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Sample records for adaptive contrast enhancement

  1. Adaptive color contrast enhancement for digital images

    NASA Astrophysics Data System (ADS)

    Wang, Yanfang; Luo, Yupin

    2011-11-01

    Noncanonical illumination that is too dim or with color cast induces degenerated images. To cope with this, we propose a method for color-contrast enhancement. First, intensity, chrominance, and contrast characteristics are explored and integrated in the Naka-Rushton equation to remove underexposure and color cast simultaneously. Motivated by the comparison mechanism in Retinex, the ratio of each pixel to its surroundings is utilized to improve image contrast. Finally, inspired by the two color-opponent dimensions in CIELAB space, a color-enhancement strategy is devised based on the transformation from CIEXYZ to CIELAB color space. For images that suffer from underexposure, color cast, or both problems, our algorithm produces promising results without halo artifacts and corruption of uniform areas.

  2. An adaptive algorithm for low contrast infrared image enhancement

    NASA Astrophysics Data System (ADS)

    Liu, Sheng-dong; Peng, Cheng-yuan; Wang, Ming-jia; Wu, Zhi-guo; Liu, Jia-qi

    2013-08-01

    An adaptive infrared image enhancement algorithm for low contrast is proposed in this paper, to deal with the problem that conventional image enhancement algorithm is not able to effective identify the interesting region when dynamic range is large in image. This algorithm begin with the human visual perception characteristics, take account of the global adaptive image enhancement and local feature boost, not only the contrast of image is raised, but also the texture of picture is more distinct. Firstly, the global image dynamic range is adjusted from the overall, the dynamic range of original image and display grayscale form corresponding relationship, the gray scale of bright object is raised and the the gray scale of dark target is reduced at the same time, to improve the overall image contrast. Secondly, the corresponding filtering algorithm is used on the current point and its neighborhood pixels to extract image texture information, to adjust the brightness of the current point in order to enhance the local contrast of the image. The algorithm overcomes the default that the outline is easy to vague in traditional edge detection algorithm, and ensure the distinctness of texture detail in image enhancement. Lastly, we normalize the global luminance adjustment image and the local brightness adjustment image, to ensure a smooth transition of image details. A lot of experiments is made to compare the algorithm proposed in this paper with other convention image enhancement algorithm, and two groups of vague IR image are taken in experiment. Experiments show that: the contrast ratio of the picture is boosted after handled by histogram equalization algorithm, but the detail of the picture is not clear, the detail of the picture can be distinguished after handled by the Retinex algorithm. The image after deal with by self-adaptive enhancement algorithm proposed in this paper becomes clear in details, and the image contrast is markedly improved in compared with Retinex

  3. Adaptive image contrast enhancement algorithm for point-based rendering

    NASA Astrophysics Data System (ADS)

    Xu, Shaoping; Liu, Xiaoping P.

    2015-03-01

    Surgical simulation is a major application in computer graphics and virtual reality, and most of the existing work indicates that interactive real-time cutting simulation of soft tissue is a fundamental but challenging research problem in virtual surgery simulation systems. More specifically, it is difficult to achieve a fast enough graphic update rate (at least 30 Hz) on commodity PC hardware by utilizing traditional triangle-based rendering algorithms. In recent years, point-based rendering (PBR) has been shown to offer the potential to outperform the traditional triangle-based rendering in speed when it is applied to highly complex soft tissue cutting models. Nevertheless, the PBR algorithms are still limited in visual quality due to inherent contrast distortion. We propose an adaptive image contrast enhancement algorithm as a postprocessing module for PBR, providing high visual rendering quality as well as acceptable rendering efficiency. Our approach is based on a perceptible image quality technique with automatic parameter selection, resulting in a visual quality comparable to existing conventional PBR algorithms. Experimental results show that our adaptive image contrast enhancement algorithm produces encouraging results both visually and numerically compared to representative algorithms, and experiments conducted on the latest hardware demonstrate that the proposed PBR framework with the postprocessing module is superior to the conventional PBR algorithm and that the proposed contrast enhancement algorithm can be utilized in (or compatible with) various variants of the conventional PBR algorithm.

  4. 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.

  5. Efficient contrast enhancement using adaptive gamma correction with weighting distribution.

    PubMed

    Huang, Shih-Chia; Cheng, Fan-Chieh; Chiu, Yi-Sheng

    2013-03-01

    This paper proposes an efficient method to modify histograms and enhance contrast in digital images. Enhancement plays a significant role in digital image processing, computer vision, and pattern recognition. We present an automatic transformation technique that improves the brightness of dimmed images via the gamma correction and probability distribution of luminance pixels. To enhance video, the proposed image-enhancement method uses temporal information regarding the differences between each frame to reduce computational complexity. Experimental results demonstrate that the proposed method produces enhanced images of comparable or higher quality than those produced using previous state-of-the-art methods. PMID:23144035

  6. Investigation of self-adaptive LED surgical lighting based on entropy contrast enhancing method

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Wang, Huihui; Zhang, Yaqin; Shen, Junfei; Wu, Rengmao; Zheng, Zhenrong; Li, Haifeng; Liu, Xu

    2014-05-01

    Investigation was performed to explore the possibility of enhancing contrast by varying the spectral distribution (SPD) of the surgical lighting. The illumination scenes with different SPDs were generated by the combination of a self-adaptive white light optimization method and the LED ceiling system, the images of biological sample are taken by a CCD camera and then processed by an 'Entropy' based contrast evaluation model which is proposed specific for surgery occasion. Compared with the neutral white LED based and traditional algorithm based image enhancing methods, the illumination based enhancing method turns out a better performance in contrast enhancing and improves the average contrast value about 9% and 6%, respectively. This low cost method is simple, practicable, and thus may provide an alternative solution for the expensive visual facility medical instruments.

  7. Adaptive luminance contrast for enhancing reading performance and visual comfort on smartphone displays

    NASA Astrophysics Data System (ADS)

    Na, Nooree; Suk, Hyeon-Jeong

    2014-11-01

    This study developed a model for setting the adaptive luminance contrast between text and background for enhancing reading performance and visual comfort on smartphone displays. The study was carried out in two experiments. In Experiment I, a user test was conducted to identify the optimal luminance contrast with regard to subjects' reading performance, measured by lines of text reading and visual comfort, assessed by self-report after the reading. Based on the empirical results of the test, an ideal adaptive model which decreases the luminance contrast gradually with passage of time was developed. In Experiment II, a validation test involving reading performance, visual comfort, and physiological stress measured by a brainwave analysis using an electroencephalogram confirmed that the proposed adaptive luminance contrast is adequate for prolonged text reading on smartphone displays. The developed model enhances both reading performance and visual comfort as well as reduces the energy consumption of a smartphone; hence, it is expected that this study will be applied to diverse kinds of visual display terminals.

  8. Contrast enhancement in microscopy of human thyroid tumors by means of acousto-optic adaptive spatial filtering

    NASA Astrophysics Data System (ADS)

    Yushkov, Konstantin B.; Molchanov, Vladimir Y.; Belousov, Pavel V.; Abrosimov, Aleksander Y.

    2016-01-01

    We report a method for edge enhancement in the images of transparent samples using analog image processing in coherent light. The experimental technique is based on adaptive spatial filtering with an acousto-optic tunable filter in a telecentric optical system. We demonstrate processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.

  9. Noise correlation-based adaptive polarimetric image representation for contrast enhancement of a polarized beacon in fog

    NASA Astrophysics Data System (ADS)

    Panigrahi, Swapnesh; Fade, Julien; Alouini, Mehdi

    2015-10-01

    We show the use of a simplified snapshot polarimetric camera along with an adaptive image processing for optimal detection of a polarized light beacon through fog. The adaptive representation is derived using theoretical noise analysis of the data at hand and is shown to be optimal in the Maximum likelihood sense. We report that the contrast enhancing optimal representation that depends on the background noise correlation differs in general from standard representations like polarimetric difference image or polarization filtered image. Lastly, we discuss a detection strategy to reduce the false positive counts.

  10. An innovative technique for contrast enhancement of computed tomography images using normalized gamma-corrected contrast-limited adaptive histogram equalization

    NASA Astrophysics Data System (ADS)

    Al-Ameen, Zohair; Sulong, Ghazali; Rehman, Amjad; Al-Dhelaan, Abdullah; Saba, Tanzila; Al-Rodhaan, Mznah

    2015-12-01

    Image contrast is an essential visual feature that determines whether an image is of good quality. In computed tomography (CT), captured images tend to be low contrast, which is a prevalent artifact that reduces the image quality and hampers the process of extracting its useful information. A common tactic to process such artifact is by using histogram-based techniques. However, although these techniques may improve the contrast for different grayscale imaging applications, the results are mostly unacceptable for CT images due to the presentation of various faults, noise amplification, excess brightness, and imperfect contrast. Therefore, an ameliorated version of the contrast-limited adaptive histogram equalization (CLAHE) is introduced in this article to provide a good brightness with decent contrast for CT images. The novel modification to the aforesaid technique is done by adding an initial phase of a normalized gamma correction function that helps in adjusting the gamma of the processed image to avoid the common errors of the basic CLAHE of the excess brightness and imperfect contrast it produces. The newly developed technique is tested with synthetic and real-degraded low-contrast CT images, in which it highly contributed in producing better quality results. Moreover, a low intricacy technique for contrast enhancement is proposed, and its performance is also exhibited against various versions of histogram-based enhancement technique using three advanced image quality assessment metrics of Universal Image Quality Index (UIQI), Structural Similarity Index (SSIM), and Feature Similarity Index (FSIM). Finally, the proposed technique provided acceptable results with no visible artifacts and outperformed all the comparable techniques.

  11. Enhancement tuning and control for high dynamic range images in multi-scale locally adaptive contrast enhancement algorithms

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Sascha D.; Schirris, Johan; de With, Peter H. N.

    2009-01-01

    For real-time imaging in surveillance applications, visibility of details is of primary importance to ensure customer confidence. If we display High Dynamic-Range (HDR) scenes whose contrast spans four or more orders of magnitude on a conventional monitor without additional processing, results are unacceptable. Compression of the dynamic range is therefore a compulsory part of any high-end video processing chain because standard monitors are inherently Low- Dynamic Range (LDR) devices with maximally two orders of display dynamic range. In real-time camera processing, many complex scenes are improved with local contrast enhancements, bringing details to the best possible visibility. In this paper, we show how a multi-scale high-frequency enhancement scheme, in which gain is a non-linear function of the detail energy, can be used for the dynamic range compression of HDR real-time video camera signals. We also show the connection of our enhancement scheme to the processing way of the Human Visual System (HVS). Our algorithm simultaneously controls perceived sharpness, ringing ("halo") artifacts (contrast) and noise, resulting in a good balance between visibility of details and non-disturbance of artifacts. The overall quality enhancement, suitable for both HDR and LDR scenes, is based on a careful selection of the filter types for the multi-band decomposition and a detailed analysis of the signal per frequency band.

  12. Pattern specificity of contrast adaptation

    PubMed Central

    Anstis, Stuart

    2014-01-01

    Contrast adaptation is specific to precisely localised edges, so that adapting to a flickering photograph makes one less sensitive to that same photograph, but not to similar photographs. When two low-contrast photos, A and B, are transparently superimposed, then adapting to a flickering high-contrast B leaves no net afterimage, but it makes B disappear from the A+B picture, which now simply looks like A. PMID:25165518

  13. Multi-band locally-adaptive contrast enhancement algorithm with built-in noise and artifact suppression mechanisms

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Sascha D.; Schirris, Johan; de With, Peter H. N.

    2008-01-01

    For real-time imaging in surveillance applications, visibility of details is of primary importance to ensure customer confidence. Usually, image quality is improved by enhancing contrast and sharpness. Many complex scenes require local contrast improvements that should bring details to the best possible visibility. However, local enhancement methods mainly suffer from ringing artifacts and noise over-enhancement. In this paper, we present a new multi-window real-time high-frequency enhancement scheme, in which gain is a non-linear function of the detail energy. Our algorithm simultaneously controls perceived sharpness, ringing artifacts (contrast) and noise, resulting in a good balance between visibility of details and non-disturbance of artifacts. The overall quality enhancement is based on a careful selection of the filter types for the multi-band decomposition and a detailed analysis of the signal per frequency band. The advantage of the proposed technique is that detail gains can be set much higher than usual and the algorithm will reduce them only at places where it is really needed.

  14. Contrast Adaptation Implies Two Spatiotemporal Channels but Three Adapting Processes

    ERIC Educational Resources Information Center

    Langley, Keith; Bex, Peter J.

    2007-01-01

    The contrast gain control model of adaptation predicts that the effects of contrast adaptation correlate with contrast sensitivity. This article reports that the effects of high contrast spatiotemporal adaptors are maximum when adapting around 19 Hz, which is a factor of two or more greater than the peak in contrast sensitivity. To explain the…

  15. Contrast adaptation in the Limulus lateral eye.

    PubMed

    Valtcheva, Tchoudomira M; Passaglia, Christopher L

    2015-12-01

    Luminance and contrast adaptation are neuronal mechanisms employed by the visual system to adjust our sensitivity to light. They are mediated by an assortment of cellular and network processes distributed across the retina and visual cortex. Both have been demonstrated in the eyes of many vertebrates, but only luminance adaptation has been shown in invertebrate eyes to date. Since the computational benefits of contrast adaptation should apply to all visual systems, we investigated whether this mechanism operates in horseshoe crab eyes, one of the best-understood neural networks in the animal kingdom. The spike trains of optic nerve fibers were recorded in response to light stimuli modulated randomly in time and delivered to single ommatidia or the whole eye. We found that the retina adapts to both the mean luminance and contrast of a white-noise stimulus, that luminance- and contrast-adaptive processes are largely independent, and that they originate within an ommatidium. Network interactions are not involved. A published computer model that simulates existing knowledge of the horseshoe crab eye did not show contrast adaptation, suggesting that a heretofore unknown mechanism may underlie the phenomenon. This mechanism does not appear to reside in photoreceptors because white-noise analysis of electroretinogram recordings did not show contrast adaptation. The likely site of origin is therefore the spike discharge mechanism of optic nerve fibers. The finding of contrast adaption in a retinal network as simple as the horseshoe crab eye underscores the broader importance of this image processing strategy to vision. PMID:26445869

  16. Contrast adaptation to luminance and brightness modulations.

    PubMed

    Nagai, Takehiro; Nakayama, Kazuki; Kawashima, Yuki; Yamauchi, Yasuki

    2016-03-01

    Perceptual brightness and color contrast decrease after seeing a light temporally modulating along a certain direction in a color space, a phenomenon known as contrast adaptation. We investigated whether contrast adaptation along the luminance direction arises from modulation of luminance signals or apparent brightness signals. The stimulus consisted of two circles on a gray background presented on a CRT monitor. In the adaptation phase, the luminance and chromaticity of one circle were temporally modulated, while the other circle was kept at a constant luminance and color metameric with an equal-energy white. We employed two types of temporal modulations, namely, in luminance and brightness. Chromaticity was sinusoidally modulated along the L-M axis, leading to dissociation between luminance and brightness (the Helmholtz-Kohlrausch effect). In addition, luminance modulation was minimized in the brightness modulation, while brightness modulation was minimized in the luminance modulation. In the test phase, an asymmetric matching method was used to measure the magnitude of contrast adaptation for both modulations. Our results showed that, although contrast adaptation along the luminance direction occurred for both modulations, contrast adaptation for luminance modulation was significantly stronger than that for the brightness modulation regardless of the temporal frequency of the adaptation modulation. These results suggest that luminance modulation is more influential in contrast adaptation than brightness modulation.

  17. Contrast adaptation in the Limulus lateral eye.

    PubMed

    Valtcheva, Tchoudomira M; Passaglia, Christopher L

    2015-12-01

    Luminance and contrast adaptation are neuronal mechanisms employed by the visual system to adjust our sensitivity to light. They are mediated by an assortment of cellular and network processes distributed across the retina and visual cortex. Both have been demonstrated in the eyes of many vertebrates, but only luminance adaptation has been shown in invertebrate eyes to date. Since the computational benefits of contrast adaptation should apply to all visual systems, we investigated whether this mechanism operates in horseshoe crab eyes, one of the best-understood neural networks in the animal kingdom. The spike trains of optic nerve fibers were recorded in response to light stimuli modulated randomly in time and delivered to single ommatidia or the whole eye. We found that the retina adapts to both the mean luminance and contrast of a white-noise stimulus, that luminance- and contrast-adaptive processes are largely independent, and that they originate within an ommatidium. Network interactions are not involved. A published computer model that simulates existing knowledge of the horseshoe crab eye did not show contrast adaptation, suggesting that a heretofore unknown mechanism may underlie the phenomenon. This mechanism does not appear to reside in photoreceptors because white-noise analysis of electroretinogram recordings did not show contrast adaptation. The likely site of origin is therefore the spike discharge mechanism of optic nerve fibers. The finding of contrast adaption in a retinal network as simple as the horseshoe crab eye underscores the broader importance of this image processing strategy to vision.

  18. Impact of adaptation time on contrast sensitivity

    NASA Astrophysics Data System (ADS)

    Apelt, Dörte; Strasburger, Hans; Klein, Jan; Preim, Bernhard

    2010-02-01

    For softcopy-reading of mammograms, a room illuminance of 10 lx is recommended in standard procedures. Room illuminance affects both the maximal monitor contrast and the global luminance adaptation of the visual system. A radiologist observer has to adapt to low luminance levels, when entering the reading room. Since the observer's sensitivity to low-contrast patterns depends on adaptation state and processes, it would be expected that the contrast sensitivity is lower at the beginning of a reading session. We investigated the effect of an initial time of dark adaptation on the contrast sensitivity. A study with eight observers was conducted in the context of mammographic softcopy-reading. Using Gabor patterns with varying spatial frequency, orientation, and contrast level as stimuli in an orientation discrimination task, the intra-observer contrast sensitivity was determined for foveal vision. Before performing the discrimination task, the observers adapted for two minutes to an average illuminance of 450 lx. Thereafter, contrast thresholds were repeatedly measured at 10 lx room illuminance over a course of 15 minutes. The results show no significant variations in contrast sensitivity during the 15 minutes period. Thus, it can be concluded that taking an initial adaptation time does not affect the perception of lowcontrast objects in mammographic images presented in the typical softcopy-reading environment. Therefore, the reading performance would not be negatively influenced when the observer started immediately with reading of mammograms. The results can be used to optimize the workflow in the radiology reading room.

  19. Rapid contrast gain reduction following motion adaptation.

    PubMed

    Nordström, Karin; Moyer de Miguel, Irene; O'Carroll, David C

    2011-12-01

    Neural and sensory systems adapt to prolonged stimulation to allow signaling across broader input ranges than otherwise possible with the limited bandwidth of single neurons and receptors. In the visual system, adaptation takes place at every stage of processing, from the photoreceptors that adapt to prevailing luminance conditions, to higher-order motion-sensitive neurons that adapt to prolonged exposure to motion. Recent experiments using dynamic, fluctuating visual stimuli indicate that adaptation operates on a time scale similar to that of the response itself. Further work from our own laboratory has highlighted the role for rapid motion adaptation in reliable encoding of natural image motion. Physiologically, motion adaptation can be broken down into four separate components. It is not clear from the previous studies which of these motion adaptation components are involved in the fast and dynamic response changes. To investigate the adapted response in more detail, we therefore analyzed the effect of motion adaptation using a test-adapt-test protocol with adapting durations ranging from 20 ms to 20 s. Our results underscore the very rapid rate of motion adaptation, suggesting that under free flight, visual motion-sensitive neurons continuously adapt to the changing scenery. This might help explain recent observations of strong invariance in the response to natural scenes with highly variable contrast and image structure.

  20. Temporal subtraction contrast-enhanced dedicated breast CT.

    PubMed

    Gazi, Peymon M; Aminololama-Shakeri, Shadi; Yang, Kai; Boone, John M

    2016-09-01

    The development of a framework of deformable image registration and segmentation for the purpose of temporal subtraction contrast-enhanced breast CT is described. An iterative histogram-based two-means clustering method was used for the segmentation. Dedicated breast CT images were segmented into background (air), adipose, fibroglandular and skin components. Fibroglandular tissue was classified as either normal or contrast-enhanced then divided into tiers for the purpose of categorizing degrees of contrast enhancement. A variant of the Demons deformable registration algorithm, intensity difference adaptive Demons (IDAD), was developed to correct for the large deformation forces that stemmed from contrast enhancement. In this application, the accuracy of the proposed method was evaluated in both mathematically-simulated and physically-acquired phantom images. Clinical usage and accuracy of the temporal subtraction framework was demonstrated using contrast-enhanced breast CT datasets from five patients. Registration performance was quantified using normalized cross correlation (NCC), symmetric uncertainty coefficient, normalized mutual information (NMI), mean square error (MSE) and target registration error (TRE). The proposed method outperformed conventional affine and other Demons variations in contrast enhanced breast CT image registration. In simulation studies, IDAD exhibited improvement in MSE (0-16%), NCC (0-6%), NMI (0-13%) and TRE (0-34%) compared to the conventional Demons approaches, depending on the size and intensity of the enhancing lesion. As lesion size and contrast enhancement levels increased, so did the improvement. The drop in the correlation between the pre- and post-contrast images for the largest enhancement levels in phantom studies is less than 1.2% (150 Hounsfield units). Registration error, measured by TRE, shows only submillimeter mismatches between the concordant anatomical target points in all patient studies. The algorithm was

  1. Temporal subtraction contrast-enhanced dedicated breast CT

    NASA Astrophysics Data System (ADS)

    Gazi, Peymon M.; Aminololama-Shakeri, Shadi; Yang, Kai; Boone, John M.

    2016-09-01

    The development of a framework of deformable image registration and segmentation for the purpose of temporal subtraction contrast-enhanced breast CT is described. An iterative histogram-based two-means clustering method was used for the segmentation. Dedicated breast CT images were segmented into background (air), adipose, fibroglandular and skin components. Fibroglandular tissue was classified as either normal or contrast-enhanced then divided into tiers for the purpose of categorizing degrees of contrast enhancement. A variant of the Demons deformable registration algorithm, intensity difference adaptive Demons (IDAD), was developed to correct for the large deformation forces that stemmed from contrast enhancement. In this application, the accuracy of the proposed method was evaluated in both mathematically-simulated and physically-acquired phantom images. Clinical usage and accuracy of the temporal subtraction framework was demonstrated using contrast-enhanced breast CT datasets from five patients. Registration performance was quantified using normalized cross correlation (NCC), symmetric uncertainty coefficient, normalized mutual information (NMI), mean square error (MSE) and target registration error (TRE). The proposed method outperformed conventional affine and other Demons variations in contrast enhanced breast CT image registration. In simulation studies, IDAD exhibited improvement in MSE (0-16%), NCC (0-6%), NMI (0-13%) and TRE (0-34%) compared to the conventional Demons approaches, depending on the size and intensity of the enhancing lesion. As lesion size and contrast enhancement levels increased, so did the improvement. The drop in the correlation between the pre- and post-contrast images for the largest enhancement levels in phantom studies is less than 1.2% (150 Hounsfield units). Registration error, measured by TRE, shows only submillimeter mismatches between the concordant anatomical target points in all patient studies. The algorithm was

  2. Temporal subtraction contrast-enhanced dedicated breast CT

    NASA Astrophysics Data System (ADS)

    Gazi, Peymon M.; Aminololama-Shakeri, Shadi; Yang, Kai; Boone, John M.

    2016-09-01

    The development of a framework of deformable image registration and segmentation for the purpose of temporal subtraction contrast-enhanced breast CT is described. An iterative histogram-based two-means clustering method was used for the segmentation. Dedicated breast CT images were segmented into background (air), adipose, fibroglandular and skin components. Fibroglandular tissue was classified as either normal or contrast-enhanced then divided into tiers for the purpose of categorizing degrees of contrast enhancement. A variant of the Demons deformable registration algorithm, intensity difference adaptive Demons (IDAD), was developed to correct for the large deformation forces that stemmed from contrast enhancement. In this application, the accuracy of the proposed method was evaluated in both mathematically-simulated and physically-acquired phantom images. Clinical usage and accuracy of the temporal subtraction framework was demonstrated using contrast-enhanced breast CT datasets from five patients. Registration performance was quantified using normalized cross correlation (NCC), symmetric uncertainty coefficient, normalized mutual information (NMI), mean square error (MSE) and target registration error (TRE). The proposed method outperformed conventional affine and other Demons variations in contrast enhanced breast CT image registration. In simulation studies, IDAD exhibited improvement in MSE (0–16%), NCC (0–6%), NMI (0–13%) and TRE (0–34%) compared to the conventional Demons approaches, depending on the size and intensity of the enhancing lesion. As lesion size and contrast enhancement levels increased, so did the improvement. The drop in the correlation between the pre- and post-contrast images for the largest enhancement levels in phantom studies is less than 1.2% (150 Hounsfield units). Registration error, measured by TRE, shows only submillimeter mismatches between the concordant anatomical target points in all patient studies. The algorithm was

  3. Adaptive changes in visual cortex following prolonged contrast reduction

    PubMed Central

    Kwon, MiYoung; Legge, Gordon E.; Fang, Fang; Cheong, Allen M. Y.; He, Sheng

    2009-01-01

    How does prolonged reduction in retinal-image contrast affect visual-contrast coding? Recent evidence indicates that some forms of long-term visual deprivation result in compensatory perceptual and neural changes in the adult visual pathway. It has not been established whether changes due to contrast adaptation are best characterized as “contrast gain” or “response gain.” We present a theoretical rationale for predicting that adaptation to long-term contrast reduction should result in response gain. To test this hypothesis, normally sighted subjects adapted for four hours by viewing their environment through contrast-reducing goggles. During the adaptation period, the subjects went about their usual daily activities. Subjects' contrast-discrimination thresholds and fMRI BOLD responses in cortical areas V1 and V2 were obtained before and after adaptation. Following adaptation, we observed a significant decrease in contrast-discrimination thresholds, and significant increase in BOLD responses in V1 and V2. The observed interocular transfer of the adaptation effect suggests that the adaptation has a cortical origin. These results reveal a new kind of adaptability of the adult visual cortex, an adjustment in the gain of the contrast-response in the presence of a reduced range of stimulus contrasts, which is consistent with a response-gain mechanism. The adaptation appears to be compensatory, such that the precision of contrast coding is improved for low retinal-image contrasts. PMID:19271930

  4. Contrast enhancement algorithm considering surrounding information by illumination image

    NASA Astrophysics Data System (ADS)

    Song, Ki Sun; Kang, Hee; Kang, Moon Gi

    2014-09-01

    We propose a contrast enhancement algorithm considering surrounding information by illumination image. Conventional contrast enhancement techniques can be classified as a retinex-based method and a tone mapping function-based method. However, many retinex methods suffer from high-computational costs or halo artifacts. To cope with these problems, efficient edge-preserving smoothing methods have been researched. Tone mapping function-based methods are limited in terms of enhancement since they are applied without considering surrounding information. To solve these problems, we estimate an illumination image with local adaptive smoothness, and then utilize it as surrounding information. The local adaptive smoothness is calculated by using illumination image properties and an edge-adaptive filter based on the just noticeable difference model. Additionally, we employ a resizing method instead of a blur kernel to reduce the computational cost of illumination estimation. The estimated illumination image is incorporated with the tone mapping function to address the limitations of the tone mapping function-based method. With this approach, the amount of local contrast enhancement is increased. Experimental results show that the proposed algorithm enhances both global and local contrasts and produces better performance in objective evaluation metrics while preventing a halo artifact.

  5. Exercise-Based Performance Enhancement and Injury Prevention for Firefighters: Contrasting the Fitness- and Movement-Related Adaptations to Two Training Methodologies.

    PubMed

    Frost, David M; Beach, Tyson A C; Callaghan, Jack P; McGill, Stuart M

    2015-09-01

    Using exercise to enhance physical fitness may have little impact on performers' movement patterns beyond the gym environment. This study examined the fitness and movement adaptations exhibited by firefighters in response to 2 training methodologies. Fifty-two firefighters were assigned to a movement-guided fitness (MOV), conventional fitness (FIT), or control (CON) group. Before and after 12 weeks of training, participants performed a fitness evaluation and laboratory-based test. Three-dimensional lumbar spine and frontal plane knee kinematics were quantified. Five whole-body tasks not included in the interventions were used to evaluate the transfer of training. FIT and MOV groups exhibited significant improvements in all aspects of fitness; however, only MOV exhibited improvements in spine and frontal plane knee motion control when performing each transfer task (effect sizes [ESs] of 0.2-1.5). FIT exhibited less controlled spine and frontal plane knee motions while squatting, lunging, pushing, and pulling (ES: 0.2-0.7). More MOV participants (43%) exhibited only positive posttraining changes (i.e., improved control), in comparison with FIT (30%) and CON (23%). Fewer negative posttraining changes were also noted (19, 25, and 36% for MOV, FIT, and CON). These findings suggest that placing an emphasis on how participants move while exercising may be an effective training strategy to elicit behavioral changes beyond the gym environment. For occupational athletes such as firefighters, soldiers, and police officers, this implies that exercise programs designed with a movement-oriented approach to periodization could have a direct impact on their safety and effectiveness by engraining desirable movement patterns that transfer to occupational tasks.

  6. Contrast-enhanced photoacoustic tomography of human joints

    NASA Astrophysics Data System (ADS)

    Tian, Chao; Keswani, Rahul K.; Gandikota, Girish; Rosania, Gus R.; Wang, Xueding

    2016-03-01

    Photoacoustic tomography (PAT) provides a unique tool to diagnose inflammatory arthritis. However, the specificity and sensitivity of PAT based on endogenous contrasts is limited. The development of contrast enhanced PAT imaging modalities in combination with small molecule contrast agents could lead to improvements in diagnosis and treatment of joint disease. Accordingly, we adapted and tested a PAT clinical imaging system for imaging the human joints, in combination with a novel PAT contrast agent derived from an FDA-approved small molecule drug. Imaging results based on a photoacoustic and ultrasound (PA/US) dual-modality system revealed that this contrast-enhanced PAT imaging system may offer additional information beyond single-modality PA or US imaging system, for the imaging, diagnosis and assessment of inflammatory arthritis.

  7. Contrast enhanced ultrasound of breast cancer

    PubMed Central

    Cassano, E; Rizzo, S; Bozzini, A; Menna, S; Bellomi, M

    2006-01-01

    The importance of ultrasound examination in the diagnosis of breast cancer has been widely demonstrated. During the last few years, the introduction of ultrasound contrast media has been considered a promising tool for studying the vascular pattern of focal lesions within the breast. Our purpose was to assess whether contrast-enhanced (CE) ultrasound examination, performed using specific contrast imaging modes, can be helpful for detection and characterization of breast lesions, and for prediction of the response of breast cancer to therapy. PMID:16478698

  8. Contrast enhanced ultrasound of breast cancer.

    PubMed

    Cassano, E; Rizzo, S; Bozzini, A; Menna, S; Bellomi, M

    2006-01-01

    The importance of ultrasound examination in the diagnosis of breast cancer has been widely demonstrated. During the last few years, the introduction of ultrasound contrast media has been considered a promising tool for studying the vascular pattern of focal lesions within the breast. Our purpose was to assess whether contrast-enhanced (CE) ultrasound examination, performed using specific contrast imaging modes, can be helpful for detection and characterization of breast lesions, and for prediction of the response of breast cancer to therapy. PMID:16478698

  9. Contrast Enhancement by Nonlinear Diffusion Filtering.

    PubMed

    Liang, Zhetong; Liu, Weijian; Yao, Ruohe

    2016-02-01

    To enhance the visual quality of an image that is degraded by uneven light, an effective method is to estimate the illumination component and compress it. Some previous methods have either defects of halo artifacts or contrast loss in the enhanced image due to incorrect estimation. In this paper, we discuss this problem and propose a novel method to estimate the illumination. The illumination is obtained by iteratively solving a nonlinear diffusion equation. During the diffusion process, surround suppression is embedded in the conductance function to specially enhance the diffusive strength in textural areas of the image. The proposed estimation method has the following two merits: 1) the boundary areas are preserved in the illumination, and thus halo artifacts are prevented and 2) the textural details are preserved in the reflectance to not suffer from illumination compression, which contributes to the contrast enhancement in the result. Experimental results show that the proposed algorithm achieves excellent performance in artifact removal and local contrast enhancement. PMID:26685234

  10. Adaptation to stimulus contrast and correlations during natural visual stimulation

    PubMed Central

    Lesica, Nicholas A.; Jin, Jianzhong; Weng, Chong; Yeh, Chun-I; Butts, Daniel A.; Stanley, Garrett B.; Alonso, Jose-Manuel

    2008-01-01

    Summary In this study, we characterize the adaptation of neurons in the cat lateral geniculate nucleus to changes in stimulus contrast and correlations. By comparing responses to high and low contrast natural scene movie and white noise stimuli, we show that an increase in contrast or correlations results in receptive fields with faster temporal dynamics and stronger antagonistic surrounds, as well as decreases in gain and selectivity. We also observe contrast- and correlation-induced changes in the reliability and sparseness of neural responses. We find that reliability is determined primarily by processing in the receptive field (the effective contrast of the stimulus), while sparseness is determined by the interactions between several functional properties. These results reveal a number of novel adaptive phenomena and suggest that adaptation to stimulus contrast and correlations may play an important role in visual coding in a dynamic natural environment. PMID:17678859

  11. 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.

  12. 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. PMID:26945462

  13. Contrast-enhanced and targeted ultrasound

    PubMed Central

    Postema, Michiel; Gilja, Odd Helge

    2011-01-01

    Ultrasonic imaging is becoming the most popular medical imaging modality, owing to the low price per examination and its safety. However, blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit frequencies. For perfusion imaging, markers have been designed to enhance the contrast in B-mode imaging. These so-called ultrasound contrast agents consist of microscopically small gas bubbles encapsulated in biodegradable shells. In this review, the physical principles of ultrasound contrast agent microbubble behavior and their adjustment for drug delivery including sonoporation are described. Furthermore, an outline of clinical imaging applications of contrast-enhanced ultrasound is given. It is a challenging task to quantify and predict which bubble phenomenon occurs under which acoustic condition, and how these phenomena may be utilized in ultrasonic imaging. Aided by high-speed photography, our improved understanding of encapsulated microbubble behavior will lead to more sophisticated detection and delivery techniques. More sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves, and have shown great promise in revealing effective tumor responses to anti-angiogenic drugs in humans before tumor shrinkage occurs. These are beginning to be accepted into clinical practice. In the long term, targeted microbubbles for molecular imaging and eventually for directed anti-tumor therapy are expected to be tested. PMID:21218081

  14. MRI contrast enhancement using Magnetic Carbon Nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaudhary, Rakesh P.; Kangasniemi, Kim; Takahashi, Masaya; Mohanty, Samarendra K.; Koymen, Ali R.; Department of Physics, University of Texas at Arlington Team; University of Texas Southwestern Medical Center Team

    2014-03-01

    In recent years, nanotechnology has become one of the most exciting forefront fields in cancer diagnosis and therapeutics such as drug delivery, thermal therapy and detection of cancer. Here, we report development of core (Fe)-shell (carbon) nanoparticles with enhanced magnetic properties for contrast enhancement in MRI imaging. These new classes of magnetic carbon nanoparticles (MCNPs) are synthesized using a bottom-up approach in various organic solvents, using the electric plasma discharge generated in the cavitation field of an ultrasonic horn. Gradient echo MRI images of well-dispersed MCNP-solutions (in tube) were acquired. For T2 measurements, a multi echo spin echo sequence was performed. From the slope of the 1/T2 versus concentration plot, the R2 value for different CMCNP-samples was measured. Since MCNPs were found to be extremely non-reactive, and highly absorbing in NIR regime, development of carbon-based MRI contrast enhancement will allow its simultaneous use in biomedical applications. We aim to localize the MCNPs in targeted tissue regions by external DC magnetic field, followed by MRI imaging and subsequent photothermal therapy.

  15. Quantitative contrast-enhanced optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Winetraub, Yonatan; SoRelle, Elliott D.; Liba, Orly; de la Zerda, Adam

    2016-01-01

    We have developed a model to accurately quantify the signals produced by exogenous scattering agents used for contrast-enhanced Optical Coherence Tomography (OCT). This model predicts distinct concentration-dependent signal trends that arise from the underlying physics of OCT detection. Accordingly, we show that real scattering particles can be described as simplified ideal scatterers with modified scattering intensity and concentration. The relation between OCT signal and particle concentration is approximately linear at concentrations lower than 0.8 particle per imaging voxel. However, at higher concentrations, interference effects cause signal to increase with a square root dependence on the number of particles within a voxel. Finally, high particle concentrations cause enough light attenuation to saturate the detected signal. Predictions were validated by comparison with measured OCT signals from gold nanorods (GNRs) prepared in water at concentrations ranging over five orders of magnitude (50 fM to 5 nM). In addition, we validated that our model accurately predicts the signal responses of GNRs in highly heterogeneous scattering environments including whole blood and living animals. By enabling particle quantification, this work provides a valuable tool for current and future contrast-enhanced in vivo OCT studies. More generally, the model described herein may inform the interpretation of detected signals in modalities that rely on coherence-based detection or are susceptible to interference effects.

  16. 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.

  17. A synaptic mechanism for retinal adaptation to luminance and contrast.

    PubMed

    Jarsky, Tim; Cembrowski, Mark; Logan, Stephen M; Kath, William L; Riecke, Hermann; Demb, Jonathan B; Singer, Joshua H

    2011-07-27

    The gain of signaling in primary sensory circuits is matched to the stimulus intensity by the process of adaptation. Retinal neural circuits adapt to visual scene statistics, including the mean (background adaptation) and the temporal variance (contrast adaptation) of the light stimulus. The intrinsic properties of retinal bipolar cells and synapses contribute to background and contrast adaptation, but it is unclear whether both forms of adaptation depend on the same cellular mechanisms. Studies of bipolar cell synapses identified synaptic mechanisms of gain control, but the relevance of these mechanisms to visual processing is uncertain because of the historical focus on fast, phasic transmission rather than the tonic transmission evoked by ambient light. Here, we studied use-dependent regulation of bipolar cell synaptic transmission evoked by small, ongoing modulations of membrane potential (V(M)) in the physiological range. We made paired whole-cell recordings from rod bipolar (RB) and AII amacrine cells in a mouse retinal slice preparation. Quasi-white noise voltage commands modulated RB V(M) and evoked EPSCs in the AII. We mimicked changes in background luminance or contrast, respectively, by depolarizing the V(M) or increasing its variance. A linear systems analysis of synaptic transmission showed that increasing either the mean or the variance of the presynaptic V(M) reduced gain. Further electrophysiological and computational analyses demonstrated that adaptation to mean potential resulted from both Ca channel inactivation and vesicle depletion, whereas adaptation to variance resulted from vesicle depletion alone. Thus, background and contrast adaptation apparently depend in part on a common synaptic mechanism.

  18. Adaptive Inverse Hyperbolic Tangent Algorithm for Dynamic Contrast Adjustment in Displaying Scenes

    NASA Astrophysics Data System (ADS)

    Yu, Cheng-Yi; Ouyang, Yen-Chieh; Wang, Chuin-Mu; Chang, Chein-I.

    2010-12-01

    Contrast has a great influence on the quality of an image in human visual perception. A poorly illuminated environment can significantly affect the contrast ratio, producing an unexpected image. This paper proposes an Adaptive Inverse Hyperbolic Tangent (AIHT) algorithm to improve the display quality and contrast of a scene. Because digital cameras must maintain the shadow in a middle range of luminance that includes a main object such as a face, a gamma function is generally used for this purpose. However, this function has a severe weakness in that it decreases highlight contrast. To mitigate this problem, contrast enhancement algorithms have been designed to adjust contrast to tune human visual perception. The proposed AIHT determines the contrast levels of an original image as well as parameter space for different contrast types so that not only the original histogram shape features can be preserved, but also the contrast can be enhanced effectively. Experimental results show that the proposed algorithm is capable of enhancing the global contrast of the original image adaptively while extruding the details of objects simultaneously.

  19. 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

  20. Do common mechanisms of adaptation mediate color discrimination and appearance? Contrast adaptation

    NASA Astrophysics Data System (ADS)

    Hillis, James M.; Brainard, David H.

    2007-08-01

    Are effects of background contrast on color appearance and sensitivity controlled by the same mechanism of adaptation? We examined the effects of background color contrast on color appearance and on color-difference sensitivity under well-matched conditions. We linked the data using Fechner's hypothesis that the rate of apparent stimulus change is proportional to sensitivity and examined a family of parametric models of adaptation. Our results show that both appearance and discrimination are consistent with the same mechanism of adaptation.

  1. Do common mechanisms of adaptation mediate color discrimination and appearance? Contrast adaptation.

    PubMed

    Hillis, James M; Brainard, David H

    2007-08-01

    Are effects of background contrast on color appearance and sensitivity controlled by the same mechanism of adaptation? We examined the effects of background color contrast on color appearance and on color-difference sensitivity under well-matched conditions. We linked the data using Fechner's hypothesis that the rate of apparent stimulus change is proportional to sensitivity and examined a family of parametric models of adaptation. Our results show that both appearance and discrimination are consistent with the same mechanism of adaptation.

  2. Clinical evaluation of vein contrast enhancement

    NASA Astrophysics Data System (ADS)

    Lovhoiden, Gunnar; Deshmukh, Harshal; Zeman, Herbert D.

    2002-05-01

    A clinical study is underway to compare an experimental infrared (IR) device, OnTarget OnTarget at LeBonheur Children's Medical Center, Methodist Healthcare, in Memphis, TN, while the adult study site is the clinical research center at Bowld Hospital, also in Memphis, TN. Early results on 35 pediatric and 25 adult subjects indicate that OnTarget years' experience in accessing veins in pediatric subjects, and that it could be very helpful to a phlebotomist with limited experience when accessing veins in both adult and pediatric subjects. The study uses monitor based OnTarget area of the patients anatomy enlarged and contrast enhanced on a LCD monitor. The phlebotomist can then compare the OnTarget or feel when examining a subject.

  3. Contrast-enhanced ultrasound in oncology

    PubMed Central

    Rasmussen, F.

    2011-01-01

    Abstract In patients with known malignant disease, 51% of liver lesions less than 1.5 cm turn out to be benign. Whether the probability of malignancy is high or low, further investigations are often necessary to definitely exclude malignancy. Contrast-enhanced ultrasonography has a prominent role in lesion characterization with a diagnostic accuracy comparable with computed tomography and magnetic resonance imaging. Anti-angiogenic treatment is common in most oncological institutions and the response evaluation is a new challenge with a research focus on the change in tumour vasculature and perfusion. In planning biopsies, CEUS can identify necrotic and viable areas of tumours and improve the diagnostic accuracy. PMID:22186152

  4. Individual and age-related variation in chromatic contrast adaptation

    PubMed Central

    Elliott, Sarah L.; Werner, John S.; Webster, Michael A.

    2012-01-01

    Precortical color channels are tuned primarily to the LvsM (stimulation of L and M cones varied, but S cone stimulation held constant) or SvsLM (stimulation of S cones varied, but L and M cone stimulation held constant) cone-opponent (cardinal) axes, but appear elaborated in the cortex to form higher-order mechanisms tuned to both cardinal and intermediate directions. One source of evidence for these higher-order mechanisms has been the selectivity of color contrast adaptation for noncardinal directions, yet the degree of this selectivity has varied widely across the small sample of observers tested in previous studies. This study explored the possible bases for this variation, and in particular tested whether it reflected age-related changes in the distribution or tuning of color mechanisms. Observers included 15 younger (18–22 years of age) and 15 older individuals (66–82), who adapted to temporal modulations along one of four chromatic axes (two cardinal and two intermediate axes) and then matched the hue and contrast of test stimuli lying along eight different directions in the equiluminant plane. All observers exhibited aftereffects that were selective for both the cardinal and intermediate directions, although selectivity was weaker for the intermediate axes. The degree of selectivity increased with the magnitude of adaptation for all axes, and thus adaptation strength alone may account for much of the variance in selectivity among observers. Older observers showed a stronger magnitude of adaptation thus, surprisingly, more conspicuous evidence for higher-order mechanisms. For both age groups the aftereffects were well predicted by response changes in chromatic channels with linear spectral sensitivities, and there was no evidence for weakened channel tuning with aging. The results suggest that higher-order mechanisms may become more exposed in observers or conditions in which the strength of adaptation is greater, and that both chromatic contrast

  5. Contrast-enhanced ultrasound of the spleen.

    PubMed

    Omar, Asha; Freeman, Simon

    2016-02-01

    Abnormalities in the spleen are less common than in most other abdominal organs. However, they will be regularly encountered by ultrasound practitioners, who carefully evaluate the spleen in their abdominal ultrasound studies. Conventional grey scale and Doppler ultrasound are frequently unable to characterise focal splenic abnormalities; even when clinical and laboratory information is added to the ultrasound findings, it is often not possible to make a definite diagnosis. Contrast-enhanced ultrasound (CEUS) is easy to perform, inexpensive, safe and will usually provide valuable additional information about splenic abnormalities, allowing a definitive or short differential diagnosis to be made. It also identifies those lesions that may require further imaging or biopsy, from those that can be safely dismissed or followed with interval ultrasound imaging. CEUS is also indicated in confirming the nature of suspected accessory splenic tissue and in selected patients with abdominal trauma. This article describes the CEUS examination technique, summarises the indications for CEUS and provides guidance on interpretation of the CEUS findings in splenic ultrasound.

  6. Measurements of contrast sensitivity by an adaptive optics visual simulator

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tatsuo; Ucikawa, Keiji

    2015-08-01

    We developed an adaptive optics visual simulator (AOVS) to study the relationship between the contrast sensitivity and higher-order wavefront aberrations of human eyes. A desired synthetic aberration was virtually generated on a subject eye by the AOVS, and red laser light was used to measure the aberrations. The contrast sensitivity was measured in a psychophysical experiment using visual stimulus patterns provided by a large-contrast-range imaging system, which included two liquid crystal displays illuminated by red light emitting diodes from the backside. The diameter of the pupil was set to 4 mm by an artificial aperture, and the retinal illuminance of the stimulus image was controlled to 10 Td. Experiments conducted with four normal subjects revealed that their contrast sensitivity to a high-spatial-frequency vertical sinusoidal grating pattern was lower in the presence of a horizontal coma aberration than in the presence of a vertical coma or no aberrations ( p < 0.02, Nagai method).

  7. Contrast enhancing solution for use in confocal microscopy

    DOEpatents

    Tannous, Zeina; Torres, Abel; Gonzalez, Salvador

    2006-10-31

    A method of optically detecting a tumor during surgery. The method includes imaging at least one test point defined on the tumor using a first optical imaging system to provide a first tumor image. The method further includes excising a first predetermined layer of the tumor for forming an in-vivo defect area. A predetermined contrast enhancing solution is disposed on the in-vivo defect area, which is adapted to interact with at least one cell anomaly, such as basal cell carcinoma, located on the in-vivo defect area for optically enhancing the cell anomaly. Thereafter the defect area can be optically imaged to provide a clear and bright representation of the cell anomaly to aid a surgeon while surgically removing the cell anomaly.

  8. Triple-energy contrast enhanced digital mammography

    NASA Astrophysics Data System (ADS)

    Puong, Sylvie; Milioni de Carvalho, Pablo; Muller, Serge

    2010-04-01

    With the injection of iodine, Contrast Enhanced Digital Mammography (CEDM) provides functional information about breast tumour angiogenesis that can potentially help in cancer diagnosis. In order to generate iodine images in which the gray level is proportional to the iodine thickness, temporal and dual-energy approaches have already been considered. The dual-energy method offers the advantage of less patient motion artifacts and better comfort during the exam. However, this approach requires knowledge of the breast thickness at each pixel. Generally, as compression is applied, the breast thickness at each pixel is taken as the compression thickness. Nevertheless, in the breast border region, this assumption is not correct anymore and this causes inaccuracies in the iodine image. Triple-Energy CEDM could overcome these limitations by providing supplemental information in the form of a third image acquired with a different spectrum than the other two. This precludes the need of a priori knowledge of the breast thickness. Moreover, with Triple-Energy CEDM, breast thickness and glandularity maps could potentially be derived. In this study, we first focused on the method to recombine the three images in order to generate the iodine image, analyzing the performance of either quadratic, cubic or conic recombination functions. Then, we studied the optimal acquisition spectra in order to maximize the iodine SDNR in the recombined image for a given target total glandular dose. The concept of Triple-Energy CEDM was validated on simulated textured images and poly-energetic images acquired with a conventional X-ray mammography tube.

  9. Adaptive Processes in Thalamus and Cortex Revealed by Silencing of Primary Visual Cortex during Contrast Adaptation.

    PubMed

    King, Jillian L; Lowe, Matthew P; Stover, Kurt R; Wong, Aimee A; Crowder, Nathan A

    2016-05-23

    Visual adaptation illusions indicate that our perception is influenced not only by the current stimulus but also by what we have seen in the recent past. Adaptation to stimulus contrast (the relative luminance created by edges or contours in a scene) induces the perception of the stimulus fading away and increases the contrast detection threshold in psychophysical tests [1, 2]. Neural correlates of contrast adaptation have been described throughout the visual system including the retina [3], dorsal lateral geniculate nucleus (dLGN) [4, 5], primary visual cortex (V1) [6], and parietal cortex [7]. The apparent ubiquity of adaptation at all stages raises the question of how this process cascades across brain regions [8]. Focusing on V1, adaptation could be inherited from pre-cortical stages, arise from synaptic depression at the thalamo-cortical synapse [9], or develop locally, but what is the weighting of these contributions? Because contrast adaptation in mouse V1 is similar to classical animal models [10, 11], we took advantage of the optogenetic tools available in mice to disentangle the processes contributing to adaptation in V1. We disrupted cortical adaptation by optogenetically silencing V1 and found that adaptation measured in V1 now resembled that observed in dLGN. Thus, the majority of adaptation seen in V1 neurons arises through local activity-dependent processes, with smaller contributions from dLGN inheritance and synaptic depression at the thalamo-cortical synapse. Furthermore, modeling indicates that divisive scaling of the weakly adapted dLGN input can predict some of the emerging features of V1 adaptation.

  10. Contrast enhanced spectroscopic optical coherence tomography

    NASA Technical Reports Server (NTRS)

    Boppart, Stephen A. (Inventor); Xu, Chenyang (Inventor)

    2010-01-01

    A method of forming an image of a sample includes performing SOCT on a sample. The sample may include a contrast agent, which may include an absorbing agent and/or a scattering agent. A method of forming an image of tissue may include selecting a contrast agent, delivering the contrast agent to the tissue, acquiring SOCT data from the tissue, and converting the SOCT data into an image. The contributions to the SOCT data of an absorbing agent and a scattering agent in a sample may be quantified separately.

  11. Limitations of contrast enhancement for infrared target identification

    NASA Astrophysics Data System (ADS)

    Du Bosq, Todd W.; Fanning, Jonathan D.

    2009-05-01

    Contrast enhancement and dynamic range compression are currently being used to improve the performance of infrared imagers by increasing the contrast between the target and the scene content. Automatic contrast enhancement techniques do not always achieve this improvement. In some cases, the contrast can increase to a level of target saturation. This paper assesses the range-performance effects of contrast enhancement for target identification as a function of image saturation. Human perception experiments were performed to determine field performance using contrast enhancement on the U.S. Army RDECOM CERDEC NVESD standard military eight target set using an un-cooled LWIR camera. The experiments compare the identification performance of observers viewing contrast enhancement processed images at various levels of saturation. Contrast enhancement is modeled in the U.S. Army thermal target acquisition model (NVThermIP) by changing the scene contrast temperature. The model predicts improved performance based on any improved target contrast, regardless of specific feature saturation or enhancement. The measured results follow the predicted performance based on the target task difficulty metric used in NVThermIP for the non-saturated cases. The saturated images reduce the information contained in the target and performance suffers. The model treats the contrast of the target as uniform over spatial frequency. As the contrast is enhanced, the model assumes that the contrast is enhanced uniformly over the spatial frequencies. After saturation, the spatial cues that differentiate one tank from another are located in a limited band of spatial frequencies. A frequency dependent treatment of target contrast is needed to predict performance of over-processed images.

  12. 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.

  13. 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

  14. Modeling the effects of contrast enhancement on target acquisition performance

    NASA Astrophysics Data System (ADS)

    Du Bosq, Todd W.; Fanning, Jonathan D.

    2008-04-01

    Contrast enhancement and dynamic range compression are currently being used to improve the performance of infrared imagers by increasing the contrast between the target and the scene content, by better utilizing the available gray levels either globally or locally. This paper assesses the range-performance effects of various contrast enhancement algorithms for target identification with well contrasted vehicles. Human perception experiments were performed to determine field performance using contrast enhancement on the U.S. Army RDECOM CERDEC NVESD standard military eight target set using an un-cooled LWIR camera. The experiments compare the identification performance of observers viewing linearly scaled images and various contrast enhancement processed images. Contrast enhancement is modeled in the US Army thermal target acquisition model (NVThermIP) by changing the scene contrast temperature. The model predicts improved performance based on any improved target contrast, regardless of feature saturation or enhancement. To account for the equivalent blur associated with each contrast enhancement algorithm, an additional effective MTF was calculated and added to the model. The measured results are compared with the predicted performance based on the target task difficulty metric used in NVThermIP.

  15. Field strength and dose dependence of contrast enhancement by gadolinium-based MR contrast agents.

    PubMed

    Rinck, P A; Muller, R N

    1999-01-01

    The relaxivities r1 and r2 of magnetic resonance contrast agents and the T1 relaxation time values of tissues are strongly field dependent. We present quantitative data and simulations of different gadolinium-based extracellular fluid contrast agents and the modulation of their contrast enhancement by the magnetic field to be able to answer the following questions: How are the dose and field dependences of their contrast enhancement? Is there an interrelationship between dose and field dependence? Should one increase or decrease doses at specific fields? Nuclear magnetic relaxation dispersion data were acquired for the following contrast agents: gadopentetate dimeglumine, gadoterate meglumine, gadodiamide injection, and gadoteridol injection, as well as for several normal and pathological human tissue samples. The magnetic field range stretched from 0.0002 to 4.7 T, including the entire clinical imaging range. The data acquired were then fitted with the appropriate theoretical models. The combination of the diamagnetic relaxation rates (R1 = 1/T1 and R2 = 1/T2) of tissues with the respective paramagnetic contributions of the contrast agents allowed the prediction of image contrast at any magnetic field. The results revealed a nearly identical field and dose-dependent increase of contrast enhancement induced by these contrast agents within a certain dose range. The target tissue concentration (TTC) was an important though nonlinear factor for enhancement. The currently recommended dose of 0.1 mmol/kg body weight seems to be a compromise close to the lower limits of diagnostically sufficient contrast enhancement for clinical imaging at all field strengths. At low field contrast enhancement might be insufficient. Adjustment of dose or concentration, or a new class of contrast agents with optimized relaxivity, would be a valuable contribution to a better diagnostic yield of contrast enhancement at all fields.

  16. A comparative study on preprocessing techniques in diabetic retinopathy retinal images: illumination correction and contrast enhancement.

    PubMed

    Rasta, Seyed Hossein; Partovi, Mahsa Eisazadeh; Seyedarabi, Hadi; Javadzadeh, Alireza

    2015-01-01

    To investigate the effect of preprocessing techniques including contrast enhancement and illumination correction on retinal image quality, a comparative study was carried out. We studied and implemented a few illumination correction and contrast enhancement techniques on color retinal images to find out the best technique for optimum image enhancement. To compare and choose the best illumination correction technique we analyzed the corrected red and green components of color retinal images statistically and visually. The two contrast enhancement techniques were analyzed using a vessel segmentation algorithm by calculating the sensitivity and specificity. The statistical evaluation of the illumination correction techniques were carried out by calculating the coefficients of variation. The dividing method using the median filter to estimate background illumination showed the lowest Coefficients of variations in the red component. The quotient and homomorphic filtering methods after the dividing method presented good results based on their low Coefficients of variations. The contrast limited adaptive histogram equalization increased the sensitivity of the vessel segmentation algorithm up to 5% in the same amount of accuracy. The contrast limited adaptive histogram equalization technique has a higher sensitivity than the polynomial transformation operator as a contrast enhancement technique for vessel segmentation. Three techniques including the dividing method using the median filter to estimate background, quotient based and homomorphic filtering were found as the effective illumination correction techniques based on a statistical evaluation. Applying the local contrast enhancement technique, such as CLAHE, for fundus images presented good potentials in enhancing the vasculature segmentation.

  17. Determination of contrast media administration to achieve a targeted contrast enhancement in CT

    NASA Astrophysics Data System (ADS)

    Sahbaee, Pooyan; Li, Yuan; Segars, Paul; Marin, Daniele; Nelson, Rendon; Samei, Ehsan

    2015-03-01

    Contrast enhancement is a key component of CT imaging and offer opportunities for optimization. The design and optimization of new techniques however requires orchestration with the scan parameters and further a methodology to relate contrast enhancement and injection function. In this study, we used such a methodology to develop a method, analytical inverse method, to predict the required injection function to achieve a desired contrast enhancement in a given organ by incorporation of a physiologically based compartmental model. The method was evaluated across 32 different target contrast enhancement functions for aorta, kidney, stomach, small intestine, and liver. The results exhibited that the analytical inverse method offers accurate performance with error in the range of 10% deviation between the predicted and desired organ enhancement curves. However, this method is incapable of predicting the injection function based on the liver enhancement. The findings of this study can be useful in optimizing contrast medium injection function as well as the scan timing to provide more consistency in the way that the contrast enhanced CT examinations are performed. To our knowledge, this work is one of the first attempts to predict the contrast material injection function for a desired organ enhancement curve.

  18. High-contrast, adaptive-optics simulations for HARMONI

    NASA Astrophysics Data System (ADS)

    Gladysz, Szymon; Thatte, Niranjan A.; Salter, Graeme; Clarke, Fraser; Tecza, Matthias; Jolissaint, Laurent; Galle, Roberto Baena

    2011-09-01

    HARMONI is a proposed visible and near-infrared integral field spectrograph for the European Extremely Large Telescope. We are exploring the potential of using HARMONI for high-contrast science, e.g. observations of exoplanets. Although HARMONI is not fed by extreme adaptive optics we show that substantial contrasts can be achieved by combining single-conjugate AO with coronagraphy and post-processing of the hyperspectral data cube using spectral deconvolution. HARMONI will be well suited for follow-up spectroscopy of planets detected by 8m class instruments, emphasizing their characterisation. We implement models of telescope aberrations: due to wind buffeting on M1, due to windshake on M2, due to rolled segment edges, as well as the ones resulting from M1 phasing and individual segment warping affected by thermal and gravity effects. Additionally, we investigate the impact of post-AO differential aberrations. We also look at possible improvements to spectral deconvolution which is our method of choice for data post-processing. Finally, we make predictions of achievable contrast which translates to the ability to characterise various types of exoplanets in detail.

  19. Multi-scale image enhancement using a second derivative-like measure of contrast

    NASA Astrophysics Data System (ADS)

    Nercessian, Shahan; Agaian, Sos S.; Panetta, Karen A.

    2012-03-01

    Image enhancement algorithms attempt to improve the visual quality of images for human or machine perception. Most direct multi-scale image enhancement methods are based on enhancing either absolute intensity changes or the Weber contrast at each scale, and have the advantage that the visual contrast is enhanced in a controlled manner. However, the human visual system is not adapted to absolute intensity changes, while the Weber contrast is unstable for small values of background luminance and potentially unsuitable for complex image patterns. The Michelson contrast measure is a bounded measure of contrast, but its expression does not allow a straightforward direct image enhancement formulation. Recently, a second derivative-like measure of contrast has been used to assess the performance of image enhancement algorithms. This measure is a Michelson-like contrast measure for which a direct image enhancement algorithm can be formulated. Accordingly, we propose a new direct multi-scale image enhancement algorithm based on the SDME in this paper. Experimental results illustrate the potential benefits of the proposed algorithm.

  20. 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.

  1. in vivo laser speckle imaging by adaptive contrast computation for microvasculature assessment

    NASA Astrophysics Data System (ADS)

    Basak, Kausik; Dey, Goutam; Mahadevappa, Manjunatha; Mandal, Mahitosh; Dutta, Pranab Kumar

    2014-11-01

    Interference of light backscattered from a diffused surface leads to speckle formation in laser speckle imaging. These time integrated speckle patterns can be statistically analyzed to study the flow profile of moving scatterers. Simple speckle contrast analysis techniques have limited ability to distinguish thin structures due to presence of corrupting speckles. This paper presents a high resolution imaging technique by adaptive computation of contrast for laser speckle contrast analysis (adLASCA). Speckle images of retinal microvasculature in mice model are acquired during normal and reduced blood flow conditions. Initially, the speckle images are registered to compensate for movements, associated with heart beating and respiration. Adaptive computation is performed using local image statistics, estimated within a spatially moving window over successive time frames. Experimental evidence suggests that adLASCA outperforms other contrast analysis methods, substantiating significant improvement in contrast resolution. Fine vessels can be distinguished more efficiently with reduced fluctuations in contrast level. Quantitative performance of adLASCA is evaluated by computing standard deviation, corresponding to speckle fluctuations due to unwanted speckles. There is a significant reduction in standard deviation compared to other methods. Therefore, adLASCA can be used for enhancing microvasculature in high resolution perfusion imaging with reduced effect of corrupting speckles for effective assessment.

  2. 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

  3. Dynamic contrast-enhanced MRI of ocular melanoma.

    PubMed

    Jiang, Xuyuan; Asbach, Patrick; Willerding, Gregor; Dulce, Miriam; Xu, Ke; Taupitz, Matthias; Hamm, Bernd; Erb-Eigner, Katharina

    2015-04-01

    Dynamic contrast-enhanced MRI is used for the assessment of microvasculature in several tumours. We aimed to assess the contrast signal enhancement characteristics of ocular melanoma. Forty patients with ocular melanoma were prospectively investigated with ocular MRI including dynamic contrast-enhanced sequences over a 13-month period. A region-of-interest analysis of the images was carried out to calculate signal enhancement characteristics after a contrast injection. Clinical follow-up data such as extraocular spread and development of liver metastasis were compared with the signal enhancement characteristics of the ocular melanoma. In 39 patients (98%), the ocular melanomas showed an early strong signal enhancement after contrast injection, resulting in a mean time of maximum enhancement of 49 s. Clinical follow-up was available in 28 patients (70%) and indicated that the peak signal intensity was significantly increased (P=0.039) in patients who developed extraocular spread or liver metastasis at a later stage. Ocular melanoma shows signal enhancement characteristics of hypervascular neoplasms. This study provides baseline curve pattern data that may be useful for assessing changes in vascularity, for example during therapy response. Furthermore, the study showed that a strong signal enhancement of the ocular melanoma might be linked to a less favourable prognosis.

  4. On-off selectivity and asymmetry in apparent contrast: An adaptation study.

    PubMed

    Sato, Hiromi; Motoyoshi, Isamu; Sato, Takao

    2016-01-01

    Using textures composed of sparse bright/dark elements that can activate either on or off sensors selectively, Sato, Motoyoshi, and Sato (2012) reported simultaneous contrast-contrast effects tuned for contrast polarity. As with contrast-contrast effects, prolonged viewing of high-contrast stimuli reduces the perceived contrast of a subsequently presented stimulus. The present study examined whether contrast aftereffects are also selective for luminance polarity using texture patterns composed of sparse bright/dark elements. Results revealed that contrast aftereffects are selective for luminance polarity (polarity selectivity) but that adaptation aftereffects occur asymmetrically depending on the polarity of the adapter (polarity asymmetry). Polarity selectivity and asymmetry in adaptation aftereffects are reduced but not completely diminished if adapter and test stimuli are presented to separate eyes (dichoptically). Our results support the idea that suprathreshold contrast perception and its adaptational shifts are jointly determined by responses between monocular and binocular units.

  5. 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.

  6. Detection for processing history of seam insertion and contrast enhancement

    NASA Astrophysics Data System (ADS)

    Li, Jianwei; Zhao, Yao; Ni, Rongrong

    2014-11-01

    With the development of manipulations techniques of digital images, digital image forensic technology is becoming more and more necessary. However, the determination of processing history of multi-operation is still a challenge problem. In this paper, we improve the traditional seam insertion algorithm, and propose corresponding detection method. Then an algorithm that focuses on detecting the processing history of seam insertion and contrast enhancement is proposed, which can be widely used in practical image forgery. Based on comprehensive analysis, we have discovered the inherent relationship between seam insertion and contrast enhancement. Different orders of processing make different impacts on images. By using the newly proposed algorithm, both contrast enhancement followed by seam insertion and seam insertion followed by contrast enhancement can be detected correctly. Plenty of experiments have been implemented to prove the accuracy.

  7. Visual Contrast Enhancement Algorithm Based on Histogram Equalization

    PubMed Central

    Ting, Chih-Chung; Wu, Bing-Fei; Chung, Meng-Liang; Chiu, Chung-Cheng; Wu, Ya-Ching

    2015-01-01

    Image enhancement techniques primarily improve the contrast of an image to lend it a better appearance. One of the popular enhancement methods is histogram equalization (HE) because of its simplicity and effectiveness. However, it is rarely applied to consumer electronics products because it can cause excessive contrast enhancement and feature loss problems. These problems make the images processed by HE look unnatural and introduce unwanted artifacts in them. In this study, a visual contrast enhancement algorithm (VCEA) based on HE is proposed. VCEA considers the requirements of the human visual perception in order to address the drawbacks of HE. It effectively solves the excessive contrast enhancement problem by adjusting the spaces between two adjacent gray values of the HE histogram. In addition, VCEA reduces the effects of the feature loss problem by using the obtained spaces. Furthermore, VCEA enhances the detailed textures of an image to generate an enhanced image with better visual quality. Experimental results show that images obtained by applying VCEA have higher contrast and are more suited to human visual perception than those processed by HE and other HE-based methods. PMID:26184219

  8. Quantitative flow phantom for contrast-enhanced breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Nock, Melissa L.; Kempston, Michael P.; Mainprize, James G.; Yaffe, Martin J.

    2007-03-01

    The use of contrast agents can help to overcome a lack of intrinsic radiographic contrast between malignant and benign breast tissue by taking advantage of the properties of tumour angiogenesis. Studies of contrast-enhanced mammography have demonstrated increased lesion conspicuity and have shown that this technique provides information on contrast uptake kinetics. It has been suggested that malignant and benign lesions can be differentiated in part by their uptake kinetics, so this additional data may lead to more accurate diagnoses. Tomosynthesis is a 3D x-ray imaging technique that permits lesion depth localization and increased conspicuity in comparison with 2D x-ray projection techniques. This modality, used in combination with contrast agents, promises to be a sensitive method of breast cancer detection. To develop the technique of contrast-enhanced breast tomosynthesis, a dynamic flow phantom has been constructed to provide the same types of imaging challenges anticipated in the clinical setting. These challenges include a low-contrast tumour space, relevant temporal contrast agent uptake and washout profiles, and a need for quantitative analysis of enhancement levels. The design of a flow phantom will be presented that includes a dynamic tumour space, a background that masks the tumour space in images without contrast enhancement, and flow characteristics that simulate tumour contrast agent uptake and washout kinetics. The system is calibrated to relate signal to concentration of the contrast agent using a well plate filled with iodinated water. Iodine detectability in the flow phantom is evaluated in terms of the signal-difference-to-noise ratio for various tomosynthesis image acquisition parameters including number of acquired angular views, angular extent, and reconstruction voxel size.

  9. Regional contrast enhancement and data compression for digital mammographic images

    NASA Astrophysics Data System (ADS)

    Chen, Ji; Flynn, Michael J.; Rebner, Murray

    1993-07-01

    The wide dynamic range of mammograms poses problems for displaying images on an electronic monitor and printing images through a laser printer. In addition, digital mammograms require a large amount of storage and network transmission bandwidth. We applied contrast enhancement and data compression to the segmented images to solve these problems. Using both image intensity and Gaussian filtered images, we separated the original image into three regions: the interior region, the skinline transition region, and the exterior region. In the transition region, unsharp masking process was applied and an adaptive density shift was used to simulate the process of highlighting with a spot light. The exterior region was set to a high density to reduce glare. The interior and skinline regions are the diagnostically informative areas that need to be preserved. Visually lossless coding was done for the interior by the wavelet or subband transform coding method. This was used because there are no block artifacts and a lowpass filtered image is generated by the transform. The exterior region can be represented by a bit-plane image containing only the labeling information or represented by the lower resolution transform coefficients. Therefore, by applying filters of different scales, we can accomplish region segmentation and data compression.

  10. Dynamic contrast-enhanced ultrasound for quantification of tissue perfusion.

    PubMed

    Fröhlich, Eckhart; Muller, Reinhold; Cui, Xin-Wu; Schreiber-Dietrich, Dagmar; Dietrich, Christoph F

    2015-02-01

    Dynamic contrast-enhanced ultrasound (US) imaging, a technique that uses microbubble contrast agents with diagnostic US, has recently been technically summarized and reviewed by a European Federation of Societies for Ultrasound in Medicine and Biology position paper. However, the practical applications of this imaging technique were not included. This article reviews and discusses the published literature on the clinical use of dynamic contrast-enhanced US. This review finds that dynamic contrast-enhanced US imaging is the most sensitive cross-sectional real-time method for measuring the perfusion of parenchymatous organs noninvasively. It can measure parenchymal perfusion and therefore can differentiate between benign and malignant tumors. The most important routine clinical role of dynamic contrast-enhanced US is the prediction of tumor responses to chemotherapy within a very short time, shorter than using Response Evaluation Criteria in Solid Tumors criteria. Other applications found include quantifying the hepatic transit time, diabetic kidneys, transplant grafts, and Crohn disease. In addition, the problems involved in using dynamic contrast-enhanced US are discussed.

  11. 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.

  12. 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.

  13. Automatic contrast enhancement using ensemble empirical mode decomposition.

    PubMed

    Lin, Shang-Ching; Li, Pai-Chi

    2011-12-01

    Ultrasound nonlinear contrast imaging using microbubble-based contrast agents has been widely investigated. However, the degree of contrast enhancement is often limited by overlap between the spectra of the tissue and microbubble nonlinear responses, which makes it difficult to separate them. The use of ensemble empirical mode decomposition (EEMD) in the Hilbert-Huang transform (HHT) was previously explored with the aim of alleviating this problem. The HHT is designed for analyzing nonlinear and nonstationary data, whereas EEMD is a method associated with the HHT that allows decomposition of data into a finite number of intrinsic mode functions (IMFs). It was found that the contrast can be effectively improved in certain IMFs, but manual selection of appropriate IMFs is still required. This prompted the present study to test the hypothesis that the contrast can be enhanced without requiring manual selection by summing appropriately weighted IMFs and demodulating the signal at appropriate frequencies. That is, a data-driven mechanism for determining weights and demodulation frequencies was derived and tested. Phantom results show that an overall contrast enhancement of up to 12.5 dB can be achieved. A fused-image representation that simultaneously displays the conventional B-mode image and the new contrast-mode image is also presented.

  14. Contrast-Enhanced Anatomic Imaging as Compared to Contrast-Enhanced Tissue Characterization for Detection of Left Ventricular Thrombus

    PubMed Central

    Weinsaft, Jonathan W.; Kim, Raymond J.; Ross, Michael; Krauser, Daniel; Manoushagian, Shant; LaBounty, Troy M.; Cham, Matthew D.; Min, James K.; Healy, Kirsten; Wang, Yi; Parker, Michele; Roman, Mary J.; Devereux, Richard B.

