are then rotated to align the field and are median combined. Observed performances are reported for Gemini Altair/NIRI data. Inside the speckle dominated region of the PSF, it is shown that quasi-static PSF noise can be reduced by a factor {approx}5 for each image subtraction. The combination of all residuals then provides an additional gain of the order of the square root of the total number of images acquired. To our knowledge, this is the first time an acquisition strategy and reduction pipeline designed for speckle attenuation and high contrast imaging is demonstrated to significantly get better detection limits with longer integration times at all angular separations. A PSF noise attenuation of 100 was achieved from 2-hour long sequences of images of Vega, reaching a 5-sigma contrast of 20 magnitudes for separations greater than 7''. This technique can be used with currently available instruments to search for {approx} 1 M{sub Jup} exoplanets with orbits of radii between 50 and 300 AU around nearby young stars. The possibility of combining the technique with other high-contrast imaging methods is briefly discussed.

  1. Adaptation of a clustered lumpy background model for task-based image quality assessment in x-ray phase-contrast mammography

    PubMed Central

    Zysk, Adam M.; Brankov, Jovan G.; Wernick, Miles N.; Anastasio, Mark A.

    2012-01-01

    Purpose: Since the introduction of clinical x-ray phase-contrast mammography (PCM), a technique that exploits refractive-index variations to create edge enhancement at tissue boundaries, a number of optimization studies employing physical image-quality metrics have been performed. Ideally, task-based assessment of PCM would have been conducted with human readers. These studies have been limited, however, in part due to the large parameter-space of PCM system configurations and the difficulty of employing expert readers for large-scale studies. It has been proposed that numerical observers can be used to approximate the statistical performance of human readers, thus enabling the study of task-based performance over a large parameter-space. Methods: Methods are presented for task-based image quality assessment of PCM images with a numerical observer, the most significant of which is an adapted lumpy background from the conventional mammography literature that accounts for the unique wavefield propagation physics of PCM image formation and will be used with a numerical observer to assess image quality. These methods are demonstrated by performing a PCM task-based image quality study using a numerical observer. This study employs a signal-known-exactly, background-known-statistically Bayesian ideal observer method to assess the detectability of a calcification object in PCM images when the anode spot size and calcification diameter are varied. Results: The first realistic model for the structured background in PCM images has been introduced. A numerical study demonstrating the use of this background model has compared PCM and conventional mammography detection of calcification objects. The study data confirm the strong PCM calcification detectability dependence on anode spot size. These data can be used to balance the trade-off between enhanced image quality and the potential for motion artifacts that comes with use of a reduced spot size and increased exposure time

  2. Molecular imaging with targeted contrast ultrasound.

    PubMed

    Piedra, Mark; Allroggen, Achim; Lindner, Jonathan R

    2009-01-01

    Molecular imaging with contrast-enhanced ultrasound uses targeted microbubbles that are retained in diseased tissue. The resonant properties of these microbubbles produce acoustic signals in an ultrasound field. The microbubbles are targeted to diseased tissue by using certain chemical constituents in the microbubble shell or by attaching disease-specific ligands such as antibodies to the microbubble. In this review, we discuss the applications of this technique to pathological states in the cerebrovascular system including atherosclerosis, tumor angiogenesis, ischemia, intravascular thrombus, and inflammation.

  3. Towards An Advanced Graphene-Based Magnetic Resonance Imaging Contrast Agent: Sub-acute Toxicity and Efficacy Studies in Small Animals

    PubMed Central

    Kanakia, Shruti; Toussaint, Jimmy; Hoang, Dung Minh; Mullick Chowdhury, Sayan; Lee, Stephen; Shroyer, Kenneth R.; Moore, William; Wadghiri, Youssef Z.; Sitharaman, Balaji

    2015-01-01

    Current clinical Gd3+-based T1 magnetic resonance imaging (MRI) contrast agents (CAs) are suboptimal or unsuitable, especially at higher magnetic fields (>1.5 Tesla) for advanced MRI applications such as blood pool, cellular and molecular imaging. Herein, towards the goal of developing a safe and more efficacious high field T1 MRI CA for these applications, we report the sub-acute toxicity and contrast enhancing capabilities of a novel nanoparticle MRI CA comprising of manganese (Mn2+) intercalated graphene nanoparticles functionalized with dextran (hereafter, Mangradex) in rodents. Sub-acute toxicology performed on rats intravenously injected with Mangradex at 1, 50 or 100 mg/kg dosages 3 times per week for three weeks indicated that dosages ≤50 mg/kg could serve as potential diagnostic doses. Whole body 7 Tesla MRI performed on mice injected with Mangradex at a potential diagnostic dose (25 mg/kg or 455 nanomoles Mn2+/kg; ~2 orders of magnitude lower than the paramagnetic ion concentration in a typical clinical dose) showed persistent (up to at least 2 hours) contrast enhancement in the vascular branches (Mn2+ concentration in blood at steady state = 300 ppb, per voxel = 45 femtomoles). The results lay the foundations for further development of Mangradex as a vascular and cellular/ molecular MRI probe. PMID:26625867

  4. Qualitative and Quantitative Imaging Evaluation of Renal Cell Carcinoma Subtypes with Grating-based X-ray Phase-contrast CT

    PubMed Central

    Braunagel, Margarita; Birnbacher, Lorenz; Willner, Marian; Marschner, Mathias; De Marco, Fabio; Viermetz, Manuel; Notohamiprodjo, Susan; Hellbach, Katharina; Auweter, Sigrid; Link, Vera; Woischke, Christine; Reiser, Maximilian F.; Pfeiffer, Franz; Notohamiprodjo, Mike; Herzen, Julia

    2017-01-01

    Current clinical imaging methods face limitations in the detection and correct characterization of different subtypes of renal cell carcinoma (RCC), while these are important for therapy and prognosis. The present study evaluates the potential of grating-based X-ray phase-contrast computed tomography (gbPC-CT) for visualization and characterization of human RCC subtypes. The imaging results for 23 ex vivo formalin-fixed human kidney specimens obtained with phase-contrast CT were compared to the results of the absorption-based CT (gbCT), clinical CT and a 3T MRI and validated using histology. Regions of interest were placed on each specimen for quantitative evaluation. Qualitative and quantitative gbPC-CT imaging could significantly discriminate between normal kidney cortex (54 ± 4 HUp) and clear cell (42 ± 10), papillary (43 ± 6) and chromophobe RCCs (39 ± 7), p < 0.05 respectively. The sensitivity for detection of tumor areas was 100%, 50% and 40% for gbPC-CT, gbCT and clinical CT, respectively. RCC architecture like fibrous strands, pseudocapsules, necrosis or hyalinization was depicted clearly in gbPC-CT and was not equally well visualized in gbCT, clinical CT and MRI. The results show that gbPC-CT enables improved discrimination of normal kidney parenchyma and tumorous tissues as well as different soft-tissue components of RCCs without the use of contrast media. PMID:28361951

  5. Coronary magnetic resonance vein imaging: imaging contrast, sequence, and timing.

    PubMed

    Nezafat, Reza; Han, Yuchi; Peters, Dana C; Herzka, Daniel A; Wylie, John V; Goddu, Beth; Kissinger, Kraig K; Yeon, Susan B; Zimetbaum, Peter J; Manning, Warren J

    2007-12-01

    Recently, there has been increased interest in imaging the coronary vein anatomy to guide interventional cardiovascular procedures such as cardiac resynchronization therapy (CRT), a device therapy for congestive heart failure (CHF). With CRT the lateral wall of the left ventricle is electrically paced using a transvenous coronary sinus lead or surgically placed epicardial lead. Proper transvenous lead placement is facilitated by the knowledge of the coronary vein anatomy. Cardiovascular MR (CMR) has the potential to image the coronary veins. In this study we propose and test CMR techniques and protocols for imaging the coronary venous anatomy. Three aspects of design of imaging sequence were studied: magnetization preparation schemes (T(2) preparation and magnetization transfer), imaging sequences (gradient-echo (GRE) and steady-state free precession (SSFP)), and imaging time during the cardiac cycle. Numerical and in vivo studies both in healthy and CHF subjects were performed to optimize and demonstrate the utility of CMR for coronary vein imaging. Magnetization transfer was superior to T(2) preparation for contrast enhancement. Both GRE and SSFP were viable imaging sequences, although GRE provided more robust results with better contrast. Imaging during the end-systolic quiescent period was preferable as it coincided with the maximum size of the coronary veins.

  6. Contrast Media in PET/Computed Tomography Imaging.

    PubMed

    Dhull, Varun Singh; Rana, Neelima; Nazar, Aftab Hasan

    2016-01-01

    Is there a need for the contrast-enhanced PET/computed tomography (CT) scan or is the low-dose, non-contrast-enhanced PET/CT scan sufficient? The topic has been debated time and again. Although low-dose noncontrast CT serves the purpose of simple anatomic correlation and attenuation correction of PET images, many times patients have to undergo additional contrast-enhanced diagnostic imaging modalities, which may lead to a delay in decision-making. In this review, the authors have addressed various such issues related to the use of contrast agents and special techniques of clinical interest based on their utility in dual-modality PET/CT.

  7. Exogenous contrast agents for thermoacoustic imaging: An investigation into the underlying sources of contrast

    SciTech Connect

    Ogunlade, Olumide Beard, Paul

    2015-01-15

    Purpose: Thermoacoustic imaging at microwave excitation frequencies is limited by the low differential contrast exhibited by high water content tissues. To overcome this, exogenous thermoacoustic contrast agents based on gadolinium compounds, iron oxide, and single wall carbon nanotubes have previously been suggested and investigated. However, these previous studies did not fully characterize the electric, magnetic, and thermodynamic properties of these agents thus precluding identification of the underlying sources of contrast. To address this, measurements of the complex permittivity, complex permeability, DC conductivity, and Grüneisen parameter have been made. These measurements allowed the origins of the contrast provided by each substance to be identified. Methods: The electric and magnetic properties of the contrast agents were characterized at 3 GHz using two rectangular waveguide cavities. The DC conductivity was measured separately using a conductivity meter. Thermoacoustic signals were then acquired and compared to those generated in water. Finally, 3D electromagnetic simulations were used to decouple the different contributions to the absorbed power density. Results: It was found that the gadolinium compounds provided appreciable electric contrast but not originating from the gadolinium itself. The contrast was either due to dissociation of the gadolinium salt which increased ionic conductivity or its nondissociated polar fraction which increased dielectric polarization loss or a combination of both. In addition, very high concentrations were required to achieve appreciable contrast, to the extent that the Grüneisen parameter increased significantly and became a source of contrast. Iron oxide particles were found to produce low but measurable dielectric contrast due to dielectric polarization loss, but this is attributed to the coating of the particles not the iron oxide. Single wall carbon nanotubes did not provide measurable contrast of any type

  8. TAILORING X-RAY BEAM ENERGY SPECTRUM TO ENHANCE IMAGE QUALITY OF NEW RADIOGRAPHY CONTRAST AGENTS BASED ON GD OR OTHER LANTHANIDES.

    SciTech Connect

    DILMANIAN,F.A.; WEINMANN,H.J.; ZHONG,Z.; BACARIAN,T.; RIGON,L.; BUTTON,T.M.; REN,B.; WU,X.Y.; ZHONG,N.; ATKINS,H.L.

    2001-02-17

    Gadovist, a 1.0-molar Gd contrast agent from Schering AG, Berlin Germany, in use in clinical MPI in Europe, was evaluated as a radiography contrast agent. In a collaboration with Brookhaven National Laboratory (BNL), Schering AG is developing several such lanthanide-based contrast agents, while BNL evaluates them using different x-my beam energy spectra. These energy spectra include a ''truly'' monochromatic beam (0.2 keV energy bandwidth) from the National Synchrotron Light Source (NSLS), BNL, tuned above the Gd K-edge, and x-ray-tube beams from different kVp settings and beam filtrations. Radiographs of rabbits' kidneys were obtained with Gadovist at the NSLS. Furthermore, a clinical radiography system was used for imaging rabbits' kidneys comparing Gadovist and Conray, an iodinated contrast agent. The study, using 74 kVp and standard Al beam filter for Conray and 66 kVp and an additional 1.5 mm Cu beam filter for Gadovist, produced comparable images for Gadovist and Conray; the injection volumes were the same, while the radiation absorbed dose for Gadovist was slightly smaller. A bent-crystal silicon monochromator operating in the Laue diffraction mode was developed and tested with a conventional x-ray tube beam; it narrows the energy spectrum to about 4 keV around the anode tungsten's Ku line. Preliminary beam-flux results indicate that the method could be implemented in clinical CT if x-ray tubes with {approximately} twice higher output become available.

  9. Tailoring the x-ray beam energy spectrum to enhance image quality of new radiography contrast agents based on Gd or other lanthanides

    NASA Astrophysics Data System (ADS)

    Dilmanian, F. Avraham; Weinmann, Hanns-Joachim; Zhong, Zhong; Bacarian, Tigran; Rigon, Luigi; Button, Terry M.; Ren, Baorui; Wu, Xiaoye; Zhong, Nan; Atkins, Harold L.

    2001-06-01

    Gadovist, a 1.0-molar Gd contrast agent from Schering AG, Berlin, Germany, in use in clinical MRI in Europe, was evaluated as a radiography contrast agent. In a collaboration with Brookhaven National Laboratory (BNL), Schering AG is developing several such lanthanide-based contrast agents, while BNL evaluates them using different x-ray beam energy spectra. These energy spectra include a 'truly' monochromatic beam (0.2 keV energy bandwidth) from the National Synchrotron Light Source (NSLS), BNL, tuned above the Gd K-edge, and x-ray-tube beams from different kVp settings and beam filtrations. Radiographs of rabbits' kidneys were obtained with Gadovist at the NSLS. Furthermore, a clinical radiography system was used for imaging rabbits' kidneys comparing Gadovist and Conray, an iodinated contrast agent. The study, using 74 kVp and standard Al beam filter for Conray and 66 kVp and an additional 1.5 mm Cu beam filter for Gadovist, produced comparable images for Gadovist and Conray; the injection volumes were the same, while the radiation absorbed dose for Gadovist was slightly smaller. A bent-crystal silicon monochromator operating in the Laue diffraction mode was developed and tested with a conventional x-ray tube beam; it narrows the energy spectrum to about 4 keV around the anode tungsten's K' line. Preliminary beam-flux results indicate that the method could be implemented in clinical CT if x-ray tubes with approximately twice higher output become available.

  10. Contrast and resolution in direct Fresnel diffraction phase-contrast imaging with partially coherent x-ray source

    SciTech Connect

    Han Shensheng; Yu Hong; Cheng Jing; Gao Chen; Luo Zhenlin

    2004-10-01

    A general treatment of x-ray image formation by direct Fresnel diffraction with partially coherent hard x rays is presented. Contrast and resolution are the criteria used to specify the visibility of an image, which depend primarily on the spatial coherence of the illumination and the distance from object to the image, with chromatic coherence of lesser importance. The dependence of the quality of phase-contrast images on the parameters of in-line imaging configuration is described quantitatively. The influence of spatial coherence of hard x-ray source on the imaging quality is also discussed based on the partially coherent direct Fresnel diffraction phase-contrast imaging theory. Experimental results are also presented for phase-contrast x-ray images with partially coherent hard x rays.

  11. Nanoengineered multimodal contrast agent for medical image guidance

    NASA Astrophysics Data System (ADS)

    Perkins, Gregory J.; Zheng, Jinzi; Brock, Kristy; Allen, Christine; Jaffray, David A.

    2005-04-01

    Multimodality imaging has gained momentum in radiation therapy planning and image-guided treatment delivery. Specifically, computed tomography (CT) and magnetic resonance (MR) imaging are two complementary imaging modalities often utilized in radiation therapy for visualization of anatomical structures for tumour delineation and accurate registration of image data sets for volumetric dose calculation. The development of a multimodal contrast agent for CT and MR with prolonged in vivo residence time would provide long-lasting spatial and temporal correspondence of the anatomical features of interest, and therefore facilitate multimodal image registration, treatment planning and delivery. The multimodal contrast agent investigated consists of nano-sized stealth liposomes encapsulating conventional iodine and gadolinium-based contrast agents. The average loading achieved was 33.5 +/- 7.1 mg/mL of iodine for iohexol and 9.8 +/- 2.0 mg/mL of gadolinium for gadoteridol. The average liposome diameter was 46.2 +/- 13.5 nm. The system was found to be stable in physiological buffer over a 15-day period, releasing 11.9 +/- 1.1% and 11.2 +/- 0.9% of the total amounts of iohexol and gadoteridol loaded, respectively. 200 minutes following in vivo administration, the contrast agent maintained a relative contrast enhancement of 81.4 +/- 13.05 differential Hounsfield units (ΔHU) in CT (40% decrease from the peak signal value achieved 3 minutes post-injection) and 731.9 +/- 144.2 differential signal intensity (ΔSI) in MR (46% decrease from the peak signal value achieved 3 minutes post-injection) in the blood (aorta), a relative contrast enhancement of 38.0 +/- 5.1 ΔHU (42% decrease from the peak signal value achieved 3 minutes post-injection) and 178.6 +/- 41.4 ΔSI (62% decrease from the peak signal value achieved 3 minutes post-injection) in the liver (parenchyma), a relative contrast enhancement of 9.1 +/- 1.7 ΔHU (94% decrease from the peak signal value achieved 3 minutes

  12. Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging

    SciTech Connect

    Kitchen, Marcus J.; Williams, Ivan; Irvine, Sarah C.; Morgan, Michael J.; Paganin, David M.; Lewis, Rob A.; Pavlov, Konstantin; Hooper, Stuart B.; Wallace, Megan J.; Siu, Karen K. W.; Yagi, Naoto; Uesugi, Kentaro

    2007-01-19

    Clearance of liquid from the airways at birth is a poorly understood process, partly due to the difficulties of observing and measuring the distribution of air within the lung. Imaging dynamic processes within the lung in vivo with high contrast and spatial resolution is therefore a major challenge. However, phase contrast X-ray imaging is able to exploit inhaled air as a contrast agent, rendering the lungs of small animals visible due to the large changes in the refractive index at air/tissue interfaces. In concert with the high spatial resolution afforded by X-ray imaging systems (<100 {mu}m), propagation-based phase contrast imaging is ideal for studying lung development. To this end we have utilized intense, monochromatic synchrotron radiation, together with a fast readout CCD camera, to study fluid clearance from the lungs of rabbit pups at birth. Local rates of fluid clearance have been measured from the dynamic sequences using a single image phase retrieval algorithm.

  13. Functional magnetic resonance imaging: imaging techniques and contrast mechanisms.

    PubMed Central

    Howseman, A M; Bowtell, R W

    1999-01-01

    Functional magnetic resonance imaging (fMRI) is a widely used technique for generating images or maps of human brain activity. The applications of the technique are widespread in cognitive neuroscience and it is hoped they will eventually extend into clinical practice. The activation signal measured with fMRI is predicated on indirectly measuring changes in the concentration of deoxyhaemoglobin which arise from an increase in blood oxygenation in the vicinity of neuronal firing. The exact mechanisms of this blood oxygenation level dependent (BOLD) contrast are highly complex. The signal measured is dependent on both the underlying physiological events and the imaging physics. BOLD contrast, although sensitive, is not a quantifiable measure of neuronal activity. A number of different imaging techniques and parameters can be used for fMRI, the choice of which depends on the particular requirements of each functional imaging experiment. The high-speed MRI technique, echo-planar imaging provides the basis for most fMRI experiments. The problems inherent to this method and the ways in which these may be overcome are particularly important in the move towards performing functional studies on higher field MRI systems. Future developments in techniques and hardware are also likely to enhance the measurement of brain activity using MRI. PMID:10466145

  14. High Resolution X-Ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2005-06-01

    microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray ...high spatial coherence, such as synchrotrons 46, microfocus x - ray tubes 7, or laser plasma x - ray sources 8,9are employed is the phase contrast component...imaging apparatus to determine the deflection of the bead as a function of acoustic pressure. The x - rays , generated by a microfocus x - ray tube

  15. Safety of the Gadolinium-Based Contrast Agents for Magnetic Resonance Imaging, Focusing in Part on Their Accumulation in the Brain and Especially the Dentate Nucleus.

    PubMed

    Runge, Val M

    2016-05-01

    The established class of intravenous contrast media for magnetic resonance imaging is the gadolinium chelates, more generally referred to as the gadolinium-based contrast agents (GBCAs). These can be differentiated on the basis of stability in vivo, with safety and tolerability of the GBCAs dependent upon chemical and biologic inertness. This review discusses first the background in terms of development of these agents and safety discussions therein, and second their relative stability based both on in vitro studies and clinical observations before and including the advent of nephrogenic systemic fibrosis. This sets the stage for the subsequent focus of the review, the current knowledge regarding accumulation of gadolinium in the brain and specifically the dentate nucleus after intravenous administration of the GBCAs and differentiation among agents on this basis. The information available to date, from the initial conception of these agents in 1981 to the latest reports concerning safety, demonstrates a significant difference between the macrocyclic and linear chelates. The review concludes with a discussion of the predictable future, which includes, importantly, a reassessment of the use of the linear GBCAs or a subset thereof.

  16. Characterizing growth patterns in longitudinal MRI using image contrast

    NASA Astrophysics Data System (ADS)

    Vardhan, Avantika; Prastawa, Marcel; Vachet, Clement; Piven, Joseph; Gerig, Guido

    2014-03-01

    Understanding the growth patterns of the early brain is crucial to the study of neuro-development. In the early stages of brain growth, a rapid sequence of biophysical and chemical processes take place. A crucial component of these processes, known as myelination, consists of the formation of a myelin sheath around a nerve fiber, enabling the effective transmission of neural impulses. As the brain undergoes myelination, there is a subsequent change in the contrast between gray matter and white matter as observed in MR scans. In this work, gray-white matter contrast is proposed as an effective measure of appearance which is relatively invariant to location, scanner type, and scanning conditions. To validate this, contrast is computed over various cortical regions for an adult human phantom. MR (Magnetic Resonance) images of the phantom were repeatedly generated using different scanners, and at different locations. Contrast displays less variability over changing conditions of scan compared to intensity-based measures, demonstrating that it is less dependent than intensity on external factors. Additionally, contrast is used to analyze longitudinal MR scans of the early brain, belonging to healthy controls and Down's Syndrome (DS) patients. Kernel regression is used to model subject-specific trajectories of contrast changing with time. Trajectories of contrast changing with time, as well as time-based biomarkers extracted from contrast modeling, show large differences between groups. The preliminary applications of contrast based analysis indicate its future potential to reveal new information not covered by conventional volumetric or deformation-based analysis, particularly for distinguishing between normal and abnormal growth patterns.

  17. Acoustically modulated x-ray phase contrast imaging.

    PubMed

    Hamilton, Theron J; Bailat, Claude J; Rose-Petruck, Christoph; Diebold, Gerald J

    2004-11-07

    We report the use of ultrasonic radiation pressure with phase contrast x-ray imaging to give an image proportional to the space derivative of a conventional phase contrast image in the direction of propagation of an ultrasonic beam. Intense ultrasound is used to exert forces on objects within a body giving displacements of the order of tens to hundreds of microns. Subtraction of images made with and without the ultrasound field gives an image that removes low spatial frequency features and highlights high frequency features. The method acts as an acoustic 'contrast agent' for phase contrast x-ray imaging, which in soft tissue acts to highlight small density changes.

  18. Gold nanorods: contrast agents for photoacoustic imaging?

    NASA Astrophysics Data System (ADS)

    Ungureanu, C.; Gopal, R. Raja; van Leeuwen, T. G.; Manohar, S.

    2007-07-01

    Gold nanorods are seen as possible contrast agents for photoacoustic imaging since they have strong absorption peaks at near-infrared wavelengths. Also they are easy to conjugate with various proteins. If these particles can be conjugated with cancer affinity proteins then these particles can accumulate specifically at a tumor site. By detecting the presence of accumulation of gold nanorods inside the tissue the indirect detection of tumor can be realized. When these particles are irradiated with light pulses of appropriate temporal properties and energy the temperature around these particles can be high enough to induce apoptosis or necrosis in the surrounding cells. In order to use these particles at their full potential we must determine precisely their optical properties. We simulated the optical properties of gold nanorods synthesized by us using the DDSCAT code. The simulated spectra agree qualitatively with the spectra determined using spectrometry and also determined using photoacoustic spectroscopy. Further the values of molar extinction coefficient derived from the simulations were similar to the data measured experimentally by other groups. These results validated qualitatively the model used in the simulations. During simulations we found that the choice of the dielectric function used in simulations plays an important role in the results.

  19. Power constrained contrast enhancement based on brightness compensated contrast-tone mapping operation

    NASA Astrophysics Data System (ADS)

    Jung, Cheolkon; Su, Haonan; Wang, Lu; Ke, Peng

    2016-09-01

    We propose power constrained contrast enhancement based on brightness compensated contrast-tone mapping operation (BCCTMO). We adopt brightness compensation to restore the original perceptual luminance and combine tone mapping with contrast enhancement to improve image quality. First, we increase pixel values to compensate for the reduced brightness caused by backlight dimming while maintaining the perceived luminance. Then we perform a contrast-tone mapping operation to reduce the information loss caused by the brightness compensation and enhance contrast in images. Finally, we conduct color scaling to reproduce natural colors. We implement BCCTMO on an Android tablet with an LCD display using mathematical approximation. Experimental results demonstrate that BCCTMO produces high-quality images while minimizing distortions and saving power compared with state-of-the-art methods.

  20. Spatiotemporal laser speckle contrast analysis for blood flow imaging with maximized speckle contrast.

    PubMed

    Qiu, Jianjun; Li, Pengcheng; Luo, Weihua; Wang, Jia; Zhang, Hongyan; Luo, Qingming

    2010-01-01

    Laser speckle contrast imaging is a technique used for imaging blood flow without scanning. Though several studies have attempted to combine spatial and temporal statistics of laser speckle images for reducing image noise as well as preserving acceptable spatiotemporal resolution, the statistical accuracy of these spatiotemporal methods has not been thoroughly compared. Through numerical simulation and animal experiments, this study investigates the changes in the mean speckle contrast values and the relative noise of the speckle contrast images computed by these methods with various numbers of frames and spatial windows. The simulation results show that the maximum relative error of the mean speckle contrast computed by the spatiotemporal laser speckle contrast analysis (STLASCA) method, in which the speckle contrast images are computed by analyzing the 3-D spatiotemporal speckle image cube, is approximately 5%, while it is higher than 13% for other methods. Changes in the mean speckle contrast values and the relative noise computed by these methods for animal experiment data are consistent with the simulation results. Our results demonstrate that STLASCA achieves more accurate speckle contrast, and suggest that STLASCA most effectively utilizes the number of pixels, thus achieving maximized speckle contrast, and thereby maximizing the variation of the laser speckle contrast image.

  1. Spatiotemporal laser speckle contrast analysis for blood flow imaging with maximized speckle contrast

    NASA Astrophysics Data System (ADS)

    Qiu, Jianjun; Li, Pengcheng; Luo, Weihua; Wang, Jia; Zhang, Hongyan; Luo, Qingming

    2010-01-01

    Laser speckle contrast imaging is a technique used for imaging blood flow without scanning. Though several studies have attempted to combine spatial and temporal statistics of laser speckle images for reducing image noise as well as preserving acceptable spatiotemporal resolution, the statistical accuracy of these spatiotemporal methods has not been thoroughly compared. Through numerical simulation and animal experiments, this study investigates the changes in the mean speckle contrast values and the relative noise of the speckle contrast images computed by these methods with various numbers of frames and spatial windows. The simulation results show that the maximum relative error of the mean speckle contrast computed by the spatiotemporal laser speckle contrast analysis (STLASCA) method, in which the speckle contrast images are computed by analyzing the 3-D spatiotemporal speckle image cube, is approximately 5%, while it is higher than 13% for other methods. Changes in the mean speckle contrast values and the relative noise computed by these methods for animal experiment data are consistent with the simulation results. Our results demonstrate that STLASCA achieves more accurate speckle contrast, and suggest that STLASCA most effectively utilizes the number of pixels, thus achieving maximized speckle contrast, and thereby maximizing the variation of the laser speckle contrast image.

  2. Clinical study in phase- contrast mammography: image-quality analysis.

    PubMed

    Longo, Renata; Tonutti, Maura; Rigon, Luigi; Arfelli, Fulvia; Dreossi, Diego; Quai, Elisa; Zanconati, Fabrizio; Castelli, Edoardo; Tromba, Giuliana; Cova, Maria A

    2014-03-06

    The first clinical study of phase-contrast mammography (PCM) with synchrotron radiation was carried out at the Synchrotron Radiation for Medical Physics beamline of the Elettra synchrotron radiation facility in Trieste (Italy) in 2006-2009. The study involved 71 patients with unresolved breast abnormalities after conventional digital mammography and ultrasonography exams carried out at the Radiology Department of Trieste University Hospital. These cases were referred for mammography at the synchrotron radiation facility, with images acquired using a propagation-based phase-contrast imaging technique. To investigate the contribution of phase-contrast effects to the image quality, two experienced radiologists specialized in mammography assessed the visibility of breast abnormalities and of breast glandular structures. The images acquired at the hospital and at the synchrotron radiation facility were compared and graded according to a relative seven-grade visual scoring system. The statistical analysis highlighted that PCM with synchrotron radiation depicts normal structures and abnormal findings with higher image quality with respect to conventional digital mammography.

  3. Small-animal microangiography using phase-contrast X-ray imaging and gas as contrast agent

    NASA Astrophysics Data System (ADS)

    Lundström, Ulf; Larsson, Daniel H.; Westermark, Ulrica K.; Burvall, Anna; Hertz, Hans M.

    2014-03-01

    We use propagation-based phase-contrast X-ray imaging with gas as contrast agent to visualize the microvasculature in small animals like mice and rats. The radiation dose required for absorption X-ray imaging is proportional to the minus fourth power of the structure size to be detected. This makes small vessels impossible to image at reasonable radiation doses using the absorption of conventional iodinated contrast agents. Propagation-based phase contrast gives enhanced contrast for high spatial frequencies by moving the detector away from the sample to let phase variations in the transmitted X-rays develop into intensity variations at the detector. Blood vessels are normally difficult to observe in phase contrast even with iodinated contrast agents as the density difference between blood and most tissues is relatively small. By injecting gas into the blood stream this density difference can be greatly enhanced giving strong phase contrast. One possible gas to use is carbon dioxide, which is a clinically accepted X-ray contrast agent. The gas is injected into the blood stream of patients to temporarily displace the blood in a region and thereby reduce the X-ray absorption in the blood vessels. We have shown that this method can be used to image blood vessels down to 8 μm in diameter in mouse ears. The low dose requirements of this method indicate a potential for live small-animal imaging and longitudinal studies of angiogenesis.

  4. Diffeomorphic Registration of Images with Variable Contrast Enhancement

    PubMed Central

    Janssens, Guillaume; Jacques, Laurent; Orban de Xivry, Jonathan; Geets, Xavier; Macq, Benoit

    2011-01-01

    Nonrigid image registration is widely used to estimate tissue deformations in highly deformable anatomies. Among the existing methods, nonparametric registration algorithms such as optical flow, or Demons, usually have the advantage of being fast and easy to use. Recently, a diffeomorphic version of the Demons algorithm was proposed. This provides the advantage of producing invertible displacement fields, which is a necessary condition for these to be physical. However, such methods are based on the matching of intensities and are not suitable for registering images with different contrast enhancement. In such cases, a registration method based on the local phase like the Morphons has to be used. In this paper, a diffeomorphic version of the Morphons registration method is proposed and compared to conventional Morphons, Demons, and diffeomorphic Demons. The method is validated in the context of radiotherapy for lung cancer patients on several 4D respiratory-correlated CT scans of the thorax with and without variable contrast enhancement. PMID:21197460

  5. Examination of contrast mechanisms in optoacoustic imaging of thermal lesions

    NASA Astrophysics Data System (ADS)

    Richter, Christian; Spirou, Gloria; Oraevsky, Alexander A.; Whelan, William M.; Kolios, Michael C.

    2006-02-01

    Optoacoustic Imaging is based on the thermal expansion of tissue caused by a temperature rise due to absorption of short laser pulses. At constant laser fluence, optoacoustic image contrast is proportional to differences in optical absorption and the thermoacoustic efficiency, expressed by the Grueuneisen parameter, Γ. Γ is proportional to the thermal expansion coefficient, the sound velocity squared and the inverse heat capacity at constant pressure. In thermal therapies, these parameters may be modified in the treated area. In this work experiments were performed to examine the influence of these parameters on image contrast. A Laser Optoacoustic Imaging System (LOIS, Fairway Medical Technologies, Houston, Texas) was used to image tissue phantoms comprised of cylindrical Polyvinyl Chloride Plastisol (PVCP) optical absorbing targets imbedded in either gelatin or PVCP as the background medium. Varying concentrations of Black Plastic Color (BPC) and titanium dioxide (TiO II) were added to targets and background to yield desired tissue relevant optical absorption and effective scattering coefficients, respectively. In thermal therapy experiments, ex-vivo bovine liver was heated with laser fibres (805nm laser at 5 W for 600s) to create regions of tissue coagulation. Lesions formed in the liver tissue were visible using the LOIS system with reasonable correspondence to the actual region of tissue coagulation. In the phantom experiments, contrast could be seen with low optical absorbing targets (μ a of 0.50cm -1 down to 0.13cm-1) embedded in a gelatin background (see manuscript for formula). Therefore, the data suggest that small objects (< 5mm) with low absorption coefficients (in the range < 1cm -1) can be imaged using LOIS. PVCP-targets in gelatin were visible, even with the same optical properties as the gelatin, but different Γ. The enhanced contrast may also be caused by differences in the mechanical properties between the target and the surrounding medium

  6. Phase-contrast imaging using radiation sources based on laser-plasma wakefield accelerators: state of the art and future development

    NASA Astrophysics Data System (ADS)

    Reboredo., D.; Cipiccia, S.; Grant, P. A.; Welsh, G. H.; Grant, D. W.; McKendrick, G.; Subiel, A.; Maneuski, D.; Wiggins, S. M.; Jaroszynski, D. A.

    2015-03-01

    Both the laser-plasma wakefield accelerator (LWFA) and X-ray phase-contrast imaging (XPCi) are promising technologies that are attracting the attention of the scientific community. Conventional X-ray absorption imaging cannot be used as a means of imaging biological material because of low contrast. XPCi overcomes this limitation by exploiting the variation of the refraction index of materials. The contrast obtained is higher than for conventional absorption imaging and requires a lower dose. The LWFA is a new concept of acceleration where electrons are accelerated to very high energy (~150 MeV) in very short distances (mm scale) by surfing plasma waves excited by the passage of an ultra-intense laser pulse (~1018 Wcm-2) through plasma. Electrons in the LWFA can undergo transverse oscillation and emit synchrotron-like (betatron) radiation in a narrow cone around the propagation axis. The properties of the betatron radiation produced by LWFA, such as source size and spectrum, make it an excellent candidate for XPCi. In this work we present the characterization of betatron radiation produced by the LWFA in the ALPHA-X laboratory (University of Strathclyde). We show how phase contrast images can be obtained using the betatron radiation in a free-space propagation configuration and we discuss the potential and limitation of the LWFA driven XPCi.

  7. X-ray fluorescence elemental mapping and microscopy to follow hepatic disposition of a Gd-based magnetic resonance imaging contrast agent.

    PubMed

    Delfino, Riccarda; Altissimo, Matteo; Menk, Ralf Hendrik; Alberti, Roberto; Klatka, Tomasz; Frizzi, Tommaso; Longoni, Antonio; Salomè, Murielle; Tromba, Giuliana; Arfelli, Fulvia; Clai, Milan; Vaccari, Lisa; Lorusso, Vito; Tiribelli, Claudio; Pascolo, Lorella

    2011-12-01

    1. Spatially resolved X-ray fluorescence (XRF) spectroscopy with synchrotron radiation is a technique that allows imaging and quantification of chemical elements in biological specimens with high sensitivity. In the present study, we applied XRF techniques at a macro and micro level to carry out drug distribution studies on ex vivo models to confirm the hepatobiliary disposition of the Gd-based magnetic resonance imaging contrast agent B22956/1. 2. Gd presence was selectively quantified allowing the determination of the time dependent disappearance of the drug from blood and its hepatic accumulation in mice after administration. Elemental mapping highlighted the drug distribution differences between healthy and diseased livers. XRF microanalyses showed that in CCl(4) -induced hepatitis, B22956/1 has greatly reduced hepatic accumulation, shown as a 20-fold reduction of Gd presence. Furthermore, a significant increase of Fe presence was found in steatotic compared with healthy livers, in line with the disease features. 3. The present results show that XRF might be useful in preclinical pharmacological studies with drugs containing exogenous elements. Furthermore, quantitative and high-sensitivity elemental mapping allows simultaneous detection of chemical variation, showing pathological conditions. This approach was useful in suggesting reduced B22956/1 accumulation in steatotic livers, thus opening possible new diagnostic perspectives for this drug.

  8. Image segmentation of nanoscale Zernike phase contrast X-ray computed tomography images

    SciTech Connect

    Kumar, Arjun S.; Mandal, Pratiti; Zhang, Yongjie; Litster, Shawn

    2015-05-14

    Zernike phase contrast is a useful technique for nanoscale X-ray computed tomography (CT) imaging of materials with a low X-ray absorption coefficient. It enhances the image contrast by phase shifting X-ray waves to create changes in amplitude. However, it creates artifacts that hinder the use of traditional image segmentation techniques. We propose an image restoration method that models the X-ray phase contrast optics and the three-dimensional image reconstruction method. We generate artifact-free images through an optimization problem that inverts this model. Though similar approaches have been used for Zernike phase contrast in visible light microscopy, this optimization employs an effective edge detection method tailored to handle Zernike phase contrast artifacts. We characterize this optics-based restoration method by removing the artifacts in and thresholding multiple Zernike phase contrast X-ray CT images to produce segmented results that are consistent with the physical specimens. We quantitatively evaluate and compare our method to other segmentation techniques to demonstrate its high accuracy.

