WorldWideScience

Sample records for thermal noise imaging

  1. Comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging

    International Nuclear Information System (INIS)

    O'Sullivan, Malcolm N.; Chan, Kam Wai Clifford; Boyd, Robert W.

    2010-01-01

    We present a theoretical comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging. We first calculate the signal-to-noise ratio of each process in terms of its controllable experimental conditions. We show that a key distinction is that a thermal ghost image always resides on top of a large background; the fluctuations in this background constitutes an intrinsic noise source for thermal ghost imaging. In contrast, there is a negligible intrinsic background to a quantum ghost image. However, for practical reasons involving achievable illumination levels, acquisition times for thermal ghost images are often much shorter than those for quantum ghost images. We provide quantitative predictions for the conditions under which each process provides superior performance. Our conclusion is that each process can provide useful functionality, although under complementary conditions.

  2. Noise Gating Solar Images

    Science.gov (United States)

    DeForest, Craig; Seaton, Daniel B.; Darnell, John A.

    2017-08-01

    I present and demonstrate a new, general purpose post-processing technique, "3D noise gating", that can reduce image noise by an order of magnitude or more without effective loss of spatial or temporal resolution in typical solar applications.Nearly all scientific images are, ultimately, limited by noise. Noise can be direct Poisson "shot noise" from photon counting effects, or introduced by other means such as detector read noise. Noise is typically represented as a random variable (perhaps with location- or image-dependent characteristics) that is sampled once per pixel or once per resolution element of an image sequence. Noise limits many aspects of image analysis, including photometry, spatiotemporal resolution, feature identification, morphology extraction, and background modeling and separation.Identifying and separating noise from image signal is difficult. The common practice of blurring in space and/or time works because most image "signal" is concentrated in the low Fourier components of an image, while noise is evenly distributed. Blurring in space and/or time attenuates the high spatial and temporal frequencies, reducing noise at the expense of also attenuating image detail. Noise-gating exploits the same property -- "coherence" -- that we use to identify features in images, to separate image features from noise.Processing image sequences through 3-D noise gating results in spectacular (more than 10x) improvements in signal-to-noise ratio, while not blurring bright, resolved features in either space or time. This improves most types of image analysis, including feature identification, time sequence extraction, absolute and relative photometry (including differential emission measure analysis), feature tracking, computer vision, correlation tracking, background modeling, cross-scale analysis, visual display/presentation, and image compression.I will introduce noise gating, describe the method, and show examples from several instruments (including SDO

  3. THE EFFECT OF IMAGE ENHANCEMENT METHODS DURING FEATURE DETECTION AND MATCHING OF THERMAL IMAGES

    Directory of Open Access Journals (Sweden)

    O. Akcay

    2017-05-01

    Full Text Available A successful image matching is essential to provide an automatic photogrammetric process accurately. Feature detection, extraction and matching algorithms have performed on the high resolution images perfectly. However, images of cameras, which are equipped with low-resolution thermal sensors are problematic with the current algorithms. In this paper, some digital image processing techniques were applied to the low-resolution images taken with Optris PI 450 382 x 288 pixel optical resolution lightweight thermal camera to increase extraction and matching performance. Image enhancement methods that adjust low quality digital thermal images, were used to produce more suitable images for detection and extraction. Three main digital image process techniques: histogram equalization, high pass and low pass filters were considered to increase the signal-to-noise ratio, sharpen image, remove noise, respectively. Later on, the pre-processed images were evaluated using current image detection and feature extraction methods Maximally Stable Extremal Regions (MSER and Speeded Up Robust Features (SURF algorithms. Obtained results showed that some enhancement methods increased number of extracted features and decreased blunder errors during image matching. Consequently, the effects of different pre-process techniques were compared in the paper.

  4. Eliminating thermal violin spikes from LIGO noise

    Energy Technology Data Exchange (ETDEWEB)

    Santamore, D. H.; Levin, Yuri

    2001-08-15

    We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally induced motion of a small portion of (a 'point' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than {approx}2 x 10{sup -13} cm/Hz. This sensitivity is two orders of magnitude greater than that of currently available sensors.

  5. Eliminating thermal violin spikes from LIGO noise

    International Nuclear Information System (INIS)

    Santamore, D. H.; Levin, Yuri

    2001-01-01

    We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally induced motion of a small portion of (a 'point' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than ∼2 x 10 -13 cm/Hz. This sensitivity is two orders of magnitude greater than that of currently available sensors

  6. Noise Estimation and Quality Assessment of Gaussian Noise Corrupted Images

    Science.gov (United States)

    Kamble, V. M.; Bhurchandi, K.

    2018-03-01

    Evaluating the exact quantity of noise present in an image and quality of an image in the absence of reference image is a challenging task. We propose a near perfect noise estimation method and a no reference image quality assessment method for images corrupted by Gaussian noise. The proposed methods obtain initial estimate of noise standard deviation present in an image using the median of wavelet transform coefficients and then obtains a near to exact estimate using curve fitting. The proposed noise estimation method provides the estimate of noise within average error of +/-4%. For quality assessment, this noise estimate is mapped to fit the Differential Mean Opinion Score (DMOS) using a nonlinear function. The proposed methods require minimum training and yields the noise estimate and image quality score. Images from Laboratory for image and Video Processing (LIVE) database and Computational Perception and Image Quality (CSIQ) database are used for validation of the proposed quality assessment method. Experimental results show that the performance of proposed quality assessment method is at par with the existing no reference image quality assessment metric for Gaussian noise corrupted images.

  7. Thermal diffusivity imaging with the thermal lens microscope.

    Science.gov (United States)

    Dada, Oluwatosin O; Feist, Peter E; Dovichi, Norman J

    2011-12-01

    A coaxial thermal lens microscope was used to generate images based on both the absorbance and thermal diffusivity of histological samples. A pump beam was modulated at frequencies ranging from 50 kHz to 5 MHz using an acousto-optic modulator. The pump and a CW probe beam were combined with a dichroic mirror, directed into an inverted microscope, and focused onto the specimen. The change in the transmitted probe beam's center intensity was detected with a photodiode. The photodiode's signal and a reference signal from the modulator were sent to a high-speed lock-in amplifier. The in-phase and quadrature signals were recorded as a sample was translated through the focused beams and used to generate images based on the amplitude and phase of the lock-in amplifier's signal. The amplitude is related to the absorbance and the phase is related to the thermal diffusivity of the sample. Thin sections of stained liver and bone tissues were imaged; the contrast and signal-to-noise ratio of the phase image was highest at frequencies from 0.1-1 MHz and dropped at higher frequencies. The spatial resolution was 2.5 μm for both amplitude and phase images, limited by the pump beam spot size. © 2011 Optical Society of America

  8. Chaos and thermal noise in the rf-biased Josephson junction

    International Nuclear Information System (INIS)

    Kautz, R.L.

    1985-01-01

    The effect of thermal noise on chaotic behavior in the rf-biased Josephson junction is studied through digital simulations. In instances for which chaotic behavior occurs in the noise-free system, it is found that the dynamics of the system are almost unchanged by the addition of thermal noise unless the level of thermal noise exceeds that of the chaotic state. In instances for which the only stable states of the noise-free system are periodic solutions, small amounts of thermal noise can induce the junction to hop between two different dynamical states, producing a low-frequency noise level much higher than that of the thermal noise. Such noise-induced hopping can occur either between two periodic solutions or between a periodic solution and a metastable chaotic solution. When a metastable chaotic state is involved, temperatures somewhat higher than those which produce hopping can destablize the periodic solution to the point where the system spends virtually all of its time in the metastable chaotic state, creating noise-induced chaos. The similarities between chaotic behavior at zero temperature and noise-induced chaos are sufficiently strong that it may be difficult to distinguish the two cases experimentally

  9. Manipulating the Flow of Thermal Noise in Quantum Devices

    Science.gov (United States)

    Barzanjeh, Shabir; Aquilina, Matteo; Xuereb, André

    2018-02-01

    There has been significant interest recently in using complex quantum systems to create effective nonreciprocal dynamics. Proposals have been put forward for the realization of artificial magnetic fields for photons and phonons; experimental progress is fast making these proposals a reality. Much work has concentrated on the use of such systems for controlling the flow of signals, e.g., to create isolators or directional amplifiers for optical signals. In this Letter, we build on this work but move in a different direction. We develop the theory of and discuss a potential realization for the controllable flow of thermal noise in quantum systems. We demonstrate theoretically that the unidirectional flow of thermal noise is possible within quantum cascaded systems. Viewing an optomechanical platform as a cascaded system we show here that one can ultimately control the direction of the flow of thermal noise. By appropriately engineering the mechanical resonator, which acts as an artificial reservoir, the flow of thermal noise can be constrained to a desired direction, yielding a thermal rectifier. The proposed quantum thermal noise rectifier could potentially be used to develop devices such as a thermal modulator, a thermal router, and a thermal amplifier for nanoelectronic devices and superconducting circuits.

  10. Quantitative assessment of pain-related thermal dysfunction through clinical digital infrared thermal imaging

    Directory of Open Access Journals (Sweden)

    Frize Monique

    2004-06-01

    Full Text Available Abstract Background The skin temperature distribution of a healthy human body exhibits a contralateral symmetry. Some nociceptive and most neuropathic pain pathologies are associated with an alteration of the thermal distribution of the human body. Since the dissipation of heat through the skin occurs for the most part in the form of infrared radiation, infrared thermography is the method of choice to study the physiology of thermoregulation and the thermal dysfunction associated with pain. Assessing thermograms is a complex and subjective task that can be greatly facilitated by computerised techniques. Methods This paper presents techniques for automated computerised assessment of thermal images of pain, in order to facilitate the physician's decision making. First, the thermal images are pre-processed to reduce the noise introduced during the initial acquisition and to extract the irrelevant background. Then, potential regions of interest are identified using fixed dermatomal subdivisions of the body, isothermal analysis and segmentation techniques. Finally, we assess the degree of asymmetry between contralateral regions of interest using statistical computations and distance measures between comparable regions. Results The wavelet domain-based Poisson noise removal techniques compared favourably against Wiener and other wavelet-based denoising methods, when qualitative criteria were used. It was shown to improve slightly the subsequent analysis. The automated background removal technique based on thresholding and morphological operations was successful for both noisy and denoised images with a correct removal rate of 85% of the images in the database. The automation of the regions of interest (ROIs delimitation process was achieved successfully for images with a good contralateral symmetry. Isothermal division complemented well the fixed ROIs division based on dermatomes, giving a more accurate map of potentially abnormal regions. The measure

  11. Image processing on the image with pixel noise bits removed

    Science.gov (United States)

    Chuang, Keh-Shih; Wu, Christine

    1992-06-01

    Our previous studies used statistical methods to assess the noise level in digital images of various radiological modalities. We separated the pixel data into signal bits and noise bits and demonstrated visually that the removal of the noise bits does not affect the image quality. In this paper we apply image enhancement techniques on noise-bits-removed images and demonstrate that the removal of noise bits has no effect on the image property. The image processing techniques used are gray-level look up table transformation, Sobel edge detector, and 3-D surface display. Preliminary results show no noticeable difference between original image and noise bits removed image using look up table operation and Sobel edge enhancement. There is a slight enhancement of the slicing artifact in the 3-D surface display of the noise bits removed image.

  12. Numerically modeling Brownian thermal noise in amorphous and crystalline thin coatings

    Science.gov (United States)

    Lovelace, Geoffrey; Demos, Nicholas; Khan, Haroon

    2018-01-01

    Thermal noise is expected to be one of the noise sources limiting the astrophysical reach of Advanced LIGO (once commissioning is complete) and third-generation detectors. Adopting crystalline materials for thin, reflecting mirror coatings, rather than the amorphous coatings used in current-generation detectors, could potentially reduce thermal noise. Understanding and reducing thermal noise requires accurate theoretical models, but modeling thermal noise analytically is especially challenging with crystalline materials. Thermal noise models typically rely on the fluctuation-dissipation theorem, which relates the power spectral density of the thermal noise to an auxiliary elastic problem. In this paper, we present results from a new, open-source tool that numerically solves the auxiliary elastic problem to compute the Brownian thermal noise for both amorphous and crystalline coatings. We employ the open-source deal.ii and PETSc frameworks to solve the auxiliary elastic problem using a finite-element method, adaptive mesh refinement, and parallel processing that enables us to use high resolutions capable of resolving the thin reflective coating. We verify numerical convergence, and by running on up to hundreds of compute cores, we resolve the coating elastic energy in the auxiliary problem to approximately 0.1%. We compare with approximate analytic solutions for amorphous materials, and we verify that our solutions scale as expected with changing beam size, mirror dimensions, and coating thickness. Finally, we model the crystalline coating thermal noise in an experiment reported by Cole et al (2013 Nat. Photon. 7 644–50), comparing our results to a simpler numerical calculation that treats the coating as an ‘effectively amorphous’ material. We find that treating the coating as a cubic crystal instead of as an effectively amorphous material increases the thermal noise by about 3%. Our results are a step toward better understanding and reducing thermal noise to

  13. Image reconstruction under non-Gaussian noise

    DEFF Research Database (Denmark)

    Sciacchitano, Federica

    During acquisition and transmission, images are often blurred and corrupted by noise. One of the fundamental tasks of image processing is to reconstruct the clean image from a degraded version. The process of recovering the original image from the data is an example of inverse problem. Due...... to the ill-posedness of the problem, the simple inversion of the degradation model does not give any good reconstructions. Therefore, to deal with the ill-posedness it is necessary to use some prior information on the solution or the model and the Bayesian approach. Additive Gaussian noise has been......D thesis intends to solve some of the many open questions for image restoration under non-Gaussian noise. The two main kinds of noise studied in this PhD project are the impulse noise and the Cauchy noise. Impulse noise is due to for instance the malfunctioning pixel elements in the camera sensors, errors...

  14. Analysis of sharpness increase by image noise

    Science.gov (United States)

    Kurihara, Takehito; Aoki, Naokazu; Kobayashi, Hiroyuki

    2009-02-01

    Motivated by the reported increase in sharpness by image noise, we investigated how noise affects sharpness perception. We first used natural images of tree bark with different amounts of noise to see whether noise enhances sharpness. Although the result showed sharpness decreased as noise amount increased, some observers seemed to perceive more sharpness with increasing noise, while the others did not. We next used 1D and 2D uni-frequency patterns as stimuli in an attempt to reduce such variability in the judgment. The result showed, for higher frequency stimuli, sharpness decreased as the noise amount increased, while sharpness of the lower frequency stimuli increased at a certain noise level. From this result, we thought image noise might reduce sharpness at edges, but be able to improve sharpness of lower frequency component or texture in image. To prove this prediction, we experimented again with the natural image used in the first experiment. Stimuli were made by applying noise separately to edge or to texture part of the image. The result showed noise, when added to edge region, only decreased sharpness, whereas when added to texture, could improve sharpness. We think it is the interaction between noise and texture that sharpens image.

  15. Robust reflective ghost imaging against different partially polarized thermal light

    Science.gov (United States)

    Li, Hong-Guo; Wang, Yan; Zhang, Rui-Xue; Zhang, De-Jian; Liu, Hong-Chao; Li, Zong-Guo; Xiong, Jun

    2018-03-01

    We theoretically study the influence of degree of polarization (DOP) of thermal light on the contrast-to-noise ratio (CNR) of the reflective ghost imaging (RGI), which is a novel and indirect imaging modality. An expression for the CNR of RGI with partially polarized thermal light is carefully derived, which suggests a weak dependence of CNR on the DOP, especially when the ratio of the object size to the speckle size of thermal light has a large value. Different from conventional imaging approaches, our work reveals that RGI is much more robust against the DOP of the light source, which thereby has advantages in practical applications, such as remote sensing.

  16. Electronic noise in CT detectors: Impact on image noise and artifacts.

    Science.gov (United States)

    Duan, Xinhui; Wang, Jia; Leng, Shuai; Schmidt, Bernhard; Allmendinger, Thomas; Grant, Katharine; Flohr, Thomas; McCollough, Cynthia H

    2013-10-01

    The objective of our study was to evaluate in phantoms the differences in CT image noise and artifact level between two types of commercial CT detectors: one with distributed electronics (conventional) and one with integrated electronics intended to decrease system electronic noise. Cylindric water phantoms of 20, 30, and 40 cm in diameter were scanned using two CT scanners, one equipped with integrated detector electronics and one with distributed detector electronics. All other scanning parameters were identical. Scans were acquired at four tube potentials and 10 tube currents. Semianthropomorphic phantoms were scanned to mimic the shoulder and abdominal regions. Images of two patients were also selected to show the clinical values of the integrated detector. Reduction of image noise with the integrated detector depended on phantom size, tube potential, and tube current. Scans that had low detected signal had the greatest reductions in noise, up to 40% for a 30-cm phantom scanned using 80 kV. This noise reduction translated into up to 50% in dose reduction to achieve equivalent image noise. Streak artifacts through regions of high attenuation were reduced by up to 45% on scans obtained using the integrated detector. Patient images also showed superior image quality for the integrated detector. For the same applied radiation level, the use of integrated electronics in a CT detector showed a substantially reduced level of electronic noise, resulting in reductions in image noise and artifacts, compared with detectors having distributed electronics.

  17. Partial removal of correlated noise in thermal imagery

    International Nuclear Information System (INIS)

    Borel, C.C.; Cooke, B.J.; Laubscher, B.E.

    1996-01-01

    Correlated noise occurs in many imaging systems such as scanners and push-broom imagers. The sources of correlated noise can be from the detectors, pre-amplifiers and sampling circuits. Correlated noise appears as streaking along the scan direction of a scanner or in the along track direction of a push-broom imager. We have developed algorithms to simulate correlated noise and pre-filter to reduce the amount of streaking while not destroying the scene content. The pre- filter in the Fourier domain consists of the product of two filters. One filter models the correlated noise spectrum, the other is a windowing function e.g. Gaussian or Hanning window with variable width to block high frequency noise away from the origin of the Fourier Transform of the image data. We have optimized the filter parameters for various scenes and find improvements of the RMS error of the original minus the pre-filtered noisy image

  18. Noise-gating to Clean Astrophysical Image Data

    International Nuclear Information System (INIS)

    DeForest, C. E.

    2017-01-01

    I present a family of algorithms to reduce noise in astrophysical images and image sequences, preserving more information from the original data than is retained by conventional techniques. The family uses locally adaptive filters (“noise gates”) in the Fourier domain to separate coherent image structure from background noise based on the statistics of local neighborhoods in the image. Processing of solar data limited by simple shot noise or by additive noise reveals image structure not easily visible in the originals, preserves photometry of observable features, and reduces shot noise by a factor of 10 or more with little to no apparent loss of resolution. This reveals faint features that were either not directly discernible or not sufficiently strongly detected for quantitative analysis. The method works best on image sequences containing related subjects, for example movies of solar evolution, but is also applicable to single images provided that there are enough pixels. The adaptive filter uses the statistical properties of noise and of local neighborhoods in the data to discriminate between coherent features and incoherent noise without reference to the specific shape or evolution of those features. The technique can potentially be modified in a straightforward way to exploit additional a priori knowledge about the functional form of the noise.

  19. Noise-gating to Clean Astrophysical Image Data

    Energy Technology Data Exchange (ETDEWEB)

    DeForest, C. E. [Southwest Research Institute, 1050 Walnut Street, Boulder, CO (United States)

    2017-04-01

    I present a family of algorithms to reduce noise in astrophysical images and image sequences, preserving more information from the original data than is retained by conventional techniques. The family uses locally adaptive filters (“noise gates”) in the Fourier domain to separate coherent image structure from background noise based on the statistics of local neighborhoods in the image. Processing of solar data limited by simple shot noise or by additive noise reveals image structure not easily visible in the originals, preserves photometry of observable features, and reduces shot noise by a factor of 10 or more with little to no apparent loss of resolution. This reveals faint features that were either not directly discernible or not sufficiently strongly detected for quantitative analysis. The method works best on image sequences containing related subjects, for example movies of solar evolution, but is also applicable to single images provided that there are enough pixels. The adaptive filter uses the statistical properties of noise and of local neighborhoods in the data to discriminate between coherent features and incoherent noise without reference to the specific shape or evolution of those features. The technique can potentially be modified in a straightforward way to exploit additional a priori knowledge about the functional form of the noise.

  20. Image denoising based on noise detection

    Science.gov (United States)

    Jiang, Yuanxiang; Yuan, Rui; Sun, Yuqiu; Tian, Jinwen

    2018-03-01

    Because of the noise points in the images, any operation of denoising would change the original information of non-noise pixel. A noise detection algorithm based on fractional calculus was proposed to denoise in this paper. Convolution of the image was made to gain direction gradient masks firstly. Then, the mean gray was calculated to obtain the gradient detection maps. Logical product was made to acquire noise position image next. Comparisons in the visual effect and evaluation parameters after processing, the results of experiment showed that the denoising algorithms based on noise were better than that of traditional methods in both subjective and objective aspects.

  1. Finite-difference time-domain simulation of thermal noise in open cavities

    International Nuclear Information System (INIS)

    Andreasen, Jonathan; Cao Hui; Taflove, Allen; Kumar, Prem; Cao Changqi

    2008-01-01

    A numerical model based on the finite-difference time-domain (FDTD) method is developed to simulate thermal noise in open cavities owing to output coupling. The absorbing boundary of the FDTD grid is treated as a blackbody, whose thermal radiation penetrates the cavity in the grid. The calculated amount of thermal noise in a one-dimensional dielectric cavity recovers the standard result of the quantum Langevin equation in the Markovian regime. Our FDTD simulation also demonstrates that in the non-Markovian regime the buildup of the intracavity noise field depends on the ratio of the cavity photon lifetime to the coherence time of thermal radiation. The advantage of our numerical method is that the thermal noise is introduced in the time domain without prior knowledge of cavity modes

  2. Restoration for Noise Removal in Quantum Images

    Science.gov (United States)

    Liu, Kai; Zhang, Yi; Lu, Kai; Wang, Xiaoping

    2017-09-01

    Quantum computation has become increasingly attractive in the past few decades due to its extraordinary performance. As a result, some studies focusing on image representation and processing via quantum mechanics have been done. However, few of them have considered the quantum operations for images restoration. To address this problem, three noise removal algorithms are proposed in this paper based on the novel enhanced quantum representation model, oriented to two kinds of noise pollution (Salt-and-Pepper noise and Gaussian noise). For the first algorithm Q-Mean, it is designed to remove the Salt-and-Pepper noise. The noise points are extracted through comparisons with the adjacent pixel values, after which the restoration operation is finished by mean filtering. As for the second method Q-Gauss, a special mask is applied to weaken the Gaussian noise pollution. The third algorithm Q-Adapt is effective for the source image containing unknown noise. The type of noise can be judged through the quantum statistic operations for the color value of the whole image, and then different noise removal algorithms are used to conduct image restoration respectively. Performance analysis reveals that our methods can offer high restoration quality and achieve significant speedup through inherent parallelism of quantum computation.

  3. Impact of image noise on gamma index calculation

    International Nuclear Information System (INIS)

    Chen, M; Mo, X; Parnell, D; Olivera, G; Galmarini, D; Lu, W

    2014-01-01

    Purpose: The Gamma Index defines an asymmetric metric between the evaluated image and the reference image. It provides a quantitative comparison that can be used to indicate sample-wised pass/fail on the agreement of the two images. The Gamma passing/failing rate has become an important clinical evaluation tool. However, the presence of noise in the evaluated and/or reference images may change the Gamma Index, hence the passing/failing rate, and further, clinical decisions. In this work, we systematically studied the impact of the image noise on the Gamma Index calculation. Methods: We used both analytic formulation and numerical calculations in our study. The numerical calculations included simulations and clinical images. Three different noise scenarios were studied in simulations: noise in reference images only, in evaluated images only, and in both. Both white and spatially correlated noises of various magnitudes were simulated. For clinical images of various noise levels, the Gamma Index of measurement against calculation, calculation against measurement, and measurement against measurement, were evaluated. Results: Numerical calculations for both the simulation and clinical data agreed with the analytic formulations, and the clinical data agreed with the simulations. For the Gamma Index of measurement against calculation, its distribution has an increased mean and an increased standard deviation as the noise increases. On the contrary, for the Gamma index of calculation against measurement, its distribution has a decreased mean and stabilized standard deviation as the noise increases. White noise has greater impact on the Gamma Index than spatially correlated noise. Conclusions: The noise has significant impact on the Gamma Index calculation and the impact is asymmetric. The Gamma Index should be reported along with the noise levels in both reference and evaluated images. Reporting of the Gamma Index with switched roles of the images as reference and

  4. Impact of Image Noise on Gamma Index Calculation

    Science.gov (United States)

    Chen, M.; Mo, X.; Parnell, D.; Olivera, G.; Galmarini, D.; Lu, W.

    2014-03-01

    Purpose: The Gamma Index defines an asymmetric metric between the evaluated image and the reference image. It provides a quantitative comparison that can be used to indicate sample-wised pass/fail on the agreement of the two images. The Gamma passing/failing rate has become an important clinical evaluation tool. However, the presence of noise in the evaluated and/or reference images may change the Gamma Index, hence the passing/failing rate, and further, clinical decisions. In this work, we systematically studied the impact of the image noise on the Gamma Index calculation. Methods: We used both analytic formulation and numerical calculations in our study. The numerical calculations included simulations and clinical images. Three different noise scenarios were studied in simulations: noise in reference images only, in evaluated images only, and in both. Both white and spatially correlated noises of various magnitudes were simulated. For clinical images of various noise levels, the Gamma Index of measurement against calculation, calculation against measurement, and measurement against measurement, were evaluated. Results: Numerical calculations for both the simulation and clinical data agreed with the analytic formulations, and the clinical data agreed with the simulations. For the Gamma Index of measurement against calculation, its distribution has an increased mean and an increased standard deviation as the noise increases. On the contrary, for the Gamma index of calculation against measurement, its distribution has a decreased mean and stabilized standard deviation as the noise increases. White noise has greater impact on the Gamma Index than spatially correlated noise. Conclusions: The noise has significant impact on the Gamma Index calculation and the impact is asymmetric. The Gamma Index should be reported along with the noise levels in both reference and evaluated images. Reporting of the Gamma Index with switched roles of the images as reference and

  5. Adapting Local Features for Face Detection in Thermal Image

    Directory of Open Access Journals (Sweden)

    Chao Ma

    2017-11-01

    Full Text Available A thermal camera captures the temperature distribution of a scene as a thermal image. In thermal images, facial appearances of different people under different lighting conditions are similar. This is because facial temperature distribution is generally constant and not affected by lighting condition. This similarity in face appearances is advantageous for face detection. To detect faces in thermal images, cascade classifiers with Haar-like features are generally used. However, there are few studies exploring the local features for face detection in thermal images. In this paper, we introduce two approaches relying on local features for face detection in thermal images. First, we create new feature types by extending Multi-Block LBP. We consider a margin around the reference and the generally constant distribution of facial temperature. In this way, we make the features more robust to image noise and more effective for face detection in thermal images. Second, we propose an AdaBoost-based training method to get cascade classifiers with multiple types of local features. These feature types have different advantages. In this way we enhance the description power of local features. We did a hold-out validation experiment and a field experiment. In the hold-out validation experiment, we captured a dataset from 20 participants, comprising 14 males and 6 females. For each participant, we captured 420 images with 10 variations in camera distance, 21 poses, and 2 appearances (participant with/without glasses. We compared the performance of cascade classifiers trained by different sets of the features. The experiment results showed that the proposed approaches effectively improve the performance of face detection in thermal images. In the field experiment, we compared the face detection performance in realistic scenes using thermal and RGB images, and gave discussion based on the results.

  6. Acoustic-noise-optimized diffusion-weighted imaging.

    Science.gov (United States)

    Ott, Martin; Blaimer, Martin; Grodzki, David M; Breuer, Felix A; Roesch, Julie; Dörfler, Arnd; Heismann, Björn; Jakob, Peter M

    2015-12-01

    This work was aimed at reducing acoustic noise in diffusion-weighted MR imaging (DWI) that might reach acoustic noise levels of over 100 dB(A) in clinical practice. A diffusion-weighted readout-segmented echo-planar imaging (EPI) sequence was optimized for acoustic noise by utilizing small readout segment widths to obtain low gradient slew rates and amplitudes instead of faster k-space coverage. In addition, all other gradients were optimized for low slew rates. Volunteer and patient imaging experiments were conducted to demonstrate the feasibility of the method. Acoustic noise measurements were performed and analyzed for four different DWI measurement protocols at 1.5T and 3T. An acoustic noise reduction of up to 20 dB(A) was achieved, which corresponds to a fourfold reduction in acoustic perception. The image quality was preserved at the level of a standard single-shot (ss)-EPI sequence, with a 27-54% increase in scan time. The diffusion-weighted imaging technique proposed in this study allowed a substantial reduction in the level of acoustic noise compared to standard single-shot diffusion-weighted EPI. This is expected to afford considerably more patient comfort, but a larger study would be necessary to fully characterize the subjective changes in patient experience.

  7. Temporal Noise Analysis of Charge-Domain Sampling Readout Circuits for CMOS Image Sensors

    Directory of Open Access Journals (Sweden)

    Xiaoliang Ge

    2018-02-01

    Full Text Available This paper presents a temporal noise analysis of charge-domain sampling readout circuits for Complementary Metal-Oxide Semiconductor (CMOS image sensors. In order to address the trade-off between the low input-referred noise and high dynamic range, a Gm-cell-based pixel together with a charge-domain correlated-double sampling (CDS technique has been proposed to provide a way to efficiently embed a tunable conversion gain along the read-out path. Such readout topology, however, operates in a non-stationery large-signal behavior, and the statistical properties of its temporal noise are a function of time. Conventional noise analysis methods for CMOS image sensors are based on steady-state signal models, and therefore cannot be readily applied for Gm-cell-based pixels. In this paper, we develop analysis models for both thermal noise and flicker noise in Gm-cell-based pixels by employing the time-domain linear analysis approach and the non-stationary noise analysis theory, which help to quantitatively evaluate the temporal noise characteristic of Gm-cell-based pixels. Both models were numerically computed in MATLAB using design parameters of a prototype chip, and compared with both simulation and experimental results. The good agreement between the theoretical and measurement results verifies the effectiveness of the proposed noise analysis models.

  8. Estimation of images degraded by film-grain noise.

    Science.gov (United States)

    Naderi, F; Sawchuk, A A

    1978-04-15

    Film-grain noise describes the intrinsic noise produced by a photographic emulsion during the process of image recording and reproduction. In this paper we consider the restoration of images degraded by film-grain noise. First a detailed model for the over-all photographic imaging system is presented. The model includes linear blurring effects and the signal-dependent effect of film-grain noise. The accuracy of this model is tested by simulating images according to it and comparing the results to images of similar targets that were actually recorded on film. The restoration of images degraded by film-grain noise is then considered in the context of estimation theory. A discrete Wiener filer is developed which explicitly allows for the signal dependence of the noise. The filter adaptively alters its characteristics based on the nonstationary first order statistics of an image and is shown to have advantages over the conventional Wiener filter. Experimental results for modeling and the adaptive estimation filter are presented.

  9. On the thermal noise limit of cellular membranes.

    Science.gov (United States)

    Vincze, Gy; Szasz, N; Szasz, A

    2005-01-01

    Comparison of thermal noise limits and the effects of low frequency electromagnetic fields (LFEMF) on the cellular membrane have important implications for the study of bioelectro-magnetism in this regime. Over a decade ago, Weaver and Astumian developed a model to show that thermal noise can limit the efficacy of LFEMF. A recent report by Kaune [Kaune (2002) Bioelectromagnetics 23:622-628], however, contradicted their findings. Kaune assumes that the conductance noise current of cell membrane can be decomposed into two components, where one of them is identical regarding all segments (coherent), while the other is different (incoherent). Besides, this decomposition is not unequivocal and contradicts to the statistical independence of the segment noise currents, and therefore to the second law of thermodynamics as well. We suggest the procedure based on the method of symmetrical components, by the means of which we can re-interpret the result of Kaune in a correct way. 2004 Wiley-Liss, Inc.

  10. Wavelet-based de-noising algorithm for images acquired with parallel magnetic resonance imaging (MRI)

    International Nuclear Information System (INIS)

    Delakis, Ioannis; Hammad, Omer; Kitney, Richard I

    2007-01-01

    Wavelet-based de-noising has been shown to improve image signal-to-noise ratio in magnetic resonance imaging (MRI) while maintaining spatial resolution. Wavelet-based de-noising techniques typically implemented in MRI require that noise displays uniform spatial distribution. However, images acquired with parallel MRI have spatially varying noise levels. In this work, a new algorithm for filtering images with parallel MRI is presented. The proposed algorithm extracts the edges from the original image and then generates a noise map from the wavelet coefficients at finer scales. The noise map is zeroed at locations where edges have been detected and directional analysis is also used to calculate noise in regions of low-contrast edges that may not have been detected. The new methodology was applied on phantom and brain images and compared with other applicable de-noising techniques. The performance of the proposed algorithm was shown to be comparable with other techniques in central areas of the images, where noise levels are high. In addition, finer details and edges were maintained in peripheral areas, where noise levels are low. The proposed methodology is fully automated and can be applied on final reconstructed images without requiring sensitivity profiles or noise matrices of the receiver coils, therefore making it suitable for implementation in a clinical MRI setting

  11. Noise estimation for remote sensing image data analysis

    Science.gov (United States)

    Du, Qian

    2004-01-01

    Noise estimation does not receive much attention in remote sensing society. It may be because normally noise is not large enough to impair image analysis result. Noise estimation is also very challenging due to the randomness nature of the noise (for random noise) and the difficulty of separating the noise component from the signal in each specific location. We review and propose seven different types of methods to estimate noise variance and noise covariance matrix in a remotely sensed image. In the experiment, it is demonstrated that a good noise estimate can improve the performance of an algorithm via noise whitening if this algorithm assumes white noise.

  12. Utility of noise addition image made by using water phantom and image addition and subtraction software

    International Nuclear Information System (INIS)

    Watanabe, Ryo; Aoki, Takahiro; Hayano, Mizuho; Ogawa, Masato; Mituzono, Hiroki; Watanabe, Yuka

    2010-01-01

    In optimizing exposures, it is very important to evaluate the impact of image noise on image quality. To realize this, there is a need to evaluate how much image noise will make the subject disease invisible. But generally it is very difficult to shoot images of different quality in a clinical examination. Thus, a method to create a noise addition image by adding the image noise to raw data has been reported. However, this approach requires a special system, so it is difficult to implement in many facilities. We have invented a method to easily create a noise addition image by using the water phantom and image add-subtract software that accompanies the device. To create a noise addition image, first we made a noise image by subtracting the water phantom with different standard deviation (SD). A noise addition image was then created by adding the noise image to the original image. By using this method, a simulation image with intergraded SD can be created from the original. Moreover, the noise frequency component of the created noise addition image is as same as the real image. Thus, the relationship of image quality to SD in the clinical image can be evaluated. Although this method is an easy method of LDSI creation on image data, a noise addition image can be easily created by using image addition and subtraction software and water phantom, and this can be implemented in many facilities. (author)

  13. Thermal noise from optical coatings in gravitational wave detectors.

    Science.gov (United States)

    Harry, Gregory M; Armandula, Helena; Black, Eric; Crooks, D R M; Cagnoli, Gianpietro; Hough, Jim; Murray, Peter; Reid, Stuart; Rowan, Sheila; Sneddon, Peter; Fejer, Martin M; Route, Roger; Penn, Steven D

    2006-03-01

    Gravitational waves are a prediction of Einstein's general theory of relativity. These waves are created by massive objects, like neutron stars or black holes, oscillating at speeds appreciable to the speed of light. The detectable effect on the Earth of these waves is extremely small, however, creating strains of the order of 10(-21). There are a number of basic physics experiments around the world designed to detect these waves by using interferometers with very long arms, up to 4 km in length. The next-generation interferometers are currently being designed, and the thermal noise in the mirrors will set the sensitivity over much of the usable bandwidth. Thermal noise arising from mechanical loss in the optical coatings put on the mirrors will be a significant source of noise. Achieving higher sensitivity through lower mechanical loss coatings, while preserving the crucial optical and thermal properties, is an area of active research right now.

  14. Statistical and heuristic image noise extraction (SHINE): a new method for processing Poisson noise in scintigraphic images

    International Nuclear Information System (INIS)

    Hannequin, Pascal; Mas, Jacky

    2002-01-01

    Poisson noise is one of the factors degrading scintigraphic images, especially at low count level, due to the statistical nature of photon detection. We have developed an original procedure, named statistical and heuristic image noise extraction (SHINE), to reduce the Poisson noise contained in the scintigraphic images, preserving the resolution, the contrast and the texture. The SHINE procedure consists in dividing the image into 4 x 4 blocks and performing a correspondence analysis on these blocks. Each block is then reconstructed using its own significant factors which are selected using an original statistical variance test. The SHINE procedure has been validated using a line numerical phantom and a hot spots and cold spots real phantom. The reference images are the noise-free simulated images for the numerical phantom and an extremely high counts image for the real phantom. The SHINE procedure has then been applied to the Jaszczak phantom and clinical data including planar bone scintigraphy, planar Sestamibi scintigraphy and Tl-201 myocardial SPECT. The SHINE procedure reduces the mean normalized error between the noisy images and the corresponding reference images. This reduction is constant and does not change with the count level. The SNR in a SHINE processed image is close to that of the corresponding raw image with twice the number of counts. The visual results with the Jaszczak phantom SPECT have shown that SHINE preserves the contrast and the resolution of the slices well. Clinical examples have shown no visual difference between the SHINE images and the corresponding raw images obtained with twice the acquisition duration. SHINE is an entirely automatic procedure which enables halving the acquisition time or the injected dose in scintigraphic acquisitions. It can be applied to all scintigraphic images, including PET data, and to all low-count photon images

  15. Noise Characterization and Performance of MODIS Thermal Emissive Bands

    Science.gov (United States)

    Madhavan, Sriharsha; Xiong, Xiaoxiong; Wu, Aisheng; Wenny, Brian; Chiang, Kwofu; Chen, Na; Wang, Zhipeng; Li, Yonghong

    2016-01-01

    The MODerate-resolution Imaging Spectroradiometer (MODIS) is a premier Earth-observing sensor of the early 21st century, flying onboard the Terra (T) and Aqua (A) spacecraft. Both instruments far exceeded their six-year design life and continue to operate satisfactorily for more than 15 and 13 years, respectively. The MODIS instrument is designed to make observations at nearly a 100% duty cycle covering the entire Earth in less than two days. The MODIS sensor characteristics include a spectral coverage from 0.41micrometers to 14.4 micrometers, of which those wavelengths ranging from 3.7 micrometers to 14.4 micrometers cover the thermal infrared region which is interspaced in 16 thermal emissive bands (TEBs). Each of the TEB contains ten detectors which record samples at a spatial resolution of 1 km. In order to ensure a high level of accuracy for the TEB-measured top-of-atmosphere radiances, an onboard blackbody (BB) is used as the calibration source. This paper reports the noise characterization and performance of the TEB on various counts. First, the stability of the onboard BB is evaluated to understand the effectiveness of the calibration source. Next, key noise metrics such as the noise equivalent temperature difference and the noise equivalent dn difference (NEdN) for the various TEBs are determined from multiple temperature sources. These sources include the nominally controlled BB temperature of 290 K for T-MODIS and 285 K for A-MODIS, as well as a BB warm up-cool down cycle that is performed over a temperature range from roughly 270 to 315 K. The space-view port that measures the background signal serves as a viable cold temperature source for measuring noise. In addition, a well characterized Earth-view target, the Dome Concordia site located in the Antarctic plateau, is used for characterizing the stability of the sensor, indirectly providing a measure of the NEdN. Based on this rigorous characterization, a list of the noisy and inoperable detectors for

  16. Thermal noise reduction for present and future gravitational wave detectors

    Energy Technology Data Exchange (ETDEWEB)

    Amico, P.; Bosi, L.; Gammaitoni, L.; Losurdo, G.; Marchesoni, F.; Mazzoni, M.; Punturo, M. E-mail: michele.punturo@pg.infn.it; Stanga, R.; Toncelli, A.; Tonelli, M.; Travasso, F.; Vetrano, F.; Vocca, H

    2004-02-01

    Thermal noise in mirror suspension is and will be the most severe fundamental limit to the low-frequency sensitivity of interferometric gravitational wave detectors currently under construction. The technical solutions, adopted in the Virgo detector, optimize the current suspension scheme, but new materials and new designs are needed to further reduce the suspension thermal noise. Silicon fibers are promising candidates both for room temperature advanced detectors and for future cryogenic interferometric detectors.

  17. Towards measuring the off-resonant thermal noise of a pendulum mirror

    CERN Document Server

    Leonhardt, V; Kloevekorn, P; Willke, B; Lück, H B; Danzmann, K

    2002-01-01

    Thermal noise is one of the dominant noise sources in interferometric length measurements and can limit the sensitivity of gravitational wave detectors. Our goal is to analyse the off-resonant thermal noise of a high Q pendulum. Therefore we interferometrically detect the length changes of a 2.3 cm long optical resonator, which for good seismic isolation consists of two multiple stage pendulums. We are able to lock the length of this optical resonator to a frequency-stabilized laser beam and as a result get the spectral density of the differential mirror movement.

  18. Thermal voltage noise in layered superconductors

    International Nuclear Information System (INIS)

    Ashkenazy, V.D.; Jung, G.; Shapiro, B.Y.

    1995-01-01

    Thermal voltage noise in the mixed state of type-II superconductors has been calculated taking into account fluctuation modes of nonrigid vortices. It has been shown that bending of vortices leads to new effects in thermal-voltage-noise spectra at high frequencies. The power spectrum reflecting fluctuations of rigid vortices is suppressed at very low frequencies and saturates into a white spectrum at a characteristic frequency depending on the strip width. At high frequencies tilt modes of flexible vortices start to contribute to the fluctuating voltages and the power spectrum undergoes three subsequent magnitude increases, following ω 1/2 -, ω 2 -, and again ω 1/2 -like behavior before becoming white again. It has been shown that for layered superconductors of a moderate anisotropy the second ω 1/2 -like increase disappears at magnetic fields exceeding a certain threshold field corresponding to the crossover field between two-dimensional and three-dimensional vortex-lattice melting. Field dependencies of characteristic frequencies separating different regimes of spectral behavior have been evaluated and shown to be qualitatively different for low and high magnetic fields

  19. Robust image authentication in the presence of noise

    CERN Document Server

    2015-01-01

    This book addresses the problems that hinder image authentication in the presence of noise. It considers the advantages and disadvantages of existing algorithms for image authentication and shows new approaches and solutions for robust image authentication. The state of the art algorithms are compared and, furthermore, innovative approaches and algorithms are introduced. The introduced algorithms are applied to improve image authentication, watermarking and biometry.    Aside from presenting new directions and algorithms for robust image authentication in the presence of noise, as well as image correction, this book also:   Provides an overview of the state of the art algorithms for image authentication in the presence of noise and modifications, as well as a comparison of these algorithms, Presents novel algorithms for robust image authentication, whereby the image is tried to be corrected and authenticated, Examines different views for the solution of problems connected to image authentication in the pre...

  20. Noise characteristics of neutron images obtained by cooled CCD device

    International Nuclear Information System (INIS)

    Taniguchi, Ryoichi; Sasaki, Ryoya; Okuda, Shuichi; Okamoto, Ken-Ichi; Ogawa, Yoshihiro; Tsujimoto, Tadashi

    2009-01-01

    The noise characteristics of a cooled CCD device induced by neutron and gamma ray irradiation have been investigated. In the cooled CCD images, characteristic white spot noises (CCD noise) frequently appeared, which have a shape like a pixel in most cases and their brightness is extremely high compared with that of the image pattern. They could be divided into the two groups, fixed pattern noise (FPN) and random noise. The former always appeared in the same position in the image and the latter appeared at any position. In the background image, nearly all of the CCD noises were found to be the FPN, while many of them were the random noise during the irradiation. The random CCD noises increased with irradiation and decreased soon after the irradiation. In the case of large irradiation, a part of the CCD noise remained as the FPN. These facts suggest that the CCD noise is a phenomenon strongly relating to radiation damage of the CCD device.

  1. Noise simulation in cone beam CT imaging with parallel computing

    International Nuclear Information System (INIS)

    Tu, S.-J.; Shaw, Chris C; Chen, Lingyun

    2006-01-01

    We developed a computer noise simulation model for cone beam computed tomography imaging using a general purpose PC cluster. This model uses a mono-energetic x-ray approximation and allows us to investigate three primary performance components, specifically quantum noise, detector blurring and additive system noise. A parallel random number generator based on the Weyl sequence was implemented in the noise simulation and a visualization technique was accordingly developed to validate the quality of the parallel random number generator. In our computer simulation model, three-dimensional (3D) phantoms were mathematically modelled and used to create 450 analytical projections, which were then sampled into digital image data. Quantum noise was simulated and added to the analytical projection image data, which were then filtered to incorporate flat panel detector blurring. Additive system noise was generated and added to form the final projection images. The Feldkamp algorithm was implemented and used to reconstruct the 3D images of the phantoms. A 24 dual-Xeon PC cluster was used to compute the projections and reconstructed images in parallel with each CPU processing 10 projection views for a total of 450 views. Based on this computer simulation system, simulated cone beam CT images were generated for various phantoms and technique settings. Noise power spectra for the flat panel x-ray detector and reconstructed images were then computed to characterize the noise properties. As an example among the potential applications of our noise simulation model, we showed that images of low contrast objects can be produced and used for image quality evaluation

  2. Extra phase noise from thermal fluctuations in nonlinear optical crystals

    DEFF Research Database (Denmark)

    César, J. E. S.; Coelho, A.S.; Cassemiro, K.N.

    2009-01-01

    We show theoretically and experimentally that scattered light by thermal phonons inside a second-order nonlinear crystal is the source of additional phase noise observed in optical parametric oscillators. This additional phase noise reduces the quantum correlations and has hitherto hindered the d...

  3. Hot Spots Detection of Operating PV Arrays through IR Thermal Image Using Method Based on Curve Fitting of Gray Histogram

    Directory of Open Access Journals (Sweden)

    Jiang Lin

    2016-01-01

    Full Text Available The overall efficiency of PV arrays is affected by hot spots which should be detected and diagnosed by applying responsible monitoring techniques. The method using the IR thermal image to detect hot spots has been studied as a direct, noncontact, nondestructive technique. However, IR thermal images suffer from relatively high stochastic noise and non-uniformity clutter, so the conventional methods of image processing are not effective. The paper proposes a method to detect hotspots based on curve fitting of gray histogram. The result of MATLAB simulation proves the method proposed in the paper is effective to detect the hot spots suppressing the noise generated during the process of image acquisition.

  4. Noise Reduction Effect of Multiple-Sampling-Based Signal-Readout Circuits for Ultra-Low Noise CMOS Image Sensors

    Directory of Open Access Journals (Sweden)

    Shoji Kawahito

    2016-11-01

    Full Text Available This paper discusses the noise reduction effect of multiple-sampling-based signal readout circuits for implementing ultra-low-noise image sensors. The correlated multiple sampling (CMS technique has recently become an important technology for high-gain column readout circuits in low-noise CMOS image sensors (CISs. This paper reveals how the column CMS circuits, together with a pixel having a high-conversion-gain charge detector and low-noise transistor, realizes deep sub-electron read noise levels based on the analysis of noise components in the signal readout chain from a pixel to the column analog-to-digital converter (ADC. The noise measurement results of experimental CISs are compared with the noise analysis and the effect of noise reduction to the sampling number is discussed at the deep sub-electron level. Images taken with three CMS gains of two, 16, and 128 show distinct advantage of image contrast for the gain of 128 (noise(median: 0.29 e−rms when compared with the CMS gain of two (2.4 e−rms, or 16 (1.1 e−rms.