    2016-01-01

    Objectives To compare contrast-enhanced anatomic imaging to contrast-enhanced tissue characterization (DE-CMR) for left ventricular (LV) thrombus detection. Background Contrast echocardiography (echo) detects LV thrombus based on anatomic appearance whereas delayed-enhancement cardiac magnetic resonance (DE-CMR) imaging detects thrombus based on tissue characteristics. DE-CMR has been validated as an accurate technique for thrombus but its utility compared to contrast echo is unknown. Methods Multimodality imaging was performed in 121 patients at high-risk for thrombus due to myocardial infarction or heart failure. Imaging included three anatomic imaging techniques for thrombus detection (contrast echo, non-contrast echo, cine-CMR) and a reference of DE-CMR tissue characterization. LV structural parameters were quantified to identify markers for thrombus and predictors of additive utility of contrast-enhanced thrombus imaging. Results 24 patients had thrombus by DE-CMR. Patients with thrombus had larger infarcts (by DE-CMR), more aneurysms and lower LVEF (by CMR and echo) than those without thrombus. Contrast echo nearly doubled sensitivity (61% vs. 33%, p<0.05) and yielded improved accuracy (92% vs. 82%, p<0.01) vs. non-contrast echo. Patients who derived incremental diagnostic utility from DE-CMR had lower LVEF vs. those in whom non-contrast echo alone accurately assessed thrombus (35±9% vs. 42±14%, p<0.01), with a similar trend for patients that derived incremental benefit from contrast echo (p=0.08). Contrast echo and cine-CMR closely agreed on the diagnosis of thrombus (kappa=0.79, p<0.001). Thrombus prevalence was lower by contrast echo than DE-CMR (p<0.05). Thrombus detected by DE-CMR but not by contrast echo was more likely to be mural in shape or, when apical, small in volume (p<0.05). Conclusions Echo contrast in high-risk patients markedly improves detection of LV thrombus, but does not detect a substantial number of thrombi identified by DE-CMR tissue

  15. Evaluation of renal masses with contrast-enhanced ultrasound.

    PubMed

    Houtzager, S; Wijkstra, H; de la Rosette, J J M C H; Laguna, M P

    2013-04-01

    The clinical need for characterising small renal masses (SRMs) is increasing due to their rising incidental detection. This increase is especially seen in younger and older generations and concerns mainly SRMs. Diagnostics is mainly made by contrast-enhanced CT or MRI. However, these imaging methods fail to accurately distinguishing benign from malignant SRMs. Other disadvantages of CT or MRI are high costs, the use of ionizing radiation, nephrotoxicity induced by iodine contrast agents or nephrogenic systemic fibrosis (NSF) induced by gadolinium contrast agents. Contrast-enhanced ultrasound (CEUS) is based on ultrasonography and microbubbles to real-time visualize the renal blood flow without the use of nephrotoxic agents or ionizing radiation. This comprehensive review evaluates the capabilities of CEUS in the diagnostics of benign (angiomyolipomas, cysts, oncocytomas, pseudotumors) and malignant masses (renal cell carcinomas), and focuses on possible future treatment.

  16. 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.

  17. An Analysis and Method for Contrast Enhancement Turbulence Mitigation.

    PubMed

    Gibson, Kristofor; Nguyen, Truong

    2014-06-03

    A common problem for imaging in the atmosphere is fog and atmospheric turbulence. Over the years many researchers have provided insight into the physics of either the fog or turbulence but not both. Most recently, researchers have proposed methods to remove fog in images fast enough for real-time processing. Additionally, methods have been proposed by other researchers that address the atmospheric turbulence problem. In this article, we provide an analysis that incorporates both physics models: fog and turbulence. We observe how contrast enhancements (fog removal) can affect image alignment and image averaging. We present in this article a new joint contrast enhancement and turbulence mitigation method (CETM) that utilizes estimations from the contrast enhancement algorithm to improve the turbulence removal algorithm. We provide a new turbulent mitigation object metric that measures temporal consistency. Finally, we design the CETM to be efficient such that it can operate in fractions of a second for near real-time applications.

  18. An analysis and method for contrast enhancement turbulence mitigation.

    PubMed

    Gibson, Kristofor B; Nguyen, Truong Q

    2014-07-01

    A common problem for imaging in the atmosphere is fog and atmospheric turbulence. Over the years, many researchers have provided insight into the physics of either the fog or turbulence but not both. Most recently, researchers have proposed methods to remove fog in images fast enough for real-time processing. Additionally, methods have been proposed by other researchers that address the atmospheric turbulence problem. In this paper, we provide an analysis that incorporates both physics models: 1) fog and 2) turbulence. We observe how contrast enhancements (fog removal) can affect image alignment and image averaging. We present in this paper, a new joint contrast enhancement and turbulence mitigation (CETM) method that utilizes estimations from the contrast enhancement algorithm to improve the turbulence removal algorithm. We provide a new turbulent mitigation object metric that measures temporal consistency. Finally, we design the CETM to be efficient such that it can operate in fractions of a second for near real-time applications.

  19. Contrast enhanced computerized tomography measurement of vascular blood flow

    NASA Astrophysics Data System (ADS)

    Sixou, B.; Boissel, L.; Sigovan, M.

    2016-10-01

    In this work, we study the measurement of blood velocity with contrast enhanced computed tomography. The transport equation is used as a constraint to obtain stable solutions. The inverse problem is formulated as an optimal control problem. The density of the contrast agent is reconstructed together with the flow field. The inversion scheme is tested on a simple phantom. The reconstruction of the velocity is improved but the convergence of the method is slow.

  20. Patterns of contrast enhancement in the brain and meninges.

    PubMed

    Smirniotopoulos, James G; Murphy, Frances M; Rushing, Elizabeth J; Rees, John H; Schroeder, Jason W

    2007-01-01

    Contrast material enhancement for cross-sectional imaging has been used since the mid 1970s for computed tomography and the mid 1980s for magnetic resonance imaging. Knowledge of the patterns and mechanisms of contrast enhancement facilitate radiologic differential diagnosis. Brain and spinal cord enhancement is related to both intravascular and extravascular contrast material. Extraaxial enhancing lesions include primary neoplasms (meningioma), granulomatous disease (sarcoid), and metastases (which often manifest as mass lesions). Linear pachymeningeal (dura-arachnoid) enhancement occurs after surgery and with spontaneous intracranial hypotension. Leptomeningeal (pia-arachnoid) enhancement is present in meningitis and meningoencephalitis. Superficial gyral enhancement is seen after reperfusion in cerebral ischemia, during the healing phase of cerebral infarction, and with encephalitis. Nodular subcortical lesions are typical for hematogenous dissemination and may be neoplastic (metastases) or infectious (septic emboli). Deeper lesions may form rings or affect the ventricular margins. Ring enhancement that is smooth and thin is typical of an organizing abscess, whereas thick irregular rings suggest a necrotic neoplasm. Some low-grade neoplasms are "fluid-secreting," and they may form heterogeneously enhancing lesions with an incomplete ring sign as well as the classic "cyst-with-nodule" morphology. Demyelinating lesions, including both classic multiple sclerosis and tumefactive demyelination, may also create an open ring or incomplete ring sign. Thick and irregular periventricular enhancement is typical for primary central nervous system lymphoma. Thin enhancement of the ventricular margin occurs with infectious ependymitis. Understanding the classic patterns of lesion enhancement--and the radiologic-pathologic mechanisms that produce them--can improve image assessment and differential diagnosis.

  1. Immobilized Contrast Enhanced (ICE) MRI: Gadolinium-based long-term MR Contrast Enhancement of the Vein Graft Vessel Wall*

    PubMed Central

    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.

    2010-01-01

    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 post-surgical 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 Gd-DTPA 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 3T, and its long-term stability is demonstrated during a 4-month incubation period. PMID:20859994

  2. Contrast enhanced endoscopic ultrasound: More than just a fancy Doppler.

    PubMed

    Mohamed, Rachid M; Yan, Brian M

    2010-07-16

    Contrast enhanced endoscopic ultrasound (CEUS) is a new modality that takes advantage of vascular structure and blood flow to distinguish different clinical entities. Contrast agents are microbubbles that oscillate when exposed to ultrasonographic waves resulting in characteristic acoustic signals that are then converted to colour images. This permits exquisite imaging of macro- and microvasculature, providing information to help delineate malignant from non-malignant processes. The use of CEUS may significantly increase the sensitivity and specificity over conventional endoscopic ultrasound. Currently available contrast agents are safe, with infrequent adverse effects. This review summarizes the theory and technique behind CEUS and the current and future clinical applications.

  3. Dual energy contrast enhanced breast imaging optimization using contrast to noise ratio

    NASA Astrophysics Data System (ADS)

    Arvanitis, C. D.; Royle, G.; Speller, R.

    2007-03-01

    The properties of dual energy contrast enhanced breast imaging have been analyzed by imaging a 4 cm breast equivalent phantom consisting of adipose and glandular equivalent plastics. This phantom had superimposed another thin plastic which incorporated a 2 mm deep cylinder filled with iodinated contrast media. The iodine projected thicknesses used for this study was 3 mg/cm2. Low and high energy spectra that straddle the iodine K-edge were used. Critical parameters such as the energy spectra and exposure are discussed, along with post processing by means of nonlinear energy dependent function. The dual energy image was evaluated using the relative contrast to noise ratio of a 2.5 mm x 2.5 mm region of the image at the different iodine concentrations incorporating different breast composition with respect to the noniodinated areas. Optimum results were achieved when the low and high-energy images were used in such a way that relative contrast to noise ratio of the iodine with respect to the background tissue was maximum. A figure of merit suggests that higher noise levels can be tolerated at the benefit of lower exposure. Contrast media kinetics of a phantom incorporating a water flow of 20.4 ml/min through the plastic cylinder suggests that time domain imaging could be performed with this approach. The results suggest that optimization of dual energy contrast enhanced mammography has the potential to lead to the development of perfusion digital mammography.

  4. 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.

  5. 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.

  6. Resolution enhancement phase-contrast imaging by microsphere digital holography

    NASA Astrophysics Data System (ADS)

    Wang, Yunxin; Guo, Sha; Wang, Dayong; Lin, Qiaowen; Rong, Lu; Zhao, Jie

    2016-05-01

    Microsphere has shown the superiority of super-resolution imaging in the traditional 2D intensity microscope. Here a microsphere digital holography approach is presented to realize the resolution enhancement phase-contrast imaging. The system is designed by combining the microsphere with the image-plane digital holography. A microsphere very close to the object can increase the resolution by transforming the object wave from the higher frequency to the lower one. The resolution enhancement amplitude and phase images can be retrieved from a single hologram. The experiments are carried on the 1D and 2D gratings, and the results demonstrate that the observed resolution has been improved, meanwhile, the phase-contrast image is obtained. The proposed method can improve the transverse resolution in all directions based on a single exposure. Furthermore, this system has extended the application of the microsphere from the conventional 2D microscopic imaging to 3D phase-contrast microscopic imaging.

  7. Contrast Enhanced MRI in the Diagnosis of HCC

    PubMed Central

    Niendorf, Eric; Spilseth, Benjamin; Wang, Xiao; Taylor, Andrew

    2015-01-01

    Hepatocellular carcinoma (HCC) is the 6th most common cancer worldwide. Imaging plays a critical role in HCC screening and diagnosis. Initial screening of patients at risk for HCC is performed with ultrasound. Confirmation of HCC can then be obtained by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), due to the relatively high specificity of both techniques. This article will focus on reviewing MRI techniques for imaging HCC, felt by many to be the exam of choice for HCC diagnosis. MRI relies heavily upon the use of gadolinium-based contrast agents and while primarily extracellular gadolinium-based contrast agents are used, there is an emerging role of hepatobiliary contrast agents in HCC imaging. The use of other non-contrast enhanced MRI techniques for assessing HCC will also be discussed and these MRI strategies will be reviewed in the context of the pathophysiology of HCC to help understand the MR imaging appearance of HCC. PMID:26854161

  8. Adaptive processing for enhanced target acquisition

    NASA Astrophysics Data System (ADS)

    Page, Scott F.; Smith, Moira I.; Hickman, Duncan; Bernhardt, Mark; Oxford, William; Watson, Norman; Beath, F.

    2009-05-01

    Conventional air-to-ground target acquisition processes treat the image stream in isolation from external data sources. This ignores information that may be available through modern mission management systems which could be fused into the detection process in order to provide enhanced performance. By way of an example relating to target detection, this paper explores the use of a-priori knowledge and other sensor information in an adaptive architecture with the aim of enhancing performance in decision making. The approach taken here is to use knowledge of target size, terrain elevation, sensor geometry, solar geometry and atmospheric conditions to characterise the expected spatial and radiometric characteristics of a target in terms of probability density functions. An important consideration in the construction of the target probability density functions are the known errors in the a-priori knowledge. Potential targets are identified in the imagery and their spatial and expected radiometric characteristics are used to compute the target likelihood. The adaptive architecture is evaluated alongside a conventional non-adaptive algorithm using synthetic imagery representative of an air-to-ground target acquisition scenario. Lastly, future enhancements to the adaptive scheme are discussed as well as strategies for managing poor quality or absent a-priori information.

  9. A Contrast Enhancement Method for HDR Image Using a Modified Image Formation Model

    NASA Astrophysics Data System (ADS)

    Yun, Byoung-Ju; Hong, Hee-Dong; Choi, Ho-Hyoung

    Poor illumination and viewing conditions have negativeinfluences on the quality of an image, especially the contrast of the dark and bright region. Thus, captured and displayed images usually need contrast enhancement. Histogram-based or gamma correction-based methods are generally utilized for this. However, these methods are global contrast enhancement method, and since the sensitivity of the human eye changes locally according to the position of the object and the illumination in the scene, the global contrast enhancement methods have a limit. The spatial adaptive method is needed to overcome these limitations and it has led to the development of an integrated surround retinex (ISR), and estimation of dominant chromaticity (EDC) methods. However, these methods are based on Gray-World Assumption, and they use a general image formation model, so the color constancy is known to get poor results, shown through graying-out, halo-artifacts (ringing effects), and the dominated color. This paper presents a contrast enhancement method using a modified image formation model in which the image is divided into three components: global illumination, local illumination and reflectance. After applying the power constant value to control the contrast in the resulting image, the output image is obtained from their product to avoid or minimize a color distortion, based on the sRGB color representation. The experimental results show that the proposed method yields better performances than conventional methods.

  10. Adaptive optimisation of a generalised phase contrast beam shaping system

    PubMed Central

    Kenny, F.; Choi, F.S.; Glückstad, J.; Booth, M.J.

    2015-01-01

    The generalised phase contrast (GPC) method provides versatile and efficient light shaping for a range of applications. We have implemented a generalised phase contrast system that used two passes on a single spatial light modulator (SLM). Both the pupil phase distribution and the phase contrast filter were generated by the SLM. This provided extra flexibility and control over the parameters of the system including the phase step magnitude, shape, radius and position of the filter. A feedback method for the on-line optimisation of these properties was also developed. Using feedback from images of the generated light field, it was possible to dynamically adjust the phase filter parameters to provide optimum contrast. PMID:26089573

  11. Algorithms for contrast enhancement of electronic portal images

    NASA Astrophysics Data System (ADS)

    Díez, S.; Sánchez, S.

    2015-11-01

    An implementation of two new automatized image processing algorithms for contrast enhancement of portal images is presented as suitable tools which facilitate the setup verification and visualization of patients during radiotherapy treatments. In the first algorithm, called Automatic Segmentation and Histogram Stretching (ASHS), the portal image is automatically segmented in two sub-images delimited by the conformed treatment beam: one image consisting of the imaged patient obtained directly from the radiation treatment field, and the second one is composed of the imaged patient outside it. By segmenting the original image, a histogram stretching can be independently performed and improved in both regions. The second algorithm involves a two-step process. In the first step, a Normalization to Local Mean (NLM), an inverse restoration filter is applied by dividing pixel by pixel a portal image by its blurred version. In the second step, named Lineally Combined Local Histogram Equalization (LCLHE), the contrast of the original image is strongly improved by a Local Contrast Enhancement (LCE) algorithm, revealing the anatomical structures of patients. The output image is lineally combined with a portal image of the patient. Finally the output images of the previous algorithms (NLM and LCLHE) are lineally combined, once again, in order to obtain a contrast enhanced image. These two algorithms have been tested on several portal images with great results.

  12. Renal stones on portal venous phase contrast-enhanced CT: does intravenous contrast interfere with detection?

    PubMed Central

    Dym, R. Joshua; Duncan, Dameon R.; Spektor, Michael; Cohen, Hillel W.; Scheinfeld, Meir H.

    2015-01-01

    Purpose To determine the sensitivity of portal venous phase contrast-enhanced CT for the detection of renal stones. Methods This retrospective study included 97 CT examinations of the abdomen without and with intravenous contrast, including 85 (87.6%) examinations with at least one renal stone on the “gold standard” noncontrast images, as scored by a single radiologist. Three other radiologists each independently reviewed only the contrast-enhanced images from all 97 examinations and recorded all renal stones. Reviewer sensitivity for stones was categorized by stone diameter. Reviewer sensitivity and specificity for stone disease were also calculated on a per-kidney basis. Results The 97 cases included a total of 238 stones ≥1 mm, with a mean (±SD) of 1.2 ± 1.9 stones per kidney and a stone diameter of 3.5 ± 3.0 mm. Pooling data for the three reviewers, sensitivity for all stones was 81%; sensitivity for stones ≥2, ≥3, ≥4, and ≥5 mm was 88%, 95%, 99%, and 98%, respectively. Sensitivity for stone disease on a per-kidney basis was 94% when considering all stones; when considering only stones ≥2, ≥3, and ≥4 mm, sensitivity was 96%, 99%, and 100%, respectively. Specificity for stone disease on a per-kidney basis was 98% overall, 99% when considering only stones ≥2 mm, and 100% when considering only stones ≥3 mm. Conclusion: Contrast-enhanced CT is highly sensitive for the detection of renal stones ≥3 mm in diameter and less sensitive for smaller stones. In cases where the clinical diagnosis is uncertain and performance of a CT examination is being contemplated, intravenous contrast utilization would allow assessment for stone disease while also optimizing evaluation for other conditions. PMID:24504541

  13. Photoacoustic contrast enhancement using selective subband imaging: experimental results

    NASA Astrophysics Data System (ADS)

    Wei, Chen-Wei; Sheu, Yae-lin; Li, Pai-Chi

    2007-02-01

    In photoacoustic imaging, the difference of optical absorption determines the contrast between two media. In this study, a contrast enhancement method based on choosing various frequency subbands for photoacoustic imaging is proposed. Typically, a laser beam irradiates a medium of interest, and the optical energy decays with different rates as the optical absorption changes. The decay profiles result in acoustic pressure waveforms to propagate with various frequency components, which cause the acoustic frequency variation. The frequency band for a medium with high absorption is found significantly up-shifted from that for a medium with one order lower absorption. Accordingly, besides the amplitude difference due to the absorption, the contrast between two media with varied absorption can be further enhanced by choosing a high frequency band of the receiving signals for imaging. This method was demonstrated by simulations and experiments. The simulation, which is based on the Beer-Lambert law, verified the appearance of frequency variation due to the disparity of absorption coefficients. The experiments were performed by using agar phantom with various concentrations of graphite to create optical absorptions with more than tens times difference. For absorbers with absorption coefficients from 2.5 cm -1 to 100 cm -1, the peak frequencies and the -6 dB bandwidths of the PA signals increase from 1.17 to 3.83 MHz and from 2.17 to 7.58 MHz, respectively. The subband image at band 7-14 MHz shows 13-25 dB intensity difference between two agars with respective absorption of 41.75 cm -1 and 5.01 cm -1, while the difference is 9-15 dB at band 0-7 MHz, thus demonstrating that the contrast can be enhanced between two media using the selective subband imaging. The potential of improving the contrast between biological tissues and contrast agent with a significant higher absorption is revealed.

  14. 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.

  15. Application of plasmonic silver films in histology for contrast enhancement

    NASA Astrophysics Data System (ADS)

    Motevich, I. G.; Strekal, N. D.; Shulha, A. V.; Basinski, V. A.; Maskevich, S. A.

    2012-09-01

    We have studied the absorption spectra and micrographs of sections of cells of the epithelium and andenocarcinoma of the large intestine, immobilized between standard glass slides and cover glasses and plasmonic silver films. We have shown that when we use a microtome technique and specially selected plasmonic silver films, we can achieve enhancement of the image contrast in analysis of the cell morphology as a result of the increase in the light absorption and scattering cross sections with the contrasting stains hematoxylin and eosin.

  16. Prism adaptation contrasts perceptual habituation for repetitive somatosensory stimuli.

    PubMed

    Torta, D M; Tatu, M K; Cotroneo, D; Alamia, A; Folegatti, A; Trojan, J

    2016-03-01

    Prism adaptation (PA) is a non-invasive procedure that requires performing a visuo-motor pointing task while wearing prism goggles inducing a visual displacement of the pointed target. This procedure involves a reorganization of sensorimotor coordination, and induces long-lasting effects on numerous higher-order cognitive functions in healthy volunteers and neglect patients. Prismatic displacement (PD) of the visual field can be induced when prisms are worn but no sensorimotor task is required. In this case, it is unlikely that any subsequent reorganization takes place. The effects of PD are short-lived in the sense that they last as long as prisms are worn. In this study we aimed, to the best of our knowledge for the first time, at investigating whether PA and PD induce changes in the perception of intensity of nociceptive and non- nociceptive somatosensory stimuli. We induced, in healthy volunteers, PD (experiment 1), or PA (experiment 2) and asked participants to rate the intensity of the stimuli applied to the hand undergoing the visuo-proprioceptive conflict (experiment 1) or adaptation (experiment 2). Our results indicate that: 1) the visuo-proprioceptive conflict induced by PD does not reduce the perceived intensity of the stimuli, 2) PA prevents perceptual habituation for both nociceptive and non-nociceptive somatosensory stimuli. Moreover, to investigate the possible underlying mechanisms of the effects of PA we conducted a third experiment in which stimuli were applied both at the adapted and the non-adapted hand. In line with the results of experiment 2, we found that perceptual habituation was prevented for stimuli applied onto the adapted hand. Moreover, we observed the same finding for stimuli applied onto the non-adapted hand. This result suggests that the detention of habituation is not merely driven by changes in spatial attention allocation. Taken together, these data indicate that prisms can affect the perceived intensity of somatosensory stimuli

  17. Microvascular contrast enhancement in optical coherence tomography using microbubbles

    NASA Astrophysics Data System (ADS)

    Assadi, Homa; Demidov, Valentin; Karshafian, Raffi; Douplik, Alexandre; Vitkin, I. Alex

    2016-07-01

    Gas microbubbles (MBs) are investigated as intravascular optical coherence tomography (OCT) contrast agents. Agar + intralipid scattering tissue phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood + MB. Swept-source structural and speckle variance (sv) OCT images, as well as speckle decorrelation times, were evaluated under both no-flow and varying flow conditions. Faster decorrelation times and higher structural and svOCT image contrasts were detected in the presence of MB in all experiments. The effects were largest in the svOCT imaging mode, and uniformly diminished with increasing flow velocity. These findings suggest the feasibility of utilizing MB for tissue hemodynamic investigations and for microvasculature contrast enhancement in OCT angiography.

  18. Contrast-enhanced ultrasound (CEUS) in blunt abdominal trauma.

    PubMed

    Miele, Vittorio; Piccolo, Claudia Lucia; Galluzzo, Michele; Ianniello, Stefania; Sessa, Barbara; Trinci, Margherita

    2016-01-01

    Baseline ultrasound is essential in the early assessment of patients with a huge haemoperitoneum undergoing an immediate abdominal surgery; nevertheless, even with a highly experienced operator, it is not sufficient to exclude parenchymal injuries. More recently, a new ultrasound technique using second generation contrast agents, named contrast-enhanced ultrasound (CEUS) has been developed. This technique allows all the vascular phase to be performed in real time, increasing ultrasound capability to detect parenchymal injuries, enhancing some qualitative findings, such as lesion extension, margins and its relationship with capsule and vessels. CEUS has been demonstrated to be almost as sensitive as contrast-enhanced CT in the detection of traumatic injuries in patients with low-energy isolated abdominal trauma, with levels of sensitivity and specificity up to 95%. Several studies demonstrated its ability to detect lesions occurring in the liver, spleen, pancreas and kidneys and also to recognize active bleeding as hyperechoic bands appearing as round or oval spots of variable size. Its role seems to be really relevant in paediatric patients, thus avoiding a routine exposure to ionizing radiation. Nevertheless, CEUS is strongly operator dependent, and it has some limitations, such as the cost of contrast media, lack of panoramicity, the difficulty to explore some deep regions and the poor ability to detect injuries to the urinary tract. On the other hand, it is timesaving, and it has several advantages, such as its portability, the safety of contrast agent, the lack to ionizing radiation exposure and therefore its repeatability, which allows follow-up of those traumas managed conservatively, especially in cases of fertile females and paediatric patients. PMID:26607647

  19. 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

  20. Real-time adaptive video image enhancement

    NASA Astrophysics Data System (ADS)

    Garside, John R.; Harrison, Chris G.

    1999-07-01

    As part of a continuing collaboration between the University of Manchester and British Aerospace, a signal processing array has been constructed to demonstrate that it is feasible to compensate a video signal for the degradation caused by atmospheric haze in real-time. Previously reported work has shown good agreement between a simple physical model of light scattering by atmospheric haze and the observed loss of contrast. This model predicts a characteristic relationship between contrast loss in the image and the range from the camera to the scene. For an airborne camera, the slant-range to a point on the ground may be estimated from the airplane's pose, as reported by the inertial navigation system, and the contrast may be obtained from the camera's output. Fusing data from these two streams provides a means of estimating model parameters such as the visibility and the overall illumination of the scene. This knowledge allows the same model to be applied in reverse, thus restoring the contrast lost to atmospheric haze. An efficient approximation of range is vital for a real-time implementation of the method. Preliminary results show that an adaptive approach to fitting the model's parameters, exploiting the temporal correlation between video frames, leads to a robust implementation with a significantly accelerated throughput.

  1. Effective contrast enhancement method for color night vision

    NASA Astrophysics Data System (ADS)

    Qian, Xiaoyan; Wang, Yujin; Wang, Bangfeng

    2012-01-01

    Image fusion refers to the techniques that integrate complementary information from multiple image sensors' data in a way that makes the new images more suitable for human visual perception. The paper focuses on the low color contrast problem of linear fusion algorithms with color transfer method. Firstly, the contrast of infrared and visible images is enhanced using local histogram equalization and median filter. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To enhance the color contrast between the target and the background, the scaling factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot and cold targets are all popped out with intense colors while the background details present natural color appearance. Target detection experiments through target recognition area, detection rate, target-background discrimination also show that the presented method has a better performance than the former methods.

  2. Reversibly switchable fluorescence microscopy with enhanced resolution and image contrast.

    PubMed

    Yao, Junjie; Shcherbakova, Daria M; Li, Chiye; Krumholz, Arie; Lorca, Ramon A; Reinl, Erin; England, Sarah K; Verkhusha, Vladislav V; Wang, Lihong V

    2014-08-01

    Confocal microscopy with optical sectioning has revolutionized biological studies by providing sharper images than conventional optical microscopy. Here, we introduce a fluorescence imaging method with enhanced resolution and imaging contrast, which can be implemented using a commercial confocal microscope setup. This approach, called the reversibly switchable photo-imprint microscopy (rsPIM), is based on the switching dynamics of reversibly switchable fluorophores. When the fluorophores are switched from the bright (ON) state to the dark (OFF) state, their switching rate carries the information about the local excitation light intensity. In rsPIM, a polynomial function is used to fit the fluorescence signal decay during the transition. The extracted high-order coefficient highlights the signal contribution from the center of the excitation volume, and thus sharpens the resolution in all dimensions. In particular, out-of-focus signals are greatly blocked for large targets, and thus the image contrast is considerably enhanced. Notably, since the fluorophores can be cycled between the ON and OFF states, the whole imaging process can be repeated. RsPIM imaging with enhanced image contrast was demonstrated in both fixed and live cells using a reversibly switchable synthetic dye and a genetically encoded red fluorescent protein. Since rsPIM does not require the modification of commercial microscope systems, it may provide a simple and cost-effective solution for subdiffraction imaging of live cells. PMID:25144452

  3. Cumulative phase delay imaging for contrast-enhanced ultrasound tomography

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Standard dynamic-contrast enhanced ultrasound (DCE-US) imaging detects and estimates ultrasound-contrast-agent (UCA) concentration based on the amplitude of the nonlinear (harmonic) components generated during ultrasound (US) propagation through UCAs. However, harmonic components generation is not specific to UCAs, as it also occurs for US propagating through tissue. Moreover, nonlinear artifacts affect standard DCE-US imaging, causing contrast to tissue ratio reduction, and resulting in possible misclassification of tissue and misinterpretation of UCA concentration. Furthermore, no contrast-specific modality exists for DCE-US tomography; in particular speed-of-sound changes due to UCAs are well within those caused by different tissue types. Recently, a new marker for UCAs has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental component is in fact observable for US propagating through UCAs, and is absent in tissue. In this paper, tomographic US images based on CPD are for the first time presented and compared to speed-of-sound US tomography. Results show the applicability of this marker for contrast specific US imaging, with cumulative phase delay imaging (CPDI) showing superior capabilities in detecting and localizing UCA, as compared to speed-of-sound US tomography. Cavities (filled with UCA) which were down to 1 mm in diameter were clearly detectable. Moreover, CPDI is free of the above mentioned nonlinear artifacts. These results open important possibilities to DCE-US tomography, with potential applications to breast imaging for cancer localization.

  4. Contrast-enhanced ultrasonographic findings of hepatic paragonimiasis

    PubMed Central

    Lu, Qiang; Ling, Wen-Wu; Ma, Lin; Huang, Zi-Xing; Lu, Chang-Li; Luo, Yan

    2013-01-01

    AIM: To investigate the features of hepatic paragonimiasis on contrast-enhanced ultrasound (CEUS) imaging. METHODS: Fifteen patients with hepatic paragonimiasis who were admitted to our hospital between March 2008 and August 2012 were enrolled to this study. The conventional ultrasound and CEUS examinations were performed with a Philips IU22 scanner with a 1-5-MHz convex transducer. After conventional ultrasound scanning was completed, the CEUS study was performed. Pulse inversion harmonic imaging was used for CEUS. A bolus injection of 2.4 mL of a sulfur hexafluoride-filled microbubble contrast agent (SonoVue) was administered. CEUS features were retrospectively reviewed and correlated with pathological findings. RESULTS: In total, 16 lesions were detected on CEUS. The mean size of the lesions was 4.4 ± 1.6 cm (range, 1.7-6.6 cm). Subcapsular location was found in 12 lesions (75%). All the lesions were hypoechoic. Six lesions (37.5%) were of mixed content, seven (43.8%) were solid with small cystic areas, and the other three (18.8%) were completely solid. Ten lesions (62.5%) were rim enhanced with irregular tract-like nonenhanced internal areas. Transient wedge-shaped hyperenhancement of the surrounding liver parenchyma was seen in seven lesions (43.8%). Areas with hyper- or iso-enhancement in the arterial phase showed contrast wash-out and appeared hypoenhanced in the late phase. The main pathological findings included: (1) coagulative or liquefactive necrosis within the lesion, infiltration of a large number of eosinophils with the formation of chronic eosinophilic abscesses and sporadic distribution of Charcot-Leyden crystals; and (2) hyperplasia of granulomatous and fibrous tissue around the lesion. CONCLUSION: Subcapsular location, hypoechogenicity, rim enhancement and tract-like nonenhanced areas could be seen as the main CEUS features of hepatic paragonimiasis. PMID:23599629

  5. Diffraction enhanced imaging contrast mechanisms and applications to medicine

    NASA Astrophysics Data System (ADS)

    Hasnah, Moumen Omar

    X-rays are one of the most commonly used forms of radiation in medical diagnostic imaging because of their ability to penetrate the body and give morphological information. Although several interactions may occur, as the x-ray photons traverse the object being radiographed, all of the common x-ray imaging techniques are based on absorption contrast. The fact that the density variations of these tissues are small makes soft tissue imaging difficult with x-rays. A number of imaging modalities have been developed to address the problem of soft tissue imaging that are of clinical relevance. These modalities typically use alternate methods of visualization based on sound propagation (ultrasound), proton density (Magnetic Resonance Imaging-MRI), and others. In addition, enhancements to the x-ray technique include computed tomography (Computed Axial Tomography---CAT) that has more sensitivity to tissue density, phase contrast methods relying on the phase of the traversing x-rays, and refraction methods such as Diffraction Enhanced Imaging (DEI). Of these techniques, ultrasound, MRI and CAT scans are presently common clinical techniques that are used to assist in the diagnosis and isolation of lesions in tissue. DEI is experimental technique that may someday be clinical used due to the high soft tissue contrast.

  6. Contrast-enhancement techniques for particle-image velocimetry.

    PubMed

    Dellenback, P A; Macharivilakathu, J; Pierce, S R

    2000-11-10

    In video-based particle-image velocimetry (PIV) systems for fluid mechanics research, it is sometimes desirable to image seed particles to be smaller than a camera pixel. However, imaging to this size can lead to marginal image contrast such that significant numbers of erroneous velocity vectors can be computed, even for simple flow fields. A variety of image-enhancement techniques suitable for a low-cost PIV system that uses video cameras are examined and tested on three representative flows. Techniques such as linear contrast enhancement and histogram hyperbolization are shown to have good potential for improving the image contrast and hence the accuracy of the data-reduction process with only a 15% increase in the computational time. Some other schemes that were examined appear to be of little practical value in PIV applications. An automated shifting algorithm based on mass conservation is shown to be useful for displacing the second interrogation region in the direction of flow, which minimizes the number of uncorrelated particle images that contribute noise to the data-reduction process. PMID:18354603

  7. Aging and luminance-adaptation effects on spatial contrast sensitivity.

    PubMed

    Sloane, M E; Owsley, C; Jackson, C A

    1988-12-01

    Contrast sensitivity as a function of target luminance for four spatial frequencies (0.5, 2, 4, and 8 cycles/deg) was measured in younger (n = 12; age range, 19-35 years) and older (n = 11; age range, 68-79 years) adults in order to examine the feasibility of optical and neural explanations for the impairment of contrast sensitivity in older adults. All subjects were free from identifiable ocular disease and had good acuity. Sensitivity for each spatial frequency was measured at eight luminance levels spanning 3.5 log units in the photopic-mesopic range. When gratings were flickered at 0.5 Hz, functions for older adults were displaced downward on the sensitivity axis across all luminance levels, and the slopes of these functions were steeper than those for younger adults, suggesting that optical mechanisms alone cannot account for the vision loss in older adults. Further measurements, in which spatial targets were flickered at 7.5 Hz, indicated that this faster temporal modulation affected sensitivity as a function of luminance differentially in younger and older adults. These data imply that the neural mechanisms subserving human spatial vision undergo significant changes during adulthood.

  8. Contrast-Enhanced Ultrasonography in Crohn's Disease Diagnostics.

    PubMed

    Białecki, Marcin; Białecka, Agnieszka; Laskowska, Katarzyna; Liebert, Ariel; Kłopocka, Maria; Serafin, Zbigniew

    2015-06-01

    The chronic nature of Crohn's disease (CD) implicates necessity of multiple control assessments throughout patient's life. It is accepted that in patients with CD requiring disease monitoring, magnetic resonance enterography (MRE) and computed tomography enterography (CTE) are--apart from endoscopy--imaging studies of first choice. In practice, diagnostic imaging of patients with CD is troublesome, since MRE is an expensive and complicated study, and CTE exposes patients to high doses of ionizing radiation. Therefore, there is a need for new, both non-invasive and effective, methods of imaging in CD. Contrast-Enhanced Ultrasonography (CEUS) is a relatively new method using gas-filled microbubbles serving as contrast agent. It allows for detailed assessment of blood perfusion within intestine wall and peri-intestinal tissues, which enables detection and monitoring of inflammation and its qualitative assessment. The purpose of this paper is to describe CEUS examination technique and its clinical applications in patients with Crohn's disease. PMID:26902030

  9. Contrast enhancement of propagation based X-ray phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Pan, Adam; Xu, Ling; Petruccelli, Jon C.; Gupta, Rajiv; Barbastathis, George

    2014-09-01

    We demonstrate a quantitative X-ray phase contrast imaging (XPCI) technique derived from propagation dependent phase change. We assume that the absorption and phase components are correlated and solve the Transport of Intensity Equation (TIE). The experimental setup is simple compared to other XPCI techniques; the only requirements are a micro-focus X-ray source with sufficient temporal coherence and an X-ray detector of sufficient spatial resolution. This method was demonstrated in three scenarios, the first of which entails identification of an index-matched sphere. A rubber and nylon sphere were immersed in water and imaged. While the rubber sphere could be plainly seen on a radiograph, the nylon sphere was only visible in the phase reconstruction. Next, the technique was applied to differentiating liquid samples. In this scenario, three liquid samples (acetone, water, and hydrogen peroxide) were analyzed using both conventional computed tomography (CT) and phase contrast CT. While conventional CT was capable of differentiating between acetone and the other two liquids, it failed to distinguish between water and hydrogen peroxide; only phase CT was capable of differentiating all three samples. Finally, the technique was applied to CT imaging of a human artery specimen with extensive atherosclerotic plaque. This scenario demonstrated the increased sensitivity to soft tissue compared to conventional CT; it also uncovered some drawbacks of the method, which will be the target of future work. In all cases, the signal-to-noise ratio of phase contrast was greatly enhanced relative to conventional attenuation-based imaging.

  10. Assessment of mass detection performance in contrast enhanced digital mammography

    NASA Astrophysics Data System (ADS)

    Carton, Ann-Katherine; de Carvalho, Pablo M.; Li, Zhijin; Dromain, Clarisse; Muller, Serge

    2015-03-01

    We address the detectability of contrast-agent enhancing masses for contrast-agent enhanced spectral mammography (CESM), a dual-energy technique providing functional projection images of breast tissue perfusion and vascularity using simulated CESM images. First, the realism of simulated CESM images from anthropomorphic breast software phantoms generated with a software X-ray imaging platform was validated. Breast texture was characterized by power-law coefficients calculated in data sets of real clinical and simulated images. We also performed a 2-alternative forced choice (2-AFC) psychophysical experiment whereby simulated and real images were presented side-by-side to an experienced radiologist to test if real images could be distinguished from the simulated images. It was found that texture in our simulated CESM images has a fairly realistic appearance. Next, the relative performance of human readers and previously developed mathematical observers was assessed for the detection of iodine-enhancing mass lesions containing different contrast agent concentrations. A four alternative-forced-choice (4 AFC) task was designed; the task for the model and human observer was to detect which one of the four simulated DE recombined images contained an iodineenhancing mass. Our results showed that the NPW and NPWE models largely outperform human performance. After introduction of an internal noise component, both observers approached human performance. The CHO observer performs slightly worse than the average human observer. There is still work to be done in improving model observers as predictors of human-observer performance. Larger trials could also improve our test statistics. We hope that in the future, this framework of software breast phantoms, virtual image acquisition and processing, and mathematical observers can be beneficial to optimize CESM imaging techniques.

  11. Optimization of Polarimetric Contrast Enhancement Based on Fisher Criterion

    NASA Astrophysics Data System (ADS)

    Deng, Qiming; Chen, Jiong; Yang, Jian

    The optimization of polarimetric contrast enhancement (OPCE) is a widely used method for maximizing the received power ratio of a desired target versus an undesired target (clutter). In this letter, a new model of the OPCE is proposed based on the Fisher criterion. By introducing the well known two-class problem of linear discriminant analysis (LDA), the proposed model is to enlarge the normalized distance of mean value between the target and the clutter. In addition, a cross-iterative numerical method is proposed for solving the optimization with a quadratic constraint. Experimental results with the polarimetric SAR (POLSAR) data demonstrate the effectiveness of the proposed method.

  12. 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.

  13. Enhancing astronaut performance using sensorimotor adaptability training.

    PubMed

    Bloomberg, Jacob J; Peters, Brian T; Cohen, Helen S; Mulavara, Ajitkumar P

    2015-01-01

    Astronauts experience disturbances in balance and gait function when they return to Earth. The highly plastic human brain enables individuals to modify their behavior to match the prevailing environment. Subjects participating in specially designed variable sensory challenge training programs can enhance their ability to rapidly adapt to novel sensory situations. This is useful in our application because we aim to train astronauts to rapidly formulate effective strategies to cope with the balance and locomotor challenges associated with new gravitational environments-enhancing their ability to "learn to learn." We do this by coupling various combinations of sensorimotor challenges with treadmill walking. A unique training system has been developed that is comprised of a treadmill mounted on a motion base to produce movement of the support surface during walking. This system provides challenges to gait stability. Additional sensory variation and challenge are imposed with a virtual visual scene that presents subjects with various combinations of discordant visual information during treadmill walking. This experience allows them to practice resolving challenging and conflicting novel sensory information to improve their ability to adapt rapidly. Information obtained from this work will inform the design of the next generation of sensorimotor countermeasures for astronauts. PMID:26441561

  14. Enhancing astronaut performance using sensorimotor adaptability training.

    PubMed

    Bloomberg, Jacob J; Peters, Brian T; Cohen, Helen S; Mulavara, Ajitkumar P

    2015-01-01

    Astronauts experience disturbances in balance and gait function when they return to Earth. The highly plastic human brain enables individuals to modify their behavior to match the prevailing environment. Subjects participating in specially designed variable sensory challenge training programs can enhance their ability to rapidly adapt to novel sensory situations. This is useful in our application because we aim to train astronauts to rapidly formulate effective strategies to cope with the balance and locomotor challenges associated with new gravitational environments-enhancing their ability to "learn to learn." We do this by coupling various combinations of sensorimotor challenges with treadmill walking. A unique training system has been developed that is comprised of a treadmill mounted on a motion base to produce movement of the support surface during walking. This system provides challenges to gait stability. Additional sensory variation and challenge are imposed with a virtual visual scene that presents subjects with various combinations of discordant visual information during treadmill walking. This experience allows them to practice resolving challenging and conflicting novel sensory information to improve their ability to adapt rapidly. Information obtained from this work will inform the design of the next generation of sensorimotor countermeasures for astronauts.

  15. Enhancing astronaut performance using sensorimotor adaptability training

    PubMed Central

    Bloomberg, Jacob J.; Peters, Brian T.; Cohen, Helen S.; Mulavara, Ajitkumar P.

    2015-01-01

    Astronauts experience disturbances in balance and gait function when they return to Earth. The highly plastic human brain enables individuals to modify their behavior to match the prevailing environment. Subjects participating in specially designed variable sensory challenge training programs can enhance their ability to rapidly adapt to novel sensory situations. This is useful in our application because we aim to train astronauts to rapidly formulate effective strategies to cope with the balance and locomotor challenges associated with new gravitational environments—enhancing their ability to “learn to learn.” We do this by coupling various combinations of sensorimotor challenges with treadmill walking. A unique training system has been developed that is comprised of a treadmill mounted on a motion base to produce movement of the support surface during walking. This system provides challenges to gait stability. Additional sensory variation and challenge are imposed with a virtual visual scene that presents subjects with various combinations of discordant visual information during treadmill walking. This experience allows them to practice resolving challenging and conflicting novel sensory information to improve their ability to adapt rapidly. Information obtained from this work will inform the design of the next generation of sensorimotor countermeasures for astronauts. PMID:26441561

  16. Adaptive enhancement method of infrared image based on scene feature

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao; Bai, Tingzhu; Shang, Fei

    2008-12-01

    All objects emit radiation in amounts related to their temperature and their ability to emit radiation. The infrared image shows the invisible infrared radiation emitted directly. Because of the advantages, the technology of infrared imaging is applied to many kinds of fields. But compared with visible image, the disadvantages of infrared image are obvious. The characteristics of low luminance, low contrast and the inconspicuous difference target and background are the main disadvantages of infrared image. The aim of infrared image enhancement is to improve the interpretability or perception of information in infrared image for human viewers, or to provide 'better' input for other automated image processing techniques. Most of the adaptive algorithm for image enhancement is mainly based on the gray-scale distribution of infrared image, and is not associated with the actual image scene of the features. So the pertinence of infrared image enhancement is not strong, and the infrared image is not conducive to the application of infrared surveillance. In this paper we have developed a scene feature-based algorithm to enhance the contrast of infrared image adaptively. At first, after analyzing the scene feature of different infrared image, we have chosen the feasible parameters to describe the infrared image. In the second place, we have constructed the new histogram distributing base on the chosen parameters by using Gaussian function. In the last place, the infrared image is enhanced by constructing a new form of histogram. Experimental results show that the algorithm has better performance than other methods mentioned in this paper for infrared scene images.

  17. Optimal exposure techniques for iodinated contrast enhanced breast CT

    NASA Astrophysics Data System (ADS)

    Glick, Stephen J.; Makeev, Andrey

    2016-03-01

    Screening for breast cancer using mammography has been very successful in the effort to reduce breast cancer mortality, and its use has largely resulted in the 30% reduction in breast cancer mortality observed since 1990 [1]. However, diagnostic mammography remains an area of breast imaging that is in great need for improvement. One imaging modality proposed for improving the accuracy of diagnostic workup is iodinated contrast-enhanced breast CT [2]. In this study, a mathematical framework is used to evaluate optimal exposure techniques for contrast-enhanced breast CT. The ideal observer signal-to-noise ratio (i.e., d') figure-of-merit is used to provide a task performance based assessment of optimal acquisition parameters under the assumptions of a linear, shift-invariant imaging system. A parallel-cascade model was used to estimate signal and noise propagation through the detector, and a realistic lesion model with iodine uptake was embedded into a structured breast background. Ideal observer performance was investigated across kVp settings, filter materials, and filter thickness. Results indicated many kVp spectra/filter combinations can improve performance over currently used x-ray spectra.

  18. Contrast-enhanced ultrasound of histologically proven hepatic epithelioid hemangioendothelioma

    PubMed Central

    Dong, Yi; Wang, Wen-Ping; Cantisani, Vito; D’Onofrio, Mirko; Ignee, Andre; Mulazzani, Lorenzo; Saftoiu, Adrian; Sparchez, Zeno; Sporea, Ioan; Dietrich, Christoph F

    2016-01-01

    AIM: To analyze contrast-enhanced ultrasound (CEUS) features of histologically proven hepatic epithelioid hemangioendothelioma (HEHE) in comparison to other multilocular benign focal liver lesions (FLL). METHODS: Twenty-five patients with histologically proven HEHE and 45 patients with histologically proven multilocular benign FLL were retrospectively reviewed. Four radiologists assessed the CEUS enhancement pattern in consensus. RESULTS: HEHE manifested as a single (n = 3) or multinodular (n = 22) FLL. On CEUS, HEHE showed rim-like (18/25, 72%) or heterogeneous hyperenhancement (7/25, 28%) in the arterial phase and hypoenhancement (25/25, 100%) in the portal venous and late phases (PVLP), a sign of malignancy. Eighteen patients showed central unenhanced areas (18/25, 72%); in seven patients (7/25, 28%), more lesions were detected in the PVLP. In contrast, all patients with hemangioma and focal nodular hyperplasia showed hyperenhancement as the most distinctive feature (P < 0.01). CONCLUSION: CEUS allows for characterization of unequivocal FLL. By analyzing the hypoenhancement in the PVLP, CEUS can determine the malignant nature of HEHE. PMID:27217705

  19. Fast color contrast enhancement method for color night vision

    NASA Astrophysics Data System (ADS)

    Qian, Xiaoyan; Wang, Yujin; Wang, Bangfeng

    2012-01-01

    The increasing availability and deployment of imaging sensors operating in multiple spectral bands has led to a large research effort in color image fusion, resulting in a plethora of pixel-level image fusion algorithms. In this study a simple and fast fusion approach for color night vision is presented. The contrast of infrared and visible images is adjusted by local histogram equalization. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To obtain false color images possessing a natural day-time color appearance, this paper adopts an approach which transfers color from the reference to the fused images in a simplified Lab space. To enhance the contrast between the target and the background, a stretch factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot targets are popped out with intense colors while the background details present natural color appearance. Target detection experiments also show that the presented method has a better performance than the former methods, owing to the target recognition area, detection rate, color distance and running time.

  20. Enhancing Tabletop X-Ray Phase Contrast Imaging with Nano-Fabrication.

    PubMed

    Miao, Houxun; Gomella, Andrew A; Harmon, Katherine J; Bennett, Eric E; Chedid, Nicholas; Znati, Sami; Panna, Alireza; Foster, Barbara A; Bhandarkar, Priya; Wen, Han

    2015-01-01

    X-ray phase-contrast imaging is a promising approach for improving soft-tissue contrast and lowering radiation dose in biomedical applications. While current tabletop imaging systems adapt to common x-ray tubes and large-area detectors by employing absorptive elements such as absorption gratings or monolithic crystals to filter the beam, we developed nanometric phase gratings which enable tabletop x-ray far-field interferometry with only phase-shifting elements, leading to a substantial enhancement in the performance of phase contrast imaging. In a general sense the method transfers the demands on the spatial coherence of the x-ray source and the detector resolution to the feature size of x-ray phase masks. We demonstrate its capabilities in hard x-ray imaging experiments at a fraction of clinical dose levels and present comparisons with the existing Talbot-Lau interferometer and with conventional digital radiography.

  1. Enhancing Tabletop X-Ray Phase Contrast Imaging with Nano-Fabrication

    PubMed Central

    Miao, Houxun; Gomella, Andrew A.; Harmon, Katherine J.; Bennett, Eric E.; Chedid, Nicholas; Znati, Sami; Panna, Alireza; Foster, Barbara A.; Bhandarkar, Priya; Wen, Han

    2015-01-01

    X-ray phase-contrast imaging is a promising approach for improving soft-tissue contrast and lowering radiation dose in biomedical applications. While current tabletop imaging systems adapt to common x-ray tubes and large-area detectors by employing absorptive elements such as absorption gratings or monolithic crystals to filter the beam, we developed nanometric phase gratings which enable tabletop x-ray far-field interferometry with only phase-shifting elements, leading to a substantial enhancement in the performance of phase contrast imaging. In a general sense the method transfers the demands on the spatial coherence of the x-ray source and the detector resolution to the feature size of x-ray phase masks. We demonstrate its capabilities in hard x-ray imaging experiments at a fraction of clinical dose levels and present comparisons with the existing Talbot-Lau interferometer and with conventional digital radiography. PMID:26315891

  2. Stent enhancement in digital x-ray fluoroscopy using an adaptive feature enhancement filter

    NASA Astrophysics Data System (ADS)

    Jiang, Yuhao; Zachary, Josey

    2016-03-01

    Fluoroscopic images belong to the classes of low contrast and high noise. Simply lowering radiation dose will render the images unreadable. Feature enhancement filters can reduce patient dose by acquiring images at low dose settings and then digitally restoring them to the original quality. In this study, a stent contrast enhancement filter is developed to selectively improve the contrast of stent contour without dramatically boosting the image noise including quantum noise and clinical background noise. Gabor directional filter banks are implemented to detect the edges and orientations of the stent. A high orientation resolution of 9° is used. To optimize the use of the information obtained from Gabor filters, a computerized Monte Carlo simulation followed by ROC study is used to find the best nonlinear operator. The next stage of filtering process is to extract symmetrical parts in the stent. The global and local symmetry measures are used. The information gathered from previous two filter stages are used to generate a stent contour map. The contour map is then scaled and added back to the original image to get a contrast enhanced stent image. We also apply a spatio-temporal channelized Hotelling observer model and other numerical measures to characterize the response of the filters and contour map to optimize the selections of parameters for image quality. The results are compared to those filtered by an adaptive unsharp masking filter previously developed. It is shown that stent enhancement filter can effectively improve the stent detection and differentiation in the interventional fluoroscopy.

  3. Contrast-Enhanced Harmonic Endoscopic Ultrasonography of Solid Pancreatic Lesions

    PubMed Central

    Kwek, Boon Eu Andrew; Ang, Tiing Leong; Seo, Dong Wan; Imazu, Hiroo

    2013-01-01

    Endoscopic ultrasonography is the best modality for pancreatic lesion evaluation as its superior spatial resolution allows small lesions to be identified and fine needle aspiration (FNA) cytology performed under ultrasound-guidance. Despite this, differentiating benign from malignant lesions remains a challenge as conventional ultrasound imaging is unable to differentiate lesions accurately and tissue yield is poorly diagnostic or limited in patients with the chronic inflammation. Contrast-harmonic technology uses a wide-band transducer capable of inducing sufficient acoustic energy to create harmonic microbubble oscillations of the newer second-generation ultrasound contrast agents (UCAs). These microbubbles are more stable, remaining within the intravascular component longer and emit significantly more harmonic content than surrounding tissue, thus allowing pancreatic parenchymal differentiation and microvascular architecture visualization. The use of UCAs is generally safe, but should be especially avoided in patients with unstable ischemic heart disease. During CH endosonography, pancreatic adenocarcinoma is commonly seen as an inhomogenous hypoenhancing lesion, focal pancreatitis as a hypo- or iso-enhancing lesion and neuroendocrine tumor as a hyperenhancing lesion. The presence of hyperenhancement is a strong predictor of non-adenocarcinoma etiology. Furthermore, in patients with the chronic pancreatitis or biliary stents that may obscure pancreatic inspection, the addition of contrast-harmonic endosonography to guide FNA cytology improves its diagnostic yield and accuracy. Quantitative analysis of perfusion through the time intensity curve is promising as an objective and accurate method to differentiate pancreatic lesions. Furthermore, studies are required to fully determine the role of contrast harmonic endosonography in the differential diagnosis of solid pancreatic lesions. PMID:24949382

  4. Dynamic-contrast-enhanced-MRI with extravasating contrast reagent: Rat cerebral glioma blood volume determination

    NASA Astrophysics Data System (ADS)

    Li, Xin; Rooney, William D.; Várallyay, Csanád G.; Gahramanov, Seymur; Muldoon, Leslie L.; Goodman, James A.; Tagge, Ian J.; Selzer, Audrey H.; Pike, Martin M.; Neuwelt, Edward A.; Springer, Charles S.

    2010-10-01

    The accurate mapping of the tumor blood volume (TBV) fraction ( vb) is a highly desired imaging biometric goal. It is commonly thought that achieving this is difficult, if not impossible, when small molecule contrast reagents (CRs) are used for the T1-weighted (Dynamic-Contrast-Enhanced) DCE-MRI technique. This is because angiogenic malignant tumor vessels allow facile CR extravasation. Here, a three-site equilibrium water exchange model is applied to DCE-MRI data from the cerebrally-implanted rat brain U87 glioma, a tumor exhibiting rapid CR extravasation. Analyses of segments of the (and the entire) DCE data time-course with this "shutter-speed" pharmacokinetic model, which admits finite water exchange kinetics, allow TBV estimation from the first-pass segment. Pairwise parameter determinances were tested with grid searches of 2D parametric error surfaces. Tumor blood volume ( vb), as well as ve (the extracellular, extravascular space volume fraction), and Ktrans (a CR extravasation rate measure) parametric maps are presented. The role of the Patlak Plot in DCE-MRI is also considered.

  5. 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.

  6. 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.

  7. Nanoparticles and nanostructured carriers for drug delivery and contrast enhancement

    NASA Astrophysics Data System (ADS)

    Godage, Olga S.; Bucharskaya, Alla B.; Navolokin, Nikita A.; German, Sergey V.; Zuev, Viktor V.; Terentyuk, Georgy S.; Maslyakova, Galina N.; Gorin, Dmitry A.

    2016-04-01

    Currently, nanotechnologies are widely used in science and industry. It is known that the application of drug delivery nanostructured carriers for biomedicine is one of the promising areas of nanotechnology. Nanostructured carriers can be used in the diagnosis process for detecting a neoplastic tumor cells in peripheral blood, for contrast enhancement on magnetic resonance imaging (MRI), as well as for targeted drug delivery to tumor tissues. Agents for the targeted delivery (nanoparticles, liposomes, microcapsules, and etc) can affect the healthy tissues and organs, cause side effects and have a toxic effect. Therefore, it necessary to study the morphological changes that occur not only in the "target", such as a tumor, but also the internal organs, taking place under the influence of both the agents for targeted drug delivery and physical impact induced remote controlled drug release. Thus , the aim of our work is selection of the most promising agents for targeted drug delivery to tumor and contrast agents for in vivo visualization of tumor tissue boundaries , as well as their impact on the organs and tissues as results of nanostructured object biodistribution.

  8. Dynamic contrast-enhanced 3D photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Wong, Philip; Kosik, Ivan; Carson, Jeffrey J. L.

    2013-03-01

    Photoacoustic imaging (PAI) is a hybrid imaging modality that integrates the strengths from both optical imaging and acoustic imaging while simultaneously overcoming many of their respective weaknesses. In previous work, we reported on a real-time 3D PAI system comprised of a 32-element hemispherical array of transducers. Using the system, we demonstrated the ability to capture photoacoustic data, reconstruct a 3D photoacoustic image, and display select slices of the 3D image every 1.4 s, where each 3D image resulted from a single laser pulse. The present study aimed to exploit the rapid imaging speed of an upgraded 3D PAI system by evaluating its ability to perform dynamic contrast-enhanced imaging. The contrast dynamics can provide rich datasets that contain insight into perfusion, pharmacokinetics and physiology. We captured a series of 3D PA images of a flow phantom before and during injection of piglet and rabbit blood. Principal component analysis was utilized to classify the data according to its spatiotemporal information. The results suggested that this technique can be used to separate a sequence of 3D PA images into a series of images representative of main features according to spatiotemporal flow dynamics.

  9. Color contrast enhancement method of infrared polarization fused image

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Xie, Chen

    2015-10-01

    As the traditional color fusion method based on color transfer algorithm has an issue that the color of target and background is similar. A kind of infrared polarization image color fusion method based on color contrast enhancement was proposed. Firstly the infrared radiation intensity image and the polarization image were color fused, and then color transfer technology was used between color reference image and initial fused image in the YCbCr color space. Secondly Otsu segmentation method was used to extract the target area image from infrared polarization image. Lastly the H,S,I component of the color fusion image which obtained by color transfer was adjusted to obtain the final fused image by using target area in the HSI space. Experimental results show that, the fused result which obtained by the proposed method is rich in detail and makes the contrast of target and background more outstanding. And then the ability of target detection and identification can be improved by the method.

  10. Adaptive EAGLE dynamic solution adaptation and grid quality enhancement

    NASA Technical Reports Server (NTRS)

    Luong, Phu Vinh; Thompson, J. F.; Gatlin, B.; Mastin, C. W.; Kim, H. J.

    1992-01-01

    In the effort described here, the elliptic grid generation procedure in the EAGLE grid code was separated from the main code into a subroutine, and a new subroutine which evaluates several grid quality measures at each grid point was added. The elliptic grid routine can now be called, either by a computational fluid dynamics (CFD) code to generate a new adaptive grid based on flow variables and quality measures through multiple adaptation, or by the EAGLE main code to generate a grid based on quality measure variables through static adaptation. Arrays of flow variables can be read into the EAGLE grid code for use in static adaptation as well. These major changes in the EAGLE adaptive grid system make it easier to convert any CFD code that operates on a block-structured grid (or single-block grid) into a multiple adaptive code.

  11. Multiple sites of adaptation lead to contrast encoding in the Drosophila olfactory system.

    PubMed

    Cafaro, Jon

    2016-04-01

    Animals often encounter large increases in odor intensity that can persist for many seconds. These increases in the background odor are often accompanied by increases in the variance of the odor stimulus. Previous studies have shown that a persistent odor stimulus (odor background) results in a decrease in the response to brief odor pulses in the olfactory receptor neurons (ORNs). However, the contribution of adapting mechanisms beyond theORNs is not clear. Thus, it is unclear how adaptive mechanisms are distributed within the olfactory circuit and what impact downstream adaptation may have on the encoding of odor stimuli. In this study, adaptation to the same odor stimulus is examined at multiple levels in the well studied and accessibleDrosophilaolfactory system. The responses of theORNs are compared to the responses of the second order, projection neurons (PNs), directly connected to them. Adaptation inPNspike rate was found to be much greater than adaptation in theORNspike rate. This greater adaptation allowsPNs to encode odor contrast (ratio of pulse intensity to background intensity) with little ambiguity. Moreover, distinct neural mechanisms contribute to different aspects of adaptation; adaptation to the background odor is dominated by adaptation in spike generation in bothORNs andPNs, while adaptation to the odor pulse is dominated by changes within olfactory transduction and the glomerulus. These observations suggest that the olfactory system adapts at multiple sites to better match its response gain to stimulus statistics. PMID:27053295

  12. Multiple sites of adaptation lead to contrast encoding in the Drosophila olfactory system.

    PubMed

    Cafaro, Jon

    2016-04-01

    Animals often encounter large increases in odor intensity that can persist for many seconds. These increases in the background odor are often accompanied by increases in the variance of the odor stimulus. Previous studies have shown that a persistent odor stimulus (odor background) results in a decrease in the response to brief odor pulses in the olfactory receptor neurons (ORNs). However, the contribution of adapting mechanisms beyond theORNs is not clear. Thus, it is unclear how adaptive mechanisms are distributed within the olfactory circuit and what impact downstream adaptation may have on the encoding of odor stimuli. In this study, adaptation to the same odor stimulus is examined at multiple levels in the well studied and accessibleDrosophilaolfactory system. The responses of theORNs are compared to the responses of the second order, projection neurons (PNs), directly connected to them. Adaptation inPNspike rate was found to be much greater than adaptation in theORNspike rate. This greater adaptation allowsPNs to encode odor contrast (ratio of pulse intensity to background intensity) with little ambiguity. Moreover, distinct neural mechanisms contribute to different aspects of adaptation; adaptation to the background odor is dominated by adaptation in spike generation in bothORNs andPNs, while adaptation to the odor pulse is dominated by changes within olfactory transduction and the glomerulus. These observations suggest that the olfactory system adapts at multiple sites to better match its response gain to stimulus statistics.

  13. Adaptive Intuitionistic Fuzzy Enhancement of Brain Tumor MR Images

    PubMed Central

    Deng, He; Deng, Wankai; Sun, Xianping; Ye, Chaohui; Zhou, Xin

    2016-01-01

    Image enhancement techniques are able to improve the contrast and visual quality of magnetic resonance (MR) images. However, conventional methods cannot make up some deficiencies encountered by respective brain tumor MR imaging modes. In this paper, we propose an adaptive intuitionistic fuzzy sets-based scheme, called as AIFE, which takes information provided from different MR acquisitions and tries to enhance the normal and abnormal structural regions of the brain while displaying the enhanced results as a single image. The AIFE scheme firstly separates an input image into several sub images, then divides each sub image into object and background areas. After that, different novel fuzzification, hyperbolization and defuzzification operations are implemented on each object/background area, and finally an enhanced result is achieved via nonlinear fusion operators. The fuzzy implementations can be processed in parallel. Real data experiments demonstrate that the AIFE scheme is not only effectively useful to have information from images acquired with different MR sequences fused in a single image, but also has better enhancement performance when compared to conventional baseline algorithms. This indicates that the proposed AIFE scheme has potential for improving the detection and diagnosis of brain tumors. PMID:27786240

  14. Potential of high-Z contrast agents in clinical contrast-enhanced computed tomography

    SciTech Connect

    Nowak, Tristan; Hupfer, Martin; Brauweiler, Robert; Eisa, Fabian; Kalender, Willi A.

    2011-12-15

    Purpose: Currently, only iodine- and barium-based contrast media (CM) are used in clinical contrast-enhanced computed tomography (CE-CT). High-Z metals would produce a higher contrast at equal mass density for the x-ray spectra used in clinical CT. Using such materials might allow for significant dose reductions in CE-CT. The purpose of this study was to quantify the potential for dose reduction when using CM based on heavy metals. Methods: The contrast-to-noise ratio weighted by dose (CNRD) was determined as a function of scan protocol by means of measurements and simulations on a clinical CT scanner. For simulations, water cylinders with diameters 160, 320, 480, and 640 mm were used to cover a broad range of patient sizes. Measurements were conducted with 160 and 320 mm water-equivalent plastic cylinders. A central bore of 13 mm diameter was present in all phantoms. The tube voltage was varied from 80 to 140 kV for measurements and from 60 to 180 kV for simulations. Additional tin filtration of thicknesses 0.4, 0.8, and 1.2 mm was applied in the simulation to evaluate a range of spectral hardness. The bore was filled with a mixture of water and 10 mg/ml of pure iodine, holmium, gadolinium, ytterbium, osmium, tungsten, gold, and bismuth for the simulations and with aqueous solutions of ytterbium, tungsten, gold, and bismuth salts as well as Iopromid containing 10 mg/ml of the pure materials for the measurements. CNRDs were compared to iodine at phantom size-dependent reference voltages for all high-Z materials and the resulting dose reduction was calculated for equal contrast-to-noise ratio. Results: Dose reduction potentials strongly depended on phantom size, spectral hardness, and tube voltage. Depending on the added filtration, a dose reduction of 19%-60% could be reached at 80 kV with gadolinium for the 160 mm phantom, 52%-69% at 100 kV with holmium for the 320 mm phantom, 62%-78% with 120 kV for hafnium and the 480 mm phantom and 74%-86% with 140 kV for gold

  15. Cerebellar dermoid cyst with contrast enhancement mural nodule: case report.

    PubMed

    Morina, Arsim; Kelmendi, Fatos; Morina, Qamile; Morina, Dukagjin

    2014-12-01

    Typical dermoid cysts are well-circumscribed fat-density masses with no associated contrast enhancement; rarely, they may appear hyperattenuating on CT scan. CT hyperattenuating dermoid cyst (CHADC) is very uncommon, with only nine case reports in the literature update, which occurs exclusively in the posterior fossa. CHADC with mural nodule is extremely rare and, to the best of our knowledge, only two cases have been documented previously in the literature. A 49-year-old farmer had a 2-month history of occipital headaches, which were not suggestive of raised intracranial pressure. During the last month, he experienced loss of balance, frequent falls, anorexia and loss of weight. Magnetic resonance imaging (MRI) showed a huge mass from the tentorium to the foramen occipitale magnum with obliteration of the fourth ventricle; the lesion was well circumscribed. We completely removed the tumor and postoperative MRI showed no residual tumor. Epidermoid tumors with enhancing mural nodule on MRI and with hyperattenuating lesion on CT are extremely rare. Dermoid cysts are never associated with edema and extremely rarely cause obstructive hydrocephalus. MRI investigations are mandatory to diagnose these cases. The best curative treatment is total removal of the lesion. PMID:25868317

  16. Cerebellar dermoid cyst with contrast enhancement mural nodule: case report.

    PubMed

    Morina, Arsim; Kelmendi, Fatos; Morina, Qamile; Morina, Dukagjin

    2014-12-01

    Typical dermoid cysts are well-circumscribed fat-density masses with no associated contrast enhancement; rarely, they may appear hyperattenuating on CT scan. CT hyperattenuating dermoid cyst (CHADC) is very uncommon, with only nine case reports in the literature update, which occurs exclusively in the posterior fossa. CHADC with mural nodule is extremely rare and, to the best of our knowledge, only two cases have been documented previously in the literature. A 49-year-old farmer had a 2-month history of occipital headaches, which were not suggestive of raised intracranial pressure. During the last month, he experienced loss of balance, frequent falls, anorexia and loss of weight. Magnetic resonance imaging (MRI) showed a huge mass from the tentorium to the foramen occipitale magnum with obliteration of the fourth ventricle; the lesion was well circumscribed. We completely removed the tumor and postoperative MRI showed no residual tumor. Epidermoid tumors with enhancing mural nodule on MRI and with hyperattenuating lesion on CT are extremely rare. Dermoid cysts are never associated with edema and extremely rarely cause obstructive hydrocephalus. MRI investigations are mandatory to diagnose these cases. The best curative treatment is total removal of the lesion.

  17. Evidence for a common motion mechanism of luminance-modulated and contrast-modulated patterns: selective adaptation.

    PubMed

    Turano, K

    1991-01-01

    Selective adaptation effects were measured with contrast-modulated patterns and sine-wave gratings in order to determine the extent to which the two patterns are processed by common mechanisms. Direction-specific adaptation effects were measured for a contrast-modulated adapting pattern and a test pattern. The contrast-modulated adapting pattern was composed of a sine-wave grating of 8 cycles deg-1 whose contrast was spatially modulated by a sinusoid of 1 cycle deg-1 at one of four levels: 100%, 60%, 30%, or 0%. The results showed that contrast-modulation thresholds for contrast-modulated gratings were raised by 0.3 to 0.5 log units following adaptation to a contrast-modulated grating moving in the same direction as the test pattern, relative to thresholds obtained following adaptation to a contrast-modulated grafting moving in the opposite direction. Cross-adaptation effects were also measured with a sine-wave adapting pattern and a contrast-modulated test pattern. The sine-wave adapting pattern was a sine-wave grating of 1 cycle deg-1 whose contrast was set to one of three levels: 16.4%, 1.25%, or 0%. The contrast-modulated test pattern was a sine-wave grating of 8 cycles deg-1 whose contrast was modulated by a sinusoid of 1 cycle deg-1. The results revealed that contrast-modulation thresholds for contrast-modulated gratings were raised by approximately 0.25 log units following adaptation to moving sine-wave gratings, relative to thresholds obtained following adaptation to a uniform field. Cross-adaptation effects were also obtained with a contrast-modulated adapting pattern and a sine-wave test pattern. The results support the view that signals generated from luminance-domain stimuli and from contrast-domain stimuli are processed by a common motion mechanism.

  18. Dynamic Contrast-Enhanced MRI of Cervical Cancers: Temporal Percentile Screening of Contrast Enhancement Identifies Parameters for Prediction of Chemoradioresistance

    SciTech Connect

    Andersen, Erlend K.F.; Hole, Knut Hakon; Lund, Kjersti V.; Sundfor, Kolbein; Kristensen, Gunnar B.; Lyng, Heidi; Malinen, Eirik

    2012-03-01

    Purpose: To systematically screen the tumor contrast enhancement of locally advanced cervical cancers to assess the prognostic value of two descriptive parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Methods and Materials: This study included a prospectively collected cohort of 81 patients who underwent DCE-MRI with gadopentetate dimeglumine before chemoradiotherapy. The following descriptive DCE-MRI parameters were extracted voxel by voxel and presented as histograms for each time point in the dynamic series: normalized relative signal increase (nRSI) and normalized area under the curve (nAUC). The first to 100th percentiles of the histograms were included in a log-rank survival test, resulting in p value and relative risk maps of all percentile-time intervals for each DCE-MRI parameter. The maps were used to evaluate the robustness of the individual percentile-time pairs and to construct prognostic parameters. Clinical endpoints were locoregional control and progression-free survival. The study was approved by the institutional ethics committee. Results: The p value maps of nRSI and nAUC showed a large continuous region of percentile-time pairs that were significantly associated with locoregional control (p < 0.05). These parameters had prognostic impact independent of tumor stage, volume, and lymph node status on multivariate analysis. Only a small percentile-time interval of nRSI was associated with progression-free survival. Conclusions: The percentile-time screening identified DCE-MRI parameters that predict long-term locoregional control after chemoradiotherapy of cervical cancer.