  9. Effects of Image Contrast on Functional MRI Image Registration

    PubMed Central

    Gonzalez-Castillo, Javier; Duthie, Kristen N.; Saad, Ziad S.; Chu, Carlton; Bandettini, Peter A.; Luh, Wen-Ming

    2012-01-01

    Lack of tissue contrast and existing inhomogeneous bias fields from multi-channel coils have the potential to degrade the output of registration algorithms; and consequently degrade group analysis and any attempt to accurately localize brain function. Non-invasive ways to improve tissue contrast in fMRI images include the use of low flip angles (FAs) well below the Ernst angle and longer repetition times (TR). Techniques to correct intensity inhomogeneity are also available in most mainstream fMRI data analysis packages; but are not used as part of the pre-processing pipeline in many studies. In this work, we use a combination of real data and simulations to show that simple-to-implement acquisition/pre-processing techniques can significantly improve the outcome of both functional-to-functional and anatomical-to-functional image registrations. We also emphasize the need of tissue contrast on EPI images to be able to appropriately evaluate the quality of the alignment. In particular, we show that the use of low FAs (e.g., θ≤40°), when physiological noise considerations permit such an approach, significantly improves accuracy, consistency and stability of registration for data acquired at relatively short TRs (TR≤2s). Moreover, we also show that the application of bias correction techniques significantly improves alignment both for array-coil data (known to contain high intensity inhomogeneity) as well as birdcage-coil data. Finally, improvements in alignment derived from the use of the first infinite-TR volumes (ITVs) as targets for registration are also demonstrated. For the purpose of quantitatively evaluating the different scenarios, two novel metrics were developed: Mean Voxel Distance (MVD) to evaluate registration consistency, and Deviation of Mean Voxel Distance (dMVD) to evaluate registration stability across successive alignment attempts. PMID:23128074

  10. Optimal Phase Masks for High Contrast Imaging Applications

    NASA Astrophysics Data System (ADS)

    Ruane, Garreth J.

    2016-05-01

    Phase-only optical elements can provide a number of important functions for high-contrast imaging. This thesis presents analytical and numerical optical design methods for accomplishing specific tasks, the most significant of which is the precise suppression of light from a distant point source. Instruments designed for this purpose are known as coronagraphs. Here, advanced coronagraph designs are presented that offer improved theoretical performance in comparison to the current state-of-the-art. Applications of these systems include the direct imaging and characterization of exoplanets and circumstellar disks with high sensitivity. Several new coronagraph designs are introduced and, in some cases, experimental support is provided. In addition, two novel high-contrast imaging applications are discussed: the measurement of sub-resolution information using coronagraphic optics and the protection of sensors from laser damage. The former is based on experimental measurements of the sensitivity of a coronagraph to source displacement. The latter discussion presents the current state of ongoing theoretical work. Beyond the mentioned applications, the main outcome of this thesis is a generalized theory for the design of optical systems with one of more phase masks that provide precise control of radiation over a large dynamic range, which is relevant in various high-contrast imaging scenarios. The optimal phase masks depend on the necessary tasks, the maximum number of optics, and application specific performance measures. The challenges and future prospects of this work are discussed in detail.

  11. High Contrast Imaging with the JWST NIRCAM Coronagraph

    NASA Technical Reports Server (NTRS)

    Green, Joseph J.; Beichman, Charles; Basinger, Scott A.; Horner, Scott; Meyer, Michael; Redding, David C.; Rieke, Marcia; Trauger, John T.

    2005-01-01

    Relative to ground-based telescopes, the James Webb Space Telescope (JWST) will have a substantial sensitivity advantage in the 2.2-5pm wavelength range where brown dwarfs and hot Jupiters are thought to have significant brightness enhancements. To facilitate high contrast imaging within this band, the Near-Infrared Camera (NIRCAM) will employ a Lyot coronagraph with an array of band-limited image-plane occulting spots. In this paper, we provide the science motivation for high contrast imaging with NIRCAM, comparing its expected performance to that of the Keck, Gemini and 30 m (TMT) telescopes equipped with Adaptive Optics systems of different capabilities. We then describe our design for the NIRCAM coronagraph that enables imaging over the entire sensitivity range of the instrument while providing significant operational flexibility. We describe the various design tradeoffs that were made in consideration of alignment and aberration sensitivities and present contrast performance in the presence of JWST's expected optical aberrations. Finally we show an example of a that can provide 10-5 companion sensitivity at sub-arcsecond separations.

  12. Cumulative phase delay imaging - A new contrast enhanced ultrasound modality

    SciTech Connect

    Demi, Libertario Sloun, Ruud J. G. van; Mischi, Massimo; Wijkstra, Hessel

    2015-10-28

    Recently, a new acoustic marker for ultrasound contrast agents (UCAs) has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental pressure wave field components is in fact observable for ultrasound propagating through UCAs. This phenomenon is absent in the case of tissue nonlinearity and is dependent on insonating pressure and frequency, UCA concentration, and propagation path length through UCAs. In this paper, ultrasound images based on this marker are presented. The ULA-OP research platform, in combination with a LA332 linear array probe (Esaote, Firenze Italy), were used to image a gelatin phantom containing a PVC plate (used as a reflector) and a cylindrical cavity measuring 7 mm in diameter (placed in between the observation point and the PVC plate). The cavity contained a 240 µL/L SonoVueO{sup ®} UCA concentration. Two insonating frequencies (3 MHz and 2.5 MHz) were used to scan the gelatine phantom. A mechanical index MI = 0.07, measured in water at the cavity location with a HGL-0400 hydrophone (Onda, Sunnyvale, CA), was utilized. Processing the ultrasound signals backscattered from the plate, ultrasound images were generated in a tomographic fashion using the filtered back-projection method. As already observed in previous studies, significantly higher CPD values are measured when imaging at a frequency of 2.5 MHz, as compared to imaging at 3 MHz. In conclusion, these results confirm the applicability of the discussed CPD as a marker for contrast imaging. Comparison with standard contrast-enhanced ultrasound imaging modalities will be the focus of future work.

  13. Cumulative phase delay imaging - A new contrast enhanced ultrasound modality

    NASA Astrophysics Data System (ADS)

    Demi, Libertario; van Sloun, Ruud J. G.; Wijkstra, Hessel; Mischi, Massimo

    2015-10-01

    Recently, a new acoustic marker for ultrasound contrast agents (UCAs) has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental pressure wave field components is in fact observable for ultrasound propagating through UCAs. This phenomenon is absent in the case of tissue nonlinearity and is dependent on insonating pressure and frequency, UCA concentration, and propagation path length through UCAs. In this paper, ultrasound images based on this marker are presented. The ULA-OP research platform, in combination with a LA332 linear array probe (Esaote, Firenze Italy), were used to image a gelatin phantom containing a PVC plate (used as a reflector) and a cylindrical cavity measuring 7 mm in diameter (placed in between the observation point and the PVC plate). The cavity contained a 240 µL/L SonoVueO® UCA concentration. Two insonating frequencies (3 MHz and 2.5 MHz) were used to scan the gelatine phantom. A mechanical index MI = 0.07, measured in water at the cavity location with a HGL-0400 hydrophone (Onda, Sunnyvale, CA), was utilized. Processing the ultrasound signals backscattered from the plate, ultrasound images were generated in a tomographic fashion using the filtered back-projection method. As already observed in previous studies, significantly higher CPD values are measured when imaging at a frequency of 2.5 MHz, as compared to imaging at 3 MHz. In conclusion, these results confirm the applicability of the discussed CPD as a marker for contrast imaging. Comparison with standard contrast-enhanced ultrasound imaging modalities will be the focus of future work.

  14. Signal Increase on Unenhanced T1-Weighted Images in the Rat Brain After Repeated, Extended Doses of Gadolinium-Based Contrast Agents

    PubMed Central

    Jost, Gregor; Lenhard, Diana Constanze; Sieber, Martin Andrew; Lohrke, Jessica; Frenzel, Thomas; Pietsch, Hubertus

    2016-01-01

    Objectives In this prospective preclinical study, we evaluated T1-weighted signal intensity in the deep cerebellar nuclei (CN) and globus pallidus (GP) up to 24 days after repeated administration of linear and macrocyclic gadolinium-based contrast agents (GBCAs) using homologous imaging and evaluation methods as in the recently published retrospective clinical studies. In a second part of the study, cerebrospinal fluid (CSF) spaces were evaluated for contrast enhancement by fluid-attenuated magnetic resonance imaging (MRI). Materials and Methods Sixty adult male Wistar-Han rats were randomly divided into a control and 5 GBCA groups (n = 10 per group). The administered GBCAs were gadodiamide, gadopentetate dimeglumine, and gadobenate dimeglumine (linear GBCAs) as well as gadobutrol and gadoterate meglumine (macrocyclic GBCAs) and saline (control). Over a period of 2 weeks, the animals received 10 intravenous injections at a dose of 2.5 mmol Gd/kg body weight, each on 5 consecutive days per week. Before GBCA administration, as well as 3 and 24 days after the last injection, a whole-brain MRI was performed using a standard T1-weighted 3-dimensional turbo spin echo sequence on a clinical 1.5 T scanner. The ratios of signal intensities in deep CN to pons (CN/Po) and GP to thalamus (GP/Th) were determined. For the evaluation of the CSF spaces, 18 additional rats were randomly divided into 6 groups (n = 3 per group) that received the same GBCAs as in the first part of the study. After MR cisternography for anatomical reference, a fluid-attenuated inversion recovery sequence was performed before and 1 minute after intravenous injection of a dose of 1 mmol Gd/kg body weight GBCA or saline. Results A significantly increased signal intensity ratio of CN/Po was observed 3 and 24 days after the last injection of gadodiamide and gadobenate dimeglumine. No significant changes were observed between the 2 time points. Gadopentetate dimeglumine injection led to a moderately elevated

  15. In-line phase-contrast imaging of a biological specimen using a compact laser-Compton scattering-based x-ray source

    NASA Astrophysics Data System (ADS)

    Ikeura-Sekiguchi, H.; Kuroda, R.; Yasumoto, M.; Toyokawa, H.; Koike, M.; Yamada, K.; Sakai, F.; Mori, K.; Maruyama, K.; Oka, H.; Kimata, T.

    2008-03-01

    Laser-Compton scattering (LCS) x-ray sources have recently attracted much attention for their potential use at local medical facilities because they can produce ultrashort pulsed, high-brilliance, and quasimonochromatic hard x rays with a small source size. The feasibility of in-line phase-contrast imaging for a "thick" biological specimens of rat lumbar vertebrae using the developed compact LCS-X in AIST was investigated for the promotion of clinical imaging. In the higher-quality images, anatomical details of the spinous processes of the vertebrae are more clearly observable than with conventional absorption radiography. The results demonstrate that phase-contrast radiography can be performed using LCS-X.

  16. Adaptive sigmoid function bihistogram equalization for image contrast enhancement

    NASA Astrophysics Data System (ADS)

    Arriaga-Garcia, Edgar F.; Sanchez-Yanez, Raul E.; Ruiz-Pinales, Jose; Garcia-Hernandez, Ma. de Guadalupe

    2015-09-01

    Contrast enhancement plays a key role in a wide range of applications including consumer electronic applications, such as video surveillance, digital cameras, and televisions. The main goal of contrast enhancement is to increase the quality of images. However, most state-of-the-art methods induce different types of distortion such as intensity shift, wash-out, noise, intensity burn-out, and intensity saturation. In addition, in consumer electronics, simple and fast methods are required in order to be implemented in real time. A bihistogram equalization method based on adaptive sigmoid functions is proposed. It consists of splitting the image histogram into two parts that are equalized independently by using adaptive sigmoid functions. In order to preserve the mean brightness of the input image, the parameter of the sigmoid functions is chosen to minimize the absolute mean brightness metric. Experiments on the Berkeley database have shown that the proposed method improves the quality of images and preserves their mean brightness. An application to improve the colorfulness of images is also presented.

  17. Spatial frequency, phase, and the contrast of natural images.

    PubMed

    Bex, Peter J; Makous, Walter

    2002-06-01

    We examined contrast sensitivity and suprathreshold apparent contrast with natural images. The spatial-frequency components within single octaves of the images were removed (notch filtered), their phases were randomized, or the polarity of the images was inverted. Of Michelson contrast, root-mean-square (RMS) contrast, and band-limited contrast, RMS contrast was the best index of detectability. Negative images had lower apparent contrast than their positives. Contrast detection thresholds showed spatial-frequency-dependent elevation following both notch filtering and phase randomization. The peak of the spatial-frequency tuning function was approximately 0.5-2 cycles per degree (c/deg). Suprathreshold contrast matching functions also showed spatial-frequency-dependent contrast loss for both notch-filtered and phase-randomized images. The peak of the spatial-frequency tuning function was approximately 1-3 c/deg. There was no detectable difference between the effects of phase randomization and notch filtering on contrast sensitivity. We argue that these observations are consistent with changes in the activity within spatial-frequency channels caused by the higher-order phase structure of natural images that is responsible for the presence of edges and specularities.

  18. Spatial frequency, phase, and the contrast of natural images

    NASA Astrophysics Data System (ADS)

    Bex, Peter J.; Makous, Walter

    2002-06-01

    We examined contrast sensitivity and suprathreshold apparent contrast with natural images. The spatial-frequency components within single octaves of the images were removed (notch filtered), their phases were randomized, or the polarity of the images was inverted. Of Michelson contrast, root-mean-square (RMS) contrast, and band-limited contrast, RMS contrast was the best index of detectability. Negative images had lower apparent contrast than their positives. Contrast detection thresholds showed spatial-frequency-dependent elevation following both notch filtering and phase randomization. The peak of the spatial-frequency tuning function was approximately 0.5-2 cycles per degree (c/deg). Suprathreshold contrast matching functions also showed spatial-frequency-dependent contrast loss for both notch-filtered and phase-randomized images. The peak of the spatial-frequency tuning function was approximately 1-3 c/deg. There was no detectable difference between the effects of phase randomization and notch filtering on contrast sensitivity. We argue that these observations are consistent with changes in the activity within spatial-frequency channels caused by the higher-order phase structure of natural images that is responsible for the presence of edges and specularities.

  19. High Resolution X-ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2008-06-01

    murine liver. 15. SUBJECT TERMS X-ray, ultrasound, phase contrast, imaging, elastography 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...of the veins in a mouse liver that was excised from an euthanized mouse, fixed in paraformaldehyde and subsequently dried. The vascular tree is...clearly visible in the x-ray image. Contrast agent injections into the portal vein of another mouse liver verified that the veins are imaged and not

  20. Imaging depth and multiple scattering in laser speckle contrast imaging

    PubMed Central

    Davis, Mitchell A.; Kazmi, S. M. Shams; Dunn, Andrew K.

    2014-01-01

    Abstract. Laser speckle contrast imaging (LSCI) is a powerful and simple method for full field imaging of blood flow. However, the depth dependence and the degree of multiple scattering have not been thoroughly investigated. We employ three-dimensional Monte Carlo simulations of photon propagation combined with high resolution vascular anatomy to investigate these two issues. We found that 95% of the detected signal comes from the top 700 μm of tissue. Additionally, we observed that single-intravascular scattering is an accurate description of photon sampling dynamics, but that regions of interest (ROIs) in areas free of obvious surface vessels had fewer intravascular scattering events than ROI over resolved surface vessels. Furthermore, we observed that the local vascular anatomy can strongly affect the depth dependence of LSCI. We performed simulations over a wide range of intravascular and extravascular scattering properties to confirm the applicability of these results to LSCI imaging over a wide range of visible and near-infrared wavelengths. PMID:25089945

  1. Pediatric Brain: Repeated Exposure to Linear Gadolinium-based Contrast Material Is Associated with Increased Signal Intensity at Unenhanced T1-weighted MR Imaging.

    PubMed

    Flood, Thomas F; Stence, Nicholas V; Maloney, John A; Mirsky, David M

    2017-01-01

    Purpose To determine whether repeated exposure of the pediatric brain to a linear gadolinium-based contrast agent (GBCA) is associated with an increase in signal intensity (SI) relative to that in GBCA-naive control subjects at unenhanced T1-weighted magnetic resonance (MR) imaging. Materials and Methods This single-center, retrospective study was approved by the institutional review board and compliant with HIPAA. The authors evaluated 46 pediatric patients who had undergone at least three GBCA-enhanced MR examinations (30 patients for two-group analysis and 16 for pre- and post-GBCA exposure comparisons) and 57 age-matched GBCA-naive control subjects. The SI in the globus pallidus, thalamus, dentate nucleus, and pons was measured at unenhanced T1-weighted MR imaging. Globus pallidus-thalamus and dentate nucleus-pons SI ratios were calculated and compared between groups and relative to total cumulative gadolinium dose, age, sex, and number of and mean time between GBCA-enhanced examinations. Analysis included the Wilcoxon signed rank test, Wilcoxon rank sum test, and Spearman correlation coefficient. Results Patients who underwent multiple GBCA-enhanced examinations had increased SI ratios within the dentate nucleus (mean SI ratio ± standard error of the mean for two-group comparison: 1.007 ± 0.0058 for GBCA-naive group and 1.046 ± 0.0060 for GBCA-exposed group [P < .001]; mean SI ratio for pre- and post-GBCA comparison: 0.995 ± 0.0062 for pre-GBCA group and 1.035 ± 0.0063 for post-GBCA group [P < .001]) but not the globus pallidus (mean SI ratio for two-group comparison: 1.131 ± 0.0070 for GBCA-naive group and 1.014 ± 0.0091 for GBCA-exposed group [P = .21]; mean SI ratio for pre- and post-GBCA comparison: 1.068 ± 0.0094 for pre-GBCA group and 1.093 ± 0.0134 for post-GBCA group [P = .12]). There was a significant correlation between dentate nucleus SI and total cumulative gadolinium dose (r = 0.4; 95% confidence interval [CI]: 0.03, 0.67; P = .03), but

  2. Separation of Gd-humic complexes and Gd-based magnetic resonance imaging contrast agent in river water with QAE-Sephadex A-25 for the fractionation analysis.

    PubMed

    Matsumiya, Hiroaki; Inoue, Hiroto; Hiraide, Masataka

    2014-10-01

    Gadolinium complexed with naturally occurring, negatively charged humic substances (humic and fulvic acids) was collected from 500 mL of sample solution onto a column packed with 150 mg of a strongly basic anion-exchanger (QAE-Sephadex A-25). A Gd-based magnetic resonance imaging contrast agent (diethylenetriamine-N,N,N',N″,N″-pentaacetato aquo gadolinium(III), Gd-DTPA(2-)) was simultaneously collected on the same column. The Gd-DTPA complex was desorbed by anion-exchange with 50mM tetramethylammonium sulfate, leaving the Gd-humic complexes on the column. The Gd-humic complexes were subsequently dissociated with 1M nitric acid to desorb the humic fraction of Gd. The two-step desorption with small volumes of the eluting agents allowed the 100-fold preconcentration for the fractionation analysis of Gd at low ng L(-1) levels by inductively coupled plasma-mass spectrometry (ICP-MS). On the other hand, Gd(III) neither complexed with humic substances nor DTPA, i.e., free species, was not sorbed on the column. The free Gd in the effluent was preconcentrated 100-fold by a conventional solid-phase extraction with an iminodiacetic acid-type chelating resin and determined by ICP-MS. The proposed analytical fractionation method was applied to river water samples.

  3. Solution and solid-state characterization of europium and gadolinium Schiff base complexes and assessment of their potential as contrast agents in magnetic resonance imaging

    SciTech Connect

    Smith, P.H.; Brainard, J.R.; Morris, D.E.; Jarvinen, G.D.; Ryan, R.R. )

    1989-09-13

    Two lanthanide Schiff base macrocyclic complexes, LnAM(OAc){sub 2}Cl{center dot}4H{sub 2}O (Ln = Eu, Gd; HAM - HexaAzaMacrocycle = C{sub 22}H{sub 26}N{sub 6}), have been characterized in view of the potential of the Gd complex as a magnetic resonance imaging (MRI) contrast agent. The relaxivity of GdHAM(OAc){sub 2}Cl was measured at 300 and 20 MHz and is as high as that for the gadolinium aquo ion. The number of coordinated waters, q, was measured by comparison of the luminescent lifetimes of EuHAM(OAc){sub 2}Cl in H{sub 2}O and D{sub 2}O and found to be between three and four. The complex GdHAM(OAc){sub 2}Cl{center dot}4H{sub 2}O was characterized by single-crystal X-ray diffraction. The complex crystallizes in space group P{bar 1} with Z = 2, a = 10.032 (2) {angstrom}, b = 12.765 (2) {angstrom}, c = 13.668 (3) {angstrom}, {alpha} = 69.190{degree} (9){degree}, {beta} = 72.405{degree} (9){degree}, and {gamma} = 74.07{degree} (1){degree}.

  4. Phase Contrast X-ray Imaging of Shuttle Insulating Foam

    NASA Technical Reports Server (NTRS)

    Hu, Zhengwei

    2005-01-01

    X-ray radiation has been widely used for imaging applications since Rontgen first discovered X-rays over a century ago. Its large penetration depth makes it ideal for the nondestructive visualization of internal structure of materials or objects unobtainable otherwise. Currently widely used nondestructive evaluation (NDE) tools-X-ray radiography and tomography are absorption-based, and work well in highly absorbing materials where density or composition variations due to internal structure or defects are high enough to be spatially distinguished in terms of absorption contrast. However, in many cases where materials such as insulating foam are light-weight, the conventional absorption-based X-ray methods for NDE become less effective. Indeed, the low-density shuttle insulating foam used for flight mission poses a great challenge to the standard NDE tools in that the absorption contrast arising from internal defects of such a low- density material is either weak or indistinguishable. In this presentation, the latest progress in phase contrast X-ray imaging of internal defects of insulating foam will be presented and discussed, demonstrating new opportunities to solve challenging issues involved in advanced materials development and processing for space exploration.

  5. Advanced contrast modalities for X-ray radiology: Phase-contrast and dark-field imaging using a grating interferometer.

    PubMed

    Bech, Martin; Jensen, Torben H; Bunk, Oliver; Donath, Tilman; David, Christian; Weitkamp, Timm; Le Duc, Geraldine; Bravin, Alberto; Cloetens, Peter; Pfeiffer, Franz

    2010-01-01

    Here we review our recent progress in the field of X-ray dark-field and phase-contrast imaging using a grating interferometer. We describe the basic imaging principles of grating-based phase-contrast and dark-field radiography and present some exemplary results obtained for simple test objects and biological specimens. Furthermore, we discuss how phase-contrast and dark-field radiography can be combined with the concept of computed tomography, and yield highly detailed three-dimensional insights into biomedical sample. Exemplary results obtained with standard X-ray tube sources and highly brilliant synchrotron sources are presented.

  6. Motion corrected photoacoustic difference imaging of fluorescent contrast agents

    NASA Astrophysics Data System (ADS)

    Märk, Julia; Wagener, Asja; Pönick, Sarah; Grötzinger, Carsten; Zhang, Edward; Laufer, Jan

    2016-03-01

    In fluorophores, such as exogenous dyes and genetically expressed proteins, the excited state lifetime can be modulated using pump-probe excitation at wavelengths corresponding to the absorption and fluorescence spectra. Simultaneous pump-probe pulses induce stimulated emission (SE) which, in turn, modulates the thermalized energy, and hence the photoacoustic (PA) signal amplitude. For time-delayed pulses, by contrast, SE is suppressed. Since this is not observed in endogenous chromophores, the location of the fluorophore can be determined by subtracting images acquired using simultaneous and time-delayed pump-probe excitation. This simple experimental approach exploits a fluorophorespecific contrast mechanism, and has the potential to enable deep-tissue molecular imaging at fluences below the MPE. In this study, some of the challenges to its in vivo implementation are addressed. First, the PA signal amplitude generated in fluorophores in vivo is often much smaller than that in blood. Second, tissue motion can give rise to artifacts that correspond to endogenous chromophores in the difference image. This would not allow the unambiguous detection of fluorophores. A method to suppress motion artifacts based on fast switching between simultaneous and time-delayed pump-probe excitation was developed. This enables the acquisition of PA signals using the two excitation modes with minimal time delay (20 ms), thus minimizing the effects of tissue motion. The feasibility of this method is demonstrated by visualizing a fluorophore (Atto680) in tissue phantoms, which were moved during the image acquisition to mimic tissue motion.

  7. New imaging technology: measurement of myocardial perfusion by contrast echocardiography

    NASA Technical Reports Server (NTRS)

    Rubin, D. N.; Thomas, J. D.

    2000-01-01

    Myocardial perfusion imaging has long been a goal for the non-invasive echocardiographic assessment of the heart. However, many factors at play in perfusion imaging have made this goal elusive. Harmonic imaging and triggered imaging with newer contrast agents have made myocardial perfusion imaging potentially practical in the very near future. The application of indicator dilution theory to the coronary circulation and bubble contrast agents is fraught with complexities and sources of error. Therefore, quantification of myocardial perfusion by non-invasive echocardiographic imaging requires further investigation in order to make this technique clinically viable.

  8. Diffraction enhance x-ray imaging for quantitative phase contrast studies

    NASA Astrophysics Data System (ADS)

    Agrawal, A. K.; Singh, B.; Kashyap, Y. S.; Shukla, Mayank; Sarkar, P. S.; Sinha, Amar

    2016-05-01

    Conventional X-ray imaging based on absorption contrast permits limited visibility of feature having small density and thickness variations. For imaging of weakly absorbing material or materials possessing similar densities, a novel phase contrast imaging techniques called diffraction enhanced imaging has been designed and developed at imaging beamline Indus-2 RRCAT Indore. The technique provides improved visibility of the interfaces and show high contrast in the image forsmall density or thickness gradients in the bulk. This paper presents basic principle, instrumentation and analysis methods for this technique. Initial results of quantitative phase retrieval carried out on various samples have also been presented.

  9. Contrast-enhanced imaging of cerebral vasculature with laser speckle

    NASA Astrophysics Data System (ADS)

    Murari, K.; Li, N.; Rege, A.; Jia, X.; All, A.; Thakor, N.

    2007-08-01

    High-resolution cerebral vasculature imaging has applications ranging from intraoperative procedures to basic neuroscience research. Laser speckle, with spatial contrast processing, has recently been used to map cerebral blood flow. We present an application of the technique using temporal contrast processing to image cerebral vascular structures with a field of view a few millimeters across and approximately 20 μm resolution through a thinned skull. We validate the images using fluorescent imaging and demonstrate a factor of 2-4 enhancement in contrast-to-noise ratios over reflectance imaging using white or spectrally filtered green light. The contrast enhancement enables the perception of approximately 10%-30% more vascular structures without the introduction of any contrast agent.

  10. Magnetic field induced differential neutron phase contrast imaging

    SciTech Connect

    Strobl, M.; Treimer, W.; Walter, P.; Keil, S.; Manke, I.

    2007-12-17

    Besides the attenuation of a neutron beam penetrating an object, induced phase changes have been utilized to provide contrast in neutron and x-ray imaging. In analogy to differential phase contrast imaging of bulk samples, the refraction of neutrons by magnetic fields yields image contrast. Here, it will be reported how double crystal setups can provide quantitative tomographic images of magnetic fields. The use of magnetic air prisms adequate to split the neutron spin states enables a distinction of field induced phase shifts and these introduced by interaction with matter.

  11. Does bicarbonate prevent contrast-induced nephropathy in cardiovascular patients undergoing contrast imaging?

    PubMed

    Dabare, Dilan; Banihani, Mohammed; Gibbs, Paul; Grewal, Perbinder

    2013-12-01

    A best evidence topic in cardiovascular surgery was written according to a structured protocol. The question addressed was whether administering sodium bicarbonate (NaHCO3) prevents contrast-induced nephropathy (CIN) in cardiovascular patients undergoing contrast imaging. In total, 266 papers were found using the reported search, 16 of which represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. CIN is thought to occur as a result of ischaemic or oxidative injury to the kidney. It is postulated that NaHCO3attenuates this renal damage by alkanizing renal tubular fluid thus reducing the generation of contrast-induced free radicals, which damage the kidney. Of the 16 trials, 15 recruited patients with various degrees of renal dysfunction at baseline. The benefit of using NaHCO3 was demonstrated at all stages of chronic kidney disease. Apart from four studies, 12 studies used low toxicity, low-osmolar contrast. Merten et al. published the first trial of NaHCO3 vs (saline) NaCl in preventing CIN, demonstrated a significantly lower rate in the NaHCO3 group and advocated its widespread use. Subsequent trials using the same regimen have collaborated these results. However, more recently, Gomes et al. concluded that NaHCO3 is not superior to saline-based hydration. Similarly, Brar et al. randomized 323 patients with moderate-to-severe renal insufficiency to receive either an NaHCO3 or an NaCl infusion and observed no difference in CIN rates. Two studies investigated the effects of rapid urine alkanization with bolus injections of NaHCO3 prior to contrast and found significant reductions in CIN rates compared with NaCl-treated groups. One study observed that NaCl is superior to NaHCO3, while all other studies showed a beneficial effect or no difference between NaCl- and NaHCO3-based hydration. The most recent meta

  12. Photo-magnetic Imaging: Resolving Optical Contrast at MRI resolution

    PubMed Central

    Lin, Yuting; Gao, Hao; Thayer, David; Luk, Alex L.; Gulsen, Gultekin

    2014-01-01

    In this paper, we establish the mathematical framework of a novel imaging technique, namely Photo-magnetic Imaging (PMI). PMI uses laser to illuminate biological tissues and measure the induced temperature variations using magnetic resonance imaging (MRI). PMI overcomes the limitation of conventional optical imaging and allows imaging of optical contrast at MRI spatial resolution. The image reconstruction for PMI, using a finite element-based algorithm with iterative approach, is presented in this paper. The quantitative accuracy of PMI is investigated for various inclusion sizes, depths and absorption values. Then, a comparison between conventional Diffuse Optical Tomography (DOT) and PMI is carried out to illustrate the superior performance of PMI. An example is presented showing that two 2 mm diameter inclusions embedded 4.5 mm deep and located side by side in a 25 mm diameter circular geometry medium is recovered as a single 6 mm diameter object with DOT. However, these two objects are not only effectively resolved with PMI, but their true concentration are also recovered successfully. PMID:23640084

  13. Quantitative analysis of contrast to noise ratio using a phase contrast x-ray imaging prototype

    NASA Astrophysics Data System (ADS)

    Ghani, Muhammad U.; Wu, Di; Li, Yuhua; Kang, Minhua; Chen, Wei R.; Wu, Xizeng; Liu, Hong

    2013-02-01

    The purpose of this study was to determine the Contrast to Noise Ratio (CNR) of the x-ray images taken with the phase contrast imaging mode and compare them with the CNR of the images taken under the conventional mode. For each mode, three images were taken under three exposure conditions of 100 kVp (2.8mAs), 120 kVp (1.9mAs) and 140kVp (1.42mAs). A 1.61cm thick contrast detail phantom was used as an imaging object. For phase contrast, the source to image detector distance (SID) was 182.88 cm and the source to object (SOD) distance was 73.15 cm. The SOD was the same as SID in the conventional imaging mode. A computed radiography (CR) plate was used as a detector and the output CR images were converted to linear form in relation with the incident x-ray exposure. To calculate CNR, an image processing software was used to determine the mean pixel value and the standard deviation of the pixels in the region of interest (ROI) and in the nearby background around ROI. At any given exposure condition investigated in this study, the CNR values for the phase contrast images were better as compared to the corresponding conventional mode images. The superior image quality in terms of CNR is contributed by the phase-shifts resulted contrast, as well as the reduced scatters due to the air gap between the object and the detector.

  14. Contrast enhancement via texture region based histogram equalization

    NASA Astrophysics Data System (ADS)

    Singh, Kuldeep; Vishwakarma, Dinesh K.; Singh Walia, Gurjit; Kapoor, Rajiv

    2016-08-01

    This paper presents two novel contrast enhancement approaches using texture regions-based histogram equalization (HE). In HE-based contrast enhancement methods, the enhanced image often contains undesirable artefacts because an excessive number of pixels in the non-textured areas heavily bias the histogram. The novel idea presented in this paper is to suppress the impact of pixels in non-textured areas and to exploit texture features for the computation of histogram in the process of HE. The first algorithm named as Dominant Orientation-based Texture Histogram Equalization (DOTHE), constructs the histogram of the image using only those image patches having dominant orientation. DOTHE categories image patches into smooth, dominant or non-dominant orientation patches by using the image variance and singular value decomposition algorithm and utilizes only dominant orientation patches in the process of HE. The second method termed as Edge-based Texture Histogram Equalization, calculates significant edges in the image and constructs the histogram using the grey levels present in the neighbourhood of edges. The cumulative density function of the histogram formed from texture features is mapped on the entire dynamic range of the input image to produce the contrast-enhanced image. Subjective as well as objective performance assessment of proposed methods is conducted and compared with other existing HE methods. The performance assessment in terms of visual quality, contrast improvement index, entropy and measure of enhancement reveals that the proposed methods outperform the existing HE methods.

  15. Color Contrast Metrics for Complex Images

    DTIC Science & Technology

    1986-09-01

    viewer who is focused at infinity sees an image of the outside world with 4 the computer-generated imagery " watercolored " upon it. The reader has...raster is 2:1 positively interlaced and paints a complete image once every 1/30 s. The aspect ratio was adjusted to 1:1, yielding a (26 cm)2 -live...required approximately 5 s. Presentation of the HUDBACKs to subjects was synchronized with the monitor’s raster so that they were always painted

  16. A Lipopeptide-Based αvβ₃ Integrin-Targeted Ultrasound Contrast Agent for Molecular Imaging of Tumor Angiogenesis.

    PubMed

    Yan, Fei; Xu, Xiuxia; Chen, Yihan; Deng, Zhiting; Liu, Hongmei; Xu, Jianrong; Zhou, Jie; Tan, Guanghong; Wu, Junru; Zheng, Hairong

    2015-10-01

    The design and fabrication of targeted ultrasound contrast agents are key factors in the success of ultrasound molecular imaging applications. Here, we introduce a transformable αvβ3 integrin-targeted microbubble (MB) by incorporation of iRGD-lipopeptides into the MB membrane for non-invasive ultrasound imaging of tumor angiogenesis. First, the iRGD-lipopeptides were synthesized by conjugating iRGD peptides to distearoylphosphatidylethanolamine-polyethylene glycol 2000-maleimide. The resulting iRGD-lipopeptides were used for fabrication of the iRGD-carrying αvβ3 integrin-targeted MBs (iRGD-MBs). The binding specificity of iRGD-MBs for endothelial cells was found to be significantly stronger than that of control MBs (p < 0.01) under in vitro static and dynamic conditions. The binding of iRGD-MBs on the endothelial cells was competed off by pre-incubation with the anti-αv or anti-β3 antibody (p < 0.01). Ultrasound images taken of mice bearing 4T1 breast tumors after intravenous injections of iRGD-MBs or control MBs revealed strong contrast enhancement within the tumors from iRGD-MBs but not from the control MBs; the mean acoustic signal intensity was 10.71 ± 2.75 intensity units for iRGD-MBs versus 1.13 ± 0.18 intensity units for the control MBs (p < 0.01). The presence of αvβ3 integrin was confirmed by immunofluorescence staining. These data indicate that iRGD-MBs can be used as an ultrasound imaging probe for the non-invasive molecular imaging of tumor angiogenesis, and may have further implications for ultrasound image-guided tumor targeting drug delivery.

  17. X-ray refraction-contrast computed tomography images using dark-field imaging optics

    SciTech Connect

    Sunaguchi, Naoki; Yuasa, Tetsuya; Huo, Qingkai; Ichihara, Shu; Ando, Masami

    2010-10-11

    If an x-ray beam containing internal information derived from sample soft tissue is incident upon a Laue-case analyzer, the beam will subsequently split into a forwardly diffracted beam and a separate diffracted beam. Using these beams acquired simultaneously, a refraction-contrast computed tomography (CT) imaging system for biomedical use with lower radiation dose can be easily realized, and has a high depicting capability on the soft tissues compared with conventional x-ray CT based on absorption contrast principles. In this paper, we propose an imaging system using dark-field imaging for CT measurement based on a tandem system of Bragg- and Laue-case crystals with two two-dimensional detectors, along with a data-processing method to extract information on refraction from the measured entangled intensities by use of rocking curve fitting with polynomial functions. Reconstructed images of soft tissues are presented and described.

  18. Manganese-based MRI contrast agents: past, present and future

    PubMed Central

    Pan, Dipanjan; Schmieder, Anne H.; Wickline, Samuel A.; Lanza, Gregory M.

    2011-01-01

    Paramagnetic and superparamagnetic metals are used as contrast materials for magnetic resonance (MR) based techniques. Lanthanide metal gadolinium (Gd) has been the most widely explored, predominant paramagnetic contrast agent until the discovery and association of the metal with nephrogenic systemic fibrosis (NSF), a rare but serious side effects in patients with renal or kidney problems. Manganese was one of the earliest reported examples of paramagnetic contrast material for MRI because of its efficient positive contrast enhancement. In this review, manganese based contrast agent approaches are discussed with a particular emphasis on their synthetic approaches. Both small molecules based typical blood pool contrast agents and more recently developed novel nanometer sized materials are reviewed focusing on a number of successful molecular imaging examples. PMID:22043109

  19. Global and Regional Brain Assessment with Quantitative MR Imaging in Patients with Prior Exposure to Linear Gadolinium-based Contrast Agents.

    PubMed

    Kuno, Hirofumi; Jara, Hernán; Buch, Karen; Qureshi, Muhammad Mustafa; Chapman, Margaret N; Sakai, Osamu

    2017-04-01

    Purpose To assess the association of global and regional brain relaxation times in patients with prior exposure to linear gadolinium-based contrast agents (GBCAs). Materials and Methods The institutional review board approved this cross-sectional study. Thirty-five patients (nine who had received GBCA gadopentetate dimeglumine injections previously [one to eight times] and 26 patients who did not) who underwent brain magnetic resonance (MR) imaging with a mixed fast spin-echo pulse sequence were assessed. The whole brain was segmented according to white and gray matter by using a dual-clustering algorithm. In addition, regions of interest were measured in the globus pallidus, dentate nucleus, thalamus, and pons. The Mann-Whitney U test was used to assess the difference between groups. Multiple regression analysis was performed to assess the association of T1 and T2 with prior GBCA exposure. Results T1 values of gray matter were significantly shorter for patients with than for patients without prior GBCA exposure (P = .022). T1 of the gray matter of the whole brain (P < .001), globus pallidus (P = .002), dentate nucleus (P = .046), and thalamus (P = .026) and T2 of the whole brain (P = .004), dentate nucleus (P = .023), and thalamus (P = .002) showed a significant correlation with the accumulated dose of previous GBCA administration. There was no significant correlation between T1 and the accumulated dose of previous GBCA injections in the white matter (P = .187). Conclusion Global and regional quantitative assessments of T1 and T2 demonstrated an association with prior GBCA exposure, especially for gray matter structures. The results of this study confirm previous research findings that there is gadolinium deposition in wider distribution throughout the brain. (©) RSNA, 2016 Online supplemental material is available for this article.