  5. Thermal imaging in medicine

    Directory of Open Access Journals (Sweden)

    Jaka Ogorevc

    2015-12-01

    Full Text Available AbstractIntroduction: Body temperature monitoring is one of the oldest and still one of the most basic diagnostic methods in medicine. In recent years thermal imaging has been increasingly used in measurements of body temperature for diagnostic purposes. Thermal imaging is non-invasive, non-contact method for measuring surface body temperature. Method is quick, painless and patient is not exposed to ionizing radiation or any other body burden.Application of thermal imaging in medicine: Pathological conditions can be indicated as hyper- or hypothermic patterns in many cases. Thermal imaging is presented as a diagnostic method, which can detect such thermal anomalies. This article provides an overview of the thermal imaging applications in various fields of medicine. Thermal imaging has proven to be a suitable method for human febrile temperature screening, for the detection of sites of fractures and infections, a reliable diagnostic tool in the detection of breast cancer and determining the type of skin cancer tumour. It is useful in monitoring the course of a therapy after spinal cord injury, in the detection of food allergies and detecting complications at hemodialysis and is also very effective at the course of treatment of breast reconstruction after mastectomy. With thermal imaging is possible to determine the degrees of burns and early detection of osteomyelitis in diabetic foot phenomenon. The most common and the oldest application of thermal imaging in medicine is the field of rheumatology.Recommendations for use and standards: Essential performance of a thermal imaging camera, measurement method, preparation of a patient and environmental conditions are very important for proper interpretation of measurement results in medical applications of thermal imaging. Standard for screening thermographs was formed for the human febrile temperature screening application.Conclusion: Based on presented examples it is shown that thermal imaging can

  6. Training Methods for Image Noise Level Estimation on Wavelet Components

    Directory of Open Access Journals (Sweden)

    A. De Stefano

    2004-12-01

    Full Text Available The estimation of the standard deviation of noise contaminating an image is a fundamental step in wavelet-based noise reduction techniques. The method widely used is based on the mean absolute deviation (MAD. This model-based method assumes specific characteristics of the noise-contaminated image component. Three novel and alternative methods for estimating the noise standard deviation are proposed in this work and compared with the MAD method. Two of these methods rely on a preliminary training stage in order to extract parameters which are then used in the application stage. The sets used for training and testing, 13 and 5 images, respectively, are fully disjoint. The third method assumes specific statistical distributions for image and noise components. Results showed the prevalence of the training-based methods for the images and the range of noise levels considered.

  7. Noise removal in multichannel image data by a parametric maximum noise fraction estimator

    DEFF Research Database (Denmark)

    Conradsen, Knut; Ersbøll, Bjarne Kjær; Nielsen, Allan Aasbjerg

    1991-01-01

    Some approaches to noise removal in multispectral imagery are presented. The primary contribution of the present work is the establishment of several ways of estimating the noise covariance matrix from image data and a comparison of the noise separation performances. A case study with Landsat MSS...

  8. Improved Denoising via Poisson Mixture Modeling of Image Sensor Noise.

    Science.gov (United States)

    Zhang, Jiachao; Hirakawa, Keigo

    2017-04-01

    This paper describes a study aimed at comparing the real image sensor noise distribution to the models of noise often assumed in image denoising designs. A quantile analysis in pixel, wavelet transform, and variance stabilization domains reveal that the tails of Poisson, signal-dependent Gaussian, and Poisson-Gaussian models are too short to capture real sensor noise behavior. A new Poisson mixture noise model is proposed to correct the mismatch of tail behavior. Based on the fact that noise model mismatch results in image denoising that undersmoothes real sensor data, we propose a mixture of Poisson denoising method to remove the denoising artifacts without affecting image details, such as edge and textures. Experiments with real sensor data verify that denoising for real image sensor data is indeed improved by this new technique.

  9. Optimal Scale Edge Detection Utilizing Noise within Images

    Directory of Open Access Journals (Sweden)

    Adnan Khashman

    2003-04-01

    Full Text Available Edge detection techniques have common problems that include poor edge detection in low contrast images, speed of recognition and high computational cost. An efficient solution to the edge detection of objects in low to high contrast images is scale space analysis. However, this approach is time consuming and computationally expensive. These expenses can be marginally reduced if an optimal scale is found in scale space edge detection. This paper presents a new approach to detecting objects within images using noise within the images. The novel idea is based on selecting one optimal scale for the entire image at which scale space edge detection can be applied. The selection of an ideal scale is based on the hypothesis that "the optimal edge detection scale (ideal scale depends on the noise within an image". This paper aims at providing the experimental evidence on the relationship between the optimal scale and the noise within images.

  10. Monocrystalline fibres for low thermal noise suspension in advanced gravitational wave detectors

    International Nuclear Information System (INIS)

    Amico, P; Bosi, L; Gammaitoni, L; Losurdo, G; Marchesoni, F; Mazzoni, M; Parisi, D; Punturo, M; Stanga, R; Toncelli, A; Tonelli, M; Travasso, F; Vetrano, F; Vocca, H

    2004-01-01

    Thermal noise in mirror suspension will be the most severe fundamental limit to the low-frequency sensitivity of future interferometric gravitational wave detectors. We propose a new type of materials to realize low thermal noise suspension in such detectors. Monocrystalline suspension fibres are good candidates both for cryogenic and for ambient temperature interferometers. Material characteristics and a production facility are described in this paper

  11. Monocrystalline fibres for low thermal noise suspension in advanced gravitational wave detectors

    Energy Technology Data Exchange (ETDEWEB)

    Amico, P [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy); Bosi, L [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy); Gammaitoni, L [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy); Losurdo, G [Istituto Nazionale di Fisica Nucleare, Sezione di Firenze/Urbino, Florence (Italy); Marchesoni, F [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy); Mazzoni, M [Istituto Nazionale di Fisica Nucleare, Sezione di Firenze/Urbino, Florence (Italy); Parisi, D [NEST-Dipartimento di Fisica, Universita di Pisa, Pisa (Italy); Punturo, M [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy); Stanga, R [Istituto Nazionale di Fisica Nucleare, Sezione di Firenze/Urbino, Florence (Italy); Toncelli, A [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa (Italy); Tonelli, M [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa (Italy); Travasso, F [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy); Vetrano, F [Istituto Nazionale di Fisica Nucleare, Sezione di Firenze/Urbino, Florence (Italy); Vocca, H [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Virgo Project, I-06100 Perugia (Italy)

    2004-03-07

    Thermal noise in mirror suspension will be the most severe fundamental limit to the low-frequency sensitivity of future interferometric gravitational wave detectors. We propose a new type of materials to realize low thermal noise suspension in such detectors. Monocrystalline suspension fibres are good candidates both for cryogenic and for ambient temperature interferometers. Material characteristics and a production facility are described in this paper.

  12. Study of the thermal noise caused by inhomogeneously distributed loss

    CERN Document Server

    Yamamoto, K; Ando, M; Kawabe, K; Tsubono, K

    2002-01-01

    The normal modal expansion is the most frequently used method to estimate the thermal noise of interferometric gravitational wave detectors. However, the method does not agree with new estimation methods, direct approaches, when the loss is distributed inhomogeneously. We have checked the modal expansion and direct approaches experimentally using a mechanical oscillator, such as a mirror. The experiments showed that the modal expansion is invalid. On the other hand, the measured spectra are consistent with the direct approaches. We calculated the thermal noise of a real mirror with inhomogeneous loss using the direct approaches. This calculation showed that the thermal motions caused by loss in the reflective coating and at coil-magnet actuators are comparable with the sensitivity goals of future gravitational wave detector projects. In addition, according to our calculation, a mechanical loss may cause much larger or much smaller thermal motion than is expected in modal expansion, depending on the loss distr...

  13. Hot Shoes in the Room: Authentication of Thermal Imaging for Quantitative Forensic Analysis

    Directory of Open Access Journals (Sweden)

    Justin H. J. Chua

    2018-01-01

    Full Text Available Thermal imaging has been a mainstay of military applications and diagnostic engineering. However, there is currently no formalised procedure for the use of thermal imaging capable of standing up to judicial scrutiny. Using a scientifically sound characterisation method, we describe the cooling function of three common shoe types at an ambient room temperature of 22 °C (295 K based on the digital output of a consumer-grade FLIR i50 thermal imager. Our method allows the reliable estimation of cooling time from pixel intensity values within a time interval of 3 to 25 min after shoes have been removed. We found a significant linear relationship between pixel intensity level and temperature. The calibration method allows the replicable determination of independent thermal cooling profiles for objects without the need for emissivity values associated with non-ideal black-body thermal radiation or system noise functions. The method has potential applications for law enforcement and forensic research, such as cross-validating statements about time spent by a person in a room. The use of thermal images can thus provide forensic scientists, law enforcement officials, and legislative bodies with an efficient and cost-effective tool for obtaining and interpreting time-based evidence.

  14. Self-noise in interferometers - radio and infrared

    International Nuclear Information System (INIS)

    Kulkarni, S.R.

    1989-01-01

    A complete theory of noise in a synthesis image is proposed for a source of arbitrary strength. In the limit of faint sources, the standard estimates of noise in a synthesis image are recovered, while in the limit of strong sources, the noise in the synthesis image is found to be dominated by either self noise or by the noise generated by the source signal itself. It is found that the best VLBI maps (with noise approaching the thermal noise) may in fact be limited by self noise, and that there is a negligible bias in the standard definitions of the bispectrum phasor and the closure phase. The results suggest that at the low signal levels which are characteristic of infrared interferometers, it is best to fit the model to all the closure phases and fringe amplitudes. 13 refs

  15. Thermal noise in mid-infrared broadband upconversion detectors

    DEFF Research Database (Denmark)

    Barh, Ajanta; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2018-01-01

    Low noise detection with state-of-the-art mid-infrared (MIR) detectors (e.g., PbS, PbSe, InSb, HgCdTe) is a primary challenge owing to the intrinsic thermal background radiation of the low bandgap detector material itself. However, researchers have employed frequency upconversion based detectors...... of the noise-equivalent power of an UCD system. In this article, we rigorously analyze the optical power generated by frequency upconversion of the intrinsic black-body radiation in the nonlinear material itself due to the crystals residual emissivity, i.e. absorption. The thermal radiation is particularly...... prominent at the optical absorption edge of the nonlinear material even at room temperature. We consider a conventional periodically poled lithium niobate (PPLN) based MIR-UCD for the investigation. The UCD is designed to cover a broad spectral range, overlapping with the entire absorption edge of the PPLN...

  16. Subcutaneous Tissue Thickness is an Independent Predictor of Image Noise in Cardiac CT

    Energy Technology Data Exchange (ETDEWEB)

    Staniak, Henrique Lane; Sharovsky, Rodolfo [Hospital Universitário - Universidade de São Paulo, São Paulo, SP (Brazil); Pereira, Alexandre Costa [Hospital das Clínicas - Universidade de São Paulo, São Paulo, SP (Brazil); Castro, Cláudio Campi de; Benseñor, Isabela M.; Lotufo, Paulo A. [Hospital Universitário - Universidade de São Paulo, São Paulo, SP (Brazil); Faculdade de Medicina - Universidade de São Paulo, São Paulo, SP (Brazil); Bittencourt, Márcio Sommer, E-mail: msbittencourt@mail.harvard.edu [Hospital Universitário - Universidade de São Paulo, São Paulo, SP (Brazil)

    2014-01-15

    Few data on the definition of simple robust parameters to predict image noise in cardiac computed tomography (CT) exist. To evaluate the value of a simple measure of subcutaneous tissue as a predictor of image noise in cardiac CT. 86 patients underwent prospective ECG-gated coronary computed tomographic angiography (CTA) and coronary calcium scoring (CAC) with 120 kV and 150 mA. The image quality was objectively measured by the image noise in the aorta in the cardiac CTA, and low noise was defined as noise < 30HU. The chest anteroposterior diameter and lateral width, the image noise in the aorta and the skin-sternum (SS) thickness were measured as predictors of cardiac CTA noise. The association of the predictors and image noise was performed by using Pearson correlation. The mean radiation dose was 3.5 ± 1.5 mSv. The mean image noise in CT was 36.3 ± 8.5 HU, and the mean image noise in non-contrast scan was 17.7 ± 4.4 HU. All predictors were independently associated with cardiac CTA noise. The best predictors were SS thickness, with a correlation of 0.70 (p < 0.001), and noise in the non-contrast images, with a correlation of 0.73 (p < 0.001). When evaluating the ability to predict low image noise, the areas under the ROC curve for the non-contrast noise and for the SS thickness were 0.837 and 0.864, respectively. Both SS thickness and CAC noise are simple accurate predictors of cardiac CTA image noise. Those parameters can be incorporated in standard CT protocols to adequately adjust radiation exposure.

  17. Subcutaneous Tissue Thickness is an Independent Predictor of Image Noise in Cardiac CT

    International Nuclear Information System (INIS)

    Staniak, Henrique Lane; Sharovsky, Rodolfo; Pereira, Alexandre Costa; Castro, Cláudio Campi de; Benseñor, Isabela M.; Lotufo, Paulo A.; Bittencourt, Márcio Sommer

    2014-01-01

    Few data on the definition of simple robust parameters to predict image noise in cardiac computed tomography (CT) exist. To evaluate the value of a simple measure of subcutaneous tissue as a predictor of image noise in cardiac CT. 86 patients underwent prospective ECG-gated coronary computed tomographic angiography (CTA) and coronary calcium scoring (CAC) with 120 kV and 150 mA. The image quality was objectively measured by the image noise in the aorta in the cardiac CTA, and low noise was defined as noise < 30HU. The chest anteroposterior diameter and lateral width, the image noise in the aorta and the skin-sternum (SS) thickness were measured as predictors of cardiac CTA noise. The association of the predictors and image noise was performed by using Pearson correlation. The mean radiation dose was 3.5 ± 1.5 mSv. The mean image noise in CT was 36.3 ± 8.5 HU, and the mean image noise in non-contrast scan was 17.7 ± 4.4 HU. All predictors were independently associated with cardiac CTA noise. The best predictors were SS thickness, with a correlation of 0.70 (p < 0.001), and noise in the non-contrast images, with a correlation of 0.73 (p < 0.001). When evaluating the ability to predict low image noise, the areas under the ROC curve for the non-contrast noise and for the SS thickness were 0.837 and 0.864, respectively. Both SS thickness and CAC noise are simple accurate predictors of cardiac CTA image noise. Those parameters can be incorporated in standard CT protocols to adequately adjust radiation exposure

  18. Suspension-thermal noise in spring–antispring systems for future gravitational-wave detectors

    Science.gov (United States)

    Harms, Jan; Mow-Lowry, Conor M.

    2018-01-01

    Spring–antispring systems have been investigated in the context of low-frequency seismic isolation in high-precision optical experiments. These systems provide the possibility to tune the fundamental resonance frequency to, in principle, arbitrarily low values, and at the same time maintain a compact design. It was argued though that thermal noise in spring–antispring systems would not be as small as one may naively expect from lowering the fundamental resonance frequency. In this paper, we present calculations of suspension-thermal noise for spring–antispring systems potentially relevant in future gravitational-wave detectors, i.e. the beam-balance tiltmeter, and the Roberts linkage. We find a concise expression of the suspension-thermal noise spectrum, which assumes a form very similar to the well-known expression for a simple pendulum. For systems such as the Roberts linkage foreseen as passive seismic isolation, we find that while they can provide strong seismic isolation due to a very low fundamental resonance frequency, their thermal noise is determined by the dimension of the system and is insensitive to fine-tunings of the geometry that can strongly influence the resonance frequency. By analogy, i.e. formal similarity of the equations of motion, this is true for all horizontal mechanical isolation systems with spring–antispring dynamics. This imposes strict requirements on mechanical spring–antispring systems for seismic isolation in potential future low-frequency gravitational-wave detectors as we discuss for the four main concepts, atom-interferometric, superconducting, torsion-bars, and conventional laser interferometer, and generally suggests that thermal noise needs to be evaluated carefully for high-precision experiments implementing spring–antispring dynamics.

  19. Noise removal for medical X-ray images in wavelet domain

    International Nuclear Information System (INIS)

    Wang, Ling; Lu, Jianming; Li, Yeqiu; Yahagi, Takashi; Okamoto, Takahide

    2006-01-01

    Many important problems in engineering and science are well-modeled by Poisson noise, the noise of medical X-ray image is Poisson noise. In this paper, we propose a method of noise removal for degraded medical X-ray image using improved preprocessing and improved BayesShrink (IBS) method in wavelet domain. Firstly, we pre-process the medical X-ray image, Secondly, we apply the Daubechies (db) wavelet transform to medical X-ray image to acquire scaling and wavelet coefficients. Thirdly, we apply the proposed IBS method to process wavelet coefficients. Finally, we compute the inverse wavelet transform for the thresholded coefficeints. Experimental results show that the proposed method always outperforms traditional methods. (author)

  20. Analysis and reduction of thermal magnetic noise in liquid-He dewar for sensitive low-field nuclear magnetic resonance measurements

    International Nuclear Information System (INIS)

    Hwang, S. M.; Yu, K. K.; Lee, Y. H.; Kang, C. S.; Kim, K.; Lee, S. J.

    2013-01-01

    For sensitive measurements of micro-Tesla nuclear magnetic resonance (μT-NMR) signal, a low-noise superconducting quantum interference device (SQUID) system is needed. We have fabricated a liquid He dewar for an SQUID having a large diameter for the pickup coil. The initial test of the SQUID system showed much higher low-frequency magnetic noise caused by the thermal magnetic noise of the aluminum plates used for the vapor-cooled thermal shield material. The frequency dependence of the noise spectrum showed that the noise increases with the decrease of frequency. This behavior could be explained from a two-layer model; one generating the thermal noise and the other one shielding the thermal noise by eddy-current shielding. And the eddy-current shielding effect is strongly dependent on the frequency through the skin-depth. To minimize the loop size for the fluctuating thermal noise current, we changed the thermal shield material into insulated thin Cu mesh. The magnetic noise of the SQUID system became flat down to 0.1 Hz with a white noise of 0.3 fT√ Hz, including the other noise contributions such as SQUID electronics and magnetically shielded room, etc, which is acceptable for low-noise μT-NMR experiments.

  1. Optimization of the GOES-1 Imagers radiometric accuracy: Drift and 1/f noise suppression

    International Nuclear Information System (INIS)

    Bremer, J.C.; Comeyne, G.J. III

    1994-01-01

    The raw output of many scanning radiometers is a small, rapidly varying signal superimposed on a large background that varies more slowly, due to thermal drifts and 1/f noise. To isolate the signal, it is necessary to perform a differential measurement: measure a known reference and subtract it from each of the raw outputs, canceling the common-mode background. Calibration is also a differential measurement: the difference between two outputs is divided by the difference between the two known references that produced them to determine the gain. The GOES-I Imager views space as its background subtraction reference and a full-aperture blackbody as its second reference for calibration. The background suppression efficiency of a differential measurement algorithm depends on its timing. The Imager measures space references before and after each scan line and performs interpolated background subtraction: a unique, linearly weighted average of the two references is subtracted from each scene sample in that line, canceling both constant bias and linear drift. One model quantifies the Gaussian noise and 1/f noise terms in the noise equivalent bandwidth, which is minimized to optimize the algorithm. The authors have obtained excellent agreement between the analytical predictions and Monte Carlo computer simulations

  2. Operation of transition-edge sensors with excess thermal noise

    International Nuclear Information System (INIS)

    Maasilta, I J; Kinnunen, K M; Nuottajaervi, A K; Leppaeniemi, J; Luukanen, A

    2006-01-01

    The superconducting transition-edge sensor (TES) is currently one of the most attractive choices for ultra-high resolution calorimetry in the keV x-ray band, and is being considered for future ESA and NASA missions. We have performed a study on the noise characteristics of Au/Ti bilayer TESs, at operating temperatures around ∼100 mK, with the SQUID readout at 1.5 K. Experimental results indicate that without modifications the back-action noise from the SQUID chip degrades the noise characteristics significantly. We present a simple and effective solution to the problem: by installing an extra shunt resistor which absorbs the excess radiation from the SQUID input, we have reduced the excess thermal (photon) noise power down by approximately a factor of five, allowing high resolution operation of the sensors

  3. Detection of low-contrast images in film-grain noise.

    Science.gov (United States)

    Naderi, F; Sawchuk, A A

    1978-09-15

    When low contrast photographic images are digitized by a very small aperture, extreme film-grain noise almost completely obliterates the image information. Using a large aperture to average out the noise destroys the fine details of the image. In these situations conventional statistical restoration techniques have little effect, and well chosen heuristic algorithms have yielded better results. In this paper we analyze the noisecheating algorithm of Zweig et al. [J. Opt. Soc. Am. 65, 1347 (1975)] and show that it can be justified by classical maximum-likelihood detection theory. A more general algorithm applicable to a broader class of images is then developed by considering the signal-dependent nature of film-grain noise. Finally, a Bayesian detection algorithm with improved performance is presented.

  4. Regularized Pre-image Estimation for Kernel PCA De-noising

    DEFF Research Database (Denmark)

    Abrahamsen, Trine Julie; Hansen, Lars Kai

    2011-01-01

    The main challenge in de-noising by kernel Principal Component Analysis (PCA) is the mapping of de-noised feature space points back into input space, also referred to as “the pre-image problem”. Since the feature space mapping is typically not bijective, pre-image estimation is inherently illposed...

  5. Interaction of image noise, spatial resolution, and low contrast fine detail preservation in digital image processing

    Science.gov (United States)

    Artmann, Uwe; Wueller, Dietmar

    2009-01-01

    We present a method to improve the validity of noise and resolution measurements on digital cameras. If non-linear adaptive noise reduction is part of the signal processing in the camera, the measurement results for image noise and spatial resolution can be good, while the image quality is low due to the loss of fine details and a watercolor like appearance of the image. To improve the correlation between objective measurement and subjective image quality we propose to supplement the standard test methods with an additional measurement of the texture preserving capabilities of the camera. The proposed method uses a test target showing white Gaussian noise. The camera under test reproduces this target and the image is analyzed. We propose to use the kurtosis of the derivative of the image as a metric for the texture preservation of the camera. Kurtosis is a statistical measure for the closeness of a distribution compared to the Gaussian distribution. It can be shown, that the distribution of digital values in the derivative of the image showing the chart becomes the more leptokurtic (increased kurtosis) the stronger the noise reduction has an impact on the image.

  6. Effects of injected dose, BMI and scanner type on NECR and image noise in PET imaging

    International Nuclear Information System (INIS)

    Chang Tingting; Chang Guoping; Clark, John W Jr; Kohlmyer, Steve; Rohren, Eric; Mawlawi, Osama R

    2011-01-01

    Noise equivalent count rate (NECR) and image noise are two different but related metrics that have been used to predict and assess image quality, respectively. The aim of this study is to investigate, using patient studies, the relationships between injected dose (ID), body mass index (BMI) and scanner type on NECR and image noise measurements in PET imaging. Two groups of 90 patients each were imaged on a GE DSTE and a DRX PET/CT scanner, respectively. The patients in each group were divided into nine subgroups according to three BMI (20-24.9, 25-29.9, 30-45 kg m -2 ) and three ID (296-444, 444-555, 555-740 MBq) ranges, resulting in ten patients/subgroup. All PET data were acquired in 3D mode and reconstructed using the VuePoint HD (registered) fully 3D OSEM algorithm (2 iterations, 21(DRX) or 20 (DSTE) subsets). NECR and image noise measurements for bed positions covering the liver were calculated for each patient. NECR was calculated from the trues, randoms and scatter events recorded in the DICOM header of each patient study, while image noise was determined as the standard deviation of 50 non-neighboring voxels in the liver of each patient. A t-test compared the NECR and image noise for different scanners but with the same BMI and ID. An ANOVA test on the other hand was used to compare the results of patients with different BMI but the same ID and scanner type as well as different ID but the same BMI and scanner type. As expected the t-test showed a significant difference in NECR between the two scanners for all BMI and ID subgroups. However, contrary to what is expected no such findings were observed for image noise measurement. The ANOVA results showed a statistically significant difference in both NECR and image noise among the different BMI for each ID and scanner subgroup. However, there was no statistically significant difference in NECR and image noise across different ID for each BMI and scanner subgroup. Although the GE DRX PET/CT scanner has better

  7. Thermal-to-visible transducer (TVT) for thermal-IR imaging

    Science.gov (United States)

    Flusberg, Allen; Swartz, Stephen; Huff, Michael; Gross, Steven

    2008-04-01

    We have been developing a novel thermal-to-visible transducer (TVT), an uncooled thermal-IR imager that is based on a Fabry-Perot Interferometer (FPI). The FPI-based IR imager can convert a thermal-IR image to a video electronic image. IR radiation that is emitted by an object in the scene is imaged onto an IR-absorbing material that is located within an FPI. Temperature variations generated by the spatial variations in the IR image intensity cause variations in optical thickness, modulating the reflectivity seen by a probe laser beam. The reflected probe is imaged onto a visible array, producing a visible image of the IR scene. This technology can provide low-cost IR cameras with excellent sensitivity, low power consumption, and the potential for self-registered fusion of thermal-IR and visible images. We will describe characteristics of requisite pixelated arrays that we have fabricated.

  8. Multiplane wave imaging increases signal-to-noise ratio in ultrafast ultrasound imaging

    International Nuclear Information System (INIS)

    Tiran, Elodie; Deffieux, Thomas; Correia, Mafalda; Maresca, David; Osmanski, Bruno-Felix; Pernot, Mathieu; Tanter, Mickael; Sieu, Lim-Anna; Bergel, Antoine; Cohen, Ivan

    2015-01-01

    Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable.Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients.The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8  ±  0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz −1 cm −1 ). In shear wave elastography, the same multiplane wave configuration yields a 2.07  ±  0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in

  9. Trends in magnetic resonance imaging. Technical trends in MRI, noise reduction and fast imaging

    International Nuclear Information System (INIS)

    Sugimoto, Hiroshi

    2007-01-01

    At MRI examination, patients suffer the machine noise and long tight lying as well as an oppressive feeling. This paper describes the technological efforts against the former two. The noise is generated from the force (thumb-ward) to vibrate the magnetic field gradient coil according to the left-hand rule. Authors have developed a MRI machine (Pianissimo) where the coil is placed in vacuum and its actual noise level is found reduced from 105 - 112 to 84 dB(A) at 1.5T. Fast imaging to shorten the imaging time is attained by combination of parallel imaging where MR signals are into multiple high frequency receiver coils, and the usual pulse sequence imaging, which results in the increased encoding in a given time. Together with these, MR angiography and diffusion weighted imaging of abdomen for cancer examination are becoming popular as an additional MRI diagnosis, also acceptable to patients. Future progress of MRI machines conceivably accompanies the unavoidable noise increase and possibly significant magnetic effects on human body, and efforts for their reduction will be continued at patients' viewpoint. (T.I.)

  10. Measuring proton beam thermal noises on the NAP-M storage ring

    International Nuclear Information System (INIS)

    Dement'ev, E.N.; Dikanskij, N.S.; Medvedko, A.S.; Parkhomchuk, V.V.; Pestrikov, D.V.

    1980-01-01

    The data on experimental investigation of thermal noises of an asimuthally homogeneous proton beam on the NAP-M storage ring are given. The noise spectra are measured at the 5th and 8th harmonics of the ciculation frequency using pick-up electrodes. The dependencies of the noise power on the proton current for noncooled and cooled beams are presented. It is shown that as a result of electron cooling the noise power decreases by two orders and in the 0.5-10 μA current range the noise power of the cooled beam does not depend on the proton current. The noise power of the noncooled beam linearly increases with the proton current. It is also shown that with the modulation growth the noise power increases. The conclusions are made that while analyzing noises of the continuous beam in the storage ring the changes of the noise spectra due to particle interaction in the beam should be taken into account

  11. Methods and tools to detect thermal noise in fast reactors

    International Nuclear Information System (INIS)

    Motta, M.; Giovannini, R.

    1985-07-01

    The Specialists' Meeting on ''Methods and Tools to Detect Thermal Noise in Fast Reactors'' was held in Bologna on 8-10 October 1984. The meeting was hosted by the ENEA and was sponsored by the IAEA on the recommendation of the International Working Group on Fast Reactors. 17 participants attended the meeting from France, the Federal Republic of Germany, Italy, Japan, the United Kingdom, Joint Research Centre of CEC and from IAEA. The meeting was presided over by Prof. Mario Motta of Italy. The purpose of the meeting was to review and discuss methods and tools for temperature noise detection and related analysis as a potential means for detecting local blockages in fuel and blanket subassemblies and other faults in LMFBR. The meeting was divided into four technical sessions as follows: 1. National review presentations on application purposes and research activities for thermal noise detection. (5 papers); 2. Detection instruments and electronic equipment for temperature measurements in fast reactors. (5 papers); 3. Physical models. (2 papers); 4. Signal processing techniques. (3 papers). A separate abstract was prepared for each of these papers

  12. A Denoising Scheme for Randomly Clustered Noise Removal in ICCD Sensing Image

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-01-01

    Full Text Available An Intensified Charge-Coupled Device (ICCD image is captured by the ICCD image sensor in extremely low-light conditions. Its noise has two distinctive characteristics. (a Different from the independent identically distributed (i.i.d. noise in natural image, the noise in the ICCD sensing image is spatially clustered, which induces unexpected structure information; (b The pattern of the clustered noise is formed randomly. In this paper, we propose a denoising scheme to remove the randomly clustered noise in the ICCD sensing image. First, we decompose the image into non-overlapped patches and classify them into flat patches and structure patches according to if real structure information is included. Then, two denoising algorithms are designed for them, respectively. For each flat patch, we simulate multiple similar patches for it in pseudo-time domain and remove its noise by averaging all the simulated patches, considering that the structure information induced by the noise varies randomly over time. For each structure patch, we design a structure-preserved sparse coding algorithm to reconstruct the real structure information. It reconstructs each patch by describing it as a weighted summation of its neighboring patches and incorporating the weights into the sparse representation of the current patch. Based on all the reconstructed patches, we generate a reconstructed image. After that, we repeat the whole process by changing relevant parameters, considering that blocking artifacts exist in a single reconstructed image. Finally, we obtain the reconstructed image by merging all the generated images into one. Experiments are conducted on an ICCD sensing image dataset, which verifies its subjective performance in removing the randomly clustered noise and preserving the real structure information in the ICCD sensing image.

  13. The analysis and rationale behind the upgrading of existing standard definition thermal imagers to high definition

    Science.gov (United States)

    Goss, Tristan M.

    2016-05-01

    With 640x512 pixel format IR detector arrays having been on the market for the past decade, Standard Definition (SD) thermal imaging sensors have been developed and deployed across the world. Now with 1280x1024 pixel format IR detector arrays becoming readily available designers of thermal imager systems face new challenges as pixel sizes reduce and the demand and applications for High Definition (HD) thermal imaging sensors increases. In many instances the upgrading of existing under-sampled SD thermal imaging sensors into more optimally sampled or oversampled HD thermal imaging sensors provides a more cost effective and reduced time to market option than to design and develop a completely new sensor. This paper presents the analysis and rationale behind the selection of the best suited HD pixel format MWIR detector for the upgrade of an existing SD thermal imaging sensor to a higher performing HD thermal imaging sensor. Several commercially available and "soon to be" commercially available HD small pixel IR detector options are included as part of the analysis and are considered for this upgrade. The impact the proposed detectors have on the sensor's overall sensitivity, noise and resolution is analyzed, and the improved range performance is predicted. Furthermore with reduced dark currents due to the smaller pixel sizes, the candidate HD MWIR detectors are operated at higher temperatures when compared to their SD predecessors. Therefore, as an additional constraint and as a design goal, the feasibility of achieving upgraded performance without any increase in the size, weight and power consumption of the thermal imager is discussed herein.

  14. Noise and contrast detection in computed tomography images

    International Nuclear Information System (INIS)

    Faulkner, K.; Moores, B.M.

    1984-01-01

    A discrete representation of the reconstruction process is used in an analysis of noise in computed tomography (CT) images. This model is consistent with the method of data collection in actual machines. An expression is derived which predicts the variance on the measured linear attenuation coefficient of a single pixel in an image. The dependence of the variance on various CT scanner design parameters such as pixel size, slice width, scan time, number of detectors, etc., is then described. The variation of noise with sampling area is theoretically explained. These predictions are in good agreement with a set of experimental measurements made on a range of CT scanners. The equivalent sampling aperture of the CT process is determined and the effect of the reconstruction filter on the variance of the linear attenuation coefficient is also noted, in particular, the choice and its consequences for reconstructed images and noise behaviour. The theory has been extended to include contrast detail behaviour, and these predictions compare favourably with experimental measurements. The theory predicts that image smoothing will have little effect on the contrast-detail detectability behaviour of reconstructed images. (author)

  15. Noise propagation in x-ray phase-contrast imaging and computed tomography

    International Nuclear Information System (INIS)

    Nesterets, Yakov I; Gureyev, Timur E

    2014-01-01

    Three phase-retrieval algorithms, based on the transport-of-intensity equation and on the contrast transfer function for propagation-based imaging, and on the linearized geometrical optics approximation for analyser-based imaging, are investigated. The algorithms are compared in terms of their effect on propagation of noise from projection images to the corresponding phase-retrieved images and further to the computed tomography (CT) images/slices of a monomorphous object reconstructed using filtered backprojection algorithm. The comparison is carried out in terms of an integral noise characteristic, the variance, as well as in terms of a simple figure-of-merit, i.e. signal-to-noise ratio per unit dose. A gain factor is introduced that quantitatively characterizes the effect of phase retrieval on the variance of noise in the reconstructed projection images and in the axial slices of the object. Simple analytical expressions are derived for the gain factor and the signal-to-noise ratio, which indicate that the application of phase-retrieval algorithms can increase these parameters by up to two orders of magnitude compared to raw projection images and conventional CT, thus allowing significant improvement in the image quality and/or reduction of the x-ray dose delivered to the patient. (paper)

  16. Relationship of core exit-temperature noise to thermal-hydraulic conditions in PWRs

    International Nuclear Information System (INIS)

    Sweeney, F.J.; Upadhyaya, B.R.

    1983-01-01

    Core exit thermocouple temperature noise and neutron detector noise measurements were performed at the Loss of Fluid Test Facility (LOFT) reactor and a Westinghouse, 1148 MW(e) PWR to relate temperature noise to core thermal-hydraulic conditions. The noise analysis results show that the RMS of the temperature noise increases linearly with increasing core δT at LOFT and the commercial PWR. Out-of-core test loop temperature noise has shown similar behavior. The phase angle between core exit temperature noise and in-core or ex-core neutron noise is directly related to the core coolant flow velocity. However, if the thermocouple response time is slow, compared to the coolant transit time between the sensors, velocities inferred from the phase angle are lower than measured coolant flow velocities

  17. Edge enhancement and noise suppression for infrared image based on feature analysis

    Science.gov (United States)

    Jiang, Meng

    2018-06-01

    Infrared images are often suffering from background noise, blurred edges, few details and low signal-to-noise ratios. To improve infrared image quality, it is essential to suppress noise and enhance edges simultaneously. To realize it in this paper, we propose a novel algorithm based on feature analysis in shearlet domain. Firstly, as one of multi-scale geometric analysis (MGA), we introduce the theory and superiority of shearlet transform. Secondly, after analyzing the defects of traditional thresholding technique to suppress noise, we propose a novel feature extraction distinguishing image structures from noise well and use it to improve the traditional thresholding technique. Thirdly, with computing the correlations between neighboring shearlet coefficients, the feature attribute maps identifying the weak detail and strong edges are completed to improve the generalized unsharped masking (GUM). At last, experiment results with infrared images captured in different scenes demonstrate that the proposed algorithm suppresses noise efficiently and enhances image edges adaptively.

  18. The iterative shrinkage method for impulsive noise reduction from images

    International Nuclear Information System (INIS)

    Beygi, Sajjad; Kafashan, Mohammadmehdi; Bahrami, Hamid Reza; Mugler, Dale H

    2012-01-01

    In this paper, we present a novel scheme to compensate impulsive noise from images using the sparse shrinkage method. In this scheme, we assume the remaining noise after using a simple median filtering in place of corrupted pixels, found by boundary discriminative noise detection method, to be Gaussian additive noise. This assumption will later be verified by the means of simulation. Knowing that the pure image in the discrete wavelet transform (DWT) domain is a sparse vector, we define an optimization problem to minimize the l 0 -norm of the estimated image vector from the noisy one in the DWT domain. l 0 -norm makes the optimization problem a combinatorial optimization problem which is NP-hard to solve. To come up with a solution for our optimization problem, we convert the l 0 -norm problem to a continuous optimization problem which is then solved to find the estimated image with reduced noise. In the simulation and discussion part, the performance of our proposed method in reducing impulsive noise is compared to that of existing methods in the literature. We show that our proposed algorithm generally performs better in terms of both subjective and objective evaluations and is less complex. (paper)

  19. Fuzzy Logic-Based Filter for Removing Additive and Impulsive Noise from Color Images

    Science.gov (United States)

    Zhu, Yuhong; Li, Hongyang; Jiang, Huageng

    2017-12-01

    This paper presents an efficient filter method based on fuzzy logics for adaptively removing additive and impulsive noise from color images. The proposed filter comprises two parts including noise detection and noise removal filtering. In the detection part, the fuzzy peer group concept is applied to determine what type of noise is added to each pixel of the corrupted image. In the filter part, the impulse noise is deducted by the vector median filter in the CIELAB color space and an optimal fuzzy filter is introduced to reduce the Gaussian noise, while they can work together to remove the mixed Gaussian-impulse noise from color images. Experimental results on several color images proves the efficacy of the proposed fuzzy filter.

  20. How does image noise affect actual and predicted human gaze allocation in assessing image quality?

    Science.gov (United States)

    Röhrbein, Florian; Goddard, Peter; Schneider, Michael; James, Georgina; Guo, Kun

    2015-07-01

    A central research question in natural vision is how to allocate fixation to extract informative cues for scene perception. With high quality images, psychological and computational studies have made significant progress to understand and predict human gaze allocation in scene exploration. However, it is unclear whether these findings can be generalised to degraded naturalistic visual inputs. In this eye-tracking and computational study, we methodically distorted both man-made and natural scenes with Gaussian low-pass filter, circular averaging filter and Additive Gaussian white noise, and monitored participants' gaze behaviour in assessing perceived image qualities. Compared with original high quality images, distorted images attracted fewer numbers of fixations but longer fixation durations, shorter saccade distance and stronger central fixation bias. This impact of image noise manipulation on gaze distribution was mainly determined by noise intensity rather than noise type, and was more pronounced for natural scenes than for man-made scenes. We furthered compared four high performing visual attention models in predicting human gaze allocation in degraded scenes, and found that model performance lacked human-like sensitivity to noise type and intensity, and was considerably worse than human performance measured as inter-observer variance. Furthermore, the central fixation bias is a major predictor for human gaze allocation, which becomes more prominent with increased noise intensity. Our results indicate a crucial role of external noise intensity in determining scene-viewing gaze behaviour, which should be considered in the development of realistic human-vision-inspired attention models. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Cluster-cluster aggregation of Ising dipolar particles under thermal noise

    KAUST Repository

    Suzuki, Masaru; Kun, Ferenc; Ito, Nobuyasu

    2009-01-01

    The cluster-cluster aggregation processes of Ising dipolar particles under thermal noise are investigated in the dilute condition. As the temperature increases, changes in the typical structures of clusters are observed from chainlike (D1

  2. Speckle noise reduction in breast ultrasound images: SMU (srad median unsharp) approch

    International Nuclear Information System (INIS)

    Njeh, I.; Sassi, O. B.; Ben Hamida, A.; Chtourou, K.

    2011-01-01

    Image denoising has become a very essential for better information extraction from the image and mainly from so noised ones, such as ultrasound images. In certain cases, for instance in ultrasound images, the noise can restrain information which is valuable for the general practitioner. Consequently medical images are very inconsistent, and it is crucial to operate case to case. This paper presents a novel algorithm SMU (Srad Median Unsharp) for noise suppression in ultrasound breast images in order to realize a computer aided diagnosis (CAD) for breast cancer.

  3. Quasi-thermal noise spectroscopy: The art and the practice

    Science.gov (United States)

    Meyer-Vernet, N.; Issautier, K.; Moncuquet, M.

    2017-08-01

    Quasi-thermal noise spectroscopy is an efficient tool for measuring in situ macroscopic plasma properties in space, using a passive wave receiver at the ports of an electric antenna. This technique was pioneered on spinning spacecraft carrying very long dipole antennas in the interplanetary medium—like ISEE-3 and Ulysses—whose geometry approached a "theoretician's dream." The technique has been extended to other instruments in various types of plasmas on board different spacecraft and will be implemented on several missions in the near future. Such extensions require different theoretical modelizations, involving magnetized, drifting, or dusty plasmas with various particle velocity distributions and antennas being shorter, biased, or made of unequal wires. We give new analytical approximations of the plasma quasi-thermal noise (QTN) and study how the constraints of the real world in space can (or cannot) be compatible with plasma detection by QTN spectroscopy. We consider applications to the missions Wind, Cassini, BepiColombo, Solar Orbiter, and Parker Solar Probe.

  4. A Shearlet-based algorithm for quantum noise removal in low-dose CT images

    Science.gov (United States)

    Zhang, Aguan; Jiang, Huiqin; Ma, Ling; Liu, Yumin; Yang, Xiaopeng

    2016-03-01

    Low-dose CT (LDCT) scanning is a potential way to reduce the radiation exposure of X-ray in the population. It is necessary to improve the quality of low-dose CT images. In this paper, we propose an effective algorithm for quantum noise removal in LDCT images using shearlet transform. Because the quantum noise can be simulated by Poisson process, we first transform the quantum noise by using anscombe variance stabilizing transform (VST), producing an approximately Gaussian noise with unitary variance. Second, the non-noise shearlet coefficients are obtained by adaptive hard-threshold processing in shearlet domain. Third, we reconstruct the de-noised image using the inverse shearlet transform. Finally, an anscombe inverse transform is applied to the de-noised image, which can produce the improved image. The main contribution is to combine the anscombe VST with the shearlet transform. By this way, edge coefficients and noise coefficients can be separated from high frequency sub-bands effectively. A number of experiments are performed over some LDCT images by using the proposed method. Both quantitative and visual results show that the proposed method can effectively reduce the quantum noise while enhancing the subtle details. It has certain value in clinical application.

  5. Comprehensive quantification of signal-to-noise ratio and g-factor for image-based and k-space-based parallel imaging reconstructions.

    Science.gov (United States)

    Robson, Philip M; Grant, Aaron K; Madhuranthakam, Ananth J; Lattanzi, Riccardo; Sodickson, Daniel K; McKenzie, Charles A

    2008-10-01

    Parallel imaging reconstructions result in spatially varying noise amplification characterized by the g-factor, precluding conventional measurements of noise from the final image. A simple Monte Carlo based method is proposed for all linear image reconstruction algorithms, which allows measurement of signal-to-noise ratio and g-factor and is demonstrated for SENSE and GRAPPA reconstructions for accelerated acquisitions that have not previously been amenable to such assessment. Only a simple "prescan" measurement of noise amplitude and correlation in the phased-array receiver, and a single accelerated image acquisition are required, allowing robust assessment of signal-to-noise ratio and g-factor. The "pseudo multiple replica" method has been rigorously validated in phantoms and in vivo, showing excellent agreement with true multiple replica and analytical methods. This method is universally applicable to the parallel imaging reconstruction techniques used in clinical applications and will allow pixel-by-pixel image noise measurements for all parallel imaging strategies, allowing quantitative comparison between arbitrary k-space trajectories, image reconstruction, or noise conditioning techniques. (c) 2008 Wiley-Liss, Inc.

  6. Qualitative and quantitative analysis of reconstructed images using projections with noises

    International Nuclear Information System (INIS)

    Lopes, R.T.; Assis, J.T. de

    1988-01-01

    The reconstruction of a two-dimencional image from one-dimensional projections in an analytic algorithm ''convolution method'' is simulated on a microcomputer. In this work it was analysed the effects caused in the reconstructed image in function of the number of projections and noise level added to the projection data. Qualitative and quantitative (distortion and image noise) comparison were done with the original image and the reconstructed images. (author) [pt

  7. Complex noise suppression using a sparse representation and 3D filtering of images

    Science.gov (United States)

    Kravchenko, V. F.; Ponomaryov, V. I.; Pustovoit, V. I.; Palacios-Enriquez, A.

    2017-08-01

    A novel method for the filtering of images corrupted by complex noise composed of randomly distributed impulses and additive Gaussian noise has been substantiated for the first time. The method consists of three main stages: the detection and filtering of pixels corrupted by impulsive noise, the subsequent image processing to suppress the additive noise based on 3D filtering and a sparse representation of signals in a basis of wavelets, and the concluding image processing procedure to clean the final image of the errors emerged at the previous stages. A physical interpretation of the filtering method under complex noise conditions is given. A filtering block diagram has been developed in accordance with the novel approach. Simulations of the novel image filtering method have shown an advantage of the proposed filtering scheme in terms of generally recognized criteria, such as the structural similarity index measure and the peak signal-to-noise ratio, and when visually comparing the filtered images.

  8. An approach to remove impulse noise from a corrupted image

    International Nuclear Information System (INIS)

    Jin, Cong; Yan, Meng; Jin, Shu-Wei

    2013-01-01

    In this paper, we propose an efficient approach for detecting the impulse noise from corrupted images. This method is based on the principle that the feature of the digital image is usually local correlation and the feature of the impulse noise is usually located near one of the two ends of the image’s maximum and minimum gray values. After the noisy pixel has been detected by the proposed detector, a modified version of the mean filter is proposed to remove the detected impulse noise. Experimental results show that the implementation of the proposed method is simple, and it has better performance than comparison filters with regard to effective noise suppression and preservation of detail, especially when the noise ratio is very high. (paper)

  9. Turbulence, chaos and thermal noise in globally coupled Josephson junction arrays

    International Nuclear Information System (INIS)

    Dominguez, D.

    1995-03-01

    We discuss the effects of thermal noise in underdamped Josephson junction series arrays that are globally coupled through a resistive load and driven by an rf current. We study the breakdown of the law of large numbers in the turbulent phase of the Josephson arrays. This corresponds to a saturation of the broad band noise S 0 for a large number N of junctions. We find that this phenomenon is stable against thermal fluctuations below a critical temperature T cl . The behaviour of S 0 vs. T, for large N, shows three different regimes. For 0 cl , S 0 decreases when increasing T, and there is turbulence and the breakdown of the law of large numbers. For T cl c2 , S 0 is constant and the dynamics is dominated by the chaos of the individual junctions. Finally for T > T c2 , S 0 in mainly due to thermal fluctuations, since it increases linearly with T. (author). 23 refs, 6 figs

  10. Image matching in Bayer raw domain to de-noise low-light still images, optimized for real-time implementation

    Science.gov (United States)

    Romanenko, I. V.; Edirisinghe, E. A.; Larkin, D.

    2013-03-01

    Temporal accumulation of images is a well-known approach to improve signal to noise ratios of still images taken in a low light conditions. However, the complexity of known algorithms often leads to high hardware resource usage, increased memory bandwidth and computational complexity, making their practical use impossible. In our research we attempt to solve this problem with an implementation of a practical spatial-temporal de-noising algorithm, based on image accumulation. Image matching and spatial-temporal filtering was performed in Bayer RAW data space, which allowed us to benefit from predictable sensor noise characteristics, thus allowing using a range of algorithmic optimizations. The proposed algorithm accurately compensates for global and local motion and efficiently removes different kinds of noise in noisy images taken in low light conditions. In our algorithm we were able to perform global and local motion compensation in Bayer RAW data space, while preserving the resolution and effectively improving signal to noise ratios of moving objects as well as non-stationary background. The proposed algorithm is suitable for implementation in commercial grade FPGA's and capable of processing 16MP images at capturing rate (10 frames per second). The main challenge for matching between still images is the compromise between the quality of the motion prediction and the complexity of the algorithm and required memory bandwidth. Still images taken in a burst sequence must be aligned to compensate for background motion and foreground objects movements in a scene. High resolution still images coupled with significant time between successive frames can produce large displacements between images, which creates additional difficulty for image matching algorithms. In photo applications it is very important that the noise is efficiently removed in both static, and non-static background as well as in a moving objects, maintaining the resolution of the image. In our proposed

  11. Using noise inconsistencies for blind image forensics

    Czech Academy of Sciences Publication Activity Database

    Saic, Stanislav; Mahdian, Babak

    2009-01-01

    Roč. 27, č. 10 (2009), s. 1497-1503 ISSN 0262-8856 R&D Projects: GA ČR GA102/08/0470 Institutional research plan: CEZ:AV0Z10750506 Keywords : Image forensics * Digital forgery * Image tampering * Image segmentation Subject RIV: IN - Informatics, Computer Science Impact factor: 1.474, year: 2009 http://library.utia.cas.cz/separaty/2009/ZOI/saic-using%20noise%20inconsistencies%20for%20blind%20image%20forensics.pdf

  12. Noise reduction in real time x-ray images

    International Nuclear Information System (INIS)

    Tsuda, Motohisa; Kimura, Yutaro

    1986-01-01

    The signal-to-noise ratio of real-time digital X-ray imaging systems consisting of an X-ray image intensifer-television chain was investigated while concentrating on the effect of the X-ray quantum nature. Along with conventional signal accumulation, logarithmic conversion and subtraction, a new technique called the peak hold method is introduced. Theoretical and simulational studies were made with practical parameters. Theory and simulation showed good agreement. An accumulation of signal is most effective for improving the signal-to-noise ratio; the peak-hold method comes next. The peak hold method, however, offers a new image-display mode. Moreover, this method is superior to signal accumulation for specific conditions. (author)

  13. Removal of impulse noise clusters from color images with local order statistics

    Science.gov (United States)

    Ruchay, Alexey; Kober, Vitaly

    2017-09-01

    This paper proposes a novel algorithm for restoring images corrupted with clusters of impulse noise. The noise clusters often occur when the probability of impulse noise is very high. The proposed noise removal algorithm consists of detection of bulky impulse noise in three color channels with local order statistics followed by removal of the detected clusters by means of vector median filtering. With the help of computer simulation we show that the proposed algorithm is able to effectively remove clustered impulse noise. The performance of the proposed algorithm is compared in terms of image restoration metrics with that of common successful algorithms.