  19. Adaptation with a stabilized retinal image: effect of luminance and contrast.

    PubMed

    Olson, J D; Tulunay-Keesey, U; Saleh, B E

    1994-11-01

    The addition of a uniform increment of luminance (L) to a faded retinally-stabilized target results in the subjective reappearance of the image with contrast opposite to that of the target. This phenomenon, called apparent phase reversal (APR), reveals a nonlinear gain mechanism in the adaptation process. The magnitude of the threshold increment to elicit APR (Lapr) is a measure of the state of stabilized adaptation. In the experiments reported here, Lapr was studied as a function of background luminance (Lo) and contrast (m) of the adapting stimulus. It was found that Lapr increases with increasing Lo, but does not depend on m. The data are analyzed within the context of a previously proposed model of stabilized image fading consisting of a multiplicative inverse gain followed by a subtractive process. It was found that the addition of a contrast processing stage was required to account for the relationship between Lapr and m.

  20. Ultrafast 3D spin-echo acquisition improves Gadolinium-enhanced MRI signal contrast enhancement

    PubMed Central

    Han, S. H.; Cho, F. H.; Song, Y. K.; Paulsen, J.; Song, Y. Q.; Kim, Y. R.; Kim, J. K.; Cho, G.; Cho, H.

    2014-01-01

    Long scan times of 3D volumetric MR acquisitions usually necessitate ultrafast in vivo gradient-echo acquisitions, which are intrinsically susceptible to magnetic field inhomogeneities. This is especially problematic for contrast-enhanced (CE)-MRI applications, where non-negligible T2* effect of contrast agent deteriorates the positive signal contrast and limits the available range of MR acquisition parameters and injection doses. To overcome these shortcomings without degrading temporal resolution, ultrafast spin-echo acquisitions were implemented. Specifically, a multiplicative acceleration factor from multiple spin echoes (×32) and compressed sensing (CS) sampling (×8) allowed highly-accelerated 3D Multiple-Modulation-Multiple-Echo (MMME) acquisition. At the same time, the CE-MRI of kidney with Gd-DOTA showed significantly improved signal enhancement for CS-MMME acquisitions (×7) over that of corresponding FLASH acquisitions (×2). Increased positive contrast enhancement and highly accelerated acquisition of extended volume with reduced RF irradiations will be beneficial for oncological and nephrological applications, in which the accurate in vivo 3D quantification of contrast agent concentration is necessary with high temporal resolution. PMID:24863102

  1. Spike-Triggered Covariance Analysis Reveals Phenomenological Diversity of Contrast Adaptation in the Retina

    PubMed Central

    Liu, Jian K.; Gollisch, Tim

    2015-01-01

    When visual contrast changes, retinal ganglion cells adapt by adjusting their sensitivity as well as their temporal filtering characteristics. The latter has classically been described by contrast-induced gain changes that depend on temporal frequency. Here, we explored a new perspective on contrast-induced changes in temporal filtering by using spike-triggered covariance analysis to extract multiple parallel temporal filters for individual ganglion cells. Based on multielectrode-array recordings from ganglion cells in the isolated salamander retina, we found that contrast adaptation of temporal filtering can largely be captured by contrast-invariant sets of filters with contrast-dependent weights. Moreover, differences among the ganglion cells in the filter sets and their contrast-dependent contributions allowed us to phenomenologically distinguish three types of filter changes. The first type is characterized by newly emerging features at higher contrast, which can be reproduced by computational models that contain response-triggered gain-control mechanisms. The second type follows from stronger adaptation in the Off pathway as compared to the On pathway in On-Off-type ganglion cells. Finally, we found that, in a subset of neurons, contrast-induced filter changes are governed by particularly strong spike-timing dynamics, in particular by pronounced stimulus-dependent latency shifts that can be observed in these cells. Together, our results show that the contrast dependence of temporal filtering in retinal ganglion cells has a multifaceted phenomenology and that a multi-filter analysis can provide a useful basis for capturing the underlying signal-processing dynamics. PMID:26230927

  2. Adaptive line enhancers for fast acquisition

    NASA Technical Reports Server (NTRS)

    Yeh, H.-G.; Nguyen, T. M.

    1994-01-01

    Three adaptive line enhancer (ALE) algorithms and architectures - namely, conventional ALE, ALE with double filtering, and ALE with coherent accumulation - are investigated for fast carrier acquisition in the time domain. The advantages of these algorithms are their simplicity, flexibility, robustness, and applicability to general situations including the Earth-to-space uplink carrier acquisition and tracking of the spacecraft. In the acquisition mode, these algorithms act as bandpass filters; hence, the carrier-to-noise ratio (CNR) is improved for fast acquisition. In the tracking mode, these algorithms simply act as lowpass filters to improve signal-to-noise ratio; hence, better tracking performance is obtained. It is not necessary to have a priori knowledge of the received signal parameters, such as CNR, Doppler, and carrier sweeping rate. The implementation of these algorithms is in the time domain (as opposed to the frequency domain, such as the fast Fourier transform (FFT)). The carrier frequency estimation can be updated in real time at each time sample (as opposed to the batch processing of the FFT). The carrier frequency to be acquired can be time varying, and the noise can be non-Gaussian, nonstationary, and colored.

  3. An adaptive image enhancement technique by combining cuckoo search and particle swarm optimization algorithm.

    PubMed

    Ye, Zhiwei; Wang, Mingwei; Hu, Zhengbing; Liu, Wei

    2015-01-01

    Image enhancement is an important procedure of image processing and analysis. This paper presents a new technique using a modified measure and blending of cuckoo search and particle swarm optimization (CS-PSO) for low contrast images to enhance image adaptively. In this way, contrast enhancement is obtained by global transformation of the input intensities; it employs incomplete Beta function as the transformation function and a novel criterion for measuring image quality considering three factors which are threshold, entropy value, and gray-level probability density of the image. The enhancement process is a nonlinear optimization problem with several constraints. CS-PSO is utilized to maximize the objective fitness criterion in order to enhance the contrast and detail in an image by adapting the parameters of a novel extension to a local enhancement technique. The performance of the proposed method has been compared with other existing techniques such as linear contrast stretching, histogram equalization, and evolutionary computing based image enhancement methods like backtracking search algorithm, differential search algorithm, genetic algorithm, and particle swarm optimization in terms of processing time and image quality. Experimental results demonstrate that the proposed method is robust and adaptive and exhibits the better performance than other methods involved in the paper. PMID:25784928

  4. An adaptive image enhancement technique by combining cuckoo search and particle swarm optimization algorithm.

    PubMed

    Ye, Zhiwei; Wang, Mingwei; Hu, Zhengbing; Liu, Wei

    2015-01-01

    Image enhancement is an important procedure of image processing and analysis. This paper presents a new technique using a modified measure and blending of cuckoo search and particle swarm optimization (CS-PSO) for low contrast images to enhance image adaptively. In this way, contrast enhancement is obtained by global transformation of the input intensities; it employs incomplete Beta function as the transformation function and a novel criterion for measuring image quality considering three factors which are threshold, entropy value, and gray-level probability density of the image. The enhancement process is a nonlinear optimization problem with several constraints. CS-PSO is utilized to maximize the objective fitness criterion in order to enhance the contrast and detail in an image by adapting the parameters of a novel extension to a local enhancement technique. The performance of the proposed method has been compared with other existing techniques such as linear contrast stretching, histogram equalization, and evolutionary computing based image enhancement methods like backtracking search algorithm, differential search algorithm, genetic algorithm, and particle swarm optimization in terms of processing time and image quality. Experimental results demonstrate that the proposed method is robust and adaptive and exhibits the better performance than other methods involved in the paper.

  5. An Adaptive Image Enhancement Technique by Combining Cuckoo Search and Particle Swarm Optimization Algorithm

    PubMed Central

    Ye, Zhiwei; Wang, Mingwei; Hu, Zhengbing; Liu, Wei

    2015-01-01

    Image enhancement is an important procedure of image processing and analysis. This paper presents a new technique using a modified measure and blending of cuckoo search and particle swarm optimization (CS-PSO) for low contrast images to enhance image adaptively. In this way, contrast enhancement is obtained by global transformation of the input intensities; it employs incomplete Beta function as the transformation function and a novel criterion for measuring image quality considering three factors which are threshold, entropy value, and gray-level probability density of the image. The enhancement process is a nonlinear optimization problem with several constraints. CS-PSO is utilized to maximize the objective fitness criterion in order to enhance the contrast and detail in an image by adapting the parameters of a novel extension to a local enhancement technique. The performance of the proposed method has been compared with other existing techniques such as linear contrast stretching, histogram equalization, and evolutionary computing based image enhancement methods like backtracking search algorithm, differential search algorithm, genetic algorithm, and particle swarm optimization in terms of processing time and image quality. Experimental results demonstrate that the proposed method is robust and adaptive and exhibits the better performance than other methods involved in the paper. PMID:25784928

  6. Dynamic Contrast-Enhanced CT in Patients with Pancreatic Cancer

    PubMed Central

    Eriksen, Rie Ø.; Strauch, Louise S.; Sandgaard, Michael; Kristensen, Thomas S.; Nielsen, Michael B.; Lauridsen, Carsten A.

    2016-01-01

    The aim of this systematic review is to provide an overview of the use of Dynamic Contrast-enhanced Computed Tomography (DCE-CT) in patients with pancreatic cancer. This study was composed according to the PRISMA guidelines 2009. The literature search was conducted in PubMed, Cochrane Library, EMBASE, and Web of Science databases to identify all relevant publications. The QUADAS-2 tool was implemented to assess the risk of bias and applicability concerns of each included study. The initial literature search yielded 483 publications. Thirteen articles were included. Articles were categorized into three groups: nine articles concerning primary diagnosis or staging, one article about tumor response to treatment, and three articles regarding scan techniques. In exocrine pancreatic tumors, measurements of blood flow in eight studies and blood volume in seven studies were significantly lower in tumor tissue, compared with measurements in pancreatic tissue outside of tumor, or normal pancreatic tissue in control groups of healthy volunteers. The studies were heterogeneous in the number of patients enrolled and scan protocols. Perfusion parameters measured and analyzed by DCE-CT might be useful in the investigation of characteristic vascular patterns of exocrine pancreatic tumors. Further clinical studies are desired for investigating the potential of DCE-CT in pancreatic tumors. PMID:27608045

  7. Dynamic Contrast-Enhanced CT in Patients with Pancreatic Cancer.

    PubMed

    Eriksen, Rie Ø; Strauch, Louise S; Sandgaard, Michael; Kristensen, Thomas S; Nielsen, Michael B; Lauridsen, Carsten A

    2016-01-01

    The aim of this systematic review is to provide an overview of the use of Dynamic Contrast-enhanced Computed Tomography (DCE-CT) in patients with pancreatic cancer. This study was composed according to the PRISMA guidelines 2009. The literature search was conducted in PubMed, Cochrane Library, EMBASE, and Web of Science databases to identify all relevant publications. The QUADAS-2 tool was implemented to assess the risk of bias and applicability concerns of each included study. The initial literature search yielded 483 publications. Thirteen articles were included. Articles were categorized into three groups: nine articles concerning primary diagnosis or staging, one article about tumor response to treatment, and three articles regarding scan techniques. In exocrine pancreatic tumors, measurements of blood flow in eight studies and blood volume in seven studies were significantly lower in tumor tissue, compared with measurements in pancreatic tissue outside of tumor, or normal pancreatic tissue in control groups of healthy volunteers. The studies were heterogeneous in the number of patients enrolled and scan protocols. Perfusion parameters measured and analyzed by DCE-CT might be useful in the investigation of characteristic vascular patterns of exocrine pancreatic tumors. Further clinical studies are desired for investigating the potential of DCE-CT in pancreatic tumors. PMID:27608045

  8. Uncertainty estimation in dynamic contrast-enhanced MRI.

    PubMed

    Garpebring, Anders; Brynolfsson, Patrik; Yu, Jun; Wirestam, Ronnie; Johansson, Adam; Asklund, Thomas; Karlsson, Mikael

    2013-04-01

    Using dynamic contrast-enhanced MRI (DCE-MRI), it is possible to estimate pharmacokinetic (PK) parameters that convey information about physiological properties, e.g., in tumors. In DCE-MRI, errors propagate in a nontrivial way to the PK parameters. We propose a method based on multivariate linear error propagation to calculate uncertainty maps for the PK parameters. Uncertainties in the PK parameters were investigated for the modified Kety model. The method was evaluated with Monte Carlo simulations and exemplified with in vivo brain tumor data. PK parameter uncertainties due to noise in dynamic data were accurately estimated. Noise with standard deviation up to 15% in the baseline signal and the baseline T1 map gave estimated uncertainties in good agreement with the Monte Carlo simulations. Good agreement was also found for up to 15% errors in the arterial input function amplitude. The method was less accurate for errors in the bolus arrival time with disagreements of 23%, 32%, and 29% for K(trans) , ve , and vp , respectively, when the standard deviation of the bolus arrival time error was 5.3 s. In conclusion, the proposed method provides efficient means for calculation of uncertainty maps, and it was applicable to a wide range of sources of uncertainty.

  9. Visual enhancement of unmixed multispectral imagery using adaptive smoothing

    USGS Publications Warehouse

    Lemeshewsky, G.P.; Rahman, Z.-U.; Schowengerdt, R.A.; Reichenbach, S.E.

    2004-01-01

    Adaptive smoothing (AS) has been previously proposed as a method to smooth uniform regions of an image, retain contrast edges, and enhance edge boundaries. The method is an implementation of the anisotropic diffusion process which results in a gray scale image. This paper discusses modifications to the AS method for application to multi-band data which results in a color segmented image. The process was used to visually enhance the three most distinct abundance fraction images produced by the Lagrange constraint neural network learning-based unmixing of Landsat 7 Enhanced Thematic Mapper Plus multispectral sensor data. A mutual information-based method was applied to select the three most distinct fraction images for subsequent visualization as a red, green, and blue composite. A reported image restoration technique (partial restoration) was applied to the multispectral data to reduce unmixing error, although evaluation of the performance of this technique was beyond the scope of this paper. The modified smoothing process resulted in a color segmented image with homogeneous regions separated by sharpened, coregistered multiband edges. There was improved class separation with the segmented image, which has importance to subsequent operations involving data classification.

  10. Dynamic contrast-enhanced MRI evaluation of cerebral cavernous malformations.

    PubMed

    Hart, Blaine L; Taheri, Saeid; Rosenberg, Gary A; Morrison, Leslie A

    2013-10-01

    The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4 min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects. PMID:24323376

  11. Dynamic Contrast-Enhanced MRI Evaluation of Cerebral Cavernous Malformations

    PubMed Central

    Hart, B. L.; Taheri, S.; Rosenberg, G. A.; Morrison, L. A.

    2013-01-01

    The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22–76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E–6 to 9.63E–4 min−1, mean 3.55E–4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E–4, not statistically different from mean WM Ki of 1.47E–4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects. PMID:24323376

  12. Dynamic contrast-enhanced MRI evaluation of cerebral cavernous malformations.

    PubMed

    Hart, Blaine L; Taheri, Saeid; Rosenberg, Gary A; Morrison, Leslie A

    2013-10-01

    The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4 min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects.

  13. Dynamic contrast-enhanced MRI for prostate cancer localization.

    PubMed

    Jackson, A S N; Reinsberg, S A; Sohaib, S A; Charles-Edwards, E M; Jhavar, S; Christmas, T J; Thompson, A C; Bailey, M J; Corbishley, C M; Fisher, C; Leach, M O; Dearnaley, D P

    2009-02-01

    Radiotherapy dose escalation improves tumour control in prostate cancer but with increased toxicity. Boosting focal tumour only may allow dose escalation with acceptable toxicity. Intensity-modulated radiotherapy can deliver this, but visualization of the tumour remains limiting. CT or conventional MRI techniques are poor at localizing tumour, but dynamic contrast-enhanced MRI (DCE-MRI) may be superior. 18 patients with prostate cancer had T(2) weighted (T2W) and DCE-MRI prior to prostatectomy. The prostate was sectioned meticulously so as to achieve accurate correlation between imaging and pathology. The accuracy of DCE-MRI for cancer detection was calculated by a pixel-by-pixel correlation of quantitative DCE-MRI parameter maps and pathology. In addition, a radiologist interpreted the DCE-MRI and T2W images. The location of tumour on imaging was compared with histology, and the accuracy of DCE-MRI and T2W images was then compared. Pixel-by-pixel comparison of quantitative parameter maps showed a significant difference between the benign peripheral zone and tumour for the parameters K(trans), v(e) and k(ep). Calculation of areas under the receiver operating characteristic curve showed that the pharmacokinetic parameters were only "fair" discriminators between cancer and benign gland. Interpretation of DCE-MRI and T2W images by a radiologist showed DCE-MRI to be more sensitive than T2W images for tumour localization (50% vs 21%; p = 0.006) and similarly specific (85% vs 81%; p = 0.593). The superior sensitivity of DCE-MRI compared with T2W images, together with its high specificity, is arguably sufficient for its use in guiding radiotherapy boosts in prostate cancer.

  14. Enhancement of chromatic contrast increases predation risk for striped butterflies

    PubMed Central

    Stobbe, Nina; Schaefer, H. Martin

    2008-01-01

    Many prey species have evolved defensive colour patterns to avoid attacks. One type of camouflage, disruptive coloration, relies on contrasting patterns that hinder predators' ability to recognize an object. While high contrasts are used to facilitate detection in many visual communication systems, they are thought to provide misleading information about prey appearance in disruptive patterns. A fundamental tenet in disruptive coloration theory is the principle of ‘maximum disruptive contrast’, i.e. disruptive patterns are more effective when higher contrasts are involved. We tested this principle in highly contrasting stripes that have often been described as disruptive patterns. Varying the strength of chromatic contrast between stripes and adjacent pattern elements in artificial butterflies, we found a strong negative correlation between survival probability and chromatic contrast strength. We conclude that too high a contrast leads to increased conspicuousness rather than to effective camouflage. However, artificial butterflies that sported contrasts similar to those of the model species Limenitis camilla survived equally well as background-matching butterflies without these stripes. Contrasting stripes do thus not necessarily increase predation rates. This result may provide new insights into the design and characteristics of a range of colour patterns such as sexual, mimetic and aposematic signals. PMID:18381256

  15. Adaptation strategies to climate change and climate variability: a comparative study between seven contrasting river basins.

    NASA Astrophysics Data System (ADS)

    Droogers, P.

    2003-04-01

    Climate change and climate variability is and will have a tremendous impact on hydrology and consequently on food security and environmental protection. From the four major components in climate change and climate variability studies, projection, mitigation, impact and adaptation, has the latter so far received less attention than the other three. An international collaboration of ten institutions is comparing adaptation strategies between contrasting basins ranging from wet to dry and from poor to rich. Basins included are: Mekong, Walawe (Sri Lanka), Rhine, Sacramento, Syr Darya, Volta, and Zayandeh (Iran). Simulation models at basin and field scale have been set up and possible adaptation strategies are explored by these models. Preliminary results indicate that appropriate adaptation strategies are different between these seven contrasting basins. It is also clear that these adaptation strategies should focus on increased variability rather than on the overall change of the mean. The focus was hereby not only on an increase in variation but especially on the number of successive dry and wet years. Results show that the studies on these adaptation strategies could not be performed only at one scale, but that a combination of field scale as well as basin scale analysis is essential.

  16. Contrast gain, signal-to-noise ratio, and linearity in light-adapted blowfly photoreceptors

    PubMed Central

    1994-01-01

    Response properties of short-type (R1-6) photoreceptors of the blowfly (Calliphora vicina) were investigated with intracellular recordings using repeated sequences of pseudorandomly modulated light contrast stimuli at adapting backgrounds covering 5 log intensity units. The resulting voltage responses were used to determine the effects of adaptational regulation on signal-to-noise ratios (SNR), signal induced noise, contrast gain, linearity and the dead time in phototransduction. In light adaptation the SNR of the photoreceptors improved more than 100-fold due to (a) increased photoreceptor voltage responses to a contrast stimulus and (b) reduction of voltage noise at high intensity backgrounds. In the frequency domain the SNR was attenuated in low frequencies with an increase in the middle and high frequency ranges. A pseudorandom contrast stimulus by itself did not produce any additional noise. The contrast gain of the photoreceptor frequency responses increased with mean illumination and the gain was best fitted with a model consisting of two second order and one double pole of first order. The coherence function (a normalized measure of linearity and SNR) of the frequency responses demonstrated that the photoreceptors responded linearly (from 1 to 150 Hz) to the contrast stimuli even under fairly dim conditions. The theoretically derived and the recorded phase functions were used to calculate phototransduction dead time, which decreased in light adaptation from approximately 5-2.5 ms. This analysis suggests that the ability of fly photoreceptors to maintain linear performance under dynamic stimulation conditions results from the high early gain followed by delayed compressive feed-back mechanisms. PMID:7807062

  17. Turning up the contrast: self-enhancement motives prompt egocentric contrast effects in social judgments.

    PubMed

    Beauregard, K S; Dunning, D

    1998-03-01

    Contrast effects occur when people judge the behavior and attitudes of others relative to their own. We tested a motivational account suggesting that these effects arise because people tailor their judgments of others to affirm their own self-worth. Consistent with that interpretation, participants displayed more egocentric contrast in their judgments of another person's intelligence (i.e., their evaluation of his score on the Scholastic Aptitude Test was more negatively related to their own score) after their self-esteem was threatened than after it was bolstered (Studies 1 and 2). High-self-esteem individuals displayed more judgmental contrast overall than did their low-esteem counterparts (Study 2). Strongly pro-choice participants whose esteem was threatened also displayed more contrast in their judgments of another person's attitude on abortion, relative to esteem-bolstered participants (Study 3). Discussion centers on the implications of these findings for theory on social comparison, self-affirmation, and social judgment. PMID:9523408

  18. Contrast enhanced cartilage imaging: Comparison of ionic and non-ionic contrast agents.

    PubMed

    Wiener, Edzard; Woertler, Klaus; Weirich, Gregor; Rummeny, Ernst J; Settles, Marcus

    2007-07-01

    Our objective was to compare relaxation effects, dynamics and spatial distributions of ionic and non-ionic contrast agents in articular cartilage at concentrations typically used for direct MR arthrography at 1.5T. Dynamic MR-studies over 11h were performed in 15 bovine patella specimens. For each of the contrast agents gadopentetate dimeglumine, gadobenate dimeglumine, gadoteridol and mangafodipir trinatrium three patellae were placed in 2.5mmol/L contrast solution. Simultaneous measurements of T(1) and T(2) were performed every 30min using a high-spatial-resolution "MIX"-sequence. T(1), T(2) and DeltaR(1), DeltaR(2) profile plots across cartilage thickness were calculated to demonstrate the spatial and temporal distributions. The charge is one of the main factors which controls the amount of the contrast media diffusing into intact cartilage, but independent of the charge, the spatial distribution across cartilage thickness remains highly inhomogeneous even after 11h of diffusion. The absolute DeltaR(2)-effect in cartilage is at least as large as the DeltaR(1)-effect for all contrast agents. Maximum changes were 5-12s(-1) for DeltaR(1) and 8-15s(-1) for DeltaR(2). This study indicates that for morphologically intact cartilage only the amount of contrast agents within cartilage is determined by the charge but not the spatial distribution across cartilage thickness. In addition, DeltaR(2) can be considered for quantification of contrast agent concentrations, since it is of the same magnitude and less time consuming to measure than DeltaR(1).

  19. A hierarchical Bayesian approach to adaptive vision testing: A case study with the contrast sensitivity function

    PubMed Central

    Gu, Hairong; Kim, Woojae; Hou, Fang; Lesmes, Luis Andres; Pitt, Mark A.; Lu, Zhong-Lin; Myung, Jay I.

    2016-01-01

    Measurement efficiency is of concern when a large number of observations are required to obtain reliable estimates for parametric models of vision. The standard entropy-based Bayesian adaptive testing procedures addressed the issue by selecting the most informative stimulus in sequential experimental trials. Noninformative, diffuse priors were commonly used in those tests. Hierarchical adaptive design optimization (HADO; Kim, Pitt, Lu, Steyvers, & Myung, 2014) further improves the efficiency of the standard Bayesian adaptive testing procedures by constructing an informative prior using data from observers who have already participated in the experiment. The present study represents an empirical validation of HADO in estimating the human contrast sensitivity function. The results show that HADO significantly improves the accuracy and precision of parameter estimates, and therefore requires many fewer observations to obtain reliable inference about contrast sensitivity, compared to the method of quick contrast sensitivity function (Lesmes, Lu, Baek, & Albright, 2010), which uses the standard Bayesian procedure. The improvement with HADO was maintained even when the prior was constructed from heterogeneous populations or a relatively small number of observers. These results of this case study support the conclusion that HADO can be used in Bayesian adaptive testing by replacing noninformative, diffuse priors with statistically justified informative priors without introducing unwanted bias. PMID:27105061

  20. PERIPATELLAR SYNOVITIS: COMPARISON BETWEEN NON-CONTRAST-ENHANCED AND CONTRAST-ENHANCED MRI AND ASSOCIATION WITH PAIN. THE MOST STUDY

    PubMed Central

    Crema, Michel D.; Felson, David T.; Roemer, Frank W.; Niu, Jingbo; Marra, Monica D.; Zhang, Yuqing; Lynch, John A.; El-Khoury, Georges Y.; Lewis, Cora E.; Guermazi, Ali

    2013-01-01

    Purpose To assess the diagnostic performance of signal changes in Hoffa's fat pad (HFP) assessed on non-contrast-enhanced (CE) MRI in detecting synovitis, and the association of pain with signal changes in Hoffa’s fat pad on non-CE MRI and peripatellar synovial thickness on CE MRI. Methods The Multicenter Osteoarthritis (MOST) Study is an observational study of individuals who have or are at high risk for knee OA. All subjects with available non-CE and CE MRIs were included. Signal changes in HFP were scored from 0 to 3 in 2 regions using non-CE MRI. Synovial thickness was scored from 0 to 2 on CE MRI in 5 peripatellar regions. Sensitivity, specificity and accuracy of HFP signal changes were calculated considering synovial thickness on CE MRI as the reference standard. We used logistic regression to assess the associations of HFP changes (non-CE MRI) and synovial thickness (CE MRI) with pain from walking up or down stairs, after adjusting for potential confounders. Results A total of 393 subjects were included. Sensitivity of infrapatellar and intercondylar signal changes in HFP was high (71% and 88%), but specificity was low (55% and 30%). No significant associations were found between HFP changes on non-CE MRI and pain. Grade 2 synovial thickness assessed on CE MRI was significantly associated with pain after adjustments for potential confounders. Conclusion Signal changes in HFP detected on non-CE MRI are a sensitive but non-specific surrogate for the assessment of synovitis. CE MRI identifies associations with pain better than non-CE MRI. PMID:23277189

  1. High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

    SciTech Connect

    Evans, Julia Wilhelmsen

    2006-01-01

    Direct imaging of extrasolar planets is an important, but challenging, next step in planetary science. Most planets identified to date have been detected indirectly--not by emitted or reflected light but through the effect of the planet on the parent star. For example, radial velocity techniques measure the doppler shift in the spectrum of the star produced by the presence of a planet. Indirect techniques only probe about 15% of the orbital parameter space of our solar system. Direct methods would probe new parameter space, and the detected light can be analyzed spectroscopically, providing new information about detected planets. High contrast adaptive optics systems, also known as Extreme Adaptive Optics (ExAO), will require contrasts of between 10-6 and 10-7 at angles of 4-24 λ/D on an 8-m class telescope to image young Jupiter-like planets still warm with the heat of formation. Contrast is defined as the intensity ratio of the dark wings of the image, where a planet might be, to the bright core of the star. Such instruments will be technically challenging, requiring high order adaptive optics with > 2000 actuators and improved diffraction suppression. Contrast is ultimately limited by residual static wavefront errors, so an extrasolar planet imager will require wavefront control with an accuracy of better than 1 nm rms within the low- to mid-spatial frequency range. Laboratory demonstrations are critical to instrument development. The ExAO testbed at the Laboratory for Adaptive Optics was designed with low wavefront error and precision optical metrology, which is used to explore contrast limits and develop the technology needed for an extrasolar planet imager. A state-of-the-art, 1024-actuator micro-electrical-mechanical-systems (MEMS) deformable mirror was installed and characterized to provide active wavefront control and test this novel technology. I present 6.5 x 10-8 contrast measurements with a prolate shaped pupil and

  2. Immature visual neural system in children reflected by contrast sensitivity with adaptive optics correction

    PubMed Central

    Liu, Rong; Zhou, Jiawei; Zhao, Haoxin; Dai, Yun; Zhang, Yudong; Tang, Yong; Zhou, Yifeng

    2014-01-01

    This study aimed to explore the neural development status of the visual system of children (around 8 years old) using contrast sensitivity. We achieved this by eliminating the influence of higher order aberrations (HOAs) with adaptive optics correction. We measured HOAs, modulation transfer functions (MTFs) and contrast sensitivity functions (CSFs) of six children and five adults with both corrected and uncorrected HOAs. We found that when HOAs were corrected, children and adults both showed improvements in MTF and CSF. However, the CSF of children was still lower than the adult level, indicating the difference in contrast sensitivity between groups cannot be explained by differences in optical factors. Further study showed that the difference between the groups also could not be explained by differences in non-visual factors. With these results we concluded that the neural systems underlying vision in children of around 8 years old are still immature in contrast sensitivity. PMID:24732728

  3. Comparing and contrasting observed adaptations in three deltas: the Ganges-Meghna-Brahmaputra, Mahanadi and Volta

    NASA Astrophysics Data System (ADS)

    Nicholls, R. J.; Suckall, N.; Mensah, A.; Mondal, S.; Dey, S.; Hazra, S.

    2015-12-01

    In low and middle-income countries, many deltaic communities directly depend on the natural environment for income and well-being. Current environmental concerns that threaten deltaic communities, such as increasing salinity, sedimentation, erosion and subsidence are likely to be exacerbated by climate change and variability, for example sea-level rise, increased storminess and rising temperatures. Such changes, along with other social and environmental stressors, mean that communities must adapt. This paper outlines findings of a systematic review of the peer-reviewed and grey literature that examines observed adaptations in three deltas of differing sizes in various geographical contexts: the Ganges-Meghna-Brahmaputra in India and Bangladesh, the Mahanadi in India, and the Volta in Ghana. It compares and contrasts various elements of observed adaptations, including who is driving the adaptation, the beneficiaries, barriers to participation and evidence for maladaptation. The predominant drivers of adaptation vary from government (at state level in India and national level in Bangladesh) and NGOs (in Ghana). Autonomous adaptations are not widely reported in the literature from any of the deltas. In all three deltas there is a focus on supporting adaptation in farming rather than fishing; despite the fact that fisheries contribute to local food security as well as national economies. Lack of access to financial, natural, physical and human capital are common barriers to adaptation in all three deltas. Additionally the Indian literature in particular highlights the lack of coordination between different government departments, coupled with an excessively top-down (state-driven) approach to adaptation. Maladaptation is most commonly reported in the literature from Bangladesh, for example, loss of employment of inland fishermen in embanked areas. The paper concludes by highlighting some of the implications of these findings for adaptation policy in deltas.

  4. Die Fledermaus: Regarding Optokinetic Contrast Sensitivity and Light-Adaptation, Chicks Are Mice with Wings

    PubMed Central

    Shi, Qing; Stell, William K.

    2013-01-01

    Background Through adaptation, animals can function visually under an extremely broad range of light intensities. Light adaptation starts in the retina, through shifts in photoreceptor sensitivity and kinetics plus modulation of visual processing in retinal circuits. Although considerable research has been conducted on retinal adaptation in nocturnal species with rod-dominated retinas, such as the mouse, little is known about how cone-dominated avian retinas adapt to changes in mean light intensity. Methodology/Principal Findings We used the optokinetic response to characterize contrast sensitivity (CS) in the chick retina as a function of spatial frequency and temporal frequency at different mean light intensities. We found that: 1) daytime, cone-driven CS was tuned to spatial frequency; 2) nighttime, presumably rod-driven CS was tuned to temporal frequency and spatial frequency; 3) daytime, presumably cone-driven CS at threshold intensity was invariant with temporal and spatial frequency; and 4) daytime photopic CS was invariant with clock time. Conclusion/Significance Light- and dark-adaptational changes in CS were investigated comprehensively for the first time in the cone-dominated retina of an avian, diurnal species. The chick retina, like the mouse retina, adapts by using a “day/night” or “cone/rod” switch in tuning preference during changes in lighting conditions. The chick optokinetic response is an attractive model for noninvasive, behavioral studies of adaptation in retinal circuitry in health and disease. PMID:24098693

  5. Transmission grating stretcher for contrast enhancement of high power lasers.

    PubMed

    Tang, Yunxin; Hooker, Chris; Chekhlov, Oleg; Hawkes, Steve; Collier, John; Rajeev, P P

    2014-12-01

    We propose, for the first time, a transmission grating stretcher for high power lasers and demonstrate its superiority over conventional, reflective gold grating stretchers in terms of pulse temporal quality. We show that, compared to a conventional stretcher with the same stretching factor, the transmission-grating based stretcher yields more than an order of magnitude improvement in the contrast pedestal. We have also quantitatively characterized the roughness of the grating surfaces and estimated its impact on the contrast pedestal.

  6. Extreme Adaptive Optics Testbed: High Contrast Measurements with a MEMS Deformable Mirror

    SciTech Connect

    Evans, J W; Morzinski, K; Reza, L; Severson, S; Poyneer, L; Macintosh, B; Dillon, D; Sommargren, G

    2005-08-16

    ''Extreme'' adaptive optics systems are optimized for ultra-high-contrast applications, such as ground-based extrasolar planet detection. The Extreme Adaptive Optics Testbed at UC Santa Cruz is being used to investigate and develop technologies for high-contrast imaging, especially wavefront control. We use a simple optical design to minimize wavefront error and maximize the experimentally achievable contrast. A phase shifting diffraction interferometer (PSDI) measures wavefront errors with sub-nm precision and accuracy for metrology and wavefront control. Previously, we have demonstrated RMS wavefront errors of <1.5 nm and a contrast of >10{sup 7} over a substantial region using a shaped pupil without a deformable mirror. Current work includes the installation and characterization of a 1024-actuator Micro-Electro-Mechanical-Systems (MEMS) deformable mirror, manufactured by Boston Micro-Machines for active wavefront control. Using the PSDI as the wavefront sensor we have flattened the deformable mirror to <1 nm within the controllable spatial frequencies and measured a contrast in the far field of >10{sup 6}. Consistent flattening required testing and characterization of the individual actuator response, including the effects of dead and low-response actuators. Stability and repeatability of the MEMS devices was also tested. Ultimately this testbed will be used to test all aspects of the system architecture for an extrasolar planet-finding AO system.

  7. Contrast-enhanced optical coherence tomography with picomolar sensitivity for functional in vivo imaging

    NASA Astrophysics Data System (ADS)

    Liba, Orly; Sorelle, Elliott D.; Sen, Debasish; de La Zerda, Adam

    2016-03-01

    Optical Coherence Tomography (OCT) enables real-time imaging of living tissues at cell-scale resolution over millimeters in three dimensions. Despite these advantages, functional biological studies with OCT have been limited by a lack of exogenous contrast agents that can be distinguished from tissue. Here we report an approach to functional OCT imaging that implements custom algorithms to spectrally identify unique contrast agents: large gold nanorods (LGNRs). LGNRs exhibit 110-fold greater spectral signal per particle than conventional GNRs, which enables detection of individual LGNRs in water and concentrations as low as 250 pM in the circulation of living mice. This translates to ~40 particles per imaging voxel in vivo. Unlike previous implementations of OCT spectral detection, the methods described herein adaptively compensate for depth and processing artifacts on a per sample basis. Collectively, these methods enable high-quality noninvasive contrast-enhanced imaging of OCT in living subjects, including detection of tumor microvasculature at twice the depth achievable with conventional OCT. Additionally, multiplexed detection of spectrally-distinct LGNRs was demonstrated to observe discrete patterns of lymphatic drainage and identify individual lymphangions and lymphatic valve functional states. These capabilities provide a powerful platform for molecular imaging and characterization of tissue noninvasively at cellular resolution, called MOZART.

  8. Contrast-enhanced optical coherence tomography with picomolar sensitivity for functional in vivo imaging

    PubMed Central

    Liba, Orly; SoRelle, Elliott D.; Sen, Debasish; de la Zerda, Adam

    2016-01-01

    Optical Coherence Tomography (OCT) enables real-time imaging of living tissues at cell-scale resolution over millimeters in three dimensions. Despite these advantages, functional biological studies with OCT have been limited by a lack of exogenous contrast agents that can be distinguished from tissue. Here we report an approach to functional OCT imaging that implements custom algorithms to spectrally identify unique contrast agents: large gold nanorods (LGNRs). LGNRs exhibit 110-fold greater spectral signal per particle than conventional GNRs, which enables detection of individual LGNRs in water and concentrations as low as 250 pM in the circulation of living mice. This translates to ~40 particles per imaging voxel in vivo. Unlike previous implementations of OCT spectral detection, the methods described herein adaptively compensate for depth and processing artifacts on a per sample basis. Collectively, these methods enable high-quality noninvasive contrast-enhanced imaging of OCT in living subjects, including detection of tumor microvasculature at twice the depth achievable with conventional OCT. Additionally, multiplexed detection of spectrally-distinct LGNRs was demonstrated to observe discrete patterns of lymphatic drainage and identify individual lymphangions and lymphatic valve functional states. These capabilities provide a powerful platform for molecular imaging and characterization of tissue noninvasively at cellular resolution, called MOZART. PMID:26987475

  9. Simple Image Processing Techniques For The Contrast Enhancement Of Real-Time Digital Speckle Pattern Interferometry Fringes

    NASA Astrophysics Data System (ADS)

    Ganesan, A. R.; Kothiyal, M. P.; Sirohi, Rajpal S.

    1989-09-01

    Some simple image processing techniques are suggested that can be used for enhancing the contrast of real-time digital speckle pattern interferometry fringes. The techniques have been developed for the commercial Intellect 100 image processing system interfaced to a PDP-1 1 /23+ microcomputer, but they can be adapted to any commercial image processing system with slight modifications, if necessary, depending on the hardware configuration of the system.

  10. Enhancement of Electrolaryngeal Speech by Adaptive Filtering.

    ERIC Educational Resources Information Center

    Espy-Wilson, Carol Y.; Chari, Venkatesh R.; MacAuslan, Joel M.; Huang, Caroline B.; Walsh, Michael J.

    1998-01-01

    A study tested the quality and intelligibility, as judged by several listeners, of four users' electrolaryngeal speech, with and without filtering to compensate for perceptually objectionable acoustic characteristics. Results indicated that an adaptive filtering technique produced a noticeable improvement in the quality of the Transcutaneous…

  11. 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

    2014-01-01

    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

  12. 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.

  13. 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

  14. Diagnosis of gallbladder diseases by contrast-enhanced phase-inversion harmonic ultrasonography.

    PubMed

    Inoue, Tatsuo; Kitano, Masayuki; Kudo, Masatoshi; Sakamoto, Hiroki; Kawasaki, Toshihiko; Yasuda, Chikao; Maekawa, Kiyoshi

    2007-03-01

    We evaluated the usefulness of contrast-enhanced ultrasonography(US) for detecting and differentiating gallbladder lesions. Contrast-enhanced coded phase-inversion harmonic US was performed on 90 patients with gallbladder abnormalities. After administering Levovist, we observed the gallbladders in real time. Contrast-enhanced coded phase-inversion harmonic ultrasonography was compared with B-mode US and contrast-enhanced computer tomography (CT) with regard to the sensitivity and specificity in depicting the elevated gallbladder lesions. Furthermore, we assessed how the vascular patterns of the elevated gallbladder lesions depicted by contrast-enhanced US correlated with the diagnosis. Contrast-enhanced US efficiently discriminated true lesions from biliary sludge, unlike B-mode US. Consequently, contrast-enhanced US was more specific (100%) than B-mode US (81%), although their sensitivities were similar (98% and 96%, respectively). Contrast-enhanced US was also more sensitive that contrast-enhanced CT (98% versus 79%), although the two methods were equally sensitive (100% versus 95%). We classified the vascular patterns of the abnormalities depicted by contrast-enhanced US in the 90 cases into types 1 to 4, which represent branch-like, heterogeneous, homogeneous, and avascular patterns, respectively. All type 1 and 2 lesions were over 10 mm in size while most (88%) type 3 lesions were 10 mm or less in size. While the majority of carcinomas (86%) were type 1 or 2, three benign lesions also showed these patterns. Thus, the vascular pattern may simply reflect the size of the lesion and therefore its usefulness in diagnosing gallbladder lesions may be limited. Nevertheless, contrast-enhanced US is clearly superior to the other techniques in discriminating biliary sludge from other lesions.

  15. Automatic Characterization of Myocardial Perfusion in Contrast Enhanced MRI

    NASA Astrophysics Data System (ADS)

    Positano, Vincenzo; Santarelli, Maria Filomena; Landini, Luigi

    2003-12-01

    The use of contrast medium in cardiac MRI allows joining the high-resolution anatomical information provided by standard magnetic resonance with functional information obtained by means of the perfusion of contrast agent in myocardial tissues. The current approach to perfusion MRI characterization is the qualitative one, based on visual inspection of images. Moving to quantitative analysis requires extraction of numerical indices of myocardium perfusion by analysis of time/intensity curves related to the area of interest. The main problem in quantitative image sequence analysis is the heart movement, mainly due to patient respiration. We propose an automatic procedure based on image registration, segmentation of the myocardium, and extraction and analysis of time/intensity curves. The procedure requires a minimal user interaction, is robust with respect to the user input, and allows effective characterization of myocardial perfusion. The algorithm was tested on cardiac MR images acquired from voluntaries and in clinical routine.

  16. Concurrent enhancement of percolation and synchronization in adaptive networks.

    PubMed

    Eom, Young-Ho; Boccaletti, Stefano; Caldarelli, Guido

    2016-06-02

    Co-evolutionary adaptive mechanisms are not only ubiquitous in nature, but also beneficial for the functioning of a variety of systems. We here consider an adaptive network of oscillators with a stochastic, fitness-based, rule of connectivity, and show that it self-organizes from fragmented and incoherent states to connected and synchronized ones. The synchronization and percolation are associated to abrupt transitions, and they are concurrently (and significantly) enhanced as compared to the non-adaptive case. Finally we provide evidence that only partial adaptation is sufficient to determine these enhancements. Our study, therefore, indicates that inclusion of simple adaptive mechanisms can efficiently describe some emergent features of networked systems' collective behaviors, and suggests also self-organized ways to control synchronization and percolation in natural and social systems.

  17. Concurrent enhancement of percolation and synchronization in adaptive networks

    PubMed Central

    Eom, Young-Ho; Boccaletti, Stefano; Caldarelli, Guido

    2016-01-01

    Co-evolutionary adaptive mechanisms are not only ubiquitous in nature, but also beneficial for the functioning of a variety of systems. We here consider an adaptive network of oscillators with a stochastic, fitness-based, rule of connectivity, and show that it self-organizes from fragmented and incoherent states to connected and synchronized ones. The synchronization and percolation are associated to abrupt transitions, and they are concurrently (and significantly) enhanced as compared to the non-adaptive case. Finally we provide evidence that only partial adaptation is sufficient to determine these enhancements. Our study, therefore, indicates that inclusion of simple adaptive mechanisms can efficiently describe some emergent features of networked systems’ collective behaviors, and suggests also self-organized ways to control synchronization and percolation in natural and social systems. PMID:27251577

  18. Concurrent enhancement of percolation and synchronization in adaptive networks

    NASA Astrophysics Data System (ADS)

    Eom, Young-Ho; Boccaletti, Stefano; Caldarelli, Guido

    2016-06-01

    Co-evolutionary adaptive mechanisms are not only ubiquitous in nature, but also beneficial for the functioning of a variety of systems. We here consider an adaptive network of oscillators with a stochastic, fitness-based, rule of connectivity, and show that it self-organizes from fragmented and incoherent states to connected and synchronized ones. The synchronization and percolation are associated to abrupt transitions, and they are concurrently (and significantly) enhanced as compared to the non-adaptive case. Finally we provide evidence that only partial adaptation is sufficient to determine these enhancements. Our study, therefore, indicates that inclusion of simple adaptive mechanisms can efficiently describe some emergent features of networked systems’ collective behaviors, and suggests also self-organized ways to control synchronization and percolation in natural and social systems.

  19. Concurrent enhancement of percolation and synchronization in adaptive networks.

    PubMed

    Eom, Young-Ho; Boccaletti, Stefano; Caldarelli, Guido

    2016-01-01

    Co-evolutionary adaptive mechanisms are not only ubiquitous in nature, but also beneficial for the functioning of a variety of systems. We here consider an adaptive network of oscillators with a stochastic, fitness-based, rule of connectivity, and show that it self-organizes from fragmented and incoherent states to connected and synchronized ones. The synchronization and percolation are associated to abrupt transitions, and they are concurrently (and significantly) enhanced as compared to the non-adaptive case. Finally we provide evidence that only partial adaptation is sufficient to determine these enhancements. Our study, therefore, indicates that inclusion of simple adaptive mechanisms can efficiently describe some emergent features of networked systems' collective behaviors, and suggests also self-organized ways to control synchronization and percolation in natural and social systems. PMID:27251577

  20. Contrast-enhanced ultrasound (CEUS) appearance of hepatic myelolipoma.

    PubMed

    Menozzi, Guido; Maccabruni, Valeria; Marini, Giulia; Froio, Elisabetta; Garlassi, Elisa

    2016-03-01

    The case report is a description of a single case of hepatic myelolipoma, a very rare benign hepatic tumor, evaluated with contrast sonography, in a 72-year-old female. It was previously reported as hyperechoic lesions at sonography. CEUS features of the lesion were: homogeneous hyperenhancement in the arterial phase and a slight hyperenhancement in the portal venous phase typical of benign tumors. The case report shows CEUS may help in differential diagnosis between benign and malignant lesions, but only the biopsy of the tumor and the pathological evaluation allows the diagnosis. PMID:26941876

  1. Pulmonary nodule follow-up: be careful with volumetry between contrast enhanced and unenhanced CT

    PubMed Central

    Bülbül, Metin; de Jong, Pim A.

    2016-01-01

    Incident pulmonary nodules are a frequent finding on chest computed tomography (CT) of the lungs requiring follow-up. This case illustrates the importance of taking differences in CT scanning techniques (contrast versus non-contrast enhanced) into account. Comparing nodule size on unenhanced follow-up CT’s with initial contrast-enhanced CT may consequently underestimate growth and mask malignant growth rates as demonstrated by our case report.

  2. Effect of chromatic adaptation on the achromatic locus: the role of contrast, luminance and background color.

    PubMed

    Werner, J S; Walraven, J

    1982-01-01

    Two superposed annular test lights of complementary spectral composition were presented as 60-90' incremental test flashes on 480' steady backgrounds. Two observers adjusted the ratio of the two test lights to maintain an achromatic appearance under conditions of adaptation that varied with respect to background luminance, chromaticity and stimulus contrast. The shift in chromaticity of the achromatic point was in the direction of the chromaticity of the background, while the magnitude of the shift increased as an increasing function of background luminance and as a decreasing function of contrast. These data confirm and extend a model of chromatic adaptation that has the following properties: (1) non-additivity of transient test and steady background fields, in the sense that the background, although physically adding to the test flash, only affects its hue by way of altering the gain of cone pathways; (2) Vos-Walraven cone spectral sensitivities; and (3) adaptation sites in the cone pathways having the same action spectra as Stiles' pi 5, pi 4 and (modified) pi 1 mechanisms, and which generate receptor-specific attenuation factors (von Kries Coefficients) according to Stiles' generalized threshold vs intensity function, zeta (x).

  3. 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.

  4. HIFU Hemostasis of Liver Injuries Enhanced by Ultrasound Contrast Agents

    NASA Astrophysics Data System (ADS)

    Zderic, Vesna; Vaezy, Shahram; Brayman, Andrew A.; Matula, Thomas J.; O'Keefe, Grant E.; Crum, Lawrence A.

    2005-03-01

    Our objective was to investigate whether High-Intensity Focused Ultrasound (HIFU) hemostasis can be achieved faster in the presence of ultrasound contrast agents (UCA). Incisions (3 cm long and 0.5 cm deep) were made in surgically exposed rabbit liver. Optison at a concentration of 0.18 ml/kg was injected into the mesenteric vein, immediately before the incision was made. The HIFU applicator (frequency of 5.5 MHz, and intensity of 3,700 W/cm2) was scanned manually over the incision (at an approximate rate of 1 mm/s) until hemostasis was achieved. The times to complete hemostasis were measured and normalized with the initial blood loss. The hemostasis times were 59±23 s in the presence of Optison and 70±23 s without Optison. The presence of Optison produced a 37% reduction in the normalized hemostasis times (p<0.05). Optison also provided faster (by 34%) formation of the coagulum seal over the lesion. Gross observations showed that the lesion size did not change due to the presence of Optison. Histological analysis showed that lesions consisted of an area of coagulation necrosis in vicinity of the incision, occasionally surrounded by a congestion zone filled with blood. Our results suggest the potential utility of microbubble contrast agents for increasing efficiency of HIFU hemostasis of internal organ injuries.

  5. Novel ways to noninvasively detect inflammation of the myocardium: contrast-enhanced MRI and myocardial contrast echocardiography

    PubMed Central

    van den Brink, M.R.; Geluk, C.A.; Lindner, J.R.; Velthuis, B.K.; Vonken, E.J.; Cramer, M.J.M.

    2003-01-01

    Both contrast-enhanced magnetic resonance imaging (CE-MRI) and myocardial contrast echocardiography (MCE) are promising tools to detect cardiac inflammation. CE-MRI can be used to characterise the location and extent of myocardial inflammation, since areas of abnormal signal enhancement associated with regional wall motion abnormalities reliably indicate areas of active myocarditis. In MCE, chemically composed microbubbles can be visualised by ultrasound and used to determine the status of the cardiac microvasculature. If there is any inflammation the microbubbles will be phagocytosed by neutrophils and monocytes, thus enabling the degree of inflammation to be assessed. These noninvasive techniques may allow early diagnosis and accurate evaluation of myocardial inflammation. ImagesFigure 1Figure 2Figure 3Figure 4 PMID:25696203

  6. Fully automated segmentation of carotid and vertebral arteries from contrast enhanced CTA

    NASA Astrophysics Data System (ADS)

    Cuisenaire, Olivier; Virmani, Sunny; Olszewski, Mark E.; Ardon, Roberto

    2008-03-01

    We propose a method for segmenting and labeling the main head and neck vessels (common, internal, external carotid, vertebral) from a contrast enhanced computed tomography angiography (CTA) volume. First, an initial centerline of each vessel is extracted. Next, the vessels are segmented using 3D active objects initialized using the first step. Finally, the true centerline is identified by smoothly deforming it away from the segmented mask edges using a spline-snake. We focus particularly on the novel initial centerline extraction technique. It uses a locally adaptive front propagation algorithm that attempts to find the optimal path connecting the ends of the vessel, typically from the lowest image of the scan to the Circle of Willis in the brain. It uses a patient adapted anatomical model of the different vessels both to initialize and constrain this fast marching, thus eliminating the need for manual selection of seed points. The method is evaluated using data from multiple regions (USA, India, China, Israel) including a variety of scanners (10, 16, 40, 64-slice; Brilliance CT, Philips Healthcare, Cleveland, OH, USA), contrast agent dose, and image resolution. It is fully successful in over 90% of patients and only misses a single vessel in most remaining cases. We also demonstrate its robustness to metal and dental artifacts and anatomical variability. Total processing time is approximately two minutes with no user interaction, which dramatically improves the workflow over existing clinical software. It also reduces patient dose exposure by obviating the need to acquire an unenhanced scan for bone suppression as this can be done by applying the segmentation masks.

  7. Anisotropic MRI contrast reveals enhanced ionic transport in plastic crystals.

    PubMed

    Romanenko, Konstantin; Jin, Liyu; Madsen, Louis A; Pringle, Jennifer M; O'Dell, Luke A; Forsyth, Maria

    2014-11-01

    Organic ionic plastic crystals (OIPCs) are attractive as solid-state electrolytes for electrochemical devices such as lithium-ion batteries and solar and fuel cells. OIPCs offer high ionic conductivity, nonflammability, and versatility of molecular design. Nevertheless, intrinsic ion transport behavior of OIPCs is not fully understood, and their measured properties depend heavily on thermal history. Solid-state magnetic resonance imaging experiments reveal a striking image contrast anisotropy sensitive to the orientation of grain boundaries in polycrystalline OIPCs. Probing triethyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1222FSI) samples with different thermal history demonstrates vast variations in microcrystallite alignment. Upon slow cooling from the melt, microcrystallites exhibit a preferred orientation throughout the entire sample, leading to an order of magnitude increase in conductivity as probed using impedance spectroscopy. This investigation describes both a new conceptual window and a new characterization method for understanding polycrystalline domain structure and transport in plastic crystals and other solid-state conductors. PMID:25312993

  8. Nonequilibrium Enhances Adaptation Efficiency of Stochastic Biochemical Systems

    PubMed Central

    Jia, Chen; Qian, Minping

    2016-01-01

    Adaptation is a crucial biological function possessed by many sensory systems. Early work has shown that some influential equilibrium models can achieve accurate adaptation. However, recent studies indicate that there are close relationships between adaptation and nonequilibrium. In this paper, we provide an explanation of these two seemingly contradictory results based on Markov models with relatively simple networks. We show that as the nonequilibrium driving becomes stronger, the system under consideration will undergo a phase transition along a fixed direction: from non-adaptation to simple adaptation then to oscillatory adaptation, while the transition in the opposite direction is forbidden. This indicates that although adaptation may be observed in equilibrium systems, it tends to occur in systems far away from equilibrium. In addition, we find that nonequilibrium will improve the performance of adaptation by enhancing the adaptation efficiency. All these results provide a deeper insight into the connection between adaptation and nonequilibrium. Finally, we use a more complicated network model of bacterial chemotaxis to validate the main results of this paper. PMID:27195482

  9. Absolute perfusion measurements and associated iodinated contrast agent time course in brain metastasis: a study for contrast-enhanced radiotherapy.

    PubMed

    Obeid, Layal; Deman, Pierre; Tessier, Alexandre; Balosso, Jacques; Estève, François; Adam, Jean-François

    2014-04-01

    Contrast-enhanced radiotherapy is an innovative treatment that combines the selective accumulation of heavy elements in tumors with stereotactic irradiations using medium energy X-rays. The radiation dose enhancement depends on the absolute amount of iodine reached in the tumor and its time course. Quantitative, postinfusion iodine biodistribution and associated brain perfusion parameters were studied in human brain metastasis as key parameters for treatment feasibility and quality. Twelve patients received an intravenous bolus of iodinated contrast agent (CA) (40 mL, 4 mL/s), followed by a steady-state infusion (160 mL, 0.5 mL/s) to ensure stable intratumoral amounts of iodine during the treatment. Absolute iodine concentrations and quantitative perfusion maps were derived from 40 multislice dynamic computed tomography (CT) images of the brain. The postinfusion mean intratumoral iodine concentration (over 30 minutes) reached 1.94 ± 0.12 mg/mL. Reasonable correlations were obtained between these concentrations and the permeability surface area product and the cerebral blood volume. To our knowledge, this is the first quantitative study of CA biodistribution versus time in brain metastasis. The study shows that suitable and stable amounts of iodine can be reached for contrast-enhanced radiotherapy. Moreover, the associated perfusion measurements provide useful information for the patient recruitment and management processes.

  10. 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

  11. Renal Tumor Quantification and Classification in Contrast-Enhanced Abdominal CT

    PubMed Central

    Linguraru, Marius George; Yao, Jianhua; Gautam, Rabindra; Peterson, James; Li, Zhixi; Linehan, W. Marston; Summers, Ronald M.

    2008-01-01

    Kidney cancer occurs in both a hereditary (inherited) and sporadic (non-inherited) form. It is estimated that almost a quarter of a million people in the USA are living with kidney cancer and their number increases with 51,000 diagnosed with the disease every year. In clinical practice, the response to treatment is monitored by manual measurements of tumor size, which are 2D, do not reflect the 3D geometry and enhancement of tumors, and show high intra- and inter-operator variability. We propose a computer-assisted radiology tool to assess renal tumors in contrast-enhanced CT for the management of tumor diagnoses and responses to new treatments. The algorithm employs anisotropic diffusion (for smoothing), a combination of fast-marching and geodesic level-sets (for segmentation), and a novel statistical refinement step to adapt to the shape of the lesions. It also quantifies the 3D size, volume and enhancement of the lesion and allows serial management over time. Tumors are robustly segmented and the comparison between manual and semi-automated quantifications shows disparity within the limits of inter-observer variability. The analysis of lesion enhancement for tumor classification shows great separation between cysts, von Hippel-Lindau syndrome lesions and hereditary papillary renal carcinomas (HPRC) with p-values inferior to 0.004. The results on temporal evaluation of tumors from serial scans illustrate the potential of the method to become an important tool for disease monitoring, drug trials and noninvasive clinical surveillance. PMID:19492069

  12. Prostate cancer characterization by optical contrast enhanced photoacoustics

    NASA Astrophysics Data System (ADS)

    Xu, Guan; Qin, Ming; Mukundan, Ananya; Siddiqui, Javed; Takada, Marilia; Vilar-Saavedra, Paulo; Tomlins, Scott A.; Kopelman, Raoul; Wang, Xueding

    2016-03-01

    During the past decades, prostate cancer (PCa), with an annual incident rate much higher than any other cancer, is the most commonly diagnosed cancer in American men. PCa has a relatively low progression rate yet the survival percentage decreases dramatically once the cancer has metastasized. Identifying aggressive from indolent PCa to prevent metastasis and death is critical to improving outcomes for patients with PCa. Standard procedure for assessing the aggressiveness of PCa involves the removal of tumor tissues by transrectal (TR) ultrasound (US) guided needle biopsy. The microscopic architecture of the biopsied tissue is visualized by histological or immunohistochemical staining procedures. The heterogeneity of the microscopic architecture is characterized by a Gleason score, a quantitative description of the aggressiveness of PCa. Due to the inability to identify the cancer cells, most noninvasive imaging modalities can only provide diagnosis of PCa at limited accuracy. This study investigates the feasibility of identifying PCa tumors and characterizing the aggressiveness of PCa by photoacoustic imaging assisted by cancer targeting polyacrylamide (PAA) nanoparticles (NPs). PAA is a biocompatible material used in clinics for the past 20 years. PAA NPs can protect capsulated optical contrast agents from interference by enzymes and enable prolonged systematic circulation in the living biological environment. The cancer targeting mechanism is achieved by conjugating the NPs to F3 peptides, which trace nucleolin overexpressed on the surface of cancer cells. Preliminary studies have shown that the NPs are capable of staining the PCa cells in vivo.

  13. Adaptive fingerprint image enhancement with emphasis on preprocessing of data.

    PubMed

    Bartůnek, Josef Ström; Nilsson, Mikael; Sällberg, Benny; Claesson, Ingvar

    2013-02-01

    This article proposes several improvements to an adaptive fingerprint enhancement method that is based on contextual filtering. The term adaptive implies that parameters of the method are automatically adjusted based on the input fingerprint image. Five processing blocks comprise the adaptive fingerprint enhancement method, where four of these blocks are updated in our proposed system. Hence, the proposed overall system is novel. The four updated processing blocks are: 1) preprocessing; 2) global analysis; 3) local analysis; and 4) matched filtering. In the preprocessing and local analysis blocks, a nonlinear dynamic range adjustment method is used. In the global analysis and matched filtering blocks, different forms of order statistical filters are applied. These processing blocks yield an improved and new adaptive fingerprint image processing method. The performance of the updated processing blocks is presented in the evaluation part of this paper. The algorithm is evaluated toward the NIST developed NBIS software for fingerprint recognition on FVC databases.

  14. Evolution of nutrient acquisition: when adaptation fills the gap between contrasting ecological theories

    PubMed Central

    Boudsocq, S.; Barot, S.; Loeuille, N.

    2011-01-01

    Although plant strategies for acquiring nutrients have been widely studied from a functional point of view, their evolution is still not well understood. In this study, we investigate the evolutionary dynamics of these strategies and determine how they influence ecosystem properties. To do so, we use a simple nutrient-limited ecosystem model in which plant ability to take up nutrients is subject to adaptive dynamics. We postulate the existence of a trade-off between this ability and mortality. We show that contrasting strategies are possible as evolutionary outcomes, depending on the shape of the trade-off and, when nitrogen is considered as the limiting nutrient, on the intensity of symbiotic fixation. Our model enables us to bridge these evolutionary outcomes to classical ecological theories such as Hardin's tragedy of the commons and Tilman's rule of R*. Evolution does not systematically maximize plant biomass or primary productivity. On the other hand, each evolutionary outcome leads to a decrease in the availability of the limiting mineral nutrient, supporting the work of Tilman on competition between plants for a single resource. Our model shows that evolution can be used to link different classical ecological results and that adaptation may influence ecosystem properties in contrasted ways. PMID:20798113

  15. Evolution of nutrient acquisition: when adaptation fills the gap between contrasting ecological theories.

    PubMed

    Boudsocq, S; Barot, S; Loeuille, N

    2011-02-01

    Although plant strategies for acquiring nutrients have been widely studied from a functional point of view, their evolution is still not well understood. In this study, we investigate the evolutionary dynamics of these strategies and determine how they influence ecosystem properties. To do so, we use a simple nutrient-limited ecosystem model in which plant ability to take up nutrients is subject to adaptive dynamics. We postulate the existence of a trade-off between this ability and mortality. We show that contrasting strategies are possible as evolutionary outcomes, depending on the shape of the trade-off and, when nitrogen is considered as the limiting nutrient, on the intensity of symbiotic fixation. Our model enables us to bridge these evolutionary outcomes to classical ecological theories such as Hardin's tragedy of the commons and Tilman's rule of R*. Evolution does not systematically maximize plant biomass or primary productivity. On the other hand, each evolutionary outcome leads to a decrease in the availability of the limiting mineral nutrient, supporting the work of Tilman on competition between plants for a single resource. Our model shows that evolution can be used to link different classical ecological results and that adaptation may influence ecosystem properties in contrasted ways. PMID:20798113

  16. Contrast enhanced-magnetic resonance imaging as a surrogate to map verteporfin delivery in photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Samkoe, Kimberley S.; Bryant, Amber; Gunn, Jason R.; Pereira, Stephen P.; Hasan, Tayyaba; Pogue, Brian W.

    2013-12-01

    The use of in vivo contrast-enhanced magnetic resonance (MR) imaging as a surrogate for photosensitizer (verteporfin) dosimetry in photodynamic therapy of pancreas cancer is demonstrated by correlating MR contrast uptake to ex vivo fluorescence images on excised tissue. An orthotopic pancreatic xenograft mouse model was used for the study. A strong correlation (r=0.57) was found for bulk intensity measurements of T1-weighted gadolinium enhancement and verteporfin fluorescence in the tumor region of interest. The use of contrast-enhanced MR imaging shows promise as a method for treatment planning and photosensitizer dosimetry in human photodynamic therapy (PDT) of pancreas cancer.

  17. A flexible patch based approach for combined denoising and contrast enhancement of digital X-ray images.

    PubMed

    Irrera, Paolo; Bloch, Isabelle; Delplanque, Maurice

    2016-02-01

    Denoising and contrast enhancement play key roles in optimizing the trade-off between image quality and X-ray dose. However, these tasks present multiple challenges raised by noise level, low visibility of fine anatomical structures, heterogeneous conditions due to different exposure parameters, and patient characteristics. This work proposes a new method to address these challenges. We first introduce a patch-based filter adapted to the properties of the noise corrupting X-ray images. The filtered images are then used as oracles to define non parametric noise containment maps that, when applied in a multiscale contrast enhancement framework, allow optimizing the trade-off between improvement of the visibility of anatomical structures and noise reduction. A significant amount of tests on both phantoms and clinical images has shown that the proposed method is better suited than others for visual inspection for diagnosis, even when compared to an algorithm used to process low dose images in clinical routine. PMID:26716719

  18. A preliminary evaluation of self-made nanobubble in contrast-enhanced ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Li, Chunfang; Wu, Kaizhi; Li, Jing; Liu, Haijuan; Zhou, Qibing; Ding, Mingyue

    2014-03-01

    Nanoscale bubbles (nanobubbles) have been reported to improve contrast in tumor-targeted ultrasound imaging due to the enhanced permeation and retention effects at tumor vascular leaks. In this work, a self-made nanobubble ultrasound contrast agent was preliminarily characterized and evaluated in-vitro and in-vivo. Fundamental properties such as morphology appearance, size distribution, zeta potential, bubble concentration (bubble numbers per milliliter contrast agent suspension) and the stability of nanobubbles were assessed by light microscope and particle sizing analysis. Then the concentration intensity curve and time intensity curves (TICs) were acquired by ultrasound imaging experiment in-vitro. Finally, the contrast-enhanced ultrasonography was performed on rat to investigate the procedure of liver perfusion. The results showed that the nanobubbles had good shape and uniform distribution with the average diameter of 507.9 nm, polydispersity index (PDI) of 0.527, and zeta potential of -19.17 mV. Significant contrast enhancement was observed in in-vitro ultrasound imaging, demonstrating that the self-made nanobubbles can enhance the contrast effect of ultrasound imaging efficiently in-vitro. Slightly contrast enhancement was observed in in-vivo ultrasound imaging, indicating that the nanobubbles are not stable enough in-vivo. Future work will be focused on improving the ultrasonic imaging performance, stability, and antibody binding of the nanoscale ultrasound contrast agent.

  19. Integrated processing of contrast pulse sequencing ultrasound imaging for enhanced active contrast of hollow gas filled silica nanoshells and microshells.

    PubMed

    Ta, Casey N; Liberman, Alexander; Paul Martinez, H; Barback, Christopher V; Mattrey, Robert F; Blair, Sarah L; Trogler, William C; Kummel, Andrew C; Wu, Zhe

    2012-03-01

    In recent years, there have been increasing developments in the field of contrast-enhanced ultrasound both in the creation of new contrast agents and in imaging modalities. These contrast agents have been employed to study tumor vasculature in order to improve cancer detection and diagnosis. An in vivo study is presented of ultrasound imaging of gas filled hollow silica microshells and nanoshells which have been delivered intraperitoneally to an IGROV-1 tumor bearing mouse. In contrast to microbubbles, this formulation of microshells provided strong ultrasound imaging signals by shell disruption and release of gas. Imaging of the microshells in an animal model was facilitated by novel image processing. Although the particle signal could be identified by eye under live imaging, high background obfuscated the particle signal in still images and near the borders of the tumor with live images. Image processing techniques were developed that employed the transient nature of the particle signal to selectively filter out the background signal. By applying image registration, high-pass, median, threshold, and motion filtering, a short video clip of the particle signal was compressed into a single image, thereby resolving the silica shells within the tumor. © 2012 American Vacuum Society.

  20. Adaptive optics in spinning disk microscopy: improved contrast and brightness by a simple and fast method.

    PubMed

    Fraisier, V; Clouvel, G; Jasaitis, A; Dimitrov, A; Piolot, T; Salamero, J

    2015-09-01

    Multiconfocal microscopy gives a good compromise between fast imaging and reasonable resolution. However, the low intensity of live fluorescent emitters is a major limitation to this technique. Aberrations induced by the optical setup, especially the mismatch of the refractive index and the biological sample itself, distort the point spread function and further reduce the amount of detected photons. Altogether, this leads to impaired image quality, preventing accurate analysis of molecular processes in biological samples and imaging deep in the sample. The amount of detected fluorescence can be improved with adaptive optics. Here, we used a compact adaptive optics module (adaptive optics box for sectioning optical microscopy), which was specifically designed for spinning disk confocal microscopy. The module overcomes undesired anomalies by correcting for most of the aberrations in confocal imaging. Existing aberration detection methods require prior illumination, which bleaches the sample. To avoid multiple exposures of the sample, we established an experimental model describing the depth dependence of major aberrations. This model allows us to correct for those aberrations when performing a z-stack, gradually increasing the amplitude of the correction with depth. It does not require illumination of the sample for aberration detection, thus minimizing photobleaching and phototoxicity. With this model, we improved both signal-to-background ratio and image contrast. Here, we present comparative studies on a variety of biological samples.

  1. 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.

  2. Evaluation of Eu(II) -based positive contrast enhancement after intravenous, intraperitoneal, and subcutaneous injections.

    PubMed

    Ekanger, Levi A; Polin, Lisa A; Shen, Yimin; Haacke, E Mark; Allen, Matthew J

    2016-07-01

    Eu(II) -based contrast agents offer physiologically relevant, metal-based redox sensing that is unachievable with Gd(III) -based contrast agents. To evaluate the in vivo contrast enhancement of Eu(II) as a function of injection type, we performed intravenous, intraperitoneal, and subcutaneous injections in mice. Our data reveal a correlation between reported oxygen content and expected rates of diffusion with the persistence of Eu(II) -based contrast enhancement. Biodistribution studies revealed europium clearance through the liver and kidneys for intravenous and intraperitoneal injections, but no contrast enhancement was observed in organs associated with clearance. These data represent a step toward understanding the behavior of Eu(II) -based complexes in vivo. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27028559

  3. Contrast-enhanced ultrasonographic findings in three dogs with lung lobe torsion

    PubMed Central

    CAIVANO, Domenico; BIRETTONI, Francesco; BUFALARI, Antonello; DE MONTE, Valentina; ANGELI, Giovanni; GIORGI, Maria Elena; PATATA, Valentina; PORCIELLO, Francesco

    2015-01-01

    Lung lobe torsion is rare but life-threatening condition in the dog. Thoracic radiographs and conventional ultrasonography cannot be conclusive for the diagnosis, and computed tomography is useful but is limited by cost and availability. This report describes the findings of contrast-enhanced ultrasonography in 3 dogs with lung lobe torsion. Contrast-enhanced ultrasonography showed the absence or reduction of pulmonary vascularization secondary to twisting of the lung lobe around its bronchovascular pedicle in all three dogs. Moreover, contrast-enhanced ultrasonography distinguished partial pulmonary atelectasis from a lung lobe torsion. These preliminary results suggest that contrast-enhanced ultrasonography can improve the accuracy of conventional ultrasonography for detection of pulmonary blood flow compromise in dogs with lung lobe torsion. PMID:26498403

  4. Detection of Leptomeningeal Metastasis by Contrast-Enhanced 3D T1-SPACE: Comparison with 2D FLAIR and Contrast-Enhanced 2D T1-Weighted Images

    PubMed Central

    Gil, Bomi; Hwang, Eo-Jin; Lee, Song; Jang, Jinhee; Jung, So-Lyung; Ahn, Kook-Jin; Kim, Bum-soo

    2016-01-01

    Introduction To compare the diagnostic accuracy of contrast-enhanced 3D(dimensional) T1-weighted sampling perfection with application-optimized contrasts by using different flip angle evolutions (T1-SPACE), 2D fluid attenuated inversion recovery (FLAIR) images and 2D contrast-enhanced T1-weighted image in detection of leptomeningeal metastasis except for invasive procedures such as a CSF tapping. Materials and Methods Three groups of patients were included retrospectively for 9 months (from 2013-04-01 to 2013-12-31). Group 1 patients with positive malignant cells in CSF cytology (n = 22); group 2, stroke patients with steno-occlusion in ICA or MCA (n = 16); and group 3, patients with negative results on MRI, whose symptom were dizziness or headache (n = 25). A total of 63 sets of MR images are separately collected and randomly arranged: (1) CE 3D T1-SPACE; (2) 2D FLAIR; and (3) CE T1-GRE using a 3-Tesla MR system. A faculty neuroradiologist with 8-year-experience and another 2nd grade trainee in radiology reviewed each MR image- blinded by the results of CSF cytology and coded their observations as positives or negatives of leptomeningeal metastasis. The CSF cytology result was considered as a gold standard. Sensitivity and specificity of each MR images were calculated. Diagnostic accuracy was compared using a McNemar’s test. A Cohen's kappa analysis was performed to assess inter-observer agreements. Results Diagnostic accuracy was not different between 3D T1-SPACE and CSF cytology by both raters. However, the accuracy test of 2D FLAIR and 2D contrast-enhanced T1-weighted GRE was inconsistent by the two raters. The Kappa statistic results were 0.657 (3D T1-SPACE), 0.420 (2D FLAIR), and 0.160 (2D contrast-enhanced T1-weighted GRE). The 3D T1-SPACE images showed the highest inter-observer agreements between the raters. Conclusions Compared to 2D FLAIR and 2D contrast-enhanced T1-weighted GRE, contrast-enhanced 3D T1 SPACE showed a better detection rate of

  5. Photon counting CT of the liver with dual-contrast enhancement

    NASA Astrophysics Data System (ADS)

    Muenzel, Daniela; Proksa, Roland; Daerr, Heiner; Fingerle, Alexander A.; Pfeiffer, Franz; Rummeny, Ernst J.; Noël, Peter B.