  20. Contrast Enhancement Algorithm Based on Gap Adjustment for Histogram Equalization

    PubMed Central

    Chiu, Chung-Cheng; Ting, Chih-Chung

    2016-01-01

    Image enhancement methods have been widely used to improve the visual effects of images. Owing to its simplicity and effectiveness histogram equalization (HE) is one of the methods used for enhancing image contrast. However, HE may result in over-enhancement and feature loss problems that lead to unnatural look and loss of details in the processed images. Researchers have proposed various HE-based methods to solve the over-enhancement problem; however, they have largely ignored the feature loss problem. Therefore, a contrast enhancement algorithm based on gap adjustment for histogram equalization (CegaHE) is proposed. It refers to a visual contrast enhancement algorithm based on histogram equalization (VCEA), which generates visually pleasing enhanced images, and improves the enhancement effects of VCEA. CegaHE adjusts the gaps between two gray values based on the adjustment equation, which takes the properties of human visual perception into consideration, to solve the over-enhancement problem. Besides, it also alleviates the feature loss problem and further enhances the textures in the dark regions of the images to improve the quality of the processed images for human visual perception. Experimental results demonstrate that CegaHE is a reliable method for contrast enhancement and that it significantly outperforms VCEA and other methods. PMID:27338412

  1. Intravascular contrast agents suitable for magnetic resonance imaging. [Dogs

    SciTech Connect

    Runge, V.M.; Clanton, J.A.; Herzer, W.A.; Gibbs, S.J.; Price, A.C.; Partain, C.L.; James, A.E. Jr.

    1984-10-01

    Two paramagnetic chelates, chromium EDTA and gadolinium DTPA, were evaluated as potential intravenous contrast agents for magnetic resonance imaging. After evaluating both agents in vitro, in vivo studies were conducted in dogs to document changes in renal appearance produced by contrast injection. Acute splenic and renal infarction were diagnosed with contrast-enhanced MR and confirmed by gamma camera imaging following administration of Tc-99m-labeled DMSA and sulfur colloid. The authors conclude that intravenous paramagnetic contrast agents presently offer the best mechanism for assessment of tissue function and changes in perfusion with MR.

  2. Whole-cell phase contrast imaging at the nanoscale using Fresnel Coherent Diffractive Imaging Tomography

    PubMed Central

    Jones, Michael W. M.; van Riessen, Grant A.; Abbey, Brian; Putkunz, Corey T.; Junker, Mark D.; Balaur, Eugeniu; Vine, David J.; McNulty, Ian; Chen, Bo; Arhatari, Benedicta D.; Frankland, Sarah; Nugent, Keith A.; Tilley, Leann; Peele, Andrew G.

    2013-01-01

    X-ray tomography can provide structural information of whole cells in close to their native state. Radiation-induced damage, however, imposes a practical limit to image resolution, and as such, a choice between damage, image contrast, and image resolution must be made. New coherent diffractive imaging techniques, such Fresnel Coherent Diffractive Imaging (FCDI), allows quantitative phase information with exceptional dose efficiency, high contrast, and nano-scale resolution. Here we present three-dimensional quantitative images of a whole eukaryotic cell by FCDI at a spatial resolution below 70 nm with sufficient phase contrast to distinguish major cellular components. From our data, we estimate that the minimum dose required for a similar resolution is close to that predicted by the Rose criterion, considerably below accepted estimates of the maximum dose a frozen-hydrated cell can tolerate. Based on the dose efficiency, contrast, and resolution achieved, we expect this technique will find immediate applications in tomographic cellular characterisation. PMID:23887204

  3. Laboratory test of a polarimetry imaging subtraction system for the high-contrast imaging

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Li, Rong

    2012-09-01

    We propose a polarimetry imaging subtraction test system that can be used for the direct imaging of the reflected light from exoplanets. Such a system will be able to remove the speckle noise scattered by the wave-front error and thus can enhance the high-contrast imaging. In this system, we use a Wollaston Prism (WP) to divide the incoming light into two simultaneous images with perpendicular linear polarizations. One of the images is used as the reference image. Then both the phase and geometric distortion corrections have been performed on the other image. The corrected image is subtracted with the reference image to remove the speckles. The whole procedure is based on an optimization algorithm and the target function is to minimize the residual speckles after subtraction. For demonstration purpose, here we only use a circular pupil in the test without integrating of our apodized-pupil coronagraph. It is shown that best result can be gained by inducing both phase and distortion corrections. Finally, it has reached an extra contrast gain of 50-times improvement in average, which is promising to be used for the direct imaging of exoplanets.

  4. Endoluminal contrast for abdomen and pelvis magnetic resonance imaging.

    PubMed

    Gupta, Mohit K; Khatri, Gaurav; Bailey, April; Pinho, Daniella F; Costa, Daniel; Pedrosa, Ivan

    2016-07-01

    Magnetic resonance (MR) imaging of the abdomen and pelvis can be limited for assessment of different conditions when imaging inadequately distended hollow organs. Endoluminal contrast agents may provide improved anatomic definition and detection of subtle pathology in such scenarios. The available routes of administration for endoluminal contrast agents include oral, endorectal, endovaginal, intravesicular, and through non-physiologic accesses. Appropriate use of endoluminal contrast agents requires a thorough understanding of the clinical indications, available contrast agents, patient preparation, and interaction of the contrast agent with the desired MR imaging protocol. For example, biphasic oral enteric contrast agents are preferred in MR enterography as their signal properties on T1- and T2-weighted imaging allow for evaluation of both intraluminal and bowel wall pathology. In specific situations such as with MR enterography, MR defecography, and accurate local staging of certain pelvic tumors, the use of an endoluminal contrast agent is imperative in providing adequate diagnostic imaging. In other clinical scenarios, the use of an endoluminal contrast agent may serve as an indispensable problem-solving tool.

  5. Quantitative analysis of shape and volume changes in activated thrombocytes in real time by single-shot spatial light modulator-based differential interference contrast imaging.

    PubMed

    Khan, Saranjam; Jesacher, Alexander; Nussbaumer, Walter; Bernet, Stefan; Ritsch-Marte, Monika

    2011-09-01

    We suggest to use a combination of optical tweezers and single-image quantitative differential interference contrast (DIC) emulated by a spatial light modulator (SLM) to study physiological shape changes in thrombocytes after activation and demonstrate the effectiveness of this system for the given task. A specially designed phase mask displayed at the SLM enables quantitative phase calculation from only a single recording. The optical tweezers stabilize trapped thrombocytes for long-time monitoring of changes in the optical thickness profile of thrombocytes during activation by adenosine diphosphate (ADP).

  6. Design, synthesis and evaluation of a new Mn - Contrast agent for MR imaging of myocardium based on the DTPA-phenylpentadecanoic acid complex

    NASA Astrophysics Data System (ADS)

    Belyanin, Maxim L.; Stepanova, Elena V.; Valiev, Rashid R.; Filimonov, Victor D.; Usov, Vladimir Y.; Borodin, Oleg Y.; Ågren, Hans

    2016-11-01

    In the present paper we describe the first synthesis and evaluation of a novel Mn (II) complex (DTPA-PPDA Mn (II)) which contains a C-15 fatty acid moiety that has high affinity to the heart muscle. The complexation energy of DTPA-PPDA Mn (II) evaluated by quantum chemistry methodology indicates that it essentially exceeds the corresponding value for the known DTPA Mn (II) complex. Molecular docking revealed that the affinity of the designed complex to the heart-type transport protein H-FABP well exceeds that of lauric acid. Phantom experiments in low-field MRI the designed contrast agent provides MR imaging comparable to gadopentetic acid.

  7. Motility Contrast Imaging and Tissue Dynamics Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nolte, David D.; An, Ran; Turek, John

    Motion is the defining physiological characteristic of living matter. If we are interested in how things function, then the way they move is most informative. Motion provides an endogenous and functional suite of biomarkers that are sensitive to subtle changes that occur under applied pharmacological doses or cellular stresses. This chapter reviews the application of biodynamic imaging to measure cellular dynamics in three-dimensional tissue culture for drug screening applications. Nanoscale and microscale motions are detected through statistical fluctuations in dynamic speckle across an ensemble of cells within each resolution voxel. Tissue dynamics spectroscopy generates drug-response spectrograms that serve as phenotypic fingerprints of drug action and can differentiate responses from heterogeneous regions of tumor tissue.

  8. Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast

    PubMed Central

    Ananta, Jeyarama S.; Godin, Biana; Sethi, Richa; Moriggi, Loick; Liu, Xuewu; Serda, Rita E.; Krishnamurthy, Ramkumar; Muthupillai, Raja; Bolskar, Robert D.; Helm, Lothar; Ferrari, Mauro; Wilson, Lon J.; Decuzzi, Paolo

    2010-01-01

    Magnetic resonance imaging contrast agents are currently designed by modifying their structural and physiochemical properties in order to improve relaxivity and to enhance image contrast. Here we show a general method for increasing relaxivity by confining contrast agents inside the nanoporous structure of silicon particles. Magnevist, gadofullerenes and gadonanotubes were loaded inside the pores of quasi-hemispherical and discoidal particles. For all combinations of nanoconstructs, a boost in longitudinal proton relaxivity r1 was observed: for Magnevist, r1~14 mM-1s-1/Gd3+ion (~8.15×10+7 mM-1s-1/construct); for gadofullerenes, r1~200 mM-1s-1/Gd3+ion (~7×10+9 mM-1s-1/construct); for gadonanotubes, r1~150 mM-1s-1/Gd3+ion (~2×10+9 mM-1s-1/construct). These relaxivity values are about 4 to 50 times larger than that of clinically-available gadolinium-based agents (~4 mM-1s-1 /Gd3+ion). The enhancement in contrast is attributed to the geometrical confinement of the agents, which influences the paramagnetic behavior of the Gd3+ions. Thus, nanoscale confinement offers a new and general strategy for enhancing the contrast of gadolinium-based contrast agents. PMID:20972435

  9. Molecular Optical Coherence Tomography Contrast Enhancement and Imaging

    NASA Astrophysics Data System (ADS)

    Oldenburg, Amy L.; Applegate, Brian E.; Tucker-Schwartz, Jason M.; Skala, Melissa C.; Kim, Jongsik; Boppart, Stephen A.

    Histochemistry began as early as the nineteenth century, with the development of synthetic dyes that provided spatially mapped chemical contrast in tissue [1]. Stains such as hematoxylin and eosin, which contrast cellular nuclei and cytoplasm, greatly aid in the interpretation of microscopy images. An analogous development is currently taking place in biomedical imaging, whereby techniques adapted for MRI, CT, and PET now provide in vivo molecular imaging over the entire human body, aiding in both fundamental research discovery and in clinical diagnosis and treatment monitoring. Because OCT offers a unique spatial scale that is intermediate between microscopy and whole-body biomedical imaging, molecular contrast OCT (MCOCT) also has great potential for providing new insight into in vivo molecular processes. The strength of MCOCT lies in its ability to isolate signals from a molecule or contrast agent from the tissue scattering background over large scan areas at depths greater than traditional microscopy techniques while maintaining high resolution.

  10. Contrast agents for photoacoustic and thermoacoustic imaging: a review.

    PubMed

    Wu, Dan; Huang, Lin; Jiang, Max S; Jiang, Huabei

    2014-12-18

    Photoacoustic imaging (PAI) and thermoacoustic imaging (TAI) are two emerging biomedical imaging techniques that both utilize ultrasonic signals as an information carrier. Unique advantages of PAI and TAI are their abilities to provide high resolution functional information such as hemoglobin and blood oxygenation and tissue dielectric properties relevant to physiology and pathology. These two methods, however, may have a limited detection depth and lack of endogenous contrast. An exogenous contrast agent is often needed to effectively resolve these problems. Such agents are able to greatly enhance the imaging contrast and potentially break through the imaging depth limit. Furthermore, a receptor-targeted contrast agent could trace the molecular and cellular biological processes in tissues. Thus, photoacoustic and thermoacoustic molecular imaging can be outstanding tools for early diagnosis, precise lesion localization, and molecular typing of various diseases. The agents also could be used for therapy in conjugation with drugs or in photothermal therapy, where it functions as an enhancer for the integration of diagnosis and therapy. In this article, we present a detailed review about various exogenous contrast agents for photoacoustic and thermoacoustic molecular imaging. In addition, challenges and future directions of photoacoustic and thermoacoustic molecular imaging in the field of translational medicine are also discussed.

  11. Usefulness of ultrasound contrast for image enhancement during stress echocardiography.

    PubMed

    Ten Cate, Folkert J

    2002-10-01

    Although stress echocardiography has been established as a diagnostic technique for the detection and assessment of ischemia, there are still a number of limitations to the technique. These are related to suboptimal image quality with poor visualization of endocardial borders. Because assessment of wall motion is fundamental to the diagnostic value of stress echocardiography (both pharmacologic and exercise), endocardial border visualization is of utmost importance. Furthermore, interinstitutional observer agreement of 100% in highest image quality patients to a cumbersome 43% in low image quality patients is present. Therefore, improvements of image quality during stress are essential. One of the recent improvements is harmonic imaging, which improves visualization of endocardial borders at rest and during dobutamine stress. However, there is room for improvement. Since the introduction of ultrasound contrast agents, contrast has been increasingly used for better endocardial border visualization. Data from centers with a large number of stress echocardiography tests have shown that the addition of contrast agents decreases the number of more redundant diagnostic testing. Data obtained in our center in a subset of patients administered with SonoVue, a new generation contrast agent made of stabilized microbubbles containing sulfur hexafluoride, an inert gas, showed an improvement in the number of evaluable segments with fundamental and harmonic imaging and in the endocardial border detection during dobutamine stress echocardiography. Contrast also enables future quantitative analysis using acoustic quantification (AQ), and color kinesis. These studies should be carried out now that contrast has been approved for introduction to the market.

  12. Pyogenic liver abscess: contrast-enhanced MR imaging in rats.

    PubMed

    Weissleder, R; Saini, S; Stark, D D; Elizondo, G; Compton, C; Wittenberg, J; Ferrucci, J T

    1988-01-01

    MR imaging was used to evaluate experimentally induced pyogenic liver abscesses in an animal model. Rats were examined before and after IV administration of either gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), ferrite particles, or both contrast agents together. Pyogenic liver abscesses appeared hypointense on T1-weighted images and hyperintense on T2-weighted images. Bolus administration of Gd-DTPA using a fast spin-echo sequence with repetition time of 250 msec and echo time of 20 msec (SE 250/20) showed transient selective enhancement of normal hepatic tissue and increased lesion conspicuity, quantitatively assessed by the contrast-to-noise ratio, which increased from -35.7 to -59.0. Delayed leakage of Gd-DTPA into the abscess center partially obscured small lesions at 30-60 min. Ferrite particles reduced the signal intensity of normal liver, and the abscess then appeared homogenously hyperintense. Applying the SE 500/32 sequence, the contrast-to-noise ratio increased from -1.2 to +74.0. Coordinated administration of both contrast agents showed a further increase in contrast to +94.0, with a hyperintense abscess rim surrounded by hypointense liver. Gd-DTPA increases abscess-liver contrast by rim enhancement of the abscess wall, and ferrite increases the abscess-liver contrast by selectively decreasing the signal intensity of surrounding normal liver. As a result of increased contrast-to-noise ratio, both contrast agents, alone or in combination, increase the conspicuity of hepatic abscesses.

  13. "Multimodal Contrast" from the Multivariate Analysis of Hyperspectral CARS Images

    NASA Astrophysics Data System (ADS)

    Tabarangao, Joel T.

    The typical contrast mechanism employed in multimodal CARS microscopy involves the use of other nonlinear imaging modalities such as two-photon excitation fluorescence (TPEF) microscopy and second harmonic generation (SHG) microscopy to produce a molecule-specific pseudocolor image. In this work, I explore the use of unsupervised multivariate statistical analysis tools such as Principal Component Analysis (PCA) and Vertex Component Analysis (VCA) to provide better contrast using the hyperspectral CARS data alone. Using simulated CARS images, I investigate the effects of the quadratic dependence of CARS signal on concentration on the pixel clustering and classification and I find that a normalization step is necessary to improve pixel color assignment. Using an atherosclerotic rabbit aorta test image, I show that the VCA algorithm provides pseudocolor contrast that is comparable to multimodal imaging, thus showing that much of the information gleaned from a multimodal approach can be sufficiently extracted from the CARS hyperspectral stack itself.

  14. Phase contrast image segmentation using a Laue analyser crystal

    NASA Astrophysics Data System (ADS)

    Kitchen, Marcus J.; Paganin, David M.; Uesugi, Kentaro; Allison, Beth J.; Lewis, Robert A.; Hooper, Stuart B.; Pavlov, Konstantin M.

    2011-02-01

    Dual-energy x-ray imaging is a powerful tool enabling two-component samples to be separated into their constituent objects from two-dimensional images. Phase contrast x-ray imaging can render the boundaries between media of differing refractive indices visible, despite them having similar attenuation properties; this is important for imaging biological soft tissues. We have used a Laue analyser crystal and a monochromatic x-ray source to combine the benefits of both techniques. The Laue analyser creates two distinct phase contrast images that can be simultaneously acquired on a high-resolution detector. These images can be combined to separate the effects of x-ray phase, absorption and scattering and, using the known complex refractive indices of the sample, to quantitatively segment its component materials. We have successfully validated this phase contrast image segmentation (PCIS) using a two-component phantom, containing an iodinated contrast agent, and have also separated the lungs and ribcage in images of a mouse thorax. Simultaneous image acquisition has enabled us to perform functional segmentation of the mouse thorax throughout the respiratory cycle during mechanical ventilation.

  15. Harmonic chirp imaging method for ultrasound contrast agent.

    PubMed

    Borsboom, Jerome M G; Chin, Chien Ting; Bouakaz, Ayache; Versluis, Michel; de Jong, Nico

    2005-02-01

    Coded excitation is currently used in medical ultrasound to increase signal-to-noise ratio (SNR) and penetration depth. We propose a chirp excitation method for contrast agents using the second harmonic component of the response. This method is based on a compression filter that selectively compresses and extracts the second harmonic component from the received echo signal. Simulations have shown a clear increase in response for chirp excitation over pulse excitation with the same peak amplitude. This was confirmed by two-dimensional (2-D) optical observations of bubble response with a fast framing camera. To evaluate the harmonic compression method, we applied it to simulated bubble echoes, to measured propagation harmonics, and to B-mode scans of a flow phantom and compared it to regular pulse excitation imaging. An increase of approximately 10 dB in SNR was found for chirp excitation. The compression method was found to perform well in terms of resolution. Axial resolution was in all cases within 10% of the axial resolution from pulse excitation. Range side-lobe levels were 30 dB below the main lobe for the simulated bubble echoes and measured propagation harmonics. However, side-lobes were visible in the B-mode contrast images.

  16. SNR and Contrast Enhancement Techniques for the Photoacoustic Radar Imaging

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Mandelis, Andreas

    2016-07-01

    This paper presents two methods for photoacoustic signal enhancement in biological tissues. One such method is based on the fact that temperature can affect the signals of the photoacoustic radar. Therefore, thermally assisted methods have been used for photoacoustic imaging contrast improvement. Another method is based on harmonic wavelength modulation which results in a differential PA radar signal to strengthen early cancer detection. Two chirped waveforms modulated out-of-phase between 680 nm and 800 nm can effectively suppress the background noise, greatly enhance the SNR and detect small variations in hemoglobin oxygenation levels, thereby distinguishing pre-malignant tumors. Experimental results demonstrate the accuracy of the frequency-modulated differential measurement with sheep blood at different hemoglobin oxygenation (S_tO2) levels.

  17. X-ray elastography: Modification of x-ray phase contrast images using ultrasonic radiation pressure

    SciTech Connect

    Hamilton, Theron J.; Bailat, Claude; Rose-Petruck, Christoph; Diebold, Gerald J.; Gehring, Stephan; Laperle, Christopher M.; Wands, Jack

    2009-05-15

    The high resolution characteristic of in-line x-ray phase contrast imaging can be used in conjunction with directed ultrasound to detect small displacements in soft tissue generated by differential acoustic radiation pressure. The imaging method is based on subtraction of two x-ray images, the first image taken with, and the second taken without the presence of ultrasound. The subtraction enhances phase contrast features and, to a large extent, removes absorption contrast so that differential movement of tissues with different acoustic impedances or relative ultrasonic absorption is highlighted in the image. Interfacial features of objects with differing densities are delineated in the image as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. Experiments with ex vivo murine tumors and human tumor phantoms point out a diagnostic capability of the method for identifying tumors.

  18. Ultrasound Activated Contrast Imaging for Prostate Cancer Detection

    DTIC Science & Technology

    2007-03-01

    Goldberg. Nonlinear imaging with a new contrast agent. Ultrasound Med Biol, vol. 29, pp. S97, 2003. R. J. Ro, F. Forsberg, M. Knauer, W. T. Shi, P. A ... Lewin , R. Bernardi. On the temperature and concentration dependency of excitation-enhanced imaging. Proc Biomed Eng Soc Ann Fall Meetg, abstract no

  19. Image enhancement by adjusting the contrast of spatial frequencies

    NASA Astrophysics Data System (ADS)

    Yang, Ching-Chung

    2008-02-01

    We demonstrate a brand-new method for image enhancement by adjusting the contrast of different spatial frequencies. Fine characteristics of an image are well enhanced with negligible side effects. This method is easy to implement owing to its simple optical basis.

  20. Selective polarization imager for contrast enhancement in extended scattering media

    NASA Astrophysics Data System (ADS)

    Miller, Darren Alexis

    Improved imaging and detection of objects through turbid obscurants is a vital problem of current interest to both military and civilian entities. Image quality is severely degraded when obscurant fields such as fog, smoke, dust, etc., lie between an object and the light-collecting optics. Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles (e.g. in fog) or random variations of refractive index (e.g. in medical imaging). Intensity imaging does not differentiate between rays scattered off particles in the obscurant field and those reflected off objects within the field. Scattering degrades image quality in all spectral bands (UV, visible, and IR), although the amount of degradation is wavelength dependent. This dissertation features the development of innovative system designs and techniques that utilize scattered radiation's deterministic polarization state evolution to greatly enhance the image contrast of stand-off objects within obscurant fields such as smoke, fog, or dust using active polarized illumination in the visible. The produced sensors acquire and process image data in real time using computationally non-intensive algorithms that differentiate between radiation that scatters or reflects from obscured objects and the radiation from the scattering media, improving image contrast by factors of ten or greater for dense water vapor obscurants.

  1. Phase contrast imaging with coherent high energy X-rays

    SciTech Connect

    Snigireva, I.

    1997-02-01

    X-ray imaging concern high energy domain (>6 keV) like a contact radiography, projection microscopy and tomography is used for many years to discern the features of the internal structure non destructively in material science, medicine and biology. In so doing the main contrast formation is absorption that makes some limitations for imaging of the light density materials and what is more the resolution of these techniques is not better than 10-100 {mu}m. It was turned out that there is now way in which to overcome 1{mu}m or even sub-{mu}m resolution limit except phase contrast imaging. It is well known in optics that the phase contrast is realised when interference between reference wave front and transmitted through the sample take place. Examples of this imaging are: phase contrast microscopy suggested by Zernike and Gabor (in-line) holography. Both of this techniques: phase contrast x-ray microscopy and holography are successfully progressing now in soft x-ray region. For imaging in the hard X-rays to enhance the contrast and to be able to resolve phase variations across the beam the high degree of the time and more importantly spatial coherence is needed. Because of this it was reasonable that the perfect crystal optics was involved like Bonse-Hart interferometry, double-crystal and even triple-crystal set-up using Laue and Bragg geometry with asymmetrically cut crystals.

  2. Mechanical compression for contrasting OCT images of biotissues

    NASA Astrophysics Data System (ADS)

    Kirillin, Mikhail Y.; Argba, Pavel D.; Kamensky, Vladislav A.

    2011-06-01

    Contrasting of biotissue layers in OCT images after application of mechanical compression is discussed. The study is performed on ex vivo samples of human rectum, and in vivo on skin of human volunteers. We show that mechanical compression provides contrasting of biotissue layer boundaries due to different mechanical properties of layers. We show that alteration of pressure from 0 up to 0.45 N/mm2 causes contrast increase from 1 to 10 dB in OCT imaging of human rectum ex vivo. Results of ex vivo studies are in good agreement with Monte Carlo simulations. Application of pressure of 0.45 N/mm2 causes increase in contrast of epidermis-dermis junction in OCT-images of human skin in vivo for about 10 dB.

  3. Coastal Digital Surface Model on Low Contrast Images

    NASA Astrophysics Data System (ADS)

    Rosu, A.-M.; Assenbaum, M.; De la Torre, Y.; Pierrot-Deseilligny, M.

    2015-08-01

    Coastal sandy environments are extremely dynamic and require regular monitoring that can easily be achieved by using an unmanned aerial system (UAS) including a drone and a photo camera. The acquired images have low contrast and homogeneous texture. Using these images and with very few, if any, ground control points (GCPs), it is difficult to obtain a digital surface model (DSM) by classical correlation and automatic interest points determination approach. A possible response to this problem is to work with enhanced, contrast filtered images. To achieve this, we use and tune the free open-source software MicMac.

  4. Development of contrast-enhanced rodent imaging using functional CT

    NASA Astrophysics Data System (ADS)

    Liang, Yun; Stantz, Keith M.; Krishnamurthi, Ganapathy; Steinmetz, Rosemary; Hutchins, Gary D.

    2003-05-01

    Micro-computed tomography (microCT) is capable of obtaining high-resolution images of skeletal tissues. However its image contrast among soft tissues remains inadequate for tumor detection. High speed functional computed tomography will be needed to image tumors by employing x-ray contrast medium. The functional microCT development will not only facilitate the image contrast enhancement among different tissues but also provide information of tumor physiology. To demonstrate the feasibility of functional CT in mouse imaging, sequential computed tomography is performed in mice after contrast material administration using a high-speed clinical CT scanner. Although the resolution of the clinical scanner is not sufficient to dissolve the anatomic details of rodents, bulky physiological parameters in major organs such as liver, kidney, pancreas, and ovaries (testicular) can be examined. For data analysis, a two-compartmental model is employed and implemented to characterize the tissue physiological parameters (regional blood flow, capillary permeability, and relative compartment volumes.) The measured contrast dynamics in kidneys are fitted with the compartmental model to derive the kidney tissue physiology. The study result suggests that it is feasible to extract mouse tissue physiology using functional CT imaging technology.

  5. Material decomposition and virtual non-contrast imaging in photon counting computed tomography: an animal study

    NASA Astrophysics Data System (ADS)

    Gutjahr, R.; Polster, C.; Kappler, S.; Pietsch, H.; Jost, G.; Hahn, K.; Schöck, F.; Sedlmair, M.; Allmendinger, T.; Schmidt, B.; Krauss, B.; Flohr, T. G.

    2016-03-01

    The energy resolving capabilities of Photon Counting Detectors (PCD) in Computed Tomography (CT) facilitate energy-sensitive measurements. The provided image-information can be processed with Dual Energy and Multi Energy algorithms. A research PCD-CT firstly allows acquiring images with a close to clinical configuration of both the X-ray tube and the CT-detector. In this study, two algorithms (Material Decomposition and Virtual Non-Contrast-imaging (VNC)) are applied on a data set acquired from an anesthetized rabbit scanned using the PCD-CT system. Two contrast agents (CA) are applied: A gadolinium (Gd) based CA used to enhance contrasts for vascular imaging, and xenon (Xe) and air as a CA used to evaluate local ventilation of the animal's lung. Four different images are generated: a) A VNC image, suppressing any traces of the injected Gd imitating a native scan, b) a VNC image with a Gd-image as an overlay, where contrast enhancements in the vascular system are highlighted using colored labels, c) another VNC image with a Xe-image as an overlay, and d) a 3D rendered image of the animal's lung, filled with Xe, indicating local ventilation characteristics. All images are generated from two images based on energy bin information. It is shown that a modified version of a commercially available dual energy software framework is capable of providing images with diagnostic value obtained from the research PCD-CT system.

  6. Contrast ultrasound molecular imaging of inflammation in cardiovascular disease.

    PubMed

    Lindner, Jonathan R

    2009-11-01

    The cellular immune response plays an important role in almost every major form of cardiovascular disease. The ability to image the key aspects of the immune response in the clinical setting could be used to improve diagnostic information, to provide important prognostic or risk information, and to customize therapy according to disease phenotype. Accordingly, targeted imaging probes for assessing inflammation have been developed for essentially all forms of medical imaging. Molecular imaging of inflammation with contrast ultrasound relies on the detection of targeted microbubble or other gas-filled particle contrast agents. These agents are confined to the vascular space and, hence, have been targeted to either activated leucocytes or endothelial cell adhesion molecules that are upregulated in inflammation and mediate leucocyte recruitment and adhesion. This review focuses on the inflammation-targeting strategies for ultrasound contrast agents and how they have been matched to cardiovascular disease states such as myocardial ischaemia, infarction, atherosclerosis, transplant rejection, and arteriogenesis.

  7. A general theoretical formalism for X-ray phase contrast imaging.

    PubMed

    Wu, Xizeng; Liu, Hong

    2003-01-01

    The in-line phase-contrast imaging has great potential for clinical imaging applications. This work presents a general theoretical formalism for the in-line phase-contrast imaging. The theoretical formalism developed in this work is derived by taking a new strategy to calculate the Fourier transform of image intensity directly. Different from the transport of intensity equation (TIE) formalism for phase-contrast imaging in literature [6], this general formalism covers both the near field regime and the holography regime of phase-contrast imaging. The image intensity formulas have been derived in both the image space and frequency space. Especially our results show that the Fresnel diffraction image intensity is a sum of convolutions of the cosine- and sine-Fresnel filters with the object attenuation A20(x) and attenuated phase A20(x)φ(x), respectively. The Pogany-Gao-Wilkins (PGW) formalism is recovered as a special case of our general formalism. In addition, in the low-resolution approximation, the general formula is reduced a spherical wave-generalization of the TIE-based formula for phase-contrast imaging. This spherical wave-generalization will be useful for phase-contrast imaging with a micro-focus x-ray tube. The transition of the formalism from 1-D to 2-D cases has been provided as well.

  8. MR phase-contrast imaging in pulmonary hypertension.

    PubMed

    Reiter, Ursula; Reiter, Gert; Fuchsjäger, Michael

    2016-07-01

    Pulmonary hypertension (PH) is a life-threatening, multifactorial pathophysiological haemodynamic condition, diagnosed when the mean pulmonary arterial pressure equals or exceeds 25 mmHg at rest during right heart catheterization. Cardiac MRI, in general, and MR phase-contrast (PC) imaging, in particular, have emerged as potential techniques for the standardized assessment of cardiovascular function, morphology and haemodynamics in PH. Allowing the quantification and characterization of macroscopic cardiovascular blood flow, MR PC imaging offers non-invasive evaluation of haemodynamic alterations associated with PH. Techniques used to study the PH include both the routine two-dimensional (2D) approach measuring predominant velocities through an acquisition plane and the rapidly evolving four-dimensional (4D) PC imaging, which enables the assessment of the complete time-resolved, three-directional blood-flow velocity field in a volume. Numerous parameters such as pulmonary arterial mean velocity, vessel distensibility, flow acceleration time and volume and tricuspid regurgitation peak velocity, as well as the duration and onset of vortical blood flow in the main pulmonary artery, have been explored to either diagnose PH or find non-invasive correlates to right heart catheter parameters. Furthermore, PC imaging-based analysis of pulmonary arterial pulse-wave velocities, wall shear stress and kinetic energy losses grants novel insights into cardiopulmonary remodelling in PH. This review aimed to outline the current applications of 2D and 4D PC imaging in PH and show why this technique has the potential to contribute significantly to early diagnosis and characterization of PH.

  9. Confidence Level and Sensitivity Limits in High Contrast Imaging

    SciTech Connect

    Marois, C; LaFreniere, D; Macintosh, B; Doyon, R

    2008-06-02

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

  10. Confidence Level and Sensitivity Limits in High Contrast Imaging

    SciTech Connect

    Marois, C

    2007-11-07

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

  11. Gadolinium- and manganite-based contrast agents with fluorescent probes for both magnetic resonance and fluorescence imaging of pancreatic islets: a comparative study.

    PubMed

    Berkova, Zuzana; Jirak, Daniel; Zacharovova, Klara; Lukes, Ivan; Kotkova, Zuzana; Kotek, Jan; Kacenka, Michal; Kaman, Ondrej; Rehor, Ivan; Hajek, Milan; Saudek, Frantisek

    2013-04-01

    Three magnetic resonance (MR)/fluorescence imaging probes were tested for visualization, cellular distribution, and survival of labeled pancreatic islets in vitro and following transplantation. As T(1) contrast agents (CAs), gadolinium(III) complexes linked to β-cyclodextrin (Gd-F-βCD) or bound to titanium dioxide (TiO2 @RhdGd) were tested. As a T(2) CA, perovskite manganite nanoparticles (LSMO@siF@si) were examined. Fluorescein or rhodamine was incorporated as a fluorescent marker in all probes. Islets labeled with gadolinium(III) CAs were visible as hyperintense spots on MR in vitro, but detection in vivo was inconclusive. Islets labeled with LSMO@siF@si CA were clearly visible as hypointense spots or areas on MR scans in vitro as well as in vivo. All CAs were detected inside the islet cells by fluorescence. Although the vitality and function of the labeled islets was not impaired by any of the tested CAs, results indicate that LSMO@siF@si CA is a superior marker for islet labeling, as it provides better contrast enhancement within a shorter scan time.

  12. Phase-contrast enhanced mammography: A new diagnostic tool for breast imaging

    NASA Astrophysics Data System (ADS)

    Wang, Zhentian; Thuering, Thomas; David, Christian; Roessl, Ewald; Trippel, Mafalda; Kubik-Huch, Rahel A.; Singer, Gad; Hohl, Michael K.; Hauser, Nik; Stampanoni, Marco

    2012-07-01

    Phase contrast and scattering-based X-ray imaging can potentially revolutionize the radiological approach to breast imaging by providing additional and complementary information to conventional, absorption-based methods. We investigated native, non-fixed whole breast samples using a grating interferometer with an X-ray tube-based configuration. Our approach simultaneously recorded absorption, differential phase contrast and small-angle scattering signals. The results show that this novel technique - combined with a dedicated image fusion algorithm - has the potential to deliver enhanced breast imaging with complementary information for an improved diagnostic process.

  13. Phase-contrast enhanced mammography: A new diagnostic tool for breast imaging

    SciTech Connect

    Wang Zhentian; Thuering, Thomas; David, Christian; Roessl, Ewald; Trippel, Mafalda; Kubik-Huch, Rahel A.; Singer, Gad; Hohl, Michael K.; Hauser, Nik; Stampanoni, Marco

    2012-07-31

    Phase contrast and scattering-based X-ray imaging can potentially revolutionize the radiological approach to breast imaging by providing additional and complementary information to conventional, absorption-based methods. We investigated native, non-fixed whole breast samples using a grating interferometer with an X-ray tube-based configuration. Our approach simultaneously recorded absorption, differential phase contrast and small-angle scattering signals. The results show that this novel technique - combined with a dedicated image fusion algorithm - has the potential to deliver enhanced breast imaging with complementary information for an improved diagnostic process.

  14. Color-coded LED microscopy for multi-contrast and quantitative phase-gradient imaging

    PubMed Central

    Lee, Donghak; Ryu, Suho; Kim, Uihan; Jung, Daeseong; Joo, Chulmin

    2015-01-01

    We present a multi-contrast microscope based on color-coded illumination and computation. A programmable three-color light-emitting diode (LED) array illuminates a specimen, in which each color corresponds to a different illumination angle. A single color image sensor records light transmitted through the specimen, and images at each color channel are then separated and utilized to obtain bright-field, dark-field, and differential phase contrast (DPC) images simultaneously. Quantitative phase imaging is also achieved based on DPC images acquired with two different LED illumination patterns. The multi-contrast and quantitative phase imaging capabilities of our method are demonstrated by presenting images of various transparent biological samples. PMID:26713205

  15. A contrast and registration template for magnetic resonance image data guided dental implant placement

    NASA Astrophysics Data System (ADS)

    Eggers, Georg; Cosgarea, Raluca; Rieker, Marcus; Kress, Bodo; Dickhaus, Hartmut; Mühling, Joachim

    2009-02-01

    An oral imaging template was developed to address the shortcomings of MR image data for image guided dental implant planning and placement. The template was conctructed as a gadolinium filled plastic shell to give contrast to the dentition and also to be accurately re-attachable for use in image guided dental implant placement. The result of segmentation and modelling of the dentition from MR Image data with the template was compared to plaster casts of the dentition. In a phantom study dental implant placement was performed based on MR image data. MR imaging with the contrast template allowed complete representation of the existing dentition. In the phantom study, a commercially available system for image guided dental implant placement was used. Transformation of the imaging contrast template into a surgical drill guide based on the MR image data resulted in pilot burr hole placement with an accuracy of 2 mm. MRI based imaging of the existing dentition for proper image guided planning is possible with the proposed template. Using the image data and the template resulted in less accurate pilot burr hole placement in comparison to CT-based image guided implant placement.

  16. An efficient method for accurate segmentation of LV in contrast-enhanced cardiac MR images

    NASA Astrophysics Data System (ADS)

    Suryanarayana K., Venkata; Mitra, Abhishek; Srikrishnan, V.; Jo, Hyun Hee; Bidesi, Anup

    2016-03-01

    Segmentation of left ventricle (LV) in contrast-enhanced cardiac MR images is a challenging task because of high variability in the image intensity. This is due to a) wash-in and wash-out of the contrast agent over time and b) poor contrast around the epicardium (outer wall) region. Current approaches for segmentation of the endocardium (inner wall) usually involve application of a threshold within the region of interest, followed by refinement techniques like active contours. A limitation of this method is under-segmentation of the inner wall because of gradual loss of contrast at the wall boundary. On the other hand, the challenge in outer wall segmentation is the lack of reliable boundaries because of poor contrast. There are four main contributions in this paper to address the aforementioned issues. First, a seed image is selected using variance based approach on 4D time-frame images over which initial endocardium and epicardium is segmented. Secondly, we propose a patch based feature which overcomes the problem of gradual contrast loss for LV endocardium segmentation. Third, we propose a novel Iterative-Edge-Refinement (IER) technique for epicardium segmentation. Fourth, we propose a greedy search algorithm for propagating the initial contour segmented on seed-image across other time frame images. We have experimented our technique on five contrast-enhanced cardiac MR Datasets (4D) having a total of 1097 images. The segmentation results for all 1097 images have been visually inspected by a clinical expert and have shown good accuracy.