  14. Noise propagation in resolution modeled PET imaging and its impact on detectability

    International Nuclear Information System (INIS)

    Rahmim, Arman; Tang, Jing

    2013-01-01

    Positron emission tomography imaging is affected by a number of resolution degrading phenomena, including positron range, photon non-collinearity and inter-crystal blurring. An approach to this issue is to model some or all of these effects within the image reconstruction task, referred to as resolution modeling (RM). This approach is commonly observed to yield images of higher resolution and subsequently contrast, and can be thought of as improving the modulation transfer function. Nonetheless, RM can substantially alter the noise distribution. In this work, we utilize noise propagation models in order to accurately characterize the noise texture of reconstructed images in the presence of RM. Furthermore we consider the task of lesion or defect detection, which is highly determined by the noise distribution as quantified using the noise power spectrum. Ultimately, we use this framework to demonstrate why conventional trade-off analyses (e.g. contrast versus noise, using simplistic noise metrics) do not provide a complete picture of the impact of RM and that improved performance of RM according to such analyses does not necessarily translate to the superiority of RM in detection task performance. (paper)

  15. Comparison of de-noising techniques of scintigraphic images; Comparaison de techniques de debruitage des images scintigraphiques

    Energy Technology Data Exchange (ETDEWEB)

    Kirkove, M.; Seret, A. [Liege Univ., Imagerie Medicale Experimentale, Institut de Physique (Belgium)

    2007-05-15

    Scintigraphic images are strongly affected by Poisson noise. This article presents the results of a comparison between de-noising methods for Poisson noise according to different criteria: the gain in signal-to-noise ratio, the preservation of resolution and contrast. and the visual quality. The wavelet techniques recently developed to de-noise Poisson noise limited images are divided into two groups based on: (1) the Haar representation. 1 (2) the transformation of Poisson noise into white Gaussian noise by the Haar-Fisz transform followed by a de-noising. In this study, three variants of the first group and three variants of the second. including the adaptative Wiener filter, four types of wavelet thresholding and the Bayesian method of Pizurica were compared to Metz and Hanning filters and to Shine, a systematic noise elimination process. All these methods, except Shine, are parametric. For each of them, ranges of optimal values for the parameters were highlighted as a function of the aforementioned criteria. The intersection of ranges for the wavelet methods without thresholding was empty, and these methods were therefore not further compared quantitatively. The thresholding techniques and Shine gave the best results in resolution and contrast. The largest improvement in signal-to-noise ratio was obtained by the filters. Ideally, these filters should be accurately defined for each image. This is difficult in the clinical context. Moreover. they generate oscillation artefacts. In addition, the wavelet techniques did not bring significant improvements, and are rather slow. Therefore, Shine, which is fast and works automatically, appears to be an interesting alternative. (authors)

  16. Probing quantum and thermal noise in an interacting many-body system

    DEFF Research Database (Denmark)

    Hofferberth, S.; Lesanovsky, Igor; Schumm, Thorsten

    2008-01-01

    of the shot-to-shot variations of interference-fringe contrast for pairs of independently created one-dimensional Bose condensates. Analysing different system sizes, we observe the crossover from thermal to quantum noise, reflected in a characteristic change in the distribution functions from poissonian......The probabilistic character of the measurement process is one of the most puzzling and fascinating aspects of quantum mechanics. In many-body systems quantum-mechanical noise reveals non-local correlations of the underlying many-body states. Here, we provide a complete experimental analysis....... Furthermore, our experiments constitute the first analysis of the full distribution of quantum noise in an interacting many-body system....

  17. Decision-Based Marginal Total Variation Diffusion for Impulsive Noise Removal in Color Images

    Directory of Open Access Journals (Sweden)

    Hongyao Deng

    2017-01-01

    Full Text Available Impulsive noise removal for color images usually employs vector median filter, switching median filter, the total variation L1 method, and variants. These approaches, however, often introduce excessive smoothing and can result in extensive visual feature blurring and thus are suitable only for images with low density noise. A marginal method to reduce impulsive noise is proposed in this paper that overcomes this limitation that is based on the following facts: (i each channel in a color image is contaminated independently, and contaminative components are independent and identically distributed; (ii in a natural image the gradients of different components of a pixel are similar to one another. This method divides components into different categories based on different noise characteristics. If an image is corrupted by salt-and-pepper noise, the components are divided into the corrupted and the noise-free components; if the image is corrupted by random-valued impulses, the components are divided into the corrupted, noise-free, and the possibly corrupted components. Components falling into different categories are processed differently. If a component is corrupted, modified total variation diffusion is applied; if it is possibly corrupted, scaled total variation diffusion is applied; otherwise, the component is left unchanged. Simulation results demonstrate its effectiveness.

  18. TU-F-CAMPUS-J-05: Effect of Uncorrelated Noise Texture On Computed Tomography Quantitative Image Features

    International Nuclear Information System (INIS)

    Oliver, J; Budzevich, M; Moros, E; Zhang, G; Hunt, D

    2015-01-01

    Purpose: To investigate the relationship between quantitative image features (i.e. radiomics) and statistical fluctuations (i.e. electronic noise) in clinical Computed Tomography (CT) using the standardized American College of Radiology (ACR) CT accreditation phantom and patient images. Methods: Three levels of uncorrelated Gaussian noise were added to CT images of phantom and patients (20) acquired in static mode and respiratory tracking mode. We calculated the noise-power spectrum (NPS) of the original CT images of the phantom, and of the phantom images with added Gaussian noise with means of 50, 80, and 120 HU. Concurrently, on patient images (original and noise-added images), image features were calculated: 14 shape, 19 intensity (1st order statistics from intensity volume histograms), 18 GLCM features (2nd order statistics from grey level co-occurrence matrices) and 11 RLM features (2nd order statistics from run-length matrices). These features provide the underlying structural information of the images. GLCM (size 128x128) was calculated with a step size of 1 voxel in 13 directions and averaged. RLM feature calculation was performed in 13 directions with grey levels binning into 128 levels. Results: Adding the electronic noise to the images modified the quality of the NPS, shifting the noise from mostly correlated to mostly uncorrelated voxels. The dramatic increase in noise texture did not affect image structure/contours significantly for patient images. However, it did affect the image features and textures significantly as demonstrated by GLCM differences. Conclusion: Image features are sensitive to acquisition factors (simulated by adding uncorrelated Gaussian noise). We speculate that image features will be more difficult to detect in the presence of electronic noise (an uncorrelated noise contributor) or, for that matter, any other highly correlated image noise. This work focuses on the effect of electronic, uncorrelated, noise and future work shall

  19. Image restoration by Wiener filtering in the presence of signal-dependent noise.

    Science.gov (United States)

    Kondo, K; Ichioka, Y; Suzuki, T

    1977-09-01

    An optimum filter to restore the degraded image due to blurring and the signal-dependent noise is obtained on the basis of the theory of Wiener filtering. Computer simulations of image restoration using signal-dependent noise models are carried out. It becomes clear that the optimum filter, which makes use of a priori information on the signal-dependent nature of the noise and the spectral density of the signal and the noise showing significant spatial correlation, is potentially advantageous.

  20. Noise temperature improvement for magnetic fusion plasma millimeter wave imaging systems

    Energy Technology Data Exchange (ETDEWEB)

    Lai, J.; Domier, C. W.; Luhmann, N. C. [Department of Electrical and Computer Engineering, University of California at Davis, Davis, California 95616 (United States)

    2014-03-15

    Significant progress has been made in the imaging and visualization of magnetohydrodynamic and microturbulence phenomena in magnetic fusion plasmas [B. Tobias et al., Plasma Fusion Res. 6, 2106042 (2011)]. Of particular importance have been microwave electron cyclotron emission imaging and microwave imaging reflectometry systems for imaging T{sub e} and n{sub e} fluctuations. These instruments have employed heterodyne receiver arrays with Schottky diode mixer elements directly connected to individual antennas. Consequently, the noise temperature has been strongly determined by the conversion loss with typical noise temperatures of ∼60 000 K. However, this can be significantly improved by making use of recent advances in Monolithic Microwave Integrated Circuit chip low noise amplifiers to insert a pre-amplifier in front of the Schottky diode mixer element. In a proof-of-principle design at V-Band (50–75 GHz), significant improvement of noise temperature from the current 60 000 K to measured 4000 K has been obtained.

  1. Noise temperature improvement for magnetic fusion plasma millimeter wave imaging systems.

    Science.gov (United States)

    Lai, J; Domier, C W; Luhmann, N C

    2014-03-01

    Significant progress has been made in the imaging and visualization of magnetohydrodynamic and microturbulence phenomena in magnetic fusion plasmas [B. Tobias et al., Plasma Fusion Res. 6, 2106042 (2011)]. Of particular importance have been microwave electron cyclotron emission imaging and microwave imaging reflectometry systems for imaging T(e) and n(e) fluctuations. These instruments have employed heterodyne receiver arrays with Schottky diode mixer elements directly connected to individual antennas. Consequently, the noise temperature has been strongly determined by the conversion loss with typical noise temperatures of ~60,000 K. However, this can be significantly improved by making use of recent advances in Monolithic Microwave Integrated Circuit chip low noise amplifiers to insert a pre-amplifier in front of the Schottky diode mixer element. In a proof-of-principle design at V-Band (50-75 GHz), significant improvement of noise temperature from the current 60,000 K to measured 4000 K has been obtained.

  2. Noise temperature improvement for magnetic fusion plasma millimeter wave imaging systems

    International Nuclear Information System (INIS)

    Lai, J.; Domier, C. W.; Luhmann, N. C.

    2014-01-01

    Significant progress has been made in the imaging and visualization of magnetohydrodynamic and microturbulence phenomena in magnetic fusion plasmas [B. Tobias et al., Plasma Fusion Res. 6, 2106042 (2011)]. Of particular importance have been microwave electron cyclotron emission imaging and microwave imaging reflectometry systems for imaging T e and n e fluctuations. These instruments have employed heterodyne receiver arrays with Schottky diode mixer elements directly connected to individual antennas. Consequently, the noise temperature has been strongly determined by the conversion loss with typical noise temperatures of ∼60 000 K. However, this can be significantly improved by making use of recent advances in Monolithic Microwave Integrated Circuit chip low noise amplifiers to insert a pre-amplifier in front of the Schottky diode mixer element. In a proof-of-principle design at V-Band (50–75 GHz), significant improvement of noise temperature from the current 60 000 K to measured 4000 K has been obtained

  3. Proposed Use of Zero Bias Diode Arrays as Thermal Electric Noise Rectifiers and Non-Thermal Energy Harvesters

    Science.gov (United States)

    Valone, Thomas F.

    2009-03-01

    The well known built-in voltage potential for some select semiconductor p-n junctions and various rectifying devices is proposed to be favorable for generating DC electricity at "zero bias" (with no DC bias voltage applied) in the presence of Johnson noise or 1/f noise which originates from the quantum vacuum (Koch et al., 1982). The 1982 Koch discovery that certain solid state devices exhibit measurable quantum noise has also recently been labeled a finding of dark energy in the lab (Beck and Mackey, 2004). Tunnel diodes are a class of rectifiers that are qualified and some have been credited with conducting only because of quantum fluctuations. Microwave diodes are also good choices since many are designed for zero bias operation. A completely passive, unamplified zero bias diode converter/detector for millimeter (GHz) waves was developed by HRL Labs in 2006 under a DARPA contract, utilizing a Sb-based "backward tunnel diode" (BTD). It is reported to be a "true zero-bias diode." It was developed for a "field radiometer" to "collect thermally radiated power" (in other words, 'night vision'). The diode array mounting allows a feed from horn antenna, which functions as a passive concentrating amplifier. An important clue is the "noise equivalent power" of 1.1 pW per root hertz and the "noise equivalent temperature difference" of 10° K, which indicate sensitivity to Johnson noise (Lynch, et al., 2006). There also have been other inventions such as "single electron transistors" that also have "the highest signal to noise ratio" near zero bias. Furthermore, "ultrasensitive" devices that convert radio frequencies have been invented that operate at outer space temperatures (3 degrees above zero point: 3° K). These devices are tiny nanotech devices which are suitable for assembly in parallel circuits (such as a 2-D array) to possibly produce zero point energy direct current electricity with significant power density (Brenning et al., 2006). Photovoltaic p-n junction

  4. Estimations of Kappa parameter using quasi-thermal noise spectroscopy: Applications on Wind spacecraft

    Science.gov (United States)

    Martinović, M.

    2017-12-01

    Quasi-thermal noise (QTN) spectroscopy is an accurate technique for in situ measurements of electron density and temperature in space plasmas. The QTN spectrum has a characteristic noise peak just above the plasma frequency produced by electron quasi-thermal fluctuations, which allows a very accurate measurement of the electron density. The size and shape of the peak are determined by suprathermal electrons. Since this nonthermal electron population is well described by a generalized Lorentzian - Kappa velocity distribution, it is possible to determinate the distribution properties in the solar wind from a measured spectrum. In this work, we discuss some basic properties of the QTN spectrum dependence of the Kappa distribution parameters - total electron density, temperature and the Kappa index, giving an overview on how instrument characteristics and environment conditions affect quality of the measurements. Further on, we aim to apply the method to Wind Thermal Noise Receiver (TNR) measurements. However, the spectra observed by this instrument usually contain contributions from nonthermal phenomena, like ion acoustic waves below, or galactic noise above the plasma frequency. This is why, besides comparison of the theory with observations, work with Wind data requires development of a sophisticated algorithm that distinguish parts of the spectra that are dominated by the QTN, and therefore can be used in our study. Postulates of this algorithm, as well as major results of its implementation, are also presented.

  5. Thermal imager based on the array light sensor device of 128×128 CdHgTe-photodiodes

    Directory of Open Access Journals (Sweden)

    Reva V. P.

    2010-08-01

    Full Text Available The results of investigation of developed thermal imager for middle (3—5 µm infrared region are presented and its applications features are discussed. The thermal imager consists of cooled to 80 K 128×128 diodes focal plane array on the base of cadmium–mercury–telluride compound and cryostat with temperature checking system. The photodiode array is bonded with readout device (silicon focal processor via indium microcontacts. The measured average value of noise equivalent temperature difference was NETD= 20±4 mK (background radiation temperature T = 300 K, field of view 2θ = 180°, the cooled diaphragm was not used.

  6. Approximations to camera sensor noise

    Science.gov (United States)

    Jin, Xiaodan; Hirakawa, Keigo

    2013-02-01

    Noise is present in all image sensor data. Poisson distribution is said to model the stochastic nature of the photon arrival process, while it is common to approximate readout/thermal noise by additive white Gaussian noise (AWGN). Other sources of signal-dependent noise such as Fano and quantization also contribute to the overall noise profile. Question remains, however, about how best to model the combined sensor noise. Though additive Gaussian noise with signal-dependent noise variance (SD-AWGN) and Poisson corruption are two widely used models to approximate the actual sensor noise distribution, the justification given to these types of models are based on limited evidence. The goal of this paper is to provide a more comprehensive characterization of random noise. We concluded by presenting concrete evidence that Poisson model is a better approximation to real camera model than SD-AWGN. We suggest further modification to Poisson that may improve the noise model.

  7. Industrial application of thermal image processing and thermal control

    Science.gov (United States)

    Kong, Lingxue

    2001-09-01

    Industrial application of infrared thermography is virtually boundless as it can be used in any situations where there are temperature differences. This technology has particularly been widely used in automotive industry for process evaluation and system design. In this work, thermal image processing technique will be introduced to quantitatively calculate the heat stored in a warm/hot object and consequently, a thermal control system will be proposed to accurately and actively manage the thermal distribution within the object in accordance with the heat calculated from the thermal images.

  8. High Resolution Viscosity Measurement by Thermal Noise Detection

    Directory of Open Access Journals (Sweden)

    Felipe Aguilar Sandoval

    2015-11-01

    Full Text Available An interferometric method is implemented in order to accurately assess the thermal fluctuations of a micro-cantilever sensor in liquid environments. The power spectrum density (PSD of thermal fluctuations together with Sader’s model of the cantilever allow for the indirect measurement of the liquid viscosity with good accuracy. The good quality of the deflection signal and the characteristic low noise of the instrument allow for the detection and corrections of drawbacks due to both the cantilever shape irregularities and the uncertainties on the position of the laser spot at the fluctuating end of the cantilever. Variation of viscosity below 0.03 mPa·s was detected with the alternative to achieve measurements with a volume as low as 50 µL.

  9. Statistical characterization of speckle noise in coherent imaging systems

    Science.gov (United States)

    Yaroslavsky, Leonid; Shefler, A.

    2003-05-01

    Speckle noise imposes fundamental limitation on image quality in coherent radiation based imaging and optical metrology systems. Speckle noise phenomena are associated with properties of objects to diffusely scatter irradiation and with the fact that in recording the wave field, a number of signal distortions inevitably occur due to technical limitations inherent to hologram sensors. The statistical theory of speckle noise was developed with regard to only limited resolving power of coherent imaging devices. It is valid only asymptotically as much as the central limit theorem of the probability theory can be applied. In applications this assumption is not always applicable. Moreover, in treating speckle noise problem one should also consider other sources of the hologram deterioration. In the paper, statistical properties of speckle due to the limitation of hologram size, dynamic range and hologram signal quantization are studied by Monte-Carlo simulation for holograms recorded in near and far diffraction zones. The simulation experiments have shown that, for limited resolving power of the imaging system, widely accepted opinion that speckle contrast is equal to one holds only for rather severe level of the hologram size limitation. For moderate limitations, speckle contrast changes gradually from zero for no limitation to one for limitation to less than about 20% of hologram size. The results obtained for the limitation of the hologram sensor"s dynamic range and hologram signal quantization reveal that speckle noise due to these hologram signal distortions is not multiplicative and is directly associated with the severity of the limitation and quantization. On the base of the simulation results, analytical models are suggested.

  10. CT urography in the urinary bladder: To compare excretory phase images using a low noise index and a high noise index with adaptive noise reduction filter

    International Nuclear Information System (INIS)

    Takeyama, Nobuyuki; Hayashi, Takaki; Ohgiya, Yoshimitsu

    2011-01-01

    Background: Although CT urography (CTU) is widely used for the evaluation of the entire urinary tract, the most important drawback is the radiation exposure. Purpose: To evaluate the effect of a noise reduction filter (NRF) using a phantom and to quantitatively and qualitatively compare excretory phase (EP) images using a low noise index (NI) with those using a high NI and postprocessing NRF (pNRF). Material and Methods: Each NI value was defined for a slice thickness of 5 mm, and reconstructed images with a slice thickness of 1.25 mm were assessed. Sixty patients who were at high risk of developing bladder tumors (BT) were divided into two groups according to whether their EP images were obtained using an NI of 9.88 (29 patients; group A) or an NI of 20 and pNRF (31 patients; group B). The CT dose index volume (CTDI vol ) and the contrast-to-noise ratio (CNR) of the bladder with respect to the anterior pelvic fat were compared in both groups. Qualitative assessment of the urinary bladder for image noise, sharpness, streak artifacts, homogeneity, and the conspicuity of polypoid or sessile-shaped BTs with a short-axis diameter greater than 10 mm was performed using a 3-point scale. Results: The phantom study showed noise reduction of approximately 40% and 76% dose reduction between group A and group B. CTDI vol demonstrated a 73% reduction in group B (4.6 ± 1.1 mGy) compared with group A (16.9 ± 3.4 mGy). The CNR value was not significantly different (P = 0.60) between group A (16.1 ± 5.1) and group B (16.6 ± 7.6). Although group A was superior (P < 0.01) to group B with regard to image noise, other qualitative analyses did not show significant differences. Conclusion: EP images using a high NI and pNRF were quantitatively and qualitatively comparable to those using a low NI, except with regard to image noise

  11. Modeling of Thermal Phase Noise in a Solid Core Photonic Crystal Fiber-Optic Gyroscope.

    Science.gov (United States)

    Song, Ningfang; Ma, Kun; Jin, Jing; Teng, Fei; Cai, Wei

    2017-10-26

    A theoretical model of the thermal phase noise in a square-wave modulated solid core photonic crystal fiber-optic gyroscope has been established, and then verified by measurements. The results demonstrate a good agreement between theory and experiment. The contribution of the thermal phase noise to the random walk coefficient of the gyroscope is derived. A fiber coil with 2.8 km length is used in the experimental solid core photonic crystal fiber-optic gyroscope, showing a random walk coefficient of 9.25 × 10 -5 deg/√h.

  12. Implications of CT noise and artifacts for quantitative 99mTc SPECT/CT imaging

    International Nuclear Information System (INIS)

    Hulme, K. W.; Kappadath, S. C.

    2014-01-01

    Purpose: This paper evaluates the effects of computed tomography (CT) image noise and artifacts on quantitative single-photon emission computed-tomography (SPECT) imaging, with the aim of establishing an appropriate range of CT acquisition parameters for low-dose protocols with respect to accurate SPECT attenuation correction (AC). Methods: SPECT images of two geometric and one anthropomorphic phantom were reconstructed iteratively using CT scans acquired at a range of dose levels (CTDI vol = 0.4 to 46 mGy). Resultant SPECT image quality was evaluated by comparing mean signal, background noise, and artifacts to SPECT images reconstructed using the highest dose CT for AC. Noise injection was performed on linear-attenuation (μ) maps to determine the CT noise threshold for accurate AC. Results: High levels of CT noise (σ ∼ 200–400 HU) resulted in low μ-maps noise (σ ∼ 1%–3%). Noise levels greater than ∼10% in 140 keV μ-maps were required to produce visibly perceptible increases of ∼15% in 99m Tc SPECT images. These noise levels would be achieved at low CT dose levels (CTDI vol = 4 μGy) that are over 2 orders of magnitude lower than the minimum dose for diagnostic CT scanners. CT noise could also lower (bias) the expected μ values. The relative error in reconstructed SPECT signal trended linearly with the relative shift in μ. SPECT signal was, on average, underestimated in regions corresponding with beam-hardening artifacts in CT images. Any process that has the potential to change the CT number of a region by ∼100 HU (e.g., misregistration between CT images and SPECT images due to motion, the presence of contrast in CT images) could introduce errors in μ 140 keV on the order of 10%, that in turn, could introduce errors on the order of ∼10% into the reconstructed 99m Tc SPECT image. Conclusions: The impact of CT noise on SPECT noise was demonstrated to be negligible for clinically achievable CT parameters. Because CT dose levels that affect

  13. Spectrogram Image Analysis of Error Signals for Minimizing Impulse Noise

    Directory of Open Access Journals (Sweden)

    Jeakwan Kim

    2016-01-01

    Full Text Available This paper presents the theoretical and experimental study on the spectrogram image analysis of error signals for minimizing the impulse input noises in the active suppression of noise. Impulse inputs of some specific wave patterns as primary noises to a one-dimensional duct with the length of 1800 mm are shown. The convergence speed of the adaptive feedforward algorithm based on the least mean square approach was controlled by a normalized step size which was incorporated into the algorithm. The variations of the step size govern the stability as well as the convergence speed. Because of this reason, a normalized step size is introduced as a new method for the control of impulse noise. The spectrogram images which indicate the degree of the attenuation of the impulse input noises are considered to represent the attenuation with the new method. The algorithm is extensively investigated in both simulation and real-time control experiment. It is demonstrated that the suggested algorithm worked with a nice stability and performance against impulse noises. The results in this study can be used for practical active noise control systems.

  14. Imaging the Iceland Hotspot Track Beneath Greenland with Seismic Noise Correlations

    Science.gov (United States)

    Mordret, A.

    2017-12-01

    During the past 65 million years, the Greenland craton drifted over the Iceland hotspot; however, uncertainties in geodynamic modeling and a lack of geophysical evidence prevent an accurate reconstruction of the hotspot track. I image the Greenland lithosphere down to 300 km depth with seismic noise tomography. The hotspot track is observed as a linear high-velocity anomaly in the middle crust associated with magmatic intrusions. In the upper mantle, the remnant thermal signature of the hotspot manifests as low velocity and low viscosity bodies. This new detailed picture of the Greenland lithosphere will drive more accurate geodynamic reconstructions of tectonic plate motions and prediction of Greenland heat flow, which in turn will enable more precise estimations of the Greenland ice-sheet mass balance.

  15. On the performance of the noise power spectrum from the gain-corrected radiography images.

    Science.gov (United States)

    Kim, Dong Sik; Lee, Eunae

    2018-01-01

    Fixed pattern noise due to nonuniform amplifier gains and scintillator sensitivity should be alleviated in radiography imaging to acquire low-noise x-ray images from detectors. Here, the noise property of the detector is usually evaluated observing the noise power spectrum (NPS). A gain-correction scheme, in which uniformly illuminated images are averaged to design a gain map, can be applied to alleviate the fixed pattern noise problem. The normalized NPS (NNPS) of the gain-corrected image decreases as the number of images for the average increases and converges to an infimum, which can be achieved if the fixed pattern noise is completely removed. If we know the NNPS infimum of the detector, then we can determine the performance of the gain-corrected images compared with the achievable lower bound. We first construct an image-formation model considering the nonuniform gain and then consider two measurement methods based on subtraction and division to estimate the NNPS infimum of the detector. In order to obtain a high-precision NNPS infimum estimate, we consider a time-averaging method. For several flat-panel radiography detectors, we constructed the NNPS infimum measurements and compared them with NNPS values of the gain-corrected images. We observed that the NNPS values of the gain-corrected images approached the NNPS infimum as the number of images for the average increased.

  16. Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images

    Science.gov (United States)

    Yothers, Mitchell P.; Browder, Aaron E.; Bumm, Lloyd A.

    2017-01-01

    We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

  17. Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images.

    Science.gov (United States)

    Yothers, Mitchell P; Browder, Aaron E; Bumm, Lloyd A

    2017-01-01

    We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

  18. Assessment of physiological noise modelling methods for functional imaging of the spinal cord.

    Science.gov (United States)

    Kong, Yazhuo; Jenkinson, Mark; Andersson, Jesper; Tracey, Irene; Brooks, Jonathan C W

    2012-04-02

    The spinal cord is the main pathway for information between the central and the peripheral nervous systems. Non-invasive functional MRI offers the possibility of studying spinal cord function and central sensitisation processes. However, imaging neural activity in the spinal cord is more difficult than in the brain. A significant challenge when dealing with such data is the influence of physiological noise (primarily cardiac and respiratory), and currently there is no standard approach to account for these effects. We have previously studied the various sources of physiological noise for spinal cord fMRI at 1.5T and proposed a physiological noise model (PNM) (Brooks et al., 2008). An alternative de-noising strategy, selective averaging filter (SAF), was proposed by Deckers et al. (2006). In this study we reviewed and implemented published physiological noise correction methods at higher field (3T) and aimed to find the optimal models for gradient-echo-based BOLD acquisitions. Two general techniques were compared: physiological noise model (PNM) and selective averaging filter (SAF), along with regressors designed to account for specific signal compartments and physiological processes: cerebrospinal fluid (CSF), motion correction (MC) parameters, heart rate (HR), respiration volume per time (RVT), and the associated cardiac and respiratory response functions. Functional responses were recorded from the cervical spinal cord of 18 healthy subjects in response to noxious thermal and non-noxious punctate stimulation. The various combinations of models and regressors were compared in three ways: the model fit residuals, regression model F-tests and the number of activated voxels. The PNM was found to outperform SAF in all three tests. Furthermore, inclusion of the CSF regressor was crucial as it explained a significant amount of signal variance in the cord and increased the number of active cord voxels. Whilst HR, RVT and MC explained additional signal (noise) variance

  19. AN AMELIORATED DETECTION STATISTICS FOR ADAPTIVE MASK MEDIAN FILTRATION OF HEAVILY NOISED DIGITAL IMAGES

    Directory of Open Access Journals (Sweden)

    Geeta Hanji

    2016-11-01

    Full Text Available Noise reduction is an important area of research in image processing applications. The performance of the digital image noise filtering method primarily depends upon the accuracy of noise detection scheme. This paper presents an effective detector based, adaptive mask, median filtration of heavily noised digital images affected with fixed value (or salt and pepper impulse noise. The proposed filter presents a novel approach; an ameliorated Rank Ordered Absolute Deviation (ROAD statistics to judge whether the input pixel is noised or noise free. If a pixel is detected as corrupted, it is subjected to adaptive mask median filtration; otherwise, it is kept unchanged. Extensive experimental results and comparative performance evaluations demonstrate that the proposed filter outperforms the existing decision type, median based filters with powerful noise detectors in terms of objective performance measures and visual retrieviation accuracy.

  20. Speckle Noise Reduction for the Enhancement of Retinal Layers in Optical Coherence Tomography Images

    Directory of Open Access Journals (Sweden)

    Fereydoon Nowshiravan Rahatabad

    2015-09-01

    Full Text Available Introduction One of the most important pre-processing steps in optical coherence tomography (OCT is reducing speckle noise, resulting from multiple scattering of tissues, which degrades the quality of OCT images. Materials and Methods The present study focused on speckle noise reduction and edge detection techniques. Statistical filters with different masks and noise variances were applied on OCT and test images. Objective evaluation of both types of images was performed, using various image metrics such as peak signal-to-noise ratio (PSNR, root mean square error, correlation coefficient and elapsed time. For the purpose of recovery, Kuan filter was used as an input for edge enhancement. Also, a spatial filter was applied to improve image quality. Results The obtained results were presented as statistical tables and images. Based on statistical measures and visual quality of OCT images, Enhanced Lee filter (3×3 with a PSNR value of 43.6735 in low noise variance and Kuan filter (3×3 with a PSNR value of 37.2850 in high noise variance showed superior performance over other filters. Conclusion Based on the obtained results, by using speckle reduction filters such as Enhanced Lee and Kuan filters on OCT images, the number of compounded images, required to achieve a given image quality, could be reduced. Moreover, use of Kuan filters for promoting the edges allowed smoothing of speckle regions, while preserving image tissue texture.

  1. Evaluation of noise limits to improve image processing in soft X-ray projection microscopy.

    Science.gov (United States)

    Jamsranjav, Erdenetogtokh; Kuge, Kenichi; Ito, Atsushi; Kinjo, Yasuhito; Shiina, Tatsuo

    2017-03-03

    Soft X-ray microscopy has been developed for high resolution imaging of hydrated biological specimens due to the availability of water window region. In particular, a projection type microscopy has advantages in wide viewing area, easy zooming function and easy extensibility to computed tomography (CT). The blur of projection image due to the Fresnel diffraction of X-rays, which eventually reduces spatial resolution, could be corrected by an iteration procedure, i.e., repetition of Fresnel and inverse Fresnel transformations. However, it was found that the correction is not enough to be effective for all images, especially for images with low contrast. In order to improve the effectiveness of image correction by computer processing, we in this study evaluated the influence of background noise in the iteration procedure through a simulation study. In the study, images of model specimen with known morphology were used as a substitute for the chromosome images, one of the targets of our microscope. Under the condition that artificial noise was distributed on the images randomly, we introduced two different parameters to evaluate noise effects according to each situation where the iteration procedure was not successful, and proposed an upper limit of the noise within which the effective iteration procedure for the chromosome images was possible. The study indicated that applying the new simulation and noise evaluation method was useful for image processing where background noises cannot be ignored compared with specimen images.

  2. Design of low noise imaging system

    Science.gov (United States)

    Hu, Bo; Chen, Xiaolai

    2017-10-01

    In order to meet the needs of engineering applications for low noise imaging system under the mode of global shutter, a complete imaging system is designed based on the SCMOS (Scientific CMOS) image sensor CIS2521F. The paper introduces hardware circuit and software system design. Based on the analysis of key indexes and technologies about the imaging system, the paper makes chips selection and decides SCMOS + FPGA+ DDRII+ Camera Link as processing architecture. Then it introduces the entire system workflow and power supply and distribution unit design. As for the software system, which consists of the SCMOS control module, image acquisition module, data cache control module and transmission control module, the paper designs in Verilog language and drives it to work properly based on Xilinx FPGA. The imaging experimental results show that the imaging system exhibits a 2560*2160 pixel resolution, has a maximum frame frequency of 50 fps. The imaging quality of the system satisfies the requirement of the index.

  3. Background Registration-Based Adaptive Noise Filtering of LWIR/MWIR Imaging Sensors for UAV Applications

    Directory of Open Access Journals (Sweden)

    Byeong Hak Kim

    2017-12-01

    Full Text Available Unmanned aerial vehicles (UAVs are equipped with optical systems including an infrared (IR camera such as electro-optical IR (EO/IR, target acquisition and designation sights (TADS, or forward looking IR (FLIR. However, images obtained from IR cameras are subject to noise such as dead pixels, lines, and fixed pattern noise. Nonuniformity correction (NUC is a widely employed method to reduce noise in IR images, but it has limitations in removing noise that occurs during operation. Methods have been proposed to overcome the limitations of the NUC method, such as two-point correction (TPC and scene-based NUC (SBNUC. However, these methods still suffer from unfixed pattern noise. In this paper, a background registration-based adaptive noise filtering (BRANF method is proposed to overcome the limitations of conventional methods. The proposed BRANF method utilizes background registration processing and robust principle component analysis (RPCA. In addition, image quality verification methods are proposed that can measure the noise filtering performance quantitatively without ground truth images. Experiments were performed for performance verification with middle wave infrared (MWIR and long wave infrared (LWIR images obtained from practical military optical systems. As a result, it is found that the image quality improvement rate of BRANF is 30% higher than that of conventional NUC.

  4. Background Registration-Based Adaptive Noise Filtering of LWIR/MWIR Imaging Sensors for UAV Applications

    Science.gov (United States)

    Kim, Byeong Hak; Kim, Min Young; Chae, You Seong

    2017-01-01

    Unmanned aerial vehicles (UAVs) are equipped with optical systems including an infrared (IR) camera such as electro-optical IR (EO/IR), target acquisition and designation sights (TADS), or forward looking IR (FLIR). However, images obtained from IR cameras are subject to noise such as dead pixels, lines, and fixed pattern noise. Nonuniformity correction (NUC) is a widely employed method to reduce noise in IR images, but it has limitations in removing noise that occurs during operation. Methods have been proposed to overcome the limitations of the NUC method, such as two-point correction (TPC) and scene-based NUC (SBNUC). However, these methods still suffer from unfixed pattern noise. In this paper, a background registration-based adaptive noise filtering (BRANF) method is proposed to overcome the limitations of conventional methods. The proposed BRANF method utilizes background registration processing and robust principle component analysis (RPCA). In addition, image quality verification methods are proposed that can measure the noise filtering performance quantitatively without ground truth images. Experiments were performed for performance verification with middle wave infrared (MWIR) and long wave infrared (LWIR) images obtained from practical military optical systems. As a result, it is found that the image quality improvement rate of BRANF is 30% higher than that of conventional NUC. PMID:29280970

  5. Background Registration-Based Adaptive Noise Filtering of LWIR/MWIR Imaging Sensors for UAV Applications.

    Science.gov (United States)

    Kim, Byeong Hak; Kim, Min Young; Chae, You Seong

    2017-12-27

    Unmanned aerial vehicles (UAVs) are equipped with optical systems including an infrared (IR) camera such as electro-optical IR (EO/IR), target acquisition and designation sights (TADS), or forward looking IR (FLIR). However, images obtained from IR cameras are subject to noise such as dead pixels, lines, and fixed pattern noise. Nonuniformity correction (NUC) is a widely employed method to reduce noise in IR images, but it has limitations in removing noise that occurs during operation. Methods have been proposed to overcome the limitations of the NUC method, such as two-point correction (TPC) and scene-based NUC (SBNUC). However, these methods still suffer from unfixed pattern noise. In this paper, a background registration-based adaptive noise filtering (BRANF) method is proposed to overcome the limitations of conventional methods. The proposed BRANF method utilizes background registration processing and robust principle component analysis (RPCA). In addition, image quality verification methods are proposed that can measure the noise filtering performance quantitatively without ground truth images. Experiments were performed for performance verification with middle wave infrared (MWIR) and long wave infrared (LWIR) images obtained from practical military optical systems. As a result, it is found that the image quality improvement rate of BRANF is 30% higher than that of conventional NUC.

  6. Noise-Coupled Image Rejection Architecture of Complex Bandpass ΔΣAD Modulator

    Science.gov (United States)

    San, Hao; Kobayashi, Haruo

    This paper proposes a new realization technique of image rejection function by noise-coupling architecture, which is used for a complex bandpass ΔΣAD modulator. The complex bandpass ΔΣAD modulator processes just input I and Q signals, not image signals, and the AD conversion can be realized with low power dissipation. It realizes an asymmetric noise-shaped spectra, which is desirable for such low-IF receiver applications. However, the performance of the complex bandpass ΔΣAD modulator suffers from the mismatch between internal analog I and Q paths. I/Q path mismatch causes an image signal, and the quantization noise of the mirror image band aliases into the desired signal band, which degrades the SQNDR (Signal to Quantization Noise and Distortion Ratio) of the modulator. In our proposed modulator architecture, an extra notch for image rejection is realized by noise-coupled topology. We just add some passive capacitors and switches to the modulator; the additional integrator circuit composed of an operational amplifier in the conventional image rejection realization is not necessary. Therefore, the performance of the complex modulator can be effectively raised without additional power dissipation. We have performed simulation with MATLAB to confirm the validity of the proposed architecture. The simulation results show that the proposed architecture can achieve the realization of image-rejection effectively, and improve the SQNDR of the complex bandpass ΔΣAD modulator.

  7. Single Photon Counting Performance and Noise Analysis of CMOS SPAD-Based Image Sensors

    Science.gov (United States)

    Dutton, Neale A. W.; Gyongy, Istvan; Parmesan, Luca; Henderson, Robert K.

    2016-01-01

    SPAD-based solid state CMOS image sensors utilising analogue integrators have attained deep sub-electron read noise (DSERN) permitting single photon counting (SPC) imaging. A new method is proposed to determine the read noise in DSERN image sensors by evaluating the peak separation and width (PSW) of single photon peaks in a photon counting histogram (PCH). The technique is used to identify and analyse cumulative noise in analogue integrating SPC SPAD-based pixels. The DSERN of our SPAD image sensor is exploited to confirm recent multi-photon threshold quanta image sensor (QIS) theory. Finally, various single and multiple photon spatio-temporal oversampling techniques are reviewed. PMID:27447643

  8. Noise equalization for detection of microcalcification clusters in direct digital mammogram images.

    NARCIS (Netherlands)

    McLoughlin, K.J.; Bones, P.J.; Karssemeijer, N.

    2004-01-01

    Equalizing image noise is shown to be an important step in the automatic detection of microcalcifications in digital mammography. This study extends a well established film-screen noise equalization scheme developed by Veldkamp et al. for application to full-field digital mammogram (FFDM) images. A

  9. Mixed Gaussian-Impulse Noise Image Restoration Via Total Variation

    Science.gov (United States)

    2012-05-01

    deblurring under impulse noise ,” J. Math. Imaging Vis., vol. 36, pp. 46–53, January 2010. [5] B. Li, Q. Liu, J. Xu, and X. Luo, “A new method for removing......Several Total Variation (TV) regularization methods have recently been proposed to address denoising under mixed Gaussian and impulse noise . While

  10. Noise and signal properties in PSF-based fully 3D PET image reconstruction: an experimental evaluation

    International Nuclear Information System (INIS)

    Tong, S; Alessio, A M; Kinahan, P E

    2010-01-01

    The addition of accurate system modeling in PET image reconstruction results in images with distinct noise texture and characteristics. In particular, the incorporation of point spread functions (PSF) into the system model has been shown to visually reduce image noise, but the noise properties have not been thoroughly studied. This work offers a systematic evaluation of noise and signal properties in different combinations of reconstruction methods and parameters. We evaluate two fully 3D PET reconstruction algorithms: (1) OSEM with exact scanner line of response modeled (OSEM+LOR), (2) OSEM with line of response and a measured point spread function incorporated (OSEM+LOR+PSF), in combination with the effects of four post-reconstruction filtering parameters and 1-10 iterations, representing a range of clinically acceptable settings. We used a modified NEMA image quality (IQ) phantom, which was filled with 68 Ge and consisted of six hot spheres of different sizes with a target/background ratio of 4:1. The phantom was scanned 50 times in 3D mode on a clinical system to provide independent noise realizations. Data were reconstructed with OSEM+LOR and OSEM+LOR+PSF using different reconstruction parameters, and our implementations of the algorithms match the vendor's product algorithms. With access to multiple realizations, background noise characteristics were quantified with four metrics. Image roughness and the standard deviation image measured the pixel-to-pixel variation; background variability and ensemble noise quantified the region-to-region variation. Image roughness is the image noise perceived when viewing an individual image. At matched iterations, the addition of PSF leads to images with less noise defined as image roughness (reduced by 35% for unfiltered data) and as the standard deviation image, while it has no effect on background variability or ensemble noise. In terms of signal to noise performance, PSF-based reconstruction has a 7% improvement in

  11. Nodule detection in digital chest radiography: Part of image background acting as pure noise

    International Nuclear Information System (INIS)

    Baath, M.; Haakansson, M.; Boerjesson, S.; Kheddache, S.; Grahn, A.; Bochud, F. O.; Verdun, F. R.; Maansson, L. G.

    2005-01-01

    There are several factors that influence the radiologist's ability to detect a specific structure/lesion in a radiograph. Three factors that are commonly known to be of major importance are the signal itself, the system noise and the projected anatomy. The aim of this study was to determine to what extent the image background acts as pure noise for the detection of subtle lung nodules in five different regions of the chest. A receiver operating characteristic (ROC) study with five observers was conducted on two different sets of images, clinical chest X-ray images and images with a similar power spectrum as the clinical images but with a random phase spectrum, resulting in an image background containing pure noise. Simulated designer nodules with a full-width-at-fifth-maximum of 10 mm but with varying contrasts were added to the images. As a measure of the part of the image background that acts as pure noise, the ratio between the contrast needed to obtain an area under the ROC curve of 0.80 in the clinical images to that in the random-phase images was used. The ratio ranged from 0.40 (in the lateral pulmonary regions) to 0.83 (in the hilar regions) indicating that there was a large difference between different regions regarding to what extent the image background acted as pure noise; and that in the hilar regions the image background almost completely acted as pure noise for the detection of 10 mm nodules. (authors)

  12. M2 FILTER FOR SPECKLE NOISE SUPPRESSION IN BREAST ULTRASOUND IMAGES

    Directory of Open Access Journals (Sweden)

    E.S. Samundeeswari

    2016-11-01

    Full Text Available Breast cancer, commonly found in women is a serious life threatening disease due to its invasive nature. Ultrasound (US imaging method plays an effective role in screening early detection and diagnosis of Breast cancer. Speckle noise generally affects medical ultrasound images and also causes a number of difficulties in identifying the Region of Interest. Suppressing speckle noise is a challenging task as it destroys fine edge details. No specific filter is designed yet to get a noise free BUS image that is contaminated by speckle noise. In this paper M2 filter, a novel hybrid of linear and nonlinear filter is proposed and compared to other spatial filters with 3×3 kernel size. The performance of the proposed M2 filter is measured by statistical quantity parameters like MSE, PSNR and SSI. The experimental analysis clearly shows that the proposed M2 filter outperforms better than other spatial filters by 2% high PSNR values with regards to speckle suppression.

  13. Imperceptible reversible watermarking of radiographic images based on quantum noise masking.

    Science.gov (United States)

    Pan, Wei; Bouslimi, Dalel; Karasad, Mohamed; Cozic, Michel; Coatrieux, Gouenou

    2018-07-01

    Advances in information and communication technologies boost the sharing and remote access to medical images. Along with this evolution, needs in terms of data security are also increased. Watermarking can contribute to better protect images by dissimulating into their pixels some security attributes (e.g., digital signature, user identifier). But, to take full advantage of this technology in healthcare, one key problem to address is to ensure that the image distortion induced by the watermarking process does not endanger the image diagnosis value. To overcome this issue, reversible watermarking is one solution. It allows watermark removal with the exact recovery of the image. Unfortunately, reversibility does not mean that imperceptibility constraints are relaxed. Indeed, once the watermark removed, the image is unprotected. It is thus important to ensure the invisibility of reversible watermark in order to ensure a permanent image protection. We propose a new fragile reversible watermarking scheme for digital radiographic images, the main originality of which stands in masking a reversible watermark into the image quantum noise (the dominant noise in radiographic images). More clearly, in order to ensure the watermark imperceptibility, our scheme differentiates the image black background, where message embedding is conducted into pixel gray values with the well-known histogram shifting (HS) modulation, from the anatomical object, where HS is applied to wavelet detail coefficients, masking the watermark with the image quantum noise. In order to maintain the watermark embedder and reader synchronized in terms of image partitioning and insertion domain, our scheme makes use of different classification processes that are invariant to message embedding. We provide the theoretical performance limits of our scheme into the image quantum noise in terms of image distortion and message size (i.e. capacity). Experiments conducted on more than 800 12 bits radiographic images

  14. Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, Justin, E-mail: justin.solomon@duke.edu [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Samei, Ehsan [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 and Departments of Biomedical Engineering and Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina 27705 (United States)

    2014-09-15

    Purpose: Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE). Methods: Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms. Results: In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was

  15. Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE

    International Nuclear Information System (INIS)

    Solomon, Justin; Samei, Ehsan

    2014-01-01

    Purpose: Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE). Methods: Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms. Results: In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was

  16. Reducing image noise in computed tomography (CT) colonography: effect of an integrated circuit CT detector.

    Science.gov (United States)

    Liu, Yu; Leng, Shuai; Michalak, Gregory J; Vrieze, Thomas J; Duan, Xinhui; Qu, Mingliang; Shiung, Maria M; McCollough, Cynthia H; Fletcher, Joel G

    2014-01-01

    To investigate whether the integrated circuit (IC) detector results in reduced noise in computed tomography (CT) colonography (CTC). Three hundred sixty-six consecutive patients underwent clinically indicated CTC using the same CT scanner system, except for a difference in CT detectors (IC or conventional). Image noise, patient size, and scanner radiation output (volume CT dose index) were quantitatively compared between patient cohorts using each detector system, with separate comparisons for the abdomen and pelvis. For the abdomen and pelvis, despite significantly larger patient sizes in the IC detector cohort (both P 0.18). Based on the observed image noise reduction, radiation dose could alternatively be reduced by approximately 20% to result in similar levels of image noise. Computed tomography colonography images acquired using the IC detector had significantly lower noise than images acquired using the conventional detector. This noise reduction can permit further radiation dose reduction in CTC.

  17. Accuracy of signal-to-noise ratio measurement method for magnetic resonance images

    International Nuclear Information System (INIS)

    Ogura, Akio; Miyai, Akira; Maeda, Fumie; Fukutake, Hiroyuki; Kikumoto, Rikiya

    2003-01-01

    The signal-to-noise ratio (SNR) of a magnetic resonance image is a common measure of imager performance. However, evaluations for the calculation of the SNR use various methods. A problem with measuring SNR is caused by the distortion of noise statistics in commonly used magnitude images. In this study, measurement accuracy was compared among four methods of evaluating SNR according to the size and position of regions of interest (ROIs). The results indicated that the method that used the difference between two images showed the best agreement with the theoretical value. In the method that used a single image, the SNR calculated by using a small size of ROI showed better agreement with the theoretical value because of noise bias and image artifacts. However, in the method that used the difference between two images, a large size of ROI was better in reducing statistical errors. In the same way, the methods that used air noise and air signal were better when applied to a large ROI. In addition, the image subtraction process used to calculate pixel-by-pixel differences in images may reach zero on a minus pixel value when using an image processor with the MRI system and apparatuses associated with it. A revised equation is presented for this case. It is important to understand the characteristics of each method and to choose a suitable method carefully according to the purpose of the study. (author)

  18. Wavelet-domain de-noising of OCT images of human brain malignant glioma

    Science.gov (United States)

    Dolganova, I. N.; Aleksandrova, P. V.; Beshplav, S.-I. T.; Chernomyrdin, N. V.; Dubyanskaya, E. N.; Goryaynov, S. A.; Kurlov, V. N.; Reshetov, I. V.; Potapov, A. A.; Tuchin, V. V.; Zaytsev, K. I.