    2016-03-01

    The diagnostic quality of photon counting computed tomography (PCCT) is one the unexplored areas in medical imaging; at the same time, it seems to offer the opportunity as a fast and highly sensitive diagnostic tool. Today, conventional computed tomography (CT) is the standard imaging technique for diagnostic evaluation of the parenchyma of the liver. However, considerations on radiation dose are still an important factor in CT liver imaging, especially with regard to multi-phase contrast enhanced CT. In this work we report on a feasibility study for multi-contrast PCCT for simultaneous liver imaging at different contrast phases. PCCT images of the liver were simulated for a contrast-enhanced examination performed with two different contrast agents (CA), iodine (CA 1) and gadolinium (CA 2). PCCT image acquisition was performed at the time point with portal venous contrast distribution of CA 1 and arterial contrast phase for CA 2. Therefore, a contrast injection protocol was planned with sequential injection of CA 1 and CA 2 to provide a time dependent difference in contrast distribution of both CAs in the vessels and parenchyma of the liver. Native, arterial, and portal venous contrast enhanced images have been calculated based on the spectral separation of PCCT. In simulated PCCT images, we were able to differentiate between the tissue enhancement of CA 1 and CA 2. The distribution of both CA within the parenchyma of the liver was illustrated with perfusion maps for CA 1 and CA 2. In addition, virtual noncontrast enhanced image were calculated. In conclusion, multi-phase PCCT imaging of the liver based on a single scan is a novel approach for spectral PCCT imaging, offering detailed contrast information in a single scan volume and a significant reduction of radiation dose.

  6. A new hardware-efficient algorithm and reconfigurable architecture for image contrast enhancement.

    PubMed

    Huang, Shih-Chia; Chen, Wen-Chieh

    2014-10-01

    Contrast enhancement is crucial when generating high quality images for image processing applications, such as digital image or video photography, liquid crystal display processing, and medical image analysis. In order to achieve real-time performance for high-definition video applications, it is necessary to design efficient contrast enhancement hardware architecture to meet the needs of real-time processing. In this paper, we propose a novel hardware-oriented contrast enhancement algorithm which can be implemented effectively for hardware design. In order to be considered for hardware implementation, approximation techniques are proposed to reduce these complex computations during performance of the contrast enhancement algorithm. The proposed hardware-oriented contrast enhancement algorithm achieves good image quality by measuring the results of qualitative and quantitative analyzes. To decrease hardware cost and improve hardware utilization for real-time performance, a reduction in circuit area is proposed through use of parameter-controlled reconfigurable architecture. The experiment results show that the proposed hardware-oriented contrast enhancement algorithm can provide an average frame rate of 48.23 frames/s at high definition resolution 1920 × 1080.

  7. 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.

  8. Digital speech enhancement based on DTOMP and adaptive quantile

    NASA Astrophysics Data System (ADS)

    Wang, Anna; Zhou, Xiaoxing; Xue, Changliang; Sun, Xiyan; Sun, Hongying

    2013-03-01

    Compressed Sensing (CS) that can effectively extract the information contained in the signal is a new sampling theory based on signal sparseness. This paper applies CS theory in digital speech signal enhancement processing, proposes an adaptive quantile method for the noise power estimation and combines the improved double-threshold orthogonal matching pursuit algorithm for speech reconstruction, then achieves speech enhancement processing. Compared with the simulation results of the spectral subtraction and the subspace algorithm, the experiment results verify the feasibility and effectiveness of the algorithm proposed in this paper applied to speech enhancement processing.

  9. NOTE: Independent component analysis of dynamic contrast-enhanced computed tomography images

    NASA Astrophysics Data System (ADS)

    Koh, T. S.; Yang, X.; Bisdas, S.; Lim, C. C. T.

    2006-10-01

    Independent component analysis (ICA) was applied on dynamic contrast-enhanced computed tomography images of cerebral tumours to extract spatial component maps of the underlying vascular structures, which correspond to different haemodynamic phases as depicted by the passage of the contrast medium. The locations of arteries, veins and tumours can be separately identified on these spatial component maps. As the contrast enhancement behaviour of the cerebral tumour differs from the normal tissues, ICA yields a tumour component map that reveals the location and extent of the tumour. Tumour outlines can be generated using the tumour component maps, with relatively simple segmentation methods.

  10. Multiscale image fusion using an adaptive similarity-based sensor weighting scheme and human visual system-inspired contrast measure

    NASA Astrophysics Data System (ADS)

    Nercessian, Shahan C.; Panetta, Karen A.; Agaian, Sos S.

    2012-04-01

    The goal of image fusion is to combine multiple source images obtained using different capture techniques into a single image to provide an effective contextual enhancement of a scene for human or machine perception. In practice, considerable value can be gained in the fusion of images that are dissimilar or complementary in nature. However, in such cases, global weighting schemes may not sufficiently weigh the contribution of the pertinent information of the source images, while existing adaptive schemes calculate weights based on the relative amounts of salient features, which can cause severe artifacting or inadequate local luminance in the fusion result. Accordingly, a new multiscale image fusion algorithm is proposed. The approximation coefficient fusion rule of the algorithm is based on a novel similarity based weighting scheme capable of providing improved fusion results when the input source images are either similar or dissimilar to each other. Moreover, the algorithm employs a new detail coefficient fusion rule integrating a parametric multiscale contrast measure. The parametric nature of the contrast measure allows the degree to which psychophysical laws of human vision hold to be tuned based on image-dependent characteristics. Experimental results illustrate the superior performance of the proposed algorithm qualitatively and quantitatively.

  11. Quantitative Characterization of Inertial Confinement Fusion Capsules Using Phase Contrast Enhanced X-Ray Imaging

    SciTech Connect

    Kozioziemski, B J; Koch, J A; Barty, A; Martz, H E; Lee, W; Fezzaa, K

    2004-05-07

    Current designs for inertial confinement fusion capsules for the National Ignition Facility (NIF) consist of a solid deuterium-tritium (D-T) fuel layer inside of a copper doped beryllium capsule. Phase contrast enhanced x-ray imaging is shown to render the D-T layer visible inside the Be(Cu) capsule. Phase contrast imaging is experimentally demonstrated for several surrogate capsules and validates computational models. Polyimide and low density divinyl benzene foam capsules were imaged at the Advanced Photon Source synchrotron. The surrogates demonstrate that phase contrast enhanced imaging provides a method to characterize surfaces when absorption imaging cannot be used. Our computational models demonstrate that a rough surface can be accurately reproduced in phase contrast enhanced x-ray images.

  12. Tumor characterization in small animals using magnetic resonance-guided dynamic contrast enhanced diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Lin, Yuting; Thayer, Dave; Nalcioglu, Orhan; Gulsen, Gultekin

    2011-10-01

    We present a magnetic resonance (MR)-guided near-infrared dynamic contrast enhanced diffuse optical tomography (DCE-DOT) system for characterization of tumors using an optical contrast agent (ICG) and a MR contrast agent [Gd-diethylenetriaminepentaacetic acid (DTPA)] in a rat model. Both ICG and Gd-DTPA are injected and monitored simultaneously using a combined MRI-DOT system, resulting in accurate co-registration between two imaging modalities. Fisher rats bearing R3230 breast tumor are imaged using this hybrid system. For the first time, enhancement kinetics of the exogenous contrast ICG is recovered from the DCE-DOT data using MR anatomical a priori information. As tumors grow, they undergo necrosis and the tissue transforms from viable to necrotic. The results show that the physiological changes between viable and necrotic tissue can be differentiated more accurately based on the ICG enhancement kinetics when MR anatomical information is utilized.

  13. Bayesian adaptive estimation of the contrast sensitivity function: The quick CSF method

    PubMed Central

    Lesmes, Luis Andres; Lu, Zhong-Lin; Baek, Jongsoo; Albright, Thomas D.

    2015-01-01

    The contrast sensitivity function (CSF) predicts functional vision better than acuity, but long testing times prevent its psychophysical assessment in clinical and practical applications. This study presents the quick CSF (qCSF) method, a Bayesian adaptive procedure that applies a strategy developed to estimate multiple parameters of the psychometric function (A. B. Cobo-Lewis, 1996; L. L. Kontsevich & C. W. Tyler, 1999). Before each trial, a one-step-ahead search finds the grating stimulus (defined by frequency and contrast) that maximizes the expected information gain (J. V. Kujala & T. J. Lukka, 2006; L. A. Lesmes et al., 2006), about four CSF parameters. By directly estimating CSF parameters, data collected at one spatial frequency improves sensitivity estimates across all frequencies. A psychophysical study validated that CSFs obtained with 100 qCSF trials (~10 min) exhibited good precision across spatial frequencies (SD < 2–3 dB) and excellent agreement with CSFs obtained independently (mean RMSE = 0.86 dB). To estimate the broad sensitivity metric provided by the area under the log CSF (AULCSF), only 25 trials were needed to achieve a coefficient of variation of 15–20%. The current study demonstrates the method’s value for basic and clinical investigations. Further studies, applying the qCSF to measure wider ranges of normal and abnormal vision, will determine how its efficiency translates to clinical assessment. PMID:20377294

  14. A comparative study of contrast enhanced ultrasound and contrast enhanced magnetic resonance imaging for the detection and characterization of hepatic hemangiomas.

    PubMed

    Fang, Liang; Zhu, Zheng; Huang, Beijian; Ding, Hong; Mao, Feng; Li, Chaolun; Zeng, Mengsu; Zhou, Jianjun; Wang, Ling; Wang, Wenping; Chen, Yue

    2015-04-01

    This study aims to compare contrast enhanced ultrasound (CEUS) and contrast enhanced magnetic resonance imaging (CEMRI) for the detection and characterization of hepatic hemangiomas. Included in this retrospective study were 83 histopathologically confirmed lesions of hemangioma in 66 hospitalized patients who underwent both CEUS and CEMRI and received surgery. The enhancement patterns on CEUS and CEMRI in each lesion were compared and analyzed. In addition, data obtained by the two modalities were then compared with the pathological findings to determine their value in differential diagnosis of hepatic hemangiomas. CEUS diagnosed 78 lesions of hemangioma against 80 by CEMRI. There were no statistical significant differences in the diagnostic value between CEUS and CEMRI in terms of sensitivity (88.0% vs. 92.8%), specificity (99.0% vs. 99.4%), accuracy (97.3% vs. 98.4%), positive predictive value (93.6% vs. 96.3%), and negative predictive value (98.0% vs. 98.8%) (p > 0.05, all). In the arterial phase, the main enhancement pattern on both CEUS and CEMRI was peripheral nodular enhancement (73 vs. 76), but lesions with diffuse enhancement on CEUS outnumbered those on CEMRI (3 vs. 1) and lesions with circular enhancement on CEMRI outnumbered those on CEUS (3 vs. 2). In the portal venous phase and delayed phase, the main enhancement pattern was hyperechoic change on CEUS and hyperintense on CEMRI (66 vs. 65), some lesions presented isoechoic change (12 vs. 15). These results suggested CEUS, an equivalent to CEMRI, may have an added diagnostic value in hemangiomas.

  15. Climate change adaptation among Tibetan pastoralists: challenges in enhancing local adaptation through policy support.

    PubMed

    Fu, Yao; Grumbine, R Edward; Wilkes, Andreas; Wang, Yun; Xu, Jian-Chu; Yang, Yong-Ping

    2012-10-01

    While researchers are aware that a mix of Local Ecological Knowledge (LEK), community-based resource management institutions, and higher-level institutions and policies can facilitate pastoralists' adaptation to climate change, policy makers have been slow to understand these linkages. Two critical issues are to what extent these factors play a role, and how to enhance local adaptation through government support. We investigated these issues through a case study of two pastoral communities on the Tibetan Plateau in China employing an analytical framework to understand local climate adaptation processes. We concluded that LEK and community-based institutions improve adaptation outcomes for Tibetan pastoralists through shaping and mobilizing resource availability to reduce risks. Higher-level institutions and policies contribute by providing resources from outside communities. There are dynamic interrelationships among these factors that can lead to support, conflict, and fragmentation. Government policy could enhance local adaptation through improvement of supportive relationships among these factors. While central government policies allow only limited room for overt integration of local knowledge/institutions, local governments often have some flexibility to buffer conflicts. In addition, government policies to support market-based economic development have greatly benefited adaptation outcomes for pastoralists. Overall, in China, there are still questions over how to create innovative institutions that blend LEK and community-based institutions with government policy making.

  16. Management of incidental renal masses: Time to consider contrast-enhanced ultrasonography.

    PubMed

    Di Vece, Francesca; Tombesi, Paola; Ermili, Francesca; Sartori, Sergio

    2016-02-01

    Proliferation of imaging studies for different clinical purposes and continuous improvement of imaging technology have led to an increasing number of incidental findings of renal masses. It is estimated that over 50% of patients older than 50 years have at least one renal mass. The majority of incidental renal masses are simple cysts that can be easily diagnosed by conventional ultrasonography. However, some incidental renal masses are not simple cysts, and differentiation between benign and malignant entities requires further imaging modalities. In the past, multiphase contrast-enhanced computed tomography and magnetic resonance imaging were considered the primary imaging modalities used to characterize and stage complex cystic and solid renal lesions. Currently, contrast-enhanced ultrasonography represents a novel alternative to contrast-enhanced computed tomography and magnetic resonance imaging. Contrast-enhanced ultrasonography employs microbubble contrast agents that allow the study of different enhancement phases of the kidney without risk of nephrotoxicity and radiation exposure. The diagnostic accuracy of contrast-enhanced ultrasonography in the characterization of complex renal cysts is comparable to that of computed tomography and magnetic resonance imaging, and several studies have demonstrated its reliability also in identifying solid lesions such as pseudotumors, typical angiomyolipomas, and clear cell renal carcinomas. Considering the high incidence of incidental renal masses and the need for rapid and reliable diagnosis, contrast-enhanced ultrasonography could be proposed as the first step in the diagnostic work-up of renal masses because of its safety and cost effectiveness. In this paper, we propose a diagnostic algorithm for the characterization of cystic and solid renal masses. PMID:27433273

  17. Optimized dynamic contrast-enhanced cone-beam CT for target visualization during liver SBRT

    NASA Astrophysics Data System (ADS)

    Jones, Bernard L.; Altunbas, Cem; Kavanagh, Brian; Schefter, Tracey; Miften, Moyed

    2014-03-01

    The pharmacokinetic behavior of iodine contrast agents makes it difficult to achieve significant enhancement during contrast-enhanced cone-beam CT (CE-CBCT). This study modeled this dynamic behavior to optimize CE-CBCT and improve the localization of liver lesions for SBRT. We developed a model that allows for controlled study of changing iodine concentrations using static phantoms. A projection database consisting of multiple phantom images of differing iodine/scan conditions was built. To reconstruct images of dynamic hepatic concentrations, hepatic contrast enhancement data from conventional CT scans were used to re-assemble the projections to match the expected amount of contrast. In this way the effect of various parameters on image quality was isolated, and using our dynamic model we found parameters for iodine injection, CBCT scanning, and injection/scanning timing which optimize contrast enhancement. Increasing the iodine dose, iodine injection rate, and imaging dose led to significant increases in signal-to-noise ratio (SNR). Reducing the CBCT imaging time also increased SNR, as the image can be completed before the iodine exits the liver. Proper timing of image acquisition played a significant role, as a 30 second error in start time resulted in a 40% SNR decrease. The effect of IV contrast is severely degraded in CBCT, but there is promise that, with optimization of the injection and scan parameters to account for iodine pharmacokinetics, CE-CBCT which models venous-phase blood flow kinetics will be feasible for accurate localization of liver lesions.

  18. Digital contrast enhancement of 18Fluorine-fluorodeoxyglucose positron emission tomography images in hepatocellular carcinoma

    PubMed Central

    Pandey, Anil Kumar; Sharma, Sanjay Kumar; Agarwal, Krishan Kant; Sharma, Punit; Bal, Chandrasekhar; Kumar, Rakesh

    2016-01-01

    Purpose: The role of 18fluorodeoxyglucose positron emission tomography (PET) is limited for detection of primary hepatocellular carcinoma (HCC) due to low contrast to the tumor, and normal hepatocytes (background). The aim of the present study was to improve the contrast between the tumor and background by standardizing the input parameters of a digital contrast enhancement technique. Materials and Methods: A transverse slice of PET image was adjusted for the best possible contrast, and saved in JPEG 2000 format. We processed this image with a contrast enhancement technique using 847 possible combinations of input parameters (threshold “m” and slope “e”). The input parameters which resulted in an image having a high value of 2nd order entropy, and edge content, and low value of absolute mean brightness error, and saturation evaluation metrics, were considered as standardized input parameters. The same process was repeated for total nine PET-computed tomography studies, thus analyzing 7623 images. Results: The selected digital contrast enhancement technique increased the contrast between the HCC tumor and background. In seven out of nine images, the standardized input parameters “m” had values between 150 and 160, and for other two images values were 138 and 175, respectively. The value of slope “e” was 4 in 4 images, 3 in 3 images and 1 in 2 images. It was found that it is important to optimize the input parameters for the best possible contrast for each image; a particular value was not sufficient for all the HCC images. Conclusion: The use of above digital contrast enhancement technique improves the tumor to background ratio in PET images of HCC and appears to be useful. Further clinical validation of this finding is warranted. PMID:26917889

  19. Stick-guided lateral inhibition for enhancement of low-contrast image

    NASA Astrophysics Data System (ADS)

    Tu, Shengxian; Wu, Yilun; Lu, Xuesong; Huo, Hong; Fang, Tao

    2007-11-01

    The inhibitory interaction has long been observed in the lateral eye of the Limulus and been integrated into mechanism of enhancing contrast. When applying to the enhancement of low-contrast image for segmenting interested objects, the original lateral inhibition model will simultaneously amplify noises while enhancing edges contrast. This paper presents a new lateral inhibition model, which is called Stick-Guided Lateral Inhibition, for enhancement of low-contrast image so that week edges may exert a stronger force to catch the boundary of targets in the latter segmentation. First, the guided inhibition term is introduced as a general framework for improving the performance of lateral inhibition models in the presence of noises. Then, by using asymmetric sticks to guide the inhibiting process, we are able to accentuate the intensity gradients of image-edges and contours while suppressing the amplification of noises. Experiments on synthetic images and remote sensor images show that our model significantly enhances low-contrast images and improves the performance of latter segmentation.

  20. Iomeprol versus iopamidol in contrast-enhanced computed tomography of thoracic and abdominal organs.

    PubMed

    Valentini, A L; Tartaglione, T; Monti, L; Marano, P

    1994-05-01

    The aim of this double-blind, parallel-group study was to compare the safety, tolerance, and efficacy of iomeprol-350 (350 mgI/ml), iomeprol-400 (400 mgI/ml) and iopamidol-370 (370 mgI/ml) for use in contrast-enhanced body computed tomography (CT). Following written informed consent, 120 adult inpatients of either sex requiring CT of thoracic or abdominal organs were randomly assigned to receive iomeprol-350, iomeprol-400 or iopamidol-370. Pre- and post-contrast, all patients underwent clinical, instrumental and laboratory investigation to assess the safety of the test agents. Tolerance was assessed in terms of discomfort associated with contrast injection. Two experienced radiologists independently and blindly graded the quality of contrast enhancement obtained with the different contrast solutions by means of a five-point ordinal scale as follows: 1, insufficient; 2, sufficient; 3, good; 4, excellent; or E, excessive. Patients in the iomeprol groups needed fewer injections and a smaller volume of contrast medium to obtain examinations of adequate diagnostic quality. Contrast enhancement was judged as excellent or good in about 90% of the study examinations, without significant differences between the three study groups. During contrast injection, heat and pain sensations were minimal or absent in most cases. No serious adverse events occurred throughout the study. No significant changes in clinical, instrumental or laboratory safety parameters were observed. In conclusion, iomeprol-400 and iomeprol-350 appear to be contrast solutions at least as safe, well tolerated and effective as iopamidol-370 when used as contrast agents for body CT.

  1. Eco-physiological adaptation of dominant tree species at two contrasting karst habitats in southwestern China.

    PubMed

    Zhang, Shouren; Fan, Dayong; Wu, Qian; Yan, Hui; Xu, Xinwu

    2013-01-01

    The purpose of this study was to investigate the eco-physiological adaptation of indigenous woody species to their habitats in karst areas of southwestern China. Two contrasting forest habitats were studied: a degraded habitat in Daxiagu and a well-developed habitat in Tianlongshan, and the eco-physiological characteristics of the trees were measured for three growth seasons. Photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (Tr) of the tree species in Daxiagu were 2-3 times higher than those in Tianlongshan under ambient conditions. However, this habitat effect was not significant when measurements were taken under controlled conditions. Under controlled conditions, Pn, gs, and Tr of the deciduous species were markedly higher than those for the evergreen species. Habitat had no significant effect on water use efficiency (WUE) or photochemical characteristics of PSII. The stomatal sensitivity of woody species in the degraded habitat was much higher than that in the well-developed habitat. Similarly, the leaf total nitrogen (N) and phosphorus (P) contents expressed on the basis of either dry mass or leaf area were also much higher in Daxiagu than they were in Tianlongshan. The mass-based leaf total N content of deciduous species was much higher than that of evergreen species, while leaf area-based total N and P contents of evergreens were significantly higher than those of deciduous species. The photosynthetic nitrogen- and phosphorus-use efficiencies (PNUE and PPUE) of deciduous species were much higher than those of evergreens. Further, the PPUE of the woody species in Tianlongshan was much higher than that  of the woody species in Daxiagu. The results from three growth seasons imply that the tree species were able to adapt well to their growth habitats. Furthermore, it seems that so-called "temporary drought stress" may not occur, or may not be severe for most woody plants in karst areas of southwestern China.

  2. Adaptive methods of two-scale edge detection in post-enhancement visual pattern processing

    NASA Astrophysics Data System (ADS)

    Rahman, Zia-ur; Jobson, Daniel J.; Woodell, Glenn A.

    2008-04-01

    Adaptive methods are defined and experimentally studied for a two-scale edge detection process that mimics human visual perception of edges and is inspired by the parvo-cellular (P) and magno-cellular (M) physiological subsystems of natural vision. This two-channel processing consists of a high spatial acuity/coarse contrast channel (P) and a coarse acuity/fine contrast (M) channel. We perform edge detection after a very strong non-linear image enhancement that uses smart Retinex image processing. Two conditions that arise from this enhancement demand adaptiveness in edge detection. These conditions are the presence of random noise further exacerbated by the enhancement process, and the equally random occurrence of dense textural visual information. We examine how to best deal with both phenomena with an automatic adaptive computation that treats both high noise and dense textures as too much information, and gracefully shifts from a smallscale to medium-scale edge pattern priorities. This shift is accomplished by using different edge-enhancement schemes that correspond with the (P) and (M) channels of the human visual system. We also examine the case of adapting to a third image condition, namely too little visual information, and automatically adjust edge detection sensitivities when sparse feature information is encountered. When this methodology is applied to a sequence of images of the same scene but with varying exposures and lighting conditions, this edge-detection process produces pattern constancy that is very useful for several imaging applications that rely on image classification in variable imaging conditions.

  3. Non-linear direct multi-scale image enhancement based on the luminance and contrast masking characteristics of the human visual system.

    PubMed

    Nercessian, Shahan C; Panetta, Karen A; Agaian, Sos S

    2013-09-01

    Image enhancement is a crucial pre-processing step for various image processing applications and vision systems. Many enhancement algorithms have been proposed based on different sets of criteria. However, a direct multi-scale image enhancement algorithm capable of independently and/or simultaneously providing adequate contrast enhancement, tonal rendition, dynamic range compression, and accurate edge preservation in a controlled manner has yet to be produced. In this paper, a multi-scale image enhancement algorithm based on a new parametric contrast measure is presented. The parametric contrast measure incorporates not only the luminance masking characteristic, but also the contrast masking characteristic of the human visual system. The formulation of the contrast measure can be adapted for any multi-resolution decomposition scheme in order to yield new human visual system-inspired multi-scale transforms. In this article, it is exemplified using the Laplacian pyramid, discrete wavelet transform, stationary wavelet transform, and dual-tree complex wavelet transform. Consequently, the proposed enhancement procedure is developed. The advantages of the proposed method include: 1) the integration of both the luminance and contrast masking phenomena; 2) the extension of non-linear mapping schemes to human visual system inspired multi-scale contrast coefficients; 3) the extension of human visual system-based image enhancement approaches to the stationary and dual-tree complex wavelet transforms, and a direct means of; 4) adjusting overall brightness; and 5) achieving dynamic range compression for image enhancement within a direct multi-scale enhancement framework. Experimental results demonstrate the ability of the proposed algorithm to achieve simultaneous local and global enhancements.

  4. Adaptive strategies in nocturnally migrating insects and songbirds: contrasting responses to wind.

    PubMed

    Chapman, Jason W; Nilsson, Cecilia; Lim, Ka S; Bäckman, Johan; Reynolds, Don R; Alerstam, Thomas

    2016-01-01

    Animals that use flight as their mode of transportation must cope with the fact that their migration and orientation performance is strongly affected by the flow of the medium they are moving in, that is by the winds. Different strategies can be used to mitigate the negative effects and benefit from the positive effects of a moving flow. The strategies an animal can use will be constrained by the relationship between the speed of the flow and the speed of the animal's own propulsion in relation to the surrounding air. Here we analyse entomological and ornithological radar data from north-western Europe to investigate how two different nocturnal migrant taxa, the noctuid moth Autographa gamma and songbirds, deal with wind by analysing variation in resulting flight directions in relation to the wind-dependent angle between the animal's heading and track direction. Our results, from fixed locations along the migratory journey, reveal different global strategies used by moths and songbirds during their migratory journeys. As expected, nocturnally migrating moths experienced a greater degree of wind drift than nocturnally migrating songbirds, but both groups were more affected by wind in autumn than in spring. The songbirds' strategies involve elements of both drift and compensation, providing some benefits from wind in combination with destination and time control. In contrast, moths expose themselves to a significantly higher degree of drift in order to obtain strong wind assistance, surpassing the songbirds in mean ground speed, at the cost of a comparatively lower spatiotemporal migratory precision. Moths and songbirds show contrasting but adaptive responses to migrating through a moving flow, which are fine-tuned to the respective flight capabilities of each group in relation to the wind currents they travel within.

  5. Adaptive strategies in nocturnally migrating insects and songbirds: contrasting responses to wind.

    PubMed

    Chapman, Jason W; Nilsson, Cecilia; Lim, Ka S; Bäckman, Johan; Reynolds, Don R; Alerstam, Thomas

    2016-01-01

    Animals that use flight as their mode of transportation must cope with the fact that their migration and orientation performance is strongly affected by the flow of the medium they are moving in, that is by the winds. Different strategies can be used to mitigate the negative effects and benefit from the positive effects of a moving flow. The strategies an animal can use will be constrained by the relationship between the speed of the flow and the speed of the animal's own propulsion in relation to the surrounding air. Here we analyse entomological and ornithological radar data from north-western Europe to investigate how two different nocturnal migrant taxa, the noctuid moth Autographa gamma and songbirds, deal with wind by analysing variation in resulting flight directions in relation to the wind-dependent angle between the animal's heading and track direction. Our results, from fixed locations along the migratory journey, reveal different global strategies used by moths and songbirds during their migratory journeys. As expected, nocturnally migrating moths experienced a greater degree of wind drift than nocturnally migrating songbirds, but both groups were more affected by wind in autumn than in spring. The songbirds' strategies involve elements of both drift and compensation, providing some benefits from wind in combination with destination and time control. In contrast, moths expose themselves to a significantly higher degree of drift in order to obtain strong wind assistance, surpassing the songbirds in mean ground speed, at the cost of a comparatively lower spatiotemporal migratory precision. Moths and songbirds show contrasting but adaptive responses to migrating through a moving flow, which are fine-tuned to the respective flight capabilities of each group in relation to the wind currents they travel within. PMID:26147535

  6. Financial incentives enhance adaptation to a sensorimotor transformation.

    PubMed

    Gajda, Kathrin; Sülzenbrück, Sandra; Heuer, Herbert

    2016-10-01

    Adaptation to sensorimotor transformations has received much attention in recent years. However, the role of motivation and its relation to the implicit and explicit processes underlying adaptation has been neglected thus far. Here, we examine the influence of extrinsic motivation on adaptation to a visuomotor rotation by way of providing financial incentives for accurate movements. Participants in the experimental group "bonus" received a defined amount of money for high end-point accuracy in a visuomotor rotation task; participants in the control group "no bonus" did not receive a financial incentive. Results showed better overall adaptation to the visuomotor transformation in participants who were extrinsically motivated. However, there was no beneficial effect of financial incentives on the implicit component, as assessed by the after-effects, and on separately assessed explicit knowledge. These findings suggest that the positive influence of financial incentives on adaptation is due to a component which cannot be measured by after-effects or by our test of explicit knowledge. A likely candidate is model-free learning based on reward-prediction errors, which could be enhanced by the financial bonuses. PMID:27271505

  7. The clinical use of contrast-enhanced ultrasound in the kidney.

    PubMed

    Tenant, Sean C; Gutteridge, Catherine M

    2016-05-01

    Traditional B-Mode and Doppler sonography have been the stalwart of renal tract imaging for many years, and indeed, are in daily use in most centres as the modality of choice for the initial assessment of renal pathology. However, traditional ultrasound scanning can be limited in its ability to accurately characterise renal pathology, and can be inaccurate at determining benign from malignant lesions. Contrast-enhanced ultrasound conveys many benefits, being safe (especially in patients with renal dysfunction), does not require the use of ionising radiation, is quick and relatively cheap and can help to establish whether a focal renal lesion is sinister. Furthermore, it is our experience that contrast-enhanced ultrasound is not a difficult technique to master for the experienced ultrasound practitioner. In this article, we discuss the technique, interpretation and value of contrast-enhanced ultrasound in renal imaging, and describe how we use it in our practice.

  8. [3D real time contrast enhanced ultrasonography,a new technique].

    PubMed

    Dietrich, C F

    2002-02-01

    While 3D sonography has become established in gynecology, abdominal applications have been mainly restricted to case reports. However, recent advances in computer technology have supported the development of new systems with motion detection methods and image registration algorithms - making it possible to acquire 3D data without position sensors, before and after administration of contrast enhancing agents. Hepatic (and also splenic) applications involve the topographic localization of masses in relation to the vessels, e.g. hepatic veins and portal vein branches prior to surgical procedures (segment localization). 3D imaging in the characterization of liver tumors after administration of contrast enhancing agents could become of special importance. We report on the first use of 3D imaging of the liver and spleen under real time conditions in 10 patients, using contrast enhanced phase inversion imaging with low mechanical index, which may improve the detection rate and characterization of liver and splenic tumors. PMID:11898076

  9. Hydrogen atom donor compounds as contrast enhancers for black-and-white photothermographic and thermographic elements

    DOEpatents

    Harring, Lori S.; Simpson, Sharon M.; Sansbury, Francis H.

    1997-01-01

    Hydrogen atom donor compounds are useful as contrast enhancers when used in combination with (i) hindered phenol developers, and (ii) trityl hydrazide and/or formyl-phenyl hydrazine co-developers, to produce ultra-high contrast black-and-white photothermographic and thermographic elements. The photothermographic and thermographic elements may be used as a photomask in a process where there is a subsequent exposure of an ultraviolet or short wavelength visible radiation-sensitive imageable medium.

  10. Segmentation methods for breast vasculature in dual-energy contrast-enhanced digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Lau, Kristen C.; Lee, Hyo Min; Singh, Tanushriya; Maidment, Andrew D. A.

    2015-03-01

    Dual-energy contrast-enhanced digital breast tomosynthesis (DE CE-DBT) uses an iodinated contrast agent to image the three-dimensional breast vasculature. The University of Pennsylvania has an ongoing DE CE-DBT clinical study in patients with known breast cancers. The breast is compressed continuously and imaged at four time points (1 pre-contrast; 3 post-contrast). DE images are obtained by a weighted logarithmic subtraction of the high-energy (HE) and low-energy (LE) image pairs. Temporal subtraction of the post-contrast DE images from the pre-contrast DE image is performed to analyze iodine uptake. Our previous work investigated image registration methods to correct for patient motion, enhancing the evaluation of vascular kinetics. In this project we investigate a segmentation algorithm which identifies blood vessels in the breast from our temporal DE subtraction images. Anisotropic diffusion filtering, Gabor filtering, and morphological filtering are used for the enhancement of vessel features. Vessel labeling methods are then used to distinguish vessel and background features successfully. Statistical and clinical evaluations of segmentation accuracy in DE-CBT images are ongoing.

  11. Non-contrast-enhanced Peripheral Angiography Using a Sliding Interleaved Cylinder Acquisition

    PubMed Central

    Kwon, Kie Tae; Kerr, Adam B.; Wu, Holden H.; Hu, Bob S.; Brittain, Jean H.; Nishimura, Dwight G.

    2014-01-01

    Purpose To develop a new sequence for non-contrast-enhanced peripheral angiography using a sliding interleaved cylinder (SLINCYL) acquisition. Methods A venous saturation pulse was incorporated into a 3D magnetization-prepared balanced steady-state free precession sequence for non-contrast-enhanced peripheral angiography to improve artery-vein contrast. The SLINCYL acquisition, which consists of a series of overlapped thin slabs for volumetric coverage similar to the original sliding interleaved ky (SLINKY) acquisition, was employed to evenly distribute the venous-suppression effects over the FOV. In addition, the thin-slab-scan nature of SLINCYL and the centric-ordered sampling geometry of its readout trajectory were exploited to implement efficient fluid-suppression and parallel imaging approaches. The sequence was tested in healthy subjects and a patient. Results Compared to a multiple overlapped thin slab acquisition, both SLINKY and SLINCYL suppressed the venetian blind artifacts and provided similar artery-vein contrast. However, SLINCYL achieved this with shorter scan times and less noticeable artifacts from k-space amplitude modulation than SLINKY. The fluid-suppression and parallel imaging schemes were also validated. A patient study using the SLINCYL-based sequence well identified stenoses at the super cial femoral arteries, which were also confirmed with digital subtraction angiography. Conclusion Non-contrast-enhanced angiography using SLINCYL can provide angiograms with improved artery-vein contrast in the lower extremities. PMID:25203505

  12. Contrast-enhanced ultrasonography: advance and current status in abdominal imaging

    PubMed Central

    2015-01-01

    In the field of contrast-enhanced ultrasonography (US), contrast agents are classified as either first- or second-generation agents depending on the gas within the microbubbles. In the case of first-generation contrast agents, a high-mechanical-index technique is used and only intermittent scanning is possible due to the early destruction of the microbubbles during the scanning. The use of second-generation contrast agents in a low-mechanical-index technique enables continuous scanning. Besides the detection and characterization of focal liver lesions, contrastenhanced US is helpful in the monitoring of radiofrequency ablation therapy and in the targeting step of an US-guided biopsy. Recently, there has been a demand for new criteria to evaluate the treatment response obtained using anti-angiogenic agents because morphologic criteria alone may not reflect the treatment response of the tumor and contrast-enhanced US can provide quantitative markers of tissue perfusion. In spite of the concerns related to its cost-effectiveness, contrast-enhanced US has the potential to be more widely used as a complimentary tool or to substitute the current imaging modalities in some occasions. PMID:25342120

  13. Enhanced contrast separation in scanning electron microscopes via a suspended-thin sample approach.

    PubMed

    Ji, Yuan; Wang, Li; Guo, Zhenxi; Wei, Bin; Zhao, Jie; Wang, Xiaodong; Zhang, Yinqi; Sui, Manling; Han, Xiaodong

    2014-11-01

    A suspended-thin-sample (STS) approach for signal selection and contrast separation is developed in scanning electron microscopes with commonly used primary beam energies and traditional detectors. Topography contrast, electron channeling contrast and composition contrast are separated and largely enhanced from suspended thin samples of several hundred nanometers in thickness, which is less than the escape depth of backscattered electrons. This imaging technique enables to detect relatively pure secondary electron and elastic backscattered electron singles, whereas suppress multiple inelastic scattering effects. The provided contrast features are different from those of bulk samples, which are largely mixed with inelastic scattering effects. The STS imaging concept and method could be expected to have more applications in distinguishing materials of nanostructures, multilayers, compounds and composites, as well as in SEM-based electron backscatter diffraction, cathodoluminesence, and x-ray microanalysis.

  14. Contrast-enhanced ultrasound imaging of the vasa vasorum of carotid artery plaque

    PubMed Central

    Song, Ze-Zhou; Zhang, Yan-Ming

    2015-01-01

    The vasa vasorum of carotid artery plaque is a novel marker of accurately evaluating the vulnerability of carotid artery plaque, which was associated with symptomatic cerebrovascular and cardiovascular disease. The presence of ultrasound contrast agents in carotid artery plaque represents the presence of the vasa vasorum in carotid artery plaque because the ultrasound contrast agents are strict intravascular tracers. Therefore, contrast-enhanced ultrasound (CEUS) is a novel and safe imaging modality for evaluating the vasa vasorum in carotid artery plaque. However, there are some issues that needs to be assessed to embody fully the clinical utility of the vasa vasorum in carotid artery plaque with CEUS. PMID:26120382

  15. Optical switching and contrast enhancement in intense laser systems by cascaded optical parametric amplification

    SciTech Connect

    Jovanovic, I; Haefner, C; Wattellier, B; Barty, C J

    2005-09-06

    Optical parametric chirped-pulse amplification (OPCPA) can be used to improve the prepulse contrast in chirped-pulse amplification systems by amplifying the main pulse with a total saturated OPCPA gain, while not affecting the preceding prepulses of the seed oscillator mode-locked pulse train. We show that a simple modification of a multistage OPCPA system into a cascaded optical parametric amplifier (COPA) results in an optical switch and extreme contrast enhancement which can completely eliminate the preceding and trailing oscillator pulses. Instrument-limited measurement of prepulse contrast ratio of 1.4 x 10{sup 11} is demonstrated from COPA at a 30-mJ level.

  16. Optical switching and contrast enhancement in intense laser systems by cascaded optical parametric amplification.

    PubMed

    Jovanovic, Igor; Barty, C P J; Haefner, Constantin; Wattellier, Benoit

    2006-03-15

    Optical parametric chirped-pulse amplification (OPCPA) can be used to improve the prepulse contrast in chirped-pulse amplification systems by amplifying the main pulse with a total saturated OPCPA gain, while not affecting the preceding prepulses of the seed oscillator mode-locked pulse train. We show that a simple modification of a multistage OPCPA system into a cascaded optical parametric amplifier (COPA) results in an optical switch and extreme contrast enhancement that can completely eliminate the preceding and trailing oscillator pulses. Instrument-limited measurement of a prepulse contrast ratio of 1.4 x 10(11) is demonstrated from COPA at a 30 mJ level.

  17. Resolution and contrast enhancement of subtractive second harmonic generation microscopy with a circularly polarized vortex beam

    PubMed Central

    Tian, Nian; Fu, Ling; Gu, Min

    2015-01-01

    We extend the subtractive imaging method to label-free second harmonic generation (SHG) microscopy to enhance the spatial resolution and contrast. This method is based on the intensity difference between two images obtained with circularly polarized Gaussian and doughnut-shaped beams, respectively. By characterizing the intensity and polarization distributions of the two focused beams, we verify the feasibility of the subtractive imaging method in polarization dependent SHG microscopy. The resolution and contrast enhancement in different biological samples is demonstrated. This work will open a new avenue for the applications of SHG microscopy in biomedical research. PMID:26364733

  18. Practical method and device for enhancing pulse contrast ratio for lasers and electron accelerators

    DOEpatents

    Zhang, Shukui; Wilson, Guy

    2014-09-23

    An apparatus and method for enhancing pulse contrast ratios for drive lasers and electron accelerators. The invention comprises a mechanical dual-shutter system wherein the shutters are placed sequentially in series in a laser beam path. Each shutter of the dual shutter system has an individually operated trigger for opening and closing the shutter. As the triggers are operated individually, the delay between opening and closing first shutter and opening and closing the second shutter is variable providing for variable differential time windows and enhancement of pulse contrast ratio.

  19. 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.

  20. Dynamic enhancement patterns of intrahepatic cholangiocarcinoma in cirrhosis on contrast-enhanced computed tomography: risk of misdiagnosis as hepatocellular carcinoma.

    PubMed

    Li, Rui; Cai, Ping; Ma, Kuan-Sheng; Ding, Shi-Yi; Guo, De-Yu; Yan, Xiao-Chu

    2016-01-01

    This study aimed to assess the features of intrahepatic cholangiocarcinoma (ICC) at computerized tomography (CT) and verify the risk of misdiagnosis of ICC as hepatocellular carcinoma (HCC) in cirrhosis. CT appearances of 98 histologically confirmed ICC nodules from 84 cirrhotic patients were retrospectively reviewed, taking into consideration the pattern and dynamic contrast uptake during the arterial, portal venous and delayed phases. During the arterial phase, 53 nodules (54.1%) showed peripheral rim-like enhancement, 35 (35.7%) hyperenhancement, 9 (9.2%) hypoenhancement and 1 (1.0%) isoenhancement. The ICC nodules showed heterogeneous dynamic contrast patterns, being progressive enhancement in 35 nodules (35.7%), stable enhancement in 28 nodules (28.6%), wash-in and wash-out pattern in 15 nodules (15.3%) and all other enhancement patterns in 20 nodules (20.4%). There were no significant differences in the dynamic vascular patterns of ICC according to nodule size (p > 0.05). ICC in cirrhosis has varied enhancement patterns at contrast-enhanced multiphase multidetector CT. Though the majority of ICC did not display typical radiological hallmarks of HCC, if dynamic CT scan was used as the sole modality for the non-invasive diagnosis of nodules in cirrhosis, the risk of misdiagnosis of ICC for HCC is not negligible.

  1. Adaptive optics for high-contrast imaging of faint substellar companions

    NASA Astrophysics Data System (ADS)

    Morzinski, Katie M.

    Direct imaging of faint objects around bright stars is challenging because the primary star's diffracted light can overwhelm low-mass companions. Nevertheless, advances in adaptive optics (AO) and high-contrast imaging have revealed the first pictures of extrasolar planets. In this dissertation I employ today's high-contrast AO techniques to image brown dwarfs around stars in the nearby Hyades cluster. Furthermore, I prepare for the next generation of high-contrast AO instrumentation, by qualifying MEMS deformable mirrors for wavefront control in the Gemini Planet Imager. In Part I, I present discovery of 3 new brown dwarfs and 36 low-mass stellar companions to 85 stars in the Hyades, imaged with AO at Keck and Lick Observatories. The "locally-optimized combination of images" (LOCI) image-diversity technique filters out the primary star to reveal faint companions. This survey is complete to the hydrogen-burning limit at separations beyond 20 AU. In the complete sample, multiplicity increases as primary star mass decreases. Additionally, the brown dwarfs are at wide >150 AU separations. Finding this preference for low binding-energy systems is an unexpected result, as the Hyades is 625 Myr old and dynamically relaxed. Future work will continue to explore this trend to understand the dynamical and star formation history of the Hyades. The brown dwarfs are near interesting transition regimes for low-mass objects; therefore, characterizing their atmospheres with spectrophotometry will serve as an important benchmark for our understanding of these cool objects. In Part II, I demonstrate micro-electro-mechanical systems (MEMS) deformable mirrors for high-order wavefront control in the Gemini Planet Imager (GPI). MEMS micromirrors have thousands of degrees of freedom and represent a significant cost efficiency over conventional glass deformable mirrors, making them ideal for high-contrast AO. In Chapter 7, I present experimental evidence that MEMS actuators function well

  2. Contrasted modes of evolution in the same genome: allozymes and adaptive change in Heliconius.

    PubMed

    Turner, J R; Johnson, M S; Eanes, W F

    1979-04-01

    Butterflies in the South American genus Heliconius have undergone a spectacular adaptive radiation (with convergent evolution between some lines) in their color patterns; this has been produced by natural selection for muellerian mimicry. The genetic basis of this radiation, shown by crossing highly differentiated races within two of the species, is homozygosity for alternative alleles at some half dozen loci. In complete contrast, allozyme loci in these butterflies are strongly heterozygous and show only frequency differences (never amounting to homozygosity of alternative alleles) between races; the amount of allozyme divergence is the same between races of H. erato and H. sara, although in color pattern the first forms marked races and the other does not. For the allozymes, there is a strong correlation over loci for rate of divergence between species and average heterozygosity. This is not true of the genes controlling color pattern. Heterozygosity of the enzymes is correlated with subunit molecular weight. Thus, different parts of the genome can evolve in different ways simultaneously; genes controlling color pattern in the "classical" mode, and allozymes in a different mode in which the rate of evolution is related to their heterozygosity (a "balance" or "neutral" mode).

  3. High contrast L' band adaptive optics imaging to detect extrasolar planets

    NASA Astrophysics Data System (ADS)

    Heinze, Ari; Hinz, Phil; Sivanandam, Suresh; Apai, Daniel; Meyer, Michael

    2006-06-01

    We are carrying out a survey to search for giant extrasolar planets around nearby, moderate-age stars in the mid-infrared L' and M bands (3.8 and 4.8 microns, respectively), using the Clio camera with the adaptive optics system on the MMT telescope. To date we have observed 7 stars, of a total 50 planned, including GJ 450 (distance about 8.55pc, age about 1 billion years, no real companions detected), which we use as our example here. We report the methods we use to obtain extremely high contrast imaging in L', and the performance we have obtained. We find that the rotation of a celestial object over time with respect to a telescope tracking it with an altazimuth mount can be a powerful tool for subtracting telescope-related stellar halo artifacts and detecting planets near bright stars. We have carried out a thorough Monte Carlo simulation demonstrating our ability to detect planets as small as 6 Jupiter masses around GJ 450. The division of a science data set into two independent parts, with companions required to be detected on both in order to be recognized as real, played a crucial role in detecting companions in this simulation. We mention also our discovery of a previously unknown faint stellar companion to another of our survey targets, HD 133002. Followup is needed to confirm this as a physical companion, and to determine its physical properties.

  4. Measurements of achromatic and chromatic contrast sensitivity functions for an extended range of adaptation luminance

    NASA Astrophysics Data System (ADS)

    Kim, Kil Joong; Mantiuk, Rafal; Lee, Kyoung Ho

    2013-03-01

    Inspired by the ModelFest and ColorFest data sets, a contrast sensitivity function was measured for a wide range of adapting luminance levels. The measurements were motivated by the need to collect visual performance data for natural viewing of static images at a broad range of luminance levels, such as can be found in the case of high dynamic range displays. The detection of sine-gratings with Gaussian envelope was measured for achromatic color axis (black to white), two chromatic axes (green to red and yellow-green to violet) and two mixed chromatic and achromatic axes (dark-green to light-pink, and dark yellow to light-blue). The background luminance varied from 0.02 to 200 cd/m2. The spatial frequency of the gratings varied from 0.125 to 16 cycles per degree. More than four observers participated in the experiments and they individually determined the detection threshold for each stimulus using at least 20 trials of the QUEST method. As compared to the popular CSF models, we observed higher sensitivity drop for higher frequencies and significant differences in sensitivities in the luminance range between 0.02 and 2 cd/m2. Our measurements for chromatic CSF show a significant drop in sensitivity with luminance, but little change in the shape of the CSF. The drop of sensitivity at high frequencies is significantly weaker than reported in other studies and assumed in most chromatic CSF models.

  5. SU-D-12A-02: DeTECT, a Method to Enhance Soft Tissue Contrast From Mega Voltage CT

    SciTech Connect

    Sheng, K; Gou, S; Qi, S

    2014-06-01

    Purpose: MVCT images have been used on TomoTherapy system to align patients based on bony anatomies but its usefulness for soft tissue registration, delineation and adaptive radiation therapy is severely limited due to minimal photoelectric interaction and prominent presence of noise resulting from low detector quantum efficiency of megavoltage x-rays. We aim to utilize a non-local means denoising method and texture analysis to recover the soft tissue information for MVCT. Methods: A block matching 3D (BM3D) algorithm was adapted to reduce the noise while keeping the texture information of the MVCT images. BM3D is an imaging denoising algorithm developed from non-local means methods. BM3D additionally creates 3D groups by stacking 2D patches by the order of similarity. 3D denoising operation is then performed. The resultant 3D group is inversely transformed back to 2D images. In this study, BM3D was applied to MVCT images of a CT quality phantom, a head and neck and a prostate patient. Following denoising, imaging texture was enhanced to create the denoised and texture enhanced CT (DeTECT). Results: The original MVCT images show prevalent noise and poor soft tissue contrast. By applying BM3D denoising and texture enhancement, all MVCT images show remarkable improvements. For the phantom, the contrast to noise ratio for the low contrast plug was improved from 2.2 to 13.1 without compromising line pair conspicuity. For the head and neck patient, the lymph nodes and vein in the carotid space inconspicuous in the original MVCT image becomes highly visible in DeTECT. For the prostate patient, the boundary between the bladder and the prostate in the original MVCT is successfully recovered. Both results are visually validated by kVCT images of the corresponding patients. Conclusion: DeTECT showed the promise to drastically improve the soft tissue contrast of MVCT for image guided radiotherapy and adaptive radiotherapy.

  6. Adaptive bilateral filter for sharpness enhancement and noise removal.

    PubMed

    Zhang, Buyue; Allebach, Jan P

    2008-05-01

    In this paper, we present the adaptive bilateral filter (ABF) for sharpness enhancement and noise removal. The ABF sharpens an image by increasing the slope of the edges without producing overshoot or undershoot. It is an approach to sharpness enhancement that is fundamentally different from the unsharp mask (USM). This new approach to slope restoration also differs significantly from previous slope restoration algorithms in that the ABF does not involve detection of edges or their orientation, or extraction of edge profiles. In the ABF, the edge slope is enhanced by transforming the histogram via a range filter with adaptive offset and width. The ABF is able to smooth the noise, while enhancing edges and textures in the image. The parameters of the ABF are optimized with a training procedure. ABF restored images are significantly sharper than those restored by the bilateral filter. Compared with an USM based sharpening method-the optimal unsharp mask (OUM), ABF restored edges are as sharp as those rendered by the OUM, but without the halo artifacts that appear in the OUM restored image. In terms of noise removal, ABF also outperforms the bilateral filter and the OUM. We demonstrate that ABF works well for both natural images and text images. PMID:18390373

  7. Use of computational fluid dynamics in the design of dynamic contrast enhanced imaging phantoms

    NASA Astrophysics Data System (ADS)

    Hariharan, Prasanna; Freed, Melanie; Myers, Matthew R.

    2013-09-01

    Phantoms for dynamic contrast enhanced (DCE) imaging modalities such as DCE computed tomography (DCE-CT) and DCE magnetic resonance imaging (DCE-MRI) are valuable tools for evaluating and comparing imaging systems. It is important for the contrast-agent distribution within the phantom to possess a time dependence that replicates a curve observed clinically, known as the ‘tumor-enhancement curve’. It is also important for the concentration field within the lesion to be as uniform as possible. This study demonstrates how computational fluid dynamics (CFD) can be applied to achieve these goals within design constraints. The distribution of the contrast agent within the simulated phantoms was investigated in relation to the influence of three factors of the phantom design. First, the interaction between the inlets and the uniformity of the contrast agent within the phantom was modeled. Second, pumps were programmed using a variety of schemes and the resultant dynamic uptake curves were compared to tumor-enhancement curves obtained from clinical data. Third, the effectiveness of pulsing the inlet flow rate to produce faster equilibration of the contrast-agent distribution was quantified. The models employed a spherical lesion and design constraints (lesion diameter, inlet-tube size and orientation, contrast-agent flow rates and fluid properties) taken from a recently published DCE-MRI phantom study. For DCE-MRI in breast cancer detection, where the target tumor-enhancement curve varies on the scale of hundreds of seconds, optimizing the number of inlet tubes and their orientation was found to be adequate for attaining concentration uniformity and reproducing the target tumor-enhancement curve. For DCE-CT in liver tumor detection, where the tumor-enhancement curve varies on a scale of tens of seconds, the use of an iterated inlet condition (programmed into the pump) enabled the phantom to reproduce the target tumor-enhancement curve within a few per cent beyond about

  8. 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.

  9. Contrast-enhanced harmonic endoscopic ultrasound imaging: Basic principles, present situation and future perspectives

    PubMed Central

    Alvarez-Sánchez, María-Victoria; Napoléon, Bertrand

    2014-01-01

    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. PMID:25400439

  10. Coronary artery calcium quantification from contrast enhanced CT using gemstone spectral imaging and material decomposition.

    PubMed

    Fuchs, Tobias A; Stehli, Julia; Dougoud, Svetlana; Sah, Bert-Ram; Bull, Sacha; Clerc, Olivier F; Possner, Mathias; Buechel, Ronny R; Gaemperli, Oliver; Kaufmann, Philipp A

    2014-10-01

    To explore the feasibility of coronary artery calcium (CAC) measurement from low-dose contrast enhanced coronary CT angiography (CCTA) as this may obviate the need for an unenhanced CT scan. 52 patients underwent unenhanced cardiac CT and prospectively ECG triggered contrast enhanced CCTA (Discovery HD 750, GE Healthcare, Milwaukee, WI, USA). The latter was acquired in single-source dual-energy mode [gemstone spectral imaging (GSI)]. Virtual unenhanced images were generated from GSI CCTA by monochromatic image reconstruction of 70 keV allowing selective iodine material suppression. CAC scores from virtual unenhanced CT were compared to standard unenhanced CT including a linear regression model. After iodine subtraction from the contrast enhanced CCTA the attenuation in the ascending aorta decreased significantly from 359 ± 61 to 54 ± 8 HU (P < 0.001), the latter comparing well to the value of 64 ± 55 HU found in the standard unenhanced CT (P = ns) confirming successful iodine subtraction. After introducing linear regression formula the mean values for Agatston, Volume and Mass scores of virtual unenhanced CT were 187 ± 321, 72 ± 114 mm(3), and 27 ± 46 mg/cm(3), comparing well to the values from standard unenhanced CT (187 ± 309, 72 ± 110 mm(3), and 27 ± 45 mg/cm(3)) yielding an excellent correlation (r = 0.96, r = 0.96, r = 0.92; P < 0.001). Mean estimated radiation dose revealed 0.83 ± 0.02 mSv from the unenhanced CT and 1.70 ± 0.53 mSv from the contrast enhanced CCTA. Single-source dual-energy scanning with GSI allows CAC quantification from low dose contrast enhanced CCTA by virtual iodine contrast subtraction.

  11. Hepatocellular Carcinoma Treated with Chemoembolization: Assessment with Contrast-Enhanced Doppler Ultrasonography

    SciTech Connect

    Catalano, Orlando; Esposito, Maria; Lobianco, Roberto; Cusati, Bianca; Altei, Francesco; Siani, Alfredo

    1999-11-15

    Purpose: To report our preliminary experience concerning the use of Doppler ultrasonography (DUS) techniques after intravenous injection of the galactose-based contrast agent Levovist in the assessment of hepatocellular carcinoma (HCC) treated with transcatheter arterial chemoembolization (TACE). The sonographic findings are correlated with those obtained using iodized oil (Lipiodol) helical computed tomography (CT). Methods: For 7 months we studied 28 patients with cirrhosis and HCC (a total of 43 nodules) who had undergone TACE between 18 and 30 days previously. The lesions were investigated with color Doppler ultrasonography (CDUS) and power Doppler ultrasonography (PDUS), before and after infusion of the echo-contrast agent (300 mg/ml, maximum 1 injection for each nodule, administered at constant velocity within 60-90 sec), and with helical Lipiodol-CT (0-7 days after DUS). In the retrospective analysis, special attention was given to the Doppler signals related to pulsatile intra- and perinodular flow and to the detection of new vessels after contrast agent injection. The signal intensity was graded as 0 (absent), 1 (low), 2 (medium), or 3 (high), while its distribution was classified as peripheral, central, or diffuse. Oily agent retention on CT scans was assessed as 0 (absent), I (<10%), II (<50%), III (>50%), or IV (homogeneous). These scores were awarded separately, without knowledge of the other judgments. Results: An hepatic global echo-enhancing effect was identified in all cases and always lasted long enough to allow an accurate analysis of all parenchymal lesions (at least 8 min). The signal scores could be evaluated in 39 of 43 HCCs, as follows: basal CDUS: grade 0 in 17 lesions, grade 1 in 16, grade 2 in 6; contrast-enhanced CDUS: grade 0 in 12 lesions, grade 1 in 10, grade 2 in 14, grade 3 in 3; basal PDUS: grade 0 in 15 lesions, grade 1 in 13, grade 2 in 9, grade 3 in 2; contrast-enhanced PDUS: grade 0 in 11 lesions, grade 1 in 9, grade 2 in 15

  12. Contrast adaptive total p-norm variation minimization approach to CT reconstruction for artifact reduction in reduced-view brain perfusion CT

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Won; Kim, Jong-Hyo

    2011-03-01

    Perfusion CT (PCT) examinations are getting more frequently used for diagnosis of acute brain diseases such as hemorrhage and infarction, because the functional map images it produces such as regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), and mean transit time (MTT) may provide critical information in the emergency work-up of patient care. However, a typical PCT scans the same slices several tens of times after injection of contrast agent, which leads to much increased radiation dose and is inevitability of growing concern for radiation-induced cancer risk. Reducing the number of views in projection in combination of TV minimization reconstruction technique is being regarded as an option for radiation reduction. However, reconstruction artifacts due to insufficient number of X-ray projections become problematic especially when high contrast enhancement signals are present or patient's motion occurred. In this study, we present a novel reconstruction technique using contrast-adaptive TpV minimization that can reduce reconstruction artifacts effectively by using different p-norms in high contrast and low contrast objects. In the proposed method, high contrast components are first reconstructed using thresholded projection data and low p-norm total variation to reflect sparseness in both projection and reconstruction spaces. Next, projection data are modified to contain only low contrast objects by creating projection data of reconstructed high contrast components and subtracting them from original projection data. Then, the low contrast projection data are reconstructed by using relatively high p-norm TV minimization technique, and are combined with the reconstructed high contrast component images to produce final reconstructed images. The proposed algorithm was applied to numerical phantom and a clinical data set of brain PCT exam, and the resultant images were compared with those using filtered back projection (FBP) and conventional TV

  13. The Use of Contrast-Enhanced Post Mortem CT in the Detection of Cardiovascular Deaths

    PubMed Central

    Penzkofer, Tobias; Kuhl, Christiane Katharina; Knüchel, Ruth; Mahnken, Andreas H.

    2014-01-01

    Objectives To evaluate the diagnostic value of contrast enhanced post mortem computed tomography (PMCT) in comparison to non-enhanced post mortem CT in the detection of cardiovascular causes of death (COD). Background As autopsy rates decline, new methods to determine CODs are necessary. So contrast enhanced PMCT shall be evaluated in comparison to established non-enhanced PMCT in order to further improve the method. Methods In a prospective study, 20 corpses were examined using a 64-row multisclice CT (MSCT) before and after intraarterial perfusion with a newly developed, barium-bearing contrast agent and ventilation of the lungs. The cause of death was determined in enhanced and unenhanced scans and a level of confidence (LOC) was given by three experienced radiologists on a scale between 0 and 4. Results were compared to autopsy results as gold standard. Autopsy was performed blinded to PMCT-findings. Results The method allowed visualization of different types of cause of death. There was a significant improvement in LOC in enhanced scans compared to unenhanced scans as well as an improvement in the detection of COD. The cause of death could be determined in 19 out of 20 patients. Conclusions PMCT is feasible and appears to be robust for diagnosing cardiovascular causes of death. When compared with unenhanced post-mortem CT intraarterial perfusion and pulmonary ventilation significantly improve visualization and diagnostic accuracy. These promising results warrant further studies. PMID:24759757

  14. Contrast-enhanced ultrasonography for the determination of Crohn’s disease activity – preliminary experience

    PubMed Central

    Białecki, Marcin; Białecka, Agnieszka; Laskowska, Katarzyna; Kłopocka, Maria; Liebert, Ariel; Lemanowicz, Adam; Serafin, Zbigniew

    2014-01-01

    Summary Background Contrast-enhanced ultrasound (CEUS) is a recent non-invasive modality, which may partially replace currently used techniques (endoscopy, CT enterography and MR enterography) in the diagnostics and assessment of Crohn’s disease (CD). The aim of the study was to analyze early experience in the use of CEUS for the measurement of activity and staging of CD. Material/Methods Eleven patients previously diagnosed with CD were included in the study. They underwent contrast-enhanced ultrasonography (SonoVue, Bracco), low-dose CT enterography (LDCTE), assessment of laboratory markers of inflammation and clinical CD activity index (CDAI). Contrast enhancement was evaluated using a semi-quantitative method and a quantitative method that included measurement of peak enhancement (PE), enhancement curve rise time (RT) and wash-in-rate (WiR). Results Ileal wall thickening was observed in all patients. Semi-quantitative method was used to observe CD activity in CEUS in 10 cases that perfectly matched LDCTE findings. There was a moderate positive correlation between PE and CDAI (r=0.65, p<0.001). There was no significant relationship between perfusion parameters and laboratory markers of inflammation. Conclusions CEUS is a promising modality for non-invasive assessment of pathologic ileal vascularization in the course of Crohn’s disease. Intensity of enhancement in CEUS reflects activity of the disease detected in LDCTE and correlates with CDAI. PMID:24723988

  15. High-resolution contrast-enhanced optical coherence tomography in mice retinae

    NASA Astrophysics Data System (ADS)

    Sen, Debasish; SoRelle, Elliott D.; Liba, Orly; Dalal, Roopa; Paulus, Yannis M.; Kim, Tae-Wan; Moshfeghi, Darius M.; de la Zerda, Adam

    2016-06-01

    Optical coherence tomography (OCT) is a noninvasive interferometric imaging modality providing anatomical information at depths of millimeters and a resolution of micrometers. Conventional OCT images limit our knowledge to anatomical structures alone, without any contrast enhancement. Therefore, here we have, for the first time, optimized an OCT-based contrast-enhanced imaging system for imaging single cells and blood vessels in vivo inside the living mouse retina at subnanomolar sensitivity. We used bioconjugated gold nanorods (GNRs) as exogenous OCT contrast agents. Specifically, we used anti-mouse CD45 coated GNRs to label mouse leukocytes and mPEG-coated GNRs to determine sensitivity of GNR detection in vivo inside mice retinae. We corroborated OCT observations with hyperspectral dark-field microscopy of formalin-fixed histological sections. Our results show that mouse leukocytes that otherwise do not produce OCT contrast can be labeled with GNRs leading to significant OCT intensity equivalent to a 0.5 nM GNR solution. Furthermore, GNRs injected intravenously can be detected inside retinal blood vessels at a sensitivity of ˜0.5 nM, and GNR-labeled cells injected intravenously can be detected inside retinal capillaries by enhanced OCT contrast. We envision the unprecedented resolution and sensitivity of functionalized GNRs coupled with OCT to be adopted for longitudinal studies of retinal disorders.

  16. High-resolution contrast-enhanced optical coherence tomography in mice retinae

    NASA Astrophysics Data System (ADS)

    Sen, Debasish; SoRelle, Elliott D.; Liba, Orly; Dalal, Roopa; Paulus, Yannis M.; Kim, Tae-Wan; Moshfeghi, Darius M.; de la Zerda, Adam

    2016-06-01

    Optical coherence tomography (OCT) is a noninvasive interferometric imaging modality providing anatomical information at depths of millimeters and a resolution of micrometers. Conventional OCT images limit our knowledge to anatomical structures alone, without any contrast enhancement. Therefore, here we have, for the first time, optimized an OCT-based contrast-enhanced imaging system for imaging single cells and blood vessels in vivo inside the living mouse retina at subnanomolar sensitivity. We used bioconjugated gold nanorods (GNRs) as exogenous OCT contrast agents. Specifically, we used anti-mouse CD45 coated GNRs to label mouse leukocytes and mPEG-coated GNRs to determine sensitivity of GNR detection in vivo inside mice retinae. We corroborated OCT observations with hyperspectral dark-field microscopy of formalin-fixed histological sections. Our results show that mouse leukocytes that otherwise do not produce OCT contrast can be labeled with GNRs leading to significant OCT intensity equivalent to a 0.5 nM GNR solution. Furthermore, GNRs injected intravenously can be detected inside retinal blood vessels at a sensitivity of ˜0.5 nM, and GNR-labeled cells injected intravenously can be detected inside retinal capillaries by enhanced OCT contrast. We envision the unprecedented resolution and sensitivity of functionalized GNRs coupled with OCT to be adopted for longitudinal studies of retinal disorders.

  17. Contrast-enhanced ultrasound in differentiating malignant from benign portal vein thrombosis in hepatocellular carcinoma

    PubMed Central

    Tarantino, Luciano; Ambrosino, Pasquale; Di Minno, Matteo Nicola Dario

    2015-01-01

    Portal vein thrombosis (PVT) may occur in liver cirrhosis patients. Malignant PVT is a common complication in cirrhotic patients with concomitant hepatocellular carcinoma (HCC) and, in some cases, it may be even the initial sign of an undetected HCC. Detection of malignant PVT in a patient with liver cirrhosis heavily affects the therapeutic strategy. Gray-scale ultrasound (US) is widely unreliable for differentiating benign and malignant thrombi. Although effective for this differential diagnosis, fine-needle biopsy remains an invasive technique. Sensitivity of color-doppler US in detection of malignant thrombi is highly dependent on the size of the thrombus. Contrast-enhanced computed tomography (CT) and contrast-enhanced magnetic resonance (MRI) can be useful to assess the nature of portal thrombus, while limited data are currently available about the role of positron emission tomography (PET) and PET-CT. In contrast with CT, MRI, PET, and PET-CT, contrast-enhanced ultrasound (CEUS) is a fast, effective, well tolerated and cheap technique, that can be performed even in the same session in which the thrombus has been detected. CEUS can be performed bedside and can be available also in transplanted patients. Moreover, CT and MRI only yield a snapshot analysis during contrast diffusion, while CEUS allows for a continuous real-time imaging of the microcirculation that lasts several minutes, so that the whole arterial phase and the late parenchymal phase of the contrast diffusion can be analyzed continuously by real-time US scanning. Continuous real-time monitoring of contrast diffusion entails an easy detection of thrombus maximum enhancement. Moreover, continuous quantitative analyses of enhancement (wash in - wash out studies) by CEUS during contrast diffusion is nowadays available in most CEUS machines, thus giving a more sophisticated and accurate evaluation of the contrast distribution and an increased confidence in diagnosis in difficult cases. In conclusion

  18. Automatic hyperspectral camera for latent fingerprint detection and contrast enhancement. Final report, September 2, 1998 - March 17, 1999

    SciTech Connect

    Paul Shnitser

    1999-06-01

    Physical Optics Corporation demonstrated the feasibility of the contrast enhancement of the latent fingerprint by portable hyperspectral imaging camera. The demonstrated non-contact technology is applicable for observation of the low contrast laser excited fluorescence from latent fingerprints as well as for the contrast enhancement of chemically processed fingerprints. Experiments were conducted with fingerprints on various types of substrates.

  19. Discrimination Training of Phonemic Contrasts Enhances Phonological Processing in Mainstream School Children

    ERIC Educational Resources Information Center

    Moore, D.R.; Rosenberg, J.F.; Coleman, J.S.

    2005-01-01

    Auditory perceptual learning has been proposed as effective for remediating impaired language and for enhancing normal language development. We examined the effect of phonemic contrast discrimination training on the discrimination of whole words and on phonological awareness in 8- to 10-year-old mainstream school children. Eleven phonemic contrast…

  20. Contrast-enhanced ultrasound in the evaluation of parotid gland lesions: an update of the literature.

    PubMed

    David, E; Cantisani, V; De Vincentiis, M; Sidhu, P S; Greco, A; Tombolini, M; Drudi, F M; Messineo, D; Gigli, S; Rubini, A; Fresilli, D; Ferrari, D; Flammia, F; D'Ambrosio, F

    2016-05-01

    High-resolution ultrasound is the first line examination for parotid gland diffuse disease and focal lesions, normally using grey-scale and colour-Doppler ultrasound. Unfortunately, grey-scale and colour-Doppler ultrasound features of benign and malignant salivary gland lesions may overlap, particularly with benign tumors, where pleomorphic adenomas are often indistinguishable from malignant lesions. With atypical lesions, contrast-enhanced magnetic resonance imaging is usually the second level imaging modality requested. The introduction of ultrasound contrast agents has opened further possible perspectives to improve the interpretation of parotid diseases, particularly the differentiation between benign and malignant lesions. We present a review of the current literature on contrast-enhanced ultrasound for the assessment of parotid gland lesions, considering all characteristics of the technique, evidence of usefulness, future perspectives and limitations.

  1. Contrast enhancement in dense breast images to aid clustered microcalcifications detection.

    PubMed

    Nunes, Fátima L S; Schiabel, Homero; Goes, Claudio E

    2007-03-01

    This paper presents a method to provide contrast enhancement in dense breast digitized images, which are difficult cases in testing of computer-aided diagnosis (CAD) schemes. Three techniques were developed, and data from each method were combined to provide a better result in relation to detection of clustered microcalcifications. Results obtained during the tests indicated that, by combining all the developed techniques, it is possible to improve the performance of a processing scheme designed to detect microcalcification clusters. It also allows operators to distinguish some of these structures in low-contrast images, which were not detected via conventional processing before the contrast enhancement. This investigation shows the possibility of improving CAD schemes for better detection of microcalcifications in dense breast images.