  17. Contrast enhancement of subcutaneous blood vessel images by means of visible and near-infrared hyper-spectral imaging

    NASA Astrophysics Data System (ADS)

    Katrašnik, Jaka; Bürmen, Miran; Pernuš, Franjo; Likar, Boštjan

    2009-02-01

    Visualization of subcutaneous veins is very difficult with the naked eye, but important for diagnosis of medical conditions and different medical procedures such as catheter insertion and blood withdrawal. Moreover, recent studies showed that the images of subcutaneous veins could be used for biometric identification. The majority of methods used for enhancing the contrast between the subcutaneous veins and surrounding tissue are based on simple imaging systems utilizing CMOS or CCD cameras with LED illumination capable of acquiring images from the near infrared spectral region, usually near 900 nm. However, such simplified imaging methods cannot exploit the full potential of the spectral information. In this paper, a new highly versatile method for enhancing the contrast of subcutaneous veins based on state-of-the-art high-resolution hyper-spectral imaging system utilizing the spectral region from 550 to 1700 nm is presented. First, a detailed analysis of the contrast between the subcutaneous veins and the surrounding tissue as a function of wavelength, for several different positions on the human arm, was performed in order to extract the spectral regions with the highest contrast. The highest contrast images were acquired at 1100 nm, however, combining the individual images from the extracted spectral regions by the proposed contrast enhancement method resulted in a single image with up to ten-fold better contrast. Therefore, the proposed method has proved to be a useful tool for visualization of subcutaneous veins.

  18. Velocity Measurement in Carotid Artery: Quantitative Comparison of Time-Resolved 3D Phase-Contrast MRI and Image-based Computational Fluid Dynamics

    PubMed Central

    Sarrami-Foroushani, Ali; Nasr Esfahany, Mohsen; Nasiraei Moghaddam, Abbas; Saligheh Rad, Hamidreza; Firouznia, Kavous; Shakiba, Madjid; Ghanaati, Hossein; Wilkinson, Iain David; Frangi, Alejandro Federico

    2015-01-01

    Background: Understanding hemodynamic environment in vessels is important for realizing the mechanisms leading to vascular pathologies. Objectives: Three-dimensional velocity vector field in carotid bifurcation is visualized using TR 3D phase-contrast magnetic resonance imaging (TR 3D PC MRI) and computational fluid dynamics (CFD). This study aimed to present a qualitative and quantitative comparison of the velocity vector field obtained by each technique. Subjects and Methods: MR imaging was performed on a 30-year old male normal subject. TR 3D PC MRI was performed on a 3 T scanner to measure velocity in carotid bifurcation. 3D anatomical model for CFD was created using images obtained from time-of-flight MR angiography. Velocity vector field in carotid bifurcation was predicted using CFD and PC MRI techniques. A statistical analysis was performed to assess the agreement between the two methods. Results: Although the main flow patterns were the same for the both techniques, CFD showed a greater resolution in mapping the secondary and circulating flows. Overall root mean square (RMS) errors for all the corresponding data points in PC MRI and CFD were 14.27% in peak systole and 12.91% in end diastole relative to maximum velocity measured at each cardiac phase. Bland-Altman plots showed a very good agreement between the two techniques. However, this study was not aimed to validate any of methods, instead, the consistency was assessed to accentuate the similarities and differences between Time-resolved PC MRI and CFD. Conclusion: Both techniques provided quantitatively consistent results of in vivo velocity vector fields in right internal carotid artery (RCA). PC MRI represented a good estimation of main flow patterns inside the vasculature, which seems to be acceptable for clinical use. However, limitations of each technique should be considered while interpreting results. PMID:26793288

  19. Color voltage contrast: A new method of implementing fault contrast with color imaging software

    SciTech Connect

    Colvin, J.

    1995-12-31

    Although voltage contrast and fault contrast methods are well established, the current methods of implementation are frequently tedious. A new method of mapping voltage contrast (VC) images in a qualitative (stroboscopic) color mode allows multiple logic states to be simultaneously viewed and updated in color. A shortcoming of image subtraction is that only one direction of logic change is represented unless the frames are exclusive OR`ed together. Although this gives fault information it does not include the VC of neighboring unchanged nodes. When tracking failures such as a saturated transistor resulting from a logic short somewhere else, all logic states; both static and transitional need to be understood and viewed simultaneously if an expedient analysis is desired.

  20. Contrast-enhanced magnetic resonance imaging of hypoperfused myocardium.

    PubMed

    Schaefer, S; Lange, R A; Gutekunst, D P; Parkey, R W; Willerson, J T; Peshock, R M

    1991-06-01

    Contrast-enhanced magnetic resonance (MR) imaging can define myocardial perfusion defects due to acute coronary occlusion. However, since most clinically important diagnostic examinations involve coronary arteries with subtotal stenoses, we investigated the ability of MR imaging with a manganese contrast agent to detect perfusion abnormalities in a canine model of partial coronary artery stenosis. The contrast agent was administered after the creation of a partial coronary artery stenosis with the addition of the coronary vasodilator dipyridamole in six of 12 animals. The hearts were imaged ex situ using gradient reversal and spin-echo sequences, and images were analyzed to determine differences in signal intensity between hypoperfused and normally perfused myocardium. Comparison of MR images with regional blood flow and thallium-201 measurements showed good concordance of hypoperfused segments in those animals given dipyridamole, with 75% of the abnormal segments correctly identified. In those animals not given dipyridamole, 48% of segments were correctly identified. Thus, ex vivo MR imaging with a paramagnetic contrast enhancement can be used to detect acute regional myocardial perfusion abnormalities due to severe partial coronary artery stenoses.

  1. Theoretical Evaluation of Compositional Contrast of Scanning Electron Microscope Images

    NASA Astrophysics Data System (ADS)

    Kotera, Masatoshi; Yamaguchi, Satoru; Fujiwara, Takafumi; Suga, Hiroshi

    1992-12-01

    The compositional contrast in the scanning electron microscope image is calculated for Al-Cu, Si-Cu and Al-Si contacts. An electron scattering phenomenon in the specimen is simulated in a direct manner. Electron refraction at the boundary, because of the agreement of each Fermi energy at the boundary, is precisely taken into account. The backscattered electron image shows better resolution than the secondary electron image in terms of the boundary contrast when the primary electron energy is 1 keV. The signal intensity varies depending on materials adjacent to the location observed. The ultimate resolution of the compositional contrast of the scanning electron microscope can be below 1 nm.

  2. Blood pool contrast agents for venous magnetic resonance imaging

    PubMed Central

    Oliveira, Irai S.; Li, Weier; Ganguli, Suvranu; Prabhakar, Anand M.

    2016-01-01

    Imaging of the venous system plays a vital role in the diagnosis and management of a wide range of clinically significant disorders. There have been great advances in venous imaging techniques, culminating in the use of magnetic resonance venography (MRV). Although MRV has distinct advantages in anatomic and quantitative cross sectional imaging without ionizing radiation, there are well-known challenges in acquisition timing and contrast administration in patients with renal impairment. The latest advancement involves the addition of new contrast media agents, which have emerged as valuable alternatives in these difficult scenarios. In this review, we will focus on a group of specific contrast agents called blood pool agents and discuss their salient features and clinical applications. PMID:28123972

  3. Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Kennedy, S. M.; Zheng, C. X.; Jesson, D. E.

    2017-01-01

    Image simulation methods are applied to interpret mirror electron microscopy (MEM) images obtained from a movie of GaAs droplet epitaxy. Cylindrical symmetry of structures grown by droplet epitaxy is assumed in the simulations which reproduce the main features of the experimental MEM image contrast, demonstrating that droplet epitaxy can be studied in real-time. It is therefore confirmed that an inner ring forms at the droplet contact line and an outer ring (or skirt) occurs outside the droplet periphery. We believe that MEM combined with image simulations will be increasingly used to study the formation and growth of quantum structures.

  4. Ultrasound contrast agent imaging: Real-time imaging of the superharmonics

    NASA Astrophysics Data System (ADS)

    Peruzzini, D.; Viti, J.; Tortoli, P.; Verweij, M. D.; de Jong, N.; Vos, H. J.

    2015-10-01

    Currently, in medical ultrasound contrast agent (UCA) imaging the second harmonic scattering of the microbubbles is regularly used. This scattering is in competition with the signal that is caused by nonlinear wave propagation in tissue. It was reported that UCA imaging based on the third or higher harmonics, i.e. "superharmonic" imaging, shows better contrast. However, the superharmonic scattering has a lower signal level compared to e.g. second harmonic signals. This study investigates the contrast-to-tissue ratio (CTR) and signal to noise ratio (SNR) of superharmonic UCA scattering in a tissue/vessel mimicking phantom using a real-time clinical scanner. Numerical simulations were performed to estimate the level of harmonics generated by the microbubbles. Data were acquired with a custom built dual-frequency cardiac phased array probe. Fundamental real-time images were produced while beam formed radiofrequency (RF) data was stored for further offline processing. The phantom consisted of a cavity filled with UCA surrounded by tissue mimicking material. The acoustic pressure in the cavity of the phantom was 110 kPa (MI = 0.11) ensuring non-destructivity of UCA. After processing of the acquired data from the phantom, the UCA-filled cavity could be clearly observed in the images, while tissue signals were suppressed at or below the noise floor. The measured CTR values were 36 dB, >38 dB, and >32 dB, for the second, third, and fourth harmonic respectively, which were in agreement with those reported earlier for preliminary contrast superharmonic imaging. The single frame SNR values (in which `signal' denotes the signal level from the UCA area) were 23 dB, 18 dB, and 11 dB, respectively. This indicates that noise, and not the tissue signal, is the limiting factor for the UCA detection when using the superharmonics in nondestructive mode.

  5. Ultrasound contrast agent imaging: Real-time imaging of the superharmonics

    SciTech Connect

    Peruzzini, D.; Viti, J.; Tortoli, P.; Verweij, M. D.; Jong, N. de; Vos, H. J.

    2015-10-28

    Currently, in medical ultrasound contrast agent (UCA) imaging the second harmonic scattering of the microbubbles is regularly used. This scattering is in competition with the signal that is caused by nonlinear wave propagation in tissue. It was reported that UCA imaging based on the third or higher harmonics, i.e. “superharmonic” imaging, shows better contrast. However, the superharmonic scattering has a lower signal level compared to e.g. second harmonic signals. This study investigates the contrast-to-tissue ratio (CTR) and signal to noise ratio (SNR) of superharmonic UCA scattering in a tissue/vessel mimicking phantom using a real-time clinical scanner. Numerical simulations were performed to estimate the level of harmonics generated by the microbubbles. Data were acquired with a custom built dual-frequency cardiac phased array probe. Fundamental real-time images were produced while beam formed radiofrequency (RF) data was stored for further offline processing. The phantom consisted of a cavity filled with UCA surrounded by tissue mimicking material. The acoustic pressure in the cavity of the phantom was 110 kPa (MI = 0.11) ensuring non-destructivity of UCA. After processing of the acquired data from the phantom, the UCA-filled cavity could be clearly observed in the images, while tissue signals were suppressed at or below the noise floor. The measured CTR values were 36 dB, >38 dB, and >32 dB, for the second, third, and fourth harmonic respectively, which were in agreement with those reported earlier for preliminary contrast superharmonic imaging. The single frame SNR values (in which ‘signal’ denotes the signal level from the UCA area) were 23 dB, 18 dB, and 11 dB, respectively. This indicates that noise, and not the tissue signal, is the limiting factor for the UCA detection when using the superharmonics in nondestructive mode.

  6. Near-infrared fluorescence imaging of experimentally collagen-induced arthritis in rats using the nonspecific dye tetrasulfocyanine in comparison with gadolinium-based contrast-enhanced magnetic resonance imaging, histology, and clinical score

    NASA Astrophysics Data System (ADS)

    Gemeinhardt, Ines; Puls, Dorothee; Gemeinhardt, Ole; Taupitz, Matthias; Wagner, Susanne; Schnorr, Beatrix; Licha, Kai; Schirner, Michael; Ebert, Bernd; Petzelt, Diethard; Macdonald, Rainer; Schnorr, Jörg

    2012-10-01

    Using 15 rats with collagen-induced arthritis (30 joints) and 7 control rats (14 joints), we correlated the intensity of near-infrared fluorescence (NIRF) of the nonspecific dye tetrasulfocyanine (TSC) with magnetic resonance imaging (MRI), histopathology, and clinical score. Fluorescence images were obtained in reflection geometry using a NIRF camera system. Normalized fluorescence intensity (INF) was determined after intravenous dye administration on different time points up to 120 min. Contrast-enhanced MRI using gadodiamide was performed after NIRF imaging. Analyses were performed in a blinded fashion. Histopathological and clinical scores were determined for each ankle joint. INF of moderate and high-grade arthritic joints were significantly higher (p<0.005) than the values of control and low-grade arthritic joints between 5 and 30 min after TSC-injection. This result correlated well with post-contrast MRI signal intensities at about 5 min after gadodiamide administration. Furthermore, INF and signal increase on contrast-enhanced MRI showed high correlation with clinical and histopathological scores. Sensitivities and specificities for detection of moderate and high-grade arthritic joints were slightly lower for NIRF imaging (89%/81%) than for MRI (100%/91%). NIRF imaging using TSC, which is characterized by slower plasma clearance compared to indocyanine green (ICG), has the potential to improve monitoring of inflamed joints.

  7. Tissue Necrosis Monitoring for HIFU Ablation with T1 Contrast MRI Imaging

    NASA Astrophysics Data System (ADS)

    Hwang, San-Chao; Yao, Ching; Kuo, Ih-Yuan; Tsai, Wei-Cheng; Chang, Hsu

    2011-09-01

    In MR-guided HIFU ablation, MTC (Magnetization Transfer Contrast) or perfusion imaging is usually used after ablation to evaluate the ablated area based on the thermally induced necrosis contrast. In our MR-guided HIFU ablation study, a T1 contrast MRI scan sequence has been used to distinguish between necrotic and non-necrotic tissue. The ablation of porcine meat in-vitro and in-vivo pig leg muscle show that the necrotic area of T1 contrast MRI image coincides with the photographs of sliced specimen. The sequence is considerably easier to apply than MTC or perfusion imaging, while giving good necrosis contrast. In addition, no injection of contrast agent is needed, allowing multiple scans to be applied throughout the entire ablation procedure.

  8. High-Accuracy Ultrasound Contrast Agent Detection Method for Diagnostic Ultrasound Imaging Systems.

    PubMed

    Ito, Koichi; Noro, Kazumasa; Yanagisawa, Yukari; Sakamoto, Maya; Mori, Shiro; Shiga, Kiyoto; Kodama, Tetsuya; Aoki, Takafumi

    2015-12-01

    An accurate method for detecting contrast agents using diagnostic ultrasound imaging systems is proposed. Contrast agents, such as microbubbles, passing through a blood vessel during ultrasound imaging are detected as blinking signals in the temporal axis, because their intensity value is constantly in motion. Ultrasound contrast agents are detected by evaluating the intensity variation of a pixel in the temporal axis. Conventional methods are based on simple subtraction of ultrasound images to detect ultrasound contrast agents. Even if the subject moves only slightly, a conventional detection method will introduce significant error. In contrast, the proposed technique employs spatiotemporal analysis of the pixel intensity variation over several frames. Experiments visualizing blood vessels in the mouse tail illustrated that the proposed method performs efficiently compared with conventional approaches. We also report that the new technique is useful for observing temporal changes in microvessel density in subiliac lymph nodes containing tumors. The results are compared with those of contrast-enhanced computed tomography.

  9. Spatial contrast sensitivity through aviator's night vision imaging system.

    PubMed

    Rabin, J

    1993-08-01

    Visual acuity is often used to assess vision through image intensifying devices such as night vision goggles (NVG's). Fewer attempts have been made to measure contrast sensitivity through NVG's. Such information would be useful to better understand contrast processing through NVG's under various stimulus conditions. In this study, computer-generated letter charts were used to measure contrast sensitivity through third generation NVG's for a range of letter sizes. The red phosphor of a standard color monitor proved to be an effective stimulus for third generation devices. Different night sky conditions were simulated over a 3 log unit range. The results illustrate the profile of contrast sensitivity through third generation NVG's over a range of night sky conditions. Comparison of measurements through NVG's to measurements obtained without the device but at the same luminance and color distinguish between effects of luminance and noise on contrast sensitivity.

  10. Dual-frequency chirp imaging for contrast detection

    NASA Astrophysics Data System (ADS)

    Cheng, Chih-Hao; Shen, Che-Chou; Yeh, Chih-Kuang

    2011-05-01

    The method of dual-frequency (DF) difference excitation is capable of generating a low-frequency envelope component as the driving force of commercial contrast microbubbles by using a high-frequency pulse. Although the DF difference excitation method provides good lateral resolution in high-frequency contrast imaging, it suffers from degraded axial resolution because a longer-than-usual envelope component is required to induce the oscillation of microbubbles. In this study, a coded excitation technique (i.e. chirp waveform) is combined with the DF difference excitation method (also referred to as the DF chirp excitation method) to improve the axial resolution of contrast imaging while maintaining the impinging insonation energy. B-mode images were constructed to compare the performance of the DF chirp excitation method with the conventional tone-burst pulse method. Results indicate that the proposed DF chirp excitation method can provide better axial resolution after pulse compression. Moreover, as compared to the tone-burst pulse with the same pulse duration, the pulse compression results in a higher signal-to-noise ratio because of the temporal concentration of the received energy. Nevertheless, images with the DF chirp excitation method demonstrated noticeable image artefacts resulting from the range sidelobes. The DF chirp excitation method also produced obvious tissue harmonic generation that could degrade the contrast-to-tissue ratio at higher acoustic pressures.

  11. Amplitude-modulation chirp imaging for contrast detection.

    PubMed

    Li, Meng-Lin; Kuo, Yu-Chen; Yeh, Chih-Kuang

    2010-09-01

    We propose an amplitude-modulation chirp imaging method for contrast detection with high-frequency ultrasound. Our proposed method detects microbubbles by extracting and then selectively compressing the component of the backscattered chirp signal modulated by changes in the radii of microbubbles at their resonance frequency. Microbubbles are sonicated simultaneously with a narrowband, low-frequency pumping signal at their resonance frequency and a wideband, high-frequency imaging chirp signal. Changes in the radii of the resonant microbubbles result in periodic changes in their acoustic cross section that modulate the amplitude of the backscattered imaging chirp signal, forming pumping and imaging frequency sum-and-difference chirp terms. The frequency-sum or -difference chirp component is then extracted by a bandpass filter (BPF). Because a long imaging pulse duration is required to obtain a sufficient modulation depth on the chirp for contrast detection and to facilitate frequency-sum-and-difference signal extraction with the BPF, a chirp with a longer-than-usual waveform is used so pulse compression of the extracted chirp signal can then be performed to maintain the axial resolution, and even further improve the signal-to-noise ratio and contrast-to-tissue ratio. Experiments performed on flow phantoms with and without a speckle-generating background were performed to demonstrate the efficacy of the proposed technique. These results indicate that our proposed method can potentially provide high-resolution contrast detection in the microvasculature.

  12. Dual-frequency chirp imaging for contrast detection.

    PubMed

    Cheng, Chih-Hao; Shen, Che-Chou; Yeh, Chih-Kuang

    2011-05-07

    The method of dual-frequency (DF) difference excitation is capable of generating a low-frequency envelope component as the driving force of commercial contrast microbubbles by using a high-frequency pulse. Although the DF difference excitation method provides good lateral resolution in high-frequency contrast imaging, it suffers from degraded axial resolution because a longer-than-usual envelope component is required to induce the oscillation of microbubbles. In this study, a coded excitation technique (i.e. chirp waveform) is combined with the DF difference excitation method (also referred to as the DF chirp excitation method) to improve the axial resolution of contrast imaging while maintaining the impinging insonation energy. B-mode images were constructed to compare the performance of the DF chirp excitation method with the conventional tone-burst pulse method. Results indicate that the proposed DF chirp excitation method can provide better axial resolution after pulse compression. Moreover, as compared to the tone-burst pulse with the same pulse duration, the pulse compression results in a higher signal-to-noise ratio because of the temporal concentration of the received energy. Nevertheless, images with the DF chirp excitation method demonstrated noticeable image artefacts resulting from the range sidelobes. The DF chirp excitation method also produced obvious tissue harmonic generation that could degrade the contrast-to-tissue ratio at higher acoustic pressures.

  13. Reflection-contrast limit of fiber-optic image guides

    PubMed Central

    Lane, Pierre M.; MacAulay, Calum E.

    2009-01-01

    Fiber-optic image guides in confocal reflectance endomicroscopes introduce background backscatter that limits the achievable contrast in these devices. We show the dominant source of backscatter from the image guide is due to Rayleigh scattering at short wavelengths and terminal reflections of the fibers at long wavelengths. The effective Rayleigh scattering coefficient and the wavelength-independent reflectivity due terminal reflections are measured experimentally in a commercial image guide. The Rayleigh scattering component of backscatter can be accurately predicted using the fractional refractive-index difference and length of the fibers in the image guide. We also presented a simple model that can be used to predict signal-to-background ratio in a fiber-optic confocal reflectance endomicroscope for biologically relevant tissues and contrast agents that cover a wide range of reflectivity. PMID:20059266

  14. A new ultrasonic transducer for improved contrast nonlinear imaging.

    PubMed

    Bouakaz, Ayache; Cate, Folkert ten; de Jong, Nico

    2004-08-21

    Second harmonic imaging has provided significant improvement in contrast detection over fundamental imaging. This improvement is a result of a higher contrast-to-tissue ratio (CTR) achievable at the second harmonic frequency. Nevertheless, the differentiation between contrast and tissue at the second harmonic frequency is still in many situations cumbersome and contrast detection remains nowadays as one of the main challenges, especially in the capillaries. The reduced CTR is mainly caused by the generation of second harmonic energy from nonlinear propagation effects in tissue, which hence obscures the echoes from contrast bubbles. In a previous study, we demonstrated theoretically that the CTR increases with the harmonic number. Therefore the purpose of our study was to increase the CTR by selectively looking to the higher harmonic frequencies. In order to be able to receive these high frequency components (third up to the fifth harmonic), a new ultrasonic phased array transducer has been constructed. The main advantage of the new design is its wide frequency bandwidth. The new array transducer contains two different types of elements arranged in an interleaved pattern (odd and even elements). This design enables separate transmission and reception modes. The odd elements operate at 2.8 MHz and 80% bandwidth, whereas the even elements have a centre frequency of 900 kHz with a bandwidth of 50%. The probe is connected to a Vivid 5 system (GE-Vingmed) and proper software is developed for driving. The total bandwidth of such a transducer is estimated to be more than 150% which enables higher harmonic imaging at an adequate sensitivity and signal to noise ratio compared to standard medical array transducers. We describe in this paper the design and fabrication of the array transducer. Moreover its acoustic properties are measured and its performances for nonlinear contrast imaging are evaluated in vitro and in vivo. The preliminary results demonstrate the advantages of

  15. Managing the optical wavefront for high contrast exoplanet imaging with the WFIRST-AFTA coronagraph

    NASA Astrophysics Data System (ADS)

    Trauger, John T.; Krist, John E.; Moody, Dwight

    2016-01-01

    The prospect of extreme high contrast astronomical imaging from space has inspired developments of new coronagraph methods for exoplanet imaging and spectroscopy. However, the requisite contrast, at levels of a billion to one or better for the direct imaging of cool mature exoplanets in reflected visible starlight, leads to challenging new requirements on the stability and control of the optical wavefront at levels currently beyond the reach of ground based telescopes. We briefly review the designs, laboratory validations, and science prospects for direct imaging and spectroscopic characterization of exoplanet systems with an actively corrected Lyot coronagraph. We review exoplanet science performance predicted for NASA's WFIRST-AFTA coronagraph. Together with a pair of deformable mirrors for optical wavefront control, the Lyot coronagraph creates high contrast dark fields of view extending to angular separations within 0.1 arcsec from the central star at visible wavelengths. Performance metrics are presented, including image contrast and spectral bandwidth, and laboratory validation experience.

  16. Quantitative characterization of edge enhancement in phase contrast x-ray imaging.

    PubMed

    Monnin, P; Bulling, S; Hoszowska, J; Valley, J F; Meuli, R; Verdun, F R

    2004-06-01

    The aim of this study was to model the edge enhancement effect in in-line holography phase contrast imaging. A simple analytical approach was used to quantify refraction and interference contrasts in terms of beam energy and imaging geometry. The model was applied to predict the peak intensity and frequency of the edge enhancement for images of cylindrical fibers. The calculations were compared with measurements, and the relationship between the spatial resolution of the detector and the amplitude of the phase contrast signal was investigated. Calculations using the analytical model were in good agreement with experimental results for nylon, aluminum and copper wires of 50 to 240 microm diameter, and with numerical simulations based on Fresnel-Kirchhoff theory. A relationship between the defocusing distance and the pixel size of the image detector was established. This analytical model is a useful tool for optimizing imaging parameters in phase contrast in-line holography, including defocusing distance, detector resolution and beam energy.

  17. Inclusion of coherence in Monte Carlo models for simulation of x-ray phase contrast imaging.

    PubMed

    Cipiccia, Silvia; Vittoria, Fabio A; Weikum, Maria; Olivo, Alessandro; Jaroszynski, Dino A

    2014-09-22

    Interest in phase contrast imaging methods based on electromagnetic wave coherence has increased significantly recently, particularly at X-ray energies. This is giving rise to a demand for effective simulation methods. Coherent imaging approaches are usually based on wave optics, which require significant computational resources, particularly for producing 2D images. Monte Carlo (MC) methods, used to track individual particles/photons for particle physics, are not considered appropriate for describing coherence effects. Previous preliminary work has evaluated the possibility of incorporating coherence in Monte Carlo codes. However, in this paper, we present the implementation of refraction in a model that is based on time of flight calculations and the Huygens-Fresnel principle, which allow reproducing the formation of phase contrast images in partially and fully coherent experimental conditions. The model is implemented in the FLUKA Monte Carlo code and X-ray phase contrast imaging simulations are compared with experiments and wave optics calculations.

  18. Mechanisms of contrast enhancement in magnetic resonance imaging.

    PubMed

    Lee, D H

    1991-02-01

    The use of contrast agents has increased the sensitivity and specificity of magnetic resonance imaging (MRI). Contrast in MRI is multifactorial, depending not only on T1 and T2 relaxation rates, but also on flow, proton density and, in gradient-echo sequences, on the angle of the induced field. The use of contrast agents in MRI changes the T1 and T2 relaxation rates, producing increased signal intensity on T1-weighted images or decreased signal intensity on T2-weighted images, or both. All contrast agents produce changes in magnetic susceptibility by enhancing local magnetic fields. These effects are caused by interactions between nuclear and paramagnetic substance magnet moments, which produce accentuated transitions between spin states and cause shortening of T1; the paramagnetic substance causes accentuated local fields, which lead to increased dephasing and thus shortening of T2 or T2* relaxation time. The efficacy of shortening of T1, T2 or T2* relaxation time depends on the distance between the proton nucleus and the electronic field of the paramagnetic compound, the time of their interaction (correlation time) and the paramagnetic concentration. The MRI contrast agents currently in use cause shortening of T1, T2 or T2* relaxation time. Metal chelates (e.g., gadolinium-diethylene triamine penta-acetic acid [Gd-DTPA]) in low concentration cause shortening of T1 relaxation times, and the superparamagnetics (e.g., ferrite) cause shortening of T2 relaxation times.

  19. HIGH-CONTRAST IMAGING VIA MODAL CONVERGENCE OF DEFORMABLE MIRROR

    SciTech Connect

    Wang Feiling

    2012-06-01

    For extremely high contrast imaging, such as direct observation of faint stellar companions, an adaptive optics system is required to produce low-halo and low-speckle regions in the focal plane. A method for deformable mirror control is proposed to achieve this goal. The method relies on a modal convergence of the deformable mirror driven by a focal-plane metric. The modal sets are derived from the Walsh functions. The Walsh-function modes serve two purposes: the expansion of the actuator displacements and the expansion of the phase functions. Taking advantage of the unique properties of the modal functions, a universal control algorithm is devised for the realization of high-contrast focal planes with and without the help of conventional coronagraphy. Numerical modeling is conducted to simulate complete imaging systems under various scenarios. It is shown that the proposed method reliably produces high-contrast focal planes using either a segmented or a membrane mirror. In the presence of random aberration the method is shown to be able to maintain high-contrast focal planes. Requiring neither retrieval of electric fields nor detailed knowledge of the deformable mirrors, this technique may allow high-contrast imaging in real time.

  20. Molecular Imaging and Contrast Agent Database (MICAD): evolution and progress.

    PubMed

    Chopra, Arvind; Shan, Liang; Eckelman, W C; Leung, Kam; Latterner, Martin; Bryant, Stephen H; Menkens, Anne

    2012-02-01

    The purpose of writing this review is to showcase the Molecular Imaging and Contrast Agent Database (MICAD; www.micad.nlm.nih.gov ) to students, researchers, and clinical investigators interested in the different aspects of molecular imaging. This database provides freely accessible, current, online scientific information regarding molecular imaging (MI) probes and contrast agents (CA) used for positron emission tomography, single-photon emission computed tomography, magnetic resonance imaging, X-ray/computed tomography, optical imaging and ultrasound imaging. Detailed information on >1,000 agents in MICAD is provided in a chapter format and can be accessed through PubMed. Lists containing >4,250 unique MI probes and CAs published in peer-reviewed journals and agents approved by the United States Food and Drug Administration as well as a comma separated values file summarizing all chapters in the database can be downloaded from the MICAD homepage. Users can search for agents in MICAD on the basis of imaging modality, source of signal/contrast, agent or target category, pre-clinical or clinical studies, and text words. Chapters in MICAD describe the chemical characteristics (structures linked to PubChem), the in vitro and in vivo activities, and other relevant information regarding an imaging agent. All references in the chapters have links to PubMed. A Supplemental Information Section in each chapter is available to share unpublished information regarding an agent. A Guest Author Program is available to facilitate rapid expansion of the database. Members of the imaging community registered with MICAD periodically receive an e-mail announcement (eAnnouncement) that lists new chapters uploaded to the database. Users of MICAD are encouraged to provide feedback, comments, or suggestions for further improvement of the database by writing to the editors at micad@nlm.nih.gov.

  1. Contrast Imaging in Mouse Embryos Using High-frequency Ultrasound

    PubMed Central

    Denbeigh, Janet M.; Nixon, Brian A.; Puri, Mira C.; Foster, F. Stuart

    2015-01-01

    Ultrasound contrast-enhanced imaging can convey essential quantitative information regarding tissue vascularity and perfusion and, in targeted applications, facilitate the detection and measure of vascular biomarkers at the molecular level. Within the mouse embryo, this noninvasive technique may be used to uncover basic mechanisms underlying vascular development in the early mouse circulatory system and in genetic models of cardiovascular disease. The mouse embryo also presents as an excellent model for studying the adhesion of microbubbles to angiogenic targets (including vascular endothelial growth factor receptor 2 (VEGFR2) or αvβ3) and for assessing the quantitative nature of molecular ultrasound. We therefore developed a method to introduce ultrasound contrast agents into the vasculature of living, isolated embryos. This allows freedom in terms of injection control and positioning, reproducibility of the imaging plane without obstruction and motion, and simplified image analysis and quantification. Late gestational stage (embryonic day (E)16.6 and E17.5) murine embryos were isolated from the uterus, gently exteriorized from the yolk sac and microbubble contrast agents were injected into veins accessible on the chorionic surface of the placental disc. Nonlinear contrast ultrasound imaging was then employed to collect a number of basic perfusion parameters (peak enhancement, wash-in rate and time to peak) and quantify targeted microbubble binding in an endoglin mouse model. We show the successful circulation of microbubbles within living embryos and the utility of this approach in characterizing embryonic vasculature and microbubble behavior. PMID:25867243

  2. Development of contrast enhancing agents in magnetic resonance imaging.

    PubMed

    Lex, L

    1989-01-01

    Magnetic Resonance Imaging (MRI) is a powerful new diagnostic tool in medicine. In MRI there is a great need to improve the specific identification of different tissues i.e. to enhance the contrast between them. This review tries to cover most of the approaches known for solving this problem.

  3. Differential phase contrast X-ray imaging system and components

    DOEpatents

    Stutman, Daniel; Finkenthal, Michael

    2014-07-01

    A differential phase contrast X-ray imaging system includes an X-ray illumination system, a beam splitter arranged in an optical path of the X-ray illumination system, and a detection system arranged in an optical path to detect X-rays after passing through the beam splitter.

  4. Differential phase contrast X-ray imaging system and components

    DOEpatents

    Stutman, Daniel; Finkenthal, Michael

    2017-01-31

    A differential phase contrast X-ray imaging system includes an X-ray illumination system, a beam splitter arranged in an optical path of the X-ray illumination system, and a detection system arranged in an optical path to detect X-rays after passing through the beam splitter.

  5. Contrast imaging in mouse embryos using high-frequency ultrasound.

    PubMed

    Denbeigh, Janet M; Nixon, Brian A; Puri, Mira C; Foster, F Stuart

    2015-03-04

    Ultrasound contrast-enhanced imaging can convey essential quantitative information regarding tissue vascularity and perfusion and, in targeted applications, facilitate the detection and measure of vascular biomarkers at the molecular level. Within the mouse embryo, this noninvasive technique may be used to uncover basic mechanisms underlying vascular development in the early mouse circulatory system and in genetic models of cardiovascular disease. The mouse embryo also presents as an excellent model for studying the adhesion of microbubbles to angiogenic targets (including vascular endothelial growth factor receptor 2 (VEGFR2) or αvβ3) and for assessing the quantitative nature of molecular ultrasound. We therefore developed a method to introduce ultrasound contrast agents into the vasculature of living, isolated embryos. This allows freedom in terms of injection control and positioning, reproducibility of the imaging plane without obstruction and motion, and simplified image analysis and quantification. Late gestational stage (embryonic day (E)16.6 and E17.5) murine embryos were isolated from the uterus, gently exteriorized from the yolk sac and microbubble contrast agents were injected into veins accessible on the chorionic surface of the placental disc. Nonlinear contrast ultrasound imaging was then employed to collect a number of basic perfusion parameters (peak enhancement, wash-in rate and time to peak) and quantify targeted microbubble binding in an endoglin mouse model. We show the successful circulation of microbubbles within living embryos and the utility of this approach in characterizing embryonic vasculature and microbubble behavior.

  6. Denoising in Contrast-Enhanced X-ray Images

    NASA Astrophysics Data System (ADS)

    Jeon, Gwanggil

    2016-12-01

    In this paper, we propose a denoising and contrast-enhancement method for medical images. The main purpose of medical image improvement is to transform lower contrast data into higher contrast, and to reduce high noise levels. To meet this goal, we propose a noise-level estimation method, whereby the noise level is estimated by computing the standard deviation and variance in a local block. The obtained noise level is then used as an input parameter for the block-matching and 3D filtering (BM3D) algorithm, and the denoising process is then performed. Noise-level estimation step is important because the BM3D algorithm does not perform well without correct noise-level information. Simulation results confirm that the proposed method outperforms other benchmarks with respect to both their objective and visual performances.

  7. Robust automatic focus algorithm for low contrast images using a new contrast measure.

    PubMed

    Xu, Xin; Wang, Yinglin; Tang, Jinshan; Zhang, Xiaolong; Liu, Xiaoming

    2011-01-01

    Low contrast images, suffering from a lack of sharpness, are easily influenced by noise. As a result, many local false peaks may be generated in contrast measurements, making it difficult for the camera's passive auto-focus system to perform its function of locating the focused peak. In this paper, a new passive auto-focus algorithm is proposed to address this problem. First, a noise reduction preprocessing is introduced to make our algorithm robust to both additive noise and multiplicative noise. Then, a new contrast measure is presented to bring in local false peaks, ensuring the presence of a well defined focused peak. In order to gauge the performance of our algorithm, a modified peak search algorithm is used in the experiments. The experimental results from an actual digital camera validate the effectiveness of our proposed algorithm.

  8. High contrast optical imaging methods for image guided laser ablation of dental caries lesions

    NASA Astrophysics Data System (ADS)

    LaMantia, Nicole R.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Darling, Cynthia L.; Fried, Daniel

    2014-02-01

    Laser based methods are well suited for automation and can be used to selectively remove dental caries to minimize the loss of healthy tissues and render the underlying enamel more resistant to acid dissolution. The purpose of this study was to determine which imaging methods are best suited for image-guided ablation of natural non-cavitated carious lesions on occlusal surfaces. Multiple caries imaging methods were compared including near-IR and visible reflectance and quantitative light fluorescence (QLF). In order for image-guided laser ablation to be feasible, chemical and physical modification of tooth surfaces due to laser irradiation cannot greatly reduce the contrast between sound and demineralized dental hard tissues. Sound and demineralized surfaces of 48 extracted human molar teeth with non-cavitated lesions were examined. Images were acquired before and after laser irradiation using visible and near-IR reflectance and QLF at several wavelengths. Polarization sensitive-optical coherence tomography was used to confirm that lesions were present. The highest contrast was attained at 1460-nm and 1500-1700-nm, wavelengths coincident with higher water absorption. The reflectance did not decrease significantly after laser irradiation for those wavelengths.

  9. Image quality and high contrast improvements on VLT/NACO

    NASA Astrophysics Data System (ADS)

    Girard, Julien H. V.; O'Neal, Jared; Mawet, Dimitri; Kasper, Markus; Zins, Gérard; Neichel, Benoît; Kolb, Johann; Christiaens, Valentin; Tourneboeuf, Martin

    2012-07-01

    NACO is the famous and versatile diffraction limited NIR imager and spectrograph at the VLT with which ESO celebrated 10 years of Adaptive Optics. Since two years a substantial effort has been put in understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in october 2011. NACO is therefore even more suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially the ones working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, and possibly ERIS).

  10. Quasi-real-time fluorescence imaging with lifetime dependent contrast

    NASA Astrophysics Data System (ADS)

    Jiang, Pei-Chi; Grundfest, Warren S.; Stafsudd, Oscar M.

    2011-08-01

    Conventional fluorescence lifetime imaging requires complicated algorithms to extract lifetimes of fluorophores and acquisition of multiple data points at progressively longer delay times to characterize tissues. To address diminishing signal-to-noise ratios at these progressively longer time delays, we report a time-resolved fluorescence imaging method, normalized fluorescence yield imaging that does not require the extraction of lifetimes. The concept is to extract the ``contrast'' instead of the lifetime value of the fluorophores by using simple mathematical algorithms. This process converts differences in decay times directly to different intensities. The technique was verified experimentally using a gated iCCD camera and an ultraviolet light-emitting diode light source. It was shown that this method can distinguish between chemical dyes (Fluorescein and Rhodamine-B) and biomedical samples, such as powders of elastin and collagen. Good contrast was obtained between fluorophores that varied by less than 6% in lifetime. Additionally, it was shown that long gate times up to 16 ns achieve good contrast depending upon the samples to be studied. These results support the feasibility of time-resolved fluorescence imaging without lifetime extraction, which has a potential clinical role in noninvasive real-time imaging.