    2018-04-01

    We have proposed a wavelet-domain de-noising technique for imaging of human brain malignant glioma by optical coherence tomography (OCT). It implies OCT image decomposition using the direct fast wavelet transform, thresholding of the obtained wavelet spectrum and further inverse fast wavelet transform for image reconstruction. By selecting both wavelet basis and thresholding procedure, we have found an optimal wavelet filter, which application improves differentiation of the considered brain tissue classes - i.e. malignant glioma and normal/intact tissue. Namely, it allows reducing the scattering noise in the OCT images and retaining signal decrement for each tissue class. Therefore, the observed results reveals the wavelet-domain de-noising as a prospective tool for improved characterization of biological tissue using the OCT.

  19. Noise removal in extended depth of field microscope images through nonlinear signal processing.

    Science.gov (United States)

    Zahreddine, Ramzi N; Cormack, Robert H; Cogswell, Carol J

    2013-04-01

    Extended depth of field (EDF) microscopy, achieved through computational optics, allows for real-time 3D imaging of live cell dynamics. EDF is achieved through a combination of point spread function engineering and digital image processing. A linear Wiener filter has been conventionally used to deconvolve the image, but it suffers from high frequency noise amplification and processing artifacts. A nonlinear processing scheme is proposed which extends the depth of field while minimizing background noise. The nonlinear filter is generated via a training algorithm and an iterative optimizer. Biological microscope images processed with the nonlinear filter show a significant improvement in image quality and signal-to-noise ratio over the conventional linear filter.

  20. Does image quality matter? Impact of resolution and noise on mammographic task performance

    International Nuclear Information System (INIS)

    Saunders, Robert S. Jr.; Baker, Jay A.; Delong, David M.; Johnson, Jeff P.; Samei, Ehsan

    2007-01-01

    The purpose of this study was to examine the effects of different resolution and noise levels on task performance in digital mammography. This study created an image set with images at three different resolution levels, corresponding to three digital display devices, and three different noise levels, with noise magnitudes similar to full clinical dose, half clinical dose, and quarter clinical dose. The images were read by five experienced breast imaging radiologists. The data were then analyzed to compute two accuracy statistics (overall classification accuracy and lesion detection accuracy) and performance at four diagnostic tasks (detection of microcalcifications, benign masses, malignant masses, and discrimination of benign and malignant masses). Human observer results showed decreasing display resolution had little effect on overall classification accuracy and individual diagnostic task performance, but increasing noise caused overall classification accuracy to decrease by a statistically significant 21% as the breast dose went to one quarter of its normal clinical value. The noise effects were most prominent for the tasks of microcalcification detection and mass discrimination. When the noise changed from full clinical dose to quarter clinical dose, the microcalcification detection performance fell from 89% to 67% and the mass discrimination performance decreased from 93% to 79%, while malignant mass detection performance remained relatively constant with values of 88% and 84%, respectively. As a secondary aim, the image set was also analyzed by two observer models to examine whether their performance was similar to humans. Observer models differed from human observers and each other in their sensitivity to resolution degradation and noise. The primary conclusions of this study suggest that quantum noise appears to be the dominant image quality factor in digital mammography, affecting radiologist performance much more profoundly than display resolution

  1. Computed Tomography Image Origin Identification Based on Original Sensor Pattern Noise and 3-D Image Reconstruction Algorithm Footprints.

    Science.gov (United States)

    Duan, Yuping; Bouslimi, Dalel; Yang, Guanyu; Shu, Huazhong; Coatrieux, Gouenou

    2017-07-01

    In this paper, we focus on the "blind" identification of the computed tomography (CT) scanner that has produced a CT image. To do so, we propose a set of noise features derived from the image chain acquisition and which can be used as CT-scanner footprint. Basically, we propose two approaches. The first one aims at identifying a CT scanner based on an original sensor pattern noise (OSPN) that is intrinsic to the X-ray detectors. The second one identifies an acquisition system based on the way this noise is modified by its three-dimensional (3-D) image reconstruction algorithm. As these reconstruction algorithms are manufacturer dependent and kept secret, our features are used as input to train a support vector machine (SVM) based classifier to discriminate acquisition systems. Experiments conducted on images issued from 15 different CT-scanner models of 4 distinct manufacturers demonstrate that our system identifies the origin of one CT image with a detection rate of at least 94% and that it achieves better performance than sensor pattern noise (SPN) based strategy proposed for general public camera devices.

  2. A review on noise suppression and aberration compensation in holographic particle image velocimetry

    Directory of Open Access Journals (Sweden)

    K.F. Tamrin

    2016-12-01

    Full Text Available Understanding three-dimensional (3D fluid flow behaviour is undeniably crucial in improving performance and efficiency in a wide range of applications in engineering and medical fields. Holographic particle image velocimetry (HPIV is a potential tool to probe and characterize complex flow dynamics since it is a truly three-dimensional three-component measurement technique. The technique relies on the coherent light scattered by small seeding particles that are assumed to faithfully follow the flow for subsequent reconstruction of the same the event afterward. However, extraction of useful 3D displacement data from these particle images is usually aggravated by noise and aberration which are inherent within the optical system. Noise and aberration have been considered as major hurdles in HPIV in obtaining accurate particle image identification and its corresponding 3D position. Major contributions to noise include zero-order diffraction, out-of-focus particles, virtual image and emulsion grain scattering. Noise suppression is crucial to ensure that particle image can be distinctly differentiated from background noise while aberration compensation forms particle image with high integrity. This paper reviews a number of HPIV configurations that have been proposed to address these issues, summarizes the key findings and outlines a basis for follow-on research.

  3. Analysis and Extension of the PCA Method, Estimating a Noise Curve from a Single Image

    Directory of Open Access Journals (Sweden)

    Miguel Colom

    2016-12-01

    Full Text Available In the article 'Image Noise Level Estimation by Principal Component Analysis', S. Pyatykh, J. Hesser, and L. Zheng propose a new method to estimate the variance of the noise in an image from the eigenvalues of the covariance matrix of the overlapping blocks of the noisy image. Instead of using all the patches of the noisy image, the authors propose an iterative strategy to adaptively choose the optimal set containing the patches with lowest variance. Although the method measures uniform Gaussian noise, it can be easily adapted to deal with signal-dependent noise, which is realistic with the Poisson noise model obtained by a CMOS or CCD device in a digital camera.

  4. Spatio-temporal chaos and thermal noise in Josephson junction series arrays

    International Nuclear Information System (INIS)

    Dominguez, D.; Cerdeira, H.A.

    1995-01-01

    We study underdamped Josephson junction series arrays that are globally coupled through a resistive shunting load and driven by an rf bias current. We find that they can be an experimental realization of many phenomena currently studied in globally coupled logistic map. Depending on the bias current the array can show Shapiro steps but also spatio-temporal chaos or ''turbulence'' in the IV characteristics. In the turbulent phase there is a saturation of the broad band noise for a large number of junctions. This corresponds to a break down of the law of large numbers as seen in globally coupled maps. We study this phenomenon as a function of thermal noise. We find that when increasing the temperature the broad band noise decreases. (author). 8 refs, 1 fig

  5. Application of a Noise Adaptive Contrast Sensitivity Function to Image Data Compression

    Science.gov (United States)

    Daly, Scott J.

    1989-08-01

    The visual contrast sensitivity function (CSF) has found increasing use in image compression as new algorithms optimize the display-observer interface in order to reduce the bit rate and increase the perceived image quality. In most compression algorithms, increasing the quantization intervals reduces the bit rate at the expense of introducing more quantization error, a potential image quality degradation. The CSF can be used to distribute this error as a function of spatial frequency such that it is undetectable by the human observer. Thus, instead of being mathematically lossless, the compression algorithm can be designed to be visually lossless, with the advantage of a significantly reduced bit rate. However, the CSF is strongly affected by image noise, changing in both shape and peak sensitivity. This work describes a model of the CSF that includes these changes as a function of image noise level by using the concepts of internal visual noise, and tests this model in the context of image compression with an observer study.

  6. Impulse Noise Cancellation of Medical Images Using Wavelet Networks and Median Filters

    Science.gov (United States)

    Sadri, Amir Reza; Zekri, Maryam; Sadri, Saeid; Gheissari, Niloofar

    2012-01-01

    This paper presents a new two-stage approach to impulse noise removal for medical images based on wavelet network (WN). The first step is noise detection, in which the so-called gray-level difference and average background difference are considered as the inputs of a WN. Wavelet Network is used as a preprocessing for the second stage. The second step is removing impulse noise with a median filter. The wavelet network presented here is a fixed one without learning. Experimental results show that our method acts on impulse noise effectively, and at the same time preserves chromaticity and image details very well. PMID:23493998

  7. Thermal imaging cameras characteristics and performance

    CERN Document Server

    Williams, Thomas

    2009-01-01

    The ability to see through smoke and mist and the ability to use the variances in temperature to differentiate between targets and their backgrounds are invaluable in military applications and have become major motivators for the further development of thermal imagers. As the potential of thermal imaging is more clearly understood and the cost decreases, the number of industrial and civil applications being exploited is growing quickly. In order to evaluate the suitability of particular thermal imaging cameras for particular applications, it is important to have the means to specify and measur

  8. Suppression of thermal noise in a non-Markovian random velocity field

    International Nuclear Information System (INIS)

    Ueda, Masahiko

    2016-01-01

    We study the diffusion of Brownian particles in a Gaussian random velocity field with short memory. By extending the derivation of an effective Fokker–Planck equation for the Lanvegin equation with weakly colored noise to a random velocity-field problem, we find that the effect of thermal noise on particles is suppressed by the existence of memory. We also find that the renormalization effect for the relative diffusion of two particles is stronger than that for single-particle diffusion. The results are compared with those of molecular dynamics simulations. (paper: classical statistical mechanics, equilibrium and non-equilibrium)

  9. Wavelet theory applied to remove noise and movement artifacts from images

    International Nuclear Information System (INIS)

    Blanco, S.; Cabrejas, M.L.; Carpintiero, S.; Costa, A.; Stenborg, J.

    2002-01-01

    The quality of the images is in direct relationship with the accuracy of the diagnosis. There are several physical and technical problems (signal to noise ratio, image distortions, geometrical defects, pattern recognition and movement corrections) associated with acquisition and processing devices, each of which require specific solutions. New generation equipment or appropriate quality control techniques, often solve the problem. The option, is trying to correct for image distortions existing on the reconstructed images using post processing mathematical filtering. In this paper a new developed software is described to correct the images and solve the above mentioned problems. Mathematical tools: To improve the signal to noise ratio, a noise reduction method, based on Multi Resolution Analysis with Wavelets, was used. The use of cubic spline wavelets as mother wavelets, is more convenient because they conform an orthogonal basis. For each multi resolution level, a 'hard thresholding' was applied. This means that the coefficients, which are strongly dependent on the images, are put to zero when they are smaller than a reference value. It is also possible to separate the movement of the structures under study from instrumental constraints or noise. To accomplish this, cross-correlations of particular sub-regions, in consecutive images, were performed. Since a quantitative estimation of the error introduced by both effects is rather difficult, a new technique was developed, a so-called trial and error technique (TET), via the identification of a particular subregion on consecutive images, provided there are sharp fixed features present in the considered subregion. This position, being the one in which the standard deviation is the smallest, is then chosen on the second image. Taking into account the time between images and the dynamic characteristic time, the Gaussian distribution confirms the absence of substantial variability form one image to the other. Results

  10. Night Vision Image De-Noising of Apple Harvesting Robots Based on the Wavelet Fuzzy Threshold

    Directory of Open Access Journals (Sweden)

    Chengzhi Ruan

    2015-12-01

    Full Text Available In this paper, the de-noising problem of night vision images is studied for apple harvesting robots working at night. The wavelet threshold method is applied to the de-noising of night vision images. Due to the fact that the choice of wavelet threshold function restricts the effect of the wavelet threshold method, the fuzzy theory is introduced to construct the fuzzy threshold function. We then propose the de-noising algorithm based on the wavelet fuzzy threshold. This new method can reduce image noise interferences, which is conducive to further image segmentation and recognition. To demonstrate the performance of the proposed method, we conducted simulation experiments and compared the median filtering and the wavelet soft threshold de-noising methods. It is shown that this new method can achieve the highest relative PSNR. Compared with the original images, the median filtering de-noising method and the classical wavelet threshold de-noising method, the relative PSNR increases 24.86%, 13.95%, and 11.38% respectively. We carry out comparisons from various aspects, such as intuitive visual evaluation, objective data evaluation, edge evaluation and artificial light evaluation. The experimental results show that the proposed method has unique advantages for the de-noising of night vision images, which lay the foundation for apple harvesting robots working at night.

  11. Signal to noise ratio (SNR) and image uniformity: an estimate of performance of magnetic resonance imaging (MRI) system

    International Nuclear Information System (INIS)

    Narayan, P.; Suri, S.; Choudhary, S.R.

    2001-01-01

    In most general definition, noise in an image, is any variation that represents a deviation from truth. Noise sources in MRI can be systematic or random and statistical in nature. Data processing algorithms that smooth and enhance the edges by non-linear intensity assignments among other factors can affect the distribution of statistical noise. The SNR and image uniformity depends on the various parameters of NMR imaging system (viz. General system calibration, Gain coil tuning, AF shielding, coil loading, image processing and scan parameters like TE, TR, interslice distance, slice thickness, pixel size and matrix size). A study on SNR and image uniformity have been performed using standard head AF coil with different TR and the estimates of their variation are presented. A comparison between different techniques has also been evaluated using standard protocol of the Siemens Magnetom Vision Plus MRI system

  12. Assessment of noise in a digital image using the join-count statistic and the Moran test

    International Nuclear Information System (INIS)

    Kehshih Chuang; Huang, H.K.

    1992-01-01

    It is assumed that data bits of a pixel in digital images can be divided into signal and noise bits. The signal bits occupy the most significant part of the pixel. The signal parts of each pixel are correlated while the noise parts are uncorrelated. Two statistical methods, the Moran test and the join-count statistic, are used to examine the noise parts. Images from computerized tomography, magnetic resonance and computed radiography are used for the evaluation of the noise bits. A residual image is formed by subtracting the original image from its smoothed version. The noise level in the residual image is then identical to that in the original image. Both statistical tests are then performed on the bit planes of the residual image. Results show that most digital images contain only 8-9 bits of correlated information. Both methods are easy to implement and fast to perform. (author)

  13. [Investigation on Mobile Phone Based Thermal Imaging System and Its Preliminary Application].

    Science.gov (United States)

    Li, Fufeng; Chen, Feng; Liu, Jing

    2015-03-01

    The technical structure of a low-cost thermal imaging system (TIM) lunched on a mobile phone was investigated, which consists of a thermal infrared module and mobile phone and application software. The designing strategies and technical factors toward realizing various TIM array performances are interpreted, including sensor cost and Noise Equivalent Temperature Difference (NETD). In the software algorithm, a mechanism for scene-change detection was implemented to optimize the efficiency of non-uniformity correction (NUC). The performance experiments and analysis indicate that the NETD of the system can be smaller than 150 mK when the integration time is larger than 16 frames. Furthermore, a practical application for human temperature monitoring during physical exercise is proposed and interpreted. The measurement results support the feasibility and facility of the system in the medical application.

  14. A multi-stage noise adaptive switching filter for extremely corrupted images

    Science.gov (United States)

    Dinh, Hai; Adhami, Reza; Wang, Yi

    2015-07-01

    A multi-stage noise adaptive switching filter (MSNASF) is proposed for the restoration of images extremely corrupted by impulse and impulse-like noise. The filter consists of two steps: noise detection and noise removal. The proposed extrema-based noise detection scheme utilizes the false contouring effect to get better over detection rate at low noise density. It is adaptive and will detect not only impulse but also impulse-like noise. In the noise removal step, a novel multi-stage filtering scheme is proposed. It replaces corrupted pixel with the nearest uncorrupted median to preserve details. When compared with other methods, MSNASF provides better peak signal to noise ratio (PSNR) and structure similarity index (SSIM). A subjective evaluation carried out online also demonstrates that MSNASF yields higher fidelity.

  15. Image noise reduction algorithm for digital subtraction angiography: clinical results.

    Science.gov (United States)

    Söderman, Michael; Holmin, Staffan; Andersson, Tommy; Palmgren, Charlotta; Babic, Draženko; Hoornaert, Bart

    2013-11-01

    To test the hypothesis that an image noise reduction algorithm designed for digital subtraction angiography (DSA) in interventional neuroradiology enables a reduction in the patient entrance dose by a factor of 4 while maintaining image quality. This clinical prospective study was approved by the local ethics committee, and all 20 adult patients provided informed consent. DSA was performed with the default reference DSA program, a quarter-dose DSA program with modified acquisition parameters (to reduce patient radiation dose exposure), and a real-time noise-reduction algorithm. Two consecutive biplane DSA data sets were acquired in each patient. The dose-area product (DAP) was calculated for each image and compared. A randomized, blinded, offline reading study was conducted to show noninferiority of the quarter-dose image sets. Overall, 40 samples per treatment group were necessary to acquire 80% power, which was calculated by using a one-sided α level of 2.5%. The mean DAP with the quarter-dose program was 25.3% ± 0.8 of that with the reference program. The median overall image quality scores with the reference program were 9, 13, and 12 for readers 1, 2, and 3, respectively. These scores increased slightly to 12, 15, and 12, respectively, with the quarter-dose program imaging chain. In DSA, a change in technique factors combined with a real-time noise-reduction algorithm will reduce the patient entrance dose by 75%, without a loss of image quality. RSNA, 2013

  16. Poisson–Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain

    Science.gov (United States)

    Lee, Sangyoon; Lee, Min Seok; Kang, Moon Gi

    2018-01-01

    The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson–Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson–Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods. PMID:29596335

  17. Poisson-Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain.

    Science.gov (United States)

    Lee, Sangyoon; Lee, Min Seok; Kang, Moon Gi

    2018-03-29

    The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson-Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson-Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods.

  18. SU-G-IeP4-13: PET Image Noise Variability and Its Consequences for Quantifying Tumor Hypoxia

    Energy Technology Data Exchange (ETDEWEB)

    Kueng, R [Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario (Canada); Manser, P; Fix, M K [Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Driscoll, B; Keller, H [Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario (Canada); Stampanoni, M F M [Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology (ETH) (Switzerland)

    2016-06-15

    Purpose: The values in a PET image which represent activity concentrations of a radioactive tracer are influenced by a large number of parameters including patient conditions as well as image acquisition and reconstruction. This work investigates noise characteristics in PET images for various image acquisition and image reconstruction parameters. Methods: Different phantoms with homogeneous activity distributions were scanned using several acquisition parameters and reconstructed with numerous sets of reconstruction parameters. Images from six PET scanners from different vendors were analyzed and compared with respect to quantitative noise characteristics. Local noise metrics, which give rise to a threshold value defining the metric of hypoxic fraction, as well as global noise measures in terms of noise power spectra (NPS) were computed. In addition to variability due to different reconstruction parameters, spatial variability of activity distribution and its noise metrics were investigated. Patient data from clinical trials were mapped onto phantom scans to explore the impact of the scanner’s intrinsic noise variability on quantitative clinical analysis. Results: Local noise metrics showed substantial variability up to an order of magnitude for different reconstruction parameters. Investigations of corresponding NPS revealed reconstruction dependent structural noise characteristics. For the acquisition parameters, noise metrics were guided by Poisson statistics. Large spatial non-uniformity of the noise was observed in both axial and radial direction of a PET image. In addition, activity concentrations in PET images of homogeneous phantom scans showed intriguing spatial fluctuations for most scanners. The clinical metric of the hypoxic fraction was shown to be considerably influenced by the PET scanner’s spatial noise characteristics. Conclusion: We showed that a hypoxic fraction metric based on noise characteristics requires careful consideration of the

  19. The colour of thermal noise in classical Brownian motion: a feasibility study of direct experimental observation

    International Nuclear Information System (INIS)

    Berg-Soerensen, Kirstine; Flyvbjerg, Henrik

    2005-01-01

    One hundred years after Einstein modelled Brownian motion, a central aspect of this motion in incompressible fluids has not been verified experimentally: the thermal noise that drives the Brownian particle, is not white, as in Einstein's simple theory. It is slightly coloured, due to hydrodynamics and the fluctuation-dissipation theorem. This theoretical result from the 1970s was prompted by computer simulation results in apparent violation of Einstein's theory. We discuss how a direct experimental observation of this colour might be carried out by using optical tweezers to separate the thermal noise from the particle's dynamic response to it. Since the thermal noise is almost white, very good statistics is necessary to resolve its colour. That requires stable equipment and long recording times, possibly making this experiment one for the future only. We give results for experimental requirements and for stochastic errors as functions of experimental window and measurement time, and discuss some potential sources of systematic errors

  20. Characterization and simulation of noise in PET images reconstructed with OSEM: Development of a method for the generation of synthetic images.

    Science.gov (United States)

    Castro, P; Huerga, C; Chamorro, P; Garayoa, J; Roch, M; Pérez, L

    2018-04-17

    The goals of the study are to characterize imaging properties in 2D PET images reconstructed with the iterative algorithm ordered-subset expectation maximization (OSEM) and to propose a new method for the generation of synthetic images. The noise is analyzed in terms of its magnitude, spatial correlation, and spectral distribution through standard deviation, autocorrelation function, and noise power spectrum (NPS), respectively. Their variations with position and activity level are also analyzed. This noise analysis is based on phantom images acquired from 18 F uniform distributions. Experimental recovery coefficients of hot spheres in different backgrounds are employed to study the spatial resolution of the system through point spread function (PSF). The NPS and PSF functions provide the baseline for the proposed simulation method: convolution with PSF as kernel and noise addition from NPS. The noise spectral analysis shows that the main contribution is of random nature. It is also proven that attenuation correction does not alter noise texture but it modifies its magnitude. Finally, synthetic images of 2 phantoms, one of them an anatomical brain, are quantitatively compared with experimental images showing a good agreement in terms of pixel values and pixel correlations. Thus, the contrast to noise ratio for the biggest sphere in the NEMA IEC phantom is 10.7 for the synthetic image and 8.8 for the experimental image. The properties of the analyzed OSEM-PET images can be described by NPS and PSF functions. Synthetic images, even anatomical ones, are successfully generated by the proposed method based on the NPS and PSF. Copyright © 2018 Sociedad Española de Medicina Nuclear e Imagen Molecular. Publicado por Elsevier España, S.L.U. All rights reserved.

  1. Comparison of vibrational noise, between thermal power station (T.P.S.) Jamshoro and thermal power plant (T.P.P.) Pakistan Steel Bin Qasim Karachi

    International Nuclear Information System (INIS)

    Zaheer-ud-Din Memon

    2003-01-01

    Vibrational Noise is one of the major environmental problems in Industrial Plants. The Noise study has been under taken in (Japanese Unit) Thermal Power Station (TPS) Jamshoro, which generates 250 MW since Jan: 1990 and Russian Unit Thermal Power Plant (TPP) Pak Steel Bin Qasim Karachi, generates 165 MW since 1984. The prevailing Noise has been recorded in detail; at Basement area feed pumps, Turbines, Boilers F.D.F, I.D.F and Compressor houses. Comparing these two Plants, the Noise Level found more Intensive i.e. 97- 114 dB(A) at TPP Pak Steel Bin Qasim as against 91.4 -96.3 dB(A) at TPS Jamshoro, which was even higher one in the light of ISO and other National Standards. In the light of permissible Occupational Noise exposure limits, as allowed by the ISO and other National Standards, some recommendations have been made to provide safety measures for workers against high level noise health hazards like head ache, hearing problem, irritation, accidents at work, tension, disturbance to work and so many psychological effects, along with guidelines to improve the efficiency of the plants. (author)

  2. Realistic simulation of reduced-dose CT with noise modeling and sinogram synthesis using DICOM CT images

    International Nuclear Information System (INIS)

    Won Kim, Chang; Kim, Jong Hyo

    2014-01-01

    Purpose: Reducing the patient dose while maintaining the diagnostic image quality during CT exams is the subject of a growing number of studies, in which simulations of reduced-dose CT with patient data have been used as an effective technique when exploring the potential of various dose reduction techniques. Difficulties in accessing raw sinogram data, however, have restricted the use of this technique to a limited number of institutions. Here, we present a novel reduced-dose CT simulation technique which provides realistic low-dose images without the requirement of raw sinogram data. Methods: Two key characteristics of CT systems, the noise equivalent quanta (NEQ) and the algorithmic modulation transfer function (MTF), were measured for various combinations of object attenuation and tube currents by analyzing the noise power spectrum (NPS) of CT images obtained with a set of phantoms. Those measurements were used to develop a comprehensive CT noise model covering the reduced x-ray photon flux, object attenuation, system noise, and bow-tie filter, which was then employed to generate a simulated noise sinogram for the reduced-dose condition with the use of a synthetic sinogram generated from a reference CT image. The simulated noise sinogram was filtered with the algorithmic MTF and back-projected to create a noise CT image, which was then added to the reference CT image, finally providing a simulated reduced-dose CT image. The simulation performance was evaluated in terms of the degree of NPS similarity, the noise magnitude, the bow-tie filter effect, and the streak noise pattern at photon starvation sites with the set of phantom images. Results: The simulation results showed good agreement with actual low-dose CT images in terms of their visual appearance and in a quantitative evaluation test. The magnitude and shape of the NPS curves of the simulated low-dose images agreed well with those of real low-dose images, showing discrepancies of less than +/−3.2% in

  3. Image de-noising based on mathematical morphology and multi-objective particle swarm optimization

    Science.gov (United States)

    Dou, Liyun; Xu, Dan; Chen, Hao; Liu, Yicheng

    2017-07-01

    To overcome the problem of image de-noising, an efficient image de-noising approach based on mathematical morphology and multi-objective particle swarm optimization (MOPSO) is proposed in this paper. Firstly, constructing a series and parallel compound morphology filter based on open-close (OC) operation and selecting a structural element with different sizes try best to eliminate all noise in a series link. Then, combining multi-objective particle swarm optimization (MOPSO) to solve the parameters setting of multiple structural element. Simulation result shows that our algorithm can achieve a superior performance compared with some traditional de-noising algorithm.

  4. Evaluation of mixed-signal noise effects in photon-counting X-ray image sensor readout circuits

    International Nuclear Information System (INIS)

    Lundgren, Jan; Abdalla, Suliman; O'Nils, Mattias; Oelmann, Bengt

    2006-01-01

    In readout electronics for photon-counting pixel detectors, the tight integration between analog and digital blocks causes the readout electronics to be sensitive to on-chip noise coupling. This noise coupling can result in faulty luminance values in grayscale X-ray images, or as color distortions in a color X-ray imaging system. An exploration of simulating noise coupling in readout circuits is presented which enables the discovery of sensitive blocks at as early a stage as possible, in order to avoid costly design iterations. The photon-counting readout system has been simulated for noise coupling in order to highlight the existing problems of noise coupling in X-ray imaging systems. The simulation results suggest that on-chip noise coupling should be considered and simulated in future readout electronics systems for X-ray detectors

  5. Analysis and Extension of the Percentile Method, Estimating a Noise Curve from a Single Image

    Directory of Open Access Journals (Sweden)

    Miguel Colom

    2013-12-01

    Full Text Available Given a white Gaussian noise signal on a sampling grid, its variance can be estimated from a small block sample. However, in natural images we observe the combination of the geometry of the scene being photographed and the added noise. In this case, estimating directly the standard deviation of the noise from block samples is not reliable since the measured standard deviation is not explained just by the noise but also by the geometry of the image. The Percentile method tries to estimate the standard deviation of the noise from blocks of a high-passed version of the image and a small p-percentile of these standard deviations. The idea behind is that edges and textures in a block of the image increase the observed standard deviation but they never make it decrease. Therefore, a small percentile (0.5%, for example in the list of standard deviations of the blocks is less likely to be affected by the edges and textures than a higher percentile (50%, for example. The 0.5%-percentile is empirically proven to be adequate for most natural, medical and microscopy images. The Percentile method is adapted to signal-dependent noise, which is realistic with the Poisson noise model obtained by a CCD device in a digital camera.

  6. The Noise Clinic: a Blind Image Denoising Algorithm

    Directory of Open Access Journals (Sweden)

    Marc Lebrun

    2015-01-01

    Full Text Available This paper describes the complete implementation of a blind image algorithm, that takes any digital image as input. In a first step the algorithm estimates a Signal and Frequency Dependent (SFD noise model. In a second step, the image is denoised by a multiscale adaptation of the Non-local Bayes denoising method. We focus here on a careful analysis of the denoising step and present a detailed discussion of the influence of its parameters. Extensive commented tests of the blind denoising algorithm are presented, on real JPEG images and scans of old photographs.

  7. Acoustic noise in functional magnetic resonance imaging reduces pain unpleasantness ratings.

    Science.gov (United States)

    Boyle, Y; Bentley, D E; Watson, A; Jones, A K P

    2006-07-01

    Functional magnetic resonance imaging (fMRI) is increasingly used in cognitive studies. Unfortunately, the scanner produces acoustic noise during the image acquisition process. Interference from acoustic noise is known to affect auditory, visual and motor processing, raising the possibility that acoustic interference may also modulate processing of other sensory modalities such as pain. With the increasing use of fMRI in the investigation of the mechanisms of pain perception, particularly in relation to attention, this issue has become highly relevant. Pain is a complex experience, composed of sensory-discriminative, affective-motivational and cognitive-evaluative components. The aim of this experiment was to assess the effect of MRI scanner noise, compared to white noise, on the affective (unpleasantness) and the sensory-discriminative (localisation) components of pain. Painful radiant heat from a CO(2) laser was delivered to the skin of the right forearm in 24 healthy volunteers. The volunteers attended to either pain location or pain unpleasantness during three conditions: i) no noise, ii) exposure to MRI scanner noise (85 dB) or iii) exposure to white noise (85 dB). Both MRI scanner noise and white noise significantly reduced unpleasantness ratings (from 5.1 +/- 1.6 in the control condition to 4.7 +/- 1.5 (P = 0.002) and 4.6 +/- 1.6 (P white noise respectively), whereas the ability to localise pain was not significantly affected (from 85.4 +/- 9.2% correct in the control condition to 83.1 +/- 10.3% (P = 0.06) and 83.9 +/- 9.5% (P = 0.27) with MRI scanner and white noise respectively). This phenomenon should be taken into account in the design of fMRI studies into human pain perception.

  8. Ghost imaging with third-order correlated thermal light

    International Nuclear Information System (INIS)

    Ou, L-H; Kuang, L-M

    2007-01-01

    In this paper, we propose a ghost imaging scheme with third-order correlated thermal light. We show that it is possible to produce the spatial information of an object at two different places in a nonlocal fashion by means of a third-order correlated imaging process with a third-order correlated thermal source and third-order correlation measurement. Concretely, we propose a protocol to create two ghost images at two different places from one object. This protocol involves two optical configurations. We derive the Gaussian thin lens equations and plot the geometrical optics of the ghost imaging processes for the two configurations. It is indicated that third-order correlated ghost imaging with thermal light exhibits richer correlated imaging effects than second-order correlated ghost imaging with thermal light

  9. Adaptive iterated function systems filter for images highly corrupted with fixed - Value impulse noise

    Science.gov (United States)

    Shanmugavadivu, P.; Eliahim Jeevaraj, P. S.

    2014-06-01

    The Adaptive Iterated Functions Systems (AIFS) Filter presented in this paper has an outstanding potential to attenuate the fixed-value impulse noise in images. This filter has two distinct phases namely noise detection and noise correction which uses Measure of Statistics and Iterated Function Systems (IFS) respectively. The performance of AIFS filter is assessed by three metrics namely, Peak Signal-to-Noise Ratio (PSNR), Mean Structural Similarity Index Matrix (MSSIM) and Human Visual Perception (HVP). The quantitative measures PSNR and MSSIM endorse the merit of this filter in terms of degree of noise suppression and details/edge preservation respectively, in comparison with the high performing filters reported in the recent literature. The qualitative measure HVP confirms the noise suppression ability of the devised filter. This computationally simple noise filter broadly finds application wherein the images are highly degraded by fixed-value impulse noise.

  10. An image-processing method to detect sub-optical features based on understanding noise in intensity measurements.

    Science.gov (United States)

    Bhatia, Tripta

    2018-02-01

    Accurate quantitative analysis of image data requires that we distinguish between fluorescence intensity (true signal) and the noise inherent to its measurements to the extent possible. We image multilamellar membrane tubes and beads that grow from defects in the fluid lamellar phase of the lipid 1,2-dioleoyl-sn-glycero-3-phosphocholine dissolved in water and water-glycerol mixtures by using fluorescence confocal polarizing microscope. We quantify image noise and determine the noise statistics. Understanding the nature of image noise also helps in optimizing image processing to detect sub-optical features, which would otherwise remain hidden. We use an image-processing technique "optimum smoothening" to improve the signal-to-noise ratio of features of interest without smearing their structural details. A high SNR renders desired positional accuracy with which it is possible to resolve features of interest with width below optical resolution. Using optimum smoothening, the smallest and the largest core diameter detected is of width [Formula: see text] and [Formula: see text] nm, respectively, discussed in this paper. The image-processing and analysis techniques and the noise modeling discussed in this paper can be used for detailed morphological analysis of features down to sub-optical length scales that are obtained by any kind of fluorescence intensity imaging in the raster mode.

  11. Thermal infrared panoramic imaging sensor

    Science.gov (United States)

    Gutin, Mikhail; Tsui, Eddy K.; Gutin, Olga; Wang, Xu-Ming; Gutin, Alexey

    2006-05-01

    Panoramic cameras offer true real-time, 360-degree coverage of the surrounding area, valuable for a variety of defense and security applications, including force protection, asset protection, asset control, security including port security, perimeter security, video surveillance, border control, airport security, coastguard operations, search and rescue, intrusion detection, and many others. Automatic detection, location, and tracking of targets outside protected area ensures maximum protection and at the same time reduces the workload on personnel, increases reliability and confidence of target detection, and enables both man-in-the-loop and fully automated system operation. Thermal imaging provides the benefits of all-weather, 24-hour day/night operation with no downtime. In addition, thermal signatures of different target types facilitate better classification, beyond the limits set by camera's spatial resolution. The useful range of catadioptric panoramic cameras is affected by their limited resolution. In many existing systems the resolution is optics-limited. Reflectors customarily used in catadioptric imagers introduce aberrations that may become significant at large camera apertures, such as required in low-light and thermal imaging. Advantages of panoramic imagers with high image resolution include increased area coverage with fewer cameras, instantaneous full horizon detection, location and tracking of multiple targets simultaneously, extended range, and others. The Automatic Panoramic Thermal Integrated Sensor (APTIS), being jointly developed by Applied Science Innovative, Inc. (ASI) and the Armament Research, Development and Engineering Center (ARDEC) combines the strengths of improved, high-resolution panoramic optics with thermal imaging in the 8 - 14 micron spectral range, leveraged by intelligent video processing for automated detection, location, and tracking of moving targets. The work in progress supports the Future Combat Systems (FCS) and the

  12. Wideband Low Noise Amplifiers Exploiting Thermal Noise Cancellation

    NARCIS (Netherlands)

    Bruccoleri, F.; Klumperink, Eric A.M.; Nauta, Bram

    2005-01-01

    Low Noise Amplifiers (LNAs) are commonly used to amplify signals that are too weak for direct processing for example in radio or cable receivers. Traditionally, low noise amplifiers are implemented via tuned amplifiers, exploiting inductors and capacitors in resonating LC-circuits. This can render

  13. New Hybrid Variational Recovery Model for Blurred Images with Multiplicative Noise

    DEFF Research Database (Denmark)

    Dong, Yiqiu; Zeng, Tieyong

    2013-01-01

    A new hybrid variational model for recovering blurred images in the presence of multiplicative noise is proposed. Inspired by previous work on multiplicative noise removal, an I-divergence technique is used to build a strictly convex model under a condition that ensures the uniqueness...

  14. A Convex Variational Model for Restoring Blurred Images with Multiplicative Noise

    DEFF Research Database (Denmark)

    Dong, Yiqiu; Tieyong Zeng

    2013-01-01

    In this paper, a new variational model for restoring blurred images with multiplicative noise is proposed. Based on the statistical property of the noise, a quadratic penalty function technique is utilized in order to obtain a strictly convex model under a mild condition, which guarantees...

  15. Investigation of ferroelectric materials by the thermal noise method: advantages and limitations

    Czech Academy of Sciences Publication Activity Database

    Bednyakov, Petr; Shnaidshtein, I. V.; Strukov, B. A.

    2016-01-01

    Roč. 500, č. 1 (2016), 203-217 ISSN 0015-0193 R&D Projects: GA ČR GA13-15110S Institutional support: RVO:68378271 Keywords : thermal noise * ferroelectricity * thin films * dielectric permittivity * equivalent circuit Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.551, year: 2016

  16. l0TV: A Sparse Optimization Method for Impulse Noise Image Restoration

    KAUST Repository

    Yuan, Ganzhao; Ghanem, Bernard

    2017-01-01

    Total Variation (TV) is an effective and popular prior model in the field of regularization-based image processing. This paper focuses on total variation for removing impulse noise in image restoration. This type of noise frequently arises in data acquisition and transmission due to many reasons, e.g. a faulty sensor or analog-to-digital converter errors. Removing this noise is an important task in image restoration. State-of-the-art methods such as Adaptive Outlier Pursuit(AOP), which is based on TV with l02-norm data fidelity, only give sub-optimal performance. In this paper, we propose a new sparse optimization method, called l0TV-PADMM, which solves the TV-based restoration problem with l0-norm data fidelity. To effectively deal with the resulting non-convex non-smooth optimization problem, we first reformulate it as an equivalent biconvex Mathematical Program with Equilibrium Constraints (MPEC), and then solve it using a proximal Alternating Direction Method of Multipliers (PADMM). Our l0TV-PADMM method finds a desirable solution to the original l0-norm optimization problem and is proven to be convergent under mild conditions. We apply l0TV-PADMM to the problems of image denoising and deblurring in the presence of impulse noise. Our extensive experiments demonstrate that l0TV-PADMM outperforms state-of-the-art image restoration methods.

  17. l0TV: A Sparse Optimization Method for Impulse Noise Image Restoration

    KAUST Repository

    Yuan, Ganzhao

    2017-12-18

    Total Variation (TV) is an effective and popular prior model in the field of regularization-based image processing. This paper focuses on total variation for removing impulse noise in image restoration. This type of noise frequently arises in data acquisition and transmission due to many reasons, e.g. a faulty sensor or analog-to-digital converter errors. Removing this noise is an important task in image restoration. State-of-the-art methods such as Adaptive Outlier Pursuit(AOP), which is based on TV with l02-norm data fidelity, only give sub-optimal performance. In this paper, we propose a new sparse optimization method, called l0TV-PADMM, which solves the TV-based restoration problem with l0-norm data fidelity. To effectively deal with the resulting non-convex non-smooth optimization problem, we first reformulate it as an equivalent biconvex Mathematical Program with Equilibrium Constraints (MPEC), and then solve it using a proximal Alternating Direction Method of Multipliers (PADMM). Our l0TV-PADMM method finds a desirable solution to the original l0-norm optimization problem and is proven to be convergent under mild conditions. We apply l0TV-PADMM to the problems of image denoising and deblurring in the presence of impulse noise. Our extensive experiments demonstrate that l0TV-PADMM outperforms state-of-the-art image restoration methods.

  18. Poisson-Gaussian Noise Reduction Using the Hidden Markov Model in Contourlet Domain for Fluorescence Microscopy Images

    Science.gov (United States)

    Yang, Sejung; Lee, Byung-Uk

    2015-01-01

    In certain image acquisitions processes, like in fluorescence microscopy or astronomy, only a limited number of photons can be collected due to various physical constraints. The resulting images suffer from signal dependent noise, which can be modeled as a Poisson distribution, and a low signal-to-noise ratio. However, the majority of research on noise reduction algorithms focuses on signal independent Gaussian noise. In this paper, we model noise as a combination of Poisson and Gaussian probability distributions to construct a more accurate model and adopt the contourlet transform which provides a sparse representation of the directional components in images. We also apply hidden Markov models with a framework that neatly describes the spatial and interscale dependencies which are the properties of transformation coefficients of natural images. In this paper, an effective denoising algorithm for Poisson-Gaussian noise is proposed using the contourlet transform, hidden Markov models and noise estimation in the transform domain. We supplement the algorithm by cycle spinning and Wiener filtering for further improvements. We finally show experimental results with simulations and fluorescence microscopy images which demonstrate the improved performance of the proposed approach. PMID:26352138

  19. Understanding synthesis imaging dynamic range

    Science.gov (United States)

    Braun, R.

    2013-03-01

    We develop a general framework for quantifying the many different contributions to the noise budget of an image made with an array of dishes or aperture array stations. Each noise contribution to the visibility data is associated with a relevant correlation timescale and frequency bandwidth so that the net impact on a complete observation can be assessed when a particular effect is not captured in the instrumental calibration. All quantities are parameterised as function of observing frequency and the visibility baseline length. We apply the resulting noise budget analysis to a wide range of existing and planned telescope systems that will operate between about 100 MHz and 5 GHz to ascertain the magnitude of the calibration challenges that they must overcome to achieve thermal noise limited performance. We conclude that calibration challenges are increased in several respects by small dimensions of the dishes or aperture array stations. It will be more challenging to achieve thermal noise limited performance using 15 m class dishes rather than the 25 m dishes of current arrays. Some of the performance risks are mitigated by the deployment of phased array feeds and more with the choice of an (alt,az,pol) mount, although a larger dish diameter offers the best prospects for risk mitigation. Many improvements to imaging performance can be anticipated at the expense of greater complexity in calibration algorithms. However, a fundamental limitation is ultimately imposed by an insufficient number of data constraints relative to calibration variables. The upcoming aperture array systems will be operating in a regime that has never previously been addressed, where a wide range of effects are expected to exceed the thermal noise by two to three orders of magnitude. Achieving routine thermal noise limited imaging performance with these systems presents an extreme challenge. The magnitude of that challenge is inversely related to the aperture array station diameter.

  20. Noninvasive, low-noise, fast imaging of blood volume and deoxygenation changes in muscles using light-emitting diode continuous-wave imager

    Science.gov (United States)

    Lin, Yuanqing; Lech, Gwen; Nioka, Shoko; Intes, Xavier; Chance, Britton

    2002-08-01

    This article focuses on optimizing the signal to noise ratio (SNR) of a three-wavelength light-emitting diode (LED) near-infrared continuous-wave (cw) imager and its application to in vivo muscle metabolism measurement. The shot-noise limited SNR is derived and calculated to be 2 x104 for the physiological blood concentrations of muscle. Aiming at shot-noise limited SNR performance and fast imaging, we utilize sample and hold circuits to reduce high-frequency noise. These circuits have also been designed to be parallel integrating, through which SNR of 2 x103 and 2 Hz imaging acquisition rate have been achieved when the probe is placed on a muscle model. The noise corresponds to 2 x10-4 optical density error, which suggests an in vitro resolution of 15. 4 nM blood volume and 46.8 nM deoxygenation changes. A 48 dB digital gain control circuit with 256 steps is employed to enlarge the dynamic range of the imager. We utilize cuff ischemia as a living model demonstration and its results are reported. The instrument is applied during exercise to measure the changes of blood volume and deoxygenation, which provides important information about muscle metabolism. We find that the primary source of noise encountered during exercise experiment is from the random motion of muscle. The results demonstrate that the LED cw imager is ideal for the noninvasive study of muscle metabolism.

  1. Automated measurement of CT noise in patient images with a novel structure coherence feature

    International Nuclear Information System (INIS)

    Chun, Minsoo; Kim, Jong Hyo; Choi, Young Hun

    2015-01-01

    While the assessment of CT noise constitutes an important task for the optimization of scan protocols in clinical routine, the majority of noise measurements in practice still rely on manual operation, hence limiting their efficiency and reliability. This study presents an algorithm for the automated measurement of CT noise in patient images with a novel structure coherence feature. The proposed algorithm consists of a four-step procedure including subcutaneous fat tissue selection, the calculation of structure coherence feature, the determination of homogeneous ROIs, and the estimation of the average noise level. In an evaluation with 94 CT scans (16 517 images) of pediatric and adult patients along with the participation of two radiologists, ROIs were placed on a homogeneous fat region at 99.46% accuracy, and the agreement of the automated noise measurements with the radiologists’ reference noise measurements (PCC  =  0.86) was substantially higher than the within and between-rater agreements of noise measurements (PCC within   =  0.75, PCC between   =  0.70). In addition, the absolute noise level measurements matched closely the theoretical noise levels generated by a reduced-dose simulation technique. Our proposed algorithm has the potential to be used for examining the appropriateness of radiation dose and the image quality of CT protocols for research purposes as well as clinical routine. (paper)

  2. More noise, please: How cultural overprinting in the urban environment can be exploited for improved subsurface imaging (Invited)

    Science.gov (United States)

    Weiss, C. J.

    2009-12-01

    A long standing issue for geophysical imaging methods revolves around the proper treatment of "noise": Defining what noise is; separating "noise" for "signal"; filtering and suppressing noise; and recently, challenging the prevailing view that noise is a nuisance to see if, instead, it may contribute favorably toward improving subsurface imaging fidelity. This last point is particularly relevant to geophysical imaging in the urban environment where noise sources are abundant, complex, and logistical constraints on geophysical field procedures prohibit a crude "turning up the volume" approach to simply drown out the noise with powerful sources of electromagnetic and seismic energy. In this contribution I explore the concept passive geophysical imaging which uses uncorrelated ambient noise as the source of geophysical imaging energy to be used in the urban environment. Examples will be presented from seismic and ground penetrating radar methods, in addition to new theoretical results bearing on the feasibility of low-frequency electromagnetic induction techniques.

  3. Improving Signal-to-Noise Ratio in Susceptibility Weighted Imaging: A Novel Multicomponent Non-Local Approach.

    Directory of Open Access Journals (Sweden)

    Pasquale Borrelli

    Full Text Available In susceptibility-weighted imaging (SWI, the high resolution required to obtain a proper contrast generation leads to a reduced signal-to-noise ratio (SNR. The application of a denoising filter to produce images with higher SNR and still preserve small structures from excessive blurring is therefore extremely desirable. However, as the distributions of magnitude and phase noise may introduce biases during image restoration, the application of a denoising filter is non-trivial. Taking advantage of the potential multispectral nature of MR images, a multicomponent approach using a Non-Local Means (MNLM denoising filter may perform better than a component-by-component image restoration method. Here we present a new MNLM-based method (Multicomponent-Imaginary-Real-SWI, hereafter MIR-SWI to produce SWI images with high SNR and improved conspicuity. Both qualitative and quantitative comparisons of MIR-SWI with the original SWI scheme and previously proposed SWI restoring pipelines showed that MIR-SWI fared consistently better than the other approaches. Noise removal with MIR-SWI also provided improvement in contrast-to-noise ratio (CNR and vessel conspicuity at higher factors of phase mask multiplications than the one suggested in the literature for SWI vessel imaging. We conclude that a proper handling of noise in the complex MR dataset may lead to improved image quality for SWI data.