  2. Contrast-enhanced ultrasound for the evaluation of acute renal infarction.

    PubMed

    Miyoshi, Toru; Okayama, Hideki; Hiasa, Go; Kawata, Yoshitaka; Yamada, Tadakatsu; Kazatani, Yukio

    2016-01-01

    A 65-year-old male in the dilated phase of hypertrophic cardiomyopathy and with persistent atrial fibrillation was admitted to our hospital because of an episode of ventricular fibrillation following an appropriate shock from an implantable cardiac defibrillator (ICD). At admission, electrocardiography showed a normal sinus rhythm. He had complained of back pain 7 days after the ICD shock. Renal infarction was suspected, although computed tomography and magnetic resonance imaging could not be performed because of chronic renal failure and the presence of his ICD. We, therefore, used contrast-enhanced ultrasonography with a contrast agent to evaluate his acute kidney injury. This showed the left kidney contained a wedge-shaped area that was not enhanced by the contrast agent, indicating an area of infarction.

  3. Nonlinear contrast enhancement in photoacoustic molecular imaging with gold nanosphere encapsulated nanoemulsions

    SciTech Connect

    Wei, Chen-wei; Lombardo, Michael; Larson-Smith, Kjersta; Perez, Camilo; Xia, Jinjun; Matula, Thomas; Pozzo, Danilo; O'Donnell, Matthew; Pelivanov, Ivan

    2014-01-20

    A composite contrast agent, a nanoemulsion bead with assembled gold nanospheres at the interface, is proposed to improve the specific contrast of photoacoustic molecular imaging. A phase transition in the bead's core is induced by absorption of a nanosecond laser pulse with a fairly low laser fluence (∼3.5 mJ/cm{sup 2}), creating a transient microbubble through dramatically enhanced thermal expansion. This generates nonlinear photoacoustic signals with more than 10 times larger amplitude compared to that of a linear agent with the same optical absorption. By applying a differential scheme similar to ultrasound pulse inversion, more than 40 dB contrast enhancement is demonstrated with suppression of background signals.

  4. Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT): experimental validation with a dynamic phantom

    PubMed Central

    Unlu, Mehmet Burcin; Lin, Yuting; Gulsen, Gultekin

    2010-01-01

    Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT) can provide spatially resolved enhancement kinetics of an optical contrast agent. We undertook a systematic phantom study to evaluate the effects of the geometrical parameters such as the depth and size of the inclusion as well as the optical parameters of the background on the recovered enhancement kinetics of the most commonly used optical contrast agent, indocyanine green (ICG). For this purpose a computer-controlled dynamic phantom was constructed. An ICG–intralipid–water mixture was circulated through the inclusions while the DCE-DOT measurements were acquired with a temporal resolution of 16 s. The same dynamic study was repeated using inclusions of different sizes located at different depths. In addition to this, the effect of non-scattering regions was investigated by placing a second inclusion filled with water in the background. The phantom studies confirmed that although the peak enhancement varied substantially for each case, the recovered injection and dilution rates obtained from the percentage enhancement maps agreed within 15% independent of not only the depth and the size of the inclusion but also the presence of a non-scattering region in the background. Although no internal structural information was used in these phantom studies, it may be necessary to use it for small objects buried deep in tissue. However, the different contrast mechanisms of optical and other imaging modalities as well as imperfect co-registration between both modalities may lead to potential errors in the structural a priori. Therefore, the effect of erroneous selection of structural priors was investigated as the final step. Again, the injection and dilution rates obtained from the percentage enhancement maps were also immune to the systematic errors introduced by erroneous selection of the structural priors, e.g. choosing the diameter of the inclusion 20% smaller increased the peak enhancement 60% but

  5. System and method for 3-D/3-D registration between non-contrast-enhanced CBCT and contrast-enhanced CT for abdominal aortic aneurysm stenting.

    PubMed

    Miao, Shun; Liao, Rui; Pfister, Marcus; Zhang, Li; Ordy, Vincent

    2013-01-01

    In this paper, we present an image guidance system for abdominal aortic aneurysm stenting, which brings pre-operative 3-D computed tomography (CT) into the operating room by registering it against intra-operative non-contrast-enhanced cone-beam CT (CBCT). Registration between CT and CBCT volumes is a challenging task due to two factors: the relatively low signal-to-noise ratio of the abdominal aorta in CBCT without contrast enhancement, and the drastically different field of view between the two image modalities. The proposed automatic registration method handles the first issue through a fast quasi-global search utilizing surrogate 2-D images, and solves the second problem by relying on neighboring dominant structures of the abdominal aorta (i.e. the spine) for initial coarse alignment, and using a confined and image-processed volume of interest around the abdominal aorta for fine registration. The proposed method is validated offline using 17 clinical datasets, and achieves 1.48 mm target registration error and 100% success rate in 2.83 s. The prototype system has been installed in hospitals for clinical trial and applied in around 30 clinical cases, with 100% success rate reported qualitatively. PMID:24505689

  6. Diagnostic Accuracy of Dynamic Contrast Enhanced Magnetic Resonance Imaging in Characterizing Lung Masses

    PubMed Central

    Inan, Nagihan; Arslan, Arzu; Donmez, Muhammed; Sarisoy, Hasan Tahsin

    2016-01-01

    Background Imaging plays a critical role not only in the detection, but also in the characterization of lung masses as benign or malignant. Objectives To determine the diagnostic accuracy of dynamic magnetic resonance imaging (MRI) in the differential diagnosis of benign and malignant lung masses. Patients and Methods Ninety-four masses were included in this prospective study. Five dynamic series of T1-weighted spoiled gradient echo (FFE) images were obtained, followed by a T1-weighted FFE sequence in the late phase (5th minutes). Contrast enhancement patterns in the early (25th second) and late (5th minute) phase images were evaluated. For the quantitative evaluation, signal intensity (SI)-time curves were obtained and the maximum relative enhancement, wash-in rate, and time-to-peak enhancement of masses in both groups were calculated. Results The early phase contrast enhancement patterns were homogeneous in 78.2% of the benign masses, while heterogeneous in 74.4% of the malignant tumors. On the late phase images, 70.8% of the benign masses showed homogeneous enhancement, while most of the malignant masses showed heterogeneous enhancement (82.4%). During the first pass, the maximum relative enhancement and wash-in rate values of malignant masses were significantly higher than those of the benign masses (P = 0.03 and 0.04, respectively). The cutoff value at 15% yielded a sensitivity of 85.4%, specificity of 61.2%, and positive predictive value of 68.7% for the maximum relative enhancement. Conclusion Contrast enhancement patterns and SI-time curve analysis of MRI are helpful in the differential diagnosis of benign and malignant lung masses. PMID:27703654

  7. What do we know about brain contrast enhancement patterns in neuromyelitis optica?☆

    PubMed Central

    Pekcevik, Yeliz; Orman, Gunes; Lee, In Ho; Mealy, Maureen A.; Levy, Michael; Izbudak, Izlem

    2016-01-01

    Neuromyelitis optica (NMO) is an autoimmune disorder of the central nervous system that usually presents with acute myelitis and/or optic neuritis. Recently, some brain magnetic resonance imaging findings have been described in NMO that are important in the differential diagnosis. Pencil-thin, leptomeningeal, and cloud-like enhancement may be specific to NMO. These patterns are usually seen during relapses. Recognizing these lesions and enhancement patterns may expedite the diagnosis and allows early effective treatment. The purpose of this article is to review the latest knowledge and to share our experience with the contrast enhancement patterns of NMO brain lesions. PMID:26615899

  8. Cardiac Amyloidosis: Typical Imaging Findings and Diffuse Myocardial Damage Demonstrated by Delayed Contrast-Enhanced MRI

    SciTech Connect

    Sueyoshi, Eijun Sakamoto, Ichiro; Okimoto, Tomoaki; Hayashi, Kuniaki; Tanaka, Kyouei; Toda, Genji

    2006-08-15

    Amyloidosis is a rare systemic disease. However, involvement of the heart is a common finding and is the most frequent cause of death in amyloidosis. We report the sonographic, scintigraphic, and MRI features of a pathologically proven case of cardiac amyloidosis. Delayed contrast-enhanced MR images, using an inversion recovery prepped gradient-echo sequence, revealed diffuse enhancement in the wall of both left and right ventricles. This enhancement suggested expansion of the extracellular space of the myocardium caused by diffuse myocardial necrosis secondary to deposition of amyloid.

  9. NOTE Contrast enhancement of EPID images via difference imaging: a feasibility study

    NASA Astrophysics Data System (ADS)

    Kairn, T.; Khoei, S.; Markwell, T. S.; Fielding, A. L.; Trapp, J. V.

    2010-11-01

    In this study, the feasibility of difference imaging for improving the contrast of electronic portal imaging device (EPID) images is investigated. The difference imaging technique consists of the acquisition of two EPID images (with and without the placement of an additional layer of attenuating medium on the surface of the EPID) and the subtraction of one of these images from the other. The resulting difference image shows improved contrast, compared to a standard EPID image, since it is generated by lower-energy photons. Results of this study show that, firstly, this method can produce images exhibiting greater contrast than is seen in standard megavoltage EPID images and secondly, the optimal thickness of attenuating material for producing a maximum contrast enhancement may vary with phantom thickness and composition. Further studies of the possibilities and limitations of the difference imaging technique, and the physics behind it, are therefore recommended.

  10. Blood flow contrast enhancement in optical coherence tomography using microbubbles: a phantom study

    NASA Astrophysics Data System (ADS)

    Assadi, Homa; Demidov, Valentin; Karshafian, Raffi; Douplik, Alexandre; Vitkin, I. Alex

    2016-03-01

    In this study gas microbubbles are investigated as intravascular OCT contrast agents. Agar+Intralipid scattering tissue-like phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood and microbubbles. Swept-source structural and speckle variance OCT images, as well as speckle decorrelation times, were evaluated under both stationary and flow conditions. Faster decorrelation times and higher image contrast were detected in the presence of microbubbles in all experiments, and the effect was largest for speckle variance OCT ~2.3x greater contrast under flow conditions. The feasibility of utilizing microbubbles for tissue hemodynamic investigations and for microvasculature contrast enhancement in OCT angiography thus appears promising.

  11. Evaluation of the potential utility of flat panel CT for quantifying relative contrast enhancement

    SciTech Connect

    Jones, A. Kyle; Mahvash, Armeen

    2012-07-15

    Purpose: Certain directed oncologic therapies seek to take advantage of the fact that tumors are typically more susceptible to directed therapeutic agents than normal tissue owing to their extensive networks of poorly formed, leaky vasculature. If differences between the vascularity of normal and tumor tissues could be quantified, patients could be selected for or excluded from directed treatments on the basis of this difference. However, angiographic imaging techniques such as digital subtraction angiography (DSA) yield two-dimensional data that may be inadequate for this task. As a first step, the authors evaluated the feasibility of using a commercial implementation of flat panel computed tomography (FPCT) to quantify differences in enhancement of a simulated tumor compared with normal tissue based on differences in CT number measured in precontrast and postcontrast scans. Methods: To evaluate the FPCT scanner studied, the authors scanned several phantoms containing simulated normal and tumor tissues. In the first experiment, the authors used an anthropomorphic phantom containing inclusions representing normal, tumor, and bone tissue to evaluate the constancy of CT numbers in scans repeated at clinically relevant intervals of 1 and 3 min. The authors then scanned gelatin phantoms containing dilutions of iodinated contrast to evaluate the accuracy of relative contrast enhancement measurements for a clinical FPCT system. Data were analyzed using widely available software. Results: CT numbers measured in identical locations were constant over both scan intervals evaluated. Measured relative contrast enhancement values were accurate compared with known relative contrast enhancement values. Care must be taken to avoid artifacts in reconstructed images when placing regions of interest. Conclusions: Despite its limitations, FPCT in the interventional laboratory can be used to quantify relative contrast enhancement in phantoms. This is accomplished by measuring CT

  12. Contrast-enhanced ultrasonographic characteristics of adrenal glands in dogs with pituitary-dependent hyperadrenocorticism.

    PubMed

    Bargellini, Paolo; Orlandi, Riccardo; Paloni, Chiara; Rubini, Giuseppe; Fonti, Paolo; Peterson, Mark E; Boiti, Cristiano

    2013-01-01

    A noninvasive method for quantifying adrenal gland vascular patterns could be helpful for improving detection of adrenal gland disease in dogs. The purpose of this retrospective study was to compare the contrast-enhanced ultrasound (CEUS) characteristics of adrenal glands in 18 dogs with pituitary-dependent hyperadrenocorticism (PDH) vs. four clinically healthy dogs. Each dog received a bolus of the contrast agent (SonoVue®, 0.03 ml/kg of body weight) into the cephalic vein, immediately followed by a 5 ml saline flush. Dynamic contrast enhancement was analyzed using time-intensity curves in two regions of interest drawn manually in the caudal part of the adrenal cortex and medulla, respectively. In healthy dogs, contrast enhancement distribution was homogeneous and exhibited increased intensity from the medulla to the cortex. In the washout phase, there was a gradual and homogeneous decrease of enhancement of the adrenal gland. For all dogs with PDH, there was rapid, chaotic, and simultaneous contrast enhancement in both the medulla and cortex. Three distinct perfusion patterns were observed. Peak perfusion intensity was approximately twice as high (P < 0.05) in dogs with PDH compared with that of healthy dogs (28.90 ± 10.36 vs. 48.47 ± 15.28, respectively). In dogs with PDH, adrenal blood flow and blood volume values were approximately two- to fourfold (P < 0.05) greater than those of controls. Findings from the present study support the use of CEUS as a clinical tool for characterizing canine adrenal gland disease based on changes in vascular patterns.

  13. Contrast-enhancing computed tomography ring in glioblastoma multiforme after intraoperative endocurietherapy

    SciTech Connect

    Kumar, P.P.; Good, R.R.; Jones, E.O.; Skultety, F.M.; Leibrock, L.G.; McComb, R.D.

    1988-05-01

    The significance of the contrast-enhancing ring seen on serial follow-up postirradiation computed tomograms (CT) of the brain was evaluated in a group of 41 patients with glioblastoma multiforme (GM) who were treated in a phase I/II study by means of intraoperative remote afterloading endocurietherapy (ECT) with a high activity cobalt 60 probe (20.00 Gy) in one high-dose rate fraction), and conventional fractionated external-beam (EXRT) radiotherapy (60.00 Gy in 30 fractions in 7.5 weeks). All received minimum total tumor doses of 80.00 Gy. After completion of treatment, all patients were followed with serial CT scans of the brain. Two to 6 months after treatment, 27 of 41 patients developed the similar thin-walled, regular, contrast-enhancing CT rings with low-density attenuation inside and outside the ring. Postmortem study in two of these patients revealed that the thin-walled, regular, contrast-enhancing ring represented a continuous capsule of dilated cerebral vessels with inner low-density attenuation corresponding to necrosis, and outer low-density attenuation corresponding to edema. The CT appearance of the thin-walled, regular, contrast-enhancing ring produced after high-dose rate intraoperative ECT and EXRT is distinctly different from the CT ring characteristic of untreated or recurrent GM. After high-dose rate intracranial ECT and EXRT, the appearance of a post-ECT contrast-enhancing CT ring should not be automatically interpreted as recurrent disease as previously reported after conventional fractionated EXRT.

  14. Segmentation and classification of breast tumor using dynamic contrast-enhanced MR images.

    PubMed

    Zheng, Yuanjie; Baloch, Sajjad; Englander, Sarah; Schnall, Mitchell D; Shen, Dinggang

    2007-01-01

    Accuracy of automatic cancer diagnosis is largely determined by two factors, namely, the precision of tumor segmentation, and the suitability of extracted features for discrimination between malignancy and benignancy. In this paper, we propose a new framework for accurate characterization of tumors in contrast enhanced MR images. First, a new graph cut based segmentation algorithm is developed for refining coarse manual segmentation, which allows precise identification of tumor regions. Second, by considering serial contrast-enhanced images as a single spatio-temporal image, a spatio-temporal model of segmented tumor is constructed to extract Spatio-Temporal Enhancement Patterns (STEPs). STEPs are designed to capture not only dynamic enhancement and architectural features, but also spatial variations of pixel-wise temporal enhancement of the tumor. While temporal enhancement features are extracted through Fourier transform, the resulting STEP framework captures spatial patterns of temporal enhancement features via moment invariants and rotation invariant Gabor textures. High accuracy of the proposed framework is a direct consequence of this two pronged approach, which is validated through experiments yielding, for instance, an area of 0.97 under the ROC curve.

  15. Contrast enhancement of bite mark images using the grayscale mixer in ACR in Photoshop®.

    PubMed

    Evans, Sam; Noorbhai, Suzanne; Lawson, Zoe; Stacey-Jones, Seren; Carabott, Romina

    2013-05-01

    Enhanced images may improve bite mark edge definition, assisting forensic analysis. Current contrast enhancement involves color extraction, viewing layered images by channel. A novel technique, producing a single enhanced image using the grayscale mix panel within Adobe Camera Raw®, has been developed and assessed here, allowing adjustments of multiple color channels simultaneously. Stage 1 measured RGB values in 72 versions of a color chart image; eight sliders in Photoshop® were adjusted at 25% intervals, all corresponding colors affected. Stage 2 used a bite mark image, and found only red, orange, and yellow sliders had discernable effects. Stage 3 assessed modality preference between color, grayscale, and enhanced images; on average, the 22 survey participants chose the enhanced image as better defined for nine out of 10 bite marks. The study has shown potential benefits for this new technique. However, further research is needed before use in the analysis of bite marks.

  16. Enhancing stakeholder participation in land-based adaptation to environmental change with photo elicitation and photovoice

    NASA Astrophysics Data System (ADS)

    Orr, Barron; Kong, Taryn; Kellner, Klaus

    2015-04-01

    Land degradation is one of the main environmental changes confronting South Africa. Active participation from local land users to adopt land-based adaptation to land degradation is necessary for at least two obvious reasons. Firstly, most of the lands in South Africa are privately owned. Secondly, the costs for adapting to land degradation are substantial and are not feasible for an individual entity to afford. Land-based adaptation includes management practices that can reduce the vulnerability of land users to the threats posed by land degradation. To engage land users to participate in land-based adaptation, approaches to allow diverse stakeholders to effectively communicate their observations, knowledge and perspectives are needed. In addition to semi-structured interviews, photo elicitation and photovoice were implemented to engage 25 local livestock farmers from two rural areas in the South African Kalahari - Mier and Molopo - in a participatory research project. The results showed that photo elicitation enhanced stakeholder interaction relative to semi-structured interviews in a number of ways. Firstly, photo elicitation provided more details and new information beyond those in semi-structured interviews. Secondly, photo elicitation also allowed stakeholders to more easily communicate personal or concrete examples, comparisons, contrasts, explanatory information, attitudes and values. The results also showed that photovoice created opportunities for mutual learning among the participants. These enhancements have the potential to improve co-production of knowledge and quality of stakeholder engagement. Improvement in stakeholder engagement can in turn contribute toward land-based adaptation that is more locally relevant and a greater degree of translation of scientific advancement into actual adaptation practices.

  17. Contrast-enhanced multiple-phase imaging features in hepatic epithelioid hemangioendothelioma

    PubMed Central

    Chen, Ying; Yu, Ri-Sheng; Qiu, Ling-Ling; Jiang, Ding-Yao; Tan, Yan-Bin; Fu, Yan-Biao

    2011-01-01

    AIM: To investigate and review the contrast-enhanced multiple-phase computed tomography (CEMP CT) and magnetic resonance imaging (MRI) findings in patients with pathologically confirmed hepatic epithelioid hemangioendothelioma (HEHE). METHODS: Findings from imaging examinations in 8 patients (5 women and 3 men) with pathologically confirmed HEHE were retrospectively reviewed (CT images obtained from 7 patients and MR images obtained from 6 patients). The age of presentation varied from 27 years to 60 years (average age 39.8 years). RESULTS: There were two types of HEHE: multifocal type (n = 7) and diffuse type (n = 1). In the multifocal-type cases, there were 74 lesions on CT and 28 lesions on MRI with 7 lesions found with diffusion weighted imaging; 18 (24.3%) of 74 lesions on plain CT and 26 (92.9%) of 28 lesions on pre-contrast MRI showed the target sign. On CEMP CT, 28 (37.8%) of 74 lesions appeared with the target sign and a progressive-enhancement rim and 9 (12.2%) of 74 lesions displayed progressive enhancement, maintaining a state of persistent enhancement. On CEMP MRI, 27 (96.4%) of 28 lesions appeared with the target sign with a progressive-enhancement rim and 28 (100%) of 28 lesions displayed progressive-enhancement, maintaining a state of persistent enhancement. In the diffuse-type cases, an enlarged liver was observed with a large nodule appearing with persistent enhancement on CEMP CT and MRI. CONCLUSION: The most important imaging features of HEHE are the target sign and/or progressive enhancement with persistent enhancement on CEMP CT and MRI. MRI is advantageous over CT in displaying these imaging features. PMID:21941423

  18. Combined Dynamic Contrast Enhanced Liver MRI and MRA Using Interleaved Variable Density Sampling

    PubMed Central

    Rahimi, Mahdi Salmani; Korosec, Frank R.; Wang, Kang; Holmes, James H.; Motosugi, Utaroh; Bannas, Peter; Reeder, Scott B.

    2014-01-01

    Purpose To develop and evaluate a method for volumetric contrast-enhanced MR imaging of the liver, with high spatial and temporal resolutions, for combined dynamic imaging and MR angiography using a single injection of contrast. Methods An interleaved variable density (IVD) undersampling pattern was implemented in combination with a real-time-triggered, time-resolved, dual-echo 3D spoiled gradient echo sequence. Parallel imaging autocalibration lines were acquired only once during the first time-frame. Imaging was performed in ten subjects with focal nodular hyperplasia (FNH) and compared with their clinical MRI. The angiographic phase of the proposed method was compared to a dedicated MR angiogram acquired during a second injection of contrast. Results A total of 21 FNH, 3 cavernous hemangiomas, and 109 arterial segments were visualized in 10 subjects. The temporally-resolved images depicted the characteristic arterial enhancement pattern of the lesions with a 4 s update rate. Images were graded as having significantly higher quality compared to the clinical MRI. Angiograms produced from the IVD method provided non-inferior diagnostic assessment compared to the dedicated MRA. Conclusion Using an undersampled IVD imaging method, we have demonstrated the feasibility of obtaining high spatial and temporal resolution dynamic contrast-enhanced imaging and simultaneous MRA of the liver. PMID:24639130

  19. Near-infrared dye-loaded magnetic nanoparticles as photoacoustic contrast agent for enhanced tumor imaging

    PubMed Central

    Gao, Chuang; Deng, Zi-Jian; Peng, Dong; Jin, Yu-Shen; Ma, Yan; Li, Yan-Yan; Zhu, Yu-Kun; Xi, Jian-Zhong; Tian, Jie; Dai, Zhi-Fei; Li, Chang-Hui; Liang, Xiao-Long

    2016-01-01

    Objective: Photoacoustic (PA) tomography (PAT) has attracted extensive interest because of its optical absorption contrast and ultrasonic detection. This study aims to develop a biocompatible and biodegradable PA contrast agent particularly promising for clinical applications in human body. Methods: In this study, we presented a PA contrast agent: 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine- N-[methoxy (polyethylene glycol)] (DSPE-PEG)-coated superparamagnetic iron oxide (SPIO) nanoparticles (NPs) loaded with indocyanine green (ICG). We used ICG and SPIO NPs because both drugs are approved by the U.S. Food and Drug Administration. Given the strong absorption of near-infrared laser pulses, SPIO@DSPE-PEG/ICG NPs with a uniform diameter of ~28 nm could significantly enhance PA signals. Results: We demonstrated the contrast enhancement of these NPs in phantom and animal experiments, in which the in vivo circulation time of SPIO@DSPE-PEG/ICG NPs was considerably longer than that of free ICG. These novel NPs also displayed a high efficiency of tumor targeting. Conclusions: SPIO@DSPE-PEG/ICG NPs are promising PAT contrast agents for clinical applications. PMID:27807502

  20. Preliminary studies of enhanced contrast radiography in anatomy and embryology of insects with Elettra synchrotron light

    NASA Astrophysics Data System (ADS)

    Hönnicke, M. G.; Foerster, L. A.; Navarro-Silva, M. A.; Menk, R.-H.; Rigon, L.; Cusatis, C.

    2005-08-01

    Enhanced contrast X-ray imaging is achieved by exploiting the real part of the refraction index, which is responsible for the phase shifts, in addition to the imaginary part, which is responsible for the absorption. Such techniques are called X-ray phase contrast imaging. An analyzer-based X-ray phase contrast imaging set-up with Diffraction Enhanced Imaging processing (DEI) were used for preliminary studies in anatomy and embryology of insects. Parasitized stinkbug and moth eggs used as control agents of pests in vegetables and adult stinkbugs and mosquitoes ( Aedes aegypti) were used as samples. The experimental setup was mounted in the SYRMEP beamline at ELETTRA. Images were obtained using a high spatial resolution CCD detector (pixel size 14×14 μm 2) coupled with magnifying optics. Analyzer-based X-ray phase contrast images (PCI) and edge detection images show contrast and details not observed with conventional synchrotron radiography and open the possibility for future study in the embryonic development of insects.

  1. Spatial structure enhanced cooperation in dissatisfied adaptive snowdrift game

    NASA Astrophysics Data System (ADS)

    Zhang, Wen; Xu, Chen; Hui, Pak Ming

    2013-05-01

    The dissatisfied adaptive snowdrift game (DASG) describes the adaptive actions driven by the level of dissatisfaction when two connected agents interact. We study the DASG in static networks both numerically and analytically. In a random network of uniform degree k, the system evolves into a homogeneous state consisting only of cooperators when the cost-to-benefit ratio r < r 0 and a mixed phase with the coexistence of cooperators and defectors when r > r 0, where r 0 is a threshold. For an infinite population, the large k limit corresponding to the well-mixed case is solved analytically. A theory is developed based on the pair approximation. It gives the frequency of cooperation f c and the densities of different pairs that are in good agreement with simulation results. The results revealed that f c is enhanced in networked populations with a finite k, when compared with the well-mixed case. The reasons that the theory works well for the present model are traced back to the weak spatial correlation implied by the random network and the fact that the adaptive actions in DASG are driven only by the strategy pairs. The results shed light on the class of models that the pair approximation is applicable.

  2. Fusion of contrast-enhanced breast MR and mammographic imaging data.

    PubMed

    Behrenbruch, Christian P; Marias, Kostas; Armitage, Paul A; Yam, Margaret; Moore, Niall; English, Ruth E; Clarke, Jane; Brady, Michael

    2003-09-01

    Increasing use is being made of Gd-DTPA contrast-enhanced magnetic resonance imaging for breast cancer assessment since it provides 3D functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages as well as patients with post-operative scarring. Contrast-enhanced MRI (CE-MRI) is complementary to conventional X-ray mammography, since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value in fusing the high-resolution structural information available from mammography with the functional data acquired from MRI imaging. This paper presents a novel data fusion technique whereby medial-lateral oblique (MLO) and cranial-caudal (CC) mammograms (2D data) are registered to 3D contrast-enhanced MRI volumes. We utilise a combination of pharmacokinetic modelling, projection geometry, wavelet-based landmark detection and thin-plate spline non-rigid 'warping' to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume. Of key importance is the use of a flexible wavelet-based feature extraction technique that enables feature correspondences to be robustly determined between the very different image characteristics of X-ray mammography and MRI. An evaluation of the fusion framework is demonstrated with a series of clinical cases and a total of 14 patient examples.

  3. FEASIBILITY AND SAFETY OF CONTRAST-ENHANCED ULTRASOUND IN THE DISTAL LIMB OF SIX HORSES.

    PubMed

    Seiler, Gabriela S; Campbell, Nigel; Nixon, Britton; Tsuruta, James K; Dayton, Paul A; Jennings, Samuel; Redding, W Rich; Lustgarten, Meghann

    2016-05-01

    Vascular alterations play important roles in many orthopedic diseases such as osteoarthritis, tendonitis, and synovitis in both human and equine athletes. Understanding these alterations could enhance diagnosis, prognosis, and treatment. Contrast-enhanced ultrasound (CEUS) could be a valuable method for evaluation of blood flow and perfusion of these processes in the equine distal limb, however no reports were found describing feasibility or safety of the technique. The goal of this prospective, experimental study was to describe the feasibility and safety of distal limb CEUS in a sample of six horses. For each horse, CEUS of the distal limb was performed after intravenous injections of 5 and 10 ml, as well as intra-arterial injections of 0.5 and 1 ml contrast medium. Vital parameters were monitored and CEUS images were assessed qualitatively and quantitatively for degree of contrast enhancement. None of the horses had clinically significant changes in their vital parameters after contrast medium injection. One horse had a transient increase in respiratory rate, and several horses had mild increases of systolic blood pressure of short duration after intravenous, but not after intra-arterial injections. Intra-arterial injection was possible in all horses and resulted in significantly improved contrast enhancement both quantitatively (P = 0.027) and qualitatively (P = 0.019). Findings from this study indicated that CEUS is a feasible and safe diagnostic test for evaluation of the equine distal limb. Future studies are needed to assess the clinical utility of this test for horses with musculoskeletal diseases. PMID:26765518

  4. 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.

  5. Enhanced-Contrast Viewing of White-Hot Objects in Furnaces

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    An apparatus denoted a laser image contrast enhancement system (LICES) increases the contrast with which one can view a target glowing with blackbody radiation (a white-hot object) against a background of blackbody radiation in a furnace at a temperature as high as approximately 1,500 C. The apparatus utilizes a combination of narrowband illumination, along with band-pass filtering and polarization filtering to pass illumination reflected by the target while suppressing blackbody light from both the object and its background.

  6. 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.

  7. 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.

  8. Synergistic enhancement of iron oxide nanoparticle and gadolinium for dual-contrast MRI

    SciTech Connect

    Zhang, Fan; Huang, Xinglu; Qian, Chunqi; Zhu, Lei; Hida, Naoki; Niu, Gang; Chen, Xiaoyuan

    2012-09-07

    Highlights: Black-Right-Pointing-Pointer MR contrast agents exert influence on T{sub 1} or T{sub 2} relaxation time of the surrounding tissue. Black-Right-Pointing-Pointer Combined use of iron oxide and Gd-DTPA can improve the sensitivity/specificity of lesion detection. Black-Right-Pointing-Pointer Dual contrast MRI enhances the delineation of tumor borders and small lesions. Black-Right-Pointing-Pointer The effect of DC-MRI can come from the high paramagnetic susceptibility of Gd{sup 3+}. Black-Right-Pointing-Pointer The effect of DC-MRI can also come from the distinct pharmacokinetic distribution of SPIO and Gd-DTPA. -- Abstract: Purpose: The use of MR contrast agents allows accurate diagnosis by exerting an influence on the longitudinal (T{sub 1}) or transverse (T{sub 2}) relaxation time of the surrounding tissue. In this study, we combined the use of iron oxide (IO) particles and nonspecific extracellular gadolinium chelate (Gd) in order to further improve the sensitivity and specificity of lesion detection. Procedures: With a 7-Tesla scanner, pre-contrasted, IO-enhanced and dual contrast agent enhanced MRIs were performed in phantom, normal animals, and animal models of lymph node tumor metastases and orthotopic brain tumor. For the dual-contrast (DC) MRI, we focused on the evaluation of T{sub 2} weighted DC MRI with IO administered first, then followed by the injection of a bolus of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Results: Based on the C/N ratios and MRI relaxometry, the synergistic effect of coordinated administration of Gd-DTPA and IO was observed and confirmed in phantom, normal liver and tumor models. At 30 min after administration of Feridex, Gd-DTPA further decreased T{sub 2} relaxation in liver immediately after the injection. Additional administration of Gd-DTPA also immediately increased the signal contrast between tumor and brain parenchyma and maximized the C/N ratio to -4.12 {+-} 0.71. Dual contrast MRI also enhanced the

  9. A wavelet packet adaptive filtering algorithm for enhancing manatee vocalizations.

    PubMed

    Gur, M Berke; Niezrecki, Christopher

    2011-04-01

    Approximately a quarter of all West Indian manatee (Trichechus manatus latirostris) mortalities are attributed to collisions with watercraft. A boater warning system based on the passive acoustic detection of manatee vocalizations is one possible solution to reduce manatee-watercraft collisions. The success of such a warning system depends on effective enhancement of the vocalization signals in the presence of high levels of background noise, in particular, noise emitted from watercraft. Recent research has indicated that wavelet domain pre-processing of the noisy vocalizations is capable of significantly improving the detection ranges of passive acoustic vocalization detectors. In this paper, an adaptive denoising procedure, implemented on the wavelet packet transform coefficients obtained from the noisy vocalization signals, is investigated. The proposed denoising algorithm is shown to improve the manatee detection ranges by a factor ranging from two (minimum) to sixteen (maximum) compared to high-pass filtering alone, when evaluated using real manatee vocalization and background noise signals of varying signal-to-noise ratios (SNR). Furthermore, the proposed method is also shown to outperform a previously suggested feedback adaptive line enhancer (FALE) filter on average 3.4 dB in terms of noise suppression and 0.6 dB in terms of waveform preservation.

  10. A wavelet packet adaptive filtering algorithm for enhancing manatee vocalizations.

    PubMed

    Gur, M Berke; Niezrecki, Christopher

    2011-04-01

    Approximately a quarter of all West Indian manatee (Trichechus manatus latirostris) mortalities are attributed to collisions with watercraft. A boater warning system based on the passive acoustic detection of manatee vocalizations is one possible solution to reduce manatee-watercraft collisions. The success of such a warning system depends on effective enhancement of the vocalization signals in the presence of high levels of background noise, in particular, noise emitted from watercraft. Recent research has indicated that wavelet domain pre-processing of the noisy vocalizations is capable of significantly improving the detection ranges of passive acoustic vocalization detectors. In this paper, an adaptive denoising procedure, implemented on the wavelet packet transform coefficients obtained from the noisy vocalization signals, is investigated. The proposed denoising algorithm is shown to improve the manatee detection ranges by a factor ranging from two (minimum) to sixteen (maximum) compared to high-pass filtering alone, when evaluated using real manatee vocalization and background noise signals of varying signal-to-noise ratios (SNR). Furthermore, the proposed method is also shown to outperform a previously suggested feedback adaptive line enhancer (FALE) filter on average 3.4 dB in terms of noise suppression and 0.6 dB in terms of waveform preservation. PMID:21476661

  11. Degree of Enhancement on Contrast Enhanced Spectral Mammography (CESM) and Lesion Type on Mammography (MG): Comparison Based on Histological Results

    PubMed Central

    Łuczyńska, Elżbieta; Niemiec, Joanna; Hendrick, Edward; Heinze, Sylwia; Jaszczyński, Janusz; Jakubowicz, Jerzy; Sas-Korczyńska, Beata; Rys, Janusz

    2016-01-01

    Background Contrast enhanced spectral mammography (CESM) is a new method of breast cancer diagnosis in which an iodinated contrast agent is injected and dual-energy mammography is obtained in multiple views of the breasts. The aim of this study was to compare the degree of enhancement on CESM with lesion characteristics on mammography (MG) and lesion histology in women with suspicious breast lesions. Material/Methods The degree of enhancement on CESM (absent, weak, medium, or strong) was compared to lesion characteristics on MG (mass, mass with microcalcifications, or microcalcifications alone) and histology (infiltrating carcinoma, intraductal carcinoma, or benign) to compare sensitivity of the two modalities and to establish correlations that might improve diagnostic accuracy. Results Among 225 lesions identified with CESM and MG, histological evaluation revealed 143 carcinomas (127 infiltrating, 16 intraductal) and 82 benign lesions. This is the largest cohort investigated with CESM to date. The sensitivity of CESM was higher than that of MG (100% and 90%, respectively, p=0.010). Medium or strong enhancement on CESM and the presence of a mass on MG was the most likely indictor of malignancy (55.1% p=0.002). Among benign lesions, 60% presented as enhancement on CESM (were false-positive), and most frequently as medium or weak enhancement, together with a mass on MG (53%, p=0.047). Unfortunately, the study did not find combinations of MG findings and CESM enhancement patterns that would be helpful in defining false-positive lesions. We observed systematic overestimation of maximum lesion diameter on CESM compared to histology (mean difference: 2.29 mm). Conclusions Strong or medium enhancement on CESM and mass or mass with microcalcifications on MG were strong indicators of malignant transformation. However, we found no combination of MG and CESM characteristics helpful in defining false-positive lesions. PMID:27768681

  12. Synergistic enhancements of ultrasound image contrast with a combination of phase aberration correction and dual apodization with cross-correlation.

    PubMed

    Shin, Junseob; Yen, Jesse T

    2012-09-01

    Dual apodization with cross-correlation (DAX) is a novel adaptive beamforming technique which utilizes two distinct apodization functions in suppressing side lobes and clutter. Previous studies have shown that the performance of DAX in minimizing the effects of phase aberration diminishes with increasing aberrator strength. To achieve greater improvement in image contrast, we propose, in this paper, to combine DAX with a phase aberration correction algorithm based on nearest-neighbor cross-correlation (NNCC). Our simulation and experimental results presented in this work showed that the proposed method allows for synergistic enhancements of image contrast and achieves greater improvement in image quality than using DAX alone or phase aberration correction alone in the presence of weak and strong aberrators. Compared with standard delay-and-sum (DAS) beamforming, using the proposed method on simulated data with weak and strong aberrations increased the contrast-to-noise ratio (CNR) values from 4.10 to 10.96 and from 1.69 to 9.80, respectively. Experimental results were obtained using pork tissues of 4 and 10 mm thickness and a tissue-mimicking phantom. The CNR values increased from 3.74 to 9.72 for the 4-mm pork aberrator and from 1.27 to 8.17 for the 10-mm pork aberrator. PMID:23007784

  13. EFFECT OF SEDATION ON CONTRAST-ENHANCED ULTRASONOGRAPHY OF THE SPLEEN IN HEALTHY DOGS.

    PubMed

    Rossi, Federica; Fina, Caroline; Stock, Emmelie; Vanderperren, Katrien; Duchateau, Luc; Saunders, Jimmy H

    2016-05-01

    Contrast-enhanced ultrasound of the spleen enables the dynamic assessment of the perfusion of this organ, however, both subjective and quantitative evaluation can be strongly influenced by sedative agent administration. The purpose of this prospective, experimental study was to test effects of two sedative agents on splenic perfusion during contrast-enhanced ultrasound of the spleen in a sample of healthy dogs. Contrast-enhanced ultrasound of the spleen was repeated in six healthy Beagles following a cross-over study design comparing three protocols: awake, butorphanol 0.2 mg/Kg intramuscular (IM), and dexmedetomidine 500 μg/m(2) IM. After intravenous injection of a phospholipid stabilized sulfur hexafluoride microbubble solution (SonoVue®, Bracco Imaging, Milano, Italy), the enhancement intensity and perfusion pattern of the splenic parenchyma were assessed and perfusion parameters were calculated. Normal spleen was slightly heterogeneous in the early phase, but the parenchyma was homogeneous at a later phase. Sedation with butorphanol did not modify perfusion of the spleen. Dexmedetomidine significantly reduced splenic enhancement, providing diffuse parenchymal hypoechogenicity during the entire examination. Measured parameters were significantly modified, with increased arrival time (AT; (< 0.0001) and time to peak (TTP; P < 0.0001), and decreased peak intensity (PI; P = 0.0108), wash-in (P = 0.0014), and area under the curve (AUC; P = 0.0421). Findings supported the use of butorphanol and contraindicated the use of dexmedetomidine as sedatives for splenic contrast ultrasound procedures in dogs. Short-term and diffuse heterogeneity of the spleen in the early venous phase was determined to be a normal finding. PMID:26777031

  14. Three-dimensional Contrast-enhanced Ultrasound in Response Assessment for Breast Cancer: A Comparison with Dynamic Contrast-enhanced Magnetic Resonance Imaging and Pathology

    PubMed Central

    Jia, Wan-Ru; Tang, Lei; Wang, Deng-Bin; Chai, Wei-Min; Fei, Xiao-Chun; He, Jian-Rong; Chen, Man; Wang, Wen-Ping

    2016-01-01

    To compare the capabilities of three-dimensional contrast enhanced ultrasound (3D-CEUS) and dynamic contrast-enhanced magnetic resonance (DCE-MRI) in predicting the response to neoadjuvant chemotherapy (NAC) among breast cancer patients, 48 patients with unilateral breast cancer were recruited for 3D-CEUS and DCE-MRI examinations both before and after NAC; pathology was used to validate the results. This study was approved by the institutional review board, and written informed consent was obtained from each patient. Imaging feature changes and pathological vascularity response, including microvessel density (MVD) and vascular endothelial growth factor (VEGF), were calculated. Pathological complete response (pCR) and major histological response (MHR) were used as references. The 3D-CEUS score, DCE-MRI score, MVD and VEGF significantly decreased (P < 0.0001) after NAC. The correlations between Δ3D-CEUS and ΔDCE-MRI with pCR (r = 0.649, P < 0.0001; r = 0.639, P < 0.0001) and MHR (r = 0.863, P < 0.0001; r = 0.836, P < 0.0001) were significant. All scores showed significant differences between the pCR and non-pCR groups with folder changes of 0.1, 0.1, 2.4, and 2.3, respectively (P = 0.0001, <0.0001, <0.0001 and <0.0001). In conclusion, 3D-CEUS is effective in assessing the response of breast cancer patients undergoing NAC. PMID:27652518

  15. Suprathreshold contrast perception across differences in mean luminance: effects of stimulus size, dichoptic presentation, and length of adaptation.

    PubMed

    Peli, E

    1995-05-01

    Contrast constancy across changes in mean luminance was reported to hold over a wide range of luminances in a few studies and to be limited to approximately 1 log unit in another. The studies reporting contrast constancy over a wide luminance range used extended grafting stimuli presented dichoptically (bright stimulus to one eye and dim stimulus to the other) with long adaptation periods. The study reporting only limited constancy used narrow (1-octave-wide) Gabor patches presented side by side to both eyes with only a short (up to 5 s) period of adaptation. The current study was designed to determine whether differences in stimulus bandwidth, presentation format, or adaptation time could account for the different results reported. It was found that increasing stimulus size had no effect on the results. Dichoptic presentation with either a filter in front of one eye or calibrated screen luminance could account for the differences between the studies. When dichoptic presentation was combined with short adaptation periods (of a few seconds) an intermediate deviation from constancy was demonstrated. This effect suggests that the deviations from constancy demonstrated under free viewing are due to a lack of fast local adaptation and not to long-distance interactions across the retina.

  16. Suprathreshold contrast perception across differences in mean luminance: effects of stimulus size, dichoptic presentation, and length of adaptation

    NASA Astrophysics Data System (ADS)

    Peli, Eli

    1995-05-01

    Contrast constancy across changes in mean luminance was reported to hold over a wide range of luminances in a few studies and to be limited to approximately 1 log unit in another. The studies reporting contrast constancy over a wide luminance range used extended grating stimuli presented dichoptically (bright stimulus to one eye and dim stimulus to the other) with long adaptation periods. The study reporting only limited constancy used narrow (1-octave-wide) Gabor patches presented side by side to both eyes with only a short (up to 5 s) period of adaptation. The current study was designed to determine whether differences in stimulus bandwidth, presentation format, or adaptation time could account for the different results reported. It was found that increasing stimulus size had no effect on the results. Dichoptic presentation with either a filter in front of one eye or calibrated screen luminance could account for the differences between the studies. When dichoptic presentation was combined with short adaptation periods (of a few seconds) an intermediate deviation from constancy was demonstrated. This effect suggests that the deviations from constancy demonstrated under free viewing are due to a lack of fast local adaptation and not to long-distance interactions across the retina.

  17. Color enhancement of highly correlated images. I - Decorrelation and HSI contrast stretches. [hue saturation intensity

    NASA Technical Reports Server (NTRS)

    Gillespie, Alan R.; Kahle, Anne B.; Walker, Richard E.

    1986-01-01

    Conventional enhancements for the color display of multispectral images are based on independent contrast modifications or 'stretches' of three input images. This approach is not effective if the image channels are highly correlated or if the image histograms are strongly bimodal or more complex. Any of several procedures that tend to 'stretch' color saturation while leaving hue unchanged may better utilize the full range of colors for the display of image information. Two conceptually different enhancements are discussed: the 'decorrelation stretch', based on principal-component (PC) analysis, and the 'stretch' of 'hue' - 'saturation' - intensity (HSI) transformed data. The PC transformation in scene-dependent, but the HSI transformation is invariant. Examples of images enhanced by conventional linear stretches, decorrelation stretch, and by stretches of HSI transformed data are compared. Schematic variation diagrams or two- and three-dimensional histograms are used to illustrate the 'decorrelation stretch' method and the effect of the different enhancements.

  18. Contrast Enhancement of the Right Ventricle during Coronary CT Angiography – Is It Necessary?

    PubMed Central

    Kok, Madeleine; Kietselaer, Bas L. J. H.; Mihl, Casper; Altintas, Sibel; Nijssen, Estelle C.; Wildberger, Joachim E.; Das, Marco

    2015-01-01

    Purpose It is unclear if prolonged contrast media injection, to improve right ventricular visualization during coronary CT angiography, leads to increased detection of right ventricle pathology. The purpose of this study was to evaluate right ventricle enhancement and subsequent detection of right ventricle disease during coronary CT angiography. Materials and Methods 472 consecutive patients referred for screening coronary CT angiography were retrospectively evaluated. Every patient underwent multidetector-row CT of the coronary arteries: 128x 0.6mm coll., 100-120kV, rot. time 0.28s, ref. mAs 350 and received an individualized (P3T) contrast bolus injection of iodinated contrast medium (300 mgI/ml). Patient data were analyzed to assess right ventricle enhancement (HU) and right ventricle pathology. Image quality was defined good when right ventricle enhancement >200HU, moderate when 140-200HU and poor when <140HU. Results Good image quality was found in 372 patients, moderate in 80 patients and poor in 20 patients. Mean enhancement of the right ventricle cavity was 268HU±102. Patients received an average bolus of 108±24 ml at an average peak flow rate of 6.1±2.2 ml/s. In only three out of 472 patients (0.63%) pathology of the right ventricle was found (dilatation) No other right ventricle pathology was detected. Conclusion Right ventricle pathology was detected in three out of 472 patients; the dilatation observed in these three cases may have been picked up even without dedicated enhancement of the right ventricle. Based on our findings, right ventricle enhancement can be omitted during screening coronary CT angiography. PMID:26029905

  19. Performance comparison of fully adaptive and static passive polarimetric imagers in the presence of intensity and polarization contrast.

    PubMed

    Goudail, François; Boffety, Matthieu

    2016-09-01

    We address the comparison of contrast improvement obtained with a fully adaptive polarimetric imager and the best channel of a static polarimetric imager in the presence of both intensity and polarization differences between the target and the background. We develop an in-depth quantitative study of the performance loss incurred by a static imager compared to a fully adaptive one in this case. These results are useful to make a well-informed choice between these two polarimetric imaging architectures in a given application. PMID:27607513

  20. 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. PMID:24893835

  1. Diagnostic performance of contrast-enhanced ultrasound for ovarian cancer: a meta-analysis.

    PubMed

    Wu, Ying; Peng, Hongling; Zhao, Xia

    2015-04-01

    This meta-analysis is the first study aimed at assessing the overall diagnostic performance of contrast-enhanced ultrasound for ovarian cancer. PubMed, Embase and Medline databases were systematically searched for relevant articles published up to June 2014. Data were pooled to yield summary sensitivity, specificity, diagnostic odds ratio and receiver operating characteristic curves using Meta-Disc Version 1.4 software. Ten independent studies with 579 ovarian tumors were enrolled in this meta-analysis. The pooled sensitivity, specificity and diagnostic odds ratio statistics were 0.89 (0.83-0.94), 0.91 (0.88-0.93) and 91.70 (41.41-203.05), respectively, and the area under the summary receiver operating characteristic curve was 0.9619 (standard error: 0.0125), all indicating that contrast-enhanced ultrasound has high diagnostic accuracy in differentiation of malignant from benign ovarian tumors.

  2. 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.

  3. Acute kidney injury after contrast-enhanced examination among elderly1

    PubMed Central

    Aoki, Beatriz Bonadio; Fram, Dayana; Taminato, Mônica; Batista, Ruth Ester Sayad; Belasco, Angélica; Barbosa, Dulce Aparecida

    2014-01-01

    OBJECTIVES: to assess renal function in elderly patients undergoing contrast-enhanced computed tomography and identify the preventive measures of acute kidney injury in the period before and after the examination. METHOD: longitudinal cohort study conducted at the Federal University of São Paulo Hospital, from March 2011 to March 2013. All hospitalized elderly, of both sexes, aged 60 years and above, who performed the examination, were included (n=93). We collected sociodemographic data, data related to the examination and to the care provided, and creatinine values prior and post exam. RESULTS: an alteration in renal function was observed in 51 patients (54%) with a statistically significant increase of creatinine values (p<0.04), and two patients (4.0%) required hemodialysis. CONCLUSION: There is an urgent need for protocols prior to and post contrast-enhanced examination in the elderly, and other studies to verify the prognosis of this population. PMID:25296148

  4. A novel method for viability assessment by cinematographic and late contrast enhanced MRI

    NASA Astrophysics Data System (ADS)

    Gao, Gang; Cockshott, Paul W.; Martin, Thomas N.; Foster, John E.; Elliott, Alex; Dargie, Henry; Groenning, Bjoern A.

    2004-04-01

    Using cardiac magnetic resonance (MR) imaging, a combination of late contrast enhanced MR (ceMR) and cinematographic (CINE) images, a myocardial viability score can be derived. At present this score is produced by visual evaluation of wall motion abnormalities in combination with presence or absence of late hyper enhancement (LE) on ceMR. We set out to develop and validate image processing techniques derived from stereo vision capable of reducing the observer dependence and improving accuracy in the diagnosis of viable myocardium.

  5. Contrast enhanced ultrasound in the evaluation and percutaneous treatment of hepatic and renal tumors.

    PubMed

    Meloni, Maria Franca; Smolock, Amanda; Cantisani, Vito; Bezzi, Mario; D'Ambrosio, Ferdinando; Proiti, Maria; Lee, Fred; Aiani, Luca; Calliada, Fabrizio; Ferraioli, Giovanna

    2015-09-01

    Image-guided percutaneous ablation techniques are increasingly being used for the treatment of malignant tumors of the liver and kidney. Contrast enhanced ultrasound (CEUS) is a real-time dynamic imaging technique that plays an important role in the pre-, intra-, and post-procedural management of these patients. This review will focus on the role of CEUS in the evaluation of patients undergoing treatment with percutaneous ablation for hepatic or renal tumors.

  6. A monte carlo comparison of three different media for contrast enhanced radiotherapy of the prostate.

    PubMed

    Garnica-Garza, H M

    2010-06-01

    Contrast-enhanced radiotherapy makes use of a kilovoltage X-ray beam, either from a diagnostic X-ray tube or modified megavoltage linear accelerator, in conjunction with a high-Z contrast medium deposited into the target volume to enhance the absorption of radiation. In this work, using the Monte Carlo code PENELOPE and the voxelized Zubal phantom to model a prostate radiotherapy treatment, a comparison between the physical absorbed dose distributions rendered by three different enhancing agents namely bismuth, gadolinium, and iodine is performed. It is assumed that there exists a concentration of 10 mg of enhancing agent per 1 g of tissue in the target volume while in the background a concentration of 1.5 mg per 1 g of tissue is present. The X-ray beam energy spectrum was obtained by means of Monte Carlo simulation of a tungsten target upon which a 220 keV mono-energetic electron pencil beam is made to impinge, and the resultant photon beam is heavily filtrated by 0.2 cm of copper. The treatment delivery is simulated as a 3608 arc collimated to conform to the target from every direction. Cumulative dose-volume histograms and isodose curves are presented for the target as well as five organs-at-risk, namely rectal wall, bladder, femoral heads, skin, and bone marrow. It is shown that under these conditions clinically acceptable treatment plans are obtained for all three contrast agents. A 72 Gy dose to 100% of the target volume results in maximum absorbed doses to the above mentioned organs-at-risk of 65, 56, 44, 32 and 65 Gy respectively when bismuth is used as the contrast agent, but the results obtained with gadolinium follow closely.

  7. Chest Pain of Uncertain Aetiology: Role of Contrast Enhanced Computed Tomography in the Emergency Department

    PubMed Central

    Yassin, Firas; Sawh, Chris; Garg, Pankaj

    2016-01-01

    There is increasing role of computed tomographic (CT) in the assessment of acute chest pain in the emergency department especially when the diagnosis is not clear. We report a case where non ECG gated contrast enhanced CT in the emergency department for rule-out of pulmonary embolus guided to the actual diagnosis, which was, acute coronary event, as evidenced by the presence of perfusion defect. PMID:27733870

  8. Vascular Structure Identification in Intraoperative 3D Contrast-Enhanced Ultrasound Data.

    PubMed

    Ilunga-Mbuyamba, Elisee; Avina-Cervantes, Juan Gabriel; Lindner, Dirk; Cruz-Aceves, Ivan; Arlt, Felix; Chalopin, Claire

    2016-04-08

    In this paper, a method of vascular structure identification in intraoperative 3D Contrast-Enhanced Ultrasound (CEUS) data is presented. Ultrasound imaging is commonly used in brain tumor surgery to investigate in real time the current status of cerebral structures. The use of an ultrasound contrast agent enables to highlight tumor tissue, but also surrounding blood vessels. However, these structures can be used as landmarks to estimate and correct the brain shift. This work proposes an alternative method for extracting small vascular segments close to the tumor as landmark. The patient image dataset involved in brain tumor operations includes preoperative contrast T1MR (cT1MR) data and 3D intraoperative contrast enhanced ultrasound data acquired before (3D-iCEUS(start) and after (3D-iCEUS(end) tumor resection. Based on rigid registration techniques, a preselected vascular segment in cT1MR is searched in 3D-iCEUS(start) and 3D-iCEUS(end) data. The method was validated by using three similarity measures (Normalized Gradient Field, Normalized Mutual Information and Normalized Cross Correlation). Tests were performed on data obtained from ten patients overcoming a brain tumor operation and it succeeded in nine cases. Despite the small size of the vascular structures, the artifacts in the ultrasound images and the brain tissue deformations, blood vessels were successfully identified.

  9. Kupffer-phase findings of hepatic hemangiomas in contrast-enhanced ultrasound with sonazoid.

    PubMed

    Sugimoto, Katsutoshi; Moriyasu, Fuminori; Saito, Kazuhiro; Yoshiara, Hiroki; Imai, Yasuharu

    2014-06-01

    The aim of this study was to assess quantitatively the Kupffer-phase enhancement patterns of hepatic hemangiomas in contrast-enhanced ultrasound (CEUS) with Sonazoid. A total of 46 patients with 46 hepatic hemangiomas (17.1 ± 6.2 mm in diameter, 34 typical type and 12 high-flow type) underwent CEUS in the Kupffer phase. The lesion-to-liver contrast ratio in the Kupffer phase was quantitatively assessed for both types of hemangioma. Most of the hepatic hemangiomas, whether or not they were the high-flow type, were iso- to hypo-echoic relative to the surrounding liver parenchyma. The contrast ratio was -5.33 ± 6.70 dB for the high-flow hemangiomas and -4.54 ± 6.28 dB for the typical hemangiomas. There was no significant difference in contrast ratio between the two types of lesions (p = 0.73). All of the hemangiomas, whether of typical or high-flow type, are iso- to hypo-echoic relative to the surrounding liver parenchyma on Kupffer-phase imaging.

  10. Reversible and Asymptomatic Gyral and Subarachnoid Contrast Enhancement after Carotid Stenting

    PubMed Central

    Vangosa, Alessandra Briatico; Tortora, Domenico; Modestino, Francesco; Cotroneo, Antonio R

    2015-01-01

    The presence of sulcal hyperdensity in patients after endovascular procedures is not necessarily attributable to hemorrhage. It may frequently indicate the absolute or concomitant extravasation of contrast material into the subarachnoid spaces. This case report describes the clinical case of an 84-year-old patient with 90% stenosis of the right internal carotid who presented with a diffuse gyral and sulcal hyperdensity in the right temporal-occipital and frontal lobes at routine post-carotid stenting (CAS) brain CT scan. The patient was asymptomatic and CT findings were interpreted as contrast enhancement hyperattenuation and no therapeutic decisions were made. A 24-hour follow-up brain CT demonstrated the complete resolution of the hyperdensity, confirming the diagnosis. In this patient we considered the concomitant presence of gyral and sulcal hyperdensity as the consequence of reversible damage to the blood-brain barrier (BBB) determining a transitory extravasation of contrast material. Asymptomatic gyral and subarachnoid contrast enhancement following CAS is generally indicative of benign and transitory damage to the BBB and is not to be misinterpreted as hemorrhage. PMID:25923674

  11. Vascular Structure Identification in Intraoperative 3D Contrast-Enhanced Ultrasound Data

    PubMed Central

    Ilunga-Mbuyamba, Elisee; Avina-Cervantes, Juan Gabriel; Lindner, Dirk; Cruz-Aceves, Ivan; Arlt, Felix; Chalopin, Claire

    2016-01-01

    In this paper, a method of vascular structure identification in intraoperative 3D Contrast-Enhanced Ultrasound (CEUS) data is presented. Ultrasound imaging is commonly used in brain tumor surgery to investigate in real time the current status of cerebral structures. The use of an ultrasound contrast agent enables to highlight tumor tissue, but also surrounding blood vessels. However, these structures can be used as landmarks to estimate and correct the brain shift. This work proposes an alternative method for extracting small vascular segments close to the tumor as landmark. The patient image dataset involved in brain tumor operations includes preoperative contrast T1MR (cT1MR) data and 3D intraoperative contrast enhanced ultrasound data acquired before (3D-iCEUSstart) and after (3D-iCEUSend) tumor resection. Based on rigid registration techniques, a preselected vascular segment in cT1MR is searched in 3D-iCEUSstart and 3D-iCEUSend data. The method was validated by using three similarity measures (Normalized Gradient Field, Normalized Mutual Information and Normalized Cross Correlation). Tests were performed on data obtained from ten patients overcoming a brain tumor operation and it succeeded in nine cases. Despite the small size of the vascular structures, the artifacts in the ultrasound images and the brain tissue deformations, blood vessels were successfully identified. PMID:27070610

  12. Design of a contrast-enhanced dual-energy tomosynthesis system for breast cancer imaging

    NASA Astrophysics Data System (ADS)

    Hörnig, M. D.; Bätz, L.; Mertelmeier, T.

    2012-03-01

    Digital breast tomosynthesis (DBT) is a three-dimensional X-ray imaging modality that has the potential to decrease the superimposition effect of breast structural noise, thereby increasing lesion conspicuity. To further improve breast cancer detection, our work has been devoted to develop a prototype for contrast-enhanced dual-energy tomosynthesis (CEDET). CEDET involves the injection of an iodinated contrast agent and measures the relative increase in uptake of contrast in the suspected breast cancer lesion. Either temporal or dual-energy subtraction techniques may be used to implement CEDET. Both 2D contrast-enhanced dual-energy mammography and 3D tomosynthesis can be applied. Here we present the design of a prototype CEDET system based on the Siemens MAMMOMAT Inspiration and employing two additional high-energy filters in addition to the standard Rh filter, the latter being used for the low-energy acquisitions. A quality factor of squared signal-difference-to-noise-ratio of iodine per pixel area and average glandular dose as a function of breast thickness is used to optimize the filter material, the filter thickness, and the tube voltage. The average glandular dose can be calculated from the entrance surface air kerma using computed conversion coefficients DgN for the used X-ray spectra. We also present the results of DQE measurements of the amorphous selenium detector involved. Finally, results of phantom tests for tomosynthesis acquisition and first clinical data in the 2D mode will be shown.

  13. 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.

  14. Involuntary attention enhances identification accuracy for unmasked low contrast letters using non-predictive peripheral cues.

    PubMed

    Pack, Weston; Carney, Thom; Klein, Stanley A

    2013-08-30

    There is controversy regarding whether or not involuntary attention improves response accuracy at a cued location when the cue is non-predictive and if these cueing effects are dependent on backward masking. Various perceptual and decisional mechanisms of performance enhancement have been proposed, such as signal enhancement, noise reduction, spatial uncertainty reduction, and decisional processes. Herein we review a recent report of mask-dependent accuracy improvements with low contrast stimuli and demonstrate that the experiments contained stimulus artifacts whereby the cue impaired perception of low contrast stimuli, leading to an absence of improved response accuracy with unmasked stimuli. Our experiments corrected these artifacts by implementing an isoluminant cue and increasing its distance relative to the targets. The results demonstrate that cueing effects are robust for unmasked stimuli presented in the periphery, resolving some of the controversy concerning cueing enhancement effects from involuntary attention and mask dependency. Unmasked low contrast and/or short duration stimuli as implemented in these experiments may have a short enough iconic decay that the visual system functions similarly as if a mask were present leading to improved accuracy with a valid cue.

  15. Dual-energy contrast enhanced digital breast tomosynthesis: concept, method, and evaluation on phantoms

    NASA Astrophysics Data System (ADS)

    Puong, Sylvie; Patoureaux, Fanny; Iordache, Razvan; Bouchevreau, Xavier; Muller, Serge

    2007-03-01

    In this paper, we present the development of dual-energy Contrast-Enhanced Digital Breast Tomosynthesis (CEDBT). A method to produce background clutter-free slices from a set of low and high-energy projections is introduced, along with a scheme for the determination of the optimal low and high-energy techniques. Our approach consists of a dual-energy recombination of the projections, with an algorithm that has proven its performance in Contrast-Enhanced Digital Mammography1 (CEDM), followed by an iterative volume reconstruction. The aim is to eliminate the anatomical background clutter and to reconstruct slices where the gray level is proportional to the local iodine volumetric concentration. Optimization of the low and high-energy techniques is performed by minimizing the total glandular dose to reach a target iodine Signal Difference to Noise Ratio (SDNR) in the slices. In this study, we proved that this optimization could be done on the projections, by consideration of the SDNR in the projections instead of the SDNR in the slices, and verified this with phantom measurements. We also discuss some limitations of dual-energy CEDBT, due to the restricted angular range for the projection views, and to the presence of scattered radiation. Experiments on textured phantoms with iodine inserts were conducted to assess the performance of dual-energy CEDBT. Texture contrast was nearly completely removed and the iodine signal was enhanced in the slices.

  16. Increased salivary gland density on contrast-enhanced CT after head and neck radiation

    SciTech Connect

    Bronstein, A.D.; Nyberg, D.A.; Schwartz, A.N.; Shuman, W.P.; Griffin, B.R.

    1987-12-01

    In an attempt to determine whether radiation therapy leads to an increased density of salivary glands on subsequent contrast-enhanced CT, 109 CT scans from 78 patients with head and neck tumors were reviewed. The density of parotid and submandibular glands was subjectively evaluated (compared with adjacent muscle) and correlated with treatment including surgery, chemotherapy, and radiation. Density of the parotid and/or submandibular glands was found to be significantly associated with previous irradiation on contrast-enhanced scans (p less than .05). One or both glands were denser than normal in seven (44%) of 16 patients who received only radiation therapy and in eight (38%) of 21 who received chemotherapy and radiation therapy, compared with only two (10%) of 20 patients who received chemotherapy alone and two (4%) of 52 patients who received neither. The type or amount of irradiation, type of chemotherapy, or timing of the CT scan after the initiation of treatment was not found to be significant. We conclude that the density of the parotid and/or submandibular glands on contrast-enhanced CT is frequently increased after radiation therapy for tumors of the head and neck.

  17. Registration of dynamic contrast-enhanced MRI using a progressive principal component registration (PPCR)

    NASA Astrophysics Data System (ADS)

    Melbourne, A.; Atkinson, D.; White, M. J.; Collins, D.; Leach, M.; Hawkes, D.

    2007-09-01

    Registration of dynamic contrast-enhanced magnetic resonance images (DCE-MRI) of soft tissue is difficult. Conventional registration cost functions that depend on information content are compromised by the changing intensity profile, leading to misregistration. We present a new data-driven model of uptake patterns formed from a principal components analysis (PCA) of time-series data, avoiding the need for a physiological model. We term this process progressive principal component registration (PPCR). Registration is performed repeatedly to an artificial time series of target images generated using the principal components of the current best-registered time-series data. The aim is to produce a dataset that has had random motion artefacts removed but long-term contrast enhancement implicitly preserved. The procedure is tested on 22 DCE-MRI datasets of the liver. Preliminary assessment of the images is by expert observer comparison with registration to the first image in the sequence. The PPCR is preferred in all cases where a preference exists. The method requires neither segmentation nor a pharmacokinetic uptake model and can allow successful registration in the presence of contrast enhancement.

  18. Audiovisual contrast enhancement is articulated primarily via the M-pathway.

    PubMed

    Jaekl, Philip M; Soto-Faraco, Salvador

    2010-12-17

    Although it has been previously reported that audiovisual integration can modulate performance on some visual tasks, multisensory interactions have not been explicitly assessed in the context of different visual processing pathways. In the present study, we test auditory influences on visual processing employing a psychophysical paradigm that reveals distinct spatial contrast signatures of magnocellular and parvocellular visual pathways. We found that contrast thresholds are reduced when noninformative sounds are presented with transient, low-frequency Gabor patch stimuli and thus favor the M-system. In contrast, visual thresholds are unaffected by concurrent sounds when detection is primarily attributed to P-pathway processing. These results demonstrate that the visual detection enhancement resulting from multisensory integration is mainly articulated by the magnocellular system, which is most sensitive at low spatial frequencies. Such enhancement may subserve stimulus-driven processes including the orientation of spatial attention and fast, automatic ocular and motor responses. This dissociation helps explain discrepancies between the results of previous studies investigating visual enhancement by sounds.

  19. Evaluation of Feline Renal Perfusion with Contrast-Enhanced Ultrasonography and Scintigraphy

    PubMed Central

    Vanderperren, Katrien; Bosmans, Tim; Dobbeleir, André; Duchateau, Luc; Hesta, Myriam; Lybaert, Lien; Peremans, Kathelijne; Vandermeulen, Eva; Saunders, Jimmy

    2016-01-01

    Contrast-enhanced ultrasound (CEUS) is an emerging technique to evaluate tissue perfusion. Promising results have been obtained in the evaluation of renal perfusion in health and disease, both in human and veterinary medicine. Renal scintigraphy using 99mTc-Mercaptoacetyltriglycine (MAG3) is another non-invasive technique that can be used to evaluate renal perfusion. However, no data are available on the ability of CEUS or 99mTc- MAG3 scintigraphy to detect small changes in renal perfusion in cats. Therefore, both techniques were applied in a normal feline population to evaluate detection possibilities of perfusion changes by angiotensin II (AT II). Contrast-enhanced ultrasound using a bolus injection of commercially available contrast agent and renal scintigraphy using 99mTc-MAG3 were performed in 11 healthy cats after infusion of 0,9% NaCl (control) and AT II. Angiotensin II induced changes were noticed on several CEUS parameters. Mean peak enhancement, wash-in perfusion index and wash-out rate for the entire kidney decreased significantly after AT II infusion. Moreover, a tendency towards a lower wash-in area-under-the curve was present. Renal scintigraphy could not detect perfusion changes induced by AT II. This study shows that CEUS is able to detect changes in feline renal perfusion induced by AT II infusion. PMID:27736928

  20. Does clear speech enhance the voice onset time contrast in Croatian and English?

    NASA Astrophysics Data System (ADS)

    Smiljanic, Rajka; Bradlow, Ann

    2005-09-01

    This study investigates the effect of intelligibility-enhancing clear speech on voice onset time (VOT) in two languages with different phonetic realizations of a two-way voicing contrast. Specifically, it was explored whether the contrasts between prevoiced and short-lag categories in Croatian and short-lag and long-lag categories in English are enhanced along the VOT dimension in clear speech. Word-initial stops in words embedded in sentences read by native speakers of each language in conversational and clear speaking styles were examined. The results revealed that in English, the long-lag category (i.e., voiceless) extended somewhat in the positive VOT direction (longer aspiration), and in Croatian, the prevoiced category (i.e., voiced) extended somewhat in the negative VOT direction (longer prevoicing) in clear speech. However, in both languages, the short-lag tokens (i.e., voiced in English, voiceless in Croatian) were unchanged in clear versus conversational speech. Overall, then, the distance between the two voicing categories was rather stable across the two speaking styles in both languages. These results suggest that VOT is not a dimension of voicing category contrast enhancement. Rather, the language-specific pronunciation norms along this dimension are maintained in clear and conversational speech.

  1. Quantitative Contrast-Enhanced Ultrasonic Imaging Reflects Microvascularization in Hepatocellular Carcinoma and Prognosis after Resection.

    PubMed

    Zou, Ru-Hai; Lin, Qing-Guang; Huang, Wei; Li, Xiao-Ling; Cao, Yun; Zhang, Jing; Zhou, Jian-Hua; Li, An-Hua; Beretta, Laura; Qian, Chao-Nan

    2015-10-01

    Our aim was to evaluate the correlation between tumor vasculature detected by pre-surgical contrast-enhanced ultrasonography and the post-surgical prognosis of patients with hepatocellular carcinoma. One hundred ninety-five patients with hepatocellular carcinoma who had undergone curative resection and pre-operative contrast-enhanced ultrasonography were enrolled. Intra-tumoral microvessels were evaluated by immunohistochemical staining for anti-CD31 and anti-CD34. On the basis of the immunohistochemical staining and morphology patterns, tumors were divided into capillary-like and sinusoid-like microvessel subtypes. The rise time of tumors was shorter in the capillary-like microvessel subtype than in the sinusoid-like microvasculature subtype (p = 0.026). Intra-tumor microvascular density (p < 0.001, hazard ratio = 0.137) and rise time (p = 0.006, hazard ratio = 2.475) were independent factors corresponding to different microvasculature types. Microvascular density, vascular invasion and wash-in perfusion index were determined to be independent factors in recurrence-free survival and overall survival. In conclusion, contrast-enhanced ultrasonography may serve as a means of non-invasive assessment of tumor angiogenesis and may be associated with the survival of patients with hepatocellular carcinoma after resection. PMID:26210785

  2. Tracer kinetic model-driven registration for dynamic contrast-enhanced MRI time-series data.

    PubMed

    Buonaccorsi, Giovanni A; O'Connor, James P B; Caunce, Angela; Roberts, Caleb; Cheung, Sue; Watson, Yvonne; Davies, Karen; Hope, Lynn; Jackson, Alan; Jayson, Gordon C; Parker, Geoffrey J M

    2007-11-01

    Dynamic contrast-enhanced MRI (DCE-MRI) time series data are subject to unavoidable physiological motion during acquisition (e.g., due to breathing) and this motion causes significant errors when fitting tracer kinetic models to the data, particularly with voxel-by-voxel fitting approaches. Motion correction is problematic, as contrast enhancement introduces new features into postcontrast images and conventional registration similarity measures cannot fully account for the increased image information content. A methodology is presented for tracer kinetic model-driven registration that addresses these problems by explicitly including a model of contrast enhancement in the registration process. The iterative registration procedure is focused on a tumor volume of interest (VOI), employing a three-dimensional (3D) translational transformation that follows only tumor motion. The implementation accurately removes motion corruption in a DCE-MRI software phantom and it is able to reduce model fitting errors and improve localization in 3D parameter maps in patient data sets that were selected for significant motion problems. Sufficient improvement was observed in the modeling results to salvage clinical trial DCE-MRI data sets that would otherwise have to be rejected due to motion corruption.