  11. CHAOS: Prenatal imaging findings with post mortem contrast radiographic correlation

    PubMed Central

    Gupta, Kanika; Venkatesan, Bhuvaneswari; Manoharan, Kiruba Shankar; Rajalakshmi, Vaithianathan; Menon, Maya

    2016-01-01

    Congenital high airway obstruction syndrome is a rare fetal anomaly with characteristic constellation of prenatal findings on ultrasound and MRI. The typical triad of imaging features are enlarged and echogenic lungs, flattening or inversion of diaphragm and fetal hydrops. Early prenatal recognition of congenital high airway obstruction syndrome by ultrasound and/or MRI is mandatory for the appropriate perinatal management. We report a case of a male fetus with typical imaging findings of congenital high airway obstruction syndrome on ultrasound and MRI at 19 weeks of gestation. The role of contrast radiographs of fetal airways, including retrograde laryngogram, in confirming the postnatal diagnosis of this fetal condition is demonstrated. The prenatal imaging findings were correlated with contrast radiographs of upper airways, sonography of aborted fetus and fetal autopsy findings. PMID:27761192

  12. Multifunctional ultrasound contrast agents for imaging guided photothermal therapy.

    PubMed

    Guo, Caixin; Jin, Yushen; Dai, Zhifei

    2014-05-21

    Among all the imaging techniques, ultrasound imaging has a unique advantage due to its features of real-time, low cost, high safety, and portability. Ultrasound contrast agents (UCAs) have been widely used to enhance ultrasonic signals. One of the most exciting features of UCAs for use in biomedicine is the possibility of easily putting new combinations of functional molecules into microbubbles (MBs), which are the most routinely used UCAs. Various therapeutic agents and medical nanoparticles (quantum dots, gold, Fe3O4, etc.) can be loaded into ultrasound-responsive MBs. Hence, UCAs can be developed as multifunctional agents that integrate capabilities for early detection and diagnosis and for imaging guided therapy of various diseases. The current review will focus on such state-of-the-art UCA platforms that have been exploited for multimodal imaging and for imaging guided photothermal therapy.

  13. The ZIMPOL high contrast imaging polarimeter for SPHERE: polarimetric high contrast commissioning results

    NASA Astrophysics Data System (ADS)

    Roelfsema, Ronald; Bazzon, Andreas; Schmid, Hans Martin; Pragt, Johan; Govaert, Alain; Gisler, Daniel; Dominik, Carsten; Baruffolo, Andrea; Beuzit, Jean-Luc; Costille, Anne; Dohlen, Kjetil; Downing, Mark; Elswijk, Eddy; de Haan, Menno; Hubin, Norbert; Kasper, Markus; Keller, Christoph; Lizon, Jean-Louis; Mouillet, David; Pavlov, Alexey; Puget, Pascal; Salasnich, Bernardo; Sauvage, Jean-Francois; Wildi, Francois

    2016-07-01

    SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a second generation VLT instrument aimed at the direct detection of exo-planets. It has received its first light in May 2014. ZIMPOL (Zurich Imaging Polarimeter) is the imaging polarimeter subsystem of the SPHERE instrument. It's capable of both high accuracy and high sensitivity polarimetry but can also be used as a classical imager. It is located behind an extreme AO system and a stellar coronagraph. ZIMPOL operates at visible wavelengths which is best suited to detect the very faint reflected and hence polarized visible light from extra solar planets. During the SPHERE fourth commissioning period (October 2014) we have made deep coronagraphic observations of the bright star alpha Gru (mR = 1.75) to assess the high contrast polarimetric performance of SPHERE-ZIMPOL. We have integrated on the target for a total time of about 45 minutes during the meridian transit in the Very Broad Band filter (600 - 900 nm) with a classical Lyot coronagraph with 3 λ/D radius focal mask. We reduce the data by a combination of Polarized Background subtraction, Polarimetric Differential Imaging (PDI) and Angular Differential Imaging (ADI). We reach contrasts of 10-6 and 10-7 at a radial distances of respectively 7 and 14 lambda/D from the PSF core. At these radial distances we are respectively a factor of 10 and 2 above the photon noise limit. We discuss our results by considering the temporal and spatial speckle behavior close to the PSF core in combination with low order polarimetric aberrations.

  14. Optimization of phase contrast imaging using hard x rays

    SciTech Connect

    Zabler, S.; Cloetens, P.; Guigay, J.-P.; Baruchel, J.; Schlenker, M.

    2005-07-15

    X ray radiography and tomography are important tools in medicine as well as in life science and materials science. Not long ago an approach called in-line holography based on simple propagation became possible using partially coherent synchrotron beams like the ones available at the European Synchrotron Radiation Facility (ESRF). Theoretical and experimental work by Cloetens et al. [Appl. Phys. Lett 75, 2912 (1999)] have shown that quantitative retrieval of the optical phase, from a set of radiographs taken at different sample-to-detector distances, is feasible. Mathematically speaking we are dealing with a direct method based on linearization in order to solve an inverse nonlinear problem. The phase retrieval can be combined with classical tomography in order to obtain a three-dimensional representation of the object's electron density (holotomography). In order to optimize the image contrast for the numerical phase retrieval process, we have carried out calculations resulting in an optimized choice of value and number of the sample-to-detector distances as well as of the photon energy. These results were then confirmed by experiments on the ESRF long beamline ID19.

  15. Contrast-enhanced photoacoustic imaging of live lobster nerve cord

    NASA Astrophysics Data System (ADS)

    Witte, Russell S.; Huang, S.; Ashkenazi, S.; Kim, K.; O'Donnell, M.

    2007-02-01

    Photoacoustic imaging provides optical contrast with good penetration and high spatial resolution, making it an attractive tool for noninvasive neural applications. We chose a commercial dye (NK2761) commonly used for optical imaging of membrane potential to enhance photoacoustic images of the live lobster nerve cord. The abdominal segment of the nerve cord was excised, stained and positioned in a custom neural recording system, enabling electrical stimulation and recording of compound action potentials. Photoacoustic and pulse echo images were also collected using a commercial ultrasound scanner and a 10-MHz linear probe. A wavelength-tunable pulsed laser source (Surelite TM, 5 ns, ~15 mJ, 30 mJ/cm2) operating at 20 Hz produced photoacoustic waves. Longitudinal photoacoustic scans of a 25-mm segment of the excised nerve cord, including ganglionic and axonal processes, were collected and displayed every 7 seconds. Without the contrast agent, an average of 10 scans produced a peak photoacoustic signal 6 dB over background noise. An additional 29 dB was obtained after the nerve was submerged in the dye for 20 minutes. The gain decreased to 23 dB and 14 dB at 810 nm and 910 nm, respectively - consistent with the dye's optical absorbance measured using a portable spectrometer. The contrast-enhanced photoacoustic signal had a broad spectrum peaking at 4 MHz, and, after high pass filtering, images approached 200-μm spatial resolution. The hybrid imaging system, which provided several hours of electrical stimulation and recording, represents a robust testbed to develop novel photoacoustic contrast for neural applications.

  16. Dual-frequency piezoelectric transducers for contrast enhanced ultrasound imaging.

    PubMed

    Martin, K Heath; Lindsey, Brooks D; Ma, Jianguo; Lee, Mike; Li, Sibo; Foster, F Stuart; Jiang, Xiaoning; Dayton, Paul A

    2014-11-04

    For many years, ultrasound has provided clinicians with an affordable and effective imaging tool for applications ranging from cardiology to obstetrics. Development of microbubble contrast agents over the past several decades has enabled ultrasound to distinguish between blood flow and surrounding tissue. Current clinical practices using microbubble contrast agents rely heavily on user training to evaluate degree of localized perfusion. Advances in separating the signals produced from contrast agents versus surrounding tissue backscatter provide unique opportunities for specialized sensors designed to image microbubbles with higher signal to noise and resolution than previously possible. In this review article, we describe the background principles and recent developments of ultrasound transducer technology for receiving signals produced by contrast agents while rejecting signals arising from soft tissue. This approach relies on transmitting at a low-frequency and receiving microbubble harmonic signals at frequencies many times higher than the transmitted frequency. Design and fabrication of dual-frequency transducers and the extension of recent developments in transducer technology for dual-frequency harmonic imaging are discussed.

  17. Dual-Frequency Piezoelectric Transducers for Contrast Enhanced Ultrasound Imaging

    PubMed Central

    Martin, K. Heath; Lindsey, Brooks D.; Ma, Jianguo; Lee, Mike; Li, Sibo; Foster, F. Stuart; Jiang, Xiaoning; Dayton, Paul A.

    2014-01-01

    For many years, ultrasound has provided clinicians with an affordable and effective imaging tool for applications ranging from cardiology to obstetrics. Development of microbubble contrast agents over the past several decades has enabled ultrasound to distinguish between blood flow and surrounding tissue. Current clinical practices using microbubble contrast agents rely heavily on user training to evaluate degree of localized perfusion. Advances in separating the signals produced from contrast agents versus surrounding tissue backscatter provide unique opportunities for specialized sensors designed to image microbubbles with higher signal to noise and resolution than previously possible. In this review article, we describe the background principles and recent developments of ultrasound transducer technology for receiving signals produced by contrast agents while rejecting signals arising from soft tissue. This approach relies on transmitting at a low-frequency and receiving microbubble harmonic signals at frequencies many times higher than the transmitted frequency. Design and fabrication of dual-frequency transducers and the extension of recent developments in transducer technology for dual-frequency harmonic imaging are discussed. PMID:25375755

  18. Active extravasation of gadolinium-based contrast agent into the subdural space following lumbar puncture.

    PubMed

    Kothari, Pranay D; Hanser, Evelyn M; Wang, Harrison; Farid, Nikdokht

    2016-01-01

    A 38year-old male presented with cauda equina syndrome following multiple lumbar puncture attempts. Lumbar spine magnetic resonance imaging (MRI) showed a subdural hematoma and an area of apparent contrast enhancement in the spinal canal on sagittal post-contrast images. Axial post-contrast images obtained seven minutes later demonstrated an increase in size and change in shape of the region of apparent contrast enhancement, indicating active extravasation of the contrast agent. This is the first reported case of active extravasation of gadolinium-based contrast agent in the spine.

  19. Nonrigid registration and classification of the kidneys in 3D dynamic contrast enhanced (DCE) MR images

    NASA Astrophysics Data System (ADS)

    Yang, Xiaofeng; Ghafourian, Pegah; Sharma, Puneet; Salman, Khalil; Martin, Diego; Fei, Baowei

    2012-02-01

    We have applied image analysis methods in the assessment of human kidney perfusion based on 3D dynamic contrast-enhanced (DCE) MRI data. This approach consists of 3D non-rigid image registration of the kidneys and fuzzy C-mean classification of kidney tissues. The proposed registration method reduced motion artifacts in the dynamic images and improved the analysis of kidney compartments (cortex, medulla, and cavities). The dynamic intensity curves show the successive transition of the contrast agent through kidney compartments. The proposed method for motion correction and kidney compartment classification may be used to improve the validity and usefulness of further model-based pharmacokinetic analysis of kidney function.

  20. Magnetic resonance imaging and contrast enhancement. Scientific report

    SciTech Connect

    Swenberg, C.E.; Movius, E.G.

    1988-01-01

    Chapters II through VI of this report discuss: Relaxation of Nuclear Spins; Echo Techniques; Basic Imaging Pulse Sequences; Partial Saturation Recovery; Inversion Recovery; Spin Echo; Effects of Pulse Sequence on Image Contrast; Contrast Agents; Theoretical Aspects; Pharmacokinetics and Toxicity; and Physiological Rationale for Agent Selection. One of the major goals in all medical imaging techniques is to maximize one's ability to visualize and differentiate adjacent tissue regions in the body on the basis of differences in anatomy, physiology, or various pathological processes. Magnetic resonance (MR) imaging offers distinct advantages over conventional x-ray imaging because of the possibility of selecting specific pulse sequences that can differentiate adjacent structures on the basis of differences in proton density, T/sub 1/ or T/sub 2/ relaxation rates, or flow. As a result of applying these various pulse sequences, numerous images have been obtained of the brain and other organs that demonstrate considerably more-detailed anatomical structure than had previously been available with computerized tomography, ultrasound, or nuclear medicine techniques. In some situations it is clearly superior, such as in the diagnosis of multiple sclerosis.

  1. [Contrast agents in magnetic resonance imaging: development and problems].

    PubMed

    Xu, Yi-kai

    2002-09-01

    In spite of the inherent versatility of magnetic resonance imaging (MRI), researchers and clinicians from both home and aboard have made great achievements in developing safe and effective contrast agents. Many new agents are expected to be available for clinical use in the near future. It is of clinical importance that the agents should expand the diagnostic utility of MRI, improve the detection of tiny lesions and help evaluate specific tissue or organ functions. This article aims to examine current status of contrast agents for MRI and the problems waiting for solutions.

  2. Uncertainty analysis of quantitative imaging features extracted from contrast-enhanced CT in lung tumors

    PubMed Central

    Yang, Jinzhong; Zhang, Lifei; Fave, Xenia J.; Fried, David V.; Stingo, Francesco C.; Ng, Chaan S.; Court, Laurence E.

    2016-01-01

    Purpose To assess the uncertainty of quantitative imaging features extracted from contrast-enhanced computed tomography (CT) scans of lung cancer patients in terms of the dependency on the time after contrast injection and the feature reproducibility between scans. Methods Eight patients underwent contrast-enhanced CT scans of lung tumors on two sessions 2–7 days apart. Each session included 6 CT scans of the same anatomy taken every 15 seconds, starting 50 seconds after contrast injection. Image features based on intensity histogram, co-occurrence matrix, neighborhood gray-tone difference matrix, run-length matrix, and geometric shape were extracted from the tumor for each scan. Spearman’s correlation was used to examine the dependency of features on the time after contrast injection, with values over 0.50 considered time-dependent. Concordance correlation coefficients were calculated to examine the reproducibility of each feature between times of scans after contrast injection and between scanning sessions, with values greater than 0.90 considered reproducible. Results The features were found to have little dependency on the time between the contrast injection and the CT scan. Most features were reproducible between times of scans after contrast injection and between scanning sessions. Some features were more reproducible when they were extracted from a CT scan performed at a longer time after contrast injection. Conclusion The quantitative imaging features tested here are mostly reproducible and show little dependency on the time after contrast injection. PMID:26745258

  3. Joint contrast optimization and object segmentation in active polarimetric images.

    PubMed

    Anna, Guillaume; Bertaux, Nicolas; Galland, Frédéric; Goudail, François; Dolfi, Daniel

    2012-08-15

    We present a method for automatic target detection based on the iterative interplay between an active polarimetric imager with adaptive capabilities and a snake-based image segmentation algorithm. It successfully addresses the difficult situations where the target and the background differ only by their polarimetric properties. This method illustrates the benefits of integrating digital processing algorithms at the heart of the image acquisition process rather than using them only for postprocessing.

  4. Theoretical analysis of x-ray CT phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Feng, Sheng; Liu, Song; Zhang, Xuelong

    2008-12-01

    Recently phase contrast imaging has attracted much attention. An obvious advantage of using X-rays for imaging the internal structure of relatively thick samples lies in its high degree of penetration of solid objects. However, often leads to poor image contrast for soft tissue. Phase contrast imaging can be very useful in such situation, as the phase of the transmitted beam may often be more sensitive indicator of density of sample than convention contrast. On the other hand, Computed Tomography is the best technology in the aspect of X-rays detection. Using the technology, the detected object can be imaged to three-dimensional image, so as to observe the inner structure of object, and be convenient to the disease examination. If the phase contrast imaging can be used to the technology of Computed Tomography, the high resolution image can be gained. The technology will become the development orientation of medical image. The aim of this article was to apply the theory of X-rays phase contrast imaging to the traditional X-CT technique. For this purpose, the formula deduced from the imaging theory with parallel monochromatic X-rays illuminating the object based on the Fresnel-Kircohhof theory had been completed and a formula similar to that of the traditional X-CT reconstruction had been gained, which was Radon transform formula. At last, X-rays reconstruction simulation had been carried out according to the formula, and proved that the method could be used in clinical medical imaging. The method discussed in this paper had a very bright prospect for application.

  5. In vivo molecular contrast OCT imaging of methylene blue.

    PubMed

    Kim, Wihan; Applegate, Brian E

    2015-04-01

    An 830-nm spectral-domain optical coherence tomography (OCT) system with an integrated 663-nm diode pump laser has been developed to enable molecular contrast OCT imaging of methylene blue (MB), a common vital dye used clinically. The introduction of the 663-nm diode laser, which acts as the pump in this implementation of pump-probe OCT (PPOCT), represents a minor modification to an otherwise typical OCT system. A newly developed background subtraction technique completely removes all background from intensity noise at the pump modulation frequency, simplifying the interpretation of PPOCT images. These developments have enabled the first in vivo imaging of MB with PPOCT. Volumetric images of a zebrafish, stained by submersion in a 0.01% (w/v) solution of MB for 6 h, show accumulation of MB in the mesonephros, the primordial filtration organ.

  6. Cross contrast multi-channel image registration using image synthesis for MR brain images.

    PubMed

    Chen, Min; Carass, Aaron; Jog, Amod; Lee, Junghoon; Roy, Snehashis; Prince, Jerry L

    2017-02-01

    Multi-modal deformable registration is important for many medical image analysis tasks such as atlas alignment, image fusion, and distortion correction. Whereas a conventional method would register images with different modalities using modality independent features or information theoretic metrics such as mutual information, this paper presents a new framework that addresses the problem using a two-channel registration algorithm capable of using mono-modal similarity measures such as sum of squared differences or cross-correlation. To make it possible to use these same-modality measures, image synthesis is used to create proxy images for the opposite modality as well as intensity-normalized images from each of the two available images. The new deformable registration framework was evaluated by performing intra-subject deformation recovery, intra-subject boundary alignment, and inter-subject label transfer experiments using multi-contrast magnetic resonance brain imaging data. Three different multi-channel registration algorithms were evaluated, revealing that the framework is robust to the multi-channel deformable registration algorithm that is used. With a single exception, all results demonstrated improvements when compared against single channel registrations using the same algorithm with mutual information.

  7. a Novel Approach for Edge Detection of Low Contrast Satellite Images

    NASA Astrophysics Data System (ADS)

    Singh, K. K.; Bajpai, M. K.; Pandey, R. K.

    2015-03-01

    Discrimination between texture edges and geometrical edges is very difficult in low contrast images. Satellite images are low contrast images. It is important to extract the edges that are not clearly visible in case of Satellite images. The present work encompasses a new edge detection algorithm using newly constructed differentiator. Chebyshev polynomial based fractional order differentiator has been used for filtering operation on an image. High pass and Low pass filters are designed with the concept of Quadrature Mirror Filter (QMF). Pre-processing has been performed by using this filter. Sobel edge detection method has been applied on this pre-processed image. The algorithm has been tested with two different satellite images.

  8. Perfusion Imaging with a Freely Diffusible Hyperpolarized Contrast Agent

    PubMed Central

    Grant, Aaron K.; Vinogradov, Elena; Wang, Xiaoen; Lenkinski, Robert E.; Alsop, David C.

    2011-01-01

    Contrast agents that can diffuse freely into or within tissue have numerous attractive features for perfusion imaging. Here we present preliminary data illustrating the suitability of hyperpolarized 13C labeled 2-methylpropan-2-ol (also known as dimethylethanol, tertiary butyl alcohol and tert-butanol) as a freely diffusible contrast agent for magnetic resonance perfusion imaging. Dynamic 13C images acquired in rat brain with a balanced steady-state free precession (bSSFP) sequence following administration of hyperpolarized 2-methylpropan-2-ol show that this agent can be imaged with 2–4s temporal resolution, 2mm slice thickness, and 700 micron in-plane resolution while retaining adequate signal-to-noise ratio. 13C relaxation measurements on 2-methylpropan-2-ol in blood at 9.4T yield T1=46±4s and T2=0.55±0.03s. In the rat brain at 4.7T, analysis of the temporal dynamics of the bSSFP image intensity in tissue and venous blood indicate that 2-methylpropan-2-ol has a T2 of roughly 2–4s and a T1 of 43±24s. In addition, the images indicate that 2-methylpropan-2-ol is freely diffusible in brain and hence has a long residence time in tissue; this in turn makes it possible to image the agent continuously for tens of seconds. These characteristics show that 2-methylpropan-2-ol is a promising agent for robust and quantitative perfusion imaging in the brain and body. PMID:21432901

  9. Effects of nonlinear propagation in ultrasound contrast agent imaging.

    PubMed

    Tang, Meng-Xing; Kamiyama, Naohisa; Eckersley, Robert J

    2010-03-01

    This paper investigates two types of nonlinear propagation and their effects on image intensity and contrast-to-tissue ratio (CTR) in contrast ultrasound images. Previous studies have shown that nonlinear propagation can occur when ultrasound travels through tissue and microbubble clouds, making tissue farther down the acoustic path appear brighter in pulse inversion (PI) images, thus reducing CTR. In this study, the effect of nonlinear propagation through tissue or microbubbles on PI image intensity and CTR are compared at low mechanical index. A combination of simulation and experiment with SonoVue microbubbles were performed using a microbubble dynamics model, a laboratory ultrasound system and a clinical prototype scanner. The results show that, close to the bubble resonance frequency, nonlinear propagation through a bubble cloud of a few centimeter thickness with a modest concentration (1:10000 dilution of SonoVue microbubbles) is much more significant than through tissue-mimicking material. Consequently, CTR in regions distal to the imaging probe is greatly reduced for nonlinear propagation through the bubble cloud, with as much as a 12-dB reduction compared with nonlinear propagation through tissue-mimicking material. Both types of nonlinear propagation cause only a small change in bubble PI signals at the bubble resonance frequency. When the driving frequency increases beyond bubble resonance, nonlinear propagation through bubbles is greatly reduced in absolute values. However because of a greater reduction in nonlinear scattering from bubbles at higher frequencies, the corresponding CTR is much lower than that at bubble resonance frequency.

  10. Intravenous Imaging Contrast Media Complications: The Basics That Every Clinician Needs to Know.

    PubMed

    Rose, Trevor A; Choi, Jung W

    2015-09-01

    Intravenous contrast is commonly used in noninvasive imaging procedures such as magnetic resonance imaging and computed tomography and can evaluate blood vessels and better characterize soft-tissue lesions. Although the incidence of adverse events after administration of contrast is low, it is important that clinicians and radiologists minimize risks and respond quickly and effectively when reactions occur. We will discuss a range of adverse events to iodinated and gadolinium-based contrast agents, including allergic-like reactions, nephrotoxicity, extravasation, and nephrogenic systemic fibrosis. We will review risk stratification for patients, as well as premedication and treatment of adverse events.

  11. Characterization of encapsulated quantum dots via electron channeling contrast imaging

    NASA Astrophysics Data System (ADS)

    Deitz, Julia I.; Carnevale, Santino D.; De Graef, Marc; McComb, David W.; Grassman, Tyler J.

    2016-08-01

    A method for characterization of encapsulated epitaxial quantum dots (QD) in plan-view geometry using electron channeling contrast imaging (ECCI) is presented. The efficacy of the method, which requires minimal sample preparation, is demonstrated with proof-of-concept data from encapsulated (sub-surface) epitaxial InAs QDs within a GaAs matrix. Imaging of the QDs under multiple diffraction conditions is presented, establishing that ECCI can provide effectively identical visualization capabilities as conventional two-beam transmission electron microscopy. This method facilitates rapid, non-destructive characterization of sub-surface QDs giving immediate access to valuable nanostructural information.

  12. Silver Nanoplate Contrast Agents for In Vivo Molecular Photoacoustic Imaging

    PubMed Central

    Homan, Kimberly A.; Souza, Michael; Truby, Ryan; Luke, Geoffrey P.; Green, Christopher; Vreeland, Erika; Emelianov, Stanislav

    2012-01-01

    Silver nanoplates are introduced as a new photoacoustic contrast agent that can be easily functionalized for molecular photoacoustic imaging in vivo. Methods are described for synthesis, functionalization, and stabilization of silver nanoplates using biocompatible (“green”) reagents. Directional antibody conjugation to the nanoplate surface is presented along with proof of molecular sensitivity in vitro with pancreatic cancer cells. Cell viability tests show the antibody-conjugated silver nanoplates to be nontoxic at concentrations up to 1 mg/ml. Furthermore, the silver nanoplates' potential for in vivo application as a molecularly sensitive photoacoustic contrast agent is demonstrated using an orthotopic mouse model of pancreatic cancer. Results of these studies suggest that the synthesized silver nanoplates are well suited for a host of biomedical imaging and sensing applications. PMID:22188516

  13. High Contrast Imaging Testbed for the Terrestrial Planet Finder Coronagraph

    NASA Technical Reports Server (NTRS)

    Lowmman, Andrew E.; Trauger, John T.; Gordon, Brian; Green, Joseph J.; Moody, Dwight; Niessner, Albert F.; Shi, Fang

    2004-01-01

    The Terrestrial Planet Finder (TPF) mission is planning to launch a visible coronagraphic space telescope in 2014. To achieve TPF science goals, the coronagraph must have extreme levels of wavefront correction (less than 1 Angstrom rms over controllable spatial frequencies) and stability to get the necessary suppression of diffracted starlight (approximately l0(exp -10)) contrast at an angular separation approximately 4 (lamda)/D). TPF Coronagraph's primary platform for experimentation is the High Contrast Imaging Testbed, which will provide laboratory validation of key technologies as well as demonstration of a flight-traceable approach to implementation. Precision wavefront control in the testbed is provided by a high actuator density deformable mirror. Diffracted light control is achieved through use of occulting or apodizing masks and stops. Contrast measurements will establish the technical feasibility of TPF requirements, while model and error budget validation will demonstrate implementation viability. This paper describes the current testbed design, development approach, and recent experimental results.

  14. Optical imaging via biological object internal structure contrasting

    NASA Astrophysics Data System (ADS)

    Podgaetsky, Vitaly M.; Tereshchenko, Sergei A.; Vorobiev, Nikolai S.; Tomilova, Larisa G.; Smirnov, Alexander V.; Ivanov, Andrei V.

    1995-01-01

    For successful application of laser tomography methods for earlier medical diagnostics the signal-to-noise ratio (contrast) must be increased. For this purpose it is possible to use the absorbing dyes. We have theoretically investigated optical imaging conditions in high scattering medium on a model object. In our experiments a YAG:Nd laser generating picosecond pulses was employed. Output radiation has been recorded by a high speed streak camera with 1.5 ps temporal resolution. The high stability of the laser and of measurement scheme characteristics was provided. We looked for the contrasting substances having tropism with pathologically changed tissue of the tumor. For this purpose some dyphthalocyanines were synthesized. The experiments with laboratory animals have demonstrated that saturated dye concentrations were noticeably lower than toxicologic dangerous concentration values. We have demonstrated a possibility of the contrasting for a model object. The experimental temporal profile of scattered radiation can be explained by the nonstationary two-flow theory.

  15. Iodine contrast cone beam CT imaging of breast cancer

    NASA Astrophysics Data System (ADS)

    Partain, Larry; Prionas, Stavros; Seppi, Edward; Virshup, Gary; Roos, Gerhard; Sutherland, Robert; Boone, John

    2007-03-01

    An iodine contrast agent, in conjunction with an X-ray cone beam CT imaging system, was used to clearly image three, biopsy verified, cancer lesions in two patients. The lesions were approximately in the 10 mm to 6 mm diameter range. Additional regions were also enhanced with approximate dimensions down to 1 mm or less in diameter. A flat panel detector, with 194 μm pixels in 2 x 2 binning mode, was used to obtain 500 projection images at 30 fps with an 80 kVp X-ray system operating at 112 mAs, for an 8-9 mGy dose - equivalent to two view mammography for these women. The patients were positioned prone, while the gantry rotated in the horizontal plane around the uncompressed, pendant breasts. This gantry rotated 360 degrees during the patient's 16.6 sec breath hold. A volume of 100 cc of 320 mg/ml iodine-contrast was power injected at 4 cc/sec, via catheter into the arm vein of the patient. The resulting 512 x 512 x 300 cone beam CT data set of Feldkamp reconstructed ~(0.3 mm) 3 voxels were analyzed. An interval of voxel contrast values, characteristic of the regions with iodine contrast enhancement, were used with surface rendering to clearly identify up to a total of 13 highlighted volumes. This included the three largest lesions, that were previously biopsied and confirmed to be malignant. The other ten highlighted regions, of smaller diameters, are likely areas of increased contrast trapping unrelated to cancer angiogenesis. However the technique itself is capable of resolving lesions that small.

  16. Experimentally enhanced model-based deconvolution of propagation-based phase-contrast data

    NASA Astrophysics Data System (ADS)

    Pichotka, M.; Palma, K.; Hasn, S.; Jakubek, J.; Vavrik, D.

    2016-12-01

    In recent years phase-contrast has become a much investigated modality in radiographic imaging. The radiographic setups employed in phase-contrast imaging are typically rather costly and complex, e.g. high performance Talbot-Laue interferometers operated at synchrotron light sources. In-line phase-contrast imaging states the most pedestrian approach towards phase-contrast enhancement. Utilizing small angle deflection within the imaged sample and the entailed interference of the deflected and un-deflected beam during spatial propagation, in-line phase-contrast imaging only requires a well collimated X-ray source with a high contrast & high resolution detector. Employing high magnification the above conditions are intrinsically fulfilled in cone-beam micro-tomography. As opposed of 2D imaging, where contrast enhancement is generally considered beneficial, in tomographic modalities the in-line phase-contrast effect can be quite a nuisance since it renders the inverse problem posed by tomographic reconstruction inconsistent, thus causing reconstruction artifacts. We present an experimentally enhanced model-based approach to disentangle absorption and in-line phase-contrast. The approach employs comparison of transmission data to a system model computed iteratively on-line. By comparison of the forward model to absorption data acquired in continuous rotation strong local deviations of the data residual are successively identified as likely candidates for in-line phase-contrast. By inducing minimal vibrations (few mrad) to the sample around the peaks of such deviations the transmission signal can be decomposed into a constant absorptive fraction and an oscillating signal caused by phase-contrast which again allows to generate separate maps for absorption and phase-contrast. The contributions of phase-contrast and the corresponding artifacts are subsequently removed from the tomographic dataset. In principle, if a 3D handling of the sample is available, this method also

  17. Ultrasound Activated Contrast Imaging for Prostate Cancer Detection

    DTIC Science & Technology

    2005-03-01

    ultrasound engine with a P4-2 phased array transducer were modified to perform EEI on a vector-by-vector basis in fundamental and pulse inversion harmonic...albumin-encapsulated Abunex® bubble is 18 times greater than that for a free bubble if the two bubbles oscillate with the same relative amplitude at...utilizes two acoustic fields: the activation field for intermittently activating contrast bubbles and the imaging field, applied shortly afterwards, for

  18. Laboratory Demonstrations of High-contrast Imaging for Space Coronagraphy

    NASA Technical Reports Server (NTRS)

    Trauger, John; Giveon, Amir; Gordon, Brian; Kern, Brian; Krist, John; Kuhnert, Andreas; Moody, Dwight; Traub, Wes; Wilson, Dan

    2008-01-01

    This slide presentation reviews the use of the High Contrast Imaging Testbed (HCIT) in the design and improvement of space coronagraphs. The objectives of the work are to: (1) Advance the technology readiness of space coronagraph hardware, techniques, algorithms, and predictive models; (2) Provide proof-of-concept demonstrations of coronagraph techniques; and (3) Support collaborations across the exoplanet community in pursuit of the optimal space coronagraph architecture.

  19. The V-SHARK high contrast imager at LBT

    NASA Astrophysics Data System (ADS)

    Pedichini, F.; Ambrosino, F.; Centrone, M.; Farinato, J.; Li Causi, G.; Pinna, E.; Puglisi, A.; Stangalini, M.; Testa, V.

    2016-08-01

    In the framework of the SHARK project the visible channel is a novel instrument synergic to the NIR channel and exploiting the performances of the LBT XAO at visible wavelengths. The status of the project is presented together with the design study of this innovative instrument optimized for high contrast imaging by means of high frame rate. Its expected results will be presented comparing the simulations with the real data of the "Forerunner" experiment taken at 630nm.

  20. Nanoparticles in magnetic resonance imaging: from simple to dual contrast agents.

    PubMed

    Estelrich, Joan; Sánchez-Martín, María Jesús; Busquets, Maria Antònia

    2015-01-01

    Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T 1, spin-lattice relaxation and T 2, spin-spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T 1 and T 2 increases the corresponding relaxation rates, 1/T 1 and 1/T 2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T 2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T 1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents.

  1. Nanoparticles in magnetic resonance imaging: from simple to dual contrast agents

    PubMed Central

    Estelrich, Joan; Sánchez-Martín, María Jesús; Busquets, Maria Antònia

    2015-01-01

    Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T1, spin–lattice relaxation and T2, spin–spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T1 and T2 increases the corresponding relaxation rates, 1/T1 and 1/T2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents. PMID:25834422

  2. Simulations of multi-contrast x-ray imaging using near-field speckles

    SciTech Connect

    Zdora, Marie-Christine; Thibault, Pierre; Herzen, Julia; Pfeiffer, Franz; Zanette, Irene

    2016-01-28

    X-ray dark-field and phase-contrast imaging using near-field speckles is a novel technique that overcomes limitations inherent in conventional absorption x-ray imaging, i.e. poor contrast for features with similar density. Speckle-based imaging yields a wealth of information with a simple setup tolerant to polychromatic and divergent beams, and simple data acquisition and analysis procedures. Here, we present a simulation software used to model the image formation with the speckle-based technique, and we compare simulated results on a phantom sample with experimental synchrotron data. Thorough simulation of a speckle-based imaging experiment will help for better understanding and optimising the technique itself.

  3. Phase-contrast imaging using a scanning-double-grating configuration.

    PubMed

    Nesterets, Ya I; Wilkins, S W

    2008-04-14

    A new double-grating-based phase-contrast imaging technique is described. This technique differs from the conventional double-grating imaging method by the image acquisition strategy. The novelty of the proposed method is in lateral scanning of both gratings simultaneously while an image is collected. The collected image is not contaminated by a Moiré pattern and can be recorded even by using a high-spatial-resolution integrating detector (e.g. X-ray film), thus facilitating improved resolution and/or contrast in the image. A detailed theoretical analysis of image formation in the scanning-double-grating method is carried out within the rigorous wave-optical formalism. The transfer function for the scanning-double-grating imaging system is derived. An approximate geometrical-optics solution for the image intensity distribution is derived from the exact wave-optical formula using the stationary-phase approach. Based on the present formalism, the effects of finite source size on the preferred operating conditions and of polychromaticity on the image contrast and resolution are investigated.

  4. Single grating phase contrast imaging for x-ray microscopy and microtomography

    NASA Astrophysics Data System (ADS)

    Bruyndonckx, P.; Sasov, A.; Pauwels, B.

    2014-09-01

    The grating based approach to phase contrast imaging is rather inefficient in the use of the available x-ray flux due to the presence of two absorption gratings and it requires longer scan times compared to conventional CT because multiple images are needed at each projection angle. To avoid these drawbacks, a proof-of-principle experiment was developed to obtain absorption, phase contrast (DPC) and dark field images (DCI) in a single exposure using only a non-absorbing phase grating, a micro-focus source in cone-beam geometry and a highresolution x-ray detector.

  5. Dual-contrast MR imaging of liver cancer in rats.

    PubMed

    Weissleder, R; Saini, S; Stark, D D; Wittenberg, J; Ferrucci, J T

    1988-03-01

    MR contrast agents increase hepatic tumor conspicuity, as measured in terms of contrast-to-noise (C/N) ratios. With an animal model of hepatic metastases from breast cancer, IV administration of Gd-DTPA (0.2 mmol/kg) shows a biphasic time response, transiently increasing the signal intensity of liver relative to tumor, with C/N ratio magnitudes increasing from -5.7 to -16.3 (SE 250/20); after a delay, the signal intensity of tumor increases relative to liver with a reversal of the C/N sign from negative to positive and an increase in the C/N magnitude to +25.0. IV administration of ferrite particles (0.05 mmol Fe/kg) shows a monophasic time response, increasing signal intensity of tumor relative to liver from +1.5 to +49.5 (SE 500/30). When both contrast agents were administered together (dual-contrast technique), the tumor-liver C/N magnitude reached a maximum of +67.8 (SE 500/30) 12 min after drug infusion. Analysis of individual contrast and noise factors contributing to this technique revealed a strong correlation between the signal intensity of liver and the signal intensity of ghost artifacts, which increase after administration of Gd-DTPA (r = .89) and decrease after administration of ferrite (r = 1.0). Dual-contrast imaging shows a synergistic addition of contrast and suppression of noise from ghost artifacts, maximizing the C/N and increasing the conspicuity of focal liver lesions.

  6. Hyperpolarized water as an authentic magnetic resonance imaging contrast agent

    PubMed Central

    McCarney, Evan R.; Armstrong, Brandon D.; Lingwood, Mark D.; Han, Songi

    2007-01-01

    Pure water in a highly 1H spin-polarized state is proposed as a contrast-agent-free contrast agent to visualize its macroscopic evolution in aqueous media by MRI. Remotely enhanced liquids for image contrast (RELIC) utilizes a 1H signal of water that is enhanced outside the sample in continuous-flow mode and immediately delivered to the sample to obtain maximum contrast between entering and bulk fluids. Hyperpolarization suggests an ideal contrast mechanism to highlight the ubiquitous and specific function of water in physiology, biology, and materials because the physiological, chemical, and macroscopic function of water is not altered by the degree of magnetization. We present an approach that is capable of instantaneously enhancing the 1H MRI signal by up to 2 orders of magnitude through the Overhauser effect under ambient conditions at 0.35 tesla by using highly spin-polarized unpaired electrons that are covalently immobilized onto a porous, water-saturated gel matrix. The continuous polarization of radical-free flowing water allowed us to distinctively visualize vortices in model reactors and dispersion patterns through porous media. A 1H signal enhancement of water by a factor of −10 and −100 provides for an observation time of >4 and 7 s, respectively, upon its injection into fluids with a T1 relaxation time of >1.5 s. The implications for chemical engineering or biomedical applications of using hyperpolarized solvents or physiological fluids to visualize mass transport and perfusion with high and authentic MRI contrast originating from water itself, and not from foreign contrast agents, are immediate. PMID:17264210

  7. Flux or speed? Examining speckle contrast imaging of vascular flows

    PubMed Central

    Kazmi, S. M. Shams; Faraji, Ehssan; Davis, Mitchell A.; Huang, Yu-Yen; Zhang, Xiaojing J.; Dunn, Andrew K.