  4. A new technique for noise reduction at coronary CT angiography with multi-phase data-averaging and non-rigid image registration

    Energy Technology Data Exchange (ETDEWEB)

    Tatsugami, Fuminari; Higaki, Toru; Nakamura, Yuko; Yamagami, Takuji; Date, Shuji; Awai, Kazuo [Hiroshima University, Department of Diagnostic Radiology, Minami-ku, Hiroshima (Japan); Fujioka, Chikako; Kiguchi, Masao [Hiroshima University, Department of Radiology, Minami-ku, Hiroshima (Japan); Kihara, Yasuki [Hiroshima University, Department of Cardiovascular Medicine, Minami-ku, Hiroshima (Japan)

    2015-01-15

    To investigate the feasibility of a newly developed noise reduction technique at coronary CT angiography (CTA) that uses multi-phase data-averaging and non-rigid image registration. Sixty-five patients underwent coronary CTA with prospective ECG-triggering. The range of the phase window was set at 70-80 % of the R-R interval. First, three sets of consecutive volume data at 70 %, 75 % and 80 % of the R-R interval were prepared. Second, we applied non-rigid registration to align the 70 % and 80 % images to the 75 % image. Finally, we performed weighted averaging of the three images and generated a de-noised image. The image noise and contrast-to-noise ratio (CNR) in the proximal coronary arteries between the conventional 75 % and the de-noised images were compared. Two radiologists evaluated the image quality using a 5-point scale (1, poor; 5, excellent). On de-noised images, mean image noise was significantly lower than on conventional 75 % images (18.3 HU ± 2.6 vs. 23.0 HU ± 3.3, P < 0.01) and the CNR was significantly higher (P < 0.01). The mean image quality score for conventional 75 % and de-noised images was 3.9 and 4.4, respectively (P < 0.01). Our method reduces image noise and improves image quality at coronary CTA. (orig.)

  5. High-order noise analysis for low dose iterative image reconstruction methods: ASIR, IRIS, and MBAI

    Science.gov (United States)

    Do, Synho; Singh, Sarabjeet; Kalra, Mannudeep K.; Karl, W. Clem; Brady, Thomas J.; Pien, Homer

    2011-03-01

    Iterative reconstruction techniques (IRTs) has been shown to suppress noise significantly in low dose CT imaging. However, medical doctors hesitate to accept this new technology because visual impression of IRT images are different from full-dose filtered back-projection (FBP) images. Most common noise measurements such as the mean and standard deviation of homogeneous region in the image that do not provide sufficient characterization of noise statistics when probability density function becomes non-Gaussian. In this study, we measure L-moments of intensity values of images acquired at 10% of normal dose and reconstructed by IRT methods of two state-of-art clinical scanners (i.e., GE HDCT and Siemens DSCT flash) by keeping dosage level identical to each other. The high- and low-dose scans (i.e., 10% of high dose) were acquired from each scanner and L-moments of noise patches were calculated for the comparison.

  6. Improvement in perception of image sharpness through the addition of noise and its relationship with memory texture

    Science.gov (United States)

    Wan, Xiazi; Kobayashi, Hiroyuki; Aoki, Naokazu

    2015-03-01

    In a preceding study, we investigated the effects of image noise on the perception of image sharpness using white noise, and one- and two-dimensional single-frequency sinusoidal patterns as stimuli. This study extends our preceding study by evaluating natural color images, rather than black-and-white patterns. The results showed that the effect of noise in improving image sharpness perception is more evident in blurred images than in sharp images. This is consistent with the results of the preceding study. In another preceding study, we proposed "memory texture" to explain the preferred granularity of images, as a concept similar to "memory color" for preferred color reproduction. We observed individual differences in type of memory texture for each object, that is, white or 1/f noise. This study discusses the relationship between improvement of sharpness perception by adding noise, and the memory texture, following its individual differences. We found that memory texture is one of the elements that affect sharpness perception.

  7. Next generation thermal imaging

    International Nuclear Information System (INIS)

    Marche, P.P.

    1988-01-01

    The best design of high performance thermal imagers for the 1990s will use horizontal quasi-linear arrays with focal plane processing associated with a simple vertical mechanical scanner. These imagers will have performance that is greatly improved compared to that of present-day devices (50 to 100 percent range and resolution improvement). 5 references

  8. Ultrasound elastographic imaging of thermal lesions and temperature profiles during radiofrequency ablation

    Science.gov (United States)

    Techavipoo, Udomchai

    Manual palpation to sense variations in tissue stiffness for disease diagnosis has been regularly performed by clinicians for centuries. However, it is generally limited to large and superficial structures and the ability of the physician performing the palpation. Imaging of tissue stiffness or elastic properties via the aid of modern imaging such as ultrasound and magnetic resonance imaging, referred to as elastography, enhances the capability for disease diagnosis. In addition, elastography could be used for monitoring tissue response to minimally invasive ablative therapies, which are performed percutaneously to destruct tumors with minimum damage to surrounding tissue. Monitoring tissue temperature during ablation is another approach to estimate tissue damage. The ultimate goal of this dissertation is to improve the image quality of elastograms and temperature profiles for visualizing thermal lesions during and after ablative therapies. Elastographic imaging of thermal lesions is evaluated by comparison of sizes, shapes, and volumes with the results obtained using gross pathology. Semiautomated segmentation of lesion boundaries on elastograms is also developed. It provides comparable results to those with manual segmentation. Elastograms imaged during radiofrequency ablation in vitro show that the impact of gas bubbles during ablation on the ability to delineate the thermal lesion is small. Two novel methods to reduce noise artifacts in elastograms, and an accurate estimation of displacement vectors are proposed. The first method applies wavelet-denoising algorithms to the displacement estimates. The second method utilizes angular compounding of the elastograms generated using ultrasound signal frames acquired from different insonification angles. These angular frames are also utilized to estimate all tissue displacement vector components in response to a deformation. These enable the generation of normal and shear strain elastograms and Poisson's ratio

  9. Wide-band CMOS low-noise amplifier exploiting thermal noise canceling

    OpenAIRE

    Bruccoleri, F.; Klumperink, Eric A.M.; Nauta, Bram

    2004-01-01

    Known elementary wide-band amplifiers suffer from a fundamental tradeoff between noise figure (NF) and source impedance matching, which limits the NF to values typically above 3 dB. Global negative feedback can be used to break this tradeoff, however, at the price of potential instability. In contrast, this paper presents a feedforward noise-canceling technique, which allows for simultaneous noise and impedance matching, while canceling the noise and distortion contributions of the matching d...

  10. Noise and analyzer-crystal angular position analysis for analyzer-based phase-contrast imaging

    Science.gov (United States)

    Majidi, Keivan; Li, Jun; Muehleman, Carol; Brankov, Jovan G.

    2014-04-01

    The analyzer-based phase-contrast x-ray imaging (ABI) method is emerging as a potential alternative to conventional radiography. Like many of the modern imaging techniques, ABI is a computed imaging method (meaning that images are calculated from raw data). ABI can simultaneously generate a number of planar parametric images containing information about absorption, refraction, and scattering properties of an object. These images are estimated from raw data acquired by measuring (sampling) the angular intensity profile of the x-ray beam passed through the object at different angular positions of the analyzer crystal. The noise in the estimated ABI parametric images depends upon imaging conditions like the source intensity (flux), measurements angular positions, object properties, and the estimation method. In this paper, we use the Cramér-Rao lower bound (CRLB) to quantify the noise properties in parametric images and to investigate the effect of source intensity, different analyzer-crystal angular positions and object properties on this bound, assuming a fixed radiation dose delivered to an object. The CRLB is the minimum bound for the variance of an unbiased estimator and defines the best noise performance that one can obtain regardless of which estimation method is used to estimate ABI parametric images. The main result of this paper is that the variance (hence the noise) in parametric images is directly proportional to the source intensity and only a limited number of analyzer-crystal angular measurements (eleven for uniform and three for optimal non-uniform) are required to get the best parametric images. The following angular measurements only spread the total dose to the measurements without improving or worsening CRLB, but the added measurements may improve parametric images by reducing estimation bias. Next, using CRLB we evaluate the multiple-image radiography, diffraction enhanced imaging and scatter diffraction enhanced imaging estimation techniques

  11. Noise and analyzer-crystal angular position analysis for analyzer-based phase-contrast imaging

    International Nuclear Information System (INIS)

    Majidi, Keivan; Brankov, Jovan G; Li, Jun; Muehleman, Carol

    2014-01-01

    The analyzer-based phase-contrast x-ray imaging (ABI) method is emerging as a potential alternative to conventional radiography. Like many of the modern imaging techniques, ABI is a computed imaging method (meaning that images are calculated from raw data). ABI can simultaneously generate a number of planar parametric images containing information about absorption, refraction, and scattering properties of an object. These images are estimated from raw data acquired by measuring (sampling) the angular intensity profile of the x-ray beam passed through the object at different angular positions of the analyzer crystal. The noise in the estimated ABI parametric images depends upon imaging conditions like the source intensity (flux), measurements angular positions, object properties, and the estimation method. In this paper, we use the Cramér–Rao lower bound (CRLB) to quantify the noise properties in parametric images and to investigate the effect of source intensity, different analyzer-crystal angular positions and object properties on this bound, assuming a fixed radiation dose delivered to an object. The CRLB is the minimum bound for the variance of an unbiased estimator and defines the best noise performance that one can obtain regardless of which estimation method is used to estimate ABI parametric images. The main result of this paper is that the variance (hence the noise) in parametric images is directly proportional to the source intensity and only a limited number of analyzer-crystal angular measurements (eleven for uniform and three for optimal non-uniform) are required to get the best parametric images. The following angular measurements only spread the total dose to the measurements without improving or worsening CRLB, but the added measurements may improve parametric images by reducing estimation bias. Next, using CRLB we evaluate the multiple-image radiography, diffraction enhanced imaging and scatter diffraction enhanced imaging estimation techniques

  12. RESEARCH OF REGISTRATION APPROACHES OF THERMAL INFRARED IMAGES AND INTENSITY IMAGES OF POINT CLOUD

    Directory of Open Access Journals (Sweden)

    L. Liu

    2017-09-01

    Full Text Available In order to realize the analysis of thermal energy of the objects in 3D vision, the registration approach of thermal infrared images and TLS (Terrestrial Laser Scanner point cloud was studied. The original data was pre-processed. For the sake of making the scale and brightness contrast of the two kinds of data meet the needs of basic matching, the intensity image of point cloud was produced and projected to spherical coordinate system, histogram equalization processing was done for thermal infrared image.This paper focused on the research of registration approaches of thermal infrared images and intensity images of point cloud based on SIFT,EOH-SIFT and PIIFD operators. The latter of which is usually used for medical image matching with different spectral character. The comparison results of the experiments showed that PIIFD operator got much more accurate feature point correspondences compared to SIFT and EOH-SIFT operators. The thermal infrared image and intensity image also have ideal overlap results by quadratic polynomial transformation. Therefore, PIIFD can be used as the basic operator for the registration of thermal infrared images and intensity images, and the operator can also be further improved by incorporating the iteration method.

  13. A novel technique to monitor thermal discharges using thermal infrared imaging.

    Science.gov (United States)

    Muthulakshmi, A L; Natesan, Usha; Ferrer, Vincent A; Deepthi, K; Venugopalan, V P; Narasimhan, S V

    2013-09-01

    Coastal temperature is an important indicator of water quality, particularly in regions where delicate ecosystems sensitive to water temperature are present. Remote sensing methods are highly reliable for assessing the thermal dispersion. The plume dispersion from the thermal outfall of the nuclear power plant at Kalpakkam, on the southeast coast of India, was investigated from March to December 2011 using thermal infrared images along with field measurements. The absolute temperature as provided by the thermal infrared (TIR) images is used in the Arc GIS environment for generating a spatial pattern of the plume movement. Good correlation of the temperature measured by the TIR camera with the field data (r(2) = 0.89) make it a reliable method for the thermal monitoring of the power plant effluents. The study portrays that the remote sensing technique provides an effective means of monitoring the thermal distribution pattern in coastal waters.

  14. A Thermal Imaging Instrument with Uncooled Detectors

    Science.gov (United States)

    Joseph, A. T.; Barrentine, E. M.; Brown, A. D.

    2017-12-01

    In this work, we perform an instrument concept study for sustainable thermal imaging over land with uncooled detectors. The National Research Council's Committee on Implementation of a Sustained Land Imaging Program has identified the inclusion of a thermal imager as critical for both current and future land imaging missions. Such an imaging instrument operating in two bands located at approximately 11 and 12 microns (for example, in Landsat 8, and also Landsat 9 when launched) will provide essential information for furthering our hydrologic understanding at scales of human influence, and produce field-scale moisture information through accurate retrievals of evapotranspiration (ET). Landsat 9 is slated to recycle the TIRS-2 instrument launched with Landsat 8 that uses cooled quantum well infrared photodetectors (QWIPs), hence requiring expensive and massive cryocooler technology to achieve its required spectral and spatial accuracies. Our goal is to conceptualize and develop a thermal imaging instrument which leverages recent and imminent technology advances in uncooled detectors. Such detector technology will offer the benefit of greatly reduced instrument cost, mass, and power at the expense of some acceptable loss in detector sensitivity. It would also allow a thermal imaging instrument to be fielded on board a low-cost platform, e.g., a CubeSat. Sustained and enhanced land imaging is crucial for providing high-quality science data on change in land use, forest health, crop status, environment, and climate. Accurate satellite mapping of ET at the agricultural field scale (the finest spatial scale of the environmental processes of interest) requires high-quality thermal data to produce the corresponding accurate land surface temperature (LST) retrievals used to drive an ET model. Such an imaging instrument would provide important information on the following: 1) the relationship between land-use and land/water management practices and water use dynamics; 2) the

  15. Image simulation and a model of noise power spectra across a range of mammographic beam qualities

    Energy Technology Data Exchange (ETDEWEB)

    Mackenzie, Alistair, E-mail: alistairmackenzie@nhs.net; Dance, David R.; Young, Kenneth C. [National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Diaz, Oliver [Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom and Computer Vision and Robotics Research Institute, University of Girona, Girona 17071 (Spain)

    2014-12-15

    Purpose: The aim of this work is to create a model to predict the noise power spectra (NPS) for a range of mammographic radiographic factors. The noise model was necessary to degrade images acquired on one system to match the image quality of different systems for a range of beam qualities. Methods: Five detectors and x-ray systems [Hologic Selenia (ASEh), Carestream computed radiography CR900 (CRc), GE Essential (CSI), Carestream NIP (NIPc), and Siemens Inspiration (ASEs)] were characterized for this study. The signal transfer property was measured as the pixel value against absorbed energy per unit area (E) at a reference beam quality of 28 kV, Mo/Mo or 29 kV, W/Rh with 45 mm polymethyl methacrylate (PMMA) at the tube head. The contributions of the three noise sources (electronic, quantum, and structure) to the NPS were calculated by fitting a quadratic at each spatial frequency of the NPS against E. A quantum noise correction factor which was dependent on beam quality was quantified using a set of images acquired over a range of radiographic factors with different thicknesses of PMMA. The noise model was tested for images acquired at 26 kV, Mo/Mo with 20 mm PMMA and 34 kV, Mo/Rh with 70 mm PMMA for three detectors (ASEh, CRc, and CSI) over a range of exposures. The NPS were modeled with and without the noise correction factor and compared with the measured NPS. A previous method for adapting an image to appear as if acquired on a different system was modified to allow the reference beam quality to be different from the beam quality of the image. The method was validated by adapting the ASEh flat field images with two thicknesses of PMMA (20 and 70 mm) to appear with the imaging characteristics of the CSI and CRc systems. Results: The quantum noise correction factor rises with higher beam qualities, except for CR systems at high spatial frequencies, where a flat response was found against mean photon energy. This is due to the dominance of secondary quantum noise

  16. Noise reduction and image enhancement using a hardware implementation of artificial neural networks

    Science.gov (United States)

    David, Robert; Williams, Erin; de Tremiolles, Ghislain; Tannhof, Pascal

    1999-03-01

    In this paper, we present a neural based solution developed for noise reduction and image enhancement using the ZISC, an IBM hardware processor which implements the Restricted Coulomb Energy algorithm and the K-Nearest Neighbor algorithm. Artificial neural networks present the advantages of processing time reduction in comparison with classical models, adaptability, and the weighted property of pattern learning. The goal of the developed application is image enhancement in order to restore old movies (noise reduction, focus correction, etc.), to improve digital television images, or to treat images which require adaptive processing (medical images, spatial images, special effects, etc.). Image results show a quantitative improvement over the noisy image as well as the efficiency of this system. Further enhancements are being examined to improve the output of the system.

  17. A non-contact, thermal noise based method for the calibration of lateral deflection sensitivity in atomic force microscopy

    International Nuclear Information System (INIS)

    Mullin, Nic; Hobbs, Jamie K.

    2014-01-01

    Calibration of lateral forces and displacements has been a long standing problem in lateral force microscopies. Recently, it was shown by Wagner et al. that the thermal noise spectrum of the first torsional mode may be used to calibrate the deflection sensitivity of the detector. This method is quick, non-destructive and may be performed in situ in air or liquid. Here we make a full quantitative comparison of the lateral inverse optical lever sensitivity obtained by the lateral thermal noise method and the shape independent method developed by Anderson et al. We find that the thermal method provides accurate results for a wide variety of rectangular cantilevers, provided that the geometry of the cantilever is suitable for torsional stiffness calibration by the torsional Sader method, in-plane bending of the cantilever may be eliminated or accounted for and that any scaling of the lateral deflection signal between the measurement of the lateral thermal noise and the measurement of the lateral deflection is eliminated or corrected for. We also demonstrate that the thermal method may be used to characterize the linearity of the detector signal as a function of position, and find a deviation of less than 8% for the instrument used

  18. How to COAAD Images. II. A Coaddition Image that is Optimal for Any Purpose in the Background-dominated Noise Limit

    Energy Technology Data Exchange (ETDEWEB)

    Zackay, Barak; Ofek, Eran O. [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel)

    2017-02-20

    Image coaddition is one of the most basic operations that astronomers perform. In Paper I, we presented the optimal ways to coadd images in order to detect faint sources and to perform flux measurements under the assumption that the noise is approximately Gaussian. Here, we build on these results and derive from first principles a coaddition technique that is optimal for any hypothesis testing and measurement (e.g., source detection, flux or shape measurements, and star/galaxy separation), in the background-noise-dominated case. This method has several important properties. The pixels of the resulting coadded image are uncorrelated. This image preserves all the information (from the original individual images) on all spatial frequencies. Any hypothesis testing or measurement that can be done on all the individual images simultaneously, can be done on the coadded image without any loss of information. The PSF of this image is typically as narrow, or narrower than the PSF of the best image in the ensemble. Moreover, this image is practically indistinguishable from a regular single image, meaning that any code that measures any property on a regular astronomical image can be applied to it unchanged. In particular, the optimal source detection statistic derived in Paper I is reproduced by matched filtering this image with its own PSF. This coaddition process, which we call proper coaddition, can be understood as the maximum signal-to-noise ratio measurement of the Fourier transform of the image, weighted in such a way that the noise in the entire Fourier domain is of equal variance. This method has important implications for multi-epoch seeing-limited deep surveys, weak lensing galaxy shape measurements, and diffraction-limited imaging via speckle observations. The last topic will be covered in depth in future papers. We provide an implementation of this algorithm in MATLAB.

  19. Estimating envelope thermal characteristics from single point in time thermal images

    Science.gov (United States)

    Alshatshati, Salahaldin Faraj

    Energy efficiency programs implemented nationally in the U.S. by utilities have rendered savings which have cost on average 0.03/kWh. This cost is still well below generation costs. However, as the lowest cost energy efficiency measures are adopted, this the cost effectiveness of further investment declines. Thus there is a need to more effectively find the most opportunities for savings regionally and nationally, so that the greatest cost effectiveness in implementing energy efficiency can be achieved. Integral to this process. are at scale energy audits. However, on-site building energy audits process are expensive, in the range of US1.29/m2-$5.37/m2 and there are an insufficient number of professionals to perform the audits. Energy audits that can be conducted at-scale and at low cost are needed. Research is presented that addresses at community-wide scales characterization of building envelope thermal characteristics via drive-by and fly-over GPS linked thermal imaging. A central question drives this research: Can single point-in-time thermal images be used to infer U-values and thermal capacitances of walls and roofs? Previous efforts to use thermal images to estimate U-values have been limited to rare steady exterior weather conditions. The approaches posed here are based upon the development two models first is a dynamic model of a building envelope component with unknown U-value and thermal capacitance. The weather conditions prior to the thermal image are used as inputs to the model. The model is solved to determine the exterior surface temperature, ultimately predicted the temperature at the thermal measurement time. The model U-value and thermal capacitance are tuned in order to force the error between the predicted surface temperature and the measured surface temperature from thermal imaging to be near zero. This model is developed simply to show that such a model cannot be relied upon to accurately estimate the U-value. The second is a data

  20. Novel precision enhancement algorithm with reduced image noise in cosmic muon tomography applications

    Directory of Open Access Journals (Sweden)

    Lee Sangkyu

    2016-01-01

    Full Text Available In this paper, we present a new algorithm that improves muon-based generated tomography images with increased precision and reduced image noise applicable to the detection of nuclear materials. Cosmic muon tomography is an interrogation-based imaging technique that, over the last decade, has been frequently employed for the detection of high-Z materials. This technique exploits a magnitude of cosmic muon scattering angles in order to construct an image. The scattering angles of the muons striking the geometry of interest are non-uniform, as cosmic muons vary in energy. The randomness of the scattering angles leads to significant noise in the muon tomography image. GEANT4 is used to numerically create data on the momenta and positions of scattered muons in a predefined geometry that includes high-Z materials. The numerically generated information is then processed with the point of closest approach reconstruction method to construct a muon tomography image; statistical filters are then developed to refine the point of closest approach reconstructed images. The filtered images exhibit reduced noise and enhanced precision when attempting to identify the presence of high-Z materials. The average precision from the point of closest approach reconstruction method is 13 %; for the integrated method, 88 %. The filtered image, therefore, results in a seven-fold improvement in precision compared to the point of closest approach reconstructed image.

  1. Statistical model of intensity noise in con focal fluorescence microscopy images

    International Nuclear Information System (INIS)

    Montereali, R.M.; Almaviva, S.; Franzini, I.; Somma, F.

    2008-01-01

    The visible photoluminescence of aggregate F2 and F3+ color centers in Lithium Fluoride (LiF) thin layers, grown by thermal evaporation on various substrates (either crystalline or not) with different thicknesses, can be efficiently observed by using an optical con focal fluorescence microscope and a laser pump with emission wavelength tuned at about 450 nm. Starting from con focal fluorescence images of uniformly colored LiF samples, an automatic routine for the estimation of photoluminescence intensity noise has been developed at the Solid State Laser Laboratory and Spectroscopy of the ENEA Research Center in Frascati. We reported experimental results about application of that routine to the photoluminescence of LiF thin films, uniformly irradiated with an X-ray tube with energy spectrum centered on the Cu K? emission line (8,03 keV), at the CNR-IFN in Rome, that allow to identify a suitable statistical model for his description [it

  2. Secure Image Encryption Based On a Chua Chaotic Noise Generator

    Directory of Open Access Journals (Sweden)

    A. S. Andreatos

    2013-10-01

    Full Text Available This paper presents a secure image cryptography telecom system based on a Chua's circuit chaotic noise generator. A chaotic system based on synchronised Master–Slave Chua's circuits has been used as a chaotic true random number generator (CTRNG. Chaotic systems present unpredictable and complex behaviour. This characteristic, together with the dependence on the initial conditions as well as the tolerance of the circuit components, make CTRNGs ideal for cryptography. In the proposed system, the transmitter mixes an input image with chaotic noise produced by a CTRNG. Using thresholding techniques, the chaotic signal is converted to a true random bit sequence. The receiver must be able to reproduce exactly the same chaotic noise in order to subtract it from the received signal. This becomes possible with synchronisation between the two Chua's circuits: through the use of specific techniques, the trajectory of the Slave chaotic system can be bound to that of the Master circuit producing (almost identical behaviour. Additional blocks have been used in order to make the system highly parameterisable and robust against common attacks. The whole system is simulated in Matlab. Simulation results demonstrate satisfactory performance, as well as, robustness against cryptanalysis. The system works with both greyscale and colour jpg images.

  3. Effect of a television digital noise reduction device on fluoroscopic image quality and dose rate

    International Nuclear Information System (INIS)

    Jaffe, C.C.; Orphanoudakis, S.C.; Ablow, R.C.

    1982-01-01

    In conventional fluoroscopy, the current, and therefore the dose rate, is usually determined by the level at which the radiologist visualizes a just tolerable amount of photon ''mottle'' on the video monitor. In this study, digital processing of the analogue video image reduced noise and generated a television image at half the usual exposure rate. The technique uses frame delay to compare an incoming frame with the preceding output frame. A first-order recursive filter implemented under a motion-detection scheme operates on the image of a point-by-point basis. This effective motion detection algorithm permits noise suppression without creating noticeable lag in moving structures. Eight radiologists evaluated images of vesicoureteral reflux in the pig for noise, contrast, resolution, and general image quality on a five-point preferential scale. They rated the digitally processed fluoroscopy images equivalent in diagnostic value to unprocessed images

  4. Self-noise suppression schemes in blind image steganography

    Science.gov (United States)

    Ramkumar, Mahalingam; Akansu, Ali N.

    1999-11-01

    Blind or oblivious data hiding, can be considered as a signaling method where the origin of the signal constellation is not known. The origin however, can be estimated, by means of self-noise suppression techniques. In this paper, we propose such a technique, and present both theoretical and numerical evaluations of its performance in an additive noise scenario. The problem of optimal choice of the parameters of the proposed technique is also explored, and solutions are presented. Though the cover object is assumed to be an image for purposes of illustration, the proposed method is equally applicable for other types of multimedia data, like video, speech or music.

  5. Reduction of CMOS Image Sensor Read Noise to Enable Photon Counting.

    Science.gov (United States)

    Guidash, Michael; Ma, Jiaju; Vogelsang, Thomas; Endsley, Jay

    2016-04-09

    Recent activity in photon counting CMOS image sensors (CIS) has been directed to reduction of read noise. Many approaches and methods have been reported. This work is focused on providing sub 1 e(-) read noise by design and operation of the binary and small signal readout of photon counting CIS. Compensation of transfer gate feed-through was used to provide substantially reduced CDS time and source follower (SF) bandwidth. SF read noise was reduced by a factor of 3 with this method. This method can be applied broadly to CIS devices to reduce the read noise for small signals to enable use as a photon counting sensor.

  6. Noise in NC-AFM measurements with significant tip–sample interaction

    Directory of Open Access Journals (Sweden)

    Jannis Lübbe

    2016-12-01

    Full Text Available The frequency shift noise in non-contact atomic force microscopy (NC-AFM imaging and spectroscopy consists of thermal noise and detection system noise with an additional contribution from amplitude noise if there are significant tip–sample interactions. The total noise power spectral density DΔf(fm is, however, not just the sum of these noise contributions. Instead its magnitude and spectral characteristics are determined by the strongly non-linear tip–sample interaction, by the coupling between the amplitude and tip–sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL detector used for frequency demodulation. Here, we measure DΔf(fm for various NC-AFM parameter settings representing realistic measurement conditions and compare experimental data to simulations based on a model of the NC-AFM system that includes the tip–sample interaction. The good agreement between predicted and measured noise spectra confirms that the model covers the relevant noise contributions and interactions. Results yield a general understanding of noise generation and propagation in the NC-AFM and provide a quantitative prediction of noise for given experimental parameters. We derive strategies for noise-optimised imaging and spectroscopy and outline a full optimisation procedure for the instrumentation and control loops.

  7. Input Space Regularization Stabilizes Pre-images for Kernel PCA De-noising

    DEFF Research Database (Denmark)

    Abrahamsen, Trine Julie; Hansen, Lars Kai

    2009-01-01

    Solution of the pre-image problem is key to efficient nonlinear de-noising using kernel Principal Component Analysis. Pre-image estimation is inherently ill-posed for typical kernels used in applications and consequently the most widely used estimation schemes lack stability. For de...

  8. Noise simulation and rejection for the DELPHI Barrel Ring Imaging Cherenkov detector

    International Nuclear Information System (INIS)

    Bloch, D.

    1996-01-01

    The performance of Ring Imaging Cherenkov detectors is severely affected by the background noise due to the necessity of detecting single electrons. Furthermore, in the majority of the existing RICHs, the charged particles to be identified also cross the sensitive area of the apparatus thus creating secondary effects. The different noise sources and the background behaviour have been studied for the DELPHI RICH in order to efficiently clean the Cherenkov rings from the background while preserving the majority of the signal. Particular care has been taken to optimize the parameters of the Cherenkov image ''cleaning'' for the gas and the liquid radiators separately. For Z 0 hadronic decays 70% background rejection has been achieved, whilst 85% of the signal has been retained. This paper also presents a simulation of the noise producing mechanisms where ionization electrons, δ-rays, feedback electrons created during avalanches and electronic noise are modeled according to the measured parameters. Good agreement between data and simulation has been achieved. (orig.)

  9. Preliminary study on effects of 60Co γ-irradiation on video quality and the image de-noising methods

    International Nuclear Information System (INIS)

    Yuan Mei; Zhao Jianbin; Cui Lei

    2011-01-01

    There will be variable noises appear on images in video once the play device irradiated by γ-rays, so as to affect the image clarity. In order to eliminate the image noising, the affection mechanism of γ-irradiation on video-play device was studied in this paper and the methods to improve the image quality with both hardware and software were proposed by use of protection program and de-noising algorithm. The experimental results show that the scheme of video de-noising based on hardware and software can improve effectively the PSNR by 87.5 dB. (authors)

  10. Single frequency thermal wave radar: A next-generation dynamic thermography for quantitative non-destructive imaging over wide modulation frequency ranges.

    Science.gov (United States)

    Melnikov, Alexander; Chen, Liangjie; Ramirez Venegas, Diego; Sivagurunathan, Koneswaran; Sun, Qiming; Mandelis, Andreas; Rodriguez, Ignacio Rojas

    2018-04-01

    Single-Frequency Thermal Wave Radar Imaging (SF-TWRI) was introduced and used to obtain quantitative thickness images of coatings on an aluminum block and on polyetherketone, and to image blind subsurface holes in a steel block. In SF-TWR, the starting and ending frequencies of a linear frequency modulation sweep are chosen to coincide. Using the highest available camera frame rate, SF-TWRI leads to a higher number of sampled points along the modulation waveform than conventional lock-in thermography imaging because it is not limited by conventional undersampling at high frequencies due to camera frame-rate limitations. This property leads to large reduction in measurement time, better quality of images, and higher signal-noise-ratio across wide frequency ranges. For quantitative thin-coating imaging applications, a two-layer photothermal model with lumped parameters was used to reconstruct the layer thickness from multi-frequency SF-TWR images. SF-TWRI represents a next-generation thermography method with superior features for imaging important classes of thin layers, materials, and components that require high-frequency thermal-wave probing well above today's available infrared camera technology frame rates.

  11. Single frequency thermal wave radar: A next-generation dynamic thermography for quantitative non-destructive imaging over wide modulation frequency ranges

    Science.gov (United States)

    Melnikov, Alexander; Chen, Liangjie; Ramirez Venegas, Diego; Sivagurunathan, Koneswaran; Sun, Qiming; Mandelis, Andreas; Rodriguez, Ignacio Rojas

    2018-04-01

    Single-Frequency Thermal Wave Radar Imaging (SF-TWRI) was introduced and used to obtain quantitative thickness images of coatings on an aluminum block and on polyetherketone, and to image blind subsurface holes in a steel block. In SF-TWR, the starting and ending frequencies of a linear frequency modulation sweep are chosen to coincide. Using the highest available camera frame rate, SF-TWRI leads to a higher number of sampled points along the modulation waveform than conventional lock-in thermography imaging because it is not limited by conventional undersampling at high frequencies due to camera frame-rate limitations. This property leads to large reduction in measurement time, better quality of images, and higher signal-noise-ratio across wide frequency ranges. For quantitative thin-coating imaging applications, a two-layer photothermal model with lumped parameters was used to reconstruct the layer thickness from multi-frequency SF-TWR images. SF-TWRI represents a next-generation thermography method with superior features for imaging important classes of thin layers, materials, and components that require high-frequency thermal-wave probing well above today's available infrared camera technology frame rates.

  12. Automatic exposure control systems designed to maintain constant image noise: effects on computed tomography dose and noise relative to clinically accepted technique charts.

    Science.gov (United States)

    Favazza, Christopher P; Yu, Lifeng; Leng, Shuai; Kofler, James M; McCollough, Cynthia H

    2015-01-01

    To compare computed tomography dose and noise arising from use of an automatic exposure control (AEC) system designed to maintain constant image noise as patient size varies with clinically accepted technique charts and AEC systems designed to vary image noise. A model was developed to describe tube current modulation as a function of patient thickness. Relative dose and noise values were calculated as patient width varied for AEC settings designed to yield constant or variable noise levels and were compared to empirically derived values used by our clinical practice. Phantom experiments were performed in which tube current was measured as a function of thickness using a constant-noise-based AEC system and the results were compared with clinical technique charts. For 12-, 20-, 28-, 44-, and 50-cm patient widths, the requirement of constant noise across patient size yielded relative doses of 5%, 14%, 38%, 260%, and 549% and relative noises of 435%, 267%, 163%, 61%, and 42%, respectively, as compared with our clinically used technique chart settings at each respective width. Experimental measurements showed that a constant noise-based AEC system yielded 175% relative noise for a 30-cm phantom and 206% relative dose for a 40-cm phantom compared with our clinical technique chart. Automatic exposure control systems that prescribe constant noise as patient size varies can yield excessive noise in small patients and excessive dose in obese patients compared with clinically accepted technique charts. Use of noise-level technique charts and tube current limits can mitigate these effects.

  13. Dual-energy CT in patients with abdominal malignant lymphoma: impact of noise-optimised virtual monoenergetic imaging on objective and subjective image quality.

    Science.gov (United States)

    Lenga, L; Czwikla, R; Wichmann, J L; Leithner, D; Albrecht, M H; D'Angelo, T; Arendt, C T; Booz, C; Hammerstingl, R; Vogl, T J; Martin, S S

    2018-06-05

    To investigate the impact of noise-optimised virtual monoenergetic imaging (VMI+) reconstructions on quantitative and qualitative image parameters in patients with malignant lymphoma at dual-energy computed tomography (DECT) examinations of the abdomen. Thirty-five consecutive patients (mean age, 53.8±18.6 years; range, 21-82 years) with histologically proven malignant lymphoma of the abdomen were included retrospectively. Images were post-processed with standard linear blending (M_0.6), traditional VMI, and VMI+ technique at energy levels ranging from 40 to 100 keV in 10 keV increments. Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were objectively measured in lymphoma lesions. Image quality, lesion delineation, and image noise were rated subjectively by three blinded observers using five-point Likert scales. Quantitative image quality parameters peaked at 40-keV VMI+ (SNR, 15.77±7.74; CNR, 18.27±8.04) with significant differences compared to standard linearly blended M_0.6 (SNR, 7.96±3.26; CNR, 13.55±3.47) and all traditional VMI series (ptraditional VMI at abdominal DECT examinations. Copyright © 2018 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  14. Signal Amplification Technique (SAT): an approach for improving resolution and reducing image noise in computed tomography

    International Nuclear Information System (INIS)

    Phelps, M.E.; Huang, S.C.; Hoffman, E.J.; Plummer, D.; Carson, R.

    1981-01-01

    Spatial resolution improvements in computed tomography (CT) have been limited by the large and unique error propagation properties of this technique. The desire to provide maximum image resolution has resulted in the use of reconstruction filter functions designed to produce tomographic images with resolution as close as possible to the intrinsic detector resolution. Thus, many CT systems produce images with excessive noise with the system resolution determined by the detector resolution rather than the reconstruction algorithm. CT is a rigorous mathematical technique which applies an increasing amplification to increasing spatial frequencies in the measured data. This mathematical approach to spatial frequency amplification cannot distinguish between signal and noise and therefore both are amplified equally. We report here a method in which tomographic resolution is improved by using very small detectors to selectively amplify the signal and not noise. Thus, this approach is referred to as the signal amplification technique (SAT). SAT can provide dramatic improvements in image resolution without increases in statistical noise or dose because increases in the cutoff frequency of the reconstruction algorithm are not required to improve image resolution. Alternatively, in cases where image counts are low, such as in rapid dynamic or receptor studies, statistical noise can be reduced by lowering the cutoff frequency while still maintaining the best possible image resolution. A possible system design for a positron CT system with SAT is described

  15. Evolutionary Cellular Automata for Image Segmentation and Noise Filtering Using Genetic Algorithms

    Directory of Open Access Journals (Sweden)

    Sihem SLATNIA

    2011-01-01

    Full Text Available We use an evolutionary process to seek a specialized set of rules among a wide range of rules to be used by Cellular Automata (CA for a range of tasks,extracting edges in a given gray or colour image, noise filtering applied to black-white image. This is the best set of local rules determine the future state of CA in an asynchronous way. The Genetic Algorithm (GA is applied to search the best CA rules that can realize the best edge detection and noise filtering.

  16. Evolutionary Cellular Automata for Image Segmentation and Noise Filtering Using Genetic Algorithms

    Directory of Open Access Journals (Sweden)

    Okba Kazar

    2011-01-01

    Full Text Available We use an evolutionary process to seek a specialized set of rules among a wide range of rules to be used by Cellular Automata (CA for a range of tasks, extracting edges in a given gray or colour image, noise filtering applied to black-white image. This is the best set of local rules determine the future state of CA in an asynchronous way. The Genetic Algorithm (GA is applied to search the best CA rules that can realize the best edge detection and noise filtering.

  17. Thermal Infrared Imaging-Based Computational Psychophysiology for Psychometrics.

    Science.gov (United States)

    Cardone, Daniela; Pinti, Paola; Merla, Arcangelo

    2015-01-01

    Thermal infrared imaging has been proposed as a potential system for the computational assessment of human autonomic nervous activity and psychophysiological states in a contactless and noninvasive way. Through bioheat modeling of facial thermal imagery, several vital signs can be extracted, including localized blood perfusion, cardiac pulse, breath rate, and sudomotor response, since all these parameters impact the cutaneous temperature. The obtained physiological information could then be used to draw inferences about a variety of psychophysiological or affective states, as proved by the increasing number of psychophysiological studies using thermal infrared imaging. This paper presents therefore a review of the principal achievements of thermal infrared imaging in computational physiology with regard to its capability of monitoring psychophysiological activity.

  18. A Hybrid Technique for De-Noising Multi-Modality Medical Images by Employing Cuckoo’s Search with Curvelet Transform

    Directory of Open Access Journals (Sweden)

    Qaisar Javaid

    2018-01-01

    Full Text Available De-noising of the medical images is very difficult task. To improve the overall visual representation we need to apply a contrast enhancement techniques, this representation provide the physicians and clinicians a good and recovered diagnosis results. Various de-noising and contrast enhancements methods are develops. However, some of the methods are not good in providing the better results with accuracy and efficiency. In our paper we de-noise and enhance the medical images without any loss of information. We uses the curvelet transform in combination with ridglet transform along with CS (Cuckoo Search algorithm. The curvlet transform adapt and represents the sparse pixel informations with all edges. The edges play very important role in understanding of the images. Curvlet transform computes the edges very efficiently where the wavelets are failed. We used the CS to optimize the de-noising coefficients without loss of structural and morphological information. Our designed method would be accurate and efficient in de-noising the medical images. Our method attempts to remove the multiplicative and additive noises. Our proposed method is proved to be an efficient and reliable in removing all kind of noises from the medical images. Result indicates that our proposed approach is better than other approaches in removing impulse, Gaussian, and speckle noises.

  19. Noise analysis of a novel hybrid active-passive pixel sensor for medical X-ray imaging

    International Nuclear Information System (INIS)

    Safavian, N.; Izadi, M.H.; Sultana, A.; Wu, D.; Karim, K.S.; Nathan, A.; Rowlands, J.A.

    2009-01-01

    Passive pixel sensor (PPS) is one of the most widely used architectures in large area amorphous silicon (a-Si) flat panel imagers. It consists of a detector and a thin film transistor (TFT) acting as a readout switch. While the PPS is advantageous in terms of providing a simple and small architecture suitable for high-resolution imaging, it directly exposes the signal to the noise of data line and external readout electronics, causing significant increase in the minimum readable sensor input signal. In this work we present the operation and noise performance of a hybrid 3-TFT current programmed, current output active pixel sensor (APS) suitable for real-time X-ray imaging. The pixel circuit extends the application of a-Si TFT from conventional switching element to on-pixel amplifier for enhanced signal-to-noise ratio and higher imager dynamic range. The capability of operation in both passive and active modes as well as being able to compensate for inherent instabilities of the TFTs makes the architecture a good candidate for X-ray imaging modalities with a wide range of incoming X-ray intensities. Measurement and theoretical calculations reveal a value for input refferd noise below the 1000 electron noise limit for real-time fluoroscopy. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Overcoming thermal noise in non-volatile spin wave logic

    Science.gov (United States)

    Dutta, Sourav; Nikonov, Dmitri; Manipatruni, Sasikanth; Young, Ian; Naeemi, Azad

    Spin waves are propagating disturbances in magnetically ordered materials. To compete as a promising candidate for beyond-CMOS application, the all-magnon based computing system must undergo the essential steps of careful selection of materials and demonstrate robustness with respect to thermal noise/variability. Here, we identify suitable materials and investigate two viable options for translating the theoretical idea of phase-dependent switching of the spin wave detector to a practical realization of a thermally reliable magnonic device by - (a) using the built-in strain in the ME cell, arising from the lattice mismatch and/or thermal expansion coefficient mismatch between the film and the substrate, for compensation of the demagnetization, and (b) using an exchange-spring structure that exhibits a strong exchange-coupling between the ME cell and PMA SWB and provides a modification of the energy landscape of the ME cell magnet. A high switching success and error-free logic functionality can be ensured if the amplitude of the detected spin wave () remains higher than a threshold value of around 6°C and the detected phase falls within the window from 280°C through 0 to 20°C or from 100°C to 200°C with a maximum allowable ϕ range of around 100°C.

  1. Image processing methods for noise reduction in the TJ-II Thomson Scattering diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Dormido-Canto, S., E-mail: sebas@dia.uned.es [Departamento de Informatica y Automatica, UNED, Madrid 28040 (Spain); Farias, G. [Pontificia Universidad Catolica de Valparaiso, Valparaiso (Chile); Vega, J.; Pastor, I. [Asociacion EURATOM/CIEMAT para Fusion, Madrid 28040 (Spain)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer We describe an approach in order to reduce or mitigate the stray-light on the images and show the exceptional results. Black-Right-Pointing-Pointer We analyze the parameters to take account in the proposed process. Black-Right-Pointing-Pointer We report a simplified exampled in order to explain the proposed process. - Abstract: The Thomsom Scattering diagnostic of the TJ-II stellarator provides temperature and density profiles. The CCD camera acquires images corrupted with noise that, in some cases, can produce unreliable profiles. The main source of noise is the so-called stray-light. In this paper we describe an approach that allows mitigation of the effects that stray-light has on the images: extraction regions with connected-components. In addition, the robustness and effectiveness of the noise reduction technique is validated in two ways: (1) supervised classification and (2) comparison of electron temperature profiles.

  2. Improvement of material decomposition and image quality in dual-energy radiography by reducing image noise

    International Nuclear Information System (INIS)

    Lee, D.; Choi, S.; Kim, H.; Kim, H.-J.; Kim, Y.-S.; Choi, S.; Lee, H.; Jo, B.D.; Jeon, P.-H.; Kim, H.; Kim, D.

    2016-01-01

    Although digital radiography has been widely used for screening human anatomical structures in clinical situations, it has several limitations due to anatomical overlapping. To resolve this problem, dual-energy imaging techniques, which provide a method for decomposing overlying anatomical structures, have been suggested as alternative imaging techniques. Previous studies have reported several dual-energy techniques, each resulting in different image qualities. In this study, we compared three dual-energy techniques: simple log subtraction (SLS), simple smoothing of a high-energy image (SSH), and anti-correlated noise reduction (ACNR) with respect to material thickness quantification and image quality. To evaluate dual-energy radiography, we conducted Monte Carlo simulation and experimental phantom studies. The Geant 4 Application for Tomographic Emission (GATE) v 6.0 and tungsten anode spectral model using interpolation polynomials (TASMIP) codes were used for simulation studies and digital radiography, and human chest phantoms were used for experimental studies. The results of the simulation study showed improved image contrast-to-noise ratio (CNR) and coefficient of variation (COV) values and bone thickness estimation accuracy by applying the ACNR and SSH methods. Furthermore, the chest phantom images showed better image quality with the SSH and ACNR methods compared to the SLS method. In particular, the bone texture characteristics were well-described by applying the SSH and ACNR methods. In conclusion, the SSH and ACNR methods improved the accuracy of material quantification and image quality in dual-energy radiography compared to SLS. Our results can contribute to better diagnostic capabilities of dual-energy images and accurate material quantification in various clinical situations.

  3. Digital CDS for image sensors with dominant white and 1/f noise

    International Nuclear Information System (INIS)

    Stefanov, K.D.

    2015-01-01

    This paper investigates the performance of digital correlated double sampling (DCDS) for processing of image sensor signals in the presence of white and 1/f noise. The DCDS is compared with the dual slope integrator, which is the optimal analogue processing technique when only white noise is present. Based on the concept of matched filters, the paper derives and explores the optimal signal processing algorithms for signals with dominant 1/f noise, resulting in the highest achievable signal-to-noise ratio (SNR). Experimental results based on optimal DCDS on artificially generated 1/f noise signals are presented and discussed, together with the limitations of the method for more realistic sensor signals. It is shown that the noise level of the optimal DCDS can get close to the theoretical minimum

  4. Method and apparatus for implementing material thermal property measurement by flash thermal imaging

    Science.gov (United States)

    Sun, Jiangang

    2017-11-14

    A method and apparatus are provided for implementing measurement of material thermal properties including measurement of thermal effusivity of a coating and/or film or a bulk material of uniform property. The test apparatus includes an infrared camera, a data acquisition and processing computer coupled to the infrared camera for acquiring and processing thermal image data, a flash lamp providing an input of heat onto the surface of a two-layer sample with an enhanced optical filter covering the flash lamp attenuating an entire infrared wavelength range with a series of thermal images is taken of the surface of the two-layer sample.

  5. Restoration of Medical Images with Different Types of Noise; Restauracion de Imagenes Medicas con Diferentes Tipos de Ruido

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, M. G.; Vidal, V.; Verdu, G.; Mayo, P.; Rodenas, F.

    2013-07-01

    In this paper, a method is proposed to reduce the Gaussian, speckle and impulsive noise. This filter, named PGMFDNL filter combines a nonlinear diffusion and fuzzy peer group. The proposed filter can effectively reduce image noise without any information about the noise present in the image. As a result, the proposed method obtains good performance in different types of noise.

  6. Image Denoising Algorithm Combined with SGK Dictionary Learning and Principal Component Analysis Noise Estimation

    Directory of Open Access Journals (Sweden)

    Wenjing Zhao

    2018-01-01

    Full Text Available SGK (sequential generalization of K-means dictionary learning denoising algorithm has the characteristics of fast denoising speed and excellent denoising performance. However, the noise standard deviation must be known in advance when using SGK algorithm to process the image. This paper presents a denoising algorithm combined with SGK dictionary learning and the principal component analysis (PCA noise estimation. At first, the noise standard deviation of the image is estimated by using the PCA noise estimation algorithm. And then it is used for SGK dictionary learning algorithm. Experimental results show the following: (1 The SGK algorithm has the best denoising performance compared with the other three dictionary learning algorithms. (2 The SGK algorithm combined with PCA is superior to the SGK algorithm combined with other noise estimation algorithms. (3 Compared with the original SGK algorithm, the proposed algorithm has higher PSNR and better denoising performance.

  7. Measurement of macroscopic plasma parameters with a radio experiment: Interpretation of the quasi-thermal noise spectrum observed in the solar wind

    Science.gov (United States)

    Couturier, P.; Hoang, S.; Meyer-Vernet, N.; Steinberg, J. L.

    1983-01-01

    The ISEE-3 SBH radio receiver has provided the first systematic observations of the quasi-thermal (plasma waves) noise in the solar wind plasma. The theoretical interpretation of that noise involves the particle distribution function so that electric noise measurements with long antennas provide a fast and independent method of measuring plasma parameters: densities and temperatures of a two component (core and halo) electron distribution function have been obtained in that way. The polarization of that noise is frequency dependent and sensitive to the drift velocity of the electron population. Below the plasma frequency, there is evidence of a weak noise spectrum with spectral index -1 which is not yet accounted for by the theory. The theoretical treatment of the noise associated with the low energy (thermal) proton population shows that the moving electrical antenna radiates in the surrounding plasma by Carenkov emission which becomes predominant at the low frequencies, below about 0.1 F sub P.