  3. Dynamic contrast-enhanced ultrasound of slaughterhouse porcine livers in machine perfusion.

    PubMed

    Izamis, Maria-Louisa; Efstathiades, Andreas; Keravnou, Christina; Leen, Edward L; Averkiou, Michalakis A

    2014-09-01

    The aim of this study was to enable investigations into novel imaging and surgical techniques by developing a readily accessible, versatile liver machine perfusion system. Slaughterhouse pig livers were used, and dynamic contrast-enhanced ultrasound was introduced to optimize the procurement process and provide real-time perfusion monitoring. The system comprised a single pump, oxygenator, bubble trap and two flowmeters for pressure-controlled perfusion of the vessels using an off-the-shelf perfusate at room temperature. Successful livers exhibited homogeneous perfusion in both the portal vein and hepatic artery with dynamic contrast-enhanced ultrasound, which correlated with stable oxygen uptake, bile production and hepatic resistance and normal histology at the end of 3 h of perfusion. Dynamic contrast-enhanced ultrasound revealed perfusion abnormalities invisible to the naked eye, thereby providing context to the otherwise systemic biochemical/hemodynamic measurements and focal biopsy findings. The model developed here is a simple, cost-effective approach for stable ex vivo whole-organ machine perfusion. PMID:25023101

  4. Automatic segmentation of the liver from multi- and single-phase contrast-enhanced CT images.

    PubMed

    Ruskó, László; Bekes, György; Fidrich, Márta

    2009-12-01

    Segmentation of contrast-enhanced abdominal CT images is required by many clinical applications of computer aided diagnosis and therapy planning. The research on automated methods involves different organs among which the liver is the most emphasized. In the current clinical practice more images (at different phases) are acquired from the region of interest in case of a contrast-enhanced abdominal CT examination. The majority of the existing methods, however, use only the portal-venous image to segment the liver. This paper presents a method that automatically segments the liver by combining more phases of the contrast-enhanced CT examination. The method uses region-growing facilitated by pre- and post-processing functions, which incorporate anatomical and multi-phase information to eliminate over- and under-segmentation. Another method, which uses only the portal-venous phase to segment the liver automatically, is also presented. Both methods were evaluated using different datasets, which showed that the result of multi-phase method can be used without or after minor correction in nearly 94% of the cases, and the single-phase method can provide result comparable with non-expert manual segmentation in 90% of the cases. The comparison of the two methods demonstrates that automatic segmentation is more reliable when the information of more phases is combined.

  5. Optimization of a Spectral Contrast Enhancement Algorithm for Cochlear Implants Based on a Vowel Identification Model.

    PubMed

    Nogueira, Waldo; Rode, Thilo; Büchner, Andreas

    2016-01-01

    Speech intelligibility achieved with cochlear implants (CIs) shows large variability across different users. One reason that can explain this variability is the CI user's individual electrode nerve interface which can impact the spectral resolution they can achieve. Spectral resolution has been reported to be related to vowel and consonant recognition in CI listeners. One measure of spectral resolution is the spectral modulation threshold (SMT), which is defined as the smallest detectable spectral contrast in a stimulus. In this study we hypothesize that an algorithm that improves SMT may improve vowel identification, and consequently produce an improvement in speech understanding for CIs. With this purpose we implemented an algorithm, termed spectral contrast enhancement (SCE) that emphasizes peaks with respect to valleys in the audio spectrum. This algorithm can be configured with a single parameter: the amount of spectral contrast enhancement entitled "SCE factor". We would like to investigate whether the "SCE factor" can be individualized to each CI user. With this purpose we used a vowel identification model to predict the performance produced by the SCE algorithm with different "SCE factors" in a vowel identification task.In five CI users the new algorithm has been evaluated using a SMT task and a vowel identification task. The tasks were performed for SCE factors of 0 (no enhancement), 2 and 4. In general it seems that increasing the SCE factor produces a decrease in performance in both the SMT threshold and vowel identification.

  6. Nanoparticle-based highly sensitive MRI contrast agents with enhanced relaxivity in reductive milieu.

    PubMed

    Sigg, Severin J; Santini, Francesco; Najer, Adrian; Richard, Pascal U; Meier, Wolfgang P; Palivan, Cornelia G

    2016-08-01

    Current magnetic resonance imaging (MRI) contrast agents often produce insufficient contrast for diagnosis of early disease stages, and do not sense their biochemical environments. Herein, we report a highly sensitive nanoparticle-based MRI probe with r1 relaxivity up to 51.7 ± 1.2 mM(-1) s(-1) (3T). Nanoparticles were co-assembled from Gd(3+) complexed to heparin-poly(dimethylsiloxane) copolymer, and a reduction-sensitive amphiphilic peptide serving to induce responsiveness to environmental changes. The release of the peptide components leads to a r1 relaxivity increase under reducing conditions and increases the MRI contrast. In addition, this MRI probe has several advantages, such as a low cellular uptake, no apparent cellular toxicity (tested up to 1 mM Gd(3+)), absence of an anticoagulation property, and a high shelf stability (no increase in free Gd(3+) over 7 months). Thus, this highly sensitive T1 MRI contrast nanoparticle system represents a promising probe for early diagnosis through possible accumulation and contrast enhancement within reductive extracellular tumour tissue. PMID:27435820

  7. The Effects of Applying Breast Compression in Dynamic Contrast Material–enhanced MR Imaging

    PubMed Central

    Macura, Katarzyna J.; Kamel, Ihab R.; Bluemke, David A.; Jacobs, Michael A.

    2014-01-01

    Purpose To evaluate the effects of breast compression on breast cancer masses, contrast material enhancement of glandular tissue, and quality of magnetic resonance (MR) images in the identification and characterization of breast lesions. Materials and Methods This was a HIPAA-compliant, institutional review board–approved retrospective study, with waiver of informed consent. Images from 300 MR imaging examinations in 149 women (mean age ± standard deviation, 51.5 years ± 10.9; age range, 22–76 years) were evaluated. The women underwent diagnostic MR imaging (no compression) and MR-guided biopsy (with compression) between June 2008 and February 2013. Breast compression was expressed as a percentage relative to the noncompressed breast. Percentage enhancement difference was calculated between noncompressed- and compressed-breast images obtained in early and delayed contrast-enhanced phases. Breast density, lesion type (mass vs non-masslike enhancement [NMLE]), lesion size, percentage compression, and kinetic curve type were evaluated. Linear regression, receiver operating characteristic (ROC) curve analysis, and κ test were performed. Results Mean percentage compression was 31.3% ± 9.2 (range, 5.8%–53.2%). Percentage enhancement was higher in noncompressed- versus compressed-breast studies in early (146% ± 66 vs 107% ± 42, respectively; P < .001) and delayed (158% ± 68 vs 107% ± 42, respectively; P = .1) phases. Among breast lesions, 12% (seven of 59) were significantly smaller when compressed, which led to underestimation of TNM classification (P < .001). Breast masses (n = 35) showed significantly higher early percentage enhancement (157% ± 71) than lesions with NMLE (n = 15, 120% ± 40; P = .02) and a percentage enhancement difference (47.5% ± 64 vs 17% ± 28, respectively; P = .023). Kinetic curve performance for identifying invasive cancer decreased after compression (area under ROC curve = 0.53 vs 0.71, respectively; P = .02). Breast compression

  8. Imaging of the intracranial venous system with a contrast-enhanced volumetric interpolated examination.

    PubMed

    Wetzel, Stephan G; Law, Meng; Lee, Vivian S; Cha, Soonmee; Johnson, Glyn; Nelson, Kim

    2003-05-01

    A contrast-enhanced interpolated, three-dimensional (3D) gradient-echo MR sequence with asymmetric k-space sampling, which we refer to as volumetric interpolated brain examination (VIBE), was evaluated for its depiction of the normal intracranial venous system and compared with two-dimensional (2D) time-of-flight (TOF) MR venography (MRV). Fifteen subjects underwent contrast-enhanced VIBE imaging (TR/TE 8 ms/4.4 ms, flip angle 18 degrees, acquisition time, 2 min 20 s, voxel size approximately 1.5 mm(3)) and standard 2D TOF MRV (TR/TE 27 ms/9 ms, flip angle 35 degrees ). The presence of 19 venous structures per subject was assessed on maximum intensity projections (MIP) of the whole data set (whole-brain MIP) and on MIP images reconstructed spontaneously from source images (interactive MIP/source images). Results from a consensus reading where all imaging techniques and display modalities were available were taken as the standard of reference for the presence of venous structures. In addition, 10 subjects underwent both unenhanced and enhanced VIBE imaging. The value of subtracted data sets (unenhanced VIBE subtracted from enhanced VIBE) was then evaluated. Overall, VIBE provided a superior visualization of the cerebral veins than 2D TOF MRV (VIBE, sensitivity (reader 1/reader 2): 98%/99%, negative predictive value 64%/71%; TOF sensitivity: 85%/84%, negative predictive value 15%/15%; Wilcoxon signed-rank test VIBE vs TOF, p<0.001 for both readers). The VIBE interactive MIP/source images were superior to whole-brain MIP reconstructions. Image subtraction was not necessary for delineation of venous structures but improved small vein conspicuity. Contrast-enhanced VIBE acquisitions are faster and enable a visualization of the normal intracranial venous system superior to that of 2D TOF MRV.

  9. Enhancing topology adaptation in information-sharing social networks

    NASA Astrophysics Data System (ADS)

    Cimini, Giulio; Chen, Duanbing; Medo, Matúš; Lü, Linyuan; Zhang, Yi-Cheng; Zhou, Tao

    2012-04-01

    The advent of the Internet and World Wide Web has led to unprecedent growth of the information available. People usually face the information overload by following a limited number of sources which best fit their interests. It has thus become important to address issues like who gets followed and how to allow people to discover new and better information sources. In this paper we conduct an empirical analysis of different online social networking sites and draw inspiration from its results to present different source selection strategies in an adaptive model for social recommendation. We show that local search rules which enhance the typical topological features of real social communities give rise to network configurations that are globally optimal. These rules create networks which are effective in information diffusion and resemble structures resulting from real social systems.

  10. Conventional and contrast-enhanced ultrasound assessment of craniocerebral gunshot wounds.

    PubMed

    Deng, D; Dan, G; Tao, J; Wu, X-B; Chen, Z; Chang, M; Liao, M-S; He, F

    2015-01-01

    This study aimed to investigate the characteristic features of craniocerebral gunshot wounds by conventional ultrasound (CUS) and evaluate the efficacy of contrast-enhanced ultrasound (CEUS) in differentiation of tissue condition in wounds. Twenty crossbreed dogs (treatment: N = 15; control: N = 5) were used in the study. Pipe-shaped hyperechoes of varying size were found by CUS in most of the treated animals. The echoic areas were distinct from the neighboring brain tissue and did not change with time. CEUS revealed that the pipe-shaped echo was unenhanced in majority of the injured brains and the surrounding tissue was either heterogeneously enhanced or unenhanced. Pathological analysis confirmed that the contrast-filling-defect area indicated necrotic tissue and the heterogeneous minimally enhanced areas indicated degenerative tissue. CUS imaging enabled detection of hematomas and CEUS indicated that the filling defect was in the center of the hematoma, with enhancement gradually increasing towards the periphery. CUS could effectively detect a wound tract, hematoma, and the craniocerebral area injured by a gunshot, while CEUS could accurately reveal necrotic tissue in the injured area and differentiate the degenerative from normal tissue.

  11. Contrast-enhanced ultrasound (CEUS) for the study of peripheral lung lesions: a preliminary study.

    PubMed

    Sperandeo, Marco; Sperandeo, Giuseppe; Varriale, Antonio; Filabozzi, Paola; Decuzzi, Marco; Dimitri, Lucia; Vendemiale, Gianluigi

    2006-10-01

    The use of contrast-enhanced ultrasound (CEUS) for the study of peripheral lung lesions has never been systematically investigated. We evaluated the CEUS patterns of 98 peripheral lung lesions before performing US-guided fine-needle biopsies (FNB). The examinations were done with an Esaote Technos MPX scanner in the harmonic mode with a mechanical index of 0.04 or less. Contrast enhancement was achieved with a 4.8 mL bolus of SonoVue (Bracco) administered via an antecubital vein. All FNBs performed under CEUS guidance were adequate for pathologic diagnosis. Seventy-eight lesions were malignant: 33 (41.9%) were adenocarcinomas, 29 (36.5%) were squamous-cell carcinomas, 13 (17.6%) were undifferentiated large-cell carcinomas and the remaining three (4.1%) were small-cell carcinomas. All presented intralesional enhancement consistent with tumor neovascularization. In some cases, there were unenhanced areas consistent with zones of necrosis and these areas were avoided during FNB. The other 20 lesions were benign (four lipomas, two fibrous lung tumor, two noncaseous granulomas, six abscesses, one rheumatoid nodule, one histiocytosis X, one chondroid hamartoma, one sclerosing hemangioma, two sarcoid nodules) and none presented intralesional enhancement. This initial and admittedly limited experience suggests that CEUS may provide diagnostically useful information on peripheral lung lesions and increase the diagnostic yield of transthoracic FNB by reducing the risk of inadequate tissue sampling.

  12. Performance Enhancement of Pharmacokinetic Diffuse Fluorescence Tomography by Use of Adaptive Extended Kalman Filtering.

    PubMed

    Wang, Xin; Wu, Linhui; Yi, Xi; Zhang, Yanqi; Zhang, Limin; Zhao, Huijuan; Gao, Feng

    2015-01-01

    Due to both the physiological and morphological differences in the vascularization between healthy and diseased tissues, pharmacokinetic diffuse fluorescence tomography (DFT) can provide contrast-enhanced and comprehensive information for tumor diagnosis and staging. In this regime, the extended Kalman filtering (EKF) based method shows numerous advantages including accurate modeling, online estimation of multiparameters, and universal applicability to any optical fluorophore. Nevertheless the performance of the conventional EKF highly hinges on the exact and inaccessible prior knowledge about the initial values. To address the above issues, an adaptive-EKF scheme is proposed based on a two-compartmental model for the enhancement, which utilizes a variable forgetting-factor to compensate the inaccuracy of the initial states and emphasize the effect of the current data. It is demonstrated using two-dimensional simulative investigations on a circular domain that the proposed adaptive-EKF can obtain preferable estimation of the pharmacokinetic-rates to the conventional-EKF and the enhanced-EKF in terms of quantitativeness, noise robustness, and initialization independence. Further three-dimensional numerical experiments on a digital mouse model validate the efficacy of the method as applied in realistic biological systems. PMID:26089975

  13. Contrast-enhanced postmortem computed tomography in clinical pathology: enhanced value of 20 clinical autopsies.

    PubMed

    Westphal, Saskia E; Apitzsch, Jonas C; Penzkofer, Tobias; Kuhl, Christiane K; Mahnken, Andreas H; Knüchel, Ruth

    2014-09-01

    Postmortem computed tomography (PMCT) is a modern tool that complements autopsy diagnostics. In clinical autopsies, a major cause of death is cardiovascular disease. To improve the performance of PMCT in cardiovascular disease, full body angiography was developed (PMCT angiography [PMCTA]). Twenty PMCTA scans generated before autopsy were compared with native PMCT and clinical autopsy. The objective of the study was to quantify the additional diagnostic value of adding angiography to native imaging and to compare PMCT and PMCTA findings to autopsy findings. The diagnosis of the cause of death was identical or overlapped in 80% of the cases that used PMCTA and 70% that used PMCT. The additional diagnostic yield given by PMCT and PMCTA in combination with autopsy was 55%. PMCT yielded additional diagnoses in the musculoskeletal system. The greatest additional diagnostic value of PMCTA was in association with cardiovascular diagnoses. The accuracy of PMCTA for cardiac causes of death was 80%, and the positive predictive value was 90%. The findings indicate that native PMCT cannot display the cardiovascular system sufficiently clearly for high-quality diagnostic assessment. However, PMCTA is a powerful tool in autopsy cases with a history of cardiovascular disease and/or a suspected cardiovascular cause of death. The combination of PMCTA and clinical autopsy enhances diagnostic quality and completeness of the autopsy report. Furthermore, in cases without consent or with a restricted consent for clinical autopsy, PMCTA has the potential to provide information on cardiovascular causes of death.

  14. Contrast-enhanced color Doppler ultrasonography increases diagnostic accuracy for soft tissue tumors.

    PubMed

    Oebisu, Naoto; Hoshi, Manabu; Ieguchi, Makoto; Takada, Jun; Iwai, Tadashi; Ohsawa, Masahiko; Nakamura, Hiroaki

    2014-10-01

    Resolution of ultrasonography (US) has undergone marked development. Additionally, a new-generation contrast medium (Sonazoid) used for US is newly available. Contrast-enhanced US has been widely used for evaluating several types of cancer. In the present study, we evaluated the ability of color Doppler US (CDUS) and Sonazoid to differentiate between benign and malignant soft tissue tumors. A total of 180 patients (87 male, 93 female) were enrolled in the present study. The patient ages ranged from 1 to 91 years (mean 58.1±20.0 years). The maximum size, depth, tumor margins, shape, echogenicity and textural pattern were measured on gray-scale images. CDUS was used to evaluate the intratumoral blood flow with and without Sonazoid. Peak systolic flow velocity (Vp), mean flow velocity (Vm), resistivity index (RI) and pulsatility index (PI) of each detected intratumoral artery were automatically calculated with power Doppler US (PDUS). The present study included 118 benign and 62 malignant tumors. Statistical significances were found in size, depth, tumor margin and textural pattern but not in shape or echogenicity on gray-scale images. Before Sonazoid injection, CDUS findings showed 55% sensitivity, 77% specificity and 69% accuracy, whereas contrast-enhanced CDUS showed 87% sensitivity, 68% specificity and 74% accuracy. There were no statistically significant differences between malignant and benign tumors regarding the mean Vp, Vm, RI and PI values determined on PDUS. In conclusion, contrast-enhanced CDUS proved to be a reliable diagnostic tool for detecting malignant potential in soft tissue tumors.

  15. Phase contrast enhancement of x-ray mammography: a design study.

    PubMed

    Kotre, C J; Birch, I P

    1999-11-01

    This paper explores the application to mammography of phase contrast produced by variations in x-ray refractive index. As a spatially coherent x-ray beam propagates through an x-ray transparent medium, the phase of the incident wavefront becomes modified in a manner related to the electron density of the medium. The resulting phase gradient across the wavefront is equivalent to a small change in direction of the propagation of the wave. For a general object, the change in propagation direction will vary from point to point depending on the structures within the object. The net effect can be recorded in a radiographic image using an appropriate geometry to produce the visual appearance of edge enhancement at interfaces between materials with differing x-ray refractive indices. Normally these materials will also have differences in attenuation coefficient, so the overall effect is to increase the visibility of interfaces between materials. It is proposed that mammographic images can be subtly enhanced by the use of phase contrast information to overcome some of the known limitations of the imaging process whilst leaving the gross radiological appearance of the images substantially unchanged. The design trade-offs required to utilize phase contrast information were investigated using a conventional mammographic x-ray generator and film-screen system. The Leeds TORMAM mammographic image quality test object was then used to demonstrate a considerable improvement in image quality for the phase contrast enhanced images over those produced in the conventional geometry with no increase in radiation dose to the patient. The results are discussed in terms of their possible practical application.

  16. Broad scale agreement between intertidal habitats and adaptive traits on a basis of contrasting population genetic structure

    NASA Astrophysics Data System (ADS)

    Zardi, G. I.; Nicastro, K. R.; Ferreira Costa, J.; Serrão, E. A.; Pearson, G. A.

    2013-10-01

    Understanding the extent to which neutral processes and adaptive divergence shape the spatial structure of natural populations is a major goal in evolutionary biology and is especially important for the identification of significant levels of biodiversity. Our results identified replicated habitat-specific (adaptive) phenotypic divergence in the brown macroalga Fucus vesiculosus that is independent of population (neutral) genetic structure. F. vesiculosus inhabits contiguous and contrasting marine to estuarine intertidal habitats. Combining analyses of genetic and phenotypic traits of populations living under differential selective regimes (estuaries and open coast), we investigated levels of neutral genetic differentiation and adaptive physiological responses to emersion stress. In southwest England (SW UK) and northern Iberia (N. Iberia), populations living in estuaries and marine coastal habitats were genetically characterized at six microsatellite loci. In N. Iberia, two clades with limited admixture were recovered, each including one open coast site and the adjacent estuarine location. In contrast, SW UK samples clustered according to habitat and formed three distinct groups of genotypes; one including the two open coast locations and the other two representing each of the estuarine sites. Temperature loggers revealed distinct emersion regimes that characterized each habitat type independently of the region, while water and air temperature profiles showed site-specific trends. Despite acclimation under usual conditions, trait means of emersion stress resilience showed a strong phenotypic divergence between habitats, consistent with environmental clines in exposure time observed in the different habitats. We demonstrate that neutral genetic clusters do not reflect locally adapted population units. Our results identified replicated habitat-specific (adaptive) phenotypic divergence that is independent of population (neutral) genetic structure in F. vesiculosus

  17. Generation and modelling of megavoltage photon beams for contrast-enhanced radiation therapy

    NASA Astrophysics Data System (ADS)

    Robar, J. L.

    2006-11-01

    Contrast-enhanced radiation therapy (CERT) is a treatment approach involving the irradiation of tumours containing high atomic number (Z) contrast media, using low-quality x-ray beams. This work describes the experimental generation of x-ray beams using a linear accelerator with low-Z target materials (beryllium and aluminium), in order to produce photon energy spectra appropriate for CERT. Measurements were made to compare the experimental beams to conventional linear accelerator photon beams in terms of per cent depth dose. Monte Carlo simulation was used to model the generation of each beam, and models were validated against experimental measurement. Validated models were used to demonstrate changes in photon spectra as well as to quantify the variation of tumour dose enhancement with iodinated contrast medium concentration in a simulated tumour volume. Finally, the ratio of the linear attenuation coefficient for iodinated contrast medium relative to water was determined experimentally as a function of iodine concentration. Beams created with low-Z targets show significant changes in energy spectra compared to conventional beams. For the 4 MeV/Be beam, for example, 33% of photons have energies below 60 keV. Measurements and calculation show that both the linear attenuation coefficient ratio and dose enhancement factor (DEF) increase most rapidly at concentrations below 46 mg I ml-1. There is a significant dependence of DEF on electron energy and a lesser dependence on target material. The 4 MeV/Be beam is the most promising in terms of magnitude of DEF—for example, DEF values of 1.16 and 1.29 are obtained for concentrations of 20 mg I ml-1 and 50 mg I ml-1, respectively. DEF will increase or decrease, respectively, for shallower or deeper tumours at a rate of approximately 1.1% cm-1. In summary, we show that significant dose enhancement is possible by altering the linear accelerator target and filtration, but the magnitude is highly dependent on contrast

  18. Contrast-agent-enhanced magnetic resonance imaging: early detection of neoplastic lesions of the CNS

    NASA Astrophysics Data System (ADS)

    Carvlin, Mark J.; Rosa, Louis; Rajan, Sunder S.; Francisco, John

    1991-06-01

    Even though the intrinsic soft tissue contrast sensitivity of magnetic resonance imaging (MRI) affords excellent visualization of anatomic detail, certain pathologic processes may be diagnosed earlier with the administration of a contrast-enhancing agent. At present there is one agent, gadopentetate dimeglumine, GdDTPA, that has received FDA approval for use in the MR scanning of the brain and spine in human patients. This paramagnetic chelate distributes throughout the extracellular fluid space as dictated by capillary permeability so that abnormal vascularity and sites of blood-CNS barrier breakdown are highlighted. Primary neoplastic disease, metastases, meningeal extension, residual and recurrent tumor have been found to be better distinguished in MR images acquired after administration of GdDTPA. Routine administration of GdDTPA for cranial imaging has resulted in the discovery of otherwise occult lesions in approximately 3 of patients. Although the clinical utility and high therapeutic safety index of the first approved magnetic resonance contrast agent, GdDTPA, have been well established, other contrast agents, having different physical, chemical and biological properties, may offer improved sensitivity and bio-specificity. Agents currently being evaluated in vivo include: low osmolal paramagnetic chelates, superparamagnetic particles, metalloporphyrins, liposome encapsulated agents, perfluorocarbons, intravascular macromolecular chelate complexes and labeled monoclonal antibodies. Concurrent with advances in the development of new compounds, innovations in scanning hardware, pulse sequence design and image post-processing are helping to extend the efficacy of contrast media. Additional clinical experience will indicate which contrast agents and which MR techniques can best facilitate the early detection of specific neoplastic lesions.

  19. Efficacy of contrast-enhanced ultrasound washout rate in predicting hepatocellular carcinoma differentiation.

    PubMed

    Feng, Yan; Qin, Xia-Chuan; Luo, Yan; Li, Yong-Zhong; Zhou, Xiang

    2015-06-01

    The aim of this retrospective study was to evaluate the efficacy of contrast-enhanced ultrasound (CEUS) washout rate in predicting hepatocellular carcinoma (HCC) differentiation. Two hundred seventy-one patients underwent liver resection for HCC between April 2008 and December 2012 after being examined by CEUS using the contrast agent SonoVue with a low mechanical index (<0.1) in a routine procedure. Contrast agent washout rates obtained from video images were divided into four categories from slow to fast: WR1 = no washout in all phases (slowest); WR2 = washout after 120 s from contrast injection (late-phase washout); WR3 = washout between 41 and 120 s from contrast injection (portal venous washout); WR4 = washout before 40 s from contrast injection (fastest washout rate). HCC nodules were graded as well, moderately and poorly differentiated. Spearman rank correlation and χ(2)-tests were used to assess group relationships and differences. Receiver operating characteristic curve analysis was used to determine the diagnostic predictive value of CEUS. Among the 271 patients, 18 (6.6%) had well differentiated, 150 (55.4%) had moderately differentiated and 103 (38.0%) had poorly differentiated HCC. Statistical tests indicated that washout rate was significantly correlated with tumor differentiation (p < 0.05), and the poorly differentiated HCCs had earlier washout. At the cutoff point of WR4, CEUS based on washout rate performed poorly in distinguishing poorly differentiated from moderately and well-differentiated HCCs, with a sensitivity, specificity and accuracy (area under the curve) of 24%, 97% and 0.68, respectively. However, at the cutoff point of WR2, the sensitivity, specificity and accuracy of CEUS in differentiating well-differentiated HCC from other HCCs were significantly better: 98%, 78% and 0.96, respectively. Thus, CEUS washout rate may have a role in identifying patients with well-differentiated HCC.

  20. Engineered iron-oxide-based nanoparticles as enhanced T1 contrast agents for efficient tumor imaging.

    PubMed

    Zhou, Zijian; Wang, Lirong; Chi, Xiaoqin; Bao, Jianfeng; Yang, Lijiao; Zhao, Wenxiu; Chen, Zhong; Wang, Xiaomin; Chen, Xiaoyuan; Gao, Jinhao

    2013-04-23

    We report the design and synthesis of small-sized zwitterion-coated gadolinium-embedded iron oxide (GdIO) nanoparticles, which exhibit a strong T1 contrast effect for tumor imaging through enhanced permeation and retention effect and the ability to clear out of the body in living subjects. The combination of spin-canting effects and the collection of gadolinium species within small-sized GdIO nanoparticles led to a significantly enhanced T1 contrast effect. For example, GdIO nanoparticles with a diameter of ∼4.8 nm exhibited a high r1 relaxivity of 7.85 mM(-1)·S(-1) and a low r2/r1 ratio of 5.24. After being coated with zwitterionic dopamine sulfonate molecules, the 4.8 nm GdIO nanoparticles showed a steady hydrodynamic diameter (∼5.2 nm) in both PBS buffer and fetal bovine serum solution, indicating a low nonspecific protein absorption. This study provides a valuable strategy for the design of highly sensitive iron-oxide-based T1 contrast agents with relatively long circulation half-lives (∼50 min), efficient tumor passive targeting (SKOV3, human ovarian cancer xenograft tumor as a model), and the possibility of rapid renal clearance after tumor imaging.

  1. Optimal Analysis Method for Dynamic Contrast-Enhanced Diffuse Optical Tomography

    PubMed Central

    Ghijsen, Michael; Lin, Yuting; Hsing, Mitchell; Nalcioglu, Orhan; Gulsen, Gultekin

    2011-01-01

    Diffuse Optical Tomography (DOT) is an optical imaging modality that has various clinical applications. However, the spatial resolution and quantitative accuracy of DOT is poor due to strong photon scatting in biological tissue. Structural a priori information from another high spatial resolution imaging modality such as Magnetic Resonance Imaging (MRI) has been demonstrated to significantly improve DOT accuracy. In addition, a contrast agent can be used to obtain differential absorption images of the lesion by using dynamic contrast enhanced DOT (DCE-DOT). This produces a relative absorption map that consists of subtracting a reconstructed baseline image from reconstructed images in which optical contrast is included. In this study, we investigated and compared different reconstruction methods and analysis approaches for regular endogenous DOT and DCE-DOT with and without MR anatomical a priori information for arbitrarily-shaped objects. Our phantom and animal studies have shown that superior image quality and higher accuracy can be achieved using DCE-DOT together with MR structural a priori information. Hence, implementation of a combined MRI-DOT system to image ICG enhancement can potentially be a promising tool for breast cancer imaging. PMID:21811492

  2. Polarization sensitivity as a visual contrast enhancer in the Emperor dragonfly larva, Anax imperator.

    PubMed

    Sharkey, Camilla R; Partridge, Julian C; Roberts, Nicholas W

    2015-11-01

    Polarization sensitivity (PS) is a common feature of invertebrate visual systems. In insects, PS is well known for its use in several different visually guided behaviours, particularly navigation and habitat search. Adult dragonflies use the polarization of light to find water but a role for PS in aquatic dragonfly larvae, a stage that inhabits a very different photic environment to the adults, has not been investigated. The optomotor response of the larvae of the Emperor dragonfly, Anax imperator Leach 1815, was used to determine whether these larvae use PS to enhance visual contrast underwater. Two different light scattering conditions were used to surround the larval animals: a naturalistic horizontally polarized light field and a non-naturalistic weakly polarized light field. In both cases these scattering light fields obscured moving intensity stimuli that provoke an optokinetic response in the larvae. Animals were shown to track the movement of a square-wave grating more closely when it was viewed through the horizontally polarized light field, equivalent to a similar increase in tracking ability observed in response to an 8% increase in the intensity contrast of the stimuli. Our results suggest that larval PS enhances the intensity contrast of a visual scene under partially polarized lighting conditions that occur naturally in freshwater environments. PMID:26385333

  3. Preserving Enhancement in Freeze-Dried Contrast Agent ST68: Examination of Excipients

    PubMed Central

    Solis, Carl; Forsberg, Flemming; Wheatley, Margaret A.

    2013-01-01

    The perfluorcarbon (perfluorobutane) ultrasound contrast agent ST68, composed of sonicated mixtures of non-ionic surfactants, is stable in solution for only a few weeks at 4°C. Freeze-drying critically diminished ST68’s ability to reflect ultrasound (its echogenicity). A method of incorporating specific lyoprotectants before lyophilization was investigated. Reintroduction of perfluorobutane to the protected freeze-dried sample, followed by reconstituting with preserved echogenicity. Glucose, trehalose, sucrose, and mannitol were tested at 100 mM and in vitro echogenicity data was collected from samples with dose concentrations of 50 µl/l to 300 µl/l. Glucose was found to be the best lyoprotectant providing an average (n=3) maximum peak enhancement of 23.2 ± 1.2 dB in vitro, measured at 5 MHz, 684 kPa, and a pulse repetition frequency (PRF) of 100 Hz (p<0.05 over freeze-dried ST68 control) and 20.8 ± 0.8 dB in vivo in New Zealand white rabbits at 5 MHz and a PRF of 6.7 kHz. Pulse inversion harmonic US images of a rabbit kidney, pre- and post-contrast injection (0.1 ml/kg), showed excellent enhancement and clear vascular delineation, similar to that of the original agent. For the first time this contrast agent can be successfully freeze-dried yielding a longer self-life without the need for refrigeration. PMID:20540998

  4. Color contrast enhancement for color night vision based on color mapping

    NASA Astrophysics Data System (ADS)

    Qian, Xiaoyan; Han, Lei; Wang, Yujin; Wang, Bangfeng

    2013-03-01

    The increasing availability and deployment of imaging sensors operating in multiple spectral bands has led to a large research effort in image fusion, bringing a lot of pixel-level color fusion algorithms. Color constancy and color contrast are two important topics for color image fusion. However, there is no work considering these two aspects in the meanwhile. The paper focuses on enhancing the color contrast between targets and their backgrounds and maintaining the color constancy. Firstly, a group of visible and infrared images are rendered with natural colors with color contrast enhancement algorithm. Then a color reference palette is derived from source images and their corresponding fused results. To enrich this palette, the nearest Euclidean distance determines the absent colors. The complete palette can be deployed in real-time to different multi-band image sequences of similar scenes. Experimental results based on different data sets show that the targets are popped out with intense colors while backgrounds present natural color appearance. Some objective analysis also shows that the presented method not only inherits more detail information from source images but also brings bigger color distance when comparing with the existing algorithms.

  5. Polarization sensitivity as a visual contrast enhancer in the Emperor dragonfly larva, Anax imperator.

    PubMed

    Sharkey, Camilla R; Partridge, Julian C; Roberts, Nicholas W

    2015-11-01

    Polarization sensitivity (PS) is a common feature of invertebrate visual systems. In insects, PS is well known for its use in several different visually guided behaviours, particularly navigation and habitat search. Adult dragonflies use the polarization of light to find water but a role for PS in aquatic dragonfly larvae, a stage that inhabits a very different photic environment to the adults, has not been investigated. The optomotor response of the larvae of the Emperor dragonfly, Anax imperator Leach 1815, was used to determine whether these larvae use PS to enhance visual contrast underwater. Two different light scattering conditions were used to surround the larval animals: a naturalistic horizontally polarized light field and a non-naturalistic weakly polarized light field. In both cases these scattering light fields obscured moving intensity stimuli that provoke an optokinetic response in the larvae. Animals were shown to track the movement of a square-wave grating more closely when it was viewed through the horizontally polarized light field, equivalent to a similar increase in tracking ability observed in response to an 8% increase in the intensity contrast of the stimuli. Our results suggest that larval PS enhances the intensity contrast of a visual scene under partially polarized lighting conditions that occur naturally in freshwater environments.

  6. Preserving enhancement in freeze-dried contrast agent ST68: Examination of excipients.

    PubMed

    Solis, Carl; Forsberg, Flemming; Wheatley, Margaret A

    2010-08-30

    The perfluorcarbon (perfluorobutane) ultrasound contrast agent ST68, composed of sonicated mixtures of non-ionic surfactants, is stable in solution for only a few weeks at 4 degrees C. Freeze-drying critically diminished ST68's ability to reflect ultrasound (its echogenicity). A method of incorporating specific lyoprotectants before lyophilization was investigated. Reintroduction of perfluorobutane to the protected freeze-dried sample, followed by reconstituting with water preserved echogenicity. Glucose, trehalose, sucrose, and mannitol were tested at 100mM and in vitro echogenicity data was collected from samples with dose concentrations of 50-300microl/l. Glucose was found to be the best lyoprotectant providing an average (n=3) maximum peak enhancement of 23.2+/-1.2dB in vitro, measured at 5MHz, 684kPa, and a pulse repetition frequency (PRF) of 100Hz (p<0.05 over freeze-dried ST68 control) and 20.8+/-0.8dB in vivo in New Zealand white rabbits at 5MHz and a PRF of 6.7kHz. Pulse inversion harmonic US images of a rabbit kidney, pre- and post-contrast injection (0.1ml/kg), showed excellent enhancement and clear vascular delineation, similar to that of the original agent. For the first time this contrast agent can be successfully freeze-dried yielding a longer self-life without the need for refrigeration.

  7. Continuous Dynamic Registration of Microvascularization of Liver Tumors with Contrast-Enhanced Ultrasound

    PubMed Central

    Wiesinger, Isabel; Stroszczynski, Christian; Wiggermann, Philipp; Jung, Ernst-Michael

    2014-01-01

    Aim. To evaluate the diagnostic value of quantification of liver tumor microvascularization using contrast-enhanced ultrasound (CEUS) measured continuously from the arterial phase to the late phase (3 minutes). Material and Methods. We present a retrospective analysis of 20 patients with malignant (n = 13) or benign (n = 7) liver tumors. The tumors had histopathologically been proven or clearly identified using contrast-enhanced reference imaging with either 1.5 T MRI (liver specific contrast medium) or triphase CT and follow-up. CEUS was performed using a multifrequency transducer (1–5 MHz) and a bolus injection of 2.4 mL sulphur hexafluoride microbubbles. A retrospective perfusion analysis was performed to determine TTP (time-to-peak), RBV (regional blood volume), RBF (regional blood flow), and Peak. Results. Statistics revealed a significant difference (P < 0.05) between benign and malignant tumors in the RBV, RBF, and Peak but not in TTP (P = 0.07). Receiver operating curves (ROC) were generated for RBV, RBF, Peak, and TTP with estimated ROC areas of 0.97, 0.96, 0.98, and 0.76, respectively. Conclusion. RBV, RBF, and Peak continuously measured over a determined time period of 3 minutes could be of valuable support in differentiating malignant from benign liver tumors. PMID:24991432

  8. Contrast enhancement based on entropy and reflectance analysis for surgical lighting

    NASA Astrophysics Data System (ADS)

    Shen, Junfei; Wang, Huihui; Wu, Yisi; Li, An; Chen, Chi; Zheng, Zhenrong

    2015-07-01

    Light-emitting diode (LED) is the neotype surgical lighting device as an inexpensive and color-variable illumination. A methodology was designed to value the quality of surgical lighting and used to develop an operation lamp with LEDs enhancing the biological contrast. We assembled a modular array of Phillips LEDs as illumination. In the initial experiment, images of porcine heart were carried out in several LED environments and analyzed quantitatively to assess the function of these LEDs in contrast enhancement. Then we measured the reflectance spectrums of blood, fat and other tissues to obtain the spectral comparison. Based on the result, new illuminations with spectral components which differ most in the comparison was developed. Meanwhile, a new evaluation function combining the entropy analysis and brightness contrast was also built to value the quality of these illuminations. Experiments showed biological features are more visible with treated LED illuminations than the broadband lamps. Thus, the synthesis of LED lighting spectra could be adjusted to provide significant tissue identification. Therefore, we believe the new methodology will contribute to the manufacture of high efficient medical illuminations and act the positive role in coming surgical lighting fields.

  9. CONTRAST-ENHANCED MRI OF SUBCHONDRAL CYSTS IN PATIENTS WITH OR AT RISK FOR KNEE OSTEOARTHRITIS: THE MOST STUDY

    PubMed Central

    Crema, M.D.; Roemer, F.W.; Marra, M.D.; Niu, J.; Lynch, J.A.; Felson, D.T.; Guermazi, A.

    2009-01-01

    Objective The aim of the study was 1) to evaluate contrast enhancement patterns of subchondral cysts on magnetic resonance imaging and 2) to discuss possible radiological explanations of cyst enhancement based on existing theories of subchondral cyst formation in osteoarthritis. Materials and Methods The Multicenter Osteoarthritis (MOST) Study is a NIH-funded longitudinal observational study for individuals who have or are at high risk for knee osteoarthritis. All subjects with available non-enhanced and contrast enhanced MRI were included. The tibiofemoral and patellofemoral joints were divided in 14 subregions. The presence and size of subchondral cysts and bone marrow edema-like lesions (BMLs) were scored semiquantitatively in each subregion on non-contrast enhanced MRI from 0 to 3. Enhancement of subchondral cysts was evaluated on contrast enhanced MRI as grade 0 (absent), grade 1 (partial enhancement), or grade 2 (full enhancement). The adjacent articular cartilage was scored in each subregion on non-enhanced MRI as grade 0 (intact), grade 1 (partial thickness loss), or grade 2 (full thickness loss). Results Four hundred knees were included (1 knee per person, 5600 subregions). Subchondral cysts were detected in 260 subregions (4.6%). After intravenous contrast administration, 245 cysts (94.2%) showed full enhancement, 12 (4.6%) showed partial enhancement and 3 (1.2%) showed no enhancement. Enhancing BMLs were found in 237 (91.2%) subregions containing cysts, which were located adjacent or in the middle of BMLs. In 121 subregions (46.5%) having cysts, no adjacent full thickness cartilage loss was detected. Conclusion Most subchondral cysts demonstrated full or partial contrast enhancement, and were located adjacent or in the midst of enhancing BMLs. As pure cystic lesions are not expected to enhance on MRI, the term “subchondral cyst-like bone marrow lesion” might be appropriate to describe these lesions. PMID:19767165

  10. Contrast-enhanced molecular ultrasound differentiates endoglin genotypes in mouse embryos.

    PubMed

    Denbeigh, J M; Nixon, B A; Lee, J J Y; Jerkic, M; Marsden, P A; Letarte, M; Puri, M C; Foster, F S

    2015-01-01

    Targeted ultrasound contrast imaging has the potential to become a reliable molecular imaging tool. A better understanding of the quantitative aspects of molecular ultrasound technology could facilitate the translation of this technique to the clinic for the purposes of assessing vascular pathology and detecting individual response to treatment. The objective of this study was to evaluate whether targeted ultrasound contrast-enhanced imaging can provide a quantitative measure of endogenous biomarkers. Endoglin, an endothelial biomarker involved in the processes of development, vascular homeostasis, and altered in diseases, including hereditary hemorrhagic telangiectasia type 1 and tumor angiogenesis, was the selected target. We used a parallel plate perfusion chamber in which endoglin-targeted (MBE), rat isotype IgG2 control and untargeted microbubbles were perfused across endoglin wild-type (Eng+/+), heterozygous (Eng+/-) and null (Eng-/-) embryonic mouse endothelial cells and their adhesion quantified. Microbubble binding was also assessed in late-gestation, isolated living transgenic Eng+/- and Eng+/+ embryos. Nonlinear contrast-specific ultrasound imaging performed at 21 MHz was used to collect contrast mean power ratios for all bubble types. Statistically significant differences in microbubble binding were found across genotypes for both in vitro (p<0.05) and embryonic studies (p<0.001); MBE binding was approximately twofold higher in Eng+/+ cells and embryos compared with their Eng+/- counterparts. These results suggest that molecular ultrasound is capable of reliably differentiating between molecular genotypes and relating receptor densities to quantifiable molecular ultrasound levels. PMID:25298070

  11. Comparative evaluation of methylene blue and demeclocycline for enhancing optical contrast of gliomas in optical images.

    PubMed

    Wirth, Dennis; Snuderl, Matija; Curry, William; Yaroslavsky, Anna

    2014-09-01

    Contrast agents have shown to be useful in the detection of cancers. The goal of this study was to compare enhancement of brain cancer contrast using reflectance and fluorescence confocal imaging of two fluorophores, methylene blue (MB) and demeclocycline (DMN). MB absorbs light in the red spectral range and fluoresces in the near-infrared. It is safe for in vivo staining of human skin and breast tissue. However, its safety for staining human brain is questionable. Thus, DMN, which absorbs light in the violet spectral range and fluoresces between 470 and 570 nm, could provide a safer alternative to MB. Fresh human gliomas, obtained from surgeries, were cut in half and stained with aqueous solutions of MB and DMN, respectively. Stained tissues were imaged using multimodal confocal microscopy. Resulting reflectance and fluorescence optical images were compared with hematoxylin and eosin histopathology, processed from each imaged tissue. Results indicate that images of tissues stained with either stain exhibit comparable contrast and resolution of morphological detail. Further studies are required to establish the safety and efficacy of these contrast agents for use in human brain.

  12. Comparative evaluation of methylene blue and demeclocycline for enhancing optical contrast of gliomas in optical images

    NASA Astrophysics Data System (ADS)

    Wirth, Dennis; Snuderl, Matija; Curry, William; Yaroslavsky, Anna

    2014-09-01

    Contrast agents have shown to be useful in the detection of cancers. The goal of this study was to compare enhancement of brain cancer contrast using reflectance and fluorescence confocal imaging of two fluorophores, methylene blue (MB) and demeclocycline (DMN). MB absorbs light in the red spectral range and fluoresces in the near-infrared. It is safe for in vivo staining of human skin and breast tissue. However, its safety for staining human brain is questionable. Thus, DMN, which absorbs light in the violet spectral range and fluoresces between 470 and 570 nm, could provide a safer alternative to MB. Fresh human gliomas, obtained from surgeries, were cut in half and stained with aqueous solutions of MB and DMN, respectively. Stained tissues were imaged using multimodal confocal microscopy. Resulting reflectance and fluorescence optical images were compared with hematoxylin and eosin histopathology, processed from each imaged tissue. Results indicate that images of tissues stained with either stain exhibit comparable contrast and resolution of morphological detail. Further studies are required to establish the safety and efficacy of these contrast agents for use in human brain.

  13. Spatial covert attention increases contrast sensitivity across the CSF: support for signal enhancement

    NASA Technical Reports Server (NTRS)

    Carrasco, M.; Penpeci-Talgar, C.; Eckstein, M.

    2000-01-01

    This study is the first to report the benefits of spatial covert attention on contrast sensitivity in a wide range of spatial frequencies when a target alone was presented in the absence of a local post-mask. We used a peripheral precue (a small circle indicating the target location) to explore the effects of covert spatial attention on contrast sensitivity as assessed by orientation discrimination (Experiments 1-4), detection (Experiments 2 and 3) and localization (Experiment 3) tasks. In all four experiments the target (a Gabor patch ranging in spatial frequency from 0.5 to 10 cpd) was presented alone in one of eight possible locations equidistant from fixation. Contrast sensitivity was consistently higher for peripherally- than for neutrally-cued trials, even though we eliminated variables (distracters, global masks, local masks, and location uncertainty) that are known to contribute to an external noise reduction explanation of attention. When observers were presented with vertical and horizontal Gabor patches an external noise reduction signal detection model accounted for the cueing benefit in a discrimination task (Experiment 1). However, such a model could not account for this benefit when location uncertainty was reduced, either by: (a) Increasing overall performance level (Experiment 2); (b) increasing stimulus contrast to enable fine discriminations of slightly tilted suprathreshold stimuli (Experiment 3); and (c) presenting a local post-mask (Experiment 4). Given that attentional benefits occurred under conditions that exclude all variables predicted by the external noise reduction model, these results support the signal enhancement model of attention.

  14. Spatial covert attention increases contrast sensitivity across the CSF: support for signal enhancement.

    PubMed

    Carrasco, M; Penpeci-Talgar, C; Eckstein, M

    2000-01-01

    This study is the first to report the benefits of spatial covert attention on contrast sensitivity in a wide range of spatial frequencies when a target alone was presented in the absence of a local post-mask. We used a peripheral precue (a small circle indicating the target location) to explore the effects of covert spatial attention on contrast sensitivity as assessed by orientation discrimination (Experiments 1-4), detection (Experiments 2 and 3) and localization (Experiment 3) tasks. In all four experiments the target (a Gabor patch ranging in spatial frequency from 0.5 to 10 cpd) was presented alone in one of eight possible locations equidistant from fixation. Contrast sensitivity was consistently higher for peripherally- than for neutrally-cued trials, even though we eliminated variables (distracters, global masks, local masks, and location uncertainty) that are known to contribute to an external noise reduction explanation of attention. When observers were presented with vertical and horizontal Gabor patches an external noise reduction signal detection model accounted for the cueing benefit in a discrimination task (Experiment 1). However, such a model could not account for this benefit when location uncertainty was reduced, either by: (a) Increasing overall performance level (Experiment 2); (b) increasing stimulus contrast to enable fine discriminations of slightly tilted suprathreshold stimuli (Experiment 3); and (c) presenting a local post-mask (Experiment 4). Given that attentional benefits occurred under conditions that exclude all variables predicted by the external noise reduction model, these results support the signal enhancement model of attention.

  15. Programmable Colored Illumination Microscopy (PCIM): A practical and flexible optical staining approach for microscopic contrast enhancement

    NASA Astrophysics Data System (ADS)

    Zuo, Chao; Sun, Jiasong; Feng, Shijie; Hu, Yan; Chen, Qian

    2016-03-01

    Programmable colored illumination microscopy (PCIM) has been proposed as a flexible optical staining technique for microscopic contrast enhancement. In this method, we replace the condenser diaphragm of a conventional microscope with a programmable thin film transistor-liquid crystal display (TFT-LCD). By displaying different patterns on the LCD, numerous established imaging modalities can be realized, such as bright field, dark field, phase contrast, oblique illumination, and Rheinberg illuminations, which conventionally rely on intricate alterations in the respective microscope setups. Furthermore, the ease of modulating both the color and the intensity distribution at the aperture of the condenser opens the possibility to combine multiple microscopic techniques, or even realize completely new methods for optical color contrast staining, such as iridescent dark-field and iridescent phase-contrast imaging. The versatility and effectiveness of PCIM is demonstrated by imaging of several transparent colorless specimens, such as unstained lung cancer cells, diatom, textile fibers, and a cryosection of mouse kidney. Finally, the potentialities of PCIM for RGB-splitting imaging with stained samples are also explored by imaging stained red blood cells and a histological section.

  16. CONTRAST-ENHANCED INTRAVASCULAR ULTRASOUND PULSE SEQUENCES FOR BANDWIDTH-LIMITED TRANSDUCERS

    PubMed Central

    Maresca, David; Renaud, Guillaume; van Soest, Gijs; Li, Xiang; Zhou, Qifa; Shung, K. Kirk; de Jong, Nico; van der Steen, Antonius F. W.

    2013-01-01

    We demonstrate two methods for vasa vasorum imaging using contrast-enhanced intravascular ultrasound, which can be performed using commercial catheters. Plaque neovascularization was recognized as an independent marker of coronary artery plaque vulnerability. IVUS-based methods to image the microvessels available to date require high bandwidth (−6 dB relative frequency bandwidth >70%), which are not routinely available commercially. We explored the potential of ultraharmonic imaging and chirp reversal imaging for vasa vasorum imaging. In vitro recordings were performed on a tissue-mimicking phantom using a commercial ultrasound contrast agent and a transducer with a center frequency of 34 MHz and a −6 dB relative bandwidth of 56%. Acoustic peak pressures <500 kPa were used. A tissue-mimicking phantom with channels down to 200 μm in diameter was successfully imaged by the two contrast detection sequences while the smallest channel stayed invisible in conventional intravascular ultrasound images. Ultraharmonic imaging provided the best contrast agent detection. PMID:23384459

  17. Differential Diagnosis of Arterial Phase Enhanced Hepatic Inflammatory Lesions and Hepatocellular Carcinomas with Contrast-enhanced Ultrasound.

    PubMed

    Yang, Wei; Yan, Kun; Wang, Song; Dai, Ying; Wu, Wei; Yin, Shan-Shan; Chen, Min-Hua

    2016-01-01

    We aimed to investigate the enhancement patterns of contrast-enhanced ultrasound (CEUS) with SonoVue and determine the utility of this method for differential diagnosis between hepatic inflammatory lesions with arterial phase enhancement and hepatocellular carcinomas (HCC). Twenty-three patients with arterial-enhanced inflammatory liver lesions and 46 HCC patients were included. These lesions had been subjected to CEUS examination and confirmed by pathologic results or imaging follow-up for at least 1 y. In the arterial phase of CEUS, 65.2% of the inflammatory lesions showed patchy (slight enhancement with poorly defined margins) or centripetal enhancement, whereas 89.1% of the HCC lesions showed homogeneous or heterogeneous enhancement (p < 0.001). Moreover, 82.6% of the inflammatory lesions had poorly defined margins, and 78.3% were irregular in shape at the peak, whereas 87.0% of the HCC lesions had well-defined margins and 76.1% were regular (both p < 0.001). Feeding vessels were more frequently visualized in HCCs (71.7%) than in inflammatory lesions (26.1%, p < 0.001). Additionally, 88.2% of the internal non-perfused areas in inflammatory lesions were regular in shape, while 68.0% of these areas in HCCs had an irregular shape (p < 0.001). CEUS pattern analysis provides important information for differentiating inflammatory liver lesions and HCCs and is helpful for improving diagnostic accuracy.

  18. Adaptation to climate change: contrasting patterns of thermal-reaction-norm evolution in Pacific versus Atlantic silversides.

    PubMed

    Baumann, Hannes; Conover, David O

    2011-08-01

    How organisms may adapt to rising global temperatures is uncertain, but concepts can emerge from studying adaptive physiological trait variations across existing spatial climate gradients. Many ectotherms, particularly fish, have evolved increasing genetic growth capacities with latitude (i.e. countergradient variation (CnGV) in growth), which are thought to be an adaptation primarily to strong gradients in seasonality. In contrast, evolutionary responses to gradients in mean temperature are often assumed to involve an alternative mode, 'thermal adaptation'. We measured thermal growth reaction norms in Pacific silverside populations (Atherinops affinis) occurring across a weak latitudinal temperature gradient with invariant seasonality along the North American Pacific coast. Instead of thermal adaptation, we found novel evidence for CnGV in growth, suggesting that CnGV is a ubiquitous mode of reaction-norm evolution in ectotherms even in response to weak spatial and, by inference, temporal climate gradients. A novel, large-scale comparison between ecologically equivalent Pacific versus Atlantic silversides (Menidia menidia) revealed how closely growth CnGV patterns reflect their respective climate gradients. While steep growth reaction norms and increasing growth plasticity with latitude in M. menidia mimicked the strong, highly seasonal Atlantic coastal gradient, shallow reaction norms and much smaller, latitude-independent growth plasticity in A. affinis resembled the weak Pacific latitudinal temperature gradient. PMID:21208956

  19. Adaptation to climate change: contrasting patterns of thermal-reaction-norm evolution in Pacific versus Atlantic silversides.

    PubMed

    Baumann, Hannes; Conover, David O

    2011-08-01

    How organisms may adapt to rising global temperatures is uncertain, but concepts can emerge from studying adaptive physiological trait variations across existing spatial climate gradients. Many ectotherms, particularly fish, have evolved increasing genetic growth capacities with latitude (i.e. countergradient variation (CnGV) in growth), which are thought to be an adaptation primarily to strong gradients in seasonality. In contrast, evolutionary responses to gradients in mean temperature are often assumed to involve an alternative mode, 'thermal adaptation'. We measured thermal growth reaction norms in Pacific silverside populations (Atherinops affinis) occurring across a weak latitudinal temperature gradient with invariant seasonality along the North American Pacific coast. Instead of thermal adaptation, we found novel evidence for CnGV in growth, suggesting that CnGV is a ubiquitous mode of reaction-norm evolution in ectotherms even in response to weak spatial and, by inference, temporal climate gradients. A novel, large-scale comparison between ecologically equivalent Pacific versus Atlantic silversides (Menidia menidia) revealed how closely growth CnGV patterns reflect their respective climate gradients. While steep growth reaction norms and increasing growth plasticity with latitude in M. menidia mimicked the strong, highly seasonal Atlantic coastal gradient, shallow reaction norms and much smaller, latitude-independent growth plasticity in A. affinis resembled the weak Pacific latitudinal temperature gradient.

  20. Presynaptic GABA Receptors Mediate Temporal Contrast Enhancement in Drosophila Olfactory Sensory Neurons and Modulate Odor-Driven Behavioral Kinetics

    PubMed Central

    Demir, Mahmut; Gorur-Shandilya, Srinivas; Kunst, Michael; Nitabach, Michael N.

    2016-01-01

    Contrast enhancement mediated by lateral inhibition within the nervous system enhances the detection of salient features of visual and auditory stimuli, such as spatial and temporal edges. However, it remains unclear how mechanisms for temporal contrast enhancement in the olfactory system can enhance the detection of odor plume edges during navigation. To address this question, we delivered to Drosophila melanogaster flies pulses of high odor intensity that induce sustained peripheral responses in olfactory sensory neurons (OSNs). We use optical electrophysiology to directly measure electrical responses in presynaptic terminals and demonstrate that sustained peripheral responses are temporally sharpened by the combined activity of two types of inhibitory GABA receptors to generate contrast-enhanced voltage responses in central OSN axon terminals. Furthermore, we show how these GABA receptors modulate the time course of innate behavioral responses after odor pulse termination, demonstrating an important role for temporal contrast enhancement in odor-guided navigation. PMID:27588305

  1. Presynaptic GABA Receptors Mediate Temporal Contrast Enhancement in Drosophila Olfactory Sensory Neurons and Modulate Odor-Driven Behavioral Kinetics.

    PubMed

    Raccuglia, Davide; Yan McCurdy, Li; Demir, Mahmut; Gorur-Shandilya, Srinivas; Kunst, Michael; Emonet, Thierry; Nitabach, Michael N

    2016-01-01

    Contrast enhancement mediated by lateral inhibition within the nervous system enhances the detection of salient features of visual and auditory stimuli, such as spatial and temporal edges. However, it remains unclear how mechanisms for temporal contrast enhancement in the olfactory system can enhance the detection of odor plume edges during navigation. To address this question, we delivered to Drosophila melanogaster flies pulses of high odor intensity that induce sustained peripheral responses in olfactory sensory neurons (OSNs). We use optical electrophysiology to directly measure electrical responses in presynaptic terminals and demonstrate that sustained peripheral responses are temporally sharpened by the combined activity of two types of inhibitory GABA receptors to generate contrast-enhanced voltage responses in central OSN axon terminals. Furthermore, we show how these GABA receptors modulate the time course of innate behavioral responses after odor pulse termination, demonstrating an important role for temporal contrast enhancement in odor-guided navigation. PMID:27588305

  2. 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.

  3. Evaluation of the thrombus of abdominal aortic aneurysms using contrast enhanced ultrasound - preliminary results

    PubMed Central

    Łukasiewicz, Adam; Garkowski, Adam; Rutka, Katarzyna; Janica, Jacek; Łebkowska, Urszula

    2016-01-01

    It is hypothesized that the degree of vascularization of the thrombus may have a significant impact on the rupture of aortic aneurysms. The presence of neovascularization of the vessel wall and mural thrombus has been confirmed only in histopathological studies. However, no non-invasive imaging technique of qualitative assessment of thrombus and neovascularization has been implemented so far. Contrast-enhanced ultrasound (CEUS) has been proposed as a feasible and minimally invasive technique for in vivo visualization of neovascularization in the evaluation of tumors and atherosclerotic plaques. The aim of this study was the evaluation of mural thrombus and AAAs wall with CEUS. CEUS was performed in a group of seventeen patients with AAAs. The mural thrombus enhancement was recognized in 12 cases, yet no significant correlation between the degree of contrast enhancement and AAAs diameter, thrombus width, and thrombus echogenicity was found. We observed a rise in AAAs thrombus heterogeneity with the increase in the aneurysm diameter (r = 0.62, p = 0.017). In conclusion CEUS can visualize small channels within AAAs thrombus, which could be a result of an ongoing angiogenesis. There is a need for further research to find out whether the degree of vascularization of the thrombus may have a significant impact on the rupture of aneurysms. PMID:27677245

  4. PEGylated polyethylenimine as enhanced T₁ contrast agent for efficient magnetic resonance imaging.

    PubMed

    Zhou, Shengyuan; Wu, Zhenkai; Chen, Xiongsheng; Jia, Lianshun; Zhu, Wei

    2014-07-23

    Currently used small molecular magnetic resonance (MR) imaging contrast agents (CAs) in clinics have relatively short half-lives, which has limited the acquisition of high-resolution organ and angiographic images. Therefore, development of a facile strategy for the synthesis of long-circulating CAs with the transforming potential for MR imaging still remains a great challenge. Here we communicate the design and synthesis of PEGylated polyethylenimine (PEI) and its application as enhanced T1 CA for the long-circulating blood pool as well as efficient organ and tumor imaging. In this study, PEI was covalently grafted with gadolinium (Gd(III)) chelator and mPEG-NHS, followed by acetylation of the remaining amines to improve biocompatibility and prolong circulation time. With the relatively long circulation time (3.8 h), the formed multifunctional PEI (PEI.NHAc-DTPA(Gd(III))-mPEG) can be used as an enhanced T1 CA for blood pool and major organ imaging, and could be cleared from the body 96 h post administration through the urinary system. Importantly, the PEI.NHAc-DTPA(Gd(III))-mPEG complexes displayed a strong T1 contrast effect for tumor imaging through the enhanced permeation and retention effect. These findings suggest that the synthesized PEI.NHAc-DTPA(Gd(III))-mPEG may be used as a promising CA for T1 MR imaging of various biological systems.

  5. Contrast enhanced ultrasonography of kidney in conscious and anesthetized beagle dogs

    PubMed Central

    CHOI, Soo-Young; JEONG, Woo-Chang; LEE, Young-Won; CHOI, Ho-Jung

    2015-01-01

    Contrast enhanced ultrasound (CEUS) is useful to evaluate tissue perfusion in the kidney. In veterinary medicine, sedation or anesthesia may be required in uncooperative or panting patients. The aim of this study was to evaluate and compare the normal kidney perfusion patterns in conscious and anesthetized dogs using CEUS. Eight healthy beagles were used in this study. Scanning was performed in conscious dogs using manual restraint (conscious group), or under general anesthesia using tiletamine-zolazepam and medetomidine (TZM group) or medetomidine (M group). The contrast agent (Sonovue®) was administered as an IV bolus. The peak intensity (PI), time to peak enhancement from injection (TTP0) and the time to peak enhancement from the initial rise (TTPup), upslope, downslope and area under the curve (AUC) were analyzed. Compared to the cortical values in the conscious group, TTP0 was significantly delayed in the TZM group, and upslope, TTP0 and TTPup were significantly different in the M group. The AUCs in the TZM and M groups were not different from those in the conscious group. The upslope of renal medullary perfusion was significantly decreased in the TZM and M groups. TTP0 and TTPup were also significantly delayed in these groups. The AUC of the medulla was significantly decreased in the M group. Therefore, TZM is useful as an anesthetic protocol when performing CEUS, and the obtained data may serve as reference values in the evaluation of renal perfusion using CEUS in dogs under anesthesia. PMID:26412201

  6. Evaluation of the thrombus of abdominal aortic aneurysms using contrast enhanced ultrasound - preliminary results

    NASA Astrophysics Data System (ADS)

    Łukasiewicz, Adam; Garkowski, Adam; Rutka, Katarzyna; Janica, Jacek; Łebkowska, Urszula

    2016-09-01

    It is hypothesized that the degree of vascularization of the thrombus may have a significant impact on the rupture of aortic aneurysms. The presence of neovascularization of the vessel wall and mural thrombus has been confirmed only in histopathological studies. However, no non-invasive imaging technique of qualitative assessment of thrombus and neovascularization has been implemented so far. Contrast-enhanced ultrasound (CEUS) has been proposed as a feasible and minimally invasive technique for in vivo visualization of neovascularization in the evaluation of tumors and atherosclerotic plaques. The aim of this study was the evaluation of mural thrombus and AAAs wall with CEUS. CEUS was performed in a group of seventeen patients with AAAs. The mural thrombus enhancement was recognized in 12 cases, yet no significant correlation between the degree of contrast enhancement and AAAs diameter, thrombus width, and thrombus echogenicity was found. We observed a rise in AAAs thrombus heterogeneity with the increase in the aneurysm diameter (r = 0.62, p = 0.017). In conclusion CEUS can visualize small channels within AAAs thrombus, which could be a result of an ongoing angiogenesis. There is a need for further research to find out whether the degree of vascularization of the thrombus may have a significant impact on the rupture of aneurysms.

  7. Contrast enhancement based on layered difference representation of 2D histograms.

    PubMed

    Lee, Chulwoo; Lee, Chul; Kim, Chang-Su

    2013-12-01

    A novel contrast enhancement algorithm based on the layered difference representation of 2D histograms is proposed in this paper. We attempt to enhance image contrast by amplifying the gray-level differences between adjacent pixels. To this end, we obtain the 2D histogram h(k, k + l ) from an input image, which counts the pairs of adjacent pixels with gray-levels k and k + l , and represent the gray-level differences in a tree-like layered structure. Then, we formulate a constrained optimization problem based on the observation that the gray-level differences, occurring more frequently in the input image, should be more emphasized in the output image. We first solve the optimization problem to derive the transformation function at each layer. We then combine the transformation functions at all layers into the unified transformation function, which is used to map input gray-levels to output gray-levels. Experimental results demonstrate that the proposed algorithm enhances images efficiently in terms of both objective quality and subjective quality.

  8. Dynamic contrast enhanced CT in nodule characterization: How we review and report.

    PubMed

    Qureshi, Nagmi R; Shah, Andrew; Eaton, Rosemary J; Miles, Ken; Gilbert, Fiona J

    2016-01-01

    Incidental indeterminate solitary pulmonary nodules (SPN) that measure less than 3 cm in size are an increasingly common finding on computed tomography (CT) worldwide. Once identified there are a number of imaging strategies that can be performed to help with nodule characterization. These include interval CT, dynamic contrast enhanced computed tomography (DCE-CT), (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET-CT). To date the most cost effective and efficient non-invasive test or combination of tests for optimal nodule characterization has yet to be determined.DCE-CT is a functional test that involves the acquisition of a dynamic series of images of a nodule before and following the administration of intravenous iodinated contrast medium. This article provides an overview of the current indications and limitations of DCE- CT in nodule characterization and a systematic approach to how to perform, analyse and interpret a DCE-CT scan.

  9. Accurate diagnosis of axillary lymph node metastasis using contrast-enhanced ultrasonography with Sonazoid

    PubMed Central

    MATSUZAWA, FUMIHIKO; EINAMA, TAKAHIRO; ABE, HIRONORI; SUZUKI, TAKASHI; HAMAGUCHI, JUN; KAGA, TERUMI; SATO, MAMI; OOMURA, MASAKO; TAKATA, YUMIKO; FUJIBE, AYAKO; TAKEDA, CHIE; TAMURA, ETSUYA; TAKETOMI, AKINOBU; KYUNO, KENICHI

    2015-01-01

    Axillary lymph node enlargement following sentinel lymph node biopsy (SLNB) is often difficult to accurately diagnose. In keeping with the characteristically tortuous and aberrant pattern of tumor neovasculature, metastatic lymph nodes exhibit peripheral and mixed vascularity, resulting in a microvasculature that is often difficult to visualize. Contrast-enhanced ultrasonography (CEUS) with Sonazoid, a new generation contrast agent for ultrasonography, allows for the visualization of lymph node microvessels and may enable a more accurate evaluation of lymph node metastasis. This is a case report of axillary lymph node enlargement following SLNB, in which CEUS with Sonazoid resulted in an accurate diagnosis. On the basis of our experience with this case, we have initiated a clinical trial to evaluate the detection of lymph node metastasis through the use of CEUS in breast cancer patients. PMID:25798257

  10. Diagnosing Pancreatic Tumors Using Contrast-enhanced Harmonic Endoscopic Ultrasonography with Sonazoid.

    PubMed

    Yamamoto, Naoki; Kato, Hironari; Mizukawa, Sho; Muro, Shinichiro; Akimoto, Yutaka; Uchida, Daisuke; Tomoda, Takeshi; Matsumoto, Kazuyuki; Horiguchi, Shigeru; Tsutsumi, Koichiro; Okada, Hiroyuki

    2016-08-01

    Contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) with contrast agent enabled us to assess the hemodynamics closely, despite limited data in pancreatic tumors. We have initiated a prospective, single arm, and non-randomized study to clarify the accuracy and safety of CH-EUS with Sonazoid and time-intensity curve (TIC) analysis for diagnosing benign or malignant pancreatic tumors. A total of 200 patients will undergo CH-EUS and TIC analysis. Receiver operating characteristic (ROC) analysis will be used to determine the optimal parameter cutoff values for TIC analysis. This will clarify whether CH-EUS and TIC can further improve the diagnosis of pancreatic tumors over conventional EUS. PMID:27549682

  11. Power-constrained contrast enhancement algorithm using multiscale retinex for OLED display.

    PubMed

    Nam, Yeon-Oh; Choi, Dong-Yoon; Song, Byung Cheol

    2014-08-01

    This paper presents a power-constrained contrast enhancement algorithm for organic light-emitting diode display based on multiscale retinex (MSR). In general, MSR, which is the key component of the proposed algorithm, consists of power controllable log operation and subbandwise gain control. First, we decompose an input image to MSRs of different sub-bands, and compute a proper gain for each MSR. Second, we apply a coarse-to-fine power control mechanism, which recomputes the MSRs and gains. This step iterates until the target power saving is accurately accomplished. With video sequences, the contrast levels of adjacent images are determined consistently using temporal coherence in order to avoid flickering artifacts. Finally, we present several optimization skills for real-time processing. Experimental results show that the proposed algorithm provides better visual quality than previous methods, and a consistent power-saving ratio without flickering artifacts, even for video sequences.

  12. Controlled bacteria-gold nanorod interactions for enhancement of optoacoustic contrast

    NASA Astrophysics Data System (ADS)

    Liopo, Anton; Derry, Paul J.; Ermolinsky, Boris; Su, Richard; Conjusteau, André; Ermilov, Sergey; Zubarev, Eugene R.; Oraevsky, Alexander

    2014-03-01

    Gold-based contrast agents, gold nanorod (GNR), were designed for the enhancement of optoacoustic signal. After synthesis, the GNR-CTAB complexes were modified by pegylation (PEG), or replacement of CTAB (cetyl trimethylammonium bromide) with MTAB (16-mercaptohexadecyl trimethylammonium bromide) for coverage of gold nanorods with heparin (GNR-HP). Modified GNR are purified through centrifugation and filtration. GNRCTAB can be used as a model of positively charged gold surface for quantitative optoacoustic sensing in GNRbacteria interactions, whereas GNR-PEG and GNR-HP can be used as negatively charged gold surface models. We studied controlled agglomeration of contrast agents with the bacteria E.Coli and Vibrio Cholerae. For bacterial sensing, the localized plasmon resonance peak shifts as a function of electrostatic binding, which was detected with two different wavelengths through 3D optoacoustic imaging.

  13. Artery and vein separation using susceptibility-dependent phase in contrast-enhanced MRA.

    PubMed

    Wang, Y; Yu, Y; Li, D; Bae, K T; Brown, J J; Lin, W; Haacke, E M

    2000-11-01

    In magnetic resonance angiography, contrast agents are frequently used to help highlight arteries over background tissue. Unfortunately, enhancing veins hamper the visualization of arteries when data are collected over a long period of time after the arterial phase of the contrast agent. To overcome this problem, we have developed a novel imaging and postprocessing method that is capable of eliminating veins by utilizing the susceptibility difference between veins and surrounding tissue. This method was applied in the peripheral vasculature where the vessels are predominantly parallel to the main field and where the blood oxygen level-dependent effect is most pronounced. Results are presented for both long (15.8 msec) and short echo times (7.8 msec) and for sequential and centrally reordered acquisition schemes. The short echo scan approach appears to be the most promising, making it possible to obtain good suppression of the venous signal even when the timing is not perfect or when repeat scans are necessary.