    2015-01-01

    Speckle contrast imaging enables rapid mapping of relative blood flow distributions using camera detection of back-scattered laser light. However, speckle derived flow measures deviate from direct measurements of erythrocyte speeds by 47 ± 15% (n = 13 mice) in vessels of various calibers. Alternatively, deviations with estimates of volumetric flux are on average 91 ± 43%. We highlight and attempt to alleviate this discrepancy by accounting for the effects of multiple dynamic scattering with speckle imaging of microfluidic channels of varying sizes and then with red blood cell (RBC) tracking correlated speckle imaging of vascular flows in the cerebral cortex. By revisiting the governing dynamic light scattering models, we test the ability to predict the degree of multiple dynamic scattering across vessels in order to correct for the observed discrepancies between relative RBC speeds and multi-exposure speckle imaging estimates of inverse correlation times. The analysis reveals that traditional speckle contrast imagery of vascular flows is neither a measure of volumetric flux nor particle speed, but rather the product of speed and vessel diameter. The corrected speckle estimates of the relative RBC speeds have an average 10 ± 3% deviation in vivo with those obtained from RBC tracking. PMID:26203384

  8. On Detailed Contrast of Biomedical Object in X-ray Dark-Field Imaging

    SciTech Connect

    Shimao, Daisuke; Mori, Koichi; Sugiyama, Hiroshi; Kunisada, Toshiyuki; Hyodo, Kazuyuki; Ando, Masami

    2007-01-19

    Over the past 10 years, refraction-based X-ray imaging has been studied together with a perspective view to clinical application. X-ray Dark-Field Imaging that utilizes a Laue geometry analyzer has recently been proposed and has the proven ability to depict articular cartilage in an intact human finger. In the current study, we researched detailed image contrast using X-ray Dark-Field Imaging by observing the edge contrast of an acrylic rod as a simple case, and found differences in image contrast between the right and left edges of the rod. This effect could cause undesirable contrast in the thin articular cartilage on the head of the phalanx. To avoid overlapping with this contrast at the articular cartilage, which would lead to a wrong diagnosis, we suggest that a joint surface on which articular cartilage is located should be aligned in the same sense as the scattering vector of the Laue case analyzer crystal. Defects of articular cartilage were successfully detected under this condition. When utilized under appropriate imaging conditions, X-ray Dark-Field Imaging will be a powerful tool for the diagnosis of arthropathy, as minute changes in articular cartilage may be early-stage features of this disease.

  9. Acoustic angiography: a new high frequency contrast ultrasound technique for biomedical imaging

    NASA Astrophysics Data System (ADS)

    Shelton, Sarah E.; Lindsey, Brooks D.; Gessner, Ryan; Lee, Yueh; Aylward, Stephen; Lee, Hyunggyun; Cherin, Emmanuel; Foster, F. Stuart; Dayton, Paul A.

    2016-05-01

    Acoustic Angiography is a new approach to high-resolution contrast enhanced ultrasound imaging enabled by ultra-broadband transducer designs. The high frequency imaging technique provides signal separation from tissue which does not produce significant harmonics in the same frequency range, as well as high resolution. This approach enables imaging of microvasculature in-vivo with high resolution and signal to noise, producing images that resemble x-ray angiography. Data shows that acoustic angiography can provide important information about the presence of disease based on vascular patterns, and may enable a new paradigm in medical imaging.

  10. Contrast-enhanced ultrasound for liver imaging: recent advances.

    PubMed

    Salvatore, Veronica; Borghi, Alberto; Piscaglia, Fabio

    2012-01-01

    Contrast-enhanced ultrasonography (CEUS), providing relevant informations not available with non-enhanced ultrasonography, greatly impacted the practice of liver imaging. The characterization of focal liver lesions (FLLs), is obtained in a rapid, accurate and safe way and is considered the main hepatic indication; however CEUS offers other established or emergent relevant applications. Metastases detection and assessment of response to locoregional tumor treatment are accepted applications with specific indications. Needle guidance in case of poorly or non visible target lesions at conventional ultrasound is also accepted. The early assessment of response to systemic treatment, and in particular to antiangiogenic ones, by quantification software is an emergent application. The manageability of CEUS determined also its use in the operating theatre, improving the accuracy of intraoperatory US with a significant impact on final surgical strategy. In cirrhotic patients, the role of CEUS was proven highly accurate and sensitive in the characterization of portal vein thrombosis, by identification of contrast arterial enhancement inside the thrombus, that occurs only in case of neoplastic origin. In recent years microbubbles taken up by Kupffer cells, thus possessing a "postvascular" phase, were registered as ultrasound contrast agent in Japan (Sonazoid). During the post-vascular phase tumoral tissue tend to appear as a contrast defect image due to the lack of Kupffer cells, strongly contributing to tumor staging beside characterization. Newly developed techniques, such as fusion imaging or real-time three dimensional US, in addition to other applications of CEUS, in terms of post-transplantation or cholecystitis-related complications, have been recently proposed and will be discussed.

  11. CW-THz image contrast enhancement using wavelet transform and Retinex

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Zhang, Min; Hu, Qi-fan; Huang, Ying-Xue; Liang, Hua-Wei

    2015-10-01

    To enhance continuous wave terahertz (CW-THz) scanning images contrast and denoising, a method based on wavelet transform and Retinex theory was proposed. In this paper, the factors affecting the quality of CW-THz images were analysed. Second, an approach of combination of the discrete wavelet transform (DWT) and a designed nonlinear function in wavelet domain for the purpose of contrast enhancing was applied. Then, we combine the Retinex algorithm for further contrast enhancement. To evaluate the effectiveness of the proposed method in qualitative and quantitative, it was compared with the adaptive histogram equalization method, the homomorphic filtering method and the SSR(Single-Scale-Retinex) method. Experimental results demonstrated that the presented algorithm can effectively enhance the contrast of CW-THZ image and obtain better visual effect.

  12. Results from the first preclinical CT scanner with grating based phase contrast and a rotating gantry

    NASA Astrophysics Data System (ADS)

    Bech, Martin; Tapfer, Arne; Velroyen, Astrid; Yaroshenko, Andre; Pauwels, Bart; Bruyndonckx, Peter; Liu, Xuan; Sasov, Alexander; Mohr, Jürgen; Walter, Marco; Pfeiffer, Franz

    2012-07-01

    After successful demonstrations of soft-tissue phase-contrast imaging with grating interferometers at synchrotron radiation sources and at laboratory based x-ray tubes, a first preclinical CT scanner with grating based phase contrast imaging modality has been constructed. The rotating gantry is equipped with a three-grating interferometer, a 50 watt tungsten anode source and a Hamamatsu flat panel detector. The total length of the interferometer is 45 cm, and the bed of the scanner is optimized for mice, with a scanning diameter of 35 mm. From one single scan both phase-contrast and standard attenuation based tomography can be attained, providing an overall gain in image contrast.

  13. Results from the first preclinical CT scanner with grating based phase contrast and a rotating gantry

    SciTech Connect

    Bech, Martin; Tapfer, Arne; Velroyen, Astrid; Yaroshenko, Andre; Pauwels, Bart; Bruyndonckx, Peter; Liu Xuan; Sasov, Alexander; Mohr, Juergen; Walter, Marco; Pfeiffer, Franz

    2012-07-31

    After successful demonstrations of soft-tissue phase-contrast imaging with grating interferometers at synchrotron radiation sources and at laboratory based x-ray tubes, a first preclinical CT scanner with grating based phase contrast imaging modality has been constructed. The rotating gantry is equipped with a three-grating interferometer, a 50 watt tungsten anode source and a Hamamatsu flat panel detector. The total length of the interferometer is 45 cm, and the bed of the scanner is optimized for mice, with a scanning diameter of 35 mm. From one single scan both phase-contrast and standard attenuation based tomography can be attained, providing an overall gain in image contrast.

  14. Noise properties of grating-based x-ray phase contrast computed tomography

    SciTech Connect

    Koehler, Thomas; Juergen Engel, Klaus; Roessl, Ewald

    2011-05-15

    Purpose: To investigate the properties of tomographic grating-based phase contrast imaging with respect to its noise power spectrum and the energy dependence of the achievable contrast to noise ratio. Methods: Tomographic simulations of an object with 11 cm diameter constituted of materials of biological interest were conducted at different energies ranging from 25 to 85 keV by using a wave propagation approach. Using a Monte Carlo simulation of the x-ray attenuation within the object, it is verified that the simulated measurement deposits the same dose within the object at each energy. Results: The noise in reconstructed phase contrast computed tomography images shows a maximum at low spatial frequencies. The contrast to noise ratio reaches a maximum around 45 keV for the simulated object. The general dependence of the contrast to noise on the energy appears to be independent of the material. Compared with reconstructed absorption contrast images, the reconstructed phase contrast images show sometimes better, sometimes worse, and sometimes similar contrast to noise, depending on the material and the energy. Conclusions: Phase contrast images provide additional information to the conventional absorption contrast images and might thus be useful for medical applications. However, the observed noise power spectrum in reconstructed phase contrast images implies that the usual trade-off between noise and resolution is less efficient for phase contrast imaging compared with absorption contrast imaging. Therefore, high-resolution imaging is a strength of phase contrast imaging, but low-resolution imaging is not. This might hamper the clinical application of the method, in cases where a low spatial resolution is sufficient for diagnosis.

  15. Optical lock-in detection imaging microscopy for contrast-enhanced imaging in living cells.

    PubMed

    Marriott, Gerard; Mao, Shu; Sakata, Tomoyo; Ran, Jing; Jackson, David K; Petchprayoon, Chutima; Gomez, Timothy J; Warp, Erica; Tulyathan, Orapim; Aaron, Holly L; Isacoff, Ehud Y; Yan, Yuling

    2008-11-18

    One of the limitations on imaging fluorescent proteins within living cells is that they are usually present in small numbers and need to be detected over a large background. We have developed the means to isolate specific fluorescence signals from background by using lock-in detection of the modulated fluorescence of a class of optical probe termed "optical switches." This optical lock-in detection (OLID) approach involves modulating the fluorescence emission of the probe through deterministic, optical control of its fluorescent and nonfluorescent states, and subsequently applying a lock-in detection method to isolate the modulated signal of interest from nonmodulated background signals. Cross-correlation analysis provides a measure of correlation between the total fluorescence emission within single pixels of an image detected over several cycles of optical switching and a reference waveform detected within the same image over the same switching cycles. This approach to imaging provides a means to selectively detect the emission from optical switch probes among a larger population of conventional fluorescent probes and is compatible with conventional microscopes. OLID using nitrospirobenzopyran-based probes and the genetically encoded Dronpa fluorescent protein are shown to generate high-contrast images of specific structures and proteins in labeled cells in cultured and explanted neurons and in live Xenopus embryos and zebrafish larvae.

  16. Effect of Radiation Dose Reduction and Reconstruction Algorithm on Image Noise, Contrast, Resolution, and Detectability of Subtle Hypoattenuating Liver Lesions at Multidetector CT: Filtered Back Projection versus a Commercial Model-based Iterative Reconstruction Algorithm.

    PubMed

    Solomon, Justin; Marin, Daniele; Roy Choudhury, Kingshuk; Patel, Bhavik; Samei, Ehsan

    2017-02-07

    Purpose To determine the effect of radiation dose and iterative reconstruction (IR) on noise, contrast, resolution, and observer-based detectability of subtle hypoattenuating liver lesions and to estimate the dose reduction potential of the IR algorithm in question. Materials and Methods This prospective, single-center, HIPAA-compliant study was approved by the institutional review board. A dual-source computed tomography (CT) system was used to reconstruct CT projection data from 21 patients into six radiation dose levels (12.5%, 25%, 37.5%, 50%, 75%, and 100%) on the basis of two CT acquisitions. A series of virtual liver lesions (five per patient, 105 total, lesion-to-liver prereconstruction contrast of -15 HU, 12-mm diameter) were inserted into the raw CT projection data and images were reconstructed with filtered back projection (FBP) (B31f kernel) and sinogram-affirmed IR (SAFIRE) (I31f-5 kernel). Image noise (pixel standard deviation), lesion contrast (after reconstruction), lesion boundary sharpness (average normalized gradient at lesion boundary), and contrast-to-noise ratio (CNR) were compared. Next, a two-alternative forced choice perception experiment was performed (16 readers [six radiologists, 10 medical physicists]). A linear mixed-effects statistical model was used to compare detection accuracy between FBP and SAFIRE and to estimate the radiation dose reduction potential of SAFIRE. Results Compared with FBP, SAFIRE reduced noise by a mean of 53% ± 5, lesion contrast by 12% ± 4, and lesion sharpness by 13% ± 10 but increased CNR by 89% ± 19. Detection accuracy was 2% higher on average with SAFIRE than with FBP (P = .03), which translated into an estimated radiation dose reduction potential (±95% confidence interval) of 16% ± 13. Conclusion SAFIRE increases detectability at a given radiation dose (approximately 2% increase in detection accuracy) and allows for imaging at reduced radiation dose (16% ± 13), while maintaining low-contrast

  17. Optimisation of image reconstruction for phase-contrast x-ray Talbot-Lau imaging with regard to mechanical robustness

    NASA Astrophysics Data System (ADS)

    Seifert, M.; Kaeppler, S.; Hauke, C.; Horn, F.; Pelzer, G.; Rieger, J.; Michel, T.; Riess, C.; Anton, G.

    2016-09-01

    X-ray grating-based phase-contrast imaging opens new opportunities, inter alia, in medical imaging and non-destructive testing. Because, information about the attenuation properties and about the refractive properties of an object are gained simultaneously. Talbot-Lau imaging requires the knowledge of a reference or free-field image. The long-term stability of a Talbot-Lau interferometer is related to the time span of the validity of a measured reference image. It would be desirable to keep the validity of the reference image for a day or longer to improve feasibility of Talbot-Lau imaging. However, for example thermal and other long-term external influences result in drifting effects of the phase images. Therefore, phases are shifting over time and the reference image is not valid for long-term measurements. Thus, artifacts occur in differential phase-contrast images. We developed an algorithm to determine the differential phase-contrast image with the help of just one calibration image, which is valid for a long time-period. With the help of this algorithm, called phase-plane-fit method, it is possible to save measurement-time, as it is not necessary to take a reference image for each measurement. Additionally, transferring the interferometer technique from laboratory setups to conventional imaging systems the necessary rigidity of the system is difficult to achieve. Therefore, short-term effects like vibrations or distortions of the system lead to imperfections within the phase-stepping procedure. Consequently, artifacts occur in all three image modalities (differential phase-contrast image, attenuation image and dark-field image) of Talbot-Lau imaging. This is a problem with regard to the intended use of phase-contrast imaging for example in clinical routine or non-destructive testing. In this publication an algorithm of Vargas et al is applied and complemented to correct inaccurate phase-step positions with the help of a principal component analysis (PCA

  18. Contrast agent stability: a continuous B-mode imaging approach.

    PubMed

    Sboros, V; Moran, C M; Pye, S D; McDicken, W N

    2001-10-01

    The stability of contrast agents in suspensions with various dissolved gas levels has not been reported in the literature. An in vitro investigation has been carried out that studied the combined effect of varying the acoustic pressure along with degassing the suspension environment. In this study, the contrast agents were introduced into suspensions with different oxygen concentration levels, and their relative performance was assessed in terms of decay rate of their backscatter echoes. The partial pressures of oxygen in those solutions ranged between 1.5 and 26 kPa. Two IV and one arterial contrast agents were used: Definity, Quantison, and Myomap. It was found that Quantison and Myomap released free bubbles at high acoustic pressure that also dissolved faster in degassed suspensions. The backscatter decay for Definity did not depend on the air content of the suspensions. The destruction of bubbles was dependent on acoustic pressure. Different backscatter performance was observed by different populations of bubbles of the last two agents. The physical quantity of "overall backscatter" (OB) was defined as the integral of the decay rate over time of the backscatter of the contrast suspensions, and improved significantly the understanding of the behaviour of the agents. A quantitative analysis of the backscatter properties of contrast agents using a continuous imaging approach was difficult to achieve. This is due to the fact that the backscatter in the field of view is representative of a bubble population affected by the ultrasound (US) field, but this bubble population is not representative of the contrast suspension in the whole tank. Single frame insonation is suggested to avoid the effects of decay due to the ultrasonic field, and to measure a tank-representative backscatter. The definition of OB was useful, however, in understanding the behaviour of the agents.

  19. Motionless phase stepping in X-ray phase contrast imaging with a compact source

    PubMed Central

    Miao, Houxun; Chen, Lei; Bennett, Eric E.; Adamo, Nick M.; Gomella, Andrew A.; DeLuca, Alexa M.; Patel, Ajay; Morgan, Nicole Y.; Wen, Han

    2013-01-01

    X-ray phase contrast imaging offers a way to visualize the internal structures of an object without the need to deposit significant radiation, and thereby alleviate the main concern in X-ray diagnostic imaging procedures today. Grating-based differential phase contrast imaging techniques are compatible with compact X-ray sources, which is a key requirement for the majority of clinical X-ray modalities. However, these methods are substantially limited by the need for mechanical phase stepping. We describe an electromagnetic phase-stepping method that eliminates mechanical motion, thus removing the constraints in speed, accuracy, and flexibility. The method is broadly applicable to both projection and tomography imaging modes. The transition from mechanical to electromagnetic scanning should greatly facilitate the translation of X-ray phase contrast techniques into mainstream applications. PMID:24218599

  20. The use of contrast agent for imaging biological samples

    NASA Astrophysics Data System (ADS)

    Dammer, J.; Weyda, F.; Sopko, V.; Jakubek, J.

    2011-01-01

    The technique of X-ray transmission imaging has been available for over a century and is still among the fastest and easiest approaches to the studies of internal structure of biological samples. Recent advances in semiconductor technology have led to the development of new types of X-ray detectors with direct conversion of interacting X-ray photon to an electric signal. Semiconductor pixel detectors seem to be specially promising; compared to the film technique, they provide single-quantum and real-time digital information about the objects being studied. We describe the recently developed radiographic apparatus, equipped with Medipix2 semiconductor pixel detector. The detector is used as an imager that counts individual photons of ionizing radiation, emitted by an X-ray tube (micro- or nano-focus FeinFocus). Thanks to the wide dynamic range of the Medipix2 detector and its high spatial resolution better than 1μm, the setup is particularly suitable for radiographic imaging of small biological samples, including in-vivo observations with contrast agent (Optiray). Along with the description of the apparatus we provide examples of the use iodine contrast agent as a tracer in various insects as model organisms. The motivation of our work is to develop our imaging techniques as non-destructive and non-invasive. Microradiographic imaging helps detect organisms living in a not visible environment, visualize the internal biological processes and also to resolve the details of their body (morphology). Tiny live insects are an ideal object for our studies.

  1. Ultrasound imaging beyond the vasculature with new generation contrast agents.

    PubMed

    Perera, Reshani H; Hernandez, Christopher; Zhou, Haoyan; Kota, Pavan; Burke, Alan; Exner, Agata A

    2015-01-01

    Current commercially available ultrasound contrast agents are gas-filled, lipid- or protein-stabilized microbubbles larger than 1 µm in diameter. Because the signal generated by these agents is highly dependent on their size, small yet highly echogenic particles have been historically difficult to produce. This has limited the molecular imaging applications of ultrasound to the blood pool. In the area of cancer imaging, microbubble applications have been constrained to imaging molecular signatures of tumor vasculature and drug delivery enabled by ultrasound-modulated bubble destruction. Recently, with the rise of sophisticated advancements in nanomedicine, ultrasound contrast agents, which are an order of magnitude smaller (100-500 nm) than their currently utilized counterparts, have been undergoing rapid development. These agents are poised to greatly expand the capabilities of ultrasound in the field of targeted cancer detection and therapy by taking advantage of the enhanced permeability and retention phenomenon of many tumors and can extravasate beyond the leaky tumor vasculature. Agent extravasation facilitates highly sensitive detection of cell surface or microenvironment biomarkers, which could advance early cancer detection. Likewise, when combined with appropriate therapeutic agents and ultrasound-mediated deployment on demand, directly at the tumor site, these nanoparticles have been shown to contribute to improved therapeutic outcomes. Ultrasound's safety profile, broad accessibility and relatively low cost make it an ideal modality for the changing face of healthcare today. Aided by the multifaceted nano-sized contrast agents and targeted theranostic moieties described herein, ultrasound can considerably broaden its reach in future applications focused on the diagnosis and staging of cancer.

  2. X-ray Phase Contrast Allows Three Dimensional, Quantitative Imaging of Hydrogel Implants

    DOE PAGES

    Appel, Alyssa A.; Larson, Jeffrey C.; Jiang, Bin; ...

    2015-10-20

    Three dimensional imaging techniques are needed for the evaluation and assessment of biomaterials used for tissue engineering and drug delivery applications. Hydrogels are a particularly popular class of materials for medical applications but are difficult to image in tissue using most available imaging modalities. Imaging techniques based on X-ray Phase Contrast (XPC) have shown promise for tissue engineering applications due to their ability to provide image contrast based on multiple X-ray properties. In this manuscript we describe results using XPC to image a model hydrogel and soft tissue structure. Porous fibrin loaded poly(ethylene glycol) hydrogels were synthesized and implanted inmore » a rodent subcutaneous model. Samples were explanted and imaged with an analyzer-based XPC technique and processed and stained for histology for comparison. Both hydrogel and soft tissues structures could be identified in XPC images. Structure in skeletal muscle adjacent could be visualized and invading fibrovascular tissue could be quantified. In quantitative results, there were no differences between XPC and the gold-standard histological measurements. These results provide evidence of the significant potential of techniques based on XPC for 3D imaging of hydrogel structure and local tissue response.« less

  3. X-ray Phase Contrast Allows Three Dimensional, Quantitative Imaging of Hydrogel Implants

    SciTech Connect

    Appel, Alyssa A.; Larson, Jeffrey C.; Jiang, Bin; Zhong, Zhong; Anastasio, Mark A.; Brey, Eric M.

    2015-10-20

    Three dimensional imaging techniques are needed for the evaluation and assessment of biomaterials used for tissue engineering and drug delivery applications. Hydrogels are a particularly popular class of materials for medical applications but are difficult to image in tissue using most available imaging modalities. Imaging techniques based on X-ray Phase Contrast (XPC) have shown promise for tissue engineering applications due to their ability to provide image contrast based on multiple X-ray properties. In this manuscript we describe results using XPC to image a model hydrogel and soft tissue structure. Porous fibrin loaded poly(ethylene glycol) hydrogels were synthesized and implanted in a rodent subcutaneous model. Samples were explanted and imaged with an analyzer-based XPC technique and processed and stained for histology for comparison. Both hydrogel and soft tissues structures could be identified in XPC images. Structure in skeletal muscle adjacent could be visualized and invading fibrovascular tissue could be quantified. In quantitative results, there were no differences between XPC and the gold-standard histological measurements. These results provide evidence of the significant potential of techniques based on XPC for 3D imaging of hydrogel structure and local tissue response.

  4. Screening CEST contrast agents using ultrafast CEST imaging

    NASA Astrophysics Data System (ADS)

    Xu, Xiang; Yadav, Nirbhay N.; Song, Xiaolei; McMahon, Michael T.; Jerschow, Alexej; van Zijl, Peter C. M.; Xu, Jiadi

    2016-04-01

    A chemical exchange saturation transfer (CEST) experiment can be performed in an ultrafast fashion if a gradient field is applied simultaneously with the saturation pulse. This approach has been demonstrated for studying dia- and para-magnetic CEST agents, hyperpolarized Xe gas and in vivo spectroscopy. In this study we present a simple method for the simultaneous screening of multiple samples. Furthermore, by interleaving a number of saturation and readout periods within the TR, a series of images with different saturation times can be acquired, allowing for the quantification of exchange rates using the variable saturation time (QUEST) approach in a much accelerated fashion, thus enabling high throughput screening of CEST contrast agents.

  5. Modeling contrast agent flow in cerebral aneurysms: comparison of CFD with medical imaging

    NASA Astrophysics Data System (ADS)

    Rayz, Vitaliy; Vali, Alireza; Sigovan, Monica; Lawton, Michael; Saloner, David; Boussel, Loic

    2016-11-01

    PURPOSE: The flow in cerebral aneurysms is routinely assessed with X-ray angiography, an imaging technique based on a contrast agent injection. In addition to requiring a patient's catheterization and radiation exposure, the X-ray angiography may inaccurately estimate the flow residence time, as the injection alters the native blood flow patterns. Numerical modeling of the contrast transport based on MRI imaging, provides a non-invasive alternative for the flow diagnostics. METHODS: The flow in 3 cerebral aneurysms was measured in vivo with 4D PC-MRI, which provides time-resolved, 3D velocity field. The measured velocities were used to simulate a contrast agent transport by solving the advection-diffusion equation. In addition, the flow in the same patient-specific geometries was simulated with CFD and the velocities obtained from the Navier-Stokes solution were used to model the transport of a virtual contrast. RESULTS: Contrast filling and washout patterns obtained in simulations based on MRI-measured velocities were in agreement with those obtained using the Navier-Stokes solution. Some discrepancies were observed in comparison to the X-ray angiography data, as numerical modeling of the contrast transport is based on the native blood flow unaffected by the contrast injection. NIH HL115267.

  6. Contrast-enhanced harmonic endoscopic ultrasound imaging: basic principles, present situation and future perspectives.

    PubMed

    Alvarez-Sánchez, María-Victoria; Napoléon, Bertrand

    2014-11-14

    Over the last decade, the development of stabilised microbubble contrast agents and improvements in available ultrasonic equipment, such as harmonic imaging, have enabled us to display microbubble enhancements on a greyscale with optimal contrast and spatial resolution. Recent technological advances made contrast harmonic technology available for endoscopic ultrasound (EUS) for the first time in 2008. Thus, the evaluation of microcirculation is now feasible with EUS, prompting the evolution of contrast-enhanced EUS from vascular imaging to images of the perfused tissue. Although the relevant experience is still preliminary, several reports have highlighted contrast-enhanced harmonic EUS (CH-EUS) as a promising noninvasive method to visualise and characterise lesions and to differentiate benign from malignant focal lesions. Even if histology remains the gold standard, the combination of CH-EUS and EUS fine needle aspiration (EUS-FNA) can not only render EUS more accurate but may also assist physicians in making decisions when EUS-FNA is inconclusive, increasing the yield of EUS-FNA by guiding the puncture with simultaneous imaging of the vascularity. The development of CH-EUS has also opened up exciting possibilities in other research areas, including monitoring responses to anticancer chemotherapy or to ethanol-induced pancreatic tissue ablation, anticancer therapies based on ultrasound-triggered drug and gene delivery, and therapeutic adjuvants by contrast ultrasound-induced apoptosis. Contrast harmonic imaging is gaining popularity because of its efficacy, simplicity and non-invasive nature, and many expectations are currently resting on this technique. If its potential is confirmed in the near future, contrast harmonic imaging will become a standard practice in EUS.

  7. Evaluation of a new reconstruction algorithm for x-ray phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Seifert, Maria; Hauke, Christian; Horn, Florian; Lachner, Sebastian; Ludwig, Veronika; Pelzer, Georg; Rieger, Jens; Schuster, Max; Wandner, Johannes; Wolf, Andreas; Michel, Thilo; Anton, Gisela

    2016-04-01

    X-ray grating-based phase-contrast imaging might open up entirely new opportunities in medical imaging. However, transferring the interferometer technique from laboratory setups to conventional imaging systems the necessary rigidity of the system is difficult to achieve. Therefore, vibrations or distortions of the system lead to inaccuracies within the phase-stepping procedure. Given insufficient stability of the phase-step positions, up to now, artifacts in phase-contrast images occur, which lower the image quality. This is a problem with regard to the intended use of phase-contrast imaging in clinical routine as for example tiny structures of the human anatomy cannot be observed. In this contribution we evaluate an algorithm proposed by Vargas et.al.1 and applied to X-ray imaging by Pelzer et.al. that enables us to reconstruct a differential phase-contrast image without the knowledge of the specific phase-step positions. This method was tested in comparison to the standard reconstruction by Fourier analysis. The quality of phase-contrast images remains stable, even if the phase-step positions are completely unknown and not uniformly distributed. To also achieve attenuation and dark-field images the proposed algorithm has been combined with a further algorithm of Vargas et al.3 Using this algorithm, the phase-step positions can be reconstructed. With the help of the proper phase-step positions it is possible to get information about the phase, the amplitude and the offset of the measured data. We evaluated this algorithm concerning the measurement of thick objects which show a high absorbency.

  8. Immobilized contrast-enhanced MRI: Gadolinium-based long-term MR contrast enhancement of the vein graft vessel wall.

    PubMed

    Mitsouras, Dimitris; Vemula, Praveen Kumar; Yu, Peng; Tao, Ming; Nguyen, Binh T; Campagna, Christina M; Karp, Jeffrey M; Mulkern, Robert V; Ozaki, C Keith; Rybicki, Frank J

    2011-01-01

    An implantable MR contrast agent that can be covalently immobilized on tissue during surgery has been developed. The rationale is that a durable increase in tissue contrast using an implantable contrast agent can enhance postsurgical tissue differentiation using MRI. For small-vessel (e.g., vein graft) MRI, the direct benefit of such permanent "labeling" of the vessel wall by modification of its relaxation properties is to achieve more efficient imaging. This efficiency can be realized as either increased contrast leading to more accurate delineation of vessel wall and lesion tissue boundaries, or, faster imaging without penalizing contrast-to-noise ratio, or a combination thereof. We demonstrate, for the first time, stable long-term MRI enhancement using such an exogenous contrast mechanism based on immobilizing a modified diethylenetriaminepentaacetic acid gadolinium(3+) dihydrogen complex on a human vein using a covalent amide bond. Signal enhancement due to the covalently immobilized contrast agent is demonstrated for excised human vein specimens imaged at 3 T, and its long-term stability is demonstrated during a 4-month incubation period.

  9. Fluorine-19 MRI Contrast Agents for Cell Tracking and Lung Imaging

    PubMed Central

    Fox, Matthew S.; Gaudet, Jeffrey M.; Foster, Paula J.

    2015-01-01

    Fluorine-19 (19F)-based contrast agents for magnetic resonance imaging stand to revolutionize imaging-based research and clinical trials in several fields of medical intervention. First, their use in characterizing in vivo cell behavior may help bring cellular therapy closer to clinical acceptance. Second, their use in lung imaging provides novel noninvasive interrogation of the ventilated airspaces without the need for complicated, hard-to-distribute hardware. This article reviews the current state of 19F-based cell tracking and lung imaging using magnetic resonance imaging and describes the link between the methods across these fields and how they may mutually benefit from solutions to mutual problems encountered when imaging 19F-containing compounds, as well as hardware and software advancements. PMID:27042089

  10. Evaluation of imaging characteristics in CTDI phantom size on contrast imaging

    NASA Astrophysics Data System (ADS)

    Jeon, Pil-Hyun; Lee, Won-Hyung; Jeon, Seong-Su; Kim, Hee-Joung

    2015-03-01

    Recently, there have been several physics and clinical studies on the use of lower tube potentials in CT imaging, with the purpose of improving image quality or further reducing radiation dose. We investigated an experimental study using a series of different sized, polymethyl methacrylate (PMMA) phantoms, demonstrating the potential strategy for dose reduction and to distinguish component of plaque by imaging their energy responses using CT. We investigated the relationship between different sizes of cylinderic PMMA-equivalent phantoms with diameter of 12, 16, 20, 24, and 32 cm and used contrast at various tube voltages (80, 100, 120, and 140 kVp) using a 16-detector row CT scanner. The contrast represented CT numbers as different materials for the water, calcium chloride, and iodine. Phantom insertions also allow quantitative measures of image noise, contrast, contrast-to-noise ratio (CNR) and figure of merit (FOM). When evaluating FOM, it was found that the lower kVp provided the better CNR. An experimental study was performed to demonstrate reduced dose for both dose efficient and practical feasibility for different patient sizes and diagnostic tasks by relating achievable CNR and the volume CT dose index (CTDIvol). The use of spectra optimized to the specific application could provide further improvements of distinguishing iodine, calcium and plaque component for patient size. The purpose of this study was to evaluate variations in image noise and contrast using different tube potentials in a CTDI phantom on contrast imaging.

  11. Effects of gadolinium-based contrast agent concentrations (0.5 M or 1.0 M) on the diagnostic performance of magnetic resonance imaging examinations: systematic review of the literature.

    PubMed

    Lancelot, Eric; Froehlich, John; Heine, Oliver; Desché, Pierre

    2016-11-01

    Background To date there is no agreement as to what is the optimal concentration for gadolinium-based contrast agents (GBCAs). Purpose To assess whether diagnostic performance differences exist between 0.5 M and 1.0 M GBCAs used for magnetic resonance imaging (MRI). Material and Methods A PubMed literature search identified 21 clinical studies published between 2005 and 2013 which evaluated the diagnostic efficacy of both types of GBCAs. Study design, type of procedure, GBCA administration mode, imaging performances, impact on patient management, study limitations, and biases were analyzed. No statistical test was performed on pooled data. Results Sixteen comparative and five non-comparative studies were analyzed, involving 2183 patients who underwent MRI procedures for various indications. In 67% of the studies, 0.5 M and 1.0 M GBCAs were injected at equimolar gadolinium amounts per kg body weight. Only 33% applied the same molar flow rate for delivery of the GBCAs. No significant differences between GBCAs were reported for 23 out of 27 qualitative endpoints (mainly image quality, lesion, and vessel visualization) and 29 out of 40 quantitative endpoints. Three out of four studies with non-equimolar delivery rates showed better contrast-to-noise and signal-to-noise ratios for 1.0 M gadobutrol, without showing an impact on diagnostic performance. Methodological biases were identified in several studies impairing the interpretation of comparisons. Conclusion Imaging differences between 0.5 M and 1.0 M GBCAs were essentially observed under non-equimolar delivery rates. However, they did not result into greater diagnostic efficacy when performed under equimolar conditions.

  12. Local scattering property scales flow speed estimation in laser speckle contrast imaging

    NASA Astrophysics Data System (ADS)

    Miao, Peng; Chao, Zhen; Feng, Shihan; Yu, Hang; Ji, Yuanyuan; Li, Nan; Thakor, Nitish V.

    2015-07-01

    Laser speckle contrast imaging (LSCI) has been widely used in in vivo blood flow imaging. However, the effect of local scattering property (scattering coefficient µ s ) on blood flow speed estimation has not been well investigated. In this study, such an effect was quantified and involved in relation between speckle autocorrelation time τ c and flow speed v based on simulation flow experiments. For in vivo blood flow imaging, an improved estimation strategy was developed to eliminate the estimation bias due to the inhomogeneous distribution of the scattering property. Compared to traditional LSCI, a new estimation method significantly suppressed the imaging noise and improves the imaging contrast of vasculatures. Furthermore, the new method successfully captured the blood flow changes and vascular constriction patterns in rats’ cerebral cortex from normothermia to mild and moderate hypothermia.

  13. 75 FR 875 - Guidance for Industry on New Contrast Imaging Indication Considerations for Devices and Approved...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ... HUMAN SERVICES Food and Drug Administration Guidance for Industry on New Contrast Imaging Indication... availability of a guidance for industry entitled ``New Contrast Imaging Indication Considerations for Devices..., FDA agreed to publish guidance for medical imaging devices for use with imaging contrast agents...

  14. Phase contrast imaging simulation and measurements using polychromatic sources with small source-object distances

    SciTech Connect

    Golosio, Bruno; Carpinelli, Massimo; Masala, Giovanni Luca; Oliva, Piernicola; Stumbo, Simone; Delogu, Pasquale; Zanette, Irene; Stefanini, Arnaldo

    2008-11-01

    Phase contrast imaging is a technique widely used in synchrotron facilities for nondestructive analysis. Such technique can also be implemented through microfocus x-ray tube systems. Recently, a relatively new type of compact, quasimonochromatic x-ray sources based on Compton backscattering has been proposed for phase contrast imaging applications. In order to plan a phase contrast imaging system setup, to evaluate the system performance and to choose the experimental parameters that optimize the image quality, it is important to have reliable software for phase contrast imaging simulation. Several software tools have been developed and tested against experimental measurements at synchrotron facilities devoted to phase contrast imaging. However, many approximations that are valid in such conditions (e.g., large source-object distance, small transverse size of the object, plane wave approximation, monochromatic beam, and Gaussian-shaped source focal spot) are not generally suitable for x-ray tubes and other compact systems. In this work we describe a general method for the simulation of phase contrast imaging using polychromatic sources based on a spherical wave description of the beam and on a double-Gaussian model of the source focal spot, we discuss the validity of some possible approximations, and we test the simulations against experimental measurements using a microfocus x-ray tube on three types of polymers (nylon, poly-ethylene-terephthalate, and poly-methyl-methacrylate) at varying source-object distance. It will be shown that, as long as all experimental conditions are described accurately in the simulations, the described method yields results that are in good agreement with experimental measurements.

  15. Laser speckle contrast imaging to measure changes in cerebral blood flow.

    PubMed

    Winship, Ian R

    2014-01-01

    Laser speckle contrast imaging (LSCI) is a powerful tool capable of acquiring detailed maps of blood flow in arteries and veins on the cortical surface. Based on the blurring of laser speckle patterns by the motion of blood cells, LSCI can be combined with a variety of optical imaging preparations to acquire high-spatiotemporal resolution images of blood flow, and track changes in blood flow over time, using relatively simple instrumentation. Here, we describe methods for LSCI of cerebral blood flow via a thin skull imaging preparation in mice or rats. This preparation allows precise semiquantitative mapping of changes in blood flow over time using straightforward surgical protocols and equipment.

  16. Molecular photoacoustic imaging using gold nanoparticles as a contrast agent

    NASA Astrophysics Data System (ADS)

    Kim, Chulhong; Cho, Eun Chul; Chen, Jingyi; Song, Kwang Hyun; Au, Leslie; Favazza, Christopher P.; Zhang, Qiang; Cobley, Claire M.; Xia, Younan; Wang, Lihong V.