  8. Hand Depth Image Denoising and Superresolution via Noise-Aware Dictionaries

    Directory of Open Access Journals (Sweden)

    Huayang Li

    2016-01-01

    Full Text Available This paper proposes a two-stage method for hand depth image denoising and superresolution, using bilateral filters and learned dictionaries via noise-aware orthogonal matching pursuit (NAOMP based K-SVD. The bilateral filtering phase recovers singular points and removes artifacts on silhouettes by averaging depth data using neighborhood pixels on which both depth difference and RGB similarity restrictions are imposed. The dictionary learning phase uses NAOMP for training dictionaries which separates faithful depth from noisy data. Compared with traditional OMP, NAOMP adds a residual reduction step which effectively weakens the noise term within the residual during the residual decomposition in terms of atoms. Experimental results demonstrate that the bilateral phase and the NAOMP-based learning dictionaries phase corporately denoise both virtual and real depth images effectively.

  9. A Hybrid Method of medical Image Restoration with Gaussian and Impulsive Noise; Un Metodo Hibrido de Restauracion de Images Medidas con Ruido Gausino e Impulsivo

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, M. G.; Vidal, V.; Verdu, G.; Mayo, P.; Rodenas, F.

    2011-07-01

    The noise removal techniques to restore noisy images is currently an important issue, for example, medical images obtained by X-ray computed tomography in noise due to the use of a small number of projections present noise of different types. In this paper we analyze and evaluate two techniques that separately each behaves efficiently for the removal of Gaussian and impulsive noise respectively, and combined to form a hybrid approach obtains very good performance with respect to quality in most different types of noise.

  10. Signal-to-noise ratio analysis and evaluation of the Hadamard imaging technique

    Science.gov (United States)

    Jobson, D. J.; Katzberg, S. J.; Spiers, R. B., Jr.

    1977-01-01

    The signal-to-noise ratio performance of the Hadamard imaging technique is analyzed and an experimental evaluation of a laboratory Hadamard imager is presented. A comparison between the performances of Hadamard and conventional imaging techniques shows that the Hadamard technique is superior only when the imaging objective lens is required to have an effective F (focus) number of about 2 or slower.

  11. Development of flow velocity measurement techniques in visible images. Improvement of particle image velocimetry techniques on image process

    International Nuclear Information System (INIS)

    Kimura, Nobuyuki; Nishimura, Motohiko; Kamide, Hideki; Hishida, Koichi

    1999-10-01

    Noise reduction system was developed to improve applicability of Particle Image Velocimetry (PIV) to complicated configure bounded flows. For fast reactor safety and thermal hydraulic studies, experiments are performed in scale models which usually have rather complicated geometry and structures such as fuel subassemblies, heat exchangers, etc. The structures and stuck dusts on the view window of the models obscure the particle image. Thus the image except the moving particles can be regarded as a noise. In the present study, two noise reduction techniques are proposed. The one is the Time-averaged Light Intensity Subtraction method (TIS) which subtracts the time-averaged light intensity of each pixel in the sequential images from the each corresponding pixel. The other one is the Minimum Light Intensity Subtraction method (MIS) which subtracts the minimum light intensity of each pixel in the sequential images from the each corresponding pixel. Both methods are examined on their capabilities of noise reduction. As for the original 'bench mark' image, the image made from Large Eddy Simulation was used. To the bench mark image, noises are added which are referred as sample images. Both methods reduce the rate of vector with the error of more than one pixel from 90% to less than 5%. Also, more than 50% of the vectors have the error of less than 0.2 pixel. The analysis of uncertainty shows that these methods enhances the accuracy of vector measurement 3 ∼ 12 times if the image with noise were processed, and the MIS method has 1.1 ∼ 2.1 times accuracy compared to the TIS. Thus the present noise reduction methods are quite efficient to enhance the accuracy of flow velocity fields measured with particle images including structures and deposits on the view window. (author)

  12. Performance Evaluation Facility for Fire Fighting Thermal Imager

    International Nuclear Information System (INIS)

    Kim, Sung Chan; Amon, Francine; Hamins, Anthony

    2007-01-01

    The present study investigates the characteristics of obscuring media inside an optical smoke cell, which is a bench-scale testing facility for the evaluation of thermal imaging cameras used by fire fighters. Light extinction coefficient and visibility through the smoke cell is characterized by the measured laser transmittance. The laser transmittance along the axial direction of the smoke cell is relatively uniform at upper and lower part for various air/fuel volume flow rate. Contrast level based image quality of visible CCD camera through the smoke cell is compared with that of thermal imaging camera. The optical smoke cell can be used as well-controlled and effective laboratory-scale test apparatus to evaluate the performance of thermal imaging camera for fire fighting application

  13. Blind deblurring of spiral CT images - comparative studies on edge-to-noise ratios

    International Nuclear Information System (INIS)

    Jiang Ming; Wan Ge; Skinner, Margaret W.; Rubinstein, Jay T.; Vannier, Michael W.

    2002-01-01

    A recently developed blind deblurring algorithm based on the edge-to-noise ratio has been applied to improve the quality of spiral CT images. Since the discrepancy measure used to quantify the edge and noise effects is not symmetric, there are several ways to formulate the edge-to-noise ratio. This article is to investigate the performance of those ratios with phantom and patient data. In the phantom study, it is shown that all the ratios share similar properties, validating the blind deblurring algorithm. The image fidelity improvement varies from 29% to 33% for different ratios, according to the root mean square error (RMSE) criterion; the optimal iteration number determined for each ratio varies from 25 to 35. Those ratios that are associated with most satisfactory performance are singled out for the image fidelity improvement of about 33% in the numerical simulation. After automatic blind deblurring with the selected ratios, the spatial resolution of CT is substantially refined in all the cases tested

  14. Elimination of white Gaussian noise in arterial phase CT images to bring adrenal tumours into the forefront.

    Science.gov (United States)

    Koyuncu, Hasan; Ceylan, Rahime

    2018-04-01

    Dynamic Contrast-Enhanced Computed Tomography (DCE-CT) is applied to observe adrenal tumours in detail by utilising from the contrast matter, which generally brings the tumour into the forefront. However, DCE-CT images are generally influenced by noises that occur as the result of the trade-off between radiation doses vs. noise. Herein, this situation constitutes a challenge in the achievement of accurate tumour segmentation. In CT images, most of the noises are similar to Gaussian Noise. In this study, arterial phase CT images containing adrenal tumours are utilised, and elimination of Gaussian Noise is realised by fourteen different techniques reported in literature for the achievement of the best denoising process. In this study, the Block Matching and 3D Filtering (BM3D) algorithm typically achieve reliable Peak Signal-to-Noise Ratios (PSNR) and resolves challenges of similar techniques when addressing different levels of noise. Furthermore, BM3D obtains the best mean PSNR values among the first five techniques. BM3D outperforms to other techniques by obtaining better Total Statistical Success (TSS), CPU time and computation cost. Consequently, it prepares clearer arterial phase CT images for the next step (segmentation of adrenal tumours). Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Multispectral thermal imaging

    Energy Technology Data Exchange (ETDEWEB)

    Weber, P.G.; Bender, S.C.; Borel, C.C.; Clodius, W.B.; Smith, B.W. [Los Alamos National Lab., NM (United States). Space and Remote Sensing Sciences Group; Garrett, A.; Pendergast, M.M. [Westinghouse Savannah River Corp., Aiken, SC (United States). Savannah River Technology Center; Kay, R.R. [Sandia National Lab., Albuquerque, NM (United States). Monitoring Systems and Technology Center

    1998-12-01

    Many remote sensing applications rely on imaging spectrometry. Here the authors use imaging spectrometry for thermal and multispectral signatures measured from a satellite platform enhanced with a combination of accurate calibrations and on-board data for correcting atmospheric distortions. The approach is supported by physics-based end-to-end modeling and analysis, which permits a cost-effective balance between various hardware and software aspects. The goal is to develop and demonstrate advanced technologies and analysis tools toward meeting the needs of the customer; at the same time, the attributes of this system can address other applications in such areas as environmental change, agriculture, and volcanology.

  16. Adaptive HIFU noise cancellation for simultaneous therapy and imaging using an integrated HIFU/imaging transducer.

    Science.gov (United States)

    Jeong, Jong Seob; Cannata, Jonathan Matthew; Shung, K Kirk

    2010-04-07

    It was previously demonstrated that it is feasible to simultaneously perform ultrasound therapy and imaging of a coagulated lesion during treatment with an integrated transducer that is capable of high intensity focused ultrasound (HIFU) and B-mode ultrasound imaging. It was found that coded excitation and fixed notch filtering upon reception could significantly reduce interference caused by the therapeutic transducer. During HIFU sonication, the imaging signal generated with coded excitation and fixed notch filtering had a range side-lobe level of less than -40 dB, while traditional short-pulse excitation and fixed notch filtering produced a range side-lobe level of -20 dB. The shortcoming is, however, that relatively complicated electronics may be needed to utilize coded excitation in an array imaging system. It is for this reason that in this paper an adaptive noise canceling technique is proposed to improve image quality by minimizing not only the therapeutic interference, but also the remnant side-lobe 'ripples' when using the traditional short-pulse excitation. The performance of this technique was verified through simulation and experiments using a prototype integrated HIFU/imaging transducer. Although it is known that the remnant ripples are related to the notch attenuation value of the fixed notch filter, in reality, it is difficult to find the optimal notch attenuation value due to the change in targets or the media resulted from motion or different acoustic properties even during one sonication pulse. In contrast, the proposed adaptive noise canceling technique is capable of optimally minimizing both the therapeutic interference and residual ripples without such constraints. The prototype integrated HIFU/imaging transducer is composed of three rectangular elements. The 6 MHz center element is used for imaging and the outer two identical 4 MHz elements work together to transmit the HIFU beam. Two HIFU elements of 14.4 mm x 20.0 mm dimensions could

  17. Adaptive HIFU noise cancellation for simultaneous therapy and imaging using an integrated HIFU/imaging transducer

    International Nuclear Information System (INIS)

    Jeong, Jong Seob; Cannata, Jonathan Matthew; Shung, K Kirk

    2010-01-01

    It was previously demonstrated that it is feasible to simultaneously perform ultrasound therapy and imaging of a coagulated lesion during treatment with an integrated transducer that is capable of high intensity focused ultrasound (HIFU) and B-mode ultrasound imaging. It was found that coded excitation and fixed notch filtering upon reception could significantly reduce interference caused by the therapeutic transducer. During HIFU sonication, the imaging signal generated with coded excitation and fixed notch filtering had a range side-lobe level of less than -40 dB, while traditional short-pulse excitation and fixed notch filtering produced a range side-lobe level of -20 dB. The shortcoming is, however, that relatively complicated electronics may be needed to utilize coded excitation in an array imaging system. It is for this reason that in this paper an adaptive noise canceling technique is proposed to improve image quality by minimizing not only the therapeutic interference, but also the remnant side-lobe 'ripples' when using the traditional short-pulse excitation. The performance of this technique was verified through simulation and experiments using a prototype integrated HIFU/imaging transducer. Although it is known that the remnant ripples are related to the notch attenuation value of the fixed notch filter, in reality, it is difficult to find the optimal notch attenuation value due to the change in targets or the media resulted from motion or different acoustic properties even during one sonication pulse. In contrast, the proposed adaptive noise canceling technique is capable of optimally minimizing both the therapeutic interference and residual ripples without such constraints. The prototype integrated HIFU/imaging transducer is composed of three rectangular elements. The 6 MHz center element is used for imaging and the outer two identical 4 MHz elements work together to transmit the HIFU beam. Two HIFU elements of 14.4 mm x 20.0 mm dimensions could

  18. Thermal particle image velocity estimation of fire plume flow

    Science.gov (United States)

    Xiangyang Zhou; Lulu Sun; Shankar Mahalingam; David R. Weise

    2003-01-01

    For the purpose of studying wildfire spread in living vegetation such as chaparral in California, a thermal particle image velocity (TPIV) algorithm for nonintrusively measuring flame gas velocities through thermal infrared (IR) imagery was developed. By tracing thermal particles in successive digital IR images, the TPIV algorithm can estimate the velocity field in a...

  19. Noise and physical limits to maximum resolution of PET images

    Energy Technology Data Exchange (ETDEWEB)

    Herraiz, J.L.; Espana, S. [Dpto. Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain); Vicente, E.; Vaquero, J.J.; Desco, M. [Unidad de Medicina y Cirugia Experimental, Hospital GU ' Gregorio Maranon' , E-28007 Madrid (Spain); Udias, J.M. [Dpto. Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain)], E-mail: jose@nuc2.fis.ucm.es

    2007-10-01

    In this work we show that there is a limit for the maximum resolution achievable with a high resolution PET scanner, as well as for the best signal-to-noise ratio, which are ultimately related to the physical effects involved in the emission and detection of the radiation and thus they cannot be overcome with any particular reconstruction method. These effects prevent the spatial high frequency components of the imaged structures to be recorded by the scanner. Therefore, the information encoded in these high frequencies cannot be recovered by any reconstruction technique. Within this framework, we have determined the maximum resolution achievable for a given acquisition as a function of data statistics and scanner parameters, like the size of the crystals or the inter-crystal scatter. In particular, the noise level in the data as a limitation factor to yield high-resolution images in tomographs with small crystal sizes is outlined. These results have implications regarding how to decide the optimal number of voxels of the reconstructed image or how to design better PET scanners.

  20. Noise and physical limits to maximum resolution of PET images

    International Nuclear Information System (INIS)

    Herraiz, J.L.; Espana, S.; Vicente, E.; Vaquero, J.J.; Desco, M.; Udias, J.M.

    2007-01-01

    In this work we show that there is a limit for the maximum resolution achievable with a high resolution PET scanner, as well as for the best signal-to-noise ratio, which are ultimately related to the physical effects involved in the emission and detection of the radiation and thus they cannot be overcome with any particular reconstruction method. These effects prevent the spatial high frequency components of the imaged structures to be recorded by the scanner. Therefore, the information encoded in these high frequencies cannot be recovered by any reconstruction technique. Within this framework, we have determined the maximum resolution achievable for a given acquisition as a function of data statistics and scanner parameters, like the size of the crystals or the inter-crystal scatter. In particular, the noise level in the data as a limitation factor to yield high-resolution images in tomographs with small crystal sizes is outlined. These results have implications regarding how to decide the optimal number of voxels of the reconstructed image or how to design better PET scanners

  1. Signal-to-noise ratio enhancement on SEM images using a cubic spline interpolation with Savitzky-Golay filters and weighted least squares error.

    Science.gov (United States)

    Kiani, M A; Sim, K S; Nia, M E; Tso, C P

    2015-05-01

    A new technique based on cubic spline interpolation with Savitzky-Golay smoothing using weighted least squares error filter is enhanced for scanning electron microscope (SEM) images. A diversity of sample images is captured and the performance is found to be better when compared with the moving average and the standard median filters, with respect to eliminating noise. This technique can be implemented efficiently on real-time SEM images, with all mandatory data for processing obtained from a single image. Noise in images, and particularly in SEM images, are undesirable. A new noise reduction technique, based on cubic spline interpolation with Savitzky-Golay and weighted least squares error method, is developed. We apply the combined technique to single image signal-to-noise ratio estimation and noise reduction for SEM imaging system. This autocorrelation-based technique requires image details to be correlated over a few pixels, whereas the noise is assumed to be uncorrelated from pixel to pixel. The noise component is derived from the difference between the image autocorrelation at zero offset, and the estimation of the corresponding original autocorrelation. In the few test cases involving different images, the efficiency of the developed noise reduction filter is proved to be significantly better than those obtained from the other methods. Noise can be reduced efficiently with appropriate choice of scan rate from real-time SEM images, without generating corruption or increasing scanning time. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  2. Characterization of 3 to 5 Micron Thermal Imagers and Analysis of Narrow Band Images

    National Research Council Canada - National Science Library

    Quek, Yew S

    2004-01-01

    ...) and the Minimum Resolvable Temperature (MRT). An available thermal imager, the Cincinnati Electronics IRRIS-256LN, and a newly purchased thermal imager, the Indigo Systems Merlin InSb Laboratory Camera, were investigated and compared...

  3. Generalized INverse imaging (GIN): ultrafast fMRI with physiological noise correction.

    Science.gov (United States)

    Boyacioğlu, Rasim; Barth, Markus

    2013-10-01

    An ultrafast functional magnetic resonance imaging (fMRI) technique, called generalized inverse imaging (GIN), is proposed, which combines inverse imaging with a phase constraint-leading to a less underdetermined reconstruction-and physiological noise correction. A single 3D echo planar imaging (EPI) prescan is sufficient to obtain the necessary coil sensitivity information and reference images that are used to reconstruct standard images, so that standard analysis methods are applicable. A moving dots stimulus paradigm was chosen to assess the performance of GIN. We find that the spatial localization of activation for GIN is comparable to an EPI protocol and that maximum z-scores increase significantly. The high temporal resolution of GIN (50 ms) and the acquisition of the phase information enable unaliased sampling and regression of physiological signals. Using the phase time courses obtained from the 32 channels of the receiver coils as nuisance regressors in a general linear model results in significant improvement of the functional activation, rendering the acquisition of external physiological signals unnecessary. The proposed physiological noise correction can in principle be used for other fMRI protocols, such as simultaneous multislice acquisitions, which acquire the phase information sufficiently fast and sample physiological signals unaliased. Copyright © 2012 Wiley Periodicals, Inc.

  4. Effect of drain current on appearance probability and amplitude of random telegraph noise in low-noise CMOS image sensors

    Science.gov (United States)

    Ichino, Shinya; Mawaki, Takezo; Teramoto, Akinobu; Kuroda, Rihito; Park, Hyeonwoo; Wakashima, Shunichi; Goto, Tetsuya; Suwa, Tomoyuki; Sugawa, Shigetoshi

    2018-04-01

    Random telegraph noise (RTN), which occurs in in-pixel source follower (SF) transistors, has become one of the most critical problems in high-sensitivity CMOS image sensors (CIS) because it is a limiting factor of dark random noise. In this paper, the behaviors of RTN toward changes in SF drain current conditions were analyzed using a low-noise array test circuit measurement system with a floor noise of 35 µV rms. In addition to statistical analysis by measuring a large number of transistors (18048 transistors), we also analyzed the behaviors of RTN parameters such as amplitude and time constants in the individual transistors. It is demonstrated that the appearance probability of RTN becomes small under a small drain current condition, although large-amplitude RTN tends to appear in a very small number of cells.

  5. Measuring multielectron beam imaging fidelity with a signal-to-noise ratio analysis

    Science.gov (United States)

    Mukhtar, Maseeh; Bunday, Benjamin D.; Quoi, Kathy; Malloy, Matt; Thiel, Brad

    2016-07-01

    Java Monte Carlo Simulator for Secondary Electrons (JMONSEL) simulations are used to generate expected imaging responses of chosen test cases of patterns and defects with the ability to vary parameters for beam energy, spot size, pixel size, and/or defect material and form factor. The patterns are representative of the design rules for an aggressively scaled FinFET-type design. With these simulated images and resulting shot noise, a signal-to-noise framework is developed, which relates to defect detection probabilities. Additionally, with this infrastructure, the effect of detection chain noise and frequency-dependent system response can be made, allowing for targeting of best recipe parameters for multielectron beam inspection validation experiments. Ultimately, these results should lead to insights into how such parameters will impact tool design, including necessary doses for defect detection and estimations of scanning speeds for achieving high throughput for high-volume manufacturing.

  6. Background Noise Removal in Ultrasonic B-scan Images Using Iterative Statistical Techniques

    NARCIS (Netherlands)

    Wells, I.; Charlton, P. C.; Mosey, S.; Donne, K. E.

    2008-01-01

    The interpretation of ultrasonic B-scan images can be a time-consuming process and its success depends on operator skills and experience. Removal of the image background will potentially improve its quality and hence improve operator diagnosis. An automatic background noise removal algorithm is

  7. Generation of synthetic Kinect depth images based on empirical noise model

    DEFF Research Database (Denmark)

    Iversen, Thorbjørn Mosekjær; Kraft, Dirk

    2017-01-01

    The development, training and evaluation of computer vision algorithms rely on the availability of a large number of images. The acquisition of these images can be time-consuming if they are recorded using real sensors. An alternative is to rely on synthetic images which can be rapidly generated....... This Letter describes a novel method for the simulation of Kinect v1 depth images. The method is based on an existing empirical noise model from the literature. The authors show that their relatively simple method is able to provide depth images which have a high similarity with real depth images....

  8. Measurement and analysis of noise power spectrum of computerized tomography in images

    International Nuclear Information System (INIS)

    Castro Tejero, P.; Garayoa Roca, J.

    2013-01-01

    This paper examines the implementation of the spectrum of powers of the noise, NPS, as metric to characterize the noise, both in magnitude and in texture, for CT scans. The NPS found show that you for convolution filters that assume a greater softening in the reconstructed image, spectrum is concentrated in the low frequencies, while for filters sharp, the spectrum extends to high frequencies. In the analyzed cases, there is a low frequency component, largely due to the structure-borne noise, which can be a potential negative effect on the detectability of injuries. (Author)

  9. Automated thermal mapping techniques using chromatic image analysis

    Science.gov (United States)

    Buck, Gregory M.

    1989-01-01

    Thermal imaging techniques are introduced using a chromatic image analysis system and temperature sensitive coatings. These techniques are used for thermal mapping and surface heat transfer measurements on aerothermodynamic test models in hypersonic wind tunnels. Measurements are made on complex vehicle configurations in a timely manner and at minimal expense. The image analysis system uses separate wavelength filtered images to analyze surface spectral intensity data. The system was initially developed for quantitative surface temperature mapping using two-color thermographic phosphors but was found useful in interpreting phase change paint and liquid crystal data as well.

  10. Low-power low-noise mixed-mode VLSI ASIC for infinite dynamic range imaging applications

    Science.gov (United States)

    Turchetta, Renato; Hu, Y.; Zinzius, Y.; Colledani, C.; Loge, A.

    1998-11-01

    Solid state solutions for imaging are mainly represented by CCDs and, more recently, by CMOS imagers. Both devices are based on the integration of the total charge generated by the impinging radiation, with no processing of the single photon information. The dynamic range of these devices is intrinsically limited by the finite value of noise. Here we present the design of an architecture which allows efficient, in-pixel, noise reduction to a practically zero level, thus allowing infinite dynamic range imaging. A detailed calculation of the dynamic range is worked out, showing that noise is efficiently suppressed. This architecture is based on the concept of single-photon counting. In each pixel, we integrate both the front-end, low-noise, low-power analog part and the digital part. The former consists of a charge preamplifier, an active filter for optimal noise bandwidth reduction, a buffer and a threshold comparator, and the latter is simply a counter, which can be programmed to act as a normal shift register for the readout of the counters' contents. Two different ASIC's based on this concept have been designed for different applications. The first one has been optimized for silicon edge-on microstrips detectors, used in a digital mammography R and D project. It is a 32-channel circuit, with a 16-bit binary static counter.It has been optimized for a relatively large detector capacitance of 5 pF. Noise has been measured to be equal to 100 + 7*Cd (pF) electron rms with the digital part, showing no degradation of the noise performances with respect to the design values. The power consumption is 3.8mW/channel for a peaking time of about 1 microsecond(s) . The second circuit is a prototype for pixel imaging. The total active area is about (250 micrometers )**2. The main differences of the electronic architecture with respect to the first prototype are: i) different optimization of the analog front-end part for low-capacitance detectors, ii) in- pixel 4-bit comparator

  11. Thermal imaging for current D&S priorities

    Science.gov (United States)

    Craig, Robert; Parsons, John F.

    2012-11-01

    Supplying thermal imagers for today's operational needs requires flexibility, responsiveness and ever reducing costs. This paper will use the latest thermal imager development in the Catherine range from Thales UK to address the technical interactions with such issues as modularity, re-use, regions of deployment and supply chain management. All this is in the context of the increasingly public operations and the pressures on validating performance especially when weapon aiming is involved.

  12. QR code based noise-free optical encryption and decryption of a gray scale image

    Science.gov (United States)

    Jiao, Shuming; Zou, Wenbin; Li, Xia

    2017-03-01

    In optical encryption systems, speckle noise is one major challenge in obtaining high quality decrypted images. This problem can be addressed by employing a QR code based noise-free scheme. Previous works have been conducted for optically encrypting a few characters or a short expression employing QR codes. This paper proposes a practical scheme for optically encrypting and decrypting a gray-scale image based on QR codes for the first time. The proposed scheme is compatible with common QR code generators and readers. Numerical simulation results reveal the proposed method can encrypt and decrypt an input image correctly.

  13. Formation of the image on the receiver of thermal radiation

    Science.gov (United States)

    Akimenko, Tatiana A.

    2018-04-01

    The formation of the thermal picture of the observed scene with the verification of the quality of the thermal images obtained is one of the important stages of the technological process that determine the quality of the thermal imaging observation system. In this article propose to consider a model for the formation of a thermal picture of a scene, which must take into account: the features of the object of observation as the source of the signal; signal transmission through the physical elements of the thermal imaging system that produce signal processing at the optical, photoelectronic and electronic stages, which determines the final parameters of the signal and its compliance with the requirements for thermal information and measurement systems.

  14. Period doubling induced by thermal noise amplification in genetic circuits

    KAUST Repository

    Ruocco, G.

    2014-11-18

    Rhythms of life are dictated by oscillations, which take place in a wide rage of biological scales. In bacteria, for example, oscillations have been proven to control many fundamental processes, ranging from gene expression to cell divisions. In genetic circuits, oscillations originate from elemental block such as autorepressors and toggle switches, which produce robust and noise-free cycles with well defined frequency. In some circumstances, the oscillation period of biological functions may double, thus generating bistable behaviors whose ultimate origin is at the basis of intense investigations. Motivated by brain studies, we here study an “elemental” genetic circuit, where a simple nonlinear process interacts with a noisy environment. In the proposed system, nonlinearity naturally arises from the mechanism of cooperative stability, which regulates the concentration of a protein produced during a transcription process. In this elemental model, bistability results from the coherent amplification of environmental fluctuations due to a stochastic resonance of nonlinear origin. This suggests that the period doubling observed in many biological functions might result from the intrinsic interplay between nonlinearity and thermal noise.

  15. A NOISE ADAPTIVE FUZZY EQUALIZATION METHOD FOR PROCESSING SOLAR EXTREME ULTRAVIOLET IMAGES

    Energy Technology Data Exchange (ETDEWEB)

    Druckmueller, M., E-mail: druckmuller@fme.vutbr.cz [Institute of Mathematics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, 616 69 Brno (Czech Republic)

    2013-08-15

    A new image enhancement tool ideally suited for the visualization of fine structures in extreme ultraviolet images of the corona is presented in this paper. The Noise Adaptive Fuzzy Equalization method is particularly suited for the exceptionally high dynamic range images from the Atmospheric Imaging Assembly instrument on the Solar Dynamics Observatory. This method produces artifact-free images and gives significantly better results than methods based on convolution or Fourier transform which are often used for that purpose.

  16. Laser-induced photo-thermal strain imaging

    Science.gov (United States)

    Choi, Changhoon; Ahn, Joongho; Jeon, Seungwan; Kim, Chulhong

    2018-02-01

    Vulnerable plaque is the one of the leading causes of cardiovascular disease occurrence. However, conventional intravascular imaging techniques suffer from difficulty in finding vulnerable plaque due to limitation such as lack of physiological information, imaging depth, and depth sensitivity. Therefore, new techniques are needed to help determine the vulnerability of plaque, Thermal strain imaging (TSI) is an imaging technique based on ultrasound (US) wave propagation speed that varies with temperature of medium. During temperature increase, strain occurs in the medium and its variation tendency is depending on the type of tissue, which makes it possible to use for tissue differentiation. Here, we demonstrate laser-induced photo-thermal strain imaging (pTSI) to differentiate tissue using an intravascular ultrasound (IVUS) catheter and a 1210-nm continuous-wave laser for heating lipids intensively. During heating, consecutive US images were obtained from a custom-made phantom made of porcine fat and gelatin. A cross correlation-based speckle-tracking algorithm was then applied to calculate the strain of US images. In the strain images, the positive strain produced in lipids (porcine fat) was clearly differentiated from water-bearing tissue (gelatin). This result shows that laser-induced pTSI could be a new method to distinguish lipids in the plaque and can help to differentiate vulnerability of plaque.

  17. Thermal Imaging Systems for Real-Time Applications in Smart Cities

    DEFF Research Database (Denmark)

    Gade, Rikke; Moeslund, Thomas B.; Nielsen, Søren Zebitz

    2016-01-01

    of thermal imaging in real-time Smart City applications. Thermal cameras operate independently of light and measure the radiated infrared waves representing the temperature of the scene. In order to showcase the possibilities, we present five different applications which use thermal imaging only...

  18. Use of a hybrid iterative reconstruction technique to reduce image noise and improve image quality in obese patients undergoing computed tomographic pulmonary angiography.

    Science.gov (United States)

    Kligerman, Seth; Mehta, Dhruv; Farnadesh, Mahmmoudreza; Jeudy, Jean; Olsen, Kathryn; White, Charles

    2013-01-01

    To determine whether an iterative reconstruction (IR) technique (iDose, Philips Healthcare) can reduce image noise and improve image quality in obese patients undergoing computed tomographic pulmonary angiography (CTPA). The study was Health Insurance Portability and Accountability Act compliant and approved by our institutional review board. A total of 33 obese patients (average body mass index: 42.7) underwent CTPA studies following standard departmental protocols. The data were reconstructed with filtered back projection (FBP) and 3 iDose strengths (iDoseL1, iDoseL3, and iDoseL5) for a total of 132 studies. FBP data were collected from 33 controls (average body mass index: 22) undergoing CTPA. Regions of interest were drawn at 6 identical levels in the pulmonary artery (PA), from the main PA to a subsegmental branch, in both the control group and study groups using each algorithm. Noise and attenuation were measured at all PA levels. Three thoracic radiologists graded each study on a scale of 1 (very poor) to 5 (ideal) by 4 categories: image quality, noise, PA enhancement, and "plastic" appearance. Statistical analysis was performed using an unpaired t test, 1-way analysis of variance, and linear weighted κ. Compared with the control group, there was significantly higher noise with FBP, iDoseL1, and iDoseL3 algorithms (Pnoise in the control group and iDoseL5 algorithm in the study group. Analysis within the study group showed a significant and progressive decrease in noise and increase in the contrast-to-noise ratio as the level of IR was increased (Pnoise and PA enhancement with increasing levels of iDose. The use of an IR technique leads to qualitative and quantitative improvements in image noise and image quality in obese patients undergoing CTPA.

  19. Median filters as a tool to determine dark noise thresholds in high resolution smartphone image sensors for scientific imaging

    Science.gov (United States)

    Igoe, Damien P.; Parisi, Alfio V.; Amar, Abdurazaq; Rummenie, Katherine J.

    2018-01-01

    An evaluation of the use of median filters in the reduction of dark noise in smartphone high resolution image sensors is presented. The Sony Xperia Z1 employed has a maximum image sensor resolution of 20.7 Mpixels, with each pixel having a side length of just over 1 μm. Due to the large number of photosites, this provides an image sensor with very high sensitivity but also makes them prone to noise effects such as hot-pixels. Similar to earlier research with older models of smartphone, no appreciable temperature effects were observed in the overall average pixel values for images taken in ambient temperatures between 5 °C and 25 °C. In this research, hot-pixels are defined as pixels with intensities above a specific threshold. The threshold is determined using the distribution of pixel values of a set of images with uniform statistical properties associated with the application of median-filters of increasing size. An image with uniform statistics was employed as a training set from 124 dark images, and the threshold was determined to be 9 digital numbers (DN). The threshold remained constant for multiple resolutions and did not appreciably change even after a year of extensive field use and exposure to solar ultraviolet radiation. Although the temperature effects' uniformity masked an increase in hot-pixel occurrences, the total number of occurrences represented less than 0.1% of the total image. Hot-pixels were removed by applying a median filter, with an optimum filter size of 7 × 7; similar trends were observed for four additional smartphone image sensors used for validation. Hot-pixels were also reduced by decreasing image resolution. The method outlined in this research provides a methodology to characterise the dark noise behavior of high resolution image sensors for use in scientific investigations, especially as pixel sizes decrease.

  20. Pediatric CT: implementation of ASIR for substantial radiation dose reduction while maintaining pre-ASIR image noise.

    Science.gov (United States)

    Brady, Samuel L; Moore, Bria M; Yee, Brian S; Kaufman, Robert A

    2014-01-01

    To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient. The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current-modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests. With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT. Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose reduction tool only; no net change to the magnitude

  1. Noise analysis of grating-based x-ray differential phase-contrast imaging with angular signal radiography

    International Nuclear Information System (INIS)

    Faiz, Wali; Gao Kun; Wu Zhao; Wei Chen-Xi; Zan Gui-Bin; Tian Yang-Chao; Bao Yuan; Zhu Pei-Ping

    2017-01-01

    X-ray phase-contrast imaging is one of the novel techniques, and has potential to enhance image quality and provide the details of inner structures nondestructively. In this work, we investigate quantitatively signal-to-noise ratio (SNR) of grating-based x-ray phase contrast imaging (GBPCI) system by employing angular signal radiography (ASR). Moreover, photon statistics and mechanical error that is a major source of noise are investigated in detail. Results show the dependence of SNR on the system parameters and the effects on the extracted absorption, refraction and scattering images. Our conclusions can be used to optimize the system design for upcoming practical applications in the areas such as material science and biomedical imaging. (paper)

  2. Dual-Energy Computed Tomography Angiography of the Lower Extremity Runoff: Impact of Noise-Optimized Virtual Monochromatic Imaging on Image Quality and Diagnostic Accuracy.

    Science.gov (United States)

    Wichmann, Julian L; Gillott, Matthew R; De Cecco, Carlo N; Mangold, Stefanie; Varga-Szemes, Akos; Yamada, Ricardo; Otani, Katharina; Canstein, Christian; Fuller, Stephen R; Vogl, Thomas J; Todoran, Thomas M; Schoepf, U Joseph

    2016-02-01

    The aim of this study was to evaluate the impact of a noise-optimized virtual monochromatic imaging algorithm (VMI+) on image quality and diagnostic accuracy at dual-energy computed tomography angiography (CTA) of the lower extremity runoff. This retrospective Health Insurance Portability and Accountability Act-compliant study was approved by the local institutional review board. We evaluated dual-energy CTA studies of the lower extremity runoff in 48 patients (16 women; mean age, 63.3 ± 13.8 years) performed on a third-generation dual-source CT system. Images were reconstructed with standard linear blending (F_0.5), VMI+, and traditional monochromatic (VMI) algorithms at 40 to 120 keV in 10-keV intervals. Vascular attenuation and image noise in 18 artery segments were measured; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Five-point scales were used to subjectively evaluate vascular attenuation and image noise. In a subgroup of 21 patients who underwent additional invasive catheter angiography, diagnostic accuracy for the detection of significant stenosis (≥50% lumen restriction) of F_0.5, 50-keV VMI+, and 60-keV VMI data sets were assessed. Objective image quality metrics were highest in the 40- and 50-keV VMI+ series (SNR: 20.2 ± 10.7 and 19.0 ± 9.5, respectively; CNR: 18.5 ± 10.3 and 16.8 ± 9.1, respectively) and were significantly (all P traditional VMI technique and standard linear blending for evaluation of the lower extremity runoff using dual-energy CTA.

  3. Technique Based on Image Pyramid and Bayes Rule for Noise Reduction in Unsupervised Change Detection

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-qiang; HUO hong; FANG Tao; ZHU Ju-lian; GE Wei-li

    2009-01-01

    In this paper, a technique based on image pyramid and Bayes rule for reducing noise effects in unsupervised change detection is proposed. By using Gaussian pyramid to process two multitemporal images respectively, two image pyramids are constructed. The difference pyramid images are obtained by point-by-point subtraction between the same level images of the two image pyramids. By resizing all difference pyramid images to the size of the original multitemporal image and then making product operator among them, a map being similar to the difference image is obtained. The difference image is generated by point-by-point subtraction between the two multitemporal images directly. At last, the Bayes rule is used to distinguish the changed pixels. Both synthetic and real data sets are used to evaluate the performance of the proposed technique. Experimental results show that the map from the proposed technique is more robust to noise than the difference image.

  4. ℓ0TV: A new method for image restoration in the presence of impulse noise

    KAUST Repository

    Yuan, Ganzhao

    2015-06-02

    Total Variation (TV) is an effective and popular prior model in the field of regularization-based image processing. This paper focuses on TV for image restoration in the presence of impulse noise. This type of noise frequently arises in data acquisition and transmission due to many reasons, e.g. a faulty sensor or analog-to-digital converter errors. Removing this noise is an important task in image restoration. State-of-the-art methods such as Adaptive Outlier Pursuit(AOP), which is based on TV with L02-norm data fidelity, only give sub-optimal performance. In this paper, we propose a new method, called L0T V -PADMM, which solves the TV-based restoration problem with L0-norm data fidelity. To effectively deal with the resulting non-convex nonsmooth optimization problem, we first reformulate it as an equivalent MPEC (Mathematical Program with Equilibrium Constraints), and then solve it using a proximal Alternating Direction Method of Multipliers (PADMM). Our L0TV-PADMM method finds a desirable solution to the original L0-norm optimization problem and is proven to be convergent under mild conditions. We apply L0TV-PADMM to the problems of image denoising and deblurring in the presence of impulse noise. Our extensive experiments demonstrate that L0TV-PADMM outperforms state-of-the-art image restoration methods.

  5. Imaging resolution signal-to-noise ratio in transverse phase amplification from classical information theory

    International Nuclear Information System (INIS)

    French, Doug; Huang Zun; Pao, H.-Y.; Jovanovic, Igor

    2009-01-01

    A quantum phase amplifier operated in the spatial domain can improve the signal-to-noise ratio in imaging beyond the classical limit. The scaling of the signal-to-noise ratio with the gain of the quantum phase amplifier is derived from classical information theory

  6. Median Filter Noise Reduction of Image and Backpropagation Neural Network Model for Cervical Cancer Classification

    Science.gov (United States)

    Wutsqa, D. U.; Marwah, M.

    2017-06-01

    In this paper, we consider spatial operation median filter to reduce the noise in the cervical images yielded by colposcopy tool. The backpropagation neural network (BPNN) model is applied to the colposcopy images to classify cervical cancer. The classification process requires an image extraction by using a gray level co-occurrence matrix (GLCM) method to obtain image features that are used as inputs of BPNN model. The advantage of noise reduction is evaluated by comparing the performances of BPNN models with and without spatial operation median filter. The experimental result shows that the spatial operation median filter can improve the accuracy of the BPNN model for cervical cancer classification.

  7. PHOTOGRAMMETRIC 3D BUILDING RECONSTRUCTION FROM THERMAL IMAGES

    Directory of Open Access Journals (Sweden)

    E. Maset

    2017-08-01

    Full Text Available This paper addresses the problem of 3D building reconstruction from thermal infrared (TIR images. We show that a commercial Computer Vision software can be used to automatically orient sequences of TIR images taken from an Unmanned Aerial Vehicle (UAV and to generate 3D point clouds, without requiring any GNSS/INS data about position and attitude of the images nor camera calibration parameters. Moreover, we propose a procedure based on Iterative Closest Point (ICP algorithm to create a model that combines high resolution and geometric accuracy of RGB images with the thermal information deriving from TIR images. The process can be carried out entirely by the aforesaid software in a simple and efficient way.

  8. Noise spectroscopy of CoFeB/MgO/CoFeB magnetic tunnel junctions in the presence of thermal gradients

    Energy Technology Data Exchange (ETDEWEB)

    Liebing, N. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, d-38116 Braunschweig (Germany); Serrano-Guisan, S., E-mail: santiago.serrano-guisan@inl.int [International Iberian Nanotechnology Laboratory, Avenida Mestre Jose Veiga, 4715-330 Braga (Portugal); Rott, K.; Reiss, G. [University of Bielefeld, Department of Physics, Univesitätesstr. 25, d-33615 Bielefeld (Germany); Schumacher, H.W., E-mail: hans.w.schumacher@ptb.de [Physikalisch-Technische Bundesanstalt, Bundesallee 100, d-38116 Braunschweig (Germany)

    2016-02-15

    We present experimental data of the precessional dynamics of the free layer of CoFeB/MgO/CoFeB based magnetic tunnel junctions (MTJ) in the presence of thermal gradients across the MTJ. The free layer precession is investigated by noise spectroscopy. Thermal gradients of the order of tens of mK/nm across the MTJ are generated by electrical heating. Without applied thermal gradients we find spin transfer torque modified magnetization precession. With increasing thermal gradients we generally observe a decrease of the precession frequency which could be related to an increasing overall free layer temperature. However an asymmetry of the line width behavior for parallel and antiparallel orientation points towards additional effects beyond thermal activation. This could be a hint for the modification of the precessional dynamics in magnetic tunnel junctions by thermal spin torques. - Highlights: • Thermal gradients induced magnetization dynamics on MTJ structures are explored. • Magnetic noise spectroscopy is carried out to study the efficiency of such effects. • A decrease of resonance frequency is observed at both MTJ states for large ∇T. • An asymmetric linewidth behavior is observed for both MTJ states under ∇T. • Additional thermal effects beyond thermal activation must be considered.

  9. Optimized control of X-ray exposure and image noise using a particular multislice CT scanner

    International Nuclear Information System (INIS)

    Yamamoto, Shuji; Suzuki, Masahiro; Kakinuma, Ryutaro; Moriyama, Noriyuki; Koyama, Yoshihiro; Nagasawa, Hirofumi

    2008-01-01

    Patient dose reduction in computed tomography (CT) always results in a trade off between radiation exposure and image quality. There are few reports that estimate the relationship between image quality and X-ray exposure in CT examinations as one optimal index. The purpose of this study was to determine the optimal parameter settings enabling a low radiation exposure without compromising image quality using a particular 4-row multislice CT (MSCT) scanner (Aquilion VZ 4-slice CT scanner, Toshiba Medical Systems Corporation, Otawara, Tochigi, Japan). Normalized dose divided by image noise for helical pitches (nDNR: normalized dose to noise ratio) were calculated in consideration of beam collimation and tube current-time product. Optimal tube current-time product was calculated using the nDNR for the helical pitches based on user-defined standards of quality of the CT image. As a result, the nDNR proved to be well-supported to decrease the patient exposure in various exposure conditions of MSCT scans; however, the dose and image noise did not show a linear relation to the helical pitch. In conclusion, nDNR can be applied to patient dose reduction while keeping an acceptable image quality using a particular 4-row MSCT scanner. (author)

  10. Non-Stationary Rician Noise Estimation in Parallel MRI Using a Single Image: A Variance-Stabilizing Approach.

    Science.gov (United States)

    Pieciak, Tomasz; Aja-Fernandez, Santiago; Vegas-Sanchez-Ferrero, Gonzalo

    2017-10-01

    Parallel magnetic resonance imaging (pMRI) techniques have gained a great importance both in research and clinical communities recently since they considerably accelerate the image acquisition process. However, the image reconstruction algorithms needed to correct the subsampling artifacts affect the nature of noise, i.e., it becomes non-stationary. Some methods have been proposed in the literature dealing with the non-stationary noise in pMRI. However, their performance depends on information not usually available such as multiple acquisitions, receiver noise matrices, sensitivity coil profiles, reconstruction coefficients, or even biophysical models of the data. Besides, some methods show an undesirable granular pattern on the estimates as a side effect of local estimation. Finally, some methods make strong assumptions that just hold in the case of high signal-to-noise ratio (SNR), which limits their usability in real scenarios. We propose a new automatic noise estimation technique for non-stationary Rician noise that overcomes the aforementioned drawbacks. Its effectiveness is due to the derivation of a variance-stabilizing transformation designed to deal with any SNR. The method was compared to the main state-of-the-art methods in synthetic and real scenarios. Numerical results confirm the robustness of the method and its better performance for the whole range of SNRs.

  11. Thermal noise engines

    OpenAIRE

    Kish, Laszlo B.

    2010-01-01

    Electrical heat engines driven by the Johnson-Nyquist noise of resistors are introduced. They utilize Coulomb's law and the fluctuation-dissipation theorem of statistical physics that is the reverse phenomenon of heat dissipation in a resistor. No steams, gases, liquids, photons, combustion, phase transition, or exhaust/pollution are present here. In these engines, instead of heat reservoirs, cylinders, pistons and valves, resistors, capacitors and switches are the building elements. For the ...

  12. THERMAL AND VISIBLE SATELLITE IMAGE FUSION USING WAVELET IN REMOTE SENSING AND SATELLITE IMAGE PROCESSING

    Directory of Open Access Journals (Sweden)

    A. H. Ahrari

    2017-09-01

    Full Text Available Multimodal remote sensing approach is based on merging different data in different portions of electromagnetic radiation that improves the accuracy in satellite image processing and interpretations. Remote Sensing Visible and thermal infrared bands independently contain valuable spatial and spectral information. Visible bands make enough information spatially and thermal makes more different radiometric and spectral information than visible. However low spatial resolution is the most important limitation in thermal infrared bands. Using satellite image fusion, it is possible to merge them as a single thermal image that contains high spectral and spatial information at the same time. The aim of this study is a performance assessment of thermal and visible image fusion quantitatively and qualitatively with wavelet transform and different filters. In this research, wavelet algorithm (Haar and different decomposition filters (mean.linear,ma,min and rand for thermal and panchromatic bands of Landast8 Satellite were applied as shortwave and longwave fusion method . Finally, quality assessment has been done with quantitative and qualitative approaches. Quantitative parameters such as Entropy, Standard Deviation, Cross Correlation, Q Factor and Mutual Information were used. For thermal and visible image fusion accuracy assessment, all parameters (quantitative and qualitative must be analysed with respect to each other. Among all relevant statistical factors, correlation has the most meaningful result and similarity to the qualitative assessment. Results showed that mean and linear filters make better fused images against the other filters in Haar algorithm. Linear and mean filters have same performance and there is not any difference between their qualitative and quantitative results.

  13. Noise analysis of a digital radiography system

    International Nuclear Information System (INIS)

    Arnold, B.A.; Scheibe, P.O.

    1984-01-01

    The sources of noise in a digital video subtraction angiography system were identified and analyzed. Signal-to-noise ratios of digital radiography systems were measured using the digital image data recorded in the computer. The major sources of noise include quantum noise, TV camera electronic noise, quantization noise from the analog-to-digital converter, time jitter, structure noise in the image intensifier, and video recorder electronic noise. A new noise source was identified, which results from the interplay of fixed pattern noise and the lack of image registration. This type of noise may result from image-intensifier structure noise in combination with TV camera time jitter or recorder time jitter. A similar noise source is generated from the interplay of patient absorption inhomogeneities and patient motion or image re-registration. Signal-to-noise ratios were measured for a variety of experimental conditions using subtracted digital images. Image-intensifier structure noise was shown to be a dominant noise source in unsubtracted images at medium to high radiation exposure levels. A total-system signal-to-noise ratio (SNR) of 750:1 was measured for an input exposure of 1 mR/frame at the image intensifier input. The effect of scattered radiation on subtracted image SNR was found to be greater than previously reported. The detail SNR was found to vary approximately as one plus the scatter degradation factor. Quantization error noise with 8-bit image processors (signal-to-noise ratio of 890:1) was shown to be of increased importance after recent improvements in TV cameras. The results of the analysis are useful both in the design of future digital radiography systems and the selection of optimum clinical techniques

  14. Examination of statistical noise in SPECT image and sampling pitch

    International Nuclear Information System (INIS)

    Takaki, Akihiro; Soma, Tsutomu; Murase, Kenya; Watanabe, Hiroyuki; Murakami, Tomonori; Kawakami, Kazunori; Teraoka, Satomi; Kojima, Akihiro; Matsumoto, Masanori

    2008-01-01

    Statistical noise in single photon emission computed tomography (SPECT) image was examined for its relation with total count and with sampling pitch by simulation and phantom experiment to obtain their projection data under defined conditions. The former SPECT simulation was performed on assumption of a virtual, homogeneous water column (20 cm diameter) as an absorbing mass. In the latter, used were 3D-Hoffman brain phantom (Data Spectrum Corp.) filled with 370 MBq of 99m Tc-pertechnetate solution and a facing 2-detector SPECT machine with a low-energy/high-resolution collimator, E-CAM (Siemens). Projected data by the two methods were reconstructed through the filtered back projection to make each transaxial image. The noise was evaluated by vision, by their root mean square uncertainty calculated from average count and standard deviation (SD) in the region of interest (ROI) defined in reconstructed images and by normalized mean squares calculated from the difference between the reference image obtained with common sampling pitch to and all of obtained slices of, the simulation and phantom. As a conclusion, the pitch was recommended to be set in the machine as to approximating the value calculated by the sampling theorem, though the projection counts per one angular direction were smaller with the same total time of data acquisition. (R.T.)