  14. Contrast enhanced ultrasonography versus MR angiography in aortocaval fistula: case report.

    PubMed

    Bhatia, Mona; Platon, Alexandra; Khabiri, Ebrahim; Becker, Christoph; Poletti, Pierre-Alexandre

    2010-06-01

    Aortocaval fistula (ACF) is a rare, life threatening complication of abdominal aortic aneurysms. Time to diagnosis is crucial as preoperative diagnosis and early surgical intervention significantly improve the outcome. The clinical spectrum being varied, the challenge of prompt and reliable diagnosis rests on emergency radiology. While the gold standard for detecting ACF today is CT angiography (CTA), frequently complicating renal insufficiency discourages the use of iodinated contrast making MR angiography (MRA) a useful alternative. Contrast enhanced ultrasound (CEUS) provides a promising new diagnostic option allowing rapid, non invasive and bedside diagnosis, especially in hemodynamically unstable patients. We present a case of prompt diagnosis of ACF by CEUS in comparison to modern MRA, thus establishing the new potential role of CEUS.

  15. Dynamic contrast enhanced CT in nodule characterization: How we review and report.

    PubMed

    Qureshi, Nagmi R; Shah, Andrew; Eaton, Rosemary J; Miles, Ken; Gilbert, Fiona J

    2016-01-01

    Incidental indeterminate solitary pulmonary nodules (SPN) that measure less than 3 cm in size are an increasingly common finding on computed tomography (CT) worldwide. Once identified there are a number of imaging strategies that can be performed to help with nodule characterization. These include interval CT, dynamic contrast enhanced computed tomography (DCE-CT), (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET-CT). To date the most cost effective and efficient non-invasive test or combination of tests for optimal nodule characterization has yet to be determined.DCE-CT is a functional test that involves the acquisition of a dynamic series of images of a nodule before and following the administration of intravenous iodinated contrast medium. This article provides an overview of the current indications and limitations of DCE- CT in nodule characterization and a systematic approach to how to perform, analyse and interpret a DCE-CT scan. PMID:27430260

  16. Synchronous (Lock-in) Measurement Techniques for Magnetic Contrast Enhancement in STXM

    SciTech Connect

    Kaznatcheev, K.; Bertwistle, D.; Cheng, C.; Zohar, S.; Bailey, W. E.

    2011-09-09

    We have explored the capabilities of synchronous ('lock-in') point detection techniques to enhance the x-ray magnetic circular dichroism (XMCD) contrast in scanning x-ray transmission microscopy (STXM) of magnetic thin-film microstructures. Local absorption contrast, measured synchronously with low-amplitude (<10 Oe) and low-frequency (<200 hz) longitudinal fields perturbing the near-remanent magnetization state, reveal a strong spatial dependence of the response, with a roll-off in frequency response above 200 Hz. In this context, synchronous measurement affords us a basis for imaging the relation between energy loss and the sweeping rate. We speculate that the lock-in approach will be uniquely suited for detailing stochastic and deterministic frequency-dependent events in the process of magnetization reversal.

  17. Enhanced contrast and depth resolution in polarization imaging using elliptically polarized light

    NASA Astrophysics Data System (ADS)

    Sridhar, Susmita; Da Silva, Anabela

    2016-07-01

    Polarization gating is a popular and widely used technique in biomedical optics to sense superficial tissues (colinear detection), deeper volumes (crosslinear detection), and also selectively probe subsuperficial volumes (using elliptically polarized light). As opposed to the conventional linearly polarized illumination, we propose a new protocol of polarization gating that combines coelliptical and counter-elliptical measurements to selectively enhance the contrast of the images. This new method of eliminating multiple-scattered components from the images shows that it is possible to retrieve a greater signal and a better contrast for subsurface structures. In vivo experiments were performed on skin abnormalities of volunteers to confirm the results of the subtraction method and access subsurface information.

  18. Contrast-enhanced ultrasound after endovascular aortic repair—current status and future perspectives

    PubMed Central

    Partovi, Sasan; Kaspar, Mathias; Aschwanden, Markus; Lopresti, Charles; Madan, Shivanshu; Uthoff, Heiko; Imfeld, Stephan

    2015-01-01

    An increasing number of patients with abdominal aortic aneurysms (AAAs) are undergoing endovascular aortic repair (EVAR) instead of open surgery. These patients require lifelong surveillance, and the follow-up imaging modality of choice has been traditionally computed tomography angiography (CTA). Repetitive CTA imaging is associated with cumulative radiation exposure and requires the administration of multiple doses of nephrotoxic contrast agents. Contrast-enhanced ultrasound (CEUS) has emerged as an alternative strategy in the follow-up of patients with EVAR and demonstrates high sensitivity and specificity for detection of endoleaks. In fact, a series of studies have shown that CEUS is at least performing equal to computed tomography for the detection and classification of endoleaks. This article summarizes current evidence of CEUS after EVAR and demonstrates its usefulness via various patient cases. PMID:26673398

  19. Acceleration of conventional data acquisition in dynamic contrast enhancement: comparing keyhole approaches with compressive sensing.

    PubMed

    Geethanath, Sairam; Gulaka, Praveen K; Kodibagkar, Vikram D

    2014-01-01

    Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) has become a valuable clinical tool for cancer diagnosis and prognosis. DCE MRI provides pharmacokinetic parameters dependent on the extravasation of small molecular contrast agents, and thus high temporal resolution and/or spatial resolution is required for accurate estimation of parameters. In this article we investigate the efficacy of 2 undersampling approaches to speed up DCE MRI: a conventional keyhole approach and compressed sensing-based imaging. Data reconstructed from variants of these methods has been compared with the full k-space reconstruction with respect to data quality and pharmacokinetic parameters Ktrans and ve. Overall, compressive sensing provides better data quality and reproducible parametric maps than key-hole methods with higher acceleration factors. In particular, an undersampling mask based on a priori precontrast data showed high fidelity of reconstructed data and parametric maps up to 5× acceleration.

  20. Contrast enhancement in widefield CARS microscopy by tailored phase matching using a spatial light modulator.

    PubMed

    Jesacher, Alexander; Roider, Clemens; Khan, Saranjam; Thalhammer, Gregor; Bernet, Stefan; Ritsch-Marte, Monika

    2011-06-15

    We introduce a widefield CARS microscope implementation that uses a spatial light modulator to obtain extremely precise control over the pump/probe-beam incidence geometry, which provides the possibility to enhance the image contrast at specific target resonances by fine-tuning the incidence angles. We show how this technique can be used to optimize the image contrast between objects of different size and to practically eliminate the undesired signal from the solvent that embeds small target specimens. Changing the numerical aperture of the illumination from 1.27 to 1.24 improved the ratio of the signals of 500 nm polystyrene beads and the agarose solvent by about 20 dB. PMID:21685981

  1. 2-tier in-plane motion correction and out-of-plane motion filtering for contrast-enhanced ultrasound

    PubMed Central

    Ta, Casey N.; Eghtedari, Mohammad; Mattrey, Robert F.; Kono, Yuko; Kummel, Andrew C.

    2014-01-01

    Objectives Contrast-enhanced ultrasound (CEUS) cines of focal liver lesions (FLL) can be quantitatively analyzed to measure tumor perfusion on a pixel-by-pixel basis for diagnostic indication. However, CEUS cines acquired freehand and during free breathing cause non-uniform in-plane and out-of-plane motion from frame to frame. These motions create fluctuations in the time-intensity curves (TIC), reducing accuracy of quantitative measurements. Out-of-plane motion cannot be corrected by image registration in 2D CEUS and degrades the quality of in-plane motion correction (IPMC). A 2-tier IPMC strategy and adaptive out-of-plane motion filter (OPMF) are proposed to provide a stable correction of non-uniform motion to reduce the impact of motion on quantitative analyses. Materials and Methods 22 cines of FLLs were imaged with dual B-mode and contrast specific imaging to acquire a 3-minute TIC. B-mode images were analyzed for motion, and the motion correction was applied to both B-mode and contrast images. For IPMC, the main reference frame was automatically selected for each cine, and subreference frames were selected in each respiratory cycle and sequentially registered toward the main reference frame. All other frames were sequentially registered toward the local subreference frame. Four OPMFs were developed and tested: subsample Normalized Correlation (NC), subsample Sum of Absolute Differences (SAD), mean frame NC, and histogram. The frames that were most dissimilar to the OPMF reference frame using one of the four above criteria in each respiratory cycle were adaptively removed by thresholding against the low-pass filter of the similarity curve. OPMF was quantitatively evaluated by an out-of-plane motion metric (OPMM) that measured normalized variance in the high-pass filtered time-intensity curve within the tumor region-of-interest with low OPMM being the goal. IPMC and OPMF results were qualitatively evaluated by two blinded observers who ranked the motion in the

  2. Comparative evaluation of methylene blue and demeclocycline for enhancing optical contrast of brain neoplasms

    NASA Astrophysics Data System (ADS)

    Wirth, Dennis J.

    Brain tumors cause significant morbidity and mortality even when benign. Completeness of resection of brain tumors has been associated with better quality of life. However, that is often difficult to accomplish. The goal of this study was to evaluate the feasibility of using contrast enhanced multimodal confocal imaging for intraoperative detection of brain neoplasms. Different types of benign and malignant, primary and metastatic brain tumors, stained with Methylene Blue (MB) as a contrast agent, were imaged. MB is a traditional histopathologic stain that absorbs light in the red spectral range and fluoresces in the near infrared. It is FDA-approved for in vivo staining of human skin and breast tissue. Optical images showed good correlation with histopathology, demonstrating the potential of contrast enhanced multimodal confocal imaging for intraoperative detection of brain neoplasms ex vivo. However, the safety of MB for staining human brain in vivo is questionable. Demeclocycline (DMN), an antibiotic of the tetracycline family, has shown to be effective in differentiating normal from cancerous tissue in various organs. DMN is a fluorophore, which absorbs light in the violet spectral range and has a broad emission band covering green and yellow wavelengths. It is commonly used to treat infection and inflammatory disorders, and could provide a safer alternative to MB. To test this hypothesis, fresh excess human brain tissues were bisected and stained with aqueous solutions of either MB or DMN and then imaged. Reflectance and fluorescence images acquired from tissues stained with the two dyes were compared, and correlated with processed H&E histopathology. Comparison showed similar staining patterns and contrast of diagnostic features in glioblastomas, stained using either MB or DMN. The results show potential of both MB and DMN for the intraoperative detection of microscopic nests of brain neoplasms. Further studies will establish safety and efficacy of these

  3. Functional Contrast-Enhanced CT For Evaluation of Acute Ischemic Stroke Does Not Increase the Risk of Contrast-Induced Nephropathy

    PubMed Central

    Lima, F.O.; Lev, M.H.; Levy, R.A.; Silva, G.S.; Ebril, M.; de Camargo, É.C.; Pomerantz, S.; Singhal, A.B.; Greer, D.M.; Ay, H.; González, R. Gilberto; Koroshetz, W.J.; Smith, W.S.; Furie, K.L.

    2010-01-01

    BACKGROUND AND PURPOSE Concerns have recently grown regarding the safety of iodinated contrast agents used for CTA and CTP imaging. We tested whether the incidence of AN, defined by a ≥25% increase in the post–contrast scan creatinine level, was higher among patients with ischemic stroke who underwent a functional contrast-enhanced CT protocol compared with those who had no iodinated contrast administration. MATERIALS AND METHODS The contrast-exposed group consisted of 575 patients with acute ischemic stroke who underwent CTA (n = 313), CTA/CTP (n = 224), or CTA/CTP followed by conventional angiography (n = 38) within 24 hours of stroke onset and were consecutively enrolled in a prospective cohort study. The nonexposed group consisted of 343 patients with ischemic stroke, consecutively admitted to the same institution, who did not receive iodinated contrast material. Patients were stratified by baseline eGFR. In the primary analysis, the Fisher exact test was used to compare the incidence of AN between the contrast-exposed and the nonexposed patients at 24, 48, and 72 hours and on a cumulative basis. A secondary analysis compared the incidence of AN in patients who underwent conventional angiography following CTA/CTP versus patients who underwent CTA/CTP only. RESULTS The incidence of AN was 5% in the exposed and 10% in the nonexposed group (P = .003). Patients who underwent conventional angiography after contrast CT were at no greater risk of AN than patients who underwent CTA/CTP alone (26 patients, 5%; and 2 patients, 5%, respectively; P = .7). CONCLUSIONS Administration of a contrast-enhanced CT protocol involving CTA/CTP and conventional angiography in selected patients does not appear to increase the incidence of CIN. PMID:20044502

  4. Enhanced polyaromatic hydrocarbon degradation by adapted cultures of actinomycete strains.

    PubMed

    Bourguignon, Natalia; Isaac, Paula; Alvarez, Héctor; Amoroso, María J; Ferrero, Marcela A

    2014-12-01

    Fifteen actinomycete strains were evaluated for their potential use in removal of polycyclic aromatic hydrocarbons (PAH). Their capability to degrade of naphthalene, phenanthrene, and pyrene was tested in minimal medium (MM) and MM with glucose as another substrate. Degradation of naphthalene in MM was observed in all isolates at different rates, reaching maximum values near to 76% in some strains of Streptomyces, Rhodococcus sp. 016 and Amycolatopsis tucumanensis DSM 45259. Maximum values of degradation of phenanthrene in MM occurred in cultures of A. tucumanensis DSM 45259 (36.2%) and Streptomyces sp. A12 (20%), while the degradation of pyrene in MM was poor and only significant with Streptomyces sp. A12 (4.3%). Because of the poor performance when growing on phenanthrene and pyrene alone, Rhodococcus sp. 20, Rhodococcus sp. 016, A. tucumanensis DSM 45259, Streptomyces sp. A2, and Streptomyces sp. A12 were challenged to an adaptation schedule of successive cultures on a fresh solid medium supplemented with PAHs, decreasing concentration of glucose in each step. As a result, an enhanced degradation of PAHs by adapted strains was observed in the presence of glucose as co-substrate, without degradation of phenanthrene and pyrene in MM while an increase to up to 50% of degradation was seen with these strains in glucose amended media. An internal fragment of the catA gene, which codes for catechol 1,2-dioxygenase, was amplified from both Rhodococcus strains, showing the potential for degradation of aromatic compounds via salycilate. These results allow us to propose the usefulness of these actinomycete strains for PAH bioremediation in the environment. PMID:25205070

  5. Standardization of radiological evaluation of dynamic contrast enhanced MRI: application in breast cancer diagnosis.

    PubMed

    Furman-Haran, E; Feinberg, M Shapiro; Badikhi, D; Eyal, E; Zehavi, T; Degani, H

    2014-10-01

    Dynamic contrast enhanced MRI is applied as an adjuvant tool for breast cancer detection, diagnosis, and follow-up of therapy. Despite improvements through the years in achieving higher spatial and temporal resolution, it still suffers from lack of scanning and processing standardization, and consequently, high variability in the radiological evaluation, particularly differentiating malignant from benign lesions. We describe here a hybrid method for achieving standardization of the radiological evaluation of breast dynamic contrast enhanced (DCE)-magnetic resonance imaging (MRI) protocols, based on integrating the model based three time point (3TP) method with principal component analysis (PCA). The scanning and image processing procedures consisted of three main steps: 1. 3TP standardization of the MRI acquisition parameters according to a kinetic model, 2. Applying PCA to test cases and constructing an eigenvectors' base related to the contrast-enhancement kinetics and 3. Projecting all new cases on the eigenvectors' base and evaluating the clinical outcome. Datasets of overall 96 malignant and 26 benign breast lesions were recorded on 1.5T and 3T scanners, using three different MRI acquisition parameters optimized by the 3TP method. The final radiological evaluation showed similar detection and diagnostic ability for the three different MRI acquisition parameters. The area under the curve of receiver operating characteristic analysis yielded a value of 0.88 ± 0.034 for differentiating malignant from benign lesions. This 3TP+PCA hybrid method is fast and can be readily applied as a computer aided diagnostic tool of breast cancer. The underlying principles of this method can be extended to standardize the evaluation of malignancies in other organs.

  6. Scanning Tunneling Microscopy: Development ofTips for Contrast Enhanced Imaging and Imaging of Mixed Monolayers

    NASA Astrophysics Data System (ADS)

    Gingery, David Patrick

    Scanning Tunneling Microscopy (STM) is a powerful tool for surface analysis which provides atomic resolution of samples. Of particular interest is the adsorption behavior of alkane and alkane derivatives on graphite substrates. Such studies are limited by the lack of chemical information provided by STM. Chemically Selective STM, wherein STM tips are chemically modified in order to provide enhanced contrast of chemicals on a surface is a solution to this limitation. While extremely promising this method has several limitations barring it from wider application. These limitations include the low population of modified tips that provide contrast enhancement and limited useful tip lifetime. Chapter 1 presents a general introduction to the materials and methods employed in this work. In Chapter 2 growth of carbon nanotubes (CNTs) on STM tips is explored as a new route to chemically modified STM tips. Growth of CNTs on tungsten followed by electrodeposition of ruthenium oxide to create a conductive path led to a working CNT STM tip. Chapter 3 presents a study of gold nanoparticle deposition on carbon nanotubes by thermal evaporation. Nanoparticles supported on CNTs are of interest in various area of study including catalysis and electrochemistry. It is demonstrated that evaporation is an effective route to CNT supported gold nanoparticles. Chapter 4 focuses on development of a new single-step electrochemical etching method for producing gold STM tips. Sharp gold STM tips are critical for chemically selective STM performed with self-assembled monolayer (SAM) modified tips. It is demonstrated that electrochemical etching in low concentrations of perchloric acid in aqueous sodium chloride solutions produces high quality tips. Chapter 5 discusses an in-situ voltage pulse treatment for inducing chemical contrast enhancement in STM images. This method, applied for the first time to a hydrogen bond donor, allows chemical contrast enhancement in STM images to be switched on or

  7. Protocol using elliptically polarized light for enhanced contrast in polarization gating imaging of biological tissues

    NASA Astrophysics Data System (ADS)

    Sridhar, Susmita; Da Silva, Anabela

    2016-03-01

    Polarization gating is a popular and widely used technique in biomedical optics to sense superficial tissues (collinear detection), deeper volumes (cross-linear detection), and also selectively probe deeper volumes (using elliptically polarized light). As opposed to the conventional linearly polarized illumination, we propose a new protocol of polarization gating that combines co-elliptical and counter-elliptical measurements to selectively enhance contrast of the images. In vivo experiments were performed on skin abnormalities of volunteers (to selectively probe and access subsurface information).

  8. Water-dispersible ascorbic-acid-coated magnetite nanoparticles for contrast enhancement in MRI

    NASA Astrophysics Data System (ADS)

    Sreeja, V.; Jayaprabha, K. N.; Joy, P. A.

    2015-04-01

    Superparamagnetic iron oxide nanoparticles of size ~5 nm surface functionalized with ascorbic acid (vitamin C) form a stable dispersion in water with a hydrodynamic size of ~30 nm. The anti-oxidant property of ascorbic acid is retained after capping, as evidenced from the capability of converting methylene blue to its reduced leuco form. NMR relaxivity studies show that the ascorbic-acid-coated superparamagnetic iron oxide aqueous nanofluid is suitable as a contrast enhancement agent for MRI applications, coupled with the excellent biocompatibility and medicinal values of ascorbic acid.

  9. Three-Dimensional Characterization of Tissue-Engineered Constructs by Contrast-Enhanced Nanofocus Computed Tomography

    PubMed Central

    Papantoniou, Ioannis; Sonnaert, Maarten; Geris, Liesbet; Luyten, Frank P.; Kerckhofs, Greet

    2014-01-01

    To successfully implement tissue-engineered (TE) constructs as part of a clinical therapy, it is necessary to develop quality control tools that will ensure accurate and consistent TE construct release specifications. Hence, advanced methods to monitor TE construct properties need to be further developed. In this study, we showed proof of concept for contrast-enhanced nanofocus computed tomography (CE-nano-CT) as a whole-construct imaging technique with a noninvasive potential that enables three-dimensional (3D) visualization and quantification of in vitro engineered extracellular matrix (ECM) in TE constructs. In particular, we performed a 3D qualitative and quantitative structural and spatial assessment of the in vitro engineered ECM, formed during static and perfusion bioreactor cell culture in 3D TE scaffolds, using two contrast agents, namely, Hexabrix® and phosphotungstic acid (PTA). To evaluate the potential of CE-nano-CT, a comparison was made to standardly used techniques such as Live/Dead viability/cytotoxicity, Picrosirius Red staining, and to net dry weight measurements of the TE constructs. When using Hexabrix as the contrast agent, the ECM volume fitted linearly with the net dry ECM weight independent from the flow rate used, thus suggesting that it stains most of the ECM. When using PTA as the contrast agent, comparing to net weight measurements showed that PTA only stains a part of the ECM. This was attributed to the binding specificity of this contrast agent. In addition, the PTA-stained CE-nano-CT data showed pronounced distinction between flow conditions when compared to Hexabrix, indicating culture-specific structural ECM differences. This novel type of information can contribute to optimize bioreactor culture conditions and potentially critical quality characteristics of TE constructs such as ECM quantity and homogeneity, facilitating the gradual transformation of TE constructs in well-characterized TE products. PMID:23800097

  10. Enhancement of gamma oscillations indicates preferential processing of native over foreign phonemic contrasts in infants.

    PubMed

    Ortiz-Mantilla, Silvia; Hämäläinen, Jarmo A; Musacchia, Gabriella; Benasich, April A

    2013-11-27

    Young infants discriminate phonetically relevant speech contrasts in a universal manner, that is, similarly across languages. This ability fades by 12 months of age as the brain builds language-specific phonemic maps and increasingly responds preferentially to the infant's native language. However, the neural mechanisms that underlie the development of infant preference for native over non-native phonemes remain unclear. Since gamma-band power is known to signal infants' preference for native language rhythm, we hypothesized that it might also indicate preference for native phonemes. Using high-density electroencephalogram/event-related potential (EEG/ERP) recordings and source-localization techniques to identify and locate the ERP generators, we examined changes in brain oscillations while 6-month-old human infants from monolingual English settings listened to English and Spanish syllable contrasts. Neural dynamics were investigated via single-trial analysis of the temporal-spectral composition of brain responses at source level. Increases in 4-6 Hz (theta) power and in phase synchronization at 2-4 Hz (delta/theta) were found to characterize infants' evoked responses to discrimination of native/non-native syllable contrasts mostly in the left auditory source. However, selective enhancement of induced gamma oscillations in the area of anterior cingulate cortex was seen only during native contrast discrimination. These results suggest that gamma oscillations support syllable discrimination in the earliest stages of language acquisition, particularly during the period in which infants begin to develop preferential processing for linguistically relevant phonemic features in their environment. Our results also suggest that by 6 months of age, infants already treat native phonemic contrasts differently from non-native, implying that perceptual specialization and establishment of enduring phonemic memory representations have been initiated.

  11. Tryptophan PET predicts spatial and temporal patterns of post-treatment glioblastoma progression detected by contrast-enhanced MRI.

    PubMed

    Bosnyák, Edit; Kamson, David O; Robinette, Natasha L; Barger, Geoffrey R; Mittal, Sandeep; Juhász, Csaba

    2016-01-01

    Amino acid PET is increasingly utilized for the detection of recurrent gliomas. Increased amino acid uptake is often observed outside the contrast-enhancing brain tumor mass. In this study, we evaluated if non-enhancing PET+ regions could predict spatial and temporal patterns of subsequent MRI progression in previously treated glioblastomas. Twelve patients with a contrast-enhancing area suspicious for glioblastoma recurrence on MRI underwent PET scanning with the amino acid radiotracer alpha-[(11)C]-methyl-L-tryptophan (AMT). Brain regions showing increased AMT uptake in and outside the contrast-enhancing volume were objectively delineated to include high uptake consistent with glioma (as defined by previous studies). Volume and tracer uptake of such non-enhancing PET+ regions were compared to spatial patterns and timing of subsequent progression of the contrast-enhancing lesion, as defined by serial surveillance MRI. Non-enhancing PET+ volumes varied widely across patients and extended up to 24 mm from the edge of MRI contrast enhancement. In ten patients with clear progression of the contrast-enhancing lesion, the non-enhancing PET+ volumes predicted the location of new enhancement, which extended beyond the PET+ brain tissue in six. In two patients, with no PET+ area beyond the initial contrast enhancement, MRI remained stable. There was a negative correlation between AMT uptake in non-enhancing brain and time to subsequent progression (r = -0.77, p = 0.003). Amino acid PET imaging could complement MRI not only for detecting glioma recurrence but also predicting the location and timing of subsequent tumor progression. This could support decisions for surgical intervention or other targeted therapies for recurrent gliomas.

  12. Assessment of brain perfusion using parametric and factor images extracted from dynamic contrast-enhanced MRI images

    NASA Astrophysics Data System (ADS)

    Martel, Anne L.; Moody, Alan R.

    1998-07-01

    Contrast-enhanced magnetic resonance (MR) imaging offers a minimally invasive method of investigating brain blood flow. This paper describes two different methods of extracting quantitative and qualitative information from this data. The first approach is to generate parametric images showing blood flow, blood volume and time-to-peak activity on a pixel by pixel basis. The second approach uses factor analysis. Principal components are extracted from the data and these orthogonal factors are then rotated to give a set of oblique factors, which satisfy certain simple constraints. In most cases three factors can be identified: a background or non- enhancing factor, an early vascular factor which is strongly correlated to arterial flow, and a late vascular factor which is strongly correlated to venous flow. The parametric and factor images are complimentary in nature: the former provides quantitative information that is readily understood by the clinician, while the latter makes no a priori assumptions about the underlying physiology and also allows more subtle changes in cerebral blood flow to be assessed. The factor images may also be of great value in defining regions of interest over which to carry out a more detailed quantitative analysis. This dual approach can be readily adapted to assess perfusion in other organs such as the heart or kidneys.

  13. Importance of Contrast-Enhanced Fluid-Attenuated Inversion Recovery Magnetic Resonance Imaging in Various Intracranial Pathologic Conditions

    PubMed Central

    Lee, Eun Kyoung; Kim, Sungwon; Lee, Yong Seok

    2016-01-01

    Intracranial lesions may show contrast enhancement through various mechanisms that are closely associated with the disease process. The preferred magnetic resonance sequence in contrast imaging is T1-weighted imaging (T1WI) at most institutions. However, lesion enhancement is occasionally inconspicuous on T1WI. Although fluid-attenuated inversion recovery (FLAIR) sequences are commonly considered as T2-weighted imaging with dark cerebrospinal fluid, they also show mild T1-weighted contrast, which is responsible for the contrast enhancement. For several years, FLAIR imaging has been successfully incorporated as a routine sequence at our institution for contrast-enhanced (CE) brain imaging in detecting various intracranial diseases. In this pictorial essay, we describe and illustrate the diagnostic importance of CE-FLAIR imaging in various intracranial pathologic conditions. PMID:26798225

  14. Straight Vessel Pattern and Rapid Filling Time: Characteristic Findings on Contrast-Enhanced Sonography of Testicular Lymphoma.

    PubMed

    Lock, Guntram; Schmidt, Christa; Schröder, Claudia; Löning, Thomas; Dieckmann, Klaus-Peter

    2016-07-01

    Six patients with 7 lesions that were histologically confirmed as primary testicular lymphoma were preoperatively investigated with a standardized sonographic protocol including contrast-enhanced sonography. Duplex and contrast-enhanced sonography showed marked hypervascularization in all 7 lesions. On contrast-enhanced sonography, the filling time of lymphomatous lesions was significantly shorter than the filling time of a size-matched sample of 10 patients with seminomas (P < .0001). The sonographic hallmarks of testicular lymphoma in our case series were as follows: (1) sharply demarcated homogeneous hypoechoic testicular lesions with marked hypervascularization; (2) a rapid (<7 seconds) filling time of contrast bubbles; and (3) a straight and parallel course of intralesional vessels on contrast-enhanced sonography. PMID:27335443

  15. Topological study of nanomaterials using surface-enhanced ellipsometric contrast microscopy (SEEC)

    NASA Astrophysics Data System (ADS)

    Muckenhirn, Sylvain

    2016-03-01

    Innovations in nanotechnology are empowering scientists to deepen their understanding of physical, chemical and biological mechanisms. Powerful and precise characterization systems are essential to meet researchers' requirements. SEEC (Surface Enhanced Ellipsometric Contrast) microscopy is an innovative advanced optical technique based on ellipsometric and interference fringes of Fizeau principles. This technique offers live and label-free topographic imaging of organic, inorganic and biological samples with high Z resolution (down to 0.1nm thickness), and enhanced X-Y detection limit (down to 1.5nm width). This technique has been successfully applied to the study of nanometric films and structures, biological layers, and nano-objects. We applied SEEC technology to different applications explored below.

  16. Real-time contrast-enhanced holographic imaging using phase coherent photorefractive quantum wells.

    PubMed

    Dongol, A; Thompson, J; Schmitzer, H; Tierney, D; Wagner, H P

    2015-05-18

    We demonstrate wide-field real-time and depth-resolved contrast enhanced holographic imaging (CEHI) using the all-optical phase coherent photorefractive effect in ZnSe quantum wells. Moving objects are imaged at large depth-of-field by the local enhancement of a static reference hologram. The high refresh rate of the holographic films enables direct-to-video monitoring of floating glass beads and of living Paramecium and Euglena cells moving in water. Depth resolution is achieved by tilting the incident laser beam with respect to the normal of the cuvette. This creates double images of the objects, which are analyzed geometrically and with Fresnel diffraction theory. A two-color CEHI set-up further enables the visualization of a concealed 95 µm thick wire behind a thin layer of chicken skin. PMID:26074534

  17. Real-time contrast-enhanced holographic imaging using phase coherent photorefractive quantum wells.

    PubMed

    Dongol, A; Thompson, J; Schmitzer, H; Tierney, D; Wagner, H P

    2015-05-18

    We demonstrate wide-field real-time and depth-resolved contrast enhanced holographic imaging (CEHI) using the all-optical phase coherent photorefractive effect in ZnSe quantum wells. Moving objects are imaged at large depth-of-field by the local enhancement of a static reference hologram. The high refresh rate of the holographic films enables direct-to-video monitoring of floating glass beads and of living Paramecium and Euglena cells moving in water. Depth resolution is achieved by tilting the incident laser beam with respect to the normal of the cuvette. This creates double images of the objects, which are analyzed geometrically and with Fresnel diffraction theory. A two-color CEHI set-up further enables the visualization of a concealed 95 µm thick wire behind a thin layer of chicken skin.

  18. Tibetan and Andean contrasts in adaptation to high-altitude hypoxia.

    PubMed

    Beall, C M

    2000-01-01

    High-altitude environments provide natural experimental settings to investigate adaptation to environmental stress. An important evolutionary and functional question is whether sea-level human biology constrains the adaptive response. This paper presents evidence that indigenous populations of the Tibetan and Andean plateaus exhibit quantitatively different responses to hypobaric hypoxic stress. At the same altitude, Tibetan mean resting ventilation and hypoxic ventilatory response were more than one-half standard deviation higher than Andean Aymara means while Tibetan mean oxygen saturation and hemoglobin concentration were more than one standard deviation below the Andean means. Quantitative genetic analyses of the familial patterning of these traits provided indirect evidence of population differences in genes influencing them. The Tibetan and Andean patterns of oxygen transport appear equally effective functionally as evaluated by birthweight and maximal aerobic capacity across a range of altitudes.

  19. Adaptive k-space sampling design for edge-enhanced DCE-MRI using compressed sensing.

    PubMed

    Raja, Rajikha; Sinha, Neelam

    2014-09-01

    The critical challenge in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is the trade-off between spatial and temporal resolution due to the limited availability of acquisition time. To address this, it is imperative to under-sample k-space and to develop specific reconstruction techniques. Our proposed method reconstructs high-quality images from under-sampled dynamic k-space data by proposing two main improvements; i) design of an adaptive k-space sampling lattice and ii) edge-enhanced reconstruction technique. A high-resolution data set obtained before the start of the dynamic phase is utilized. The sampling pattern is designed to adapt to the nature of k-space energy distribution obtained from the static high-resolution data. For image reconstruction, the well-known compressed sensing-based total variation (TV) minimization constrained reconstruction scheme is utilized by incorporating the gradient information obtained from the static high-resolution data. The proposed method is tested on seven real dynamic time series consisting of 2 breast data sets and 5 abdomen data sets spanning 1196 images in all. For data availability of only 10%, performance improvement is seen across various quality metrics. Average improvements in Universal Image Quality Index and Structural Similarity Index Metric of up to 28% and 24% on breast data and about 17% and 9% on abdomen data, respectively, are obtained for the proposed method as against the baseline TV reconstruction with variable density random sampling pattern.

  20. Contrast-enhanced ultrasound for diagnosing, staging and assessment of operability of pancreatic cancer.

    PubMed

    Grossjohann, Hanne Sønder

    2012-12-01

    We have evaluated the usefulness of contrast-enhanced ultrasound (CEUS) for diagnosing, staging and assessment of operability of pancreatic head tumors. For some years CEUS has been used with great success for diagnosis of focal liver lesions but when we started our trial, it was still relatively untested in the pancreas. This PhD thesis is based on a methodological study, two clinical studies and an intra-/interobserver study. The methodological study consists of material collected from investigations made on 14 experimental pigs. First, we examined the pig pancreas with CEUS. Hereafter we repeated the CEUS examination after venous injection of the gastrointestinal hormones secretin and cholecystokinin. We investigated if the contrast-enhancement would intensify after hormone stimulation. The clinical studies consist of material collected from examinations of 49 patients referred to our hospital with the diagnosis, suspicion of pancreatic cancer. All patients had a conventional ultrasound examination and a CEUS examination. In addition, some of the patients also had a CEUS examination after stimulation with secretin and cholecystokinin. All patients had a 64-slice-CT examination and a biopsy was taken for histopathological verification. We studied whether CEUS was useful for assessment of tumor classification, tumor staging and tumor resectability. We also tested if hormone stimulation of the pancreas during CEUS could intensify contrast-enhancement of healthy pancreatic tissue and thus contribute to a better demarcation of a tumor. Finally, we tested the intra-/interobserver agreement of our visual interpretation of the contrast-enhanced ultrasound images and the concordance between the visual interpretation and histopathological test results. From the results of the methodological study it seemed possible to intensify contrast-enhancement using the gastrointestinal hormones by 3%. During the clinical studies it emerged that hormone stimulation did not improve

  1. Bipolar radiofrequency ablation for liver tumors: comparison of contrast-enhanced ultrasound with contrast-enhanced MRI/CT in the posttreatment imaging evaluation

    PubMed Central

    Bo, Xiao-Wan; Xu, Hui-Xiong; Sun, Li-Ping; Zheng, Shu-Guang; Guo, Le-Hang; Lu, Feng; Wu, Jian; Xu, Xiao-Hong

    2014-01-01

    Objective: The aim of the study was to assess the role of contrast-enhanced ultrasound (CEUS) in treatment response evaluation after percutaneous bipolar radiofrequency ablation (BRFA) for liver tumors. Methods: From May 2012 to May 2014, 39 patients with 73 tumors were treated by BRFA. One month after the treatment, CEUS and CEMRI/CECT were conducted to evaluate the treatment response. The results of CEUS were compared with CEMRI/CECT. Results: Of the 73 tumors ablated, eight (11.0%) were found to have residual viable tumor tissue and 65 (89.0%) were successfully ablated based on CEMRI/CECT within 1-month after ablation. CEUS detected seven of the eight residual tumors and 63 of 65 completely ablated tumors. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of CEUS were 87.5% (7/8), 96.9% (63/65), 77.8% (7/9), 98.4% (63/64) and 95.9% (70/73), respectively. The complete ablation (CR) rates for the tumors ≤3.0 cm, 3.1-5.0 cm, and >5.0 cm were 96.6% (58/60), 63.6% (7/11), and 0% (0/2), respectively (P<0.001). CR rates were 94.7% (36/38) for primary liver tumors and 82.9% (29/35) for metastatic liver tumors (P=0.212), and were 97.4% (38/39) for the tumors with curative treatment intention and 79.4% (27/34) for those with palliative treatment intention (P=0.037). Major complication was not encountered in this series. Conclusions: BRFA is an effective technique of percutaneous ablation for liver tumors and CEUS can be used to assess its therapeutic effect accurately. PMID:25337258

  2. Night vision in barn owls: visual acuity and contrast sensitivity under dark adaptation.

    PubMed

    Orlowski, Julius; Harmening, Wolf; Wagner, Hermann

    2012-12-06

    Barn owls are effective nocturnal predators. We tested their visual performance at low light levels and determined visual acuity and contrast sensitivity of three barn owls by their behavior at stimulus luminances ranging from photopic to fully scotopic levels (23.5 to 1.5 × 10⁻⁶). Contrast sensitivity and visual acuity decreased only slightly from photopic to scotopic conditions. Peak grating acuity was at mesopic (4 × 10⁻² cd/m²) conditions. Barn owls retained a quarter of their maximal acuity when luminance decreased by 5.5 log units. We argue that the visual system of barn owls is designed to yield as much visual acuity under low light conditions as possible, thereby sacrificing resolution at photopic conditions.

  3. Individually optimized uniform contrast enhancement in CT angiography for the diagnosis of pulmonary thromboembolic disease—A simulation study

    SciTech Connect

    Xue, Ming; Zhang, Hao; D’Souza, Warren; Lu, Wei; Kligerman, Seth; Klahr, Paul

    2013-12-15

    Purpose: To improve the diagnostic quality of CT pulmonary angiography (CTPA) by individually optimizing a biphasic contrast injection function to achieve targeted uniform contrast enhancement. To compare the results against a previously reported discrete Fourier transform (DFT) approach. Methods: This simulation study used the CTPA datasets of 27 consecutive patients with pulmonary thromboembolic disease (PE). An optimization approach was developed consisting of (1) computation of the impulse enhancement function (IEF) based on a test bolus scan, and (2) optimization of a biphasic contrast injection function using the IEF in order to achieve targeted uniform enhancement. The injection rates and durations of a biphasic contrast injection function are optimized by minimizing the difference between the resulting contrast enhancement curve and the targeted uniform enhancement curve, while conforming to the clinical constraints of injection rate and total contrast volume. The total contrast volume was limited first to the clinical standard of 65 ml, and then to the same amount used in the DFT approach for comparison. The optimization approach and the DFT approach were compared in terms of the root mean square error (RMSE) and total contrast volume used. Results: When the total contrast volume was limited to 65 ml, the optimization approach produced significantly better contrast enhancement (closer to the targeted uniform contrast enhancement) than the DFT approach (RMSE 17 HU vs 56 HU,p < 0.00001). On average, the optimization approach used 63 ml contrast, while the DFT approach used 50 ml with four patients exceeding 65 ml. When equivalent total contrast volume was used for individual patient, the optimization approach still generated significantly better contrast enhancement (RMSE 44 HU vs 56 HU, p < 0.01). Constraints for the injection function could be easily accommodated into the optimization process when searching for the optimal biphasic injection function

  4. Contrast-Enhanced Ultrasonography with Quantitative Analysis allows Differentiation of Renal Tumor Histotypes

    PubMed Central

    Sun, Di; Wei, Cong; Li, Yi; Lu, Qijie; Zhang, Wei; Hu, Bing

    2016-01-01

    Totally 85 patients with 93 renal lesions who underwent contrast-enhanced ultrasound (CEUS) were retrospectively studied with quantitative analysis to evaluate its value in the differential diagnosis of renal tumor histotypes. CEUS characteristics were analysed including the enhancement patterns, peak intensity, homogeneity of enhancement, and pseudocapsule. Quantitative parameters of peak intensity (P) and time to peak (TP) were measured with QontraXt software, and the index “relative enhancement percentage” ΔP% and “difference in TP between tumor and cortex” ΔTP were used to quantify the CEUS features of renal tumors. There are significant difference in CEUS features between the 46 clear cell renal cell carcinoma (CCRCC) and other types of renal tumors, including 17 low malignant lesions, 11 urothelial carcinoma of the renal pelvis, and 19 renal angiomyolipoma. The differences lie in the peak intensity, the homogeneity, the time of wash-in, peak, clearance and presence of pseudocapsule. The ΔTP and ΔP% of the CCRCC is significantly different from other tumors. With “fast to peak + high peak intensity” as the main criterion, assisted with “heterogeneous enhancement” and “fast wash-in” as the secondary criteria, the diagnostic accuracy of CCRCC is 91.4%, demonstrating quantitative CEUS imaging is highly valuable in differentiating CCRCC from other tumors. PMID:27725761

  5. Parameters of prostate cancer at contrast-enhanced ultrasound: correlation with prostate cancer risk

    PubMed Central

    Xu, Guang; Wu, Jian; Yao, Ming-Hua; Yao, Xu-Dong; Peng, Bo; Wei, Qing; Xu, Hui-Xiong; Wu, Rong

    2015-01-01

    Objective: to investigate the correlation between the parameters of prostate cancer (PCa) at contrast-enhanced ultrasound (CEUS) with PCa risk. Methods: 84 patients (68 ± 8 years; range, 33-79 years) who had undergone CEUS were included. All the images were offline analyzed. Parameters (maximum intensity (IMAX), rise time (RT), time to peak (TTP) and mean transit time (mTT)) were recorded and compared with PSA level, Gleason score, clinical stages and PCa risk. Results: Age was correlated significantly with PCa risk. RT and mTT of outer gland were associated with PCa risk. No significant correlation was found between PSA and CEUS enhancement parameters. Furthermore, with the exception of IMAX of inner gland and IMAX of outer gland, there were no significant differences of enhancement parameters in Gleason score groups and clinical stages groups. Conclusion: The enhancement parameters of PCa at CEUS may be used to predict PCa risk. And it is helpful for the choice of therapeutic options. PMID:25932202

  6. Does contrast-enhanced ultrasound reveal tumor angiogenesis in pancreatic ductal carcinoma? A prospective study.

    PubMed

    Nishida, Mutsumi; Koito, Kazumitsu; Hirokawa, Naoki; Hori, Masakazu; Satoh, Taishi; Hareyama, Masato

    2009-02-01

    The purpose of this study is to evaluate tumor vascularity of pancreatic carcinoma noninvasively by contrast-enhanced ultrasound (US) and clarify the diagnostic value of tumor vascularity in subjects with nonresectable advanced pancreatic carcinoma. The study was approved by our institutional review board and written informed consent was obtained from all subjects. Twenty-seven subjects with advanced pancreatic ductal carcinoma were treated by chemoradiotherapy. Contrast-enhanced US, US guided biopsies and dynamic computed tomography (CT) were performed before and after the therapy. We assigned the intratumoral enhancement pattern of US as an enhanced ultrasound (EU) score, from 1 to 4, according to the degree of enhancement area. Intratumoral microvessel density (IMD) and average vessel diameter (AVD) were calculated by means of CD 34 immunostaining. Vascular endothelial growth factor (VEGF) staining was graded on a scale of 1 to 3. EU scores before chemoradiotherapy were compared with IMD, AVD, VEGF, histological grading and hepatic metastasis. After the therapy, local treatment response was evaluated by dynamic CT calculating the maximum area of the tumor, by comparing it with its size in pre- therapy. Subjects who had at least a 50% or more decrease of tumor size lasting more than 4 wk were estimated as partial response (PR), more than a 50% of increase progressive disease (PD) and if neither PR nor PD criteria were met, they were classified as stabled disease (SD). Next, EU scores were compared with IMD, AVD, VEGF and treatment response. Statistically significant differences were evaluated by Pearson's correlation, post-hoc, Spearman's rank correlation, Wilcoxon rank sum and Student's t-test. A p < 0.05 was defined as being statistically significant. Before the therapy, the EU score and IMD were significantly correlated (r = 0.50, p < 0.02), as was VEGF (r = 0.45, p < 0.05). The EU score and AVD were negatively correlated (r = - 0.56, p < 0.02). Significant

  7. Si-strip photon counting detectors for contrast-enhanced spectral mammography

    NASA Astrophysics Data System (ADS)

    Chen, Buxin; Reiser, Ingrid; Wessel, Jan C.; Malakhov, Nail; Wawrzyniak, Gregor; Hartsough, Neal E.; Gandhi, Thulasi; Chen, Chin-Tu; Iwanczyk, Jan S.; Barber, William C.

    2015-08-01

    We report on the development of silicon strip detectors for energy-resolved clinical mammography. Typically, X-ray integrating detectors based on scintillating cesium iodide CsI(Tl) or amorphous selenium (a-Se) are used in most commercial systems. Recently, mammography instrumentation has been introduced based on photon counting Si strip detectors. The required performance for mammography in terms of the output count rate, spatial resolution, and dynamic range must be obtained with sufficient field of view for the application, thus requiring the tiling of pixel arrays and particular scanning techniques. Room temperature Si strip detector, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel, provided that the sensors are designed for rapid signal formation across the X-ray energy ranges of the application. We present our methods and results from the optimization of Si-strip detectors for contrast enhanced spectral mammography. We describe the method being developed for quantifying iodine contrast using the energy-resolved detector with fixed thresholds. We demonstrate the feasibility of the method by scanning an iodine phantom with clinically relevant contrast levels.

  8. Dynamic contrast-enhanced optical imaging of in vivo organ function

    NASA Astrophysics Data System (ADS)

    Amoozegar, Cyrus B.; Wang, Tracy; Bouchard, Matthew B.; McCaslin, Addason F. H.; Blaner, William S.; Levenson, Richard M.; Hillman, Elizabeth M. C.

    2012-09-01

    Conventional approaches to optical small animal molecular imaging suffer from poor resolution, limited sensitivity, and unreliable quantitation, often reducing their utility in practice. We previously demonstrated that the in vivo dynamics of an injected contrast agent could be exploited to provide high-contrast anatomical registration, owing to the temporal differences in each organ's response to the circulating fluorophore. This study extends this approach to explore whether dynamic contrast-enhanced optical imaging (DyCE) can allow noninvasive, in vivo assessment of organ function by quantifying the differing cellular uptake or wash-out dynamics of an agent in healthy and damaged organs. Specifically, we used DyCE to visualize and measure the organ-specific uptake dynamics of indocyanine green before and after induction of transient liver damage. DyCE imaging was performed longitudinally over nine days, and blood samples collected at each imaging session were analyzed for alanine aminotransferase (ALT), a liver enzyme assessed clinically as a measure of liver damage. We show that changes in DyCE-derived dynamics of liver and kidney dye uptake caused by liver damage correlate linearly with ALT concentrations, with an r2 value of 0.91. Our results demonstrate that DyCE can provide quantitative, in vivo, longitudinal measures of organ function with inexpensive and simple data acquisition.

  9. Cranial CT in acquired immunodeficiency syndrome: spectrum of diseases and optimal contrast enhancement technique.

    PubMed

    Post, M J; Kursunoglu, S J; Hensley, G T; Chan, J C; Moskowitz, L B; Hoffman, T A

    1985-11-01

    A retrospective review of cranial CT scans obtained over a 4 year period in patients with acquired immunodeficiency syndrome (AIDS) and documented central nervous system (CNS) pathology is presented. The spectrum of diseases and the value of CT in detecting new, recurrent, and superimposed disease processes were determined. Fifty-one AIDS patients with confirmed CNS pathology were identified. Six of them had two coexistent diseases. Opportunistic infections predominated, especially Toxoplasma encephalitis and cryptococcal meningitis, while tumor was seen infrequently. Initial CT was positive in 76% of cases. In contrast to meningeal processes, where it was not very effective, CT was very sensitive in detecting most parenchymal disease processes. Characteristic although not pathognomonic CT patterns were found for certain diseases. Improvement or resolution of CT abnormalities in patients on medical therapy for Toxoplasma encephalitis correlated well with clinical improvement. Recurrence of CT abnormalities correlated well with medical noncompliance. The optimal contrast enhancement technique for detecting CNS pathology and for monitoring the effectiveness of medical therapy was also evaluated by a prospective study in which both immediate (IDD) and 1 hr delayed (DDD) double-dose contrast CT scans were compared. The examination found to be diagnostically superior in 30 of the 41 IDD/DDD studies was the delayed scan. It is recommended that CT be used routinely and with the 1 hr DDD scan to evaluate and follow AIDS patients with neurologic symptoms and/or signs.

  10. Effect of anaesthesia on contrast-enhanced ultrasound of the feline spleen.

    PubMed

    Leinonen, Merja R; Raekallio, Marja R; Vainio, Outi M; O'Brien, Robert T

    2011-11-01

    The spleens of 18 healthy cats were imaged using contrast-enhanced ultrasound (CEUS) to evaluate splenic perfusion and to compare perfusion patterns in awake and anaesthetised cats. Two groups of cats were imaged; the first (Group 1) consisted of 10 young, anaesthetised cats and the second (Group 2) comprised eight young to middle aged cats that were initially imaged when awake and later following anaesthesia. A two-phase enhancement of the spleen was observed both in awake and in anaesthetised cats. The time to first appearance of the contrast was significantly faster in awake (3.9±0.6s) than anaesthetised (4.8±1.0s) cats in Group 2 (P=0.031). A marked heterogeneous perfusion pattern was more prevalent in the anaesthetised (50%) compared to the awake (12.5%) animals in Group 2. The spleen was heterogeneous for approximately 30s in all groups. The results indicated that CEUS suspected focal perfusion defects of the spleen, especially during general anaesthesia, should be evaluated with caution and only after the initial heterogeneity has disappeared.

  11. Contrast enhancing and adjusting advanced very high resolution radiometer scenes for solar illumination

    USGS Publications Warehouse

    Zokaites, David M.

    1993-01-01

    The AVHRR (Advanced Very High Resolution Radiometer) satellite sensors provide daily coverage of the entire Earth. As a result, individual scenes cover broad geographic areas (roughly 3000 km by 5000 km) and can contain varying levels of solar illumination. Mosaics of AVHRR scenes can be created for large (continental and global) study areas. As the north-south extent of such mosaics increases, the lightness variability within the mosaic increases. AVHRR channels one and two of multiple daytime scenes were histogrammed to find a relationship between solar zenith and scene lightness as described by brightness value distribution. This relationship was used to determine look-up tables (luts) which removed effects of varying solar illumination. These luts were combined with a contrast enhancing lut and stored online. For individual scenes, one precomputed composite lut was applied to the entire scene based on the solar zenith at scene center. For mosaicked scenes, each pixel was adjusted based on the solar zenith at that pixel location. These procedures reduce lightness variability within and between scenes and enhance scene contrast to provide visually pleasing imagery.

  12. Nosocomial transmission of hepatitis C virus during contrast-enhanced computed tomography scanning.

    PubMed

    Quer, Josep; Esteban, Juan-Ignacio; Sánchez, Josep-Maria; Otero, Teresa; Rius, Cristina; Coll, Mar; Cubero, Maria; Moreno, Gina; Gonzalez, Antonio; Vaque, Josep; Esteban, Rafael; Campins, Magda; Pañella, Helena; Guardia, Jaume; Martell, Maria

    2008-01-01

    We have investigated two cases of acute hepatitis C that occurred in patients who underwent digestive endoscopy and contrast-enhanced computed tomography (CT) scanning at two different centers. Investigations to identify the sources of infection included an on-site review of diagnostic procedures, interview of the involved healthcare staff, serological testing of the patients who underwent the procedures before and after the index cases and a molecular analysis of viral isolates from the patients and from potential viremic sources. In both cases, the epidemiological investigation identified a chronic hepatitis C virus (HCV) carrier who had been subjected to CT-scanning immediately before the index patient. Genetic distance and molecular phylogenetic analyzes of HCV sequences showed a close relationship between the isolates from these carriers and those from the acute-hepatitis patients, strongly suggesting that patient-to-patient transmission had occurred during CT. This is the first report describing two well documented cases of HCV nosocomial patient-to-patient transmission during contrast-enhanced CT scanning.

  13. Benefits of contrast-enhanced multidetector row CT colonography for preoperative staging in colorectal cancer patients

    NASA Astrophysics Data System (ADS)

    Iinuma, Gen; Moriyama, Noriyuki; Satake, Mitso; Miyakawa, Kunihisa; Muramatsu, Yukio; Tateishi, Ukihide; Akasu, Takayuki; Otake, Yousuke; Fujii, Takahiro; Kobayashi, Toshiaki

    2003-05-01

    Recently, CT colonography has been recognized as an effective option for evaluating colorectal polyps in the USA. We have applied this technique to preoperative staging of colorectal cancer patients with a contrast-enhanced multi-detector row CT (MDCT). The use of manipulated multi-planar reconstruction (MPR) views in contrast-enhanced MDCT colonography proved advantageous for detecting lymph node metastases. Furthermore, 3-dimensional (3D) endoluminal images with Hansfield-transparency settings allowed vascular views of the colorectal wall for identification of invasive colorectal cancers. Using endoluminal images, increase in flow and pooling of blood related to angiogenesis of invasive cancer could be demonstrated, not only in the lymph nodes but also in the colorectal wall. Both MPR views and 3D endoluminal images can be acquired from the same 3D volumetric data generated by helical scanning in MDCT colonography, and both have great potential as modalities for computer-aided diagnosis (CAD) using blood flow information. Therefore the use of CAD can be expected to improve radiologists' diagnostic performance with regard to colorectal cancer.

  14. Contrast-enhanced CT imaging in patients with chronic kidney disease.

    PubMed

    von Stillfried, Saskia; Apitzsch, Jonas C; Ehling, Josef; Penzkofer, Tobias; Mahnken, Andreas H; Knüchel, Ruth; Floege, Jürgen; Boor, Peter

    2016-10-01

    Renal microvascular rarefaction characterizes chronic kidney disease (CKD). In murine models of CKD, micro-CT imaging reflected capillary rarefaction using quantification of renal relative blood volume (rBV). In addition, micro-CT imaging revealed morphological alterations of the intrarenal vasculature including reduced vascular branching and lumen diameter. Here, we retrospectively quantified rBV in contrast-enhanced CT angiography in patients and found that, compared to non-CKD patients, those with CKD and renal fibrosis had significantly reduced rBV in the renal cortex. rBV values closely mirrored capillary rarefaction in the corresponding nephrectomy specimens. In patients with follow-up CT angiography, reduction of renal function was paralleled by a decline in rBV. Using virtual autopsy, i.e., postmortem CT angiography, morphometry of intrarenal arteries in 3D-rendered CT images revealed significantly reduced arterial diameter and branching in CKD compared to non-CKD cases. In conclusion, in CKD patients, contrast-enhanced CT imaging with quantification of rBV correlates with functional renal vasculature, whereas virtual autopsy allows morphometric analyses of macrovascular changes. Importantly, the observed vascular alterations in CKD patients mirror those in animals with progressive CKD, suggesting a high relevance of animal models for studying vascular alterations in CKD and renal fibrosis. PMID:27582011

  15. Targeted Multifunctional Nanoparticles cure and image Brain Tumors: Selective MRI Contrast Enhancement and Photodynamic Therapy

    NASA Astrophysics Data System (ADS)

    Kopelman, Raoul

    2008-03-01

    Aimed at targeted therapy and imaging of brain tumors, our approach uses targeted, multi-functional nano-particles (NP). A typical nano-particle contains a biologically inert, non-toxic matrix, biodegradable and bio-eliminable over a long time period. It also contains active components, such as fluorescent chemical indicators, photo-sensitizers, MRI contrast enhancement agents and optical imaging dyes. In addition, its surface contains molecular targeting units, e.g. peptides or antibodies, as well as a cloaking agent, to prevent uptake by the immune system, i.e. enabling control of the plasma residence time. These dynamic nano-platforms (DNP) contain contrast enhancement agents for the imaging (MRI, optical, photo-acoustic) of targeted locations, i.e. tumors. Added to this are targeted therapy agents, such as photosensitizers for photodynamic therapy (PDT). A simple protocol, for rats implanted with human brain cancer, consists of tail injection with DNPs, followed by 5 min red light illumination of the tumor region. It resulted in excellent cure statistics for 9L glioblastoma.

  16. Contrast enhanced pulmonary magnetic resonance angiography for pulmonary embolism: Building a successful program.

    PubMed

    Nagle, Scott K; Schiebler, Mark L; Repplinger, Michael D; François, Christopher J; Vigen, Karl K; Yarlagadda, Rajkumar; Grist, Thomas M; Reeder, Scott B

    2016-03-01

    The performance of contrast enhanced pulmonary magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism (PE) is an effective non-ionizing alternative to contrast enhanced computed tomography and nuclear medicine ventilation/perfusion scanning. However, the technical success of these exams is very dependent on careful attention to the details of the MRA acquisition protocol and requires reader familiarity with MRI and its artifacts. Most practicing radiologists are very comfortable with the performance and interpretation of computed tomographic angiography (CTA) performed to detect pulmonary embolism but not all are as comfortable with the use of MRA in this setting. The purpose of this review is to provide the general radiologist with the tools necessary to build a successful pulmonary embolism MRA program. This review will cover in detail image acquisition, image interpretation, and some key elements of outreach that help to frame the role of MRA to consulting clinicians and hospital administrators. It is our aim that this resource will help build successful clinical pulmonary embolism MRA programs that are well received by patients and physicians, reduce the burden of medical imaging radiation, and maintain good patient outcomes. PMID:26860667

  17. Case Report of Contrast-Enhanced Ultrasound Features of Primary Hepatic Neuroendocrine Tumor

    PubMed Central

    Li, Wei; Zhuang, Bo-wen; Wang, Zhu; Liao, Bing; Hong, Ling-yao; Xu, Ming; Lin, Xiao-na; Xie, Xiao-yan; Lu, Ming-de; Chen, Li-da; Wang, Wei

    2016-01-01

    Abstract Primary hepatic neuroendocrine tumors (PHNETs) are very rare and their clinical features and treatment outcomes are not well understood. It is difficult to reach a proper diagnosis before biopsy or resection. The aim of this study was to analyze the imaging features of PHNETs on contrast-enhanced ultrasound (CEUS). The clinical characteristics, CEUS findings, pathological features, treatment and prognosis of 6 patients with PHNET treated in our hospital were retrospectively analyzed. Most PHNETs occurred in middle-aged patients, and the most common clinical manifestation was right upper quadrant palpable mass and abdominal pain. Multiple small anechoic intralesional cavities occurred frequently in PHNET. Multilocular cystic with internal septation or monolocular with wall nodule could also be detected. On contrast-enhanced ultrasonography (CEUS), heterogeneous hyperenhancement in the arterial phase and wash-out hypoenhancement were observed in most patients, while computed tomography scanning yielded similar results. Diagnosis of PHNET was confirmed by immunohistochemical result and follow-up with the absence of extrahepatic primary sites. Five patients received surgical resection and 2 cases exhibited recurrence. Transcatheter arterial chemoembolization was performed in 1 patient with recurrence. Only 1 patient received conservative care. The median overall survival in 5 patients who underwent surgical treatment was 27 months (18–36 months). PHNET is a rare tumor, and its diagnosis is difficult. The CEUS features reported in this series may enrich the knowledge base for characterization of PHNET. PMID:27227910

  18. The Feasibility of Contrast-Enhanced Ultrasound During Uterine Artery Embolization: A Pilot Study

    SciTech Connect

    Dorenberg, Eric J. Jakobsen, Jarl A.; Brabrand, Knut; Hafsahl, Geir; Smith, Hans-Jorgen

    2007-09-15

    Purpose. To evaluate the feasibility of using contrast-enhanced ultrasound (CEUS) during uterine artery embolization (UAE) in order to define the correct end-point of embolization with complete devascularization of all fibroids. Methods. In this prospective study of 10 consecutive women undergoing UAE, CEUS was performed in the angiographic suite during embolization. When the angiographic end-point, defined as the 'pruned-tree' appearance of the uterine arteries was reached, CEUS was performed while the angiographic catheters to both uterine arteries were kept in place. The decision whether or not to continue the embolization was based on the findings at CEUS. The results of CEUS were compared with those of contrast-enhanced magnetic resonance imaging (MRI) 1 day as well as 3 months following UAE. Results. CEUS was successfully performed in all women. In 4 cases injection of particles was continued based on the findings at CEUS despite angiographically complete embolization. CEUS imaging at completion of UAE correlated well with the findings at MRI. Conclusion. The use of CEUS during UAE is feasible and may increase the quality of UAE.

  19. Photoacoustic imaging and surface-enhanced Raman spectroscopy using dual modal contrast agents

    NASA Astrophysics Data System (ADS)

    Park, Sungjo; Lee, Seunghyun; Cha, Myeonggeun; Jeong, Cheolhwan; Kang, Homan; Park, So Yeon; Lee, Yoon-sik; Jeong, Daehong; Kim, Chulhong

    2016-03-01

    Recently, photoacoustic tomography (PAT) has emerged as a remarkable non-invasive imaging modality that provides a strong optical absorption contrast, high ultrasonic resolution, and great penetration depth. Thus, PAT has been widely used as an in vivo preclinical imaging tool. Surface-enhanced Raman spectroscopy (SERS) is another attractive sensing technology in biological research because it offers highly sensitive chemical analyses and multiplexed detection. By performing dual-modal imaging of SERS and PAT, high-resolution structural PAT imaging and high-sensitivity SERS sensing can be achieved. At the same time, it is equally important to develop a dual modal contrast agent for this purpose. To perform both PAT and SERS, we synthesized PEGylated silver bumpy nanoshells (AgBSs). The AgBSs generate strong PA signals owing to their strong optical absorption properties as well as sensitive SERS signals because of the surface plasmon resonance effect. Then, multiplexed Raman chemicals were synthesized to enhance the sensitivity of Raman. We have photoacoustically imaged the sentinel lymph nodes of small animals after intradermal injection of multiplexed agents. Furthermore, the chemical composition of each agent has been distinguished through SERS.

  20. A game-theoretic architecture for visible watermarking system of ACOCOA (adaptive content and contrast aware) technique

    NASA Astrophysics Data System (ADS)

    Tsai, Min-Jen; Liu, Jung

    2011-12-01

    Digital watermarking techniques have been developed to protect the intellectual property. A digital watermarking system is basically judged based on two characteristics: security robustness and image quality. In order to obtain a robust visible watermarking in practice, we present a novel watermarking algorithm named adaptive content and contrast aware (ACOCOA), which considers the host image content and watermark texture. In addition, we propose a powerful security architecture against attacks for visible watermarking system which is based on game-theoretic approach that provides an equilibrium condition solution for the decision maker by studying the effects of transmission power on intensity and perceptual efficiency. The experimental results demonstrate that the feasibility of the proposed approach not only provides effectiveness and robustness for the watermarked images, but also allows the watermark encoder to obtain the best adaptive watermarking strategy under attacks.

  1. Adaptation to climate change: contrasting patterns of thermal-reaction-norm evolution in Pacific versus Atlantic silversides

    PubMed Central

    Baumann, Hannes; Conover, David O.

    2011-01-01

    How organisms may adapt to rising global temperatures is uncertain, but concepts can emerge from studying adaptive physiological trait variations across existing spatial climate gradients. Many ectotherms, particularly fish, have evolved increasing genetic growth capacities with latitude (i.e. countergradient variation (CnGV) in growth), which are thought to be an adaptation primarily to strong gradients in seasonality. In contrast, evolutionary responses to gradients in mean temperature are often assumed to involve an alternative mode, ‘thermal adaptation’. We measured thermal growth reaction norms in Pacific silverside populations (Atherinops affinis) occurring across a weak latitudinal temperature gradient with invariant seasonality along the North American Pacific coast. Instead of thermal adaptation, we found novel evidence for CnGV in growth, suggesting that CnGV is a ubiquitous mode of reaction-norm evolution in ectotherms even in response to weak spatial and, by inference, temporal climate gradients. A novel, large-scale comparison between ecologically equivalent Pacific versus Atlantic silversides (Menidia menidia) revealed how closely growth CnGV patterns reflect their respective climate gradients. While steep growth reaction norms and increasing growth plasticity with latitude in M. menidia mimicked the strong, highly seasonal Atlantic coastal gradient, shallow reaction norms and much smaller, latitude-independent growth plasticity in A. affinis resembled the weak Pacific latitudinal temperature gradient. PMID:21208956

  2. Contrast-enhanced MR angiography utilizing parallel acquisition techniques in renal artery stenosis detection.

    PubMed

    Slanina, Martin; Zizka, Jan; Klzo, Ludovít; Lojík, Miroslav

    2010-07-01

    Significant renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension and/or renal impairment. It is caused by either atherosclerosis or fibromuscular dysplasia. Correct and timely diagnosis remains a diagnostic challenge. MR angiography (MRA) as a minimally invasive method seems to be suitable for RAS detection, however, its diagnostic value widely differs in the literature (sensitivity 62-100% and specificity 75-100%). The aim of our prospective study was to compare the diagnostic value of contrast-enhanced MRA utilizing parallel acquisition techniques in the detection of significant RAS with digital subtraction angiography (DSA). A total of 78 hypertensive subjects with suspected renal artery stenosis were examined on a 1.5 Tesla MR system using a body array coil. Bolus tracking was used to monitor the arrival of contrast agent to the abdominal aorta. The MRA sequence parameters were as follows: TR 3.7 ms; TE 1.2 ms; flip angle 25 degrees; acquisition time 18s; voxel size 1.1 mm x1.0 mm x 1.1 mm; centric k-space sampling; parallel acquisition technique with acceleration factor of 2 (GRAPPA). Renal artery stenosis of 60% and more was considered hemodynamically significant. The results of MRA were compared to digital subtraction angiography serving as a standard of reference. Sensitivity and specificity of MRA in the detection of hemodynamically significant renal artery stenosis were 90% and 96%, respectively. Prevalence of RAS was 39% in our study population. Contrast-enhanced MRA with high spatial resolution offers sufficient sensitivity and specificity for screening of RAS. PMID:19671492

  3. Role of Contrast Enhanced Ultrasound in Radiofrequency Ablation of Metastatic Liver Carcinoma

    PubMed Central

    Wu, Jin-yu; Yang, Wei; Lin, Shu-zhi; Wu, Wei; Yin, Shan-shan; Zhang, Hui; Yan, Kun

    2012-01-01

    Objective To investigate the application of contrast enhanced ultrasound (CEUS) in planning and guiding for radiofrequency ablation (RFA) for metastatic liver carcinoma (MLC). Methods One hundred and thirty-five patients with clinically and pathologically diagnosed MLC (from gastrointestinal tumors) were included in the present study, and 104 of them had received CEUS prior to RFA to assess the number, size, shape, infiltration, location and enhancing features of the lesions. Among the 104 patients, 21 (20.1%) were excluded from RFA treatment due to too many lesions or large infiltrative range based on CEUS. The remaining 83 patients with 147 lesions underwent RFA (group A). During the same period, other 31 patients with 102 lesions serving as control group were treated based on findings of conventional ultrasound without contrast (group B). The patients underwent follow-up enhanced CT at the 1st month, and then every 3–6 months after RFA. The tumor was considered as early necrosis if no contrast enhancement was detected in the treated area on the CT scan at the 1st month. Results In group A, 72 of 147 MLC lesions (48.9%) showed increased sizes on CEUS. Among them, 48 lesions (66.6%) appeared enlarged in arterial phase, and 24 (33.3%) showed enlarged hypoechoic area in parenchymal phase. CEUS showed total 61 additional lesions in 35 patients (42.1%) (ranged from 8 to 15 mm) compared with conventional ultrasound (US), and 42 (68.8%) of them were visualized in parenchymal phase only. There were total 208 lesions in group A underwent RFA with CEUS planning, and the tumor necrosis rate was 94.2% (196/208). In this group, local recurrence was found in 16 lesions (7.7%) during 3–42 months’ following up, and new metastases were seen in 30 cases (36.1%). For group B, the tumor necrosis rate was 86.3% (88/102), local recurrence in 17 lesions (16.7%), and new metastases in 13 cases (41.9%). Tumor early necrosis and recurrence rates were significantly different between

  4. Differential diagnosis of gallbladder wall thickening: the usefulness of contrast-enhanced ultrasound.

    PubMed

    Xu, Jun-Mei; Guo, Le-Hang; Xu, Hui-Xiong; Zheng, Shu-Guang; Liu, Lin-Na; Sun, Li-Ping; Lu, Ming-De; Wang, Wen-Ping; Hu, Bing; Yan, Kun; Hong, Ding; Tang, Shao-Shan; Qian, Lin-Xue; Luo, Bao-Ming

    2014-12-01

    he purpose of this study was to evaluate the usefulness of contrast-enhanced ultrasound (CEUS) in the differential diagnosis of gallbladder wall (GBW) thickening and determine the predictors of malignant GBW thickening. One hundred fifty-nine patients with GBW thickening, including 76 men and 83 women, from eight institutions were enrolled. CEUS was performed after injection of a sulfur hexafluoride microbubble-based ultrasound contrast agent. Multiple logistic regression analysis was used to reveal independent predictor sassociated with malignant GBW thickening. The final diagnoses were 48 gallbladder carcinomas and 111 benign gallbladder diseases.Maximal thicknesses of the GBW in malignant and benign GB Wthickening were 17.3 ± 5.2 (6 – 30) mm and 8.6 ± 5.1 (4 – 26) mm respectively (p , 0.001). CEUS revealed significant differences in intralesional vessels, enhancement homogeneity, time to hypo-enhancement, inner layer discontinuity, outer layer discontinuity and adjacent liver involvement (all p-values , 0.05) between malignant and benign GBW thickening. Patient age . 46.5 y, focal GBW thickening, inner layer discontinuity and outer layer discontinuity were found to be associated with malignancy by multiple logistic regression analysis (all p-values , 0.05). Receiver operating characteristic curve analysis revealed Az values for patient age, focal GBW thickening, inner wall discontinuity and outer wall discontinuity of 0.709 (95%confidence interval [CI]: 0.627–0.790), 0.714 (95% CI: 0.630–0.798), 0.860 (95%CI: 0.791 – 0.928) and 0.858 (95% CI: 0.783 – 0.933), respectively. CEUS is useful in the differential diagnosis between malignant and benign GBW thickening. Focal GBW thickening, inner wall discontinuity and outer wall discontinuity observed on CEUS are diagnostic clues for malignant GBW thickening.

  5. Intravascular contrast agent-enhanced MRI measuring contrast clearance and tumor blood volume and the effects of vascular modifiers in an experimental tumor

    SciTech Connect

    Bentzen, Lise . E-mail: lise@oncology.dk; Vestergaard-Poulsen, Peter; Nielsen, Thomas; Overgaard, Jens; Bjornerud, Atle; Briley-Saebo, Karen; Horsman, Michael R.; Ostergaard, Leif

    2005-03-15

    Purpose: To examine the feasibility of using the MRI blood pool agent NC100150 for evaluation of tumor blood volume (TBV) estimates by both dynamic contrast-enhanced MRI (DCE-MRI) and susceptibility contrast MRI assays in an experimental tumor. Contrast agent clearance (K{sup trans}; depends on perfusion and permeability) from the DCE-MRI time curves was estimated, and changes in TBV and K{sup trans} were measured after administration of two drugs that reduce perfusion by different mechanisms. Methods and materials: The DCE-MRI experiments were simulated with expected physiologic values for the C3H mouse mammary carcinoma. The C3H tumor was examined by DCE-MRI and susceptibility contrast MRI with NC100150 (NC100150 Injection, Clariscan; Amersham Health, Oslo, Norway) after treatment with either hydralazine or combretastatin (Oxigene, Boston, MA). Results: Simulations showed that reliable estimates of changes in TBV and K{sup trans} could be performed with DCE-MRI. Hydralazine was shown to reduce TBV as measured by both assays and to reduce K{sup trans}. Dynamic contrast-enhanced MRI also suggested that TBV and K{sup trans} were reduced in combretastatin-treated tumors, and the TBV reduction was confirmed by susceptibility contrast MRI. Data suggested the drug to affect mainly the total TBV, whereas microvessels as such seemed less altered. Conclusion: The study supports the use of the combined DCE-MRI and susceptibility contrast MRI assay with a blood pool agent in characterizing tumors and their response to treatment.