    2010-02-01

    Gold nanoparticles have received much attention due to their potential diagnostic and therapeutic applications. Gold nanoparticles are attractive in many biomedical applications because of their biocompatibility, easily modifiable surfaces for targeting, lack of heavy metal toxicity, wide range of sizes (35-100 nm), tunable plasmonic resonance peak, encapsulated site-specific drug delivery, and strong optical absorption in the near-infrared regime. Specifically, due to their strong optical absorption, gold nanoparticles have been used as a contrast agent for molecular photoacoustic (PA) imaging of tumor. The plasmonic resonance peak of the gold nanocages (AuNCs) was tuned to the near-infrared region, and the ratio of the absorption cross-section to the extinction cross-section was approximately ~70%, as measured by PA sensing. We used PEGylated gold nanocages (PEG-AuNCs) as a passive targeting contrast agent on melanomas. After 6-h intravenous injection of PEG-AuNCs, PA amplitude was increased by ~14 %. These results strongly suggest PA imaging paired with AuNCs is a promising diagnostic tool for early cancer detection.

  17. Vascular flow and perfusion imaging with ultrasound contrast agents.

    PubMed

    Bruce, Matthew; Averkiou, Mike; Tiemann, Klaus; Lohmaier, Stefan; Powers, Jeff; Beach, Kirk

    2004-06-01

    Current techniques for imaging ultrasound (US) contrast agents (UCA) make no distinction between low-velocity microbubbles in the microcirculation and higher-velocity microbubbles in the larger vasculature. A combination of radiofrequency (RF) and Doppler filtering on a low mechanical index (MI) pulse inversion acquisition is presented that differentiates low-velocity microbubbles (on the order of mm/s) associated with perfusion, from the higher-velocity microbubbles (on the order of cm/s) in larger vessels. In vitro experiments demonstrate the ability to separate vascular flow using both harmonic and fundamental Doppler signals. Fundamental and harmonic Doppler signals from microbubbles using a low-MI pulse-inversion acquisition are compared with conventional color Doppler signals in vivo. Due to the lower transmit amplitude and enhanced backscatter from microbubbles, the in vivo signal to clutter ratios for both the fundamental (-11 dB) and harmonic (-4 dB) vascular flow signals were greater than with conventional power Doppler (-51 dB) without contrast agent. The processing investigated here, in parallel with conventional pulse-inversion processing, enables the simultaneous display of both perfusion and vascular flow. In vivo results demonstrating the feasibility and potential utility of the real-time display of both perfusion and vascular flow using US contrast agents are presented and discussed.

  18. Modeled and measured image-plane polychromatic speckle contrast

    NASA Astrophysics Data System (ADS)

    Van Zandt, Noah R.; McCrae, Jack E.; Fiorino, Steven T.

    2016-02-01

    The statistical properties of speckle relevant to short- to medium-range (tactical) active tracking involving polychromatic illumination are investigated. A numerical model is developed to allow rapid simulation of speckled images including the speckle contrast reduction effects of illuminator bandwidth, surface slope, and roughness, and the polarization properties of both the source and the reflection. Regarding surface slope (relative orientation of the surface normal and illumination/observation directions), Huntley's theory for speckle contrast, which employs geometrical approximations to decrease computation time, is modified to increase accuracy by incorporation of a geometrical correction factor and better treatment of roughness and polarization. The resulting model shows excellent agreement with more exact theory over a wide range. An experiment is conducted to validate both the numerical model developed here and existing theory. A diode laser source with coherence length of 259±7 μm is reflected off of a silver-coated diffuse surface. Speckle data are gathered for 16 surface slope angles corresponding to speckle contrast between about 0.55 and 1. Taking the measured data as truth, both equations show error mean and standard deviation of less than 3%. Thus, the theory is validated over the range of this experiment.

  19. Flow quantification with nakagami parametric imaging for suppressing contrast microbubbles attenuation.

    PubMed

    Gu, Xiaolin; Wei, Min; Zong, Yujin; Jiang, Hujie; Wan, Mingxi

    2013-04-01

    Flow quantification with contrast-enhanced ultrasound is still limited by the effects of contrast microbubble attenuation. Nakagami parametric imaging (NPI) based on the m parameter, which is related to the statistical property of echo envelope, is implemented to suppress contrast attenuation. Flow velocity (FV) and volumetric flow rate (VFR) are estimated through the least square fitting of burst depletion kinetic model to time m parameter curves (TMCs). A non-recirculating flow phantom is imaged as contrast microbubbles are infused at 10, 15, 20, 25, and 30 mL/min. Contrast microbubbles with two different concentrations are used to generate variations of contrast microbubble attenuation. The results suggest that 4 × 4 mm(2) is the optimal size of a sliding window of NPI for flow quantification under current experiment condition. At a lower microbubble concentration, the FV calculated from TMCs correlates strongly with actual FV in both unattenuated (R(2) = 0.97; p < 0.01) and attenuated regions (R(2) = 0.92; p < 0.01) within phantom. And there is a strong correlation (R(2) = 0.98; p < 0.01; slope = 0.96; intercept = 0.68) between VFR calculated from TMCs and actual VFR within the whole phantom. Similar results are obtained at higher microbubble concentrations. Compared with conventional ultrasound imaging that is intensity dependent, NPI achieves better performance on flow quantification in the presence of contrast microbubble attenuation.

  20. Encapsulated microbubbles and echogenic liposomes for contrast ultrasound imaging and targeted drug delivery

    PubMed Central

    Paul, Shirshendu; Nahire, Rahul; Mallik, Sanku; Sarkar, Kausik

    2014-01-01

    Micron- to nanometer-sized ultrasound agents, like encapsulated microbubbles and echogenic liposomes, are being developed for diagnostic imaging and ultrasound mediated drug/gene delivery. This review provides an overview of the current state of the art of the mathematical models of the acoustic behavior of ultrasound contrast microbubbles. We also present a review of the in vitro experimental characterization of the acoustic properties of microbubble based contrast agents undertaken in our laboratory. The hierarchical two-pronged approach of modeling contrast agents we developed is demonstrated for a lipid coated (Sonazoid™) and a polymer shelled (poly D-L-lactic acid) contrast microbubbles. The acoustic and drug release properties of the newly developed echogenic liposomes are discussed for their use as simultaneous imaging and drug/gene delivery agents. Although echogenicity is conclusively demonstrated in experiments, its physical mechanisms remain uncertain. Addressing questions raised here will accelerate further development and eventual clinical approval of these novel technologies. PMID:26097272

  1. Lensless phase contrast microscopy based on multiwavelength Fresnel diffraction.

    PubMed

    Noom, Daniel W E; Eikema, Kjeld S E; Witte, Stefan

    2014-01-15

    We demonstrate a compact, wide-field, quantitative phase contrast microscope that does not require lenses for image formation. High-resolution images are retrieved from Fresnel diffraction patterns recorded at multiple wavelengths, combined with a robust iterative phase retrieval algorithm. Quantitative phase contrast images of living cultured neurons are obtained with a transverse resolution of <2 μm. Our system is well suited for high-resolution live cell imaging and provides a compact, cost-effective alternative to full-sized phase-contrast microscopes.

  2. In-vivo dark-field and phase-contrast x-ray imaging.

    PubMed

    Bech, M; Tapfer, A; Velroyen, A; Yaroshenko, A; Pauwels, B; Hostens, J; Bruyndonckx, P; Sasov, A; Pfeiffer, F

    2013-11-13

    Novel radiography approaches based on the wave nature of x-rays when propagating through matter have a great potential for improved future x-ray diagnostics in the clinics. Here, we present a significant milestone in this imaging method: in-vivo multi-contrast x-ray imaging of a mouse using a compact scanner. Of particular interest is the enhanced contrast in regions related to the respiratory system, indicating a possible application in diagnosis of lung diseases (e.g. emphysema).

  3. In-vivo dark-field and phase-contrast x-ray imaging

    NASA Astrophysics Data System (ADS)

    Bech, M.; Tapfer, A.; Velroyen, A.; Yaroshenko, A.; Pauwels, B.; Hostens, J.; Bruyndonckx, P.; Sasov, A.; Pfeiffer, F.

    2013-11-01

    Novel radiography approaches based on the wave nature of x-rays when propagating through matter have a great potential for improved future x-ray diagnostics in the clinics. Here, we present a significant milestone in this imaging method: in-vivo multi-contrast x-ray imaging of a mouse using a compact scanner. Of particular interest is the enhanced contrast in regions related to the respiratory system, indicating a possible application in diagnosis of lung diseases (e.g. emphysema).

  4. Vortex Image Processing (VIP) package for high-contrast direct imaging

    NASA Astrophysics Data System (ADS)

    Gomez Gonzalez, C.; Absil, O.; Wertz, O.

    2016-05-01

    VIP is a Python instrument-agnostic toolbox featuring a flexible framework for reproducible and robust data reduction. VIP currently supports three high-contrast imaging observational techniques: angular, reference-star and multi-spectral differential imaging. The code can be downloaded from our git repository on Github: http://github.com/vortex-exoplanet/VIP

  5. Utilization of nanoparticles as X-ray contrast agents for diagnostic imaging applications.

    PubMed

    De La Vega, José Carlos; Häfeli, Urs O

    2015-01-01

    Among all the diagnostic imaging modalities, X-ray imaging techniques are the most commonly used owing to their high resolution and low cost. The improvement of these techniques relies heavily on the development of novel X-ray contrast agents, which are molecules that enhance the visibility of internal structures within the body in X-ray imaging. To date, clinically used X-ray contrast agents consist mainly of small iodinated molecules that might cause severe adverse effects (e.g. allergies, cardiovascular diseases and nephrotoxicity) in some patients owing to the large and repeated doses that are required to achieve good contrast. For this reason, there is an increasing interest in the development of alternative X-ray contrast agents utilizing elements with high atomic numbers (e.g. gold, bismuth, ytterbium and tantalum), which are well known for exhibiting high absorption of X-rays. Nanoparticles (NPs) made from these elements have been reported to have better imaging properties, longer blood circulation times and lower toxicity than conventional iodinated X-ray contrast agents. Additionally, the combination of two or more of these elements into a single carrier allows for the development of multimodal and hybrid contrast agents. Herein, the limitations of iodinated X-ray contrast agents are discussed and the parameters that influence the efficacy of X-ray contrast agents are summarized. Several examples of the design and production of both iodinated and iodine-free NP-based X-ray contrast agents are then provided, emphasizing the studies performed to evaluate their X-ray attenuation capabilities and their toxicity in vitro and in vivo.

  6. The CHARIS IFS for high contrast imaging at Subaru

    NASA Technical Reports Server (NTRS)

    Groff, Tyler D.; Kasdin, N. Jeremy; Limbach, Mary Anne; Galvin, Michael; Carr, Michael A.; Knapp, Gillian; Brandt, Timothy; Loomis, Craig; Jarosik, Norman; Mede, Kyle; McElwain, Michael William; Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Guyon, Olivier; Jovanovic, Nemanja; Takato, Naruhisa; Hayashi, Masahiko

    2015-01-01

    The Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) is an integral field spectrograph (IFS) being built for the Subaru telescope. CHARIS will take spectra of brown dwarfs and hot Jovian planets in the coronagraphic image provided by the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) and AO188 adaptive optics systems. The system is designed to detect objects five orders of magnitude dimmer than their parent star down to an 80 milliarcsecond inner working angle. For characterization, CHARIS has a high-resolution prism providing an average spectral resolution of R82, R69, and R82 in J, H, and K bands respectively. The so-called discovery mode uses a second low-resolution prism with an average spectral resolution of R19 spanning 1.15-2.37 microns (J+H+K bands). This is unique compared to other high contrast IFS designs. It augments low inner working angle performance by reducing the separation at which we can rely on spectral differential imaging. The principal challenge for a high-contrast IFS is quasi-static speckles, which cause undue levels of spectral crosstalk. CHARIS has addressed this through several key design aspects that should constrain crosstalk between adjacent spectral features to be below 1%. Sitting on the Nasmyth platform, the alignment between the lenslet array, prism, and detector will be highly stable, key for the performance of the data pipeline. Nearly every component has arrived and the project is entering its final build phase. Here we review the science case, the resulting design, status of final construction, and lessons learned that are directly applicable to future exoplanet instruments.

  7. Refraction-contrast tomosynthesis imaging using dark-field imaging optics

    NASA Astrophysics Data System (ADS)

    Sunaguchi, Naoki; Yuasa, Tetsuya; Huo, Qingkai; Ichihara, Shu; Ando, Masami

    2011-09-01

    A soft tissue tomosynthesis imaging system using Laue-case analyzer for dark-field imaging (DFI) optics is described. Two images from which refraction component is deduced are obtained in a single exposure of DFI, while two exposures are required in diffraction enhanced imaging (DEI). The measurement time and radiation dose are thus reduced to half those from DEI. Additionally, the proposed reconstruction algorithm, using only one tenth the number of projections required in computed tomography (CT) imaging, produced images in no way inferior to refraction-contrast CT images. We ex vivo imaged an excised human lung tissue using the system constructed at the KEK vertical wiggler beamline PF-BL14C to demonstrate the proposed imaging protocol efficacy.

  8. Fourier domain image fusion for differential X-ray phase-contrast breast imaging.

    PubMed

    Coello, Eduardo; Sperl, Jonathan I; Bequé, Dirk; Benz, Tobias; Scherer, Kai; Herzen, Julia; Sztrókay-Gaul, Anikó; Hellerhoff, Karin; Pfeiffer, Franz; Cozzini, Cristina; Grandl, Susanne

    2017-04-01

    X-Ray Phase-Contrast (XPC) imaging is a novel technology with a great potential for applications in clinical practice, with breast imaging being of special interest. This work introduces an intuitive methodology to combine and visualize relevant diagnostic features, present in the X-ray attenuation, phase shift and scattering information retrieved in XPC imaging, using a Fourier domain fusion algorithm. The method allows to present complementary information from the three acquired signals in one single image, minimizing the noise component and maintaining visual similarity to a conventional X-ray image, but with noticeable enhancement in diagnostic features, details and resolution. Radiologists experienced in mammography applied the image fusion method to XPC measurements of mastectomy samples and evaluated the feature content of each input and the fused image. This assessment validated that the combination of all the relevant diagnostic features, contained in the XPC images, was present in the fused image as well.

  9. A Computer-Aided Diagnosis System for Dynamic Contrast-Enhanced MR Images Based on Level Set Segmentation and ReliefF Feature Selection

    PubMed Central

    Zhu, Dongmei; Li, Li

    2015-01-01

    This study established a fully automated computer-aided diagnosis (CAD) system for the classification of malignant and benign masses via breast magnetic resonance imaging (BMRI). A breast segmentation method consisting of a preprocessing step to identify the air-breast interfacing boundary and curve fitting for chest wall line (CWL) segmentation was included in the proposed CAD system. The Chan-Vese (CV) model level set (LS) segmentation method was adopted to segment breast mass and demonstrated sufficiently good segmentation performance. The support vector machine (SVM) classifier with ReliefF feature selection was used to merge the extracted morphological and texture features into a classification score. The accuracy, sensitivity, and specificity measurements for the leave-half-case-out resampling method were 92.3%, 98.2%, and 76.2%, respectively. For the leave-one-case-out resampling method, the measurements were 90.0%, 98.7%, and 73.8%, respectively. PMID:25628755

  10. CT Image Contrast of High-Z Elements: Phantom Imaging Studies and Clinical Implications

    PubMed Central

    Colborn, Robert E.; Edic, Peter M.; Lambert, Jack W.; Torres, Andrew S.; Bonitatibus, Peter J.; Yeh, Benjamin M.

    2016-01-01

    Purpose To quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions. Materials and Methods Equal mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution. The solutions were imaged within a modified 32-cm CT dose index phantom at 80, 100, 120, and 140 kVp at CT. To simulate larger body sizes, 0.2-, 0.5-, and 1.0-mm-thick copper filters were applied. CT image contrast was measured and corrected for measured concentrations and presence of chlorine in some compounds. Results Each element tested provided higher image contrast than iodine at some tube potential levels. Over the range of tube potentials that are clinically practical for average-sized and larger adults—that is, 100 kVp and higher—barium, gadolinium, ytterbium, and tantalum provided consistently increased image contrast compared with iodine, respectively demonstrating 39%, 56%, 34%, and 24% increases at 100 kVp; 39%, 66%, 53%, and 46% increases at 120 kVp; and 40%, 72%, 65%, and 60% increases at 140 kVp, with no added x-ray filter. Conclusion The consistently high image contrast produced with 100–140 kVp by tantalum compared with bismuth and iodine at equal mass concentration suggests that tantalum could potentially be favorable for use as a clinical CT contrast agent. © RSNA, 2015 Online supplemental material is available for this article. PMID:26356064

  11. Second harmonic inversion for ultrasound contrast harmonic imaging.

    PubMed

    Pasovic, Mirza; Danilouchkine, Mike; Faez, Telli; van Neer, Paul L M J; Cachard, Christian; van der Steen, Antonius F W; Basset, Olivier; de Jong, Nico

    2011-06-07

    Ultrasound contrast agents (UCAs) are small micro-bubbles that behave nonlinearly when exposed to an ultrasound wave. This nonlinear behavior can be observed through the generated higher harmonics in a back-scattered echo. In past years several techniques have been proposed to detect or image harmonics produced by UCAs. In these proposed works, the harmonics generated in the medium during the propagation of the ultrasound wave played an important role, since these harmonics compete with the harmonics generated by the micro-bubbles. We present a method for the reduction of the second harmonic generated during nonlinear-propagation-dubbed second harmonic inversion (SHI). A general expression for the suppression signals is also derived. The SHI technique uses two pulses, p' and p″, of the same frequency f(0) and the same amplitude P(0) to cancel out the second harmonic generated by nonlinearities of the medium. Simulations show that the second harmonic is reduced by 40 dB on a large axial range. Experimental SHI B-mode images, from a tissue-mimicking phantom and UCAs, show an improvement in the agent-to-tissue ratio (ATR) of 20 dB compared to standard second harmonic imaging and 13 dB of improvement in harmonic power Doppler.

  12. Magnetic nanobeads as potential contrast agents for magnetic resonance imaging.

    PubMed

    Pablico-Lansigan, Michele H; Hickling, William J; Japp, Emily A; Rodriguez, Olga C; Ghosh, Anup; Albanese, Chris; Nishida, Maki; Van Keuren, Edward; Fricke, Stanley; Dollahon, Norman; Stoll, Sarah L

    2013-10-22

    Metal-oxo clusters have been used as building blocks to form hybrid nanomaterials and evaluated as potential MRI contrast agents. We have synthesized a biocompatible copolymer based on a water stable, nontoxic, mixed-metal-oxo cluster, Mn8Fe4O12(L)16(H2O)4, where L is acetate or vinyl benzoic acid, and styrene. The cluster alone was screened by NMR for relaxivity and was found to be a promising T2 contrast agent, with r1 = 2.3 mM(-1) s(-1) and r2 = 29.5 mM(-1) s(-1). Initial cell studies on two human prostate cancer cell lines, DU-145 and LNCap, reveal that the cluster has low cytotoxicity and may be potentially used in vivo. The metal-oxo cluster Mn8Fe4(VBA)16 (VBA = vinyl benzoic acid) can be copolymerized with styrene under miniemulsion conditions. Miniemulsion allows for the formation of nanometer-sized paramagnetic beads (~80 nm diameter), which were also evaluated as a contrast agent for MRI. These highly monodispersed, hybrid nanoparticles have enhanced properties, with the option for surface functionalization, making them a promising tool for biomedicine. Interestingly, both relaxivity measurements and MRI studies show that embedding the Mn8Fe4 core within a polymer matrix decreases r2 effects with little effect on r1, resulting in a positive T1 contrast enhancement.

  13. Moxifloxacin: Clinically compatible contrast agent for multiphoton imaging

    NASA Astrophysics Data System (ADS)

    Wang, Taejun; Jang, Won Hyuk; Lee, Seunghun; Yoon, Calvin J.; Lee, Jun Ho; Kim, Bumju; Hwang, Sekyu; Hong, Chun-Pyo; Yoon, Yeoreum; Lee, Gilgu; Le, Viet-Hoan; Bok, Seoyeon; Ahn, G.-One; Lee, Jaewook; Gho, Yong Song; Chung, Euiheon; Kim, Sungjee; Jang, Myoung Ho; Myung, Seung-Jae; Kim, Myoung Joon; So, Peter T. C.; Kim, Ki Hean

    2016-06-01

    Multiphoton microscopy (MPM) is a nonlinear fluorescence microscopic technique widely used for cellular imaging of thick tissues and live animals in biological studies. However, MPM application to human tissues is limited by weak endogenous fluorescence in tissue and cytotoxicity of exogenous probes. Herein, we describe the applications of moxifloxacin, an FDA-approved antibiotic, as a cell-labeling agent for MPM. Moxifloxacin has bright intrinsic multiphoton fluorescence, good tissue penetration and high intracellular concentration. MPM with moxifloxacin was demonstrated in various cell lines, and animal tissues of cornea, skin, small intestine and bladder. Clinical application is promising since imaging based on moxifloxacin labeling could be 10 times faster than imaging based on endogenous fluorescence.

  14. Moxifloxacin: Clinically compatible contrast agent for multiphoton imaging

    PubMed Central

    Wang, Taejun; Jang, Won Hyuk; Lee, Seunghun; Yoon, Calvin J.; Lee, Jun Ho; Kim, Bumju; Hwang, Sekyu; Hong, Chun-Pyo; Yoon, Yeoreum; Lee, Gilgu; Le, Viet-Hoan; Bok, Seoyeon; Ahn, G-One; Lee, Jaewook; Gho, Yong Song; Chung, Euiheon; Kim, Sungjee; Jang, Myoung Ho; Myung, Seung-Jae; Kim, Myoung Joon; So, Peter T. C.; Kim, Ki Hean

    2016-01-01

    Multiphoton microscopy (MPM) is a nonlinear fluorescence microscopic technique widely used for cellular imaging of thick tissues and live animals in biological studies. However, MPM application to human tissues is limited by weak endogenous fluorescence in tissue and cytotoxicity of exogenous probes. Herein, we describe the applications of moxifloxacin, an FDA-approved antibiotic, as a cell-labeling agent for MPM. Moxifloxacin has bright intrinsic multiphoton fluorescence, good tissue penetration and high intracellular concentration. MPM with moxifloxacin was demonstrated in various cell lines, and animal tissues of cornea, skin, small intestine and bladder. Clinical application is promising since imaging based on moxifloxacin labeling could be 10 times faster than imaging based on endogenous fluorescence. PMID:27283889

  15. High contrast imaging through adaptive transmittance control in the focal plane

    NASA Astrophysics Data System (ADS)

    Dhadwal, Harbans S.; Rastegar, Jahangir; Feng, Dake

    2016-05-01

    High contrast imaging, in the presence of a bright background, is a challenging problem encountered in diverse applications ranging from the daily chore of driving into a sun-drenched scene to in vivo use of biomedical imaging in various types of keyhole surgeries. Imaging in the presence of bright sources saturates the vision system, resulting in loss of scene fidelity, corresponding to low image contrast and reduced resolution. The problem is exacerbated in retro-reflective imaging systems where the light sources illuminating the object are unavoidably strong, typically masking the object features. This manuscript presents a novel theoretical framework, based on nonlinear analysis and adaptive focal plane transmittance, to selectively remove object domain sources of background light from the image plane, resulting in local and global increases in image contrast. The background signal can either be of a global specular nature, giving rise to parallel illumination from the entire object surface or can be represented by a mosaic of randomly orientated, small specular surfaces. The latter is more representative of real world practical imaging systems. Thus, the background signal comprises of groups of oblique rays corresponding to distributions of the mosaic surfaces. Through the imaging system, light from group of like surfaces, converges to a localized spot in the focal plane of the lens and then diverges to cast a localized bright spot in the image plane. Thus, transmittance of a spatial light modulator, positioned in the focal plane, can be adaptively controlled to block a particular source of background light. Consequently, the image plane intensity is entirely due to the object features. Experimental image data is presented to verify the efficacy of the methodology.

  16. Assessment of contrast enhanced respiration managed cone-beam CT for image guided radiotherapy of intrahepatic tumors

    SciTech Connect

    Jensen, Nikolaj K. G.; Stewart, Errol; Lock, Michael; Fisher, Barbara; Kozak, Roman; Chen, Jeff; Lee, Ting-Yim; Wong, Eugene

    2014-05-15

    Purpose: Contrast enhancement and respiration management are widely used during image acquisition for radiotherapy treatment planning of liver tumors along with respiration management at the treatment unit. However, neither respiration management nor intravenous contrast is commonly used during cone-beam CT (CBCT) image acquisition for alignment prior to radiotherapy. In this study, the authors investigate the potential gains of injecting an iodinated contrast agent in combination with respiration management during CBCT acquisition for liver tumor radiotherapy. Methods: Five rabbits with implanted liver tumors were subjected to CBCT with and without motion management and contrast injection. The acquired CBCT images were registered to the planning CT to determine alignment accuracy and dosimetric impact. The authors developed a simulation tool for simulating contrast-enhanced CBCT images from dynamic contrast enhanced CT imaging (DCE-CT) to determine optimal contrast injection protocols. The tool was validated against contrast-enhanced CBCT of the rabbit subjects and was used for five human patients diagnosed with hepatocellular carcinoma. Results: In the rabbit experiment, when neither motion management nor contrast was used, tumor centroid misalignment between planning image and CBCT was 9.2 mm. This was reduced to 2.8 mm when both techniques were employed. Tumors were not visualized in clinical CBCT images of human subjects. Simulated contrast-enhanced CBCT was found to improve tumor contrast in all subjects. Different patients were found to require different contrast injections to maximize tumor contrast. Conclusions: Based on the authors’ animal study, respiration managed contrast enhanced CBCT improves IGRT significantly. Contrast enhanced CBCT benefits from patient specific tracer kinetics determined from DCE-CT.

  17. Phase Contrast Imaging on the HL-2A Tokamak

    NASA Astrophysics Data System (ADS)

    Yu, Yi; Gong, Shaobo; Xu, Min; Jiang, Wei; Zhong, Wulv; Shi, Zhongbin; Wang, Huajie; Wu, Yifan; Yuan, Boda; Lan, Tao; Ye, Minyou; Duan, Xuru; HL-2A Team

    2016-10-01

    In this article we present the design of a phase contrast imaging (PCI) system on the HL-2A tokamak. This diagnostic is developed to infer line integrated plasma density fluctuations by measuring the phase shift of an expanded CO2 laser beam passing through magnetically confined high temperature plasmas. This system is designed to diagnose plasma density fluctuations with the maximum wavenumber of 66 cm-1. The designed wavenumber resolution is 2.09cm-1, and the time resolution is higher than 0.2 μs. The broad kρs ranging from 0.34 to 13.37 makes it suitable for turbulence measurement. An upgraded PCI system is also discussed, which is designed for the HL-2M tokamak. Supported by the National Magnetic Confinement Fusion Energy Research Project (Grant No. 2015GB120002), the National Natural Science Foundation of China (Grant No. 11375053, 11105144, 10905057, 11535013).

  18. Phase-Change Contrast Agents for Imaging and Therapy

    PubMed Central

    Sheeran, Paul S.; Dayton, Paul A.

    2016-01-01

    Phase-change contrast agents (PCCAs) for ultrasound-based applications have resulted in novel ways of approaching diagnostic and therapeutic techniques beyond what is possible with microbubble contrast agents and liquid emulsions. When subjected to sufficient pressures delivered by an ultrasound transducer, stabilized droplets undergo a phase-transition to the gaseous state and a volumetric expansion occurs. This phenomenon, termed acoustic droplet vaporization, has been proposed as a means to address a number of in vivo applications at the microscale and nanoscale. In this review, the history of PCCAs, physical mechanisms involved, and proposed applications are discussed with a summary of studies demonstrated in vivo. Factors that influence the design of PCCAs are discussed, as well as the need for future studies to characterize potential bioeffects for administration in humans and optimization of ultrasound parameters. PMID:22352770

  19. Improving scale invariant feature transform with local color contrastive descriptor for image classification

    NASA Astrophysics Data System (ADS)

    Guo, Sheng; Huang, Weilin; Qiao, Yu

    2017-01-01

    Image representation and classification are two fundamental tasks toward version understanding. Shape and texture provide two key features for visual representation and have been widely exploited in a number of successful local descriptors, e.g., scale invariant feature transform (SIFT), local binary pattern descriptor, and histogram of oriented gradient. Unlike these gradient-based descriptors, this paper presents a simple yet efficient local descriptor, named local color contrastive descriptor (LCCD), which captures the contrastive aspects among local regions or color channels for image representation. LCCD is partly inspired by the neural science facts that color contrast plays important roles in visual perception and there exist strong linkages between color and shape. We leverage f-divergence as a robust measure to estimate the contrastive features between different spatial locations and multiple channels. Our descriptor enriches local image representation with both color and contrast information. Due to that LCCD does not explore any gradient information, individual LCCD does not yield strong performance. But we verified experimentally that LCCD can compensate strongly SIFT. Extensive experimental results on image classification show that our descriptor improves the performance of SIFT substantially by combination on three challenging benchmarks, including MIT Indoor-67 database, SUN397, and PASCAL VOC 2007.

  20. High-Resolution Phase-Contrast Imaging of Submicron Particles in Unstained Lung Tissue

    SciTech Connect

    Schittny, J. C.; Barre, S. F.; Haberthuer, D.; Mokso, R.; Tsuda, A.; Stampanoni, M.

    2011-09-09

    To access the risks and chances of deposition of submicron particles in the gas-exchange area of the lung, a precise three-dimensional (3D)-localization of the sites of deposition is essential--especially because local peaks of deposition are expected in the acinar tree and in individual alveoli. In this study we developed the workflow for such an investigation. We administered 200-nm gold particles to young adult rats by intratracheal instillation. After fixation and paraffin embedding, their lungs were imaged unstained using synchrotron radiation x-ray tomographic microscopy (SRXTM) at the beamline TOMCAT (Swiss Light Source, Villigen, Switzerland) at sample detector distances of 2.5 mm (absorption contrast) and of 52.5 mm (phase contrast). A segmentation based on a global threshold of grey levels was successfully done on absorption-contrast images for the gold and on the phase-contrast images for the tissue. The smallest spots containing gold possessed a size of 1-2 voxels of 370-nm side length. We conclude that a combination of phase and absorption contrast SRXTM imaging is necessary to obtain the correct segmentation of both tissue and gold particles. This method will be used for the 3D localization of deposited particles in the gas-exchange area of the lung.

  1. A novel color image compression algorithm using the human visual contrast sensitivity characteristics

    NASA Astrophysics Data System (ADS)

    Yao, Juncai; Liu, Guizhong

    2017-03-01

    In order to achieve higher image compression ratio and improve visual perception of the decompressed image, a novel color image compression scheme based on the contrast sensitivity characteristics of the human visual system (HVS) is proposed. In the proposed scheme, firstly the image is converted into the YCrCb color space and divided into sub-blocks. Afterwards, the discrete cosine transform is carried out for each sub-block, and three quantization matrices are built to quantize the frequency spectrum coefficients of the images by combining the contrast sensitivity characteristics of HVS. The Huffman algorithm is used to encode the quantized data. The inverse process involves decompression and matching to reconstruct the decompressed color image. And simulations are carried out for two color images. The results show that the average structural similarity index measurement (SSIM) and peak signal to noise ratio (PSNR) under the approximate compression ratio could be increased by 2.78% and 5.48%, respectively, compared with the joint photographic experts group (JPEG) compression. The results indicate that the proposed compression algorithm in the text is feasible and effective to achieve higher compression ratio under ensuring the encoding and image quality, which can fully meet the needs of storage and transmission of color images in daily life.

  2. Phase-contrast imaging in aberration-corrected scanning transmission electron microscopy.

    PubMed

    Krumeich, F; Müller, E; Wepf, R A

    2013-06-01

    Although the presence of phase-contrast information in bright field images recorded with a scanning transmission electron microscope (STEM) has been known for a long time, its systematic exploitation for the structural characterization of materials began only with the availability of aberration-corrected microscopes that allow sufficiently large illumination angles. Today, phase-contrast STEM (PC-STEM) imaging represents an increasingly important alternative to the well-established HRTEM method. In both methods, the image contrast is coherently generated and thus depends not only on illumination and collection angles but on defocus and specimen thickness as well. By PC-STEM, a projection of the crystal potential is obtained in thin areas, with the scattering sites being represented either with dark or bright contrast at two different defocus values which are both close to Gaussian defocus. This imaging behavior can be further investigated by image simulations performed with standard HRTEM simulation software based on the principle of reciprocity. As examples for the application of this method, PC-STEM results obtained on metal nanoparticles and dodecagonal quasicrystals dd-(Ta,V)₁.₆Te are discussed.

  3. Exploring silver as a contrast agent for contrast-enhanced dual-energy X-ray breast imaging

    PubMed Central

    Tsourkas, A; Maidment, A D A

    2014-01-01

    Objective: Through prior monoenergetic modelling, we have identified silver as a potential alternative to iodine in dual-energy (DE) X-ray breast imaging. The purpose of this study was to compare the performance of silver and iodine contrast agents in a commercially available DE imaging system through a quantitative analysis of signal difference-to-noise ratio (SDNR). Methods: A polyenergetic simulation algorithm was developed to model the signal intensity and noise. The model identified the influence of various technique parameters on SDNR. The model was also used to identify the optimal imaging techniques for silver and iodine, so that the two contrast materials could be objectively compared. Results: The major influences on the SDNR were the low-energy dose fraction and breast thickness. An increase in the value of either of these parameters resulted in a decrease in SDNR. The SDNR for silver was on average 43% higher than that for iodine when imaged at their respective optimal conditions, and 40% higher when both were imaged at the optimal conditions for iodine. Conclusion: A silver contrast agent should provide benefit over iodine, even when translated to the clinic without modification of imaging system or protocol. If the system were slightly modified to reflect the lower k-edge of silver, the difference in SDNR between the two materials would be increased. Advances in knowledge: These data are the first to demonstrate the suitability of silver as a contrast material in a clinical contrast-enhanced DE image acquisition system. PMID:24998157

  4. Character segmentation and thresholding in low-contrast scene images

    NASA Astrophysics Data System (ADS)

    Winger, Lowell L.; Jernigan, M. Ed; Robinson, John A.

    1996-03-01

    We are developing a portable text-to-speech system for the vision impaired. The input image is acquired with a lightweight CCD camera that may be poorly focused and aimed, and perhaps taken under inadequate and uneven illumination. We therefore require efficient and effective thresholding and segmentation methods which are robust with respect to character contrast, font, size, and format. In this paper, we present a fast thresholding scheme which combines a local variance measure with a logical stroke-width method. An efficient post- thresholding segmentation scheme utilizing Fisher's linear discriminant to distinguish noise and character components functions as an effective pre-processing step for the application of commercial segmentation and character recognition methods. The performance of this fast new method compared favorably with other methods for the extraction of characters from uncontrolled illumination, omnifont scene images. We demonstrate the suitability of this method for use in an automated portable reader through a software implementation running on a laptop 486 computer in our prototype device.

  5. Optical Fourier techniques for medical image processing and phase contrast imaging

    PubMed Central

    Yelleswarapu, Chandra S.; Kothapalli, Sri-Rajasekhar; Rao, D.V.G.L.N.

    2008-01-01

    This paper briefly reviews the basics of optical Fourier techniques (OFT) and applications for medical image processing as well as phase contrast imaging of live biological specimens. Enhancement of microcalcifications in a mammogram for early diagnosis of breast cancer is the main focus. Various spatial filtering techniques such as conventional 4f filtering using a spatial mask, photoinduced polarization rotation in photosensitive materials, Fourier holography, and nonlinear transmission characteristics of optical materials are discussed for processing mammograms. We also reviewed how the intensity dependent refractive index can be exploited as a phase filter for phase contrast imaging with a coherent source. This novel approach represents a significant advance in phase contrast microscopy. PMID:18458764

  6. Effect of region of interest (ROI) filters on image contrast and relative detected signal

    NASA Astrophysics Data System (ADS)

    Massoumzadeh, Parinaz

    Region of interest (ROI) fluoroscopic techniques have the potential for improving image quality and greatly reducing radiation dose. The broad goal of this study is to determine the optimal filter material to be used for ROI fluoroscopic procedures using both conventional phosphor screen base and nontraditional semiconductor- based image receptors. The effects of rare earth materials (Sm, Gd, and Dy), conventional filters (Cu, Sn, and Pb), and a low-Z material (Lucite) as x-ray beam shaping ROI filters were evaluated using a computer simulation to determine their transmission and effect on radiographic image quality for a broad range of thicknesses of contrast media (iodine, barium, calcium, and fat) embedded in Lucite or muscle phantom for both conventional (CsI) and nontraditional (a-Se) image receptors as a function of kVp (40-100 kVp). Selected measurements were also performed to verify the results of the simulation. The preferred filter material should have least variation of transmission with change in kVp, and in combination with a suitable image receptor, it should have no loss (or even increase) in radiographic contrast, contrast-to-noise-ratio (CNR), and figure-of-merit (FOM) in the periphery. The results indicate that in general the rare earth filters compared to conventional filters have much less variation in transmission, much higher image contrast, higher CNR at all kVp's, and slightly better FOM at high kVp's. Low-Z material requires too thick of a filter for practical purposes. Moreover, all filter materials improve patient entrance skin exposure compared with no filter, however, conventional filters give less entrance exposure than rare earth materials for the same detected signal for all kVp's. Furthermore, a-Se image receptor provides substantially better performance compared to CsI image receptor for barium and iodinated contrast media, especially when the combination of rare earth filter and a-Se image receptor is used. Analytical results of

  7. Biocompatible polypyrrole nanoparticles as a novel organic photoacoustic contrast agent for deep tissue imaging

    NASA Astrophysics Data System (ADS)

    Zha, Zhengbao; Deng, Zijian; Li, Yanyan; Li, Changhui; Wang, Jinrui; Wang, Shumin; Qu, Enze; Dai, Zhifei

    2013-05-01

    Photoacoustic tomography (PAT) has emerged as a hybrid, nonionizing imaging modality because of its satisfactory spatial resolution and high soft tissue contrast. Here, we demonstrate the application of a novel organic PAT contrast agent based on polypyrrole nanoparticles (PPy NPs). Monodisperse PPy NPs are ~46 nm in diameter with strong absorption in the near-infrared (NIR) range, which allowed visualization of PPy NP-containing agar gel embedded in chicken breast muscle at a depth of ~4.3 cm. Compared with PAT images based on the intrinsic optical contrast in mice, the PAT images acquired within 1 h after intravenous administration of PPy NPs showed the brain vasculature with greater clarity than hemoglobin in blood. Preliminary results showed no acute toxicity to the vital organs (heart, liver, spleen, lungs and kidneys) in mice following a single imaging dose of PPy NPs. Our results indicate that PPy NPs are promising contrast agents for PAT with good biocompatibility, high spatial resolution and enhanced sensitivity.