  15. Acoustic noise reduction in T 1- and proton-density-weighted turbo spin-echo imaging.

    Science.gov (United States)

    Ott, Martin; Blaimer, Martin; Breuer, Felix; Grodzki, David; Heismann, Björn; Jakob, Peter

    2016-02-01

    To reduce acoustic noise levels in T 1-weighted and proton-density-weighted turbo spin-echo (TSE) sequences, which typically reach acoustic noise levels up to 100 dB(A) in clinical practice. Five acoustic noise reduction strategies were combined: (1) gradient ramps and shapes were changed from trapezoidal to triangular, (2) variable-encoding-time imaging was implemented to relax the phase-encoding gradient timing, (3) RF pulses were adapted to avoid the need for reversing the polarity of the slice-rewinding gradient, (4) readout bandwidth was increased to provide more time for gradient activity on other axes, (5) the number of slices per TR was reduced to limit the total gradient activity per unit time. We evaluated the influence of each measure on the acoustic noise level, and conducted in vivo measurements on a healthy volunteer. Sound recordings were taken for comparison. An overall acoustic noise reduction of up to 16.8 dB(A) was obtained by the proposed strategies (1-4) and the acquisition of half the number of slices per TR only. Image quality in terms of SNR and CNR was found to be preserved. The proposed measures in this study allowed a threefold reduction in the acoustic perception of T 1-weighted and proton-density-weighted TSE sequences compared to a standard TSE-acquisition. This could be achieved without visible degradation of image quality, showing the potential to improve patient comfort and scan acceptability.

  16. Image reconstruction with shift-variant filtration and its implication for noise and resolution properties in fan-beam computed tomography

    International Nuclear Information System (INIS)

    Pan Xiaochuan; Yu Lifeng

    2003-01-01

    In computed tomography (CT), the fan-beam filtered backprojection (FFBP) algorithm is used widely for image reconstruction. It is known that the FFBP algorithm can significantly amplify data noise and aliasing artifacts in situations where the focal lengths are comparable to or smaller than the size of the field of measurement (FOM). In this work, we propose an algorithm that is less susceptible to data noise, aliasing, and other data inconsistencies than is the FFBP algorithm while retaining the favorable resolution properties of the FFBP algorithm. In an attempt to evaluate the noise properties in reconstructed images, we derive analytic expressions for image variances obtained by use of the FFBP algorithm and the proposed algorithm. Computer simulation studies are conducted for quantitative evaluation of the spatial resolution and noise properties of images reconstructed by use of the algorithms. Numerical results of these studies confirm the favorable spatial resolution and noise properties of the proposed algorithm and verify the validity of the theoretically predicted image variances. The proposed algorithm and the derived analytic expressions for image variances can have practical implications for both estimation and detection/classification tasks making use of CT images, and they can readily be generalized to other fan-beam geometries

  17. Thermal error analysis and compensation for digital image/volume correlation

    Science.gov (United States)

    Pan, Bing

    2018-02-01

    Digital image/volume correlation (DIC/DVC) rely on the digital images acquired by digital cameras and x-ray CT scanners to extract the motion and deformation of test samples. Regrettably, these imaging devices are unstable optical systems, whose imaging geometry may undergo unavoidable slight and continual changes due to self-heating effect or ambient temperature variations. Changes in imaging geometry lead to both shift and expansion in the recorded 2D or 3D images, and finally manifest as systematic displacement and strain errors in DIC/DVC measurements. Since measurement accuracy is always the most important requirement in various experimental mechanics applications, these thermal-induced errors (referred to as thermal errors) should be given serious consideration in order to achieve high accuracy, reproducible DIC/DVC measurements. In this work, theoretical analyses are first given to understand the origin of thermal errors. Then real experiments are conducted to quantify thermal errors. Three solutions are suggested to mitigate or correct thermal errors. Among these solutions, a reference sample compensation approach is highly recommended because of its easy implementation, high accuracy and in-situ error correction capability. Most of the work has appeared in our previously published papers, thus its originality is not claimed. Instead, this paper aims to give a comprehensive overview and more insights of our work on thermal error analysis and compensation for DIC/DVC measurements.

  18. Variational approach for restoring blurred images with cauchy noise

    DEFF Research Database (Denmark)

    Sciacchitano, Federica; Dong, Yiqiu; Zeng, Tieyong

    2015-01-01

    model, we add a quadratic penalty term, which guarantees the uniqueness of the solution. Due to the convexity of our model, the primal dual algorithm is employed to solve the minimization problem. Experimental results show the effectiveness of the proposed method for simultaneously deblurring...... and denoising images corrupted by Cauchy noise. Comparison with other existing and well-known methods is provided as well....

  19. Ground-based thermal imaging of stream surface temperatures: Technique and evaluation

    Science.gov (United States)

    Bonar, Scott A.; Petre, Sally J.

    2015-01-01

    We evaluated a ground-based handheld thermal imaging system for measuring water temperatures using data from eight southwestern USA streams and rivers. We found handheld thermal imagers could provide considerably more spatial information on water temperature (for our unit one image = 19,600 individual temperature measurements) than traditional methods could supply without a prohibitive amount of effort. Furthermore, they could provide measurements of stream surface temperature almost instantaneously compared with most traditional handheld thermometers (e.g., >20 s/reading). Spatial temperature analysis is important for measurement of subtle temperature differences across waterways, and identification of warm and cold groundwater inputs. Handheld thermal imaging is less expensive and equipment intensive than airborne thermal imaging methods and is useful under riparian canopies. Disadvantages of handheld thermal imagers include their current higher expense than thermometers, their susceptibility to interference when used incorrectly, and their slightly lower accuracy than traditional temperature measurement methods. Thermal imagers can only measure surface temperature, but this usually corresponds to subsurface temperatures in well-mixed streams and rivers. Using thermal imaging in select applications, such as where spatial investigations of water temperature are needed, or in conjunction with stationary temperature data loggers or handheld electronic or liquid-in-glass thermometers to characterize stream temperatures by both time and space, could provide valuable information on stream temperature dynamics. These tools will become increasingly important to fisheries biologists as costs continue to decline.

  20. Fully Convolutional Architecture for Low-Dose CT Image Noise Reduction

    Science.gov (United States)

    Badretale, S.; Shaker, F.; Babyn, P.; Alirezaie, J.

    2017-10-01

    One of the critical topics in medical low-dose Computed Tomography (CT) imaging is how best to maintain image quality. As the quality of images decreases with lowering the X-ray radiation dose, improving image quality is extremely important and challenging. We have proposed a novel approach to denoise low-dose CT images. Our algorithm learns directly from an end-to-end mapping from the low-dose Computed Tomography images for denoising the normal-dose CT images. Our method is based on a deep convolutional neural network with rectified linear units. By learning various low-level to high-level features from a low-dose image the proposed algorithm is capable of creating a high-quality denoised image. We demonstrate the superiority of our technique by comparing the results with two other state-of-the-art methods in terms of the peak signal to noise ratio, root mean square error, and a structural similarity index.

  1. Some selected quantitative methods of thermal image analysis in Matlab.

    Science.gov (United States)

    Koprowski, Robert

    2016-05-01

    The paper presents a new algorithm based on some selected automatic quantitative methods for analysing thermal images. It shows the practical implementation of these image analysis methods in Matlab. It enables to perform fully automated and reproducible measurements of selected parameters in thermal images. The paper also shows two examples of the use of the proposed image analysis methods for the area of ​​the skin of a human foot and face. The full source code of the developed application is also provided as an attachment. The main window of the program during dynamic analysis of the foot thermal image. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Image noise reduction technology reduces radiation in a radial-first cardiac catheterization laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Gunja, Ateka; Pandey, Yagya [Department of Veterans Affairs, Jesse Brown VA Medical Center, Chicago, IL (United States); Division of Cardiology, Department of Medicine, University of Illinois at Chicago, Chicago, IL (United States); Xie, Hui [Division of Epidemiology and Biostatistics, University of Illinois at Chicago, Chicago, IL (United States); Faculty of Health Sciences, Simon Fraser University, Burnaby, BC (Canada); Wolska, Beata M. [Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL (United States); Shroff, Adhir R.; Ardati, Amer K. [Department of Veterans Affairs, Jesse Brown VA Medical Center, Chicago, IL (United States); Division of Cardiology, Department of Medicine, University of Illinois at Chicago, Chicago, IL (United States); Vidovich, Mladen I., E-mail: miv@uic.edu [Department of Veterans Affairs, Jesse Brown VA Medical Center, Chicago, IL (United States); Division of Cardiology, Department of Medicine, University of Illinois at Chicago, Chicago, IL (United States)

    2017-04-15

    Background: Transradial coronary angiography (TRA) has been associated with increased radiation doses. We hypothesized that contemporary image noise reduction technology would reduce radiation doses in the cardiac catheterization laboratory in a typical clinical setting. Methods and results: We performed a single-center, retrospective analysis of 400 consecutive patients who underwent diagnostic and interventional cardiac catheterizations in a predominantly TRA laboratory with traditional fluoroscopy (N = 200) and a new image noise reduction fluoroscopy system (N = 200). The primary endpoint was radiation dose (mGy cm{sup 2}). Secondary endpoints were contrast dose, fluoroscopy times, number of cineangiograms, and radiation dose by operator between the two study periods. Radiation was reduced by 44.7% between the old and new cardiac catheterization laboratory (75.8 mGy cm{sup 2} ± 74.0 vs. 41.9 mGy cm{sup 2} ± 40.7, p < 0.0001). Radiation was reduced for both diagnostic procedures (45.9%, p < 0.0001) and interventional procedures (37.7%, p < 0.0001). There was no statistically significant difference in radiation dose between individual operators (p = 0.84). In multivariate analysis, radiation dose remained significantly decreased with the use of the new system (p < 0.0001) and was associated with weight (p < 0.0001), previous coronary artery bypass grafting (p < 0.0007) and greater than 3 stents used (p < 0.0004). TRA was used in 90% of all cases in both periods. Compared with a transfemoral approach (TFA), TRA was not associated with higher radiation doses (p = 0.20). Conclusions: Image noise reduction technology significantly reduces radiation dose in a contemporary radial-first cardiac catheterization clinical practice. - Highlights: • Radial arterial access has been associated with higher doses compared to femoral access. • In a radial-first cardiac catheterization laboratory (90% radial) we examined radiation doses reduction with a contemporary image-noise

  3. Image noise reduction technology reduces radiation in a radial-first cardiac catheterization laboratory

    International Nuclear Information System (INIS)

    Gunja, Ateka; Pandey, Yagya; Xie, Hui; Wolska, Beata M.; Shroff, Adhir R.; Ardati, Amer K.; Vidovich, Mladen I.

    2017-01-01

    Background: Transradial coronary angiography (TRA) has been associated with increased radiation doses. We hypothesized that contemporary image noise reduction technology would reduce radiation doses in the cardiac catheterization laboratory in a typical clinical setting. Methods and results: We performed a single-center, retrospective analysis of 400 consecutive patients who underwent diagnostic and interventional cardiac catheterizations in a predominantly TRA laboratory with traditional fluoroscopy (N = 200) and a new image noise reduction fluoroscopy system (N = 200). The primary endpoint was radiation dose (mGy cm"2). Secondary endpoints were contrast dose, fluoroscopy times, number of cineangiograms, and radiation dose by operator between the two study periods. Radiation was reduced by 44.7% between the old and new cardiac catheterization laboratory (75.8 mGy cm"2 ± 74.0 vs. 41.9 mGy cm"2 ± 40.7, p < 0.0001). Radiation was reduced for both diagnostic procedures (45.9%, p < 0.0001) and interventional procedures (37.7%, p < 0.0001). There was no statistically significant difference in radiation dose between individual operators (p = 0.84). In multivariate analysis, radiation dose remained significantly decreased with the use of the new system (p < 0.0001) and was associated with weight (p < 0.0001), previous coronary artery bypass grafting (p < 0.0007) and greater than 3 stents used (p < 0.0004). TRA was used in 90% of all cases in both periods. Compared with a transfemoral approach (TFA), TRA was not associated with higher radiation doses (p = 0.20). Conclusions: Image noise reduction technology significantly reduces radiation dose in a contemporary radial-first cardiac catheterization clinical practice. - Highlights: • Radial arterial access has been associated with higher doses compared to femoral access. • In a radial-first cardiac catheterization laboratory (90% radial) we examined radiation doses reduction with a contemporary image-noise compared to

  4. A practical exposure-equivalent metric for instrumentation noise in x-ray imaging systems

    International Nuclear Information System (INIS)

    Yadava, G K; Kuhls-Gilcrist, A T; Rudin, S; Patel, V K; Hoffmann, K R; Bednarek, D R

    2008-01-01

    The performance of high-sensitivity x-ray imagers may be limited by additive instrumentation noise rather than by quantum noise when operated at the low exposure rates used in fluoroscopic procedures. The equipment-invasive instrumentation noise measures (in terms of electrons) are generally difficult to make and are potentially not as helpful in clinical practice as would be a direct radiological representation of such noise that may be determined in the field. In this work, we define a clinically relevant representation for instrumentation noise in terms of noise-equivalent detector entrance exposure, termed the instrumentation noise-equivalent exposure (INEE), which can be determined through experimental measurements of noise-variance or signal-to-noise ratio (SNR). The INEE was measured for various detectors, thus demonstrating its usefulness in terms of providing information about the effective operating range of the various detectors. A simulation study is presented to demonstrate the robustness of this metric against post-processing, and its dependence on inherent detector blur. These studies suggest that the INEE may be a practical gauge to determine and compare the range of quantum-limited performance for clinical x-ray detectors of different design, with the implication that detector performance at exposures below the INEE will be instrumentation-noise limited rather than quantum-noise limited

  5. Suppression of fixed pattern noise for infrared image system

    Science.gov (United States)

    Park, Changhan; Han, Jungsoo; Bae, Kyung-Hoon

    2008-04-01

    In this paper, we propose suppression of fixed pattern noise (FPN) and compensation of soft defect for improvement of object tracking in cooled staring infrared focal plane array (IRFPA) imaging system. FPN appears an observable image which applies to non-uniformity compensation (NUC) by temperature. Soft defect appears glittering black and white point by characteristics of non-uniformity for IR detector by time. This problem is very important because it happen serious problem for object tracking as well as degradation for image quality. Signal processing architecture in cooled staring IRFPA imaging system consists of three tables: low, normal, high temperature for reference gain and offset values. Proposed method operates two offset tables for each table. This is method which operates six term of temperature on the whole. Proposed method of soft defect compensation consists of three stages: (1) separates sub-image for an image, (2) decides a motion distribution of object between each sub-image, (3) analyzes for statistical characteristic from each stationary fixed pixel. Based on experimental results, the proposed method shows an improved image which suppresses FPN by change of temperature distribution from an observational image in real-time.

  6. Color image lossy compression based on blind evaluation and prediction of noise characteristics

    Science.gov (United States)

    Ponomarenko, Nikolay N.; Lukin, Vladimir V.; Egiazarian, Karen O.; Lepisto, Leena

    2011-03-01

    The paper deals with JPEG adaptive lossy compression of color images formed by digital cameras. Adaptation to noise characteristics and blur estimated for each given image is carried out. The dominant factor degrading image quality is determined in a blind manner. Characteristics of this dominant factor are then estimated. Finally, a scaling factor that determines quantization steps for default JPEG table is adaptively set (selected). Within this general framework, two possible strategies are considered. A first one presumes blind estimation for an image after all operations in digital image processing chain just before compressing a given raster image. A second strategy is based on prediction of noise and blur parameters from analysis of RAW image under quite general assumptions concerning characteristics parameters of transformations an image will be subject to at further processing stages. The advantages of both strategies are discussed. The first strategy provides more accurate estimation and larger benefit in image compression ratio (CR) compared to super-high quality (SHQ) mode. However, it is more complicated and requires more resources. The second strategy is simpler but less beneficial. The proposed approaches are tested for quite many real life color images acquired by digital cameras and shown to provide more than two time increase of average CR compared to SHQ mode without introducing visible distortions with respect to SHQ compressed images.

  7. Distinguishing the Noise and image structures for detecting the correction term and filtering the noise by using fuzzy rules

    OpenAIRE

    Sridevi.Ravada,; Vani prasanna.Kanakala,; Ramya.Koilada

    2011-01-01

    A fuzzy filter is constructed from a set of fuzzy IF-THEN rules, these fuzzy rules come either from human experts or by matching input-output pairs .in this paper we propose a new fuzzy filter for the noise reduction of images corrupted with additive noise. here in this approach ,initially fuzzy derivatives for all eight directions that is N,E,W,S, NE,NW,SE,SW are calculated using “fuzzy IF-THEN rules “ and membership functions . Further the fuzzy derivative values obtained are used in the fu...

  8. Adaptive non-local means on local principle neighborhood for noise/artifacts reduction in low-dose CT images.

    Science.gov (United States)

    Zhang, Yuanke; Lu, Hongbing; Rong, Junyan; Meng, Jing; Shang, Junliang; Ren, Pinghong; Zhang, Junying

    2017-09-01

    Low-dose CT (LDCT) technique can reduce the x-ray radiation exposure to patients at the cost of degraded images with severe noise and artifacts. Non-local means (NLM) filtering has shown its potential in improving LDCT image quality. However, currently most NLM-based approaches employ a weighted average operation directly on all neighbor pixels with a fixed filtering parameter throughout the NLM filtering process, ignoring the non-stationary noise nature of LDCT images. In this paper, an adaptive NLM filtering scheme on local principle neighborhoods (PC-NLM) is proposed for structure-preserving noise/artifacts reduction in LDCT images. Instead of using neighboring patches directly, in the PC-NLM scheme, the principle component analysis (PCA) is first applied on local neighboring patches of the target patch to decompose the local patches into uncorrelated principle components (PCs), then a NLM filtering is used to regularize each PC of the target patch and finally the regularized components is transformed to get the target patch in image domain. Especially, in the NLM scheme, the filtering parameter is estimated adaptively from local noise level of the neighborhood as well as the signal-to-noise ratio (SNR) of the corresponding PC, which guarantees a "weaker" NLM filtering on PCs with higher SNR and a "stronger" filtering on PCs with lower SNR. The PC-NLM procedure is iteratively performed several times for better removal of the noise and artifacts, and an adaptive iteration strategy is developed to reduce the computational load by determining whether a patch should be processed or not in next round of the PC-NLM filtering. The effectiveness of the presented PC-NLM algorithm is validated by experimental phantom studies and clinical studies. The results show that it can achieve promising gain over some state-of-the-art methods in terms of artifact suppression and structure preservation. With the use of PCA on local neighborhoods to extract principal structural

  9. Clustered DPCM with removing noise spectra for the lossless compression of hyperspectral images

    Science.gov (United States)

    Wu, Jiaji; Xu, Jianglei

    2013-10-01

    The clustered DPCM (C-DPCM) lossless compression method by Jarno et al. for hyperspectral images achieved a good compression effect. It can be divided into three components: clustering, prediction, and coding. In the prediction part, it solves a multiple linear regression model for each of the clusters in every band. Without considering the effect of noise spectra, there is still room for improvement. This paper proposes a C-DPCM method with Removing Noise Spectra (C-DPCM-RNS) for the lossless compression of hyperspectral images. C-DPCM-RNS's prediction part consists of two-times trainings. The prediction coefficients obtained from the first training will be used in the linear predictor to compute all the predicted values and then the difference between original and predicted values in current band of current class. Only the non-noise spectra are used in the second training. The resulting prediction coefficients from the second training will be used for prediction and sent to the decoder. The two-times trainings remove part of the interference of noise spectra, and reaches a better compression effect than other methods based on regression prediction.

  10. Noise Reduction planar bone imaging nuclear medicine with the use of wavelet transform: an assessment of its quality

    International Nuclear Information System (INIS)

    Casas Cardoso, Maria del Carmen; Perez Diaz, Marlen; Casas Cardoso, Gladis; Lorenzo Ginori, Juan; Paz Viera, Juan Enrique; Roque Diaz, Reinaldo; Cardenas Barreras, Julian

    2009-01-01

    Diagnostic imaging of Nuclear Medicine (MN), is highly used in Oncology, as it constitutes a noninvasive technique that allows early detection of tumors and assessment of therapeutic response of patients under treatment. However, particularly planar scintigraphy images, can be prone to problems of detectability of small lesions, because they are contaminated with noise, a phenomenon which is accentuated by the inability to increase the dose of the radiopharmaceutical or time acquisition of images of the patient over 'certain levels'. The aim of this work is to improve the detectability of tumors of bone. We describe an algorithm for random noise reduction using the wavelet transform (TW). The quality of the resulting images are evaluated through quantitative metrics such as Signal to Noise Ratio (SNR), the Mean Square Error (NMSEA) and Structural Similarity Index (SSIM). It also includes a subjective assessment of image quality by expert criteria, using a variant of the methodology FROC (Free-Response ROC). It was found that some of the filters designed in the wavelet domain, significantly improve the quality of planar bone imaging in terms of increased signal to noise ratio without implying notable structural distortions, which facilitates clinical diagnosis. (author)

  11. Thermal and Quantum Mechanical Noise of a Superfluid Gyroscope

    Science.gov (United States)

    Chui, Talso; Penanen, Konstantin

    2004-01-01

    A potential application of a superfluid gyroscope is for real-time measurements of the small variations in the rotational speed of the Earth, the Moon, and Mars. Such rotational jitter, if not measured and corrected for, will be a limiting factor on the resolution potential of a GPS system. This limitation will prevent many automation concepts in navigation, construction, and biomedical examination from being realized. We present the calculation of thermal and quantum-mechanical phase noise across the Josephson junction of a superfluid gyroscope. This allows us to derive the fundamental limits on the performance of a superfluid gyroscope. We show that the fundamental limit on real-time GPS due to rotational jitter can be reduced to well below 1 millimeter/day. Other limitations and their potential mitigation will also be discussed.

  12. Real-time implementation of optimized maximum noise fraction transform for feature extraction of hyperspectral images

    Science.gov (United States)

    Wu, Yuanfeng; Gao, Lianru; Zhang, Bing; Zhao, Haina; Li, Jun

    2014-01-01

    We present a parallel implementation of the optimized maximum noise fraction (G-OMNF) transform algorithm for feature extraction of hyperspectral images on commodity graphics processing units (GPUs). The proposed approach explored the algorithm data-level concurrency and optimized the computing flow. We first defined a three-dimensional grid, in which each thread calculates a sub-block data to easily facilitate the spatial and spectral neighborhood data searches in noise estimation, which is one of the most important steps involved in OMNF. Then, we optimized the processing flow and computed the noise covariance matrix before computing the image covariance matrix to reduce the original hyperspectral image data transmission. These optimization strategies can greatly improve the computing efficiency and can be applied to other feature extraction algorithms. The proposed parallel feature extraction algorithm was implemented on an Nvidia Tesla GPU using the compute unified device architecture and basic linear algebra subroutines library. Through the experiments on several real hyperspectral images, our GPU parallel implementation provides a significant speedup of the algorithm compared with the CPU implementation, especially for highly data parallelizable and arithmetically intensive algorithm parts, such as noise estimation. In order to further evaluate the effectiveness of G-OMNF, we used two different applications: spectral unmixing and classification for evaluation. Considering the sensor scanning rate and the data acquisition time, the proposed parallel implementation met the on-board real-time feature extraction.

  13. Use of local noise power spectrum and wavelet analysis in quantitative image quality assurance for EPIDs

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Soyoung [Department of Radiation Oncology, University Hospitals Case and Medical Center, Cleveland, Ohio 44106 (United States); Yan, Guanghua; Bassett, Philip; Samant, Sanjiv, E-mail: samant@ufl.edu [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida 32608 (United States); Gopal, Arun [Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201 (United States)

    2016-09-15

    Purpose: To investigate the use of local noise power spectrum (NPS) to characterize image noise and wavelet analysis to isolate defective pixels and inter-subpanel flat-fielding artifacts for quantitative quality assurance (QA) of electronic portal imaging devices (EPIDs). Methods: A total of 93 image sets including custom-made bar-pattern images and open exposure images were collected from four iViewGT a-Si EPID systems over three years. Global quantitative metrics such as modulation transform function (MTF), NPS, and detective quantum efficiency (DQE) were computed for each image set. Local NPS was also calculated for individual subpanels by sampling region of interests within each subpanel of the EPID. The 1D NPS, obtained by radially averaging the 2D NPS, was fitted to a power-law function. The r-square value of the linear regression analysis was used as a singular metric to characterize the noise properties of individual subpanels of the EPID. The sensitivity of the local NPS was first compared with the global quantitative metrics using historical image sets. It was then compared with two commonly used commercial QA systems with images collected after applying two different EPID calibration methods (single-level gain and multilevel gain). To detect isolated defective pixels and inter-subpanel flat-fielding artifacts, Haar wavelet transform was applied on the images. Results: Global quantitative metrics including MTF, NPS, and DQE showed little change over the period of data collection. On the contrary, a strong correlation between the local NPS (r-square values) and the variation of the EPID noise condition was observed. The local NPS analysis indicated image quality improvement with the r-square values increased from 0.80 ± 0.03 (before calibration) to 0.85 ± 0.03 (after single-level gain calibration) and to 0.96 ± 0.03 (after multilevel gain calibration), while the commercial QA systems failed to distinguish the image quality improvement between the two

  14. Estimation of Poisson noise in spatial domain

    Science.gov (United States)

    Švihlík, Jan; Fliegel, Karel; Vítek, Stanislav; Kukal, Jaromír.; Krbcová, Zuzana

    2017-09-01

    This paper deals with modeling of astronomical images in the spatial domain. We consider astronomical light images contaminated by the dark current which is modeled by Poisson random process. Dark frame image maps the thermally generated charge of the CCD sensor. In this paper, we solve the problem of an addition of two Poisson random variables. At first, the noise analysis of images obtained from the astronomical camera is performed. It allows estimating parameters of the Poisson probability mass functions in every pixel of the acquired dark frame. Then the resulting distributions of the light image can be found. If the distributions of the light image pixels are identified, then the denoising algorithm can be applied. The performance of the Bayesian approach in the spatial domain is compared with the direct approach based on the method of moments and the dark frame subtraction.

  15. Statistical reconstruction for cone-beam CT with a post-artifact-correction noise model: application to high-quality head imaging

    International Nuclear Information System (INIS)

    Dang, H; Stayman, J W; Sisniega, A; Xu, J; Zbijewski, W; Siewerdsen, J H; Wang, X; Foos, D H; Aygun, N; Koliatsos, V E

    2015-01-01

    Non-contrast CT reliably detects fresh blood in the brain and is the current front-line imaging modality for intracranial hemorrhage such as that occurring in acute traumatic brain injury (contrast ∼40–80 HU, size  >  1 mm). We are developing flat-panel detector (FPD) cone-beam CT (CBCT) to facilitate such diagnosis in a low-cost, mobile platform suitable for point-of-care deployment. Such a system may offer benefits in the ICU, urgent care/concussion clinic, ambulance, and sports and military theatres. However, current FPD-CBCT systems face significant challenges that confound low-contrast, soft-tissue imaging. Artifact correction can overcome major sources of bias in FPD-CBCT but imparts noise amplification in filtered backprojection (FBP). Model-based reconstruction improves soft-tissue image quality compared to FBP by leveraging a high-fidelity forward model and image regularization. In this work, we develop a novel penalized weighted least-squares (PWLS) image reconstruction method with a noise model that includes accurate modeling of the noise characteristics associated with the two dominant artifact corrections (scatter and beam-hardening) in CBCT and utilizes modified weights to compensate for noise amplification imparted by each correction. Experiments included real data acquired on a FPD-CBCT test-bench and an anthropomorphic head phantom emulating intra-parenchymal hemorrhage. The proposed PWLS method demonstrated superior noise-resolution tradeoffs in comparison to FBP and PWLS with conventional weights (viz. at matched 0.50 mm spatial resolution, CNR = 11.9 compared to CNR = 5.6 and CNR = 9.9, respectively) and substantially reduced image noise especially in challenging regions such as skull base. The results support the hypothesis that with high-fidelity artifact correction and statistical reconstruction using an accurate post-artifact-correction noise model, FPD-CBCT can achieve image quality allowing reliable detection of

  16. A TVSCAD approach for image deblurring with impulsive noise

    Science.gov (United States)

    Gu, Guoyong; Jiang, Suhong; Yang, Junfeng

    2017-12-01

    We consider image deblurring problem in the presence of impulsive noise. It is known that total variation (TV) regularization with L1-norm penalized data fitting (TVL1 for short) works reasonably well only when the level of impulsive noise is relatively low. For high level impulsive noise, TVL1 works poorly. The reason is that all data, both corrupted and noise free, are equally penalized in data fitting, leading to insurmountable difficulty in balancing regularization and data fitting. In this paper, we propose to combine TV regularization with nonconvex smoothly clipped absolute deviation (SCAD) penalty for data fitting (TVSCAD for short). Our motivation is simply that data fitting should be enforced only when an observed data is not severely corrupted, while for those data more likely to be severely corrupted, less or even null penalization should be enforced. A difference of convex functions algorithm is adopted to solve the nonconvex TVSCAD model, resulting in solving a sequence of TVL1-equivalent problems, each of which can then be solved efficiently by the alternating direction method of multipliers. Theoretically, we establish global convergence to a critical point of the nonconvex objective function. The R-linear and at-least-sublinear convergence rate results are derived for the cases of anisotropic and isotropic TV, respectively. Numerically, experimental results are given to show that the TVSCAD approach improves those of the TVL1 significantly, especially for cases with high level impulsive noise, and is comparable with the recently proposed iteratively corrected TVL1 method (Bai et al 2016 Inverse Problems 32 085004).

  17. Techniques for Effective Optical Noise Rejection in Amplitude-Modulated Laser Optical Radars for Underwater Three-Dimensional Imaging

    Directory of Open Access Journals (Sweden)

    Francucci M

    2010-01-01

    Full Text Available Amplitude-modulated (AM laser imaging is a promising technology for the production of accurate three-dimensional (3D images of submerged scenes. The main challenge is that radiation scattered off water gives rise to a disturbing signal (optical noise that degrades more and more the quality of 3D images for increasing turbidity. In this paper, we summarize a series of theoretical findings, that provide valuable hints for the development of experimental methods enabling a partial rejection of optical noise in underwater imaging systems. In order to assess the effectiveness of these methods, which range from modulation/demodulation to polarimetry, we carried out a series of experiments by using the laboratory prototype of an AM 3D imager ( = 405 nm for marine archaeology surveys, in course of realization at the ENEA Artificial Vision Laboratory (Frascati, Rome. The obtained results confirm the validity of the proposed methods for optical noise rejection.

  18. Techniques for Effective Optical Noise Rejection in Amplitude-Modulated Laser Optical Radars for Underwater Three-Dimensional Imaging

    Directory of Open Access Journals (Sweden)

    R. Ricci

    2010-01-01

    Full Text Available Amplitude-modulated (AM laser imaging is a promising technology for the production of accurate three-dimensional (3D images of submerged scenes. The main challenge is that radiation scattered off water gives rise to a disturbing signal (optical noise that degrades more and more the quality of 3D images for increasing turbidity. In this paper, we summarize a series of theoretical findings, that provide valuable hints for the development of experimental methods enabling a partial rejection of optical noise in underwater imaging systems. In order to assess the effectiveness of these methods, which range from modulation/demodulation to polarimetry, we carried out a series of experiments by using the laboratory prototype of an AM 3D imager (λ = 405 nm for marine archaeology surveys, in course of realization at the ENEA Artificial Vision Laboratory (Frascati, Rome. The obtained results confirm the validity of the proposed methods for optical noise rejection.

  19. Assessment of uniformity and signal-to-noise ratio in radiological image intensifier TV systems

    International Nuclear Information System (INIS)

    Malone, J.F.; O'Connor, M.K.; Maher, K.P.

    1985-01-01

    A method of measuring the uniformity of radiological Image Intensifier-TV systems is described. Large non-uniformities were observed in the systems tested. A method of estimating the Signal-to-Noise Ratio in such systems is also presented and applied to characterise the effectiveness of the noise reduction techniques used in digital fluoroscopy. (author)

  20. The reduction of image noise and streak artifact in the thoracic inlet during low dose and ultra-low dose thoracic CT

    International Nuclear Information System (INIS)

    Paul, N S; Prezelj, E; Burey, P; Menezes, R J; Blobel, J; Ursani, A; Kashani, H; Siewerdsen, J H

    2010-01-01

    Increased pixel noise and streak artifact reduce CT image quality and limit the potential for radiation dose reduction during CT of the thoracic inlet. We propose to quantify the pixel noise of mediastinal structures in the thoracic inlet, during low-dose (LDCT) and ultralow-dose (uLDCT) thoracic CT, and assess the utility of new software (quantum denoising system and BOOST3D) in addressing these limitations. Twelve patients had LDCT (120 kV, 25 mAs) and uLDCT (120 kV, 10 mAs) images reconstructed initially using standard mediastinal and lung filters followed by the quantum denoising system (QDS) to reduce pixel noise and BOOST3D (B3D) software to correct photon starvation noise as follows: group 1 no QDS, no B3D; group 2 B3D alone; group 3 QDS alone and group 4 both QDS and B3D. Nine regions of interest (ROIs) were replicated on mediastinal anatomy in the thoracic inlet, for each patient resulting in 3456 data points to calculate pixel noise and attenuation. QDS reduced pixel noise by 18.4% (lung images) and 15.8% (mediastinal images) at 25 mAs. B3D reduced pixel noise by ∼8% in the posterior thorax and in combination there was a 35.5% reduction in effective radiation dose (E) for LDCT (1.63-1.05 mSv) in lung images and 32.2% (1.55-1.05 mSv) in mediastinal images. The same combination produced 20.7% reduction (0.53-0.42 mSv) in E for uLDCT, for lung images and 17.3% (0.51-0.42) for mediastinal images. This quantitative analysis of image quality confirms the utility of dedicated processing software in targeting image noise and streak artifact in thoracic LDCT and uLDCT images taken in the thoracic inlet. This processing software potentiates substantial reductions in radiation dose during thoracic LDCT and uLDCT.

  1. Stochastic IMT (Insulator-Metal-Transition Neurons: An Interplay of Thermal and Threshold Noise at Bifurcation

    Directory of Open Access Journals (Sweden)

    Abhinav Parihar

    2018-04-01

    Full Text Available Artificial neural networks can harness stochasticity in multiple ways to enable a vast class of computationally powerful models. Boltzmann machines and other stochastic neural networks have been shown to outperform their deterministic counterparts by allowing dynamical systems to escape local energy minima. Electronic implementation of such stochastic networks is currently limited to addition of algorithmic noise to digital machines which is inherently inefficient; albeit recent efforts to harness physical noise in devices for stochasticity have shown promise. To succeed in fabricating electronic neuromorphic networks we need experimental evidence of devices with measurable and controllable stochasticity which is complemented with the development of reliable statistical models of such observed stochasticity. Current research literature has sparse evidence of the former and a complete lack of the latter. This motivates the current article where we demonstrate a stochastic neuron using an insulator-metal-transition (IMT device, based on electrically induced phase-transition, in series with a tunable resistance. We show that an IMT neuron has dynamics similar to a piecewise linear FitzHugh-Nagumo (FHN neuron and incorporates all characteristics of a spiking neuron in the device phenomena. We experimentally demonstrate spontaneous stochastic spiking along with electrically controllable firing probabilities using Vanadium Dioxide (VO2 based IMT neurons which show a sigmoid-like transfer function. The stochastic spiking is explained by two noise sources - thermal noise and threshold fluctuations, which act as precursors of bifurcation. As such, the IMT neuron is modeled as an Ornstein-Uhlenbeck (OU process with a fluctuating boundary resulting in transfer curves that closely match experiments. The moments of interspike intervals are calculated analytically by extending the first-passage-time (FPT models for Ornstein-Uhlenbeck (OU process to include a

  2. Security surveillance challenges and proven thermal imaging capabilities in real-world applications

    Science.gov (United States)

    Francisco, Glen L.; Roberts, Sharon

    2004-09-01

    Uncooled thermal imaging was first introduced to the public in early 1980's by Raytheon (legacy Texas Instruments Defense Segment Electronics Group) as a solution for military applications. Since the introduction of this technology, Raytheon has remained the leader in this market as well as introduced commercial versions of thermal imaging products specifically designed for security, law enforcement, fire fighting, automotive and industrial uses. Today, low cost thermal imaging for commercial use in security applications is a reality. Organizations of all types have begun to understand the advantages of using thermal imaging as a means to solve common surveillance problems where other popular technologies fall short. Thermal imaging has proven to be a successful solution for common security needs such as: ¸ vision at night where lighting is undesired and 24x7 surveillance is needed ¸ surveillance over waterways, lakes and ports where water and lighting options are impractical ¸ surveillance through challenging weather conditions where other technologies will be challenged by atmospheric particulates ¸ low maintenance requirements due to remote or difficult locations ¸ low cost over life of product Thermal imaging is now a common addition to the integrated security package. Companies are relying on thermal imaging for specific applications where no other technology can perform.

  3. Thermal neutron imaging in an active interrogation environment

    International Nuclear Information System (INIS)

    Vanier, P.E.; Forman, L.; Norman, D.R.

    2009-01-01

    We have developed a thermal-neutron coded-aperture imager that reveals the locations of hydrogenous materials from which thermal neutrons are being emitted. This imaging detector can be combined with an accelerator to form an active interrogation system in which fast neutrons are produced in a heavy metal target by means of excitation by high energy photons. The photo-induced neutrons can be either prompt or delayed, depending on whether neutronemitting fission products are generated. Provided that there are hydrogenous materials close to the target, some of the photo-induced neutrons slow down and emerge from the surface at thermal energies. These neutrons can be used to create images that show the location and shape of the thermalizing materials. Analysis of the temporal response of the neutron flux provides information about delayed neutrons from induced fission if there are fissionable materials in the target. The combination of imaging and time-of-flight discrimination helps to improve the signal-to-background ratio. It is also possible to interrogate the target with neutrons, for example using a D-T generator. In this case, an image can be obtained from hydrogenous material in a target without the presence of heavy metal. In addition, if fissionable material is present in the target, probing with fast neutrons can stimulate delayed neutrons from fission, and the imager can detect and locate the object of interest, using appropriate time gating. Operation of this sensitive detection equipment in the vicinity of an accelerator presents a number of challenges, because the accelerator emits electromagnetic interference as well as stray ionizing radiation, which can mask the signals of interest.

  4. The influence of CT image noise on proton range calculation in radiotherapy planning

    International Nuclear Information System (INIS)

    Chvetsov, Alexei V; Paige, Sandra L

    2010-01-01

    The purpose of this note is to evaluate the relationship between the stochastic errors in CT numbers and the standard deviation of the computed proton beam range in radiotherapy planning. The stochastic voxel-to-voxel variation in CT numbers called 'noise,' may be due to signal registration, processing and numerical image reconstruction technique. Noise in CT images may cause a deviation in the computed proton range from the physical proton range, even assuming that the error due to CT number-stopping power calibration is removed. To obtain the probability density function (PDF) of the computed proton range, we have used the continuing slowing down approximation (CSDA) and the uncorrelated white Gaussian noise along the proton path. The model of white noise was accepted because for the slice-based fan-beam CT scanner; the power-spectrum properties apply only to the axial (x, y) domain and the noise is uncorrelated in the z domain. However, the possible influence of the noise power spectrum on the standard deviation of the range should be investigated in the future. A random number generator was utilized for noise simulation and this procedure was iteratively repeated to obtain convergence of range PDF, which approached a Gaussian distribution. We showed that the standard deviation of the range, σ, increases linearly with the initial proton energy, computational grid size and standard deviation of the voxel values. The 95% confidence interval width of the range PDF, which is defined as 4σ, may reach 0.6 cm for the initial proton energy of 200 MeV, computational grid 0.25 cm and 5% standard deviation of CT voxel values. Our results show that the range uncertainty due to random errors in CT numbers may be significant and comparable to the uncertainties due to calibration of CT numbers. (note)

  5. Image Representation using Consensus Vocabulary and Food Images Classification

    OpenAIRE

    Moltisanti, Marco

    2016-01-01

    Digital images are the result of many physical factors, such as illumination, point of view an thermal noise of the sensor. These elements may be irrelevant for a specific Computer Vision task; for instance, in the object detection task, the viewpoint and the color of the object should not be relevant in order to answer the question "Is the object present in the image?". Nevertheless, an image depends crucially on all such parameters and it is simply not possible to ignore them in analysis. H...

  6. Noise-induced transition in a quantum system

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Pulak Kumar [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Barik, Debashis [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Ray, Deb Shankar [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2005-07-04

    We examine the noise-induced transition in a fluctuating bistable potential of a driven quantum system in thermal equilibrium. Making use of a Wigner canonical thermal distribution for description of the statistical properties of the thermal bath, we explore the generic effects of quantization like vacuum field fluctuation and tunneling in the characteristic stationary probability distribution functions undergoing transition from unimodal to bimodal nature and in signal-to-noise ratio characterizing the cooperative effect among the noise processes and the weak periodic signal.

  7. Noise-induced transition in a quantum system

    International Nuclear Information System (INIS)

    Ghosh, Pulak Kumar; Barik, Debashis; Ray, Deb Shankar

    2005-01-01

    We examine the noise-induced transition in a fluctuating bistable potential of a driven quantum system in thermal equilibrium. Making use of a Wigner canonical thermal distribution for description of the statistical properties of the thermal bath, we explore the generic effects of quantization like vacuum field fluctuation and tunneling in the characteristic stationary probability distribution functions undergoing transition from unimodal to bimodal nature and in signal-to-noise ratio characterizing the cooperative effect among the noise processes and the weak periodic signal

  8. Thermal background noise limitations

    Science.gov (United States)

    Gulkis, S.

    1982-01-01

    Modern detection systems are increasingly limited in sensitivity by the background thermal photons which enter the receiving system. Expressions for the fluctuations of detected thermal radiation are derived. Incoherent and heterodyne detection processes are considered. References to the subject of photon detection statistics are given.

  9. A debugging method of the Quadrotor UAV based on infrared thermal imaging

    Science.gov (United States)

    Cui, Guangjie; Hao, Qian; Yang, Jianguo; Chen, Lizhi; Hu, Hongkang; Zhang, Lijun

    2018-01-01

    High-performance UAV has been popular and in great need in recent years. The paper introduces a new method in debugging Quadrotor UAVs. Based on the infrared thermal technology and heat transfer theory, a UAV is under debugging above a hot-wire grid which is composed of 14 heated nichrome wires. And the air flow propelled by the rotating rotors has an influence on the temperature distribution of the hot-wire grid. An infrared thermal imager below observes the distribution and gets thermal images of the hot-wire grid. With the assistance of mathematic model and some experiments, the paper discusses the relationship between thermal images and the speed of rotors. By means of getting debugged UAVs into test, the standard information and thermal images can be acquired. The paper demonstrates that comparing to the standard thermal images, a UAV being debugging in the same test can draw some critical data directly or after interpolation. The results are shown in the paper and the advantages are discussed.

  10. The use of wavelet filters for reducing noise in posterior fossa Computed Tomography images

    International Nuclear Information System (INIS)

    Pita-Machado, Reinado; Perez-Diaz, Marlen; Lorenzo-Ginori, Juan V.; Bravo-Pino, Rolando

    2014-01-01

    Wavelet transform based de-noising like wavelet shrinkage, gives the good results in CT. This procedure affects very little the spatial resolution. Some applications are reconstruction methods, while others are a posteriori de-noising methods. De-noising after reconstruction is very difficult because the noise is non-stationary and has unknown distribution. Therefore, methods which work on the sinogram-space don’t have this problem, because they always work over a known noise distribution at this point. On the other hand, the posterior fossa in a head CT is a very complex region for physicians, because it is commonly affected by artifacts and noise which are not eliminated during the reconstruction procedure. This can leads to some false positive evaluations. The purpose of our present work is to compare different wavelet shrinkage de-noising filters to reduce noise, particularly in images of the posterior fossa within CT scans in the sinogram-space. This work describes an experimental search for the best wavelets, to reduce Poisson noise in Computed Tomography (CT) scans. Results showed that de-noising with wavelet filters improved the quality of posterior fossa region in terms of an increased CNR, without noticeable structural distortions

  11. Pulsed laser manipulation of an optically trapped bead: Averaging thermal noise and measuring the pulsed force amplitude

    DEFF Research Database (Denmark)

    Lindballe, Thue Bjerring; Kristensen, Martin V. G.; Keiding, Søren Rud

    2013-01-01

    An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 polystyrene bead, the laser pulse-bead...... interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead...... is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our...

  12. Interferometric Imaging of Geostationary Satellites: Signal-to-Noise Considerations

    Science.gov (United States)

    Jorgensen, A.; Schmitt, H.; Mozurkewich, D.; Armstrong, J.; Restaino, S.; Hindsley, R.

    2011-09-01

    Geostationary satellites are generally too small to image at high resolution with conventional single-dish telescopes. Obtaining many resolution elements across a typical geostationary satellite body requires a single-dish telescope with a diameter of 10’s of m or more, with a good adaptive optics system. An alternative is to use an optical/infrared interferometer consisting of multiple smaller telescopes in an array configuration. In this paper and companion papers1, 2 we discuss the performance of a common-mount 30-element interferometer. The instrument design is presented by Mozurkewich et al.,1 and imaging performance is presented by Schmitt et al.2 In this paper we discuss signal-to-noise ratio for both fringe-tracking and imaging. We conclude that the common-mount interferometer is sufficiently sensitive to track fringes on the majority of geostationary satellites. We also find that high-fidelity images can be obtained after a short integration time of a few minutes to a few tens of minutes.

  13. Pediatric cT: Implementation of ASIR for Substantial Radiation Dose Reduction While Maintaining Pre-ASIR Image Noise1

    Science.gov (United States)

    Brady, Samuel L.; Moore, Bria M.; Yee, Brian S.; Kaufman, Robert A.

    2015-01-01

    Purpose To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient. Materials and Methods The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current–modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests. Results With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT. Conclusion Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose

  14. Zero Thermal Noise in Resistors at Zero Temperature

    Science.gov (United States)

    Kish, Laszlo B.; Niklasson, Gunnar A.; Granqvist, Claes-Göran

    2016-06-01

    The bandwidth of transistors in logic devices approaches the quantum limit, where Johnson noise and associated error rates are supposed to be strongly enhanced. However, the related theory — asserting a temperature-independent quantum zero-point (ZP) contribution to Johnson noise, which dominates the quantum regime — is controversial and resolution of the controversy is essential to determine the real error rate and fundamental energy dissipation limits of logic gates in the quantum limit. The Callen-Welton formula (fluctuation-dissipation theorem) of voltage and current noise for a resistance is the sum of Nyquist’s classical Johnson noise equation and a quantum ZP term with a power density spectrum proportional to frequency and independent of temperature. The classical Johnson-Nyquist formula vanishes at the approach of zero temperature, but the quantum ZP term still predicts non-zero noise voltage and current. Here, we show that this noise cannot be reconciled with the Fermi-Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics. Consequently, Johnson noise must be nil at zero temperature, and non-zero noise found for certain experimental arrangements may be a measurement artifact, such as the one mentioned in Kleen’s uncertainty relation argument.

  15. Status of thermal imaging technology as applied to conservation-update 1

    Energy Technology Data Exchange (ETDEWEB)

    Snow, F.J.; Wood, J.T.; Barthle, R.C.