  6. 75 FR 34988 - Federal Advisory Committee; Defense Science Board 2010 Summer Study on Enhancing Adaptability of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-21

    ... of the Secretary Federal Advisory Committee; Defense Science Board 2010 Summer Study on Enhancing... meeting. SUMMARY: The Defense Science Board 2010 Summer Study on Enhancing Adaptability of our Military... of adaptation, both commercial and non-commercial, and what made them successful and...

  7. Role of Dynamic Contrast-Enhanced Magnetic Resonance Imaging in Staging of Bladder Cancer

    PubMed Central

    Rabie, Elham; Izadpanahi, Mohammad-Hossein; Dayani, Mohammad-Ali

    2016-01-01

    Introduction Dynamic Contrast Enhanced (DCE)-Magnetic Resonance Imaging (MRI) is a useful technique in which rapid enhancement of tumour by uptake of the contrast agent compared to bladder wall. Aim To evaluate the accuracy of dynamic gadolinium-enhanced MRI in staging of bladder cancer through differentiating superficial tumours from invasive tumours and organ-confined tumours from non-organ-confined tumours. In addition, the benefits of DCE-MRI in diagnosis of tumour progression steps were investigated. Materials and Methods This was a quasi-experimental study in which 45 patients (95.55% men and 4.45% women) were enrolled. Patients with confirmed transitional cell carcinoma by histopathology findings were imaged using 1.5 Tesla MRI systems. Pathology results were considered as the standard reference. Tumour stage was determined by imaging findings and compared with pathologic findings after radical cystectomy. Data were analysed by SPSS version 16 and the level of significance in all tests was considered p<0.001. Results The most common stage that was seen in pathology and MRI findings was T3b. Kappa agreement coefficient between MRI and pathology was 0.7 (p<0.001). The accuracy of MRI in differentiating superficial tumours (≤T1) from invasive tumours (≥ T2a), and organ-confined tumours (≤T2b) from non-organ-confined tumours (≥T3b) was 0.97 and 0.84, respectively. The overall accuracy of MRI was 0.77 (p<0.001). Totally, 10 cases of disagreement between MRI and pathological staging were found, eight (80%) of which were overestimated and two cases (20%) underestimated. MRI detection rate was 0% in stage Ta, 100% in stage T1, 66.7% in stage T2, 86.7% in stage T3, and 100% in stage T4. The sensitivity and specificity of MRI in differentiating superficial tumours from invasive tumours were 0.97 and 1, respectively, and in differentiating organ-confined tumours from non-organ-confined tumours were 0.94 and 0.77, respectively. The Spearman’s correlation

  8. 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.

  9. Visualization of 3D geometric models of the breast created from contrast-enhanced MRI

    NASA Astrophysics Data System (ADS)

    Leader, J. Ken, III; Wang, Xiao Hui; Chang, Yuan-Hsiang; Chapman, Brian E.

    2002-05-01

    Contrast enhanced breast MRI is currently used as an adjuvant modality to x-ray mammography because of its ability to resolve ambiguities and determine the extent of malignancy. This study described techniques to create and visualize 3D geometric models of abnormal breast tissue. MRIs were performed on a General Electric 1.5 Tesla scanner using dual phased array breast coils. Image processing tasks included: 1) correction of image inhomogeneity caused by the coils, 2) segmentation of normal and abnormal tissue, and 3) modeling and visualization of the segmented tissue. The models were visualized using object-based surface rendering which revealed characteristics critical to differentiating benign from malignant tissue. Surface rendering illustrated the enhancement distribution and enhancement patterns. The modeling process condensed the multi-slice MRI data information and standardized its interpretation. Visualizing the 3D models should improve the radiologist's and/or surgeon's impression of the 3D shape, extent, and accessibility of the malignancy compared to viewing breast MRI data slice by slice.

  10. Contrast-enhanced ultrasonographic characteristics of the diseased canine prostate gland.

    PubMed

    Troisi, Alessandro; Orlandi, Riccardo; Bargellini, Paolo; Menchetti, Laura; Borges, Paulo; Zelli, Riccardo; Polisca, Angela

    2015-11-01

    The work was carried out on a total of 26 male dogs that on the basis of clinical examination, prostate ultrasound and prostate biopsy, were divided prospectively into four groups: (1) normal dogs (control group; n = 8); (2) dogs with benign prostatic hyperplasia (group BPH; n = 8); (3) dogs suffering from prostatitis (group prostatitis; n = 4); (4) dogs with prostatic tumors (group tumors; n = 6). The examination of the prostate by means of contrast medium and dedicated ultrasound system allowed a detailed qualitative and quantitative analysis of prostatic vessels in normal and diseased conditions, enabling the detection and characterization of different disease states, and quantification of parameters such as peak intensity of perfusion (%), arrival time of the contrast medium to its maximum value of video intensity (time to peak [TTP; seconds]), regional blood volume, regional blood flow, and mean transit time (MTT [seconds]). The hemodynamic indices TTP (P < 0.01) and MTT (P < 0.001) of diseased prostate groups were significantly lower than those in the normal prostate group although there were no differences among diseases. Optimal cutoff values were 31 seconds (Sensitivity: 72%; Specificity: 88%) and 47 seconds (Sensitivity: 100%; Specificity: 88%) while area under receiver operating characteristic curves were 0.86 (P < 0.01) and 0.97 (P < 0.01) for TTP and MTT, respectively. The qualitative evaluation of vascular patterns showed differences between normal and diseased prostate glands. The latter were characterized by an alteration of the normal vascular appearance consisting of loss of the subcapsular arterioles and lack of a centripetal vascular pattern. The qualitative aspect of the study highlighted the different vascular architecture between BPH, prostatitis, adenocarcinoma, and lymphoma. This study shows how contrast-enhanced ultrasound represents a valid and noninvasive method for highlighting and characterizing prostatic vasculature

  11. TH-A-18C-08: Design of a Small Animal Contrast Enhanced Dual Energy CT

    SciTech Connect

    Martin, R; Pan, T; Li, B

    2014-06-15

    Purpose: Dual energy CT has a variety of uses in a small animal setting including quantification and enhanced visualization of contrast agent. This study aims to determine the best energy combinations for contrast enhanced DECT on the XRAD 225Cx (Precision x-ray), a small animal IGRT system with a nominal energy range of 20 – 225 kVp. Focus was placed on material density accuracy and low contrast detectability. Methods: Simulations of single energy scans of an object containing concentrations of iodine varying from 0.5 to 50 mg/ml were performed using the simulation package ImaSim. Energy spectra from 50 – 220 kVp were calculated using the same software. For approximate Poisson noise modeling, mAs were chosen such that 30% of the total 10cGy dose was assigned to the low energy scan. A calibration involving projections of objects containing different thicknesses of iodine (0–0.5 mm) and water (0–50 mm) was performed for each energy and fit to a cubic equation as the calibration curve for each energy pair. Results: Contrast to noise ratios of the iodine material images and accuracies in iodine density measurements were measured. Gradual improvements in each metric were seen with increasing high energy. Larger improvements in CNR were observed for decreasing the low energy. Errors in iodine density were generally close to 5% for concentrations of iodine above 3 mg/ml but increased to around 15% for 50 kVp, likely due to its proximity to the discontinuity caused by the k-edge of iodine. Conclusion: Based on these simulations, the best energy combination for detecting low concentrations of iodine using a projection space calibration procedure is 50/200 kVp. However, if accuracy is most important 80/220 kVp is ideal, with 60/220 kVp being a good compromise to achieve both goals. Future work is necessary to verify these conclusions with physical data.

  12. Kinetic Curve Type Assessment for Classification of Breast Lesions Using Dynamic Contrast-Enhanced MR Imaging

    PubMed Central

    Chen, Jun-Ming; Zhang, Geoffrey; Liao, Yen-Hsiu; Huang, Tzung-Chi

    2016-01-01

    Objective The aim of this study was to employ a kinetic model with dynamic contrast enhancement-magnetic resonance imaging to develop an approach that can efficiently distinguish malignant from benign lesions. Materials and Methods A total of 43 patients with 46 lesions who underwent breast dynamic contrast enhancement-magnetic resonance imaging were included in this retrospective study. The distribution of malignant to benign lesions was 31/15 based on histological results. This study integrated a single-compartment kinetic model and dynamic contrast enhancement-magnetic resonance imaging to generate a kinetic modeling curve for improving the accuracy of diagnosis of breast lesions. Kinetic modeling curves of all different lesions were analyzed by three experienced radiologists and classified into one of three given types. Receiver operating characteristic and Kappa statistics were used for the qualitative method. The findings of the three radiologists based on the time-signal intensity curve and the kinetic curve were compared. Results An average sensitivity of 82%, a specificity of 65%, an area under the receiver operating characteristic curve of 0.76, and a positive predictive value of 82% and negative predictive value of 63% was shown with the kinetic model (p = 0.017, 0.052, 0.068), as compared to an average sensitivity of 80%, a specificity of 55%, an area under the receiver operating characteristic of 0.69, and a positive predictive value of 79% and negative predictive value of 57% with the time-signal intensity curve method (p = 0.003, 0.004, 0.008). The diagnostic consistency of the three radiologists was shown by the κ-value, 0.857 (p<0.001) with the method based on the time-signal intensity curve and 0.826 (p<0.001) with the method of the kinetic model. Conclusions According to the statistic results based on the 46 lesions, the kinetic modeling curve method showed higher sensitivity, specificity, positive and negative predictive values as compared with

  13. Speech Enhancement, Gain, and Noise Spectrum Adaptation Using Approximate Bayesian Estimation.

    PubMed

    Hao, Jiucang; Attias, Hagai; Nagarajan, Srikantan; Lee, Te-Won; Sejnowski, Terrence J

    2009-01-01

    This paper presents a new approximate Bayesian estimator for enhancing a noisy speech signal. The speech model is assumed to be a Gaussian mixture model (GMM) in the log-spectral domain. This is in contrast to most current models in frequency domain. Exact signal estimation is a computationally intractable problem. We derive three approximations to enhance the efficiency of signal estimation. The Gaussian approximation transforms the log-spectral domain GMM into the frequency domain using minimal Kullback-Leiber (KL)-divergency criterion. The frequency domain Laplace method computes the maximum a posteriori (MAP) estimator for the spectral amplitude. Correspondingly, the log-spectral domain Laplace method computes the MAP estimator for the log-spectral amplitude. Further, the gain and noise spectrum adaptation are implemented using the expectation-maximization (EM) algorithm within the GMM under Gaussian approximation. The proposed algorithms are evaluated by applying them to enhance the speeches corrupted by the speech-shaped noise (SSN). The experimental results demonstrate that the proposed algorithms offer improved signal-to-noise ratio, lower word recognition error rate, and less spectral distortion. PMID:20428253

  14. T₁ and T₂ dual-mode MRI contrast agent for enhancing accuracy by engineered nanomaterials.

    PubMed

    Shin, Tae-Hyun; Choi, Jin-sil; Yun, Seokhwan; Kim, Il-Sun; Song, Ho-Taek; Kim, Youngmee; Park, Kook In; Cheon, Jinwoo

    2014-04-22

    One of the holy grails in biomedical imaging technology is to achieve accurate imaging of biological targets. The development of sophisticated instrumentation and the use of contrast agents have improved the accuracy of biomedical imaging. However, the issue of false imaging remains a problem. Here, we developed a dual-mode artifact filtering nanoparticle imaging agent (AFIA) that comprises a combination of paramagnetic and superparamagnetic nanomaterials. This AFIA has the ability to perform "AND logic gate" algorithm to eliminate false errors (artifacts) from the raw images to enhance accuracy of the MRI. We confirm the artifact filtering capability of AFIA in MRI phantoms and further demonstrate that artifact-free imaging of stem cell migration is possible in vivo.

  15. Diagnostic vascular ultrasonography with the help of color Doppler and contrast-enhanced ultrasonography.

    PubMed

    Rübenthaler, Johannes; Reiser, Maximilian; Clevert, Dirk-André

    2016-10-01

    The use of ultrasonography and especially of contrast-enhanced ultrasonography (CEUS) in the diagnosis of vascular pathologies before and after interventions has significantly increased over the past years due to the broader availability of modern ultrasound systems with CEUS capabilities and more trained user experience in this imaging modality. For the preinterventional and postinterventional work-up of carotid diseases, duplex ultrasound as well as CEUS have been established as the standard-of-care examination procedures for diagnosis, evaluation, and follow-up. In addition to its use for carotid arterial diseases, ultrasonography has also become the primary modality for the screening of vascular pathologies. This review describes the most common pathologies found in ultrasonography of the carotid arteries, the abdominal aorta, and the femoral arteries. PMID:27669962

  16. Three-dimensional resolution and contrast-enhanced confocal microscopy with array detection.

    PubMed

    Ge, Baoliang; Wang, Yifan; Huang, Yujia; Kuang, Cuifang; Fang, Yue; Xiu, Peng; Rong, Zihao; Liu, Xu

    2016-05-01

    What we believe is a novel method for improving confocal microscopy's resolution and contrast in 3D space is proposed. Based on a conventional confocal microscopy setup, we use an array detector composed of 32 photomultiplier tubes (PMTs) to replace one point-detector, where the location offset of each PMT caused a different effective point spread function (PSF). By applying array detection and the fluorescence emission difference method of an image with a solid PSF and another with a donut-shaped PSF, we can enhance lateral resolution about 27% in real time with only one scan, and improve the axial resolving ability by about 22% simultaneously. Experimental results of both fluorescent beads and living cells are presented to verify the applicability and effectiveness of our method. PMID:27128062

  17. Diagnostic vascular ultrasonography with the help of color Doppler and contrast-enhanced ultrasonography

    PubMed Central

    2016-01-01

    The use of ultrasonography and especially of contrast-enhanced ultrasonography (CEUS) in the diagnosis of vascular pathologies before and after interventions has significantly increased over the past years due to the broader availability of modern ultrasound systems with CEUS capabilities and more trained user experience in this imaging modality. For the preinterventional and postinterventional work-up of carotid diseases, duplex ultrasound as well as CEUS have been established as the standard-of-care examination procedures for diagnosis, evaluation, and follow-up. In addition to its use for carotid arterial diseases, ultrasonography has also become the primary modality for the screening of vascular pathologies. This review describes the most common pathologies found in ultrasonography of the carotid arteries, the abdominal aorta, and the femoral arteries. PMID:27669962

  18. Phenomenological universalities: a novel tool for the analysis of dynamic contrast enhancement in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Gliozzi, A. S.; Mazzetti, S.; Delsanto, P. P.; Regge, D.; Stasi, M.

    2011-02-01

    Dynamic contrast enhancement in magnetic resonance imaging (DCE-MRI) is a promising tool for the clinical diagnosis of tumors, whose implementation may be improved through the use of suitable hemodynamic models. If one prefers to avoid assumptions about the tumor physiology, empirical fitting functions may be adopted. For this purpose, in this paper we discuss the exploitation of a recently proposed phenomenological universalities (PUN) formalism. In fact, we show that a novel PUN class may be used to describe the time-signal intensity curves in both healthy and tumoral tissues, discriminating between the two cases and thus potentially providing a convenient diagnostic tool. The proposed approach is applied to analysis of the DCE-MRI data relative to a study group composed of ten patients with spine tumors.

  19. Automated lesion detection in dynamic contrast enhanced magnetic resonance imaging of breast

    NASA Astrophysics Data System (ADS)

    Liang, Xi; Kotagiri, Romamohanarao; Frazer, Helen; Yang, Qing

    2015-03-01

    We propose an automated method in detecting lesions to assist radiologists in interpreting dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) of breast. The aim is to highlight the suspicious regions of interest to reduce the searching time of the lesions and the possibility of radiologists overlooking small regions. In our method, we locate the suspicious regions by applying a threshold on essential features. The features are normalized to reduce the variation between patients. Support vector machine classifier is then applied to exclude normal tissues from these regions, using both kinetic and morphological features extracted in the lesions. In the evaluation of the system on 21 patients with 50 lesions, all lesions were successfully detected with 5.02 false positive regions per breast.

  20. SU-E-T-56: Brain Metastasis Treatment Plans for Contrast-Enhanced Synchrotron Radiation Therapy

    SciTech Connect

    Obeid, L; Adam, J; Tessier, A; Vautrin, M; Benkebil, M; Sihanath, R

    2014-06-01

    Purpose: Iodine-enhanced radiotherapy is an innovative treatment combining the selective accumulation of an iodinated contrast agent in brain tumors with irradiations using monochromatic medium energy x-rays. The aim of this study is to compare dynamic stereotactic arc-therapy and iodineenhanced SSRT. Methods: Five patients bearing brain metastasis received a standard helical 3D-scan without iodine. A second scan was acquired 13 min after an 80 g iodine infusion. Two SSRT treatment plans (with/without iodine) were performed for each patient using a dedicated Monte Carlo (MC) treatment planning system (TPS) based on the ISOgray TPS. Ten coplanar beams (6×6 cm2, shaped with collimator) were simulated. MC statistical error objective was less than 5% in the 50% isodose. The dynamic arc-therapy plan was achieved on the Iplan Brainlab TPS. The treatment plan validation criteria were fixed such that 100% of the prescribed dose is delivered at the beam isocentre and the 70% isodose contains the whole target volume. The comparison elements were the 70% isodose volume, the average and maximum doses delivered to organs at risk (OAR): brainstem, optical nerves, chiasma, eyes, skull bone and healthy brain parenchyma. Results: The stereotactic dynamic arc-therapy remains the best technique in terms of dose conformation. Iodine-enhanced SSRT presents similar performances to dynamic arc-therapy with increased brainstem and brain parenchyma sparing. One disadvantage of SSRT is the high dose to the skull bone. Iodine accumulation in metastasis may increase the dose by 20–30%, allowing a normal tissue sparing effect at constant prescribed dose. Treatment without any iodine enhancement (medium-energy stereotactic radiotherapy) is not relevant with degraded HDVs (brain, parenchyma and skull bone) comparing to stereotactic dynamic arc-therapy. Conclusion: Iodine-enhanced SSRT exhibits a good potential for brain metastasis treatment regarding the dose distribution and OAR criteria.

  1. The efficacy of contrast-enhanced harmonic endoscopic ultrasonography in diagnosing gallbladder cancer.

    PubMed

    Sugimoto, Mitsuru; Takagi, Tadayuki; Konno, Naoki; Suzuki, Rei; Asama, Hiroyuki; Hikichi, Takuto; Watanabe, Ko; Waragai, Yuichi; Kikuchi, Hitomi; Takasumi, Mika; Ohira, Hiromasa

    2016-01-01

    The aim of this study was to review the efficacy of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) in diagnosing gallbladder (GB)-protruded lesions. Thirty-eight patients underwent CH-EUS for the diagnosis of GB-protruded lesions. Twenty-four patients whose major axes of their largest lesions were longer than 10 mm were recruited. The ability of CH-EUS to diagnose malignant or benign lesions was reviewed. We treated lesions with brindled enhanced patterns as malignant and those with uniformly enhanced or unenhanced patterns as benign. Furthermore, three gastroenterologists who were not familiar with pancreaticobiliary EUS compared the diagnostic abilities of CH-EUS and conventional EUS using photographs. The sensitivity, specificity, and malignant accuracy of CH-EUS were 100, 94.4, and 95.8%, respectively. The number of lesions that presented with enhanced patterns was significantly different between the malignant lesions and the benign lesions (P < 0.001). In the comparison of diagnostic abilities between CH-EUS and conventional EUS by the three gastroenterologists, CH-EUS was significantly superior to conventional EUS in terms of sensitivity, specificity, and accuracy (76.1 vs. 42.9%, P = 0.029; 66.7 vs. 39.2%, P = 0.005; and 69.4 vs. 40.3%, P < 0.001; respectively). In conclusion, CH-EUS was useful for diagnosing malignant and benign GB-protruded lesions.

  2. The efficacy of contrast-enhanced harmonic endoscopic ultrasonography in diagnosing gallbladder cancer

    PubMed Central

    Sugimoto, Mitsuru; Takagi, Tadayuki; Konno, Naoki; Suzuki, Rei; Asama, Hiroyuki; Hikichi, Takuto; Watanabe, Ko; Waragai, Yuichi; Kikuchi, Hitomi; Takasumi, Mika; Ohira, Hiromasa

    2016-01-01

    The aim of this study was to review the efficacy of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) in diagnosing gallbladder (GB)-protruded lesions. Thirty-eight patients underwent CH-EUS for the diagnosis of GB-protruded lesions. Twenty-four patients whose major axes of their largest lesions were longer than 10 mm were recruited. The ability of CH-EUS to diagnose malignant or benign lesions was reviewed. We treated lesions with brindled enhanced patterns as malignant and those with uniformly enhanced or unenhanced patterns as benign. Furthermore, three gastroenterologists who were not familiar with pancreaticobiliary EUS compared the diagnostic abilities of CH-EUS and conventional EUS using photographs. The sensitivity, specificity, and malignant accuracy of CH-EUS were 100, 94.4, and 95.8%, respectively. The number of lesions that presented with enhanced patterns was significantly different between the malignant lesions and the benign lesions (P < 0.001). In the comparison of diagnostic abilities between CH-EUS and conventional EUS by the three gastroenterologists, CH-EUS was significantly superior to conventional EUS in terms of sensitivity, specificity, and accuracy (76.1 vs. 42.9%, P = 0.029; 66.7 vs. 39.2%, P = 0.005; and 69.4 vs. 40.3%, P < 0.001; respectively). In conclusion, CH-EUS was useful for diagnosing malignant and benign GB-protruded lesions. PMID:27162097

  3. Dynamic contrast enhanced T1 MRI perfusion differentiates pseudoprogression from recurrent glioblastoma.

    PubMed

    Thomas, Alissa A; Arevalo-Perez, Julio; Kaley, Thomas; Lyo, John; Peck, Kyung K; Shi, Weiji; Zhang, Zhigang; Young, Robert J

    2015-10-01

    Pseudoprogression may present as transient new or increasing enhancing lesions that mimic recurrent tumors in treated glioblastoma. The purpose of this study was to examine the utility of dynamic contrast enhanced T1 magnetic resonance imaging (DCE MRI) in differentiating between pseudoprogression and tumor progression and devise a cut-off value sensitive for pseudoprogression. We retrospectively examined 37 patients with glioblastoma treated with radiation and temozolomide after surgical resection that then developed new or increasing enhancing lesion(s) indeterminate for pseudoprogression versus progression. Volumetric plasma volume (Vp) and time-dependent leakage constant (Ktrans) maps were measured for the enhancing lesion and the mean and ninetieth percentile histogram values recorded. Lesion outcome was determined by clinical follow up with pseudoprogression defined as stable disease not requiring new treatment. Statistical analysis was performed with Wilcoxon rank-sum tests. Patients with pseudoprogression (n = 13) had Vp (mean) = 2.4 and Vp (90 %tile) = 3.2; and Ktrans (mean) = 3.5 and Ktrans (90 %tile) = 4.2. Patients with tumor progression (n = 24) had Vp (mean) = 5.3 and Vp (90 %tile) = 6.6; and Ktrans (mean) = 7.4 and Ktrans (90 %tile) = 9.1. Compared with tumor progression, pseudoprogression demonstrated lower Vp perfusion values (p = 0.0002) with a Vp (mean) cutoff <3.7 yielding 85% sensitivity and 79% specificity for pseudoprogression. Ktrans (mean) of >3.6 had a 69% sensitivity and 79% specificity for disease progression. DCE MRI shows lower plasma volume and time dependent leakage constant values in pseudoprogression than in tumor progression. A cut-off value with high sensitivity for pseudoprogression can be applied to aid in interpretation of DCE MRI.

  4. Enhancing Student Motivation and Learning within Adaptive Tutors

    ERIC Educational Resources Information Center

    Ostrow, Korinn S.

    2015-01-01

    My research is rooted in improving K-12 educational practice using motivational facets made possible through adaptive tutoring systems. In an attempt to isolate best practices within the science of learning, I conduct randomized controlled trials within ASSISTments, an online adaptive tutoring system that provides assistance and assessment to…

  5. Differentiation of solid pancreatic tumors by using dynamic contrast-enhanced MRI

    NASA Astrophysics Data System (ADS)

    Choi, Seung Joon; Kim, Hyung Sik; Park, Hyunjin

    2014-01-01

    Distinguishing among different solid pancreatic tumor types, pancreatic ductal adenocarcinomas, neuroendocrine tumors (NETs), and solid pseudopapillary tumors (SPTs) is important, as the treatment options are vastly different. This study compared characteristics of solid pancreatic tumors by using dynamic contrast enhanced magnetic resonance imaging (MRI). Fifty patients underwent MR imaging of pancreatic masses with a histopathology that was later confirmed as an adenocarcinoma (n = 27), a NET (n = 16), and a SPT (n = 7). For qualitative analysis, two reviewers evaluated the morphologic features of the tumors: locations, margins, shapes, contained products, pancreatic ductal dilatation, and grade of signal intensity (SI). For the quantitative analysis, all phases of the MR images were co-registered using proprietary image registration software; thus, a region of interest (ROI) defined on one phase could be re-applied in other phases. The following four ratios were considered: tumor-to-uninvolved pancreas SI ratio, percent SI change, tumor-touninvolved pancreas enhancement index, and arterial-to-delayed washout rate. The areas under the receiver operating characteristic (ROC) curves were assessed for the four ratios. Adenocarcinomas had ill-defined margins, irregular shapes, and ductal dilatation compared with NETs and SPTs (P < 0.001). The tumor-to-uninvolved pancreas ratio on all dynamic phases was significantly higher for NETs than for both adenocarcinomas and SPTs (P < 0.05). Percentage SI changes of pancreatic tumors on the pancreatic and the portal venous phases were significantly higher for NETs than for both adenocarcinomas and SPTs (P < 0.05). A significant difference between NETs and adenocarcinomas was also found with respect to the tumor-to-uninvolved pancreas enhancement index and arterial-to-delayed washout rate. The percentage SI changes in the pancreatic phase and the arterial-to-delayed washout rate best distinguished between adenocarcinomas and

  6. Contrast-enhanced ultrasound findings in a case of primary chest chondrosarcoma mimicking a porta hepatis mass.

    PubMed

    Liu, Jin-Ya; Zhou, Lu-Yao; Liang, Jin-Yu; Lu, Ming-De; Wang, Wei

    2015-04-01

    We report a case of a 32-year-old woman who presented with upper abdominal pain. The physical examination revealed a palpable hard mass with a well-demarcated lower margin. Laboratory tests indicated hepatitis B viral infection. Computed tomography scan with intravenous contrast depicted a huge well-demarcated heterogeneous mass at the porta hepatis with irregular peripheral rim enhancement. Contrast-enhanced ultrasound showed peripheral irregular hyper-enhancement in the artery phase and hypo-enhancement in the portal and late phases. The postoperative histopathologic examination confirmed the diagnosis of low-grade chondrosarcoma. This is the first report of contrast-enhanced ultrasound findings of chondrosarcoma. There is some differential diagnosis to be discussed.

  7. Feasibility and usefulness of using swallow contrast-enhanced ultrasound to diagnose Zenker's diverticulum: preliminary results.

    PubMed

    Cui, Xin-Wu; Ignee, Andre; Baum, Ulrich; Dietrich, Christoph F

    2015-04-01

    Zenker's diverticulum (ZD) may be misdiagnosed on conventional ultrasound as a thyroid nodule or other lesion. A barium esophagram is usually used to confirm the diagnosis; however, this procedure exposes the patient to radiation. The aim of this study was to evaluate the feasibility of using swallow contrast-enhanced ultrasound (swallow-CEUS) to diagnose ZD. Ten consecutive patients with ZD (7 men and 3 women, aged 67 ± 11 y) were included in the study. In 4 patients, ZD was incidentally found on head and neck ultrasound, and in 6 patients, ZD was suspected because of dysphagia. All lesions could be detected on conventional ultrasound before swallow-CEUS. Ten healthy volunteers (8 men and 2 women, aged 60 ± 12 y) were chosen as a control group. Written informed consent was obtained. With the patient in the sitting or upright position, conventional ultrasound was performed first to image the lesion, then the patient was asked to swallow ultrasound contrast agent (UCA) (2-4 drops of SonoVue diluted with about 200 mL of tap water). Transity of the contrast agent in the esophagus was imaged with CEUS. Retention of the UCA in the diverticulum was monitored for at least 3 min. All patients underwent a barium esophagram as the gold standard. Swallow-CEUS revealed that in all patients (100%), the UCA was transported from the pharynx to the esophagus while the patient swallowed. ZD appeared as a pouch-shaped structure at the posterior pharyngo-esophageal junction that retained UCA longer than 3 min. The barium esophagram confirmed the diagnosis of ZD in all patients. For the 10 volunteers, no abnormal structure (retaining UCA) was detected during or after swallowing of UCA. With the advantages of no radiation and bedside availability, swallow-CEUS may become a method of choice in confirmation of the diagnosis of ZD, especially when ZD is suspected on conventional ultrasound.

  8. Comparison of contrast enhancement methods using photon counting detector in spectral mammography

    NASA Astrophysics Data System (ADS)

    Kim, Hyemi; Park, Su-Jin; Jo, Byungdu; Kim, Dohyeon; Kim, Hee-Joung

    2016-03-01

    The photon counting detector with energy discrimination capabilities provides the spectral information and energy of each photon with single exposure. The energy-resolved photon counting detector makes it possible to improve the visualization of contrast agent by selecting the appropriate energy window. In this study, we simulated the photon counting spectral mammography system using a Monte Carlo method and compared three contrast enhancement methods (K-edge imaging, projection-based energy weighting imaging, and dual energy subtraction imaging). For the quantitative comparison, we used the homogeneous cylindrical breast phantom as a reference and the heterogeneous XCAT breast phantom. To evaluate the K-edge imaging methods, we obtained images by increasing the energy window width based on K-edge absorption energy of iodine. The iodine which has the K-edge discontinuity in the attenuation coefficient curve can be separated from the background. The projection-based energy weighting factor was defined as the difference in the transmissions between the contrast agent and the background. Each weighting factor as a function of photon energy was calculated and applied to the each energy bin. For the dual energy subtraction imaging, we acquired two images with below and above the iodine K-edge energy using single exposure. To suppress the breast tissue in high energy images, the weighting factor was applied as the ratio of the linear attenuation coefficients of the breast tissue at high and low energies. Our results demonstrated the CNR improvement of the K-edge imaging was the highest among the three methods. These imaging techniques based on the energy-resolved photon counting detector improved image quality with the spectral information.

  9. The use of contrast-enhanced ultrasound in blunt abdominal trauma: advantages and limitations.

    PubMed

    Pinto, Fabio; Miele, Vittorio; Scaglione, Mariano; Pinto, Antonio

    2014-09-01

    Computed tomography (CT) is the imaging method of choice in the assessment of multiple trauma patients. However, in patients who suffered from low-energy abdominal trauma, the use of CT is controversial, since the probability of injury is low and therefore most of the studies are normal. Thus, conventional US imaging has increasingly been employed as the initial imaging modality in the work-up of minor traumatic emergency condition. More recently, the introduction of a new contrast-enhanced ultrasound (CEUS) technique, using second-generation ultrasound contrast agents, has led to a notable increase in the diagnostic accuracy of US in many organs. Therefore, in trauma patients, following assessment with conventional US imaging, a CEUS exam can be performed, to provide a more reliable assessment of solid organ injuries. CEUS has the potential to detect active bleeding from a variety of traumatic origins. Similar to CT, active extravasation is considered when there is evidence of contrast agent collection with echogenicity similar to that of an adjacent vessel. On the other hand, at least some drawbacks have to be addressed, including operator competence and reduced panoramic view. Moreover, CEUS, like conventional US imaging, cannot depict some lesions, such as diaphragmatic ruptures, bowel, and mesenteric traumatic injuries. This technique represents a non-invasive and repeatable method that can be performed at patient's bedside and is therefore extremely helpful for the follow-up of solid organs traumas managed conservatively, especially in pediatric patients and women of fertile age. Moreover, it may reduce the number of CT scans and expedite patient discharge.

  10. Improved parameter extraction and classification for dynamic contrast enhanced MRI of prostate

    NASA Astrophysics Data System (ADS)

    Haq, Nandinee Fariah; Kozlowski, Piotr; Jones, Edward C.; Chang, Silvia D.; Goldenberg, S. Larry; Moradi, Mehdi

    2014-03-01

    Magnetic resonance imaging (MRI), particularly dynamic contrast enhanced (DCE) imaging, has shown great potential in prostate cancer diagnosis and prognosis. The time course of the DCE images provides measures of the contrast agent uptake kinetics. Also, using pharmacokinetic modelling, one can extract parameters from the DCE-MR images that characterize the tumor vascularization and can be used to detect cancer. A requirement for calculating the pharmacokinetic DCE parameters is estimating the Arterial Input Function (AIF). One needs an accurate segmentation of the cross section of the external femoral artery to obtain the AIF. In this work we report a semi-automatic method for segmentation of the cross section of the femoral artery, using circular Hough transform, in the sequence of DCE images. We also report a machine-learning framework to combine pharmacokinetic parameters with the model-free contrast agent uptake kinetic parameters extracted from the DCE time course into a nine-dimensional feature vector. This combination of features is used with random forest and with support vector machine classi cation for cancer detection. The MR data is obtained from patients prior to radical prostatectomy. After the surgery, wholemount histopathology analysis is performed and registered to the DCE-MR images as the diagnostic reference. We show that the use of a combination of pharmacokinetic parameters and the model-free empirical parameters extracted from the time course of DCE results in improved cancer detection compared to the use of each group of features separately. We also validate the proposed method for calculation of AIF based on comparison with the manual method.

  11. Conductivity image enhancement in MREIT using adaptively weighted spatial averaging filter

    PubMed Central

    2014-01-01

    Background In magnetic resonance electrical impedance tomography (MREIT), we reconstruct conductivity images using magnetic flux density data induced by externally injected currents. Since we extract magnetic flux density data from acquired MR phase images, the amount of measurement noise increases in regions of weak MR signals. Especially for local regions of MR signal void, there may occur excessive amounts of noise to deteriorate the quality of reconstructed conductivity images. In this paper, we propose a new conductivity image enhancement method as a postprocessing technique to improve the image quality. Methods Within a magnetic flux density image, the amount of noise varies depending on the position-dependent MR signal intensity. Using the MR magnitude image which is always available in MREIT, we estimate noise levels of measured magnetic flux density data in local regions. Based on the noise estimates, we adjust the window size and weights of a spatial averaging filter, which is applied to reconstructed conductivity images. Without relying on a partial differential equation, the new method is fast and can be easily implemented. Results Applying the novel conductivity image enhancement method to experimental data, we could improve the image quality to better distinguish local regions with different conductivity contrasts. From phantom experiments, the estimated conductivity values had 80% less variations inside regions of homogeneous objects. Reconstructed conductivity images from upper and lower abdominal regions of animals showed much less artifacts in local regions of weak MR signals. Conclusion We developed the fast and simple method to enhance the conductivity image quality by adaptively adjusting the weights and window size of the spatial averaging filter using MR magnitude images. Since the new method is implemented as a postprocessing step, we suggest adopting it without or with other preprocessing methods for application studies where conductivity

  12. Sex-based differences in the adaptive value of social behavior contrasted against morphology and environment.

    PubMed

    Vander Wal, E; Festa-Bianchet, M; Réale, D; Coltman, D W; Pelletier, F

    2015-03-01

    The adaptive nature of sociality has long been a central question in ecology and evolution. However, the relative importance of social behavior for fitness, compared to morphology and environment, remains largely unknown. We assessed the importance of sociality for fitness (lamb production and survival) in a population of mark6d bighorn sheep (Ovis canadensis) over 16 years (n = 1022 sheep-years). We constructed social networks from observations (n = 38,350) of group membership (n = 3150 groups). We then tested whether consistent individual differences in social behavior (centrality) exist and evaluated their relative importance compared to factors known to affect fitness: mass, age, parental effects, and population density. Sheep exhibited consistent individual differences in social centrality. Controlling for maternal carryover effects and age, the positive effect of centrality in a social network on adult female lamb production and survival was equal or greater than the effect of body mass or population density. Social centrality had less effect on male survival and no effect on adult male lamb production or lamb survival. Through its effect on lamb production and survival, sociality in fission-fusion animal societies may ultimately influence population dynamics equally or more than morphological or environmental effects. PMID:26236860

  13. Iterative development and the scope for plasticity: contrasts among trait categories in an adaptive radiation

    PubMed Central

    Foster, S A; Wund, M A; Graham, M A; Earley, R L; Gardiner, R; Kearns, T; Baker, J A

    2015-01-01

    Phenotypic plasticity can influence evolutionary change in a lineage, ranging from facilitation of population persistence in a novel environment to directing the patterns of evolutionary change. As the specific nature of plasticity can impact evolutionary consequences, it is essential to consider how plasticity is manifested if we are to understand the contribution of plasticity to phenotypic evolution. Most morphological traits are developmentally plastic, irreversible, and generally considered to be costly, at least when the resultant phenotype is mis-matched to the environment. At the other extreme, behavioral phenotypes are typically activational (modifiable on very short time scales), and not immediately costly as they are produced by constitutive neural networks. Although patterns of morphological and behavioral plasticity are often compared, patterns of plasticity of life history phenotypes are rarely considered. Here we review patterns of plasticity in these trait categories within and among populations, comprising the adaptive radiation of the threespine stickleback fish Gasterosteus aculeatus. We immediately found it necessary to consider the possibility of iterated development, the concept that behavioral and life history trajectories can be repeatedly reset on activational (usually behavior) or developmental (usually life history) time frames, offering fine tuning of the response to environmental context. Morphology in stickleback is primarily reset only in that developmental trajectories can be altered as environments change over the course of development. As anticipated, the boundaries between the trait categories are not clear and are likely to be linked by shared, underlying physiological and genetic systems. PMID:26243135

  14. Contrasting Patterns of Host Adaptation in Two Egg Parasitoids of the Pine Processionary Moth (Lepidoptera: Thaumetopoeidae).

    PubMed

    Ruschioni, Sara; Riolo, Paola; Isidoro, Nunzio; Romani, Roberto; Petrucco-Toffolo, Edoardo; Zovi, Daniel; Battisti, Andrea

    2015-06-01

    Adaptation of parasitoids to their phytophagous host is often mediated by environmental conditions and by the food plant of the phytophagous host. Therefore, the host food plant can indirectly affect the survival and fitness of parasitoids that also attack quiescent host stages, such as eggs, in which the resources available to the immature parasitoid stages are limited. Our aim was to investigate how two egg parasitoid species of the pine processionary moth, Thaumetopoea pityocampa (Denis & Schiffermüller), respond to variations in egg traits at the extremes of a west-to-east geographic gradient in northern Italy. We considered one specialist [Baryscapus servadeii (Domenichini)] and one generalist [Ooencyrtus pityocampae (Mercet)] parasitoid, which reproduce mainly by thelytokous parthenogenesis and are common throughout the whole range of this pest. The size and shell structure of the pine processionary moth eggs were studied under light microscopy and tested experimentally under controlled conditions. We can conclude that 1) the pine processionary moth egg shell thickness is inversely proportional to the parasitism performance; 2) the larger eggs from the pine processionary moth eastern population produce parasitoid females of a larger size, which have greater realized fecundity; 3) the generalist parasitoid performs successfully with either the "home" or "away" (i.e., from both extremes of the geographic gradient) pine processionary moth eggs, which is not the case for the specialist parasitoid. The implications of these responses in the regulation of phytophagous populations are numerous and should be considered in population dynamics studies and pest management programs.

  15. Contrast-enhanced spectral mammography with a photon-counting detector

    SciTech Connect

    Fredenberg, Erik; Hemmendorff, Magnus; Cederstroem, Bjoern; Aaslund, Magnus; Danielsson, Mats

    2010-05-15

    Purpose: Spectral imaging is a method in medical x-ray imaging to extract information about the object constituents by the material-specific energy dependence of x-ray attenuation. The authors have investigated a photon-counting spectral imaging system with two energy bins for contrast-enhanced mammography. System optimization and the potential benefit compared to conventional non-energy-resolved absorption imaging was studied. Methods: A framework for system characterization was set up that included quantum and anatomical noise and a theoretical model of the system was benchmarked to phantom measurements. Results: Optimal combination of the energy-resolved images corresponded approximately to minimization of the anatomical noise, which is commonly referred to as energy subtraction. In that case, an ideal-observer detectability index could be improved close to 50% compared to absorption imaging in the phantom study. Optimization with respect to the signal-to-quantum-noise ratio, commonly referred to as energy weighting, yielded only a minute improvement. In a simulation of a clinically more realistic case, spectral imaging was predicted to perform approximately 30% better than absorption imaging for an average glandularity breast with an average level of anatomical noise. For dense breast tissue and a high level of anatomical noise, however, a rise in detectability by a factor of 6 was predicted. Another {approx}70%-90% improvement was found to be within reach for an optimized system. Conclusions: Contrast-enhanced spectral mammography is feasible and beneficial with the current system, and there is room for additional improvements. Inclusion of anatomical noise is essential for optimizing spectral imaging systems.

  16. Comparison Between Perfusion Computed Tomography and Dynamic Contrast-Enhanced Magnetic Resonance Imaging in Rectal Cancer

    SciTech Connect

    Kierkels, Roel G.J.; Backes, Walter H.; Janssen, Marco H.M.; Buijsen, Jeroen; Beets-Tan, Regina G.H.; Lambin, Philippe; Lammering, Guido; Oellers, Michel C.; Aerts, Hugo J.W.L.

    2010-06-01

    Purpose: To compare pretreatment scans with perfusion computed tomography (pCT) vs. dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in rectal tumors. Methods and Materials: Nineteen patients diagnosed with rectal cancer were included in this prospective study. All patients underwent both pCT and DCE-MRI. Imaging was performed on a dedicated 40-slice CT-positron emission tomography system and a 3-T MRI system. Dynamic contrast enhancement was measured in tumor tissue and the external iliac artery. Tumor perfusion was quantified in terms of pharmacokinetic parameters: transfer constant K{sup trans}, fractional extravascular-extracellular space v{sub e}, and fractional plasma volume v{sub p}. Pharmacokinetic parameter values and their heterogeneity (by 80% quantile value) were compared between pCT and DCE-MRI. Results: Tumor K{sup trans} values correlated significantly for the voxel-by-voxel-derived median (Kendall's tau correlation, tau = 0.81, p < 0.001) and 80% quantile (tau = 0.54, p = 0.04), as well as for the averaged uptake (tau = 0.58, p = 0.03). However, no significant correlations were found for v{sub e} and v{sub p} derived from the voxel-by-voxel-derived median and 80% quantile and derived from the averaged uptake curves. Conclusions: This study demonstrated for the first time that pCT provides K{sup trans} values comparable to those of DCE-MRI. However, no correlation was found for the v{sub e} and v{sub p} parameters between CT and MRI. Computed tomography can serve as an alternative modality to MRI for the in vivo evaluation of tumor angiogenesis in terms of the transfer constant K{sup trans}.

  17. A scatter correction method for contrast-enhanced dual-energy digital breast tomosynthesis

    PubMed Central

    Lu, Yihuan; Peng, Boyu; Lau, Beverly A.; Hu, Yue-Houng; Scaduto, David A.; Zhao, Wei; Gindi, Gene

    2015-01-01

    Contrast-enhanced dual energy digital breast tomosynthesis (CE-DE-DBT) is designed to image iodinated masses while suppressing breast anatomical background. Scatter is a problem, especially for high energy acquisition, in that it causes severe cupping artifact and iodine quantitation errors. We propose a patient specific scatter correction (SC) algorithm for CE-DE-DBT. The empirical algorithm works by interpolating scatter data outside the breast shadow into an estimate within the breast shadow. The interpolated estimate is further improved by operations that use an easily obtainable (from phantoms) table of scatter-to-primary-ratios (SPR) - a single SPR value for each breast thickness and acquisition angle. We validated our SC algorithm for two breast emulating phantoms by comparing SPR from our SC algorithm to that measured using a beam-passing pinhole array plate. The error in our SC computed SPR, averaged over acquisition angle and image location, was about 5%, with slightly worse errors for thicker phantoms. The SC projection data, reconstructed using OS-SART, showed a large degree of decupping. We also observed that SC removed the dependence of iodine quantitation on phantom thickness. We applied the SC algorithm to a CE-DE-mammographic patient image with a biopsy confirmed tumor at the breast periphery. In the image without SC, the contrast enhanced tumor was masked by the cupping artifact. With our SC, the tumor was easily visible. An interpolation-based SC was proposed by (Siewerdsen et al., 2006) for cone-beam CT (CBCT), but our algorithm and application differ in several respects. Other relevant SC techniques include Monte-Carlo and convolution-based methods for CBCT, storage of a precomputed library of scatter maps for DBT, and patient acquisition with a beam-passing pinhole array for breast CT. Our SC algorithm can be accomplished in clinically acceptable times, requires no additional imaging hardware or extra patient dose and is easily transportable

  18. A scatter correction method for contrast-enhanced dual-energy digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Lu, Yihuan; Peng, Boyu; Lau, Beverly A.; Hu, Yue-Houng; Scaduto, David A.; Zhao, Wei; Gindi, Gene

    2015-08-01

    Contrast-enhanced dual energy digital breast tomosynthesis (CE-DE-DBT) is designed to image iodinated masses while suppressing breast anatomical background. Scatter is a problem, especially for high energy acquisition, in that it causes severe cupping artifact and iodine quantitation errors. We propose a patient specific scatter correction (SC) algorithm for CE-DE-DBT. The empirical algorithm works by interpolating scatter data outside the breast shadow into an estimate within the breast shadow. The interpolated estimate is further improved by operations that use an easily obtainable (from phantoms) table of scatter-to-primary-ratios (SPR)—a single SPR value for each breast thickness and acquisition angle. We validated our SC algorithm for two breast emulating phantoms by comparing SPR from our SC algorithm to that measured using a beam-passing pinhole array plate. The error in our SC computed SPR, averaged over acquisition angle and image location, was about 5%, with slightly worse errors for thicker phantoms. The SC projection data, reconstructed using OS-SART, showed a large degree of decupping. We also observed that SC removed the dependence of iodine quantitation on phantom thickness. We applied the SC algorithm to a CE-DE-mammographic patient image with a biopsy confirmed tumor at the breast periphery. In the image without SC, the contrast enhanced tumor was masked by the cupping artifact. With our SC, the tumor was easily visible. An interpolation-based SC was proposed by (Siewerdsen et al 2006 Med. Phys. 33 187-97) for cone-beam CT (CBCT), but our algorithm and application differ in several respects. Other relevant SC techniques include Monte-Carlo and convolution-based methods for CBCT, storage of a precomputed library of scatter maps for DBT, and patient acquisition with a beam-passing pinhole array for breast CT. Our SC algorithm can be accomplished in clinically acceptable times, requires no additional imaging hardware or extra patient dose and is

  19. Bisphosphonate-functionalized gold nanoparticles for contrast-enhanced X-ray detection of breast microcalcifications.

    PubMed

    Cole, Lisa E; Vargo-Gogola, Tracy; Roeder, Ryan K

    2014-02-01

    Microcalcifications are one of the most common abnormalities detected by mammography for the diagnosis of breast cancer. However, the detection of microcalcifications and correct diagnosis of breast cancer are limited by the sensitivity and specificity of mammography. Therefore, the objective of this study was to investigate the potential of bisphosphonate-functionalized gold nanoparticles (BP-Au NPs) for contrast-enhanced radiographic detection of breast microcalcifications using two models of breast microcalcifications, which allowed for precise control over levels of hydroxyapatite (HA) mineral within a low attenuating matrix. First, an in vitro imaging phantom was prepared with varying concentrations of HA uniformly dispersed in an agarose hydrogel. The X-ray attenuation of HA-agarose compositions labeled by BP-Au NPs was increased by up to 26 HU compared to unlabeled compositions for HA concentrations ranging from 1 to 10 mg/mL. Second, an ex vivo tissue model was developed to more closely mimic the heterogeneity of breast tissue by injecting varying concentrations of HA in a Matrigel carrier into murine mammary glands. The X-ray attenuation of HA-Matrigel compositions labeled by BP-Au NPs was increased by up to 289 HU compared to unlabeled compositions for HA concentrations ranging from 0.5 to 25 mg/mL, which included an HA concentration (0.5 mg/mL) that was otherwise undetectable by micro-computed tomography. Cumulatively, both models demonstrated the ability of BP-Au NPs to enhance contrast for radiographic detection of microcalcifications, including at a clinically-relevant imaging resolution. Therefore, BP-Au NPs may have potential to improve clinical detection of breast microcalcifications by mammography. PMID:24360718

  20. Bisphosphonate-Functionalized Gold Nanoparticles for Contrast-Enhanced X-Ray Detection of Breast Microcalcifications

    PubMed Central

    Cole, Lisa E.; Vargo-Gogola, Tracy; Roeder, Ryan K.

    2014-01-01

    Microcalcifications are one of the most common abnormalities detected by mammography for the diagnosis of breast cancer. However, the detection of microcalcifications and correct diagnosis of breast cancer are limited by the sensitivity and specificity of mammography. Therefore, the objective of this study was to investigate the potential of bisphosphonate-functionalized gold nanoparticles (BP-Au NPs) for contrast-enhanced radiographic detection of breast microcalcifications using two models of breast microcalcifications which allowed for precise control over levels of hydroxyapatite (HA) mineral within a low attenuating matrix. First, an in vitro imaging phantom was prepared with varying concentrations of HA uniformly dispersed in an agarose hydrogel. The X-ray attenuation of HA-agarose compositions labeled by BP-Au NPs was increased by up to 26 HU compared to unlabeled compositions for HA concentrations ranging from 1–10 mg/mL. Second, an ex vivo tissue model was developed to more closely mimic the heterogeneity of breast tissue by injecting varying concentrations of HA in a Matrigel carrier into murine mammary glands. The X-ray attenuation of HA-Matrigel compositions labeled by BP-Au NPs was increased by up to 289 HU compared to unlabeled compositions for HA concentrations ranging from 0.5–25 mg/mL, which included an HA concentration (0.5 mg/mL) that was otherwise undetectable by micro-computed tomography. Cumulatively, both models demonstrated the ability of BP-Au NPs to enhance contrast for radiographic detection of microcalcifications, including at a clinically-relevant imaging resolution. Therefore, BP-Au NPs may have potential to improve clinical detection of breast microcalcifications by mammography. PMID:24360718

  1. Contrast enhanced diffusion NMR: quantifying impurities in block copolymers for DSA

    NASA Astrophysics Data System (ADS)

    Wojtecki, Rudy; Porath, Ellie; Vora, Ankit; Nelson, Alshakim; Sanders, Daniel

    2016-03-01

    Block-copolymers (BCPs) offer the potential to meet the demands of next generation lithographic materials as they can self-assemble into scalable and tailorable nanometer scale patterns. In order for these materials to find wide spread adoption many challenges remain, including reproducible thin film morphology, for which the purity of block copolymers is critical. One of the sources of impurities are reaction conditions used to synthesize block copolymers that may result in the formation of homopolymer as a side product, which can impact the quality and the morphology of self-assembled features. Detection and characterization of these homopolymer impurities can be challenging by traditional methods of polymer characterization. We will discuss an alternate NMR-based method for the detection of homopolymer impurities in block copolymers - contrast enhanced diffusion ordered spectroscopy (CEDOSY). This experimental technique measures the diffusion coefficient of polymeric materials in the solution allowing for the `virtual' or spectroscopic separation of BCPs that contain homopolymer impurities. Furthermore, the contrast between the diffusion coefficient of mixtures containing BCPs and homopolymer impurities can be enhanced by taking advantage of the chemical mismatch of the two blocks to effectively increase the size of the BCP (and diffusion coefficient) through the formation of micelles using a cosolvent, while the size and diffusion coefficient of homopolymer impurities remain unchanged. This enables the spectroscopic separation of even small amounts of homopolymer impurities that are similar in size to BCPs. Herein, we present the results using the CEDOSY technique with both first generation BCP system, poly(styrene)-b-poly(methyl methacrylate), as well as a second generation high-χ system.

  2. Imaging of myocardial infarction using carbon nanotube micro-computed tomography and delayed contrast enhancement

    NASA Astrophysics Data System (ADS)

    Burk, Laurel M.; Wang, Kohan; Kang, Eunice; Rojas, Mauricio; Willis, Monte; Lee, Yueh Z.; Lu, Jianping; Zhou, Otto

    2011-03-01

    We demonstrate the application of our cardiac- and respiratory-gated carbon nanotube (CNT) micro-CT system by evaluating murine myocardial infarction models with a delayed contrast enhancement technique. Myocardial infarction was induced in 8 wild-type male mice. The ischemia reperfusion model was achieved by surgical occlusion of the LAD artery for 30 minutes followed by 24 hours of reperfusion. Free-breathing subjects were anesthetized with isoflurane during imaging. Respiratory and cardiac signals were monitored externally to gate the scan. Micro-CT data was obtained at 50kV, 3mA cathode current for 15ms per projection. All images were acquired during end exhalation at either 0msec or 55msec after the R-wave (diastole or systole, respectively). Following administration of Omnipaque 300mgI/mL at 0.1ml/5g, images were obtained at 0msec after the R-wave. Fenestra VC was then administered at a 0.1ml/5g dose, followed by images 0 and 55msec after the R-wave. Hearts were then harvested, sliced 1mm thick and stained with TTC. All animals survived surgery and imaging; all demonstrated obvious delayed contrast enhancement in the left ventricular wall in Omnipaque images. Fenestra VC revealed cardiac functional changes quantified by low ejection fractions. All subjects demonstrated areas of myocardial infarct in the LAD distribution on both TTC staining and micro-CT imaging. CNT enabled gated cardiac micro-CT imaging demonstrates the ability to consistently identify areas of myocardial infarct in mice, providing a powerful tool for the study of cardiovascular biology. Further work is ongoing to streamline the imaging protocol and perform more quantitative analysis of the images.

  3. Enhancement of BOLD-contrast sensitivity by single-shot multi-echo functional MR imaging.

    PubMed

    Posse, S; Wiese, S; Gembris, D; Mathiak, K; Kessler, C; Grosse-Ruyken, M L; Elghahwagi, B; Richards, T; Dager, S R; Kiselev, V G

    1999-07-01

    Improved data acquisition and processing strategies for blood oxygenation level-dependent (BOLD)-contrast functional magnetic resonance imaging (fMRI), which enhance the functional contrast-to-noise ratio (CNR) by sampling multiple echo times in a single shot, are described. The dependence of the CNR on T2*, the image encoding time, and the number of sampled echo times are investigated for exponential fitting, echo summation, weighted echo summation, and averaging of correlation maps obtained at different echo times. The method is validated in vivo using visual stimulation and turbo proton echoplanar spectroscopic imaging (turbo-PEPSI), a new single-shot multi-slice MR spectroscopic imaging technique, which acquires up to 12 consecutive echoplanar images with echo times ranging from 12 to 213 msec. Quantitative T2*-mapping significantly increases the measured extent of activation and the mean correlation coefficient compared with conventional echoplanar imaging. The sensitivity gain with echo summation, which is computationally efficient provides similar sensitivity as fitting. For all data processing methods sensitivity is optimum when echo times up to 3.2 T2* are sampled. This methodology has implications for comparing functional sensitivity at different magnetic field strengths and between brain regions with different magnetic field inhomogeneities.

  4. Pitfalls of contrast-enhanced ultrasound (CEUS) in the diagnosis of splenic sarcoidosis.

    PubMed

    Tana, C; Iannetti, G; D'Alessandro, P; Tana, M; Mezzetti, A; Schiavone, C

    2013-01-01

    By observing the real-time behavior of focal liver lesions at three vascular phases (arterial, portal-venous, and late), contrast-enhanced ultrasound (CEUS) has been successfully applied to differentiate benign from malignant hepatic nodules. In recent years, numerous studies highlighted the usefulness of CEUS also for other applications such as abdominal trauma, renal, pancreatic, thyroid, and inflammatory bowel diseases, supporting its role even in differentiating benign from malignant splenic nodules. Therefore, the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) recently updated the guidelines for the use of ultrasound contrast agents in clinical practice, pointing out the indication to characterize splenic parenchymal inhomogeneity or suspected lesions found on conventional ultrasound (BUS). We describe the case of a patient with a history of colon cancer and finding, at BUS and CEUS, of hypoechoic lesions with a highly suggestive pattern for metastases, subsequently histologically proved to be splenic localizations of a benign and multisystemic granulomatous disease such as sarcoidosis. We therefore reviewed the current literature focusing on the role of CEUS in differentiating benign from malignant splenic lesions, emphasizing on the lack of data and numerical shortage of sarcoidosis derived-lesions in the available studies. We conclude that sarcoidosis remains a diagnosis of exclusion and new studies are needed before defining precise indications of CEUS in these patients.

  5. The effect of contrast-enhanced ultrasound on the kidneys in eight cats.

    PubMed

    Leinonen, Merja R; Raekallio, Marja R; Vainio, Outi M; Sankari, Satu; O'Brien, Robert T

    2011-10-01

    Contrast-enhanced ultrasound (CEUS) of the left kidney was performed on eight non-anesthetized, young, purpose bred, domestic shorthaired cats. Each cat underwent a physical examination before and 4h and 48h after CEUS. Complete blood count (CBC), serum biochemical analysis, urinalysis, including evaluation of the enzymatic activities of urinary N-acetyl-β-d-glucosaminidase (NAG) and gamma-glutamyl transferase (GGT), were also performed. No changes were observed in CBC or serum biochemical analyses, with the exception of a decrease in blood urea concentration at 48h post-contrast ultrasound. A small elevation in NAG (U/g creatinine) was observed with a mean (SD) increase from 0.53 (0.35) to 1.43 (0.59) U/g creatinine. The magnitude of the rise was less than the circadian variation reported earlier for healthy cats. These results suggest that CEUS can be safely used to assess kidney perfusion in cats. The changes observed in laboratory values after CEUS did not appear to be related to detrimental effects on the kidneys.

  6. Automatic indicator dilution curve extraction in dynamic-contrast enhanced imaging using spectral clustering

    NASA Astrophysics Data System (ADS)

    Saporito, Salvatore; Herold, Ingeborg HF; Houthuizen, Patrick; van den Bosch, Harrie CM; Korsten, Hendrikus HM; van Assen, Hans C.; Mischi, Massimo

    2015-07-01

    Indicator dilution theory provides a framework for the measurement of several cardiovascular parameters. Recently, dynamic imaging and contrast agents have been proposed to apply the method in a minimally invasive way. However, the use of contrast-enhanced sequences requires the definition of regions of interest (ROIs) in the dynamic image series; a time-consuming and operator dependent task, commonly performed manually. In this work, we propose a method for the automatic extraction of indicator dilution curves, exploiting the time domain correlation between pixels belonging to the same region. Individual time intensity curves were projected into a low dimensional subspace using principal component analysis; subsequently, clustering was performed to identify the different ROIs. The method was assessed on clinically available DCE-MRI and DCE-US recordings, comparing the derived IDCs with those obtained manually. The robustness to noise of the proposed approach was shown on simulated data. The tracer kinetic parameters derived on real images were in agreement with those obtained from manual annotation. The presented method is a clinically useful preprocessing step prior to further ROI-based cardiac quantifications.

  7. DCE@urLAB: a dynamic contrast-enhanced MRI pharmacokinetic analysis tool for preclinical data

    PubMed Central

    2013-01-01

    Background DCE@urLAB is a software application for analysis of dynamic contrast-enhanced magnetic resonance imaging data (DCE-MRI). The tool incorporates a friendly graphical user interface (GUI) to interactively select and analyze a region of interest (ROI) within the image set, taking into account the tissue concentration of the contrast agent (CA) and its effect on pixel intensity. Results Pixel-wise model-based quantitative parameters are estimated by fitting DCE-MRI data to several pharmacokinetic models using the Levenberg-Marquardt algorithm (LMA). DCE@urLAB also includes the semi-quantitative parametric and heuristic analysis approaches commonly used in practice. This software application has been programmed in the Interactive Data Language (IDL) and tested both with publicly available simulated data and preclinical studies from tumor-bearing mouse brains. Conclusions A user-friendly solution for applying pharmacokinetic and non-quantitative analysis DCE-MRI in preclinical studies has been implemented and tested. The proposed tool has been specially designed for easy selection of multi-pixel ROIs. A public release of DCE@urLAB, together with the open source code and sample datasets, is available at http://www.die.upm.es/im/archives/DCEurLAB/. PMID:24180558

  8. Enhancement of BOLD-contrast sensitivity by single-shot multi-echo functional MR imaging.

    PubMed

    Posse, S; Wiese, S; Gembris, D; Mathiak, K; Kessler, C; Grosse-Ruyken, M L; Elghahwagi, B; Richards, T; Dager, S R; Kiselev, V G

    1999-07-01

    Improved data acquisition and processing strategies for blood oxygenation level-dependent (BOLD)-contrast functional magnetic resonance imaging (fMRI), which enhance the functional contrast-to-noise ratio (CNR) by sampling multiple echo times in a single shot, are described. The dependence of the CNR on T2*, the image encoding time, and the number of sampled echo times are investigated for exponential fitting, echo summation, weighted echo summation, and averaging of correlation maps obtained at different echo times. The method is validated in vivo using visual stimulation and turbo proton echoplanar spectroscopic imaging (turbo-PEPSI), a new single-shot multi-slice MR spectroscopic imaging technique, which acquires up to 12 consecutive echoplanar images with echo times ranging from 12 to 213 msec. Quantitative T2*-mapping significantly increases the measured extent of activation and the mean correlation coefficient compared with conventional echoplanar imaging. The sensitivity gain with echo summation, which is computationally efficient provides similar sensitivity as fitting. For all data processing methods sensitivity is optimum when echo times up to 3.2 T2* are sampled. This methodology has implications for comparing functional sensitivity at different magnetic field strengths and between brain regions with different magnetic field inhomogeneities. PMID:10398954

  9. Contrast-enhanced imaging of SPIO-labeled platelets using magnetomotive ultrasound

    NASA Astrophysics Data System (ADS)

    Pope, Ava G.; Wu, Gongting; McWhorter, Frances Y.; Merricks, Elizabeth P.; Nichols, Timothy C.; Czernuszewicz, Tomasz J.; Gallippi, Caterina M.; Oldenburg, Amy L.

    2013-10-01

    The ability to image platelets in vivo can provide insight into blood clotting processes and coagulopathies, and aid in identifying sites of vascular endothelial damage related to trauma or cardiovascular disease. Toward this end, we have developed a magnetomotive ultrasound (MMUS) system that provides contrast-enhanced imaging of superparamagnetic iron oxide (SPIO) labeled platelets via magnetically-induced vibration. Platelets are a promising platform for functional imaging contrast because they readily take up SPIOs and are easily harvested from blood. Here we report a novel MMUS system that accommodates an arbitrarily thick sample while maintaining portability. We employed a frequency- and phase-locked motion detection algorithm based on bandpass filtering of the differential RF phase, which allows for the detection of sub-resolution vibration amplitudes on the order of several nanometers. We then demonstrated MMUS in homogenous tissue phantoms at SPIO concentrations as low as 0.09 mg ml-1 Fe (p < 0.0001, n = 6, t-test). Finally, we showed that our system is capable of three-dimensional imaging of a 185 µL simulated clot containing SPIO-platelets. This highlights the potential utility for non-invasive imaging of platelet-rich clots, which would constitute a fundamental advance in technology for the study of hemostasis and detection of clinically relevant thrombi.

  10. Semi-quantitative assessment of pulmonary perfusion in children using dynamic contrast-enhanced MRI

    NASA Astrophysics Data System (ADS)

    Fetita, Catalin; Thong, William E.; Ou, Phalla

    2013-03-01

    This paper addresses the study of semi-quantitative assessment of pulmonary perfusion acquired from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in a study population mainly composed of children with pulmonary malformations. The automatic analysis approach proposed is based on the indicator-dilution theory introduced in 1954. First, a robust method is developed to segment the pulmonary artery and the lungs from anatomical MRI data, exploiting 2D and 3D mathematical morphology operators. Second, the time-dependent contrast signal of the lung regions is deconvolved by the arterial input function for the assessment of the local hemodynamic system parameters, ie. mean transit time, pulmonary blood volume and pulmonary blood flow. The discrete deconvolution method implements here a truncated singular value decomposition (tSVD) method. Parametric images for the entire lungs are generated as additional elements for diagnosis and quantitative follow-up. The preliminary results attest the feasibility of perfusion quantification in pulmonary DCE-MRI and open an interesting alternative to scintigraphy for this type of evaluation, to be considered at least as a preliminary decision in the diagnostic due to the large availability of the technique and to the non-invasive aspects.

  11. The Value of Contrast-Enhanced Ultrasound in the Diagnosis of Cesarean Scar Pregnancy.

    PubMed

    Xiong, Xi; Yan, Ping; Gao, Chunyan; Sun, Qiulei; Xu, Fenglian

    2016-01-01

    Objective. To evaluate the value of contrast-enhanced ultrasound (CEUS) in the cesarean scar pregnancy (CSP). Methods. Clinical data from 92 patients with lower uterine segment pregnancy, who underwent conventional ultrasound and CEUS examination in the Department of Obstetrics and Gynecology, were collected by Xinqiao Hospital Third Military Medical University from March 2014 to March 2015. The parameters of ultrasound contrast time-intensity curve (TIC), including arrival time, time to peak, time from peak to one half, basic intensity, peak intensity, and wash-in slope, were analyzed. Results. Of the 92 cases of patients with pregnancy in the lower uterine segment, 52 cases were CSP, and 40 cases were intrauterine pregnancy. CEUS was significantly better than conventional ultrasound in terms of sensitivity, negative predictive value, Youden index, and diagnostic accuracy (P < 0.05). There was no significant difference in specificity and positive predictive value (P > 0.05). Conclusion. CEUS has a higher accuracy than conventional ultrasound in diagnosis of CSP. PMID:27340659

  12. Sonographic imaging of extra-testicular focal lesions: comparison of grey-scale, colour Doppler and contrast-enhanced ultrasound.

    PubMed

    Rafailidis, Vasileios; Robbie, Hasti; Konstantatou, Eleni; Huang, Dean Y; Deganello, Annamaria; Sellars, Maria E; Cantisani, Vito; Isidori, Andrea M; Sidhu, Paul S

    2016-02-01

    Extra-testicular lesions are usually benign but present with nonspecific grey-scale sonography findings. This study assesses conventional sonographic characteristics in the differentiation of extra-testicular tumoural from inflammatory lesions and whether contrast-enhanced ultrasound has a role. A retrospective database analysis was performed. All patients were examined by experienced sonographers employing standard techniques combining grey-scale, colour Doppler sonography and contrast-enhanced ultrasound. Features recorded were: clinical symptoms, size, location, echogenicity, colour Doppler sonography and contrast-enhanced ultrasound enhancement. Vascularity on colour Doppler sonography and contrast-enhanced ultrasound was graded and compared. The lesions were classified as tumoural or inflammatory. The Chi-square test was used to analyse the sonographic patterns and kappa coefficient to measure the agreement between colour Doppler sonography and contrast-enhanced ultrasound. A total of 30 lesions were reviewed (median diameter 12 mm, range 5-80 mm, median age 52 years, range 18-86 years), including 13/30 tumoural and 17/30 inflammatory lesions. Lesions were hypoechoic (n = 12), isoechoic (n = 6), hyperechoic (n = 2) or mixed (n = 10). Grey-scale characteristics of tumoural vs. inflammatory lesions differed significantly (P = 0.026). On colour Doppler sonography, lesions had no vessels (n = 16), 2-3 vessels (n = 10) and ≥4 vessels (n = 4). On contrast-enhanced ultrasound, lesions showed no vascularity (n = 17), perfusion similar to testis (n = 7) and higher (n = 6). All abscesses identified (n = 9) showed no vascularity on both colour Doppler sonography and contrast-enhanced ultrasound. There was good agreement between these techniques in evaluating vascularity (κ = 0.719) and no significant difference between colour Doppler sonography and contrast-enhanced ultrasound of tumoural vs. inflammatory lesions

  13. Contrast-enhanced microCT (EPIC-µCT) ex vivo applied to the mouse and human jaw joint

    PubMed Central

    Mulder, L; Lin, A S; Langenbach, G E J; Koolstra, J H; Guldberg, R E; Everts, V

    2014-01-01

    Objectives: The temporomandibular joint (TMJ) is susceptive to the development of osteoarthritis (OA). More detailed knowledge of its development is essential to improve our insight into TMJ-OA. It is imperative to have a standardized reliable three-dimensional (3D) imaging method that allows for detailed assessment of both bone and cartilage in healthy and diseased joints. We aimed to determine the applicability of a contrast-enhanced microCT (µCT) technique for ex vivo research of mouse and human TMJs. Methods: Equilibrium partitioning of an ionic contrast agent via µCT (EPIC-µCT) was previously applied for cartilage assessment in the knee joint. The method was ex vivo, applied to the mouse TMJ and adapted for the human TMJ. Results: EPIC-µCT (30-min immersion time) was applied to mouse mandibular condyles, and 3D imaging revealed an average cartilage thickness of 110 ± 16 µm. These measurements via EPIC-µCT were similar to the histomorphometric measures (113 ± 19 µm). For human healthy OA-affected TMJ samples, the protocol was adjusted to an immersion time of 1 h. 3D imaging revealed a significant thicker cartilage layer in joints with early signs of OA compared with healthy joints (414.2 ± 122.6 and 239.7 ± 50.5 µm, respectively). A subsequent significant thinner layer was found in human joints with late signs of OA (197.4 ± 159.7 µm). Conclusions: The EPIC-µCT technique is effective for the ex vivo assessment of 3D cartilage morphology in the mouse as well as human TMJ and allows bone–cartilage interaction research in TMJ-OA. PMID:24353248

  14. Adaptation to background light enables contrast coding at rod bipolar cell synapses.

    PubMed

    Ke, Jiang-Bin; Wang, Yanbin V; Borghuis, Bart G; Cembrowski, Mark S; Riecke, Hermann; Kath, William L; Demb, Jonathan B; Singer, Joshua H

    2014-01-22

    Rod photoreceptors contribute to vision over an ∼ 6-log-unit range of light intensities. The wide dynamic range of rod vision is thought to depend upon light intensity-dependent switching between two parallel pathways linking rods to ganglion cells: a rod → rod bipolar (RB) cell pathway that operates at dim backgrounds and a rod → cone → cone bipolar cell pathway that operates at brighter backgrounds. We evaluated this conventional model of rod vision by recording rod-mediated light responses from ganglion and AII amacrine cells and by recording RB-mediated synaptic currents from AII amacrine cells in mouse retina. Contrary to the conventional model, we found that the RB pathway functioned at backgrounds sufficient to activate the rod → cone pathway. As background light intensity increased, the RB's role changed from encoding the absorption of single photons to encoding contrast modulations around mean luminance. This transition is explained by the intrinsic dynamics of transmission from RB synapses.

  15. Adaptation to background light enables contrast coding at rod bipolar cell synapses

    PubMed Central

    Ke, Jiang-Bin; Wang, Yanbin V.; Borghuis, Bart G.; Cembrowski, Mark S.; Riecke, Hermann; Kath, William L.; Demb, Jonathan B.; Singer, Joshua H.

    2013-01-01

    SUMMARY Rod photoreceptors contribute to vision over a ~6 log-unit range of light intensities. The wide dy