  8. Advanced contrast nanoagents for photoacoustic molecular imaging, cytometry, blood test and photothermal theranostics†

    PubMed Central

    de la Zerda, Adam; Kim, Jin-Woo; Galanzha, Ekaterina I.; Gambhir, Sanjiv S.; Zharov, Vladimir P.

    2013-01-01

    Various nanoparticles have raised significant interest over the past decades for their unique physical and optical properties and biological utilities. Here we summarize the vast applications of advanced nanoparticles with a focus on carbon nanotube (CNT)-based or CNT-catalyzed contrast agents for photoacoustic (PA) imaging, cytometry and theranostics applications based on the photothermal (PT) effect. We briefly review the safety and potential toxicity of the PA/PT contrast nanoagents, while showing how the physical properties as well as multiple biological coatings change their toxicity profiles and contrasts. We provide general guidelines needed for the validation of a new molecular imaging agent in living subjects, and exemplify these guidelines with single-walled CNTs targeted to αvβ3, an integrin associated with tumor angiogenesis, and golden carbon nanotubes targeted to LYVE-1, endothelial lymphatic receptors. An extensive review of the potential applications of advanced contrast agents is provided, including imaging of static targets such as tumor angiogenesis receptors, in vivo cytometry of dynamic targets such as circulating tumor cells and nanoparticles in blood, lymph, bones and plants, methods to enhance the PA and PT effects with transient and stationary bubble conjugates, PT/PA Raman imaging and multispectral histology. Finally, theranostic applications are reviewed, including the nanophotothermolysis of individual tumor cells and bacteria with clustered nanoparticles, nanothrombolysis of blood clots, detection and purging metastasis in sentinel lymph nodes, spectral hole burning and multiplex therapy with ultrasharp rainbow nanoparticles. PMID:22025336

  9. Research into europium complexes as magnetic resonance imaging contrast agents (Review)

    PubMed Central

    HAN, GUOCAN; DENG, YANGWEI; SUN, JIHONG; LING, JUN; SHEN, ZHIQUAN

    2015-01-01

    Europium (Eu) is a paramagnetic lanthanide element that possesses an outstanding luminescent property. Eu complexes are ideal fluorescence imaging (FI) agents. Eu2+ has satisfactory relaxivity and optical properties, and can realize magnetic resonance (MRI)-FI dual imaging applications when used with appropriate cryptands that render it oxidatively stable. By contrast, based on the chemical exchange saturation transfer (CEST) mechanism, Eu3+ complexes can provide enhanced MRI sensitivity when used with optimal cryptands, incorporated into polymeric CEST agents or blended with Gd3+. Eu complexes are promising in MRI-FI dual imaging applications and have a bright future. PMID:26136858

  10. Infrared moving point target detection based on spatial-temporal local contrast filter

    NASA Astrophysics Data System (ADS)

    Deng, Lizhen; Zhu, Hu; Tao, Chao; Wei, Yantao

    2016-05-01

    Infrared moving point target detection is a challenging task. In this paper, we define a novel spatial local contrast (SLC) and a novel temporal local contrast (TLC) to enhance the target's contrast. Based on the defined spatial local contrast and temporal local contrast, we propose a simple but powerful spatial-temporal local contrast filter (STLCF) to detect moving point target from infrared image sequences. In order to verify the performance of spatial-temporal local contrast filter on detecting moving point target, different detection methods are used to detect the target from several infrared image sequences for comparison. The experimental results show that the proposed spatial-temporal local contrast filter has great superiority in moving point target detection.

  11. New Colors for Histology: Optimized Bivariate Color Maps Increase Perceptual Contrast in Histological Images

    PubMed Central

    Kather, Jakob Nikolas; Weis, Cleo-Aron; Marx, Alexander; Schuster, Alexander K.; Schad, Lothar R.; Zöllner, Frank Gerrit

    2015-01-01

    Background Accurate evaluation of immunostained histological images is required for reproducible research in many different areas and forms the basis of many clinical decisions. The quality and efficiency of histopathological evaluation is limited by the information content of a histological image, which is primarily encoded as perceivable contrast differences between objects in the image. However, the colors of chromogen and counterstain used for histological samples are not always optimally distinguishable, even under optimal conditions. Methods and Results In this study, we present a method to extract the bivariate color map inherent in a given histological image and to retrospectively optimize this color map. We use a novel, unsupervised approach based on color deconvolution and principal component analysis to show that the commonly used blue and brown color hues in Hematoxylin—3,3’-Diaminobenzidine (DAB) images are poorly suited for human observers. We then demonstrate that it is possible to construct improved color maps according to objective criteria and that these color maps can be used to digitally re-stain histological images. Validation To validate whether this procedure improves distinguishability of objects and background in histological images, we re-stain phantom images and N = 596 large histological images of immunostained samples of human solid tumors. We show that perceptual contrast is improved by a factor of 2.56 in phantom images and up to a factor of 2.17 in sets of histological tumor images. Context Thus, we provide an objective and reliable approach to measure object distinguishability in a given histological image and to maximize visual information available to a human observer. This method could easily be incorporated in digital pathology image viewing systems to improve accuracy and efficiency in research and diagnostics. PMID:26717571

  12. Image quality, threshold contrast and mean glandular dose in CR mammography.

    PubMed

    Jakubiak, R R; Gamba, H R; Neves, E B; Peixoto, J E

    2013-09-21

    In many countries, computed radiography (CR) systems represent the majority of equipment used in digital mammography. This study presents a method for optimizing image quality and dose in CR mammography of patients with breast thicknesses between 45 and 75 mm. Initially, clinical images of 67 patients (group 1) were analyzed by three experienced radiologists, reporting about anatomical structures, noise and contrast in low and high pixel value areas, and image sharpness and contrast. Exposure parameters (kV, mAs and target/filter combination) used in the examinations of these patients were reproduced to determine the contrast-to-noise ratio (CNR) and mean glandular dose (MGD). The parameters were also used to radiograph a CDMAM (version 3.4) phantom (Artinis Medical Systems, The Netherlands) for image threshold contrast evaluation. After that, different breast thicknesses were simulated with polymethylmethacrylate layers and various sets of exposure parameters were used in order to determine optimal radiographic parameters. For each simulated breast thickness, optimal beam quality was defined as giving a target CNR to reach the threshold contrast of CDMAM images for acceptable MGD. These results were used for adjustments in the automatic exposure control (AEC) by the maintenance team. Using optimized exposure parameters, clinical images of 63 patients (group 2) were evaluated as described above. Threshold contrast, CNR and MGD for such exposure parameters were also determined. Results showed that the proposed optimization method was effective for all breast thicknesses studied in phantoms. The best result was found for breasts of 75 mm. While in group 1 there was no detection of the 0.1 mm critical diameter detail with threshold contrast below 23%, after the optimization, detection occurred in 47.6% of the images. There was also an average MGD reduction of 7.5%. The clinical image quality criteria were attended in 91.7% for all breast thicknesses evaluated in

  13. Image quality, threshold contrast and mean glandular dose in CR mammography

    NASA Astrophysics Data System (ADS)

    Jakubiak, R. R.; Gamba, H. R.; Neves, E. B.; Peixoto, J. E.

    2013-09-01

    In many countries, computed radiography (CR) systems represent the majority of equipment used in digital mammography. This study presents a method for optimizing image quality and dose in CR mammography of patients with breast thicknesses between 45 and 75 mm. Initially, clinical images of 67 patients (group 1) were analyzed by three experienced radiologists, reporting about anatomical structures, noise and contrast in low and high pixel value areas, and image sharpness and contrast. Exposure parameters (kV, mAs and target/filter combination) used in the examinations of these patients were reproduced to determine the contrast-to-noise ratio (CNR) and mean glandular dose (MGD). The parameters were also used to radiograph a CDMAM (version 3.4) phantom (Artinis Medical Systems, The Netherlands) for image threshold contrast evaluation. After that, different breast thicknesses were simulated with polymethylmethacrylate layers and various sets of exposure parameters were used in order to determine optimal radiographic parameters. For each simulated breast thickness, optimal beam quality was defined as giving a target CNR to reach the threshold contrast of CDMAM images for acceptable MGD. These results were used for adjustments in the automatic exposure control (AEC) by the maintenance team. Using optimized exposure parameters, clinical images of 63 patients (group 2) were evaluated as described above. Threshold contrast, CNR and MGD for such exposure parameters were also determined. Results showed that the proposed optimization method was effective for all breast thicknesses studied in phantoms. The best result was found for breasts of 75 mm. While in group 1 there was no detection of the 0.1 mm critical diameter detail with threshold contrast below 23%, after the optimization, detection occurred in 47.6% of the images. There was also an average MGD reduction of 7.5%. The clinical image quality criteria were attended in 91.7% for all breast thicknesses evaluated in both

  14. The evolution of gadolinium based contrast agents: from single-modality to multi-modality

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Liu, Ruiqing; Peng, Hui; Li, Penghui; Xu, Zushun; Whittaker, Andrew K.

    2016-05-01

    Gadolinium-based contrast agents are extensively used as magnetic resonance imaging (MRI) contrast agents due to their outstanding signal enhancement and ease of chemical modification. However, it is increasingly recognized that information obtained from single modal molecular imaging cannot satisfy the higher requirements on the efficiency and accuracy for clinical diagnosis and medical research, due to its limitation and default rooted in single molecular imaging technique itself. To compensate for the deficiencies of single function magnetic resonance imaging contrast agents, the combination of multi-modality imaging has turned to be the research hotpot in recent years. This review presents an overview on the recent developments of the functionalization of gadolinium-based contrast agents, and their application in biomedicine applications.

  15. Chain of evidence generation for contrast enhancement in digital image forensics

    NASA Astrophysics Data System (ADS)

    Battiato, Sebastiano; Messina, Giuseppe; Strano, Daniela

    2010-01-01

    The quality of the images obtained by digital cameras has improved a lot since digital cameras early days. Unfortunately, it is not unusual in image forensics to find wrongly exposed pictures. This is mainly due to obsolete techniques or old technologies, but also due to backlight conditions. To extrapolate some invisible details a stretching of the image contrast is obviously required. The forensics rules to produce evidences require a complete documentation of the processing steps, enabling the replication of the entire process. The automation of enhancement techniques is thus quite difficult and needs to be carefully documented. This work presents an automatic procedure to find contrast enhancement settings, allowing both image correction and automatic scripting generation. The technique is based on a preprocessing step which extracts the features of the image and selects correction parameters. The parameters are thus saved through a JavaScript code that is used in the second step of the approach to correct the image. The generated script is Adobe Photoshop compliant (which is largely used in image forensics analysis) thus permitting the replication of the enhancement steps. Experiments on a dataset of images are also reported showing the effectiveness of the proposed methodology.

  16. A review of contrast pattern based data mining

    NASA Astrophysics Data System (ADS)

    Zhu, Shiwei; Ju, Meilong; Yu, Junfeng; Cai, Binlei; Wang, Aiping

    2015-07-01

    Contrast pattern based data mining is concerned with the mining of patterns and models that contrast two or more datasets. Contrast patterns can describe similarities or differences between the datasets. They represent strong contrast knowledge and have been shown to be very successful for constructing accurate and robust clusters and classifiers. The increasing use of contrast pattern data mining has initiated a great deal of research and development attempts in the field of data mining. A comprehensive revision on the existing contrast pattern based data mining research is given in this paper. They are generally categorized into background and representation, definitions and mining algorithms, contrast pattern based classification, clustering, and other applications, the research trends in future. The primary of this paper is to server as a glossary for interested researchers to have an overall picture on the current contrast based data mining development and identify their potential research direction to future investigation.

  17. In-line phase-contrast stereoscopic X-ray imaging for radiological purposes: An initial experimental study

    NASA Astrophysics Data System (ADS)

    Siegbahn, E. A.; Coan, P.; Zhou, S.-A.; Bravin, A.; Brahme, A.

    2011-02-01

    We report results from a pilot study in which the in-line propagation-based phase-contrast imaging technique is combined with the stereoscopic method. Two phantoms were imaged at several sample-detector distances using monochromatic, 30 keV, X-rays. High contrast- and spatial-resolution phase-contrast stereoscopic pairs of X-ray images were constructed using the anaglyph approach and a vivid stereoscopic effect was demonstrated. On the other hand, images of the same phantoms obtained with a shorter sample-to-detector distance, but otherwise the same experimental conditions (i.e. the same X-ray energy and absorbed radiation dose), corresponding to the conventional attenuation-based imaging mode, hardly revealed stereoscopic effects because of the lower image contrast produced. These results have confirmed our hypothesis that stereoscopic X-ray images of samples with objects composed of low-atomic-number elements are considerably improved if phase-contrast imaging is used. It is our belief that the high-resolution phase-contrast stereoscopic method will be a valuable new medical imaging tool for radiologists and that it will be of help to enhance the diagnostic capability in the examination of patients in future clinical practice, even though further efforts will be needed to optimize the system performance.

  18. ASFNR Recommendations for Clinical Performance of MR Dynamic Susceptibility Contrast Perfusion Imaging of the Brain

    PubMed Central

    Welker, K.; Boxerman, J.; Kalnin, A.; Kaufmann, T.; Shiroishi, M.; Wintermark, M.

    2016-01-01

    SUMMARY MR perfusion imaging is becoming an increasingly common means of evaluating a variety of cerebral pathologies, including tumors and ischemia. In particular, there has been great interest in the use of MR perfusion imaging for both assessing brain tumor grade and for monitoring for tumor recurrence in previously treated patients. Of the various techniques devised for evaluating cerebral perfusion imaging, the dynamic susceptibility contrast method has been employed most widely among clinical MR imaging practitioners. However, when implementing DSC MR perfusion imaging in a contemporary radiology practice, a neuroradiologist is confronted with a large number of decisions. These include choices surrounding appropriate patient selection, scan-acquisition parameters, data-postprocessing methods, image interpretation, and reporting. Throughout the imaging literature, there is conflicting advice on these issues. In an effort to provide guidance to neuroradiologists struggling to implement DSC perfusion imaging in their MR imaging practice, the Clinical Practice Committee of the American Society of Functional Neuroradiology has provided the following recommendations. This guidance is based on review of the literature coupled with the practice experience of the authors. While the ASFNR acknowledges that alternate means of carrying out DSC perfusion imaging may yield clinically acceptable results, the following recommendations should provide a framework for achieving routine success in this complicated-but-rewarding aspect of neuroradiology MR imaging practice. PMID:25907520

  19. Second order x-ray in-line phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Cong, Wenxiang; Wang, Ge

    2014-09-01

    X-ray phase imaging is sensitive to structural variation of soft tissue, and offers excellent contrast resolution for characterization of cancerous tissues. Also, the cross-section of x-ray phase shift is a thousand times greater than that of x-ray attenuation in soft tissue over the diagnostic energy range, allowing a much higher signal-to-noise ratio at a substantially lower radiation dose than attenuation-based x-ray imaging. In this paper, we present a second order approximation model with respect to phase shift based on the paraxial Fresnel-Kirchhoff diffraction theory, and also discuss in-line dark-field imaging based on the second order model. This proposed model accurately establishes a quantitative correspondence between phases and recorded intensity images, outperforming the linear phase approximation model widely used in the conventional methods of x-ray in-line phase-contrast imaging. This new model can be iteratively solved using the algebraic reconstruction technique (ART). The state of the art compressive sensing ingredients can be incorporated to achieve high quality image reconstruction. Our numerical simulation studies demonstrate the feasibility of the proposed approach that is more accurate and stable, and more robust against noise than the conventional approach.

  20. Quantitative evaluation of mucosal vascular contrast in narrow band imaging using Monte Carlo modeling

    NASA Astrophysics Data System (ADS)

    Le, Du; Wang, Quanzeng; Ramella-Roman, Jessica; Pfefer, Joshua

    2012-06-01

    Narrow-band imaging (NBI) is a spectrally-selective reflectance imaging technique for enhanced visualization of superficial vasculature. Prior clinical studies have indicated NBI's potential for detection of vasculature abnormalities associated with gastrointestinal mucosal neoplasia. While the basic mechanisms behind the increased vessel contrast - hemoglobin absorption and tissue scattering - are known, a quantitative understanding of the effect of tissue and device parameters has not been achieved. In this investigation, we developed and implemented a numerical model of light propagation that simulates NBI reflectance distributions. This was accomplished by incorporating mucosal tissue layers and vessel-like structures in a voxel-based Monte Carlo algorithm. Epithelial and mucosal layers as well as blood vessels were defined using wavelength-specific optical properties. The model was implemented to calculate reflectance distributions and vessel contrast values as a function of vessel depth (0.05 to 0.50 mm) and diameter (0.01 to 0.10 mm). These relationships were determined for NBI wavelengths of 410 nm and 540 nm, as well as broadband illumination common to standard endoscopic imaging. The effects of illumination bandwidth on vessel contrast were also simulated. Our results provide a quantitative analysis of the effect of absorption and scattering on vessel contrast. Additional insights and potential approaches for improving NBI system contrast are discussed.

  1. X-ray phase contrast imaging at MAMI

    NASA Astrophysics Data System (ADS)

    El-Ghazaly, M.; Backe, H.; Lauth, W.; Kube, G.; Kunz, P.; Sharafutdinov, A.; Weber, T.

    2006-05-01

    Experiments have been performed to explore the potential of the low emittance 855MeV electron beam of the Mainz Microtron MAMI for imaging with coherent X-rays. Transition radiation from a micro-focused electron beam traversing a foil stack served as X-ray source with good transverse coherence. Refraction contrast radiographs of low absorbing materials, in particular polymer strings with diameters between 30 and 450μm, were taken with a polychromatic transition radiation X-ray source with a spectral distribution in the energy range between 8 and about 40keV. The electron beam spot size had standard deviation σh = (8.6±0.1)μm in the horizontal and σv = (7.5±0.1)μm in the vertical direction. X-ray films were used as detectors. The source-to-detector distance amounted to 11.4m. The objects were placed in a distance of up to 6m from the X-ray film. Holograms of strings were taken with a beam spot size σv = (0.50±0.05)μm in vertical direction, and a monochromatic X-ray beam of 6keV energy. A good longitudinal coherence has been obtained by the (111) reflection of a flat silicon single crystal in Bragg geometry. It has been demonstrated that a direct exposure CCD chip with a pixel size of 13×13μm^2 provides a highly efficient on-line detector. Contrast images can easily be generated with a complete elimination of all parasitic background. The on-line capability allows a minimization of the beam spot size by observing the smallest visible interference fringe spacings or the number of visible fringes. It has been demonstrated that X-ray films are also very useful detectors. The main advantage in comparison with the direct exposure CCD chip is the resolution. For the Structurix D3 (Agfa) X-ray film the standard deviation of the resolution was measured to be σf = (1.2±0.4)μm, which is about a factor of 6 better than for the direct exposure CCD chip. With the small effective X-ray spot size in vertical direction of σv = (1.2±0.3)μm and a geometrical

  2. Hue-preserving local contrast enhancement and illumination compensation for outdoor color images

    NASA Astrophysics Data System (ADS)

    Tektonidis, Marco; Monnin, David; Christnacher, Frank

    2015-10-01

    Real-time applications in the field of security and defense use dynamic color camera systems to gain a better understanding of outdoor scenes. To enhance details and improve the visibility in images it is required to per- form local image processing, and to reduce lightness and color inconsistencies between images acquired under different illumination conditions it is required to compensate illumination effects. We introduce an automatic hue-preserving local contrast enhancement and illumination compensation approach for outdoor color images. Our approach is based on a shadow-weighted intensity-based Retinex model which enhances details and compensates the illumination effect on the lightness of an image. The Retinex model exploits information from a shadow detection approach to reduce lightness halo artifacts on shadow boundaries. We employ a hue-preserving color transformation to obtain a color image based on the original color information. To reduce color inconsistencies between images acquired under different illumination conditions we process the saturation using a scaling function. The approach has been successfully applied to static and dynamic color image sequences of outdoor scenes and an experimental comparison with previous Retinex-based approaches has been carried out.

  3. A naturally occurring contrast agent for OCT imaging of smokers' lung

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Bagnaninchi, Pierre O.; Whiteman, Suzanne C.; Gey van Pittius, Daniel; El Haj, Alicia J.; Spiteri, Monica A.; Wang, Ruikang K.

    2005-08-01

    Optical coherence tomography (OCT) offers great potential for clinical applications in terms of its cost, safety and real-time imaging capability. Improvement of its resolution for revealing sub-layers or sub-cellular components within a tissue will further widen its application. In this study we report that carbon pigment, which is frequently present in the lungs of smokers, could be used as a contrast agent to improve the OCT imaging of lung tissue. Carbon produced an intense bright OCT image at a relatively deep location. The parallel histopathological section analysis confirmed the presence of carbon pigment in such tissues. The underlying mechanism of the OCT image formation has been discussed based on a model system in which carbon particles were dispersed in agar gel. Calculations and in-depth intensity profiles of OCT revealed that higher refractive index particles with a size close to or smaller than the wavelength would greatly increase backscattering and generate a sharp contrast, while a particle size several times larger than the wavelength would absorb or obstruct the light path. The naturally occurring contrast agent could provide a diagnostic biomarker of lung tissue in smokers. Furthermore, carbon under such circumstances, can be used as an effective exogenous contrast agent, with which specific components or tissues exhibiting early tumour formation can be optically labelled to delineate the location and boundary, providing potential for early cancer detection and its treatment.

  4. Table-top phase-contrast imaging employing photon-counting detectors towards mammographic applications

    NASA Astrophysics Data System (ADS)

    Palma, K. D.; Pichotka, M.; Hasn, S.; Granja, C.

    2017-02-01

    In mammography the difficult task to detect microcalcifications (≈ 100 μm) and low contrast structures in the breast has been a topic of interest from its beginnings. The possibility to improve the image quality requires the effort to employ novel X-ray imaging techniques, such as phase-contrast, and high resolution detectors. Phase-contrast techniques are promising tools for medical diagnosis because they provide additional and complementary information to traditional absorption-based X-ray imaging methods. In this work a Hamamatsu microfocus X-ray source with tungsten anode and a photon counting detector (Timepix operated in Medipix mode) was used. A significant improvement in the detection of phase-effects using Medipix detector was observed in comparison to an standard flat-panel detector. An optimization of geometrical parameters reveals the dependency on the X-ray propagation path and the small angle deviation. The quantification of these effects was achieved taking into account the image noise, contrast, spatial resolution of the phase-enhancement, absorbed dose, and energy dependence.

  5. High-Contrast NIR Polarization Imaging of MWC480

    NASA Technical Reports Server (NTRS)

    McElwain, M. W.; Kusakabe, N.; Hashimoto, J.; Kudo, T.; Kandori, R.; Miyama, S.; Morino, J.-I.; Suto, H.; Suzuki, R.; Tamura, M.; Grady, C. A.; Sitko, M. L.; Werren, C.; Day, A. N.; Beerman, C.; Iye, M.; Lynch, D. K.; Russell, R. W.; Brafford, S. M.

    2012-01-01

    One of the key predictions of modeling from the IR excess of Herbig Ae stars is that for protoplanetary disks, where significant grain growth and settling has occurred, the dust disk has flattened to the point that it can be partially or largely shadowed by the innermost material at or near the dust sublimation radius. When the self-shadowing has already started, the outer disk is expected to be detected in scattered light only in the exceptional cases that the scale height of the dust disk at the sublimation radius is smaller than usual. High-contrast imaging combined with the IR spectral energy distribution allow us to measure the degree of flattening of the disk, as well as to determine the properties of the outer disk. We present polarimetric differential imaging in H band obtained with Subaru/HiCIAO of one such system, MWC 480. The HiCIAO data were obtained at a historic minimum of the NIR excess. The disk is detected in scattered light from 0".2-1"0 (27.4-137 AU). Together with the marginal detection of the disk from 1998 February 24 by HST / NICMOS, our data constrain the opening half angle for the disk to lie between 1.3 <= Theta <=2.2 deg. When compared with similar measures in CO for the gas disk from the literature, the dust disk subtends only approx 30% of the gas disk scale height (H/R approx 0. 03). Such a dust disk is a factor of 5-7 flatter than transitional disks, which have structural signatures that giant planets have formed.

  6. Photoacoustic contrast imaging of biological tissues with nanodiamonds fabricated for high near-infrared absorbance

    PubMed Central

    Zhang, Ti; Cui, Huizhong; Fang, Chia-Yi; Su, Long-Jyun; Ren, Shenqiang; Chang, Huan-Cheng; Yang, Xinmai

    2013-01-01

    Abstract. Radiation-damaged nanodiamonds (DNDs) are potentially ideal optical contrast agents for photoacoustic (PA) imaging in biological tissues due to their low toxicity and high optical absorbance. PA imaging contrast agents have been limited to quantum dots and gold particles, since most existing carbon-based nanoparticles, including fluorescent nanodiamonds, do not have sufficient optical absorption in the near-infrared (NIR) range. A new DND by He+ ion beam irradiation with very high NIR absorption was synthesized. These DNDs produced a 71-fold higher PA signal on a molar basis than similarly dimensioned gold nanorods, and 7.1 fmol of DNDs injected into rodents could be clearly imaged 3 mm below the skin surface with PA signal enhancement of 567% using an 820-nm laser wavelength. PMID:23400417

  7. Mueller matrix group theory formalism for tissue imaging polarimetry contrast increase.

    PubMed

    Fanjul-Vélez, Felix; Samperio-García, David; Pereda-Cubián, David; Arce-Diego, José L

    2007-01-01

    Optical characterization techniques provide a new approach to diagnostic imaging, with features such as a noninvasive or nonionizing character, as long as a resolution improvement. Intensity based measurements could be not enough for certain cases, and polarization information should be also used as a contrast parameter. Imaging polarimetry could be useful in many biomedical applications like dermatology or ophthalmology. Furthermore, it could be applied to the study of internal tissues through the use of optical fiber endoscopes, much less invasive that conventional biopsy. In this work the use of polarization parameters like the entropy factor, polarization components crosstalks or linear and circular polarization degrees is proposed as a way of improving tissue imaging contrast.

  8. Laser speckle contrast imaging with extended depth of field for in-vivo tissue imaging

    PubMed Central

    Sigal, Iliya; Gad, Raanan; Caravaca-Aguirre, Antonio M.; Atchia, Yaaseen; Conkey, Donald B.; Piestun, Rafael; Levi, Ofer

    2013-01-01

    This work presents, to our knowledge, the first demonstration of the Laser Speckle Contrast Imaging (LSCI) technique with extended depth of field (DOF). We employ wavefront coding on the detected beam to gain quantitative information on flow speeds through a DOF extended two-fold compared to the traditional system. We characterize the system in-vitro using controlled microfluidic experiments, and apply it in-vivo to imaging the somatosensory cortex of a rat, showing improved ability to image flow in a larger number of vessels simultaneously. PMID:24466481

  9. Laser speckle contrast imaging with extended depth of field for in-vivo tissue imaging.

    PubMed

    Sigal, Iliya; Gad, Raanan; Caravaca-Aguirre, Antonio M; Atchia, Yaaseen; Conkey, Donald B; Piestun, Rafael; Levi, Ofer

    2013-12-06

    This work presents, to our knowledge, the first demonstration of the Laser Speckle Contrast Imaging (LSCI) technique with extended depth of field (DOF). We employ wavefront coding on the detected beam to gain quantitative information on flow speeds through a DOF extended two-fold compared to the traditional system. We characterize the system in-vitro using controlled microfluidic experiments, and apply it in-vivo to imaging the somatosensory cortex of a rat, showing improved ability to image flow in a larger number of vessels simultaneously.

  10. X-ray phase-contrast tomography for high-spatial-resolution zebrafish muscle imaging

    NASA Astrophysics Data System (ADS)

    Vågberg, William; Larsson, Daniel H.; Li, Mei; Arner, Anders; Hertz, Hans M.

    2015-11-01

    Imaging of muscular structure with cellular or subcellular detail in whole-body animal models is of key importance for understanding muscular disease and assessing interventions. Classical histological methods for high-resolution imaging methods require excision, fixation and staining. Here we show that the three-dimensional muscular structure of unstained whole zebrafish can be imaged with sub-5 μm detail with X-ray phase-contrast tomography. Our method relies on a laboratory propagation-based phase-contrast system tailored for detection of low-contrast 4-6 μm subcellular myofibrils. The method is demonstrated on 20 days post fertilization zebrafish larvae and comparative histology confirms that we resolve individual myofibrils in the whole-body animal. X-ray imaging of healthy zebrafish show the expected structured muscle pattern while specimen with a dystrophin deficiency (sapje) displays an unstructured pattern, typical of Duchenne muscular dystrophy. The method opens up for whole-body imaging with sub-cellular detail also of other types of soft tissue and in different animal models.

  11. Evaluation of edge effect due to phase contrast imaging for mammography.

    PubMed

    Matsuo, Satoru; Katafuchi, Tetsuro; Tohyama, Keiko; Morishita, Junji; Yamada, Katsuhiko; Fujita, Hiroshi

    2005-08-01

    It is well-known that the edge effect produced by phase contrast imaging results in the edge enhancement of x-ray images and thereby sharpens those images. It has recently been reported that phase contrast imaging using practical x-ray tubes with small focal spots has improved image sharpness as observed in the phase contrast imaging with x-ray from synchrotron radiation or micro-focus x-ray tubes. In this study, we conducted the phase contrast imaging of a plastic fiber and plant seeds using a customized mammography equipment with a 0.1 mm focal spot, and the improvement of image sharpness was evaluated in terms of spatial frequency response of the images. We observed that the image contrast of the plastic fiber was increased by edge enhancement, and, as predicted elsewhere, spectral analysis revealed that as the spatial frequencies of the x-ray images increased, so did the sharpness gained through phase contrast imaging. Thus, phase contrast imaging using a practical molybdenum anode tube with a 0.1 mm-focal spot would benefit mammography, in which the morphological detectability of small species such as microcalcifications is of great concern. And detectability of tumor-surrounded glandular tissues in dense breast would be also improved by the phase contrast imaging.

  12. Big-data x-ray phase contrast imaging simulation challenges

    NASA Astrophysics Data System (ADS)

    Jimenez, Edward S.; Dagel, Amber L.

    2015-08-01

    This position paper describes a potential implementation of a large-scale grating-based X-ray Phase Contrast Imaging System (XPCI) simulation tool along with the associated challenges in its implementation. This work proposes an implementation based off of an implementation by Peterzol et. al. where each grating is treated as an object imaged in the field-of-view. Two main challenges exist; the first, is the required sampling and information management in object space due to the micron-scale periods of each grating propagating over significant distances. The second is maintaining algorithmic numerical stability for imaging systems relevant to industrial applications. We present preliminary results for a numerical stability study using a simplified algorithm that performs Talbot imaging in a big-data context

  13. X-ray Scatter Imaging of Hepatocellular Carcinoma in a Mouse Model Using Nanoparticle Contrast Agents.

    PubMed

    Rand, Danielle; Derdak, Zoltan; Carlson, Rolf; Wands, Jack R; Rose-Petruck, Christoph

    2015-10-29

    Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide and is almost uniformly fatal. Current methods of detection include ultrasound examination and imaging by CT scan or MRI; however, these techniques are problematic in terms of sensitivity and specificity, and the detection of early tumors (<1 cm diameter) has proven elusive. Better, more specific, and more sensitive detection methods are therefore urgently needed. Here we discuss the application of a newly developed x-ray imaging technique called Spatial Frequency Heterodyne Imaging (SFHI) for the early detection of HCC. SFHI uses x-rays scattered by an object to form an image and is more sensitive than conventional absorption-based x-radiography. We show that tissues labeled in vivo with gold nanoparticle contrast agents can be detected using SFHI. We also demonstrate that directed targeting and SFHI of HCC tumors in a mouse model is possible through the use of HCC-specific antibodies. The enhanced sensitivity of SFHI relative to currently available techniques enables the x-ray imaging of tumors that are just a few millimeters in diameter and substantially reduces the amount of nanoparticle contrast agent required for intravenous injection relative to absorption-based x-ray imaging.

  14. X-ray scatter imaging of hepatocellular carcinoma in a mouse model using nanoparticle contrast agents

    DOE PAGES

    Rand, Danielle; Derdak, Zoltan; Carlson, Rolf; ...

    2015-10-29

    Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide and is almost uniformly fatal. Current methods of detection include ultrasound examination and imaging by CT scan or MRI; however, these techniques are problematic in terms of sensitivity and specificity, and the detection of early tumors (<1 cm diameter) has proven elusive. Better, more specific, and more sensitive detection methods are therefore urgently needed. Here we discuss the application of a newly developed x-ray imaging technique called Spatial Frequency Heterodyne Imaging (SFHI) for the early detection of HCC. SFHI uses x-rays scattered by an object to form anmore » image and is more sensitive than conventional absorption-based x-radiography. We show that tissues labeled in vivo with gold nanoparticle contrast agents can be detected using SFHI. We also demonstrate that directed targeting and SFHI of HCC tumors in a mouse model is possible through the use of HCC-specific antibodies. As a result, the enhanced sensitivity of SFHI relative to currently available techniques enables the x-ray imaging of tumors that are just a few millimeters in diameter and substantially reduces the amount of nanoparticle contrast agent required for intravenous injection relative to absorption-based x-ray imaging.« less

  15. X-ray scatter imaging of hepatocellular carcinoma in a mouse model using nanoparticle contrast agents

    SciTech Connect

    Rand, Danielle; Derdak, Zoltan; Carlson, Rolf; Wands, Jack R.; Rose-Petruck, Christoph

    2015-10-29

    Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide and is almost uniformly fatal. Current methods of detection include ultrasound examination and imaging by CT scan or MRI; however, these techniques are problematic in terms of sensitivity and specificity, and the detection of early tumors (<1 cm diameter) has proven elusive. Better, more specific, and more sensitive detection methods are therefore urgently needed. Here we discuss the application of a newly developed x-ray imaging technique called Spatial Frequency Heterodyne Imaging (SFHI) for the early detection of HCC. SFHI uses x-rays scattered by an object to form an image and is more sensitive than conventional absorption-based x-radiography. We show that tissues labeled in vivo with gold nanoparticle contrast agents can be detected using SFHI. We also demonstrate that directed targeting and SFHI of HCC tumors in a mouse model is possible through the use of HCC-specific antibodies. As a result, the enhanced sensitivity of SFHI relative to currently available techniques enables the x-ray imaging of tumors that are just a few millimeters in diameter and substantially reduces the amount of nanoparticle contrast agent required for intravenous injection relative to absorption-based x-ray imaging.

  16. Simulating contrast inversion in atomic force microscopy imaging with real-space pseudopotentials

    NASA Astrophysics Data System (ADS)

    Lee, Alex J.; Sakai, Yuki; Chelikowsky, James R.

    2017-02-01

    Atomic force microscopy (AFM) measurements have reported contrast inversions for systems such as Cu2N and graphene that can hamper image interpretation and characterization. Here, we apply a simulation method based on ab initio real-space pseudopotentials to gain an understanding of the tip-sample interactions that influence the inversion. We find that chemically reactive tips induce an attractive binding force that results in the contrast inversion. We find that the inversion is tip height dependent and not observed when using less reactive CO-functionalized tips.

  17. Exploring Planetary System Evolution Through High-Contrast Imaging

    NASA Astrophysics Data System (ADS)

    Esposito, Thomas; Fitzgerald, Michael P.; Kalas, Paul; Graham, James R.; Millar-Blanchaer, Max; Gpies Team

    2015-01-01

    Direct imaging of circumstellar disks provides unique information about planetary system construction and evolution. Several hundred nearby main-sequence stars are known to host debris disks, which are produced by mutual collisions of orbiting planetesimals during a phase thought to coincide with terrestrial planet formation. Therefore, detection of the dust in such systems through scattered near-infrared starlight offers a view of the circumstellar environment during the epoch of planet assembly. We have used ground-based coronagraphic angular differential imaging (ADI) with Keck NIRC2 and Gemini Planet Imager (GPI) to investigate disk structures that may act as signposts of planets. ADI and its associated image processing algorithms (e.g., LOCI) are powerful tools for suppressing the stellar PSF and quasistatic speckles that can contaminate disk signal. However, ADI PSF-subtraction also attenuates disk surface brightness in a spatially- and parameter-dependent manner, thereby biasing photometry and compromising inferences regarding the physical processes responsible for the dust distribution. To account for this disk "self-subtraction," we developed a novel technique to forward model the disk structure and compute a self-subtraction map for a given ADI-processed image. Applying this method to NIRC2 near-IR imaging of the HD 32297 debris disk, we combined the high signal-to-noise ratio (S/N) of ADI data with unbiased photometry to measure midplane curvature in the edge-on disk and a break in the disk's radial brightness profile. Such a break may indicate the location of a planetesimal ring that is a source of the light-scattering micron-sized grains. For the HD 61005 debris disk, we examined similar data together with GPI 1.6-micron polarization data and detected the dust ring's swept-back morphology, brightness asymmetry, stellocentric offset, and inner clearing. To study the physical mechanism behind these features, we explored how eccentricity and mutual

  18. Achieving High Contrast for Exoplanet Imaging with a Kalman Filter and Stroke Minimization

    NASA Astrophysics Data System (ADS)

    Eldorado Riggs, A. J.; Groff, T. D.; Kasdin, N. J.; Carlotti, A.; Vanderbei, R. J.

    2014-01-01

    research in coronagraphy and wavefront control and estimation are improving our readiness for a space-based mission to image exoplanets at high contrast.

  19. Three-dimensional differential interference contrast microscopy using synthetic aperture imaging

    PubMed Central

    Kim, Moonseok; Choi, Youngwoon; Fang-Yen, Christopher; Sung, Yongjin; Kim, Kwanhyung; Dasari, Ramachandra R.; Feld, Michael S.

    2012-01-01

    Abstract. We implement differential interference contrast (DIC) microscopy using high-speed synthetic aperture imaging that expands the passband of coherent imaging by a factor of 2.2. For an aperture synthesized coherent image, we apply for the numerical post-processing and obtain a high-contrast DIC image for arbitrary shearing direction and bias retardation. In addition, we obtain images at different depths without a scanning objective lens by numerically propagating the acquired coherent images. Our method achieves high-resolution and high-contrast 3-D DIC imaging of live biological cells. The proposed method will be useful for monitoring 3-D dynamics of intracellular particles. PMID:22463035

  20. X-ray Phase Contrast Imaging of Calcified Tissue and Biomaterial Structure in Bioreactor Engineered Tissues

    SciTech Connect

    Appel, Alyssa A.; Larson, Jeffery C.; Garson, III, Alfred B.; Guan, Huifeng; Zhong, Zhong; Nguyen, Bao-Ngoc; Fisher, John P.; Anastasio, Mark A.; B