    1980-07-01

    This document updates the 1978 report on the status of thermal imaging technology as applied to energy conservation in buildings. Thermal imaging technology is discussed in terms of airborne surveys, ground survey programs, and application needs such as standards development and lower cost equipment. Information on the various thermal imaging devices was obtained from manufacturer's standard product literature. Listings are provided of infrared projects of the DOE building diagnostics program, of aerial thermographic firms, and of aerial survey programs. (LCL)

  16. A novel algorithm for thermal image encryption.

    Science.gov (United States)

    Hussain, Iqtadar; Anees, Amir; Algarni, Abdulmohsen

    2018-04-16

    Thermal images play a vital character at nuclear plants, Power stations, Forensic labs biological research, and petroleum products extraction. Safety of thermal images is very important. Image data has some unique features such as intensity, contrast, homogeneity, entropy and correlation among pixels that is why somehow image encryption is trickier as compare to other encryptions. With conventional image encryption schemes it is normally hard to handle these features. Therefore, cryptographers have paid attention to some attractive properties of the chaotic maps such as randomness and sensitivity to build up novel cryptosystems. That is why, recently proposed image encryption techniques progressively more depends on the application of chaotic maps. This paper proposed an image encryption algorithm based on Chebyshev chaotic map and S8 Symmetric group of permutation based substitution boxes. Primarily, parameters of chaotic Chebyshev map are chosen as a secret key to mystify the primary image. Then, the plaintext image is encrypted by the method generated from the substitution boxes and Chebyshev map. By this process, we can get a cipher text image that is perfectly twisted and dispersed. The outcomes of renowned experiments, key sensitivity tests and statistical analysis confirm that the proposed algorithm offers a safe and efficient approach for real-time image encryption.

  17. Use of a thermal imager for snow pit temperatures

    Directory of Open Access Journals (Sweden)

    C. Shea

    2012-03-01

    Full Text Available Weak snow of interest to avalanche forecasting often forms and changes as thin layers. Thermometers, the current field technology for measuring the temperature gradients across such layers – and for thus estimating the expected vapour flux and future type of crystal metamorphism – are difficult to use at distances shorter than 1 cm. In contrast, a thermal imager can provide thousands of simultaneous temperature measurements across small distances with better accuracy. However, a thermal imager only senses the exposed surface, complicating its methods for access and accuracy of buried temperatures. This paper presents methods for exposing buried layers on pit walls and using a thermal imager to measure temperatures on these walls, correct for lens effects with snow, adjust temperature gradients, adjust time exposed, and calculate temperature gradients over millimetre distances. We find lens error on temperature gradients to be on the order of 0.03 °C between image centre and corners. We find temperature gradient change over time to usually decrease – as expected with atmospheric equalization as a strong effect. Case studies including thermal images and visual macro photographs of crystals, collected during the 2010–2011 winter, demonstrate large temperature differences over millimetre-scale distances that are consistent with observed kinetic metamorphism. Further study is needed to use absolute temperatures independently of supporting gradient data.

  18. Image processing techniques for thermal, x-rays and nuclear radiations

    International Nuclear Information System (INIS)

    Chadda, V.K.

    1998-01-01

    The paper describes image acquisition techniques for the non-visible range of electromagnetic spectrum especially thermal, x-rays and nuclear radiations. Thermal imaging systems are valuable tools used for applications ranging from PCB inspection, hot spot studies, fire identification, satellite imaging to defense applications. Penetrating radiations like x-rays and gamma rays are used in NDT, baggage inspection, CAT scan, cardiology, radiography, nuclear medicine etc. Neutron radiography compliments conventional x-rays and gamma radiography. For these applications, image processing and computed tomography are employed for 2-D and 3-D image interpretation respectively. The paper also covers main features of image processing systems for quantitative evaluation of gray level and binary images. (author)

  19. Measurements of the Young's modulus of hydroxide catalysis bonds, and the effect on thermal noise in ground-based gravitational wave detectors

    Science.gov (United States)

    Phelps, Margot; van Veggel, Anna-Maria; Hough, James; Messenger, Chris; Hughes, David; Cunningham, William; Haughian, Karen; Rowan, Sheila

    2018-05-01

    With the outstanding results from the detection and observation of gravitational waves from coalescing black holes and neutron star inspirals, it is essential that pathways to further improve the sensitivities of the LIGO and VIRGO detectors are explored. There are a number of factors that potentially limit the sensitivities of the detectors. One such factor is thermal noise, a component of which results from the mechanical loss in the bond material between the silica fibre suspensions and the test mass mirrors. To calculate its magnitude, the Young's modulus of the bond material has to be known with reasonable accuracy. In this paper we present a new combination of ultrasonic technology and Bayesian analysis to measure the Young's modulus of hydroxide catalysis bonds between fused silica substrates. Using this novel technique, we measure the bond Young's modulus to be 18.5 ±2.32.0 GPa . We show that by applying this value to thermal noise models of bonded test masses with suitable attachment geometries, a reduction in suspension thermal noise consistent with an overall design sensitivity improvement allows a factor of 5 increase in event rate to be achieved.

  20. Free Energy Adjusted Peak Signal to Noise Ratio (FEA-PSNR) for Image Quality Assessment

    Science.gov (United States)

    Liu, Ning; Zhai, Guangtao

    2017-12-01

    Peak signal to noise ratio (PSNR), the de facto universal image quality metric has been widely criticized as having poor correlation with human subjective quality ratings. In this paper, it will be illustrated that the low performance of PSNR as an image quality metric is partially due to its inability of differentiating image contents. And it is revealed that the deviation between subjective score and PSNR for each type of distortions can be systematically captured by perceptual complexity of the target image. The free energy modelling technique is then introduced to simulate the human cognitive process and measure perceptual complexity of an image. Then it is shown that performance of PSNR can be effectively improved using a linear score mapping process considering image free energy and distortion type. The proposed free energy adjusted peak signal to noise ratio (FEA-PSNR) does not change computational steps the of ordinary PSNR and therefore it inherits the merits of being simple, derivable and physically meaningful. So FEA-PSNR can be easily integrated into existing PSNR based image processing systems to achieve more visually plausible results. And the proposed analysis approach can be extended to other types of image quality metrics for enhanced performance.

  1. Reconstructing Face Image from the Thermal Infrared Spectrum to the Visible Spectrum

    Directory of Open Access Journals (Sweden)

    Brahmastro Kresnaraman

    2016-04-01

    Full Text Available During the night or in poorly lit areas, thermal cameras are a better choice instead of normal cameras for security surveillance because they do not rely on illumination. A thermal camera is able to detect a person within its view, but identification from only thermal information is not an easy task. The purpose of this paper is to reconstruct the face image of a person from the thermal spectrum to the visible spectrum. After the reconstruction, further image processing can be employed, including identification/recognition. Concretely, we propose a two-step thermal-to-visible-spectrum reconstruction method based on Canonical Correlation Analysis (CCA. The reconstruction is done by utilizing the relationship between images in both thermal infrared and visible spectra obtained by CCA. The whole image is processed in the first step while the second step processes patches in an image. Results show that the proposed method gives satisfying results with the two-step approach and outperforms comparative methods in both quality and recognition evaluations.

  2. Reducing Radiation Dose in Coronary Angiography and Angioplasty Using Image Noise Reduction Technology.

    Science.gov (United States)

    Kastrati, Mirlind; Langenbrink, Lukas; Piatkowski, Michal; Michaelsen, Jochen; Reimann, Doris; Hoffmann, Rainer

    2016-08-01

    This study sought to quantitatively evaluate the reduction of radiation dose in coronary angiography and angioplasty with the use of image noise reduction technology in a routine clinical setting. Radiation dose data from consecutive 605 coronary procedures (397 consecutive coronary angiograms and 208 consecutive coronary interventions) performed from October 2014 to April 2015 on a coronary angiography system with noise reduction technology (Allura Clarity IQ) were collected. For comparison, radiation dose data from consecutive 695 coronary procedures (435 coronary angiograms and 260 coronary interventions) performed on a conventional coronary angiography system from October 2013 to April 2014 were evaluated. Patient radiation dosage was evaluated based on the cumulative dose area product. Operators and operator practice did not change between the 2 evaluated periods. Patient characteristics were collected to evaluate similarity of patient groups. Image quality was evaluated on a 5-grade scale in 30 patients of each group. There were no significant differences between the 2 evaluated groups in gender, age, weight, and fluoroscopy time (6.8 ± 6.1 vs 6.9 ± 6.3 minutes, not significant). The dose area product was reduced from 3195 ± 2359 to 983 ± 972 cGycm(2) (65%, p technology. Image quality was graded as similar between the evaluated systems (4.0 ± 0.7 vs 4.2 ± 0.6, not significant). In conclusion, a new x-ray technology with image noise reduction algorithm provides a substantial reduction in radiation exposure without the need to prolong the procedure or fluoroscopy time. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Measurement time and statistics for a noise thermometer with a synthetic-noise reference

    Science.gov (United States)

    White, D. R.; Benz, S. P.; Labenski, J. R.; Nam, S. W.; Qu, J. F.; Rogalla, H.; Tew, W. L.

    2008-08-01

    This paper describes methods for reducing the statistical uncertainty in measurements made by noise thermometers using digital cross-correlators and, in particular, for thermometers using pseudo-random noise for the reference signal. First, a discrete-frequency expression for the correlation bandwidth for conventional noise thermometers is derived. It is shown how an alternative frequency-domain computation can be used to eliminate the spectral response of the correlator and increase the correlation bandwidth. The corresponding expressions for the uncertainty in the measurement of pseudo-random noise in the presence of uncorrelated thermal noise are then derived. The measurement uncertainty in this case is less than that for true thermal-noise measurements. For pseudo-random sources generating a frequency comb, an additional small reduction in uncertainty is possible, but at the cost of increasing the thermometer's sensitivity to non-linearity errors. A procedure is described for allocating integration times to further reduce the total uncertainty in temperature measurements. Finally, an important systematic error arising from the calculation of ratios of statistical variables is described.

  4. Influence of sinogram affirmed iterative reconstruction of CT data on image noise characteristics and low-contrast detectability: an objective approach.

    Directory of Open Access Journals (Sweden)

    Christian von Falck

    Full Text Available OBJECTIVES: To utilize a novel objective approach combining a software phantom and an image quality metric to systematically evaluate the influence of sinogram affirmed iterative reconstruction (SAFIRE of multidetector computed tomography (MDCT data on image noise characteristics and low-contrast detectability (LCD. MATERIALS AND METHODS: A low-contrast and a high-contrast phantom were examined on a 128-slice scanner at different dose levels. The datasets were reconstructed using filtered back projection (FBP and SAFIRE and virtual low-contrast lesions (-20HU were inserted. LCD was evaluated using the multiscale structural similarity index (MS-SIM*. Image noise texture and spatial resolution were objectively evaluated. RESULTS: The use of SAFIRE led to an improvement of LCD for all dose levels and lesions sizes. The relative improvement of LCD was inversely related to the dose level, declining from 208%(±37%, 259%(±30% and 309%(±35% at 25mAs to 106%(±6%, 119%(±9% and 123%(±8% at 200mAs for SAFIRE filter strengths of 1, 3 and 5 (p<0.05. SAFIRE reached at least the LCD of FBP at a relative dose of 50%. There was no statistically significant difference in spatial resolution. The use of SAFIRE led to coarser image noise granularity. CONCLUSION: A novel objective approach combining a software phantom and the MS-SSIM* image quality metric was used to analyze the detectability of virtual low-contrast lesions against the background of image noise as created using SAFIRE in comparison to filtered back-projection. We found, that image noise characteristics using SAFIRE at 50% dose were comparable to the use of FBP at 100% dose with respect to lesion detectability. The unfamiliar imaging appearance of iteratively reconstructed datasets may in part be explained by a different, coarser noise characteristic as demonstrated by a granulometric analysis.

  5. Conversion of mammographic images to appear with the noise and sharpness characteristics of a different detector and x-ray system

    Energy Technology Data Exchange (ETDEWEB)

    Mackenzie, Alistair; Dance, David R.; Workman, Adam; Yip, Mary; Wells, Kevin; Young, Kenneth C. [National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford, GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom); Northern Ireland Regional Medical Physics Service, Forster Green Hospital, Belfast, BT8 4HD (United Kingdom); Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom); Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH (United Kingdom); National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford, GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom)

    2012-05-15

    Purpose: Undertaking observer studies to compare imaging technology using clinical radiological images is challenging due to patient variability. To achieve a significant result, a large number of patients would be required to compare cancer detection rates for different image detectors and systems. The aim of this work was to create a methodology where only one set of images is collected on one particular imaging system. These images are then converted to appear as if they had been acquired on a different detector and x-ray system. Therefore, the effect of a wide range of digital detectors on cancer detection or diagnosis can be examined without the need for multiple patient exposures. Methods: Three detectors and x-ray systems [Hologic Selenia (ASE), GE Essential (CSI), Carestream CR (CR)] were characterized in terms of signal transfer properties, noise power spectra (NPS), modulation transfer function, and grid properties. The contributions of the three noise sources (electronic, quantum, and structure noise) to the NPS were calculated by fitting a quadratic polynomial at each spatial frequency of the NPS against air kerma. A methodology was developed to degrade the images to have the characteristics of a different (target) imaging system. The simulated images were created by first linearizing the original images such that the pixel values were equivalent to the air kerma incident at the detector. The linearized image was then blurred to match the sharpness characteristics of the target detector. Noise was then added to the blurred image to correct for differences between the detectors and any required change in dose. The electronic, quantum, and structure noise were added appropriate to the air kerma selected for the simulated image and thus ensuring that the noise in the simulated image had the same magnitude and correlation as the target image. A correction was also made for differences in primary grid transmission, scatter, and veiling glare. The method was

  6. Quantitative subsurface analysis using frequency modulated thermal wave imaging

    Science.gov (United States)

    Subhani, S. K.; Suresh, B.; Ghali, V. S.

    2018-01-01

    Quantitative depth analysis of the anomaly with an enhanced depth resolution is a challenging task towards the estimation of depth of the subsurface anomaly using thermography. Frequency modulated thermal wave imaging introduced earlier provides a complete depth scanning of the object by stimulating it with a suitable band of frequencies and further analyzing the subsequent thermal response using a suitable post processing approach to resolve subsurface details. But conventional Fourier transform based methods used for post processing unscramble the frequencies with a limited frequency resolution and contribute for a finite depth resolution. Spectral zooming provided by chirp z transform facilitates enhanced frequency resolution which can further improves the depth resolution to axially explore finest subsurface features. Quantitative depth analysis with this augmented depth resolution is proposed to provide a closest estimate to the actual depth of subsurface anomaly. This manuscript experimentally validates this enhanced depth resolution using non stationary thermal wave imaging and offers an ever first and unique solution for quantitative depth estimation in frequency modulated thermal wave imaging.

  7. Internal representations for face detection: an application of noise-based image classification to BOLD responses.

    Science.gov (United States)

    Nestor, Adrian; Vettel, Jean M; Tarr, Michael J

    2013-11-01

    What basic visual structures underlie human face detection and how can we extract such structures directly from the amplitude of neural responses elicited by face processing? Here, we address these issues by investigating an extension of noise-based image classification to BOLD responses recorded in high-level visual areas. First, we assess the applicability of this classification method to such data and, second, we explore its results in connection with the neural processing of faces. To this end, we construct luminance templates from white noise fields based on the response of face-selective areas in the human ventral cortex. Using behaviorally and neurally-derived classification images, our results reveal a family of simple but robust image structures subserving face representation and detection. Thus, we confirm the role played by classical face selective regions in face detection and we help clarify the representational basis of this perceptual function. From a theory standpoint, our findings support the idea of simple but highly diagnostic neurally-coded features for face detection. At the same time, from a methodological perspective, our work demonstrates the ability of noise-based image classification in conjunction with fMRI to help uncover the structure of high-level perceptual representations. Copyright © 2012 Wiley Periodicals, Inc.

  8. High level white noise generator

    International Nuclear Information System (INIS)

    Borkowski, C.J.; Blalock, T.V.

    1979-01-01

    A wide band, stable, random noise source with a high and well-defined output power spectral density is provided which may be used for accurate calibration of Johnson Noise Power Thermometers (JNPT) and other applications requiring a stable, wide band, well-defined noise power spectral density. The noise source is based on the fact that the open-circuit thermal noise voltage of a feedback resistor, connecting the output to the input of a special inverting amplifier, is available at the amplifier output from an equivalent low output impedance caused by the feedback mechanism. The noise power spectral density level at the noise source output is equivalent to the density of the open-circuit thermal noise or a 100 ohm resistor at a temperature of approximately 64,000 Kelvins. The noise source has an output power spectral density that is flat to within 0.1% (0.0043 db) in the frequency range of from 1 KHz to 100 KHz which brackets typical passbands of the signal-processing channels of JNPT's. Two embodiments, one of higher accuracy that is suitable for use as a standards instrument and another that is particularly adapted for ambient temperature operation, are illustrated in this application

  9. High level white noise generator

    Science.gov (United States)

    Borkowski, Casimer J.; Blalock, Theron V.

    1979-01-01

    A wide band, stable, random noise source with a high and well-defined output power spectral density is provided which may be used for accurate calibration of Johnson Noise Power Thermometers (JNPT) and other applications requiring a stable, wide band, well-defined noise power spectral density. The noise source is based on the fact that the open-circuit thermal noise voltage of a feedback resistor, connecting the output to the input of a special inverting amplifier, is available at the amplifier output from an equivalent low output impedance caused by the feedback mechanism. The noise power spectral density level at the noise source output is equivalent to the density of the open-circuit thermal noise or a 100 ohm resistor at a temperature of approximately 64,000 Kelvins. The noise source has an output power spectral density that is flat to within 0.1% (0.0043 db) in the frequency range of from 1 KHz to 100 KHz which brackets typical passbands of the signal-processing channels of JNPT's. Two embodiments, one of higher accuracy that is suitable for use as a standards instrument and another that is particularly adapted for ambient temperature operation, are illustrated in this application.

  10. The Impact of Optimal Respiratory Gating and Image Noise on Evaluation of Intratumor Heterogeneity on 18F-FDG PET Imaging of Lung Cancer.

    Science.gov (United States)

    Grootjans, Willem; Tixier, Florent; van der Vos, Charlotte S; Vriens, Dennis; Le Rest, Catherine C; Bussink, Johan; Oyen, Wim J G; de Geus-Oei, Lioe-Fee; Visvikis, Dimitris; Visser, Eric P

    2016-11-01

    Accurate measurement of intratumor heterogeneity using parameters of texture on PET images is essential for precise characterization of cancer lesions. In this study, we investigated the influence of respiratory motion and varying noise levels on quantification of textural parameters in patients with lung cancer. We used an optimal-respiratory-gating algorithm on the list-mode data of 60 lung cancer patients who underwent 18 F-FDG PET. The images were reconstructed using a duty cycle of 35% (percentage of the total acquired PET data). In addition, nongated images of varying statistical quality (using 35% and 100% of the PET data) were reconstructed to investigate the effects of image noise. Several global image-derived indices and textural parameters (entropy, high-intensity emphasis, zone percentage, and dissimilarity) that have been associated with patient outcome were calculated. The clinical impact of optimal respiratory gating and image noise on assessment of intratumor heterogeneity was evaluated using Cox regression models, with overall survival as the outcome measure. The threshold for statistical significance was adjusted for multiple comparisons using Bonferroni correction. In the lower lung lobes, respiratory motion significantly affected quantification of intratumor heterogeneity for all textural parameters (P 0.007). The mean increase in entropy, dissimilarity, zone percentage, and high-intensity emphasis was 1.3% ± 1.5% (P = 0.02), 11.6% ± 11.8% (P = 0.006), 2.3% ± 2.2% (P = 0.002), and 16.8% ± 17.2% (P = 0.006), respectively. No significant differences were observed for lesions in the upper lung lobes (P > 0.007). Differences in the statistical quality of the PET images affected the textural parameters less than respiratory motion, with no significant difference observed. The median follow-up time was 35 mo (range, 7-39 mo). In multivariate analysis for overall survival, total lesion glycolysis and high-intensity emphasis were the two most

  11. Thermal design and performance of the REgolith x-ray imaging spectrometer (REXIS) instrument

    Science.gov (United States)

    Stout, Kevin D.; Masterson, Rebecca A.

    2014-08-01

    The REgolith X-ray Imaging Spectrometer (REXIS) instrument is a student collaboration instrument on the OSIRIS-REx asteroid sample return mission scheduled for launch in September 2016. The REXIS science mission is to characterize the elemental abundances of the asteroid Bennu on a global scale and to search for regions of enhanced elemental abundance. The thermal design of the REXIS instrument is challenging due to both the science requirements and the thermal environment in which it will operate. The REXIS instrument consists of two assemblies: the spectrometer and the solar X-ray monitor (SXM). The spectrometer houses a 2x2 array of back illuminated CCDs that are protected from the radiation environment by a one-time deployable cover and a collimator assembly with coded aperture mask. Cooling the CCDs during operation is the driving thermal design challenge on the spectrometer. The CCDs operate in the vicinity of the electronics box, but a 130 °C thermal gradient is required between the two components to cool the CCDs to -60 °C in order to reduce noise and obtain science data. This large thermal gradient is achieved passively through the use of a copper thermal strap, a large radiator facing deep space, and a two-stage thermal isolation layer between the electronics box and the DAM. The SXM is mechanically mounted to the sun-facing side of the spacecraft separately from the spectrometer and characterizes the highly variable solar X-ray spectrum to properly interpret the data from the asteroid. The driving thermal design challenge on the SXM is cooling the silicon drift detector (SDD) to below -30 °C when operating. A two-stage thermoelectric cooler (TEC) is located directly beneath the detector to provide active cooling, and spacecraft MLI blankets cover all of the SXM except the detector aperture to radiatively decouple the SXM from the flight thermal environment. This paper describes the REXIS thermal system requirements, thermal design, and analyses, with

  12. Regional improvement of signal-to-noise and contrast-to-noise ratios in dual-screen CR chest imaging - a phantom study

    International Nuclear Information System (INIS)

    Liu Xinming; Shaw, Chris C.

    2001-01-01

    The improvement of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in dual-screen computed radiography (CR) has been investigated for various regions in images of an anthropomorphic chest phantom. With the dual-screen CR technique, two image plates are placed in a cassette and exposed together during imaging. The exposed plates are separately scanned to form a front image and a back image, which are then registered and superimposed to form a composite image with improved SNRs and CNRs. The improvement can be optimized by applying specifically selected weighting factors during superimposition. In this study, dual-screen CR images of an anthropomorphic chest phantom were acquired and formed with four different combinations of standard resolution (ST) and high-resolution (HR) screens: ST-ST, ST-HR, HR-ST, and HR-HR. SNRs and their improvements were measured and compared over twelve representative regions-of-interest (ROIs) in these images. A 19.1%-45.7% increase of the SNR was observed, depending on the ROI and screen combination used. The optimal weighting factors were found to vary by only 4.5%-12.4%. Largest improvement was found in the lung field for all screen combinations. Improvement of CNRs was investigated over two ROIs in the lung field using the rib bones as the contrast objects and a 29.2%-43.9% improvement of the CNR was observed. Among the four screen combinations, ST-ST resulted in the most SNR and CNR improvement, followed in order by HR-ST, HR-HR, and ST-HR. The HR-ST combination yielded the lowest spatial variation of the optimal weighting factors with improved SNRs and CNRs close to those of the ST-ST combination

  13. Changes in signal-to-noise ratios and contrast-to-noise ratios of hypervascular hepatocellular carcinomas on ferucarbotran-enhanced dynamic MR imaging

    International Nuclear Information System (INIS)

    Park, Yulri; Choi, Dongil; Kim, Seong Hyun; Kim, Seung Hoon; Kim, Min Ju; Lee, Jongmee; Lim, Jae Hoon; Lee, Won Jae; Lim, Hyo K.

    2006-01-01

    Purpose: To verify changes in the signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of hypervascular hepatocellular carcinomas (HCCs) on ferucarbotran-enhanced dynamic T1-weighted MR imaging. Materials and methods: Fifty-two patients with 61 hypervascular HCCs underwent ferucarbotran-enhanced dynamic MR imaging, and then hepatic resection. Hypervascular HCCs were identified when definite enhancement was noted during the arterial dominant phase of three-phase MDCT. Dynamic MR Images with T1-weighted fast multiplanar spoiled gradient-recalled echo sequence (TR200/TE4.2) were obtained before and 20 s, and 1, 3, 5, and 10 min, after bolus injection of ferucarbotran. We estimated the signal intensities of tumors and livers, and calculated the SNRs and CNRs of the tumors. Results: On ferucarbotran-enhanced dynamic MR imaging, SNR measurements showed a fluctuating pattern, namely, an increase in SNR followed by a decrease and a subsequent increase (or a decrease in SNR followed by a increase and a subsequent decrease) in 50 (82.0%) of 61 tumors, a single-peak SNR pattern (highest SNR on 20 s, 1, 3, or 5 min delayed images followed by a decrease) in seven (11.5%), and a decrease in SNR followed by an increase in four (6.6%). Maximum absolute CNRs with positive value were noted on 10 min delayed images in 41 (67.2%) tumors, and maximum absolute CNRs with negative value were observed on 20 s delayed images in 12 (19.7%) and on 1 min delayed images in eight (13.1%). Conclusion: Despite showing various SNR and CNR changes, the majority of hypervascular HCCs demonstrated a fluctuating SNR pattern on ferucarbotran-enhanced dynamic MR imaging and a highest CNR on 10 min delayed image, which differed from the classic enhancement pattern on multiphasic CT

  14. Thermal Imaging Performance of TIR Onboard the Hayabusa2 Spacecraft

    Science.gov (United States)

    Arai, Takehiko; Nakamura, Tomoki; Tanaka, Satoshi; Demura, Hirohide; Ogawa, Yoshiko; Sakatani, Naoya; Horikawa, Yamato; Senshu, Hiroki; Fukuhara, Tetsuya; Okada, Tatsuaki

    2017-07-01

    The thermal infrared imager (TIR) is a thermal infrared camera onboard the Hayabusa2 spacecraft. TIR will perform thermography of a C-type asteroid, 162173 Ryugu (1999 JU3), and estimate its surface physical properties, such as surface thermal emissivity ɛ , surface roughness, and thermal inertia Γ, through remote in-situ observations in 2018 and 2019. In prelaunch tests of TIR, detector calibrations and evaluations, along with imaging demonstrations, were performed. The present paper introduces the experimental results of a prelaunch test conducted using a large-aperture collimator in conjunction with TIR under atmospheric conditions. A blackbody source, controlled at constant temperature, was measured using TIR in order to construct a calibration curve for obtaining temperatures from observed digital data. As a known thermal emissivity target, a sandblasted black almite plate warmed from the back using a flexible heater was measured by TIR in order to evaluate the accuracy of the calibration curve. As an analog target of a C-type asteroid, carbonaceous chondrites (50 mm × 2 mm in thickness) were also warmed from the back and measured using TIR in order to clarify the imaging performance of TIR. The calibration curve, which was fitted by a specific model of the Planck function, allowed for conversion to the target temperature within an error of 1°C (3σ standard deviation) for the temperature range of 30 to 100°C. The observed temperature of the black almite plate was consistent with the temperature measured using K-type thermocouples, within the accuracy of temperature conversion using the calibration curve when the temperature variation exhibited a random error of 0.3 °C (1σ ) for each pixel at a target temperature of 50°C. TIR can resolve the fine surface structure of meteorites, including cracks and pits with the specified field of view of 0.051°C (328 × 248 pixels). There were spatial distributions with a temperature variation of 3°C at the setting

  15. Online thermal imaging: a simple approach

    Science.gov (United States)

    Senior, Mark; Hollock, Steve; Sandhu, Sat; Coy, Joanne; Parkin, Rob

    2003-04-01

    Continuous monitoring of plant and processes is widely practised but the use of thermal imagers in such systems has always been restricted by camera cost. A radiometric thermal imager can be regarded as equivalent to multiple single point radiometers or a matrix of thermocouples but with the advantages of far denser coverage, non-contact measurement, simpler installation and data processing; in addition several of the advantages of conventional machine vision systems such as shape and position recognition can be provided. IRISYS has developed a multipoint radiometer utilising its low-cost infrared array technology. This unit provides continuous real-time temperature monitoring of 256 data points at an affordable price; it is housed in a small, light-weight, sealed and robust metal case and generates RS232 or Ethernet data output. This paper reviews the radiometer technology and its application to single and multi-camera systems.

  16. Thermal Noise Canceling in LNAs : A Review

    NARCIS (Netherlands)

    Nauta, Bram; Klumperink, Eric A.M.; Bruccoleri, Frederico

    2004-01-01

    Most wide-band amplifiers suffer from a fundamental trade-off between noise figure NF and source impedance matching, which limits NF to values typically above 3dB. Recently, a feed-forward noise canceling technique has been proposed to break this trade-off. This paper reviews the principle of the

  17. Amplifiers Exploiting Thermal Noise Canceling: A Review

    NARCIS (Netherlands)

    Klumperink, Eric A.M.; Bruccoleri, F.; Stroet, P.M.; Stroet, Peter; Nauta, Bram

    2004-01-01

    Wide-band LNAs suffer from a fundamental trade-off between noise figure NF and source impedance matching, which limits NF to values typically above 3dB. Recently, a feed-forward noise canceling technique has been proposed to break this trade-off. This paper reviews the principle of the technique and

  18. Application of optical character recognition in thermal image processing

    Science.gov (United States)

    Chan, W. T.; Sim, K. S.; Tso, C. P.

    2011-07-01

    This paper presents the results of a study on the reliability of the thermal imager compared to other devices that are used in preventive maintenance. Several case studies are used to facilitate the comparisons. When any device is found to perform unsatisfactorily where there is a suspected fault, its short-fall is determined so that the other devices may compensate, if possible. This study discovered that the thermal imager is not suitable or efficient enough for systems that happen to have little contrast in temperature between its parts or small but important parts that have their heat signatures obscured by those from other parts. The thermal imager is also found to be useful for preliminary examinations of certain systems, after which other more economical devices are suitable substitutes for further examinations. The findings of this research will be useful to the design and planning of preventive maintenance routines for industrial benefits.

  19. Paediatric CT: the effects of increasing image noise on pulmonary nodule detection

    International Nuclear Information System (INIS)

    Punwani, Shonit; Davies, Warren; Greenhalgh, Rebecca; Humphries, Paul; Zhang, Jie

    2008-01-01

    A radiation dose of any magnitude can produce a detrimental effect manifesting as an increased risk of cancer. Cancer development may be delayed for many years following radiation exposure. Minimizing radiation dose in children is particularly important. However, reducing the dose can reduce image quality and may, therefore, hinder lesion detection. We investigated the effects of reducing the image signal-to-noise ratio (SNR) on CT lung nodule detection for a range of nodule sizes. A simulated nodule was placed at the periphery of the lung on an axial CT slice using image editing software. Multiple copies of the manipulated image were saved with various levels of superimposed noise. The image creation process was repeated for a range of nodule sizes. For a given nodule size, output images were read independently by four Fellows of The Royal College of Radiologists. The overall sensitivities in detecting nodules for the SNR ranges 0.8-0.99, 1-1.49, and 1.5-2.35 were 40.5%, 77.3% and 90.3%, respectively, and the specificities were 47.9%, 73.3% and 75%, respectively. The sensitivity for detecting lung nodules increased with nodule size and increasing SNR. There was 100% sensitivity for the detection of nodules of 4-10 mm in diameter at SNRs greater than 1.5. Reducing medical radiation doses in children is of paramount importance. For chest CT examinations this may be counterbalanced by reduced sensitivity and specificity combined with an increased uncertainty of pulmonary nodule detection. This study demonstrates that pulmonary nodules of 4 mm and greater in diameter can be detected with 100% sensitivity provided that the perceived image SNR is greater than 1.5. (orig.)

  20. Performance of a fast low noise front-end preamplifier for the MAGIC imaging Cherenkov telescope

    International Nuclear Information System (INIS)

    Blanch, O.; Blanchot, G.; Bosman, M.

    1999-01-01

    The observation of high energy cosmic gamma rays with an energy threshold of 15 GeV using the proposed MAGIC ground based air imaging Cherenkov telescope requires the development of new low noise fast preamplifiers for the camera photosensors. The speed and noise performance of a transimpedance preamplifier that resolves the multi photoelectron peaks from a hybrid photomultiplier with a peaking time below 7 ns is presented. The new front-end circuit is designed with RF low noise bipolar transistors and provides fast output pulses that allow for fast trigger settings

  1. Comparison of contrast-to-noise ratios of transmission and dark-field signal in grating-based X-ray imaging for healthy murine lung tissue

    International Nuclear Information System (INIS)

    Schwab, Felix; Schleede, Simone; Hahn, Dieter

    2013-01-01

    Purpose: An experimental comparison of the contrast-to-noise ratio (CNR) between transmission and dark-field signals in grating-based X-ray imaging for ex-vivo murine lung tissue. Materials and Methods: Lungs from three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Background noise of transmission and dark-field signal was quantified by measuring the standard deviation in a region of interest (ROI) placed in a homogeneous area outside the specimen. Image contrast was quantified by measuring the signal range in rectangular ROIs placed in central and peripheral lung parenchyma. The relative contrast gain (RCG) of dark-field over transmission images was calculated as CNRDF / CNRT. Results: In all images, there was a trend for contrast-to-noise ratios of dark-field images (CNRDF) to be higher than for transmission images (CNRT) for all ROIs (median 61 vs. 38, p = 0.10), but the difference was statistically significant only for peripheral ROIs (61 vs. 32, p = 0.03). Median RCG was >1 for all ROIs (1.84). RCG values were significantly smaller for central ROIs than for peripheral ROIs (1.34 vs. 2.43, p = 0.03). Conclusion: The contrast-to-noise ratio of dark-field images compares more favorably to the contrast-to-noise ratio of transmission images for peripheral lung regions as compared to central regions. For any specific specimen, a calculation of the RCG allows comparing which X-ray modality (dark-field or transmission imaging) produces better contrast-to-noise characteristics in a well-defined ROI. (orig.)

  2. Liquid-phase exfoliated graphene self-assembled films: Low-frequency noise and thermal-electric characterization

    International Nuclear Information System (INIS)

    Tubon Usca, G.; Hernandez-Ambato, J.; Pace, C.; Caputi, L.S.; Tavolaro, A.

    2016-01-01

    Highlights: • Graphene was exfoliated in liquid phase also in the presence of zeolite 4A. • Films were obtained by drop-casting. • SEM, Raman, low-frequency noise and thermal electric measurements show that the presence of zeolite improves the quality of the FLG films. - Abstract: In few years, graphene has become a revolutionary material, leading not only to applications in various fields such as electronics, medicine and environment, but also to the production of new types of 2D materials. In this work, Liquid Phase Exfoliation (LPE) was applied to natural graphite by brief sonication or mixer treatment in suitable solvents, in order to produce Few Layers Graphene (FLG) suspensions. Additionally, zeolite 4A (Z4A) was added during the production of FLG flakes-based inks, with the aim of aiding the exfoliation process. Conductive films were obtained by drop casting three types of suspensions over Al 2 O 3 substrates with interdigitated electrodes, with total channel surface of 1.39 mm 2 . The morphology characterization resulted in the verification of the presence of thin self-assembled flakes. Raman studies gave evidence of 4 to 10 layers graphene flakes. Electrical measurements were performed to state the Low-Frequency Noise and Thermal-Electric characteristics of the samples. We observe interesting relations between sample preparation procedures and electrical properties.

  3. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    Energy Technology Data Exchange (ETDEWEB)

    Tobias, B., E-mail: bjtobias@pppl.gov [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Domier, C. W.; Luhmann, N. C.; Luo, C.; Mamidanna, M.; Phan, T.; Pham, A.-V.; Wang, Y. [University of California at Davis, Davis, California 95616 (United States)

    2016-11-15

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50–150 GHz) to an intermediate frequency (IF) band (e.g. 0.1–18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10× improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). Implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  4. Cat Swarm Optimization Based Functional Link Artificial Neural Network Filter for Gaussian Noise Removal from Computed Tomography Images

    Directory of Open Access Journals (Sweden)

    M. Kumar

    2016-01-01

    Full Text Available Gaussian noise is one of the dominant noises, which degrades the quality of acquired Computed Tomography (CT image data. It creates difficulties in pathological identification or diagnosis of any disease. Gaussian noise elimination is desirable to improve the clarity of a CT image for clinical, diagnostic, and postprocessing applications. This paper proposes an evolutionary nonlinear adaptive filter approach, using Cat Swarm Functional Link Artificial Neural Network (CS-FLANN to remove the unwanted noise. The structure of the proposed filter is based on the Functional Link Artificial Neural Network (FLANN and the Cat Swarm Optimization (CSO is utilized for the selection of optimum weight of the neural network filter. The applied filter has been compared with the existing linear filters, like the mean filter and the adaptive Wiener filter. The performance indices, such as peak signal to noise ratio (PSNR, have been computed for the quantitative analysis of the proposed filter. The experimental evaluation established the superiority of the proposed filtering technique over existing methods.

  5. Reducing the Effects of Background Noise during Auditory Functional Magnetic Resonance Imaging of Speech Processing: Qualitative and Quantitative Comparisons between Two Image Acquisition Schemes and Noise Cancellation

    Science.gov (United States)

    Blackman, Graham A.; Hall, Deborah A.

    2011-01-01

    Purpose: The intense sound generated during functional magnetic resonance imaging (fMRI) complicates studies of speech and hearing. This experiment evaluated the benefits of using active noise cancellation (ANC), which attenuates the level of the scanner sound at the participant's ear by up to 35 dB around the peak at 600 Hz. Method: Speech and…

  6. A Thermal Imaging Instrument with Uncooled Detectors

    Data.gov (United States)

    National Aeronautics and Space Administration — In this proposed work, we will perform an instrument concept study for sustainable thermal imaging over land with uncooled detectors. We will define the science and...

  7. Cryogenic Preamplifiers for Magnetic Resonance Imaging

    DEFF Research Database (Denmark)

    Johansen, Daniel H.; Sanchez-Heredia, Juan D.; Petersen, Jan R.

    2018-01-01

    Pursuing the ultimate limit of detection in magnetic resonance imaging (MRI) requires cryogenics to decrease the thermal noise of the electronic circuits. As cryogenic coils for MRI are slowly emerging cryogenic preamplifiers are required to fully exploit their potential. A cryogenic preamplifier...

  8. Long-distance thermal temporal ghost imaging over optical fibers

    Science.gov (United States)

    Yao, Xin; Zhang, Wei; Li, Hao; You, Lixing; Wang, Zhen; Huang, Yidong

    2018-02-01

    A thermal ghost imaging scheme between two distant parties is proposed and experimentally demonstrated over long-distance optical fibers. In the scheme, the weak thermal light is split into two paths. Photons in one path are spatially diffused according to their frequencies by a spatial dispersion component, then illuminate the object and record its spatial transmission information. Photons in the other path are temporally diffused by a temporal dispersion component. By the coincidence measurement between photons of two paths, the object can be imaged in a way of ghost imaging, based on the frequency correlation between photons in the two paths. In the experiment, the weak thermal light source is prepared by the spontaneous four-wave mixing in a silicon waveguide. The temporal dispersion is introduced by single mode fibers of 50 km, which also could be looked as a fiber link. Experimental results show that this scheme can be realized over long-distance optical fibers.

  9. Optimization on the dose versus noise in the image on protocols for computed tomography of pediatric head

    International Nuclear Information System (INIS)

    Saint'Yves, Thalis L.A.; Travassos, Paulo Cesar B.; Goncalves, Elicardo A.S.; Mecca A, Fernando; Silveira, Thiago B.

    2010-01-01

    This article aims to establish protocols optimized for computed tomography of pediatric skull, to the Picker Q2000 tomography of the Instituto Nacional de Cancer, through the analysis of dose x noise on the image with the variation of values of mAs and kVp. We used a water phantom to measure the noise, a pencil type ionization chamber to measure the dose in the air and the Alderson Randon phantom for check the quality of the image. We found values of mAs and kVp that reduce the skin dose of the original protocol used in 35.9%, maintaining the same image quality at a safe diagnosis. (author)

  10. Thermal imaging of spin Peltier effect

    Science.gov (United States)

    Daimon, Shunsuke; Iguchi, Ryo; Hioki, Tomosato; Saitoh, Eiji; Uchida, Ken-Ichi

    2016-12-01

    The Peltier effect modulates the temperature of a junction comprising two different conductors in response to charge currents across the junction, which is used in solid-state heat pumps and temperature controllers in electronics. Recently, in spintronics, a spin counterpart of the Peltier effect was observed. The `spin Peltier effect' modulates the temperature of a magnetic junction in response to spin currents. Here we report thermal imaging of the spin Peltier effect; using active thermography technique, we visualize the temperature modulation induced by spin currents injected into a magnetic insulator from an adjacent metal. The thermal images reveal characteristic distribution of spin-current-induced heat sources, resulting in the temperature change confined only in the vicinity of the metal/insulator interface. This finding allows us to estimate the actual magnitude of the temperature modulation induced by the spin Peltier effect, which is more than one order of magnitude greater than previously believed.

  11. Occupancy Analysis of Sports Arenas Using Thermal Imaging

    DEFF Research Database (Denmark)

    Gade, Rikke; Jørgensen, Anders; Moeslund, Thomas B.

    2012-01-01

    This paper presents a system for automatic analysis of the occupancy of sports arenas. By using a thermal camera for image capturing the number of persons and their location on the court are found without violating any privacy issues. The images are binarised with an automatic threshold method...

  12. Reliability of a novel thermal imaging system for temperature assessment of healthy feet.

    Science.gov (United States)

    Petrova, N L; Whittam, A; MacDonald, A; Ainarkar, S; Donaldson, A N; Bevans, J; Allen, J; Plassmann, P; Kluwe, B; Ring, F; Rogers, L; Simpson, R; Machin, G; Edmonds, M E

    2018-01-01

    Thermal imaging is a useful modality for identifying preulcerative lesions ("hot spots") in diabetic foot patients. Despite its recognised potential, at present, there is no readily available instrument for routine podiatric assessment of patients at risk. To address this need, a novel thermal imaging system was recently developed. This paper reports the reliability of this device for temperature assessment of healthy feet. Plantar skin foot temperatures were measured with the novel thermal imaging device (Diabetic Foot Ulcer Prevention System (DFUPS), constructed by Photometrix Imaging Ltd) and also with a hand-held infrared spot thermometer (Thermofocus® 01500A3, Tecnimed, Italy) after 20 min of barefoot resting with legs supported and extended in 105 subjects (52 males and 53 females; age range 18 to 69 years) as part of a multicentre clinical trial. The temperature differences between the right and left foot at five regions of interest (ROIs), including 1st and 4th toes, 1st, 3rd and 5th metatarsal heads were calculated. The intra-instrument agreement (three repeated measures) and the inter-instrument agreement (hand-held thermometer and thermal imaging device) were quantified using intra-class correlation coefficients (ICCs) and the 95% confidence intervals (CI). Both devices showed almost perfect agreement in replication by instrument. The intra-instrument ICCs for the thermal imaging device at all five ROIs ranged from 0.95 to 0.97 and the intra-instrument ICCs for the hand-held-thermometer ranged from 0.94 to 0.97. There was substantial to perfect inter-instrument agreement between the hand-held thermometer and the thermal imaging device and the ICCs at all five ROIs ranged between 0.94 and 0.97. This study reports the performance of a novel thermal imaging device in the assessment of foot temperatures in healthy volunteers in comparison with a hand-held infrared thermometer. The newly developed thermal imaging device showed very good agreement in

  13. Thermal imaging in screening of joint inflammation and rheumatoid arthritis in children

    International Nuclear Information System (INIS)

    Lasanen, R; Julkunen, P; Töyräs, J; Piippo-Savolainen, E; Remes-Pakarinen, T; Kröger, L; Heikkilä, A; Karhu, J

    2015-01-01

    Potential of modern thermal imaging for screening and differentiation of joint inflammation has not been assessed in child and juvenile patient populations, typically demanding groups in diagnostics of musculoskeletal disorders. We hypothesize that thermal imaging can detect joint inflammation in patients with juvenile idiopathic arthritis or autoimmune disease with arthritis such as systemic lupus erythematosus. To evaluate the hypothesis, we studied 58 children exhibiting symptoms of joint inflammation. First, the patients’ joints were examined along clinical procedure supplemented with ultrasound imaging when deemed necessary by the clinician. Second, thermal images were acquired from patients’ knees and ankles. Results of thermal imaging were compared to clinical evaluations in knee and ankle. The temperatures were significantly (p max = 0.044, p mean  < 0.001) higher in inflamed ankle joints, but not in inflamed knee joints. No significant difference was found between the skin surface temperatures of medial and lateral aspects of ankle joints. In knee joints the mean temperatures of medial and lateral aspect differed significantly (p = 0.004). We have demonstrated that thermal imaging may have potential for detecting joint inflammation in ankle joints of children. For knee joints our results are inconclusive and further research is warranted. (paper)

  14. Field noise near ferromagnetic films

    Science.gov (United States)

    McMichael, Robert; Liu, Hau-Jian; Yoon, Seungha

    Thermally driven magnetization fluctuations can be viewed as a nuisance noise source or as interesting physics. For example, mag noise in a field sensor may set the minimum detectable field of that sensor. On the other hand, the field noise spectrum reflects the dynamics of the magnetic components, which are essential for device operation. Here, we model the field noise spectrum near the surface of a magnetic film due to thermal spin waves, and we calculate its effect on the T1 relaxation rate of a nearby nitrogen-vacancy (NV) center spin. The model incorporates four components: the spin wave dispersion of the magnetization in a finite-thickness film, thermal excitation of spin waves, the coupling geometry between waves in the film and an external point dipole and finally, the relaxation dynamics of the NV spin. At a distance of 100 nm above a 50 nm thick permalloy film, we find that the strongest stray fields are along the film normal and parallel to the magnetization, on the order of 1 mA m-1 Hz- 1 / 2 or 1 nT Hz- 1 / 2, yielding relaxation times on the order of 10 μs. The spin wave field noise can dominate the intrinsic relaxation, (T1 1 ms) of the NV center spin.

  15. Visualization and measurement by image processing of thermal hydraulic phenomena by neutron radiography

    International Nuclear Information System (INIS)

    Takenaka, Nobuyuki

    1996-01-01

    Neutron Radiography was applied to visualization of thermal hydraulic phenomena and measurement was carried out by image processing the visualized images. Since attenuation of thermal neutron rays is high in ordinary liquids like water and organic fluid while it is low in most of metals, liquid flow behaviors can be visualized through a metallic wall by neutron radiography. Measurement of void fraction and flow vector field which is important to study thermal hydraulic phenomena can be carried out by image processing the images obtained by the visualization. Various two-phase and liquid metal flows were visualized by a JRR-3M thermal neutron radiography system in the present study. Multi-dimensional void fraction distributions in two-phase flows and flow vector fields in liquid metals, which are difficult to measure by the other methods, were successfully measured by image processing. It was shown that neutron radiography was efficiently applicable to study thermal hydraulic phenomena. (author)

  16. Image denoising: Learning the noise model via nonsmooth PDE-constrained optimization

    KAUST Repository

    Reyes, Juan Carlos De los

    2013-11-01

    We propose a nonsmooth PDE-constrained optimization approach for the determination of the correct noise model in total variation (TV) image denoising. An optimization problem for the determination of the weights corresponding to different types of noise distributions is stated and existence of an optimal solution is proved. A tailored regularization approach for the approximation of the optimal parameter values is proposed thereafter and its consistency studied. Additionally, the differentiability of the solution operator is proved and an optimality system characterizing the optimal solutions of each regularized problem is derived. The optimal parameter values are numerically computed by using a quasi-Newton method, together with semismooth Newton type algorithms for the solution of the TV-subproblems. © 2013 American Institute of Mathematical Sciences.

  17. Image denoising: Learning the noise model via nonsmooth PDE-constrained optimization

    KAUST Repository

    Reyes, Juan Carlos De los; Schö nlieb, Carola-Bibiane

    2013-01-01

    We propose a nonsmooth PDE-constrained optimization approach for the determination of the correct noise model in total variation (TV) image denoising. An optimization problem for the determination of the weights corresponding to different types of noise distributions is stated and existence of an optimal solution is proved. A tailored regularization approach for the approximation of the optimal parameter values is proposed thereafter and its consistency studied. Additionally, the differentiability of the solution operator is proved and an optimality system characterizing the optimal solutions of each regularized problem is derived. The optimal parameter values are numerically computed by using a quasi-Newton method, together with semismooth Newton type algorithms for the solution of the TV-subproblems. © 2013 American Institute of Mathematical Sciences.

  18. STUDY ON SHADOW EFFECTS OF VARIOUS FEATURES ON CLOSE RANGE THERMAL IMAGES

    Directory of Open Access Journals (Sweden)

    C. L. Liao

    2012-07-01

    Full Text Available Thermal infrared data become more popular in remote sensing investigation, for it could be acquired both in day and night. The change of temperature has special characteristic in natural environment, so the thermal infrared images could be used in monitoring volcanic landform, the urban development, and disaster prevention. Heat shadow is formed by reflecting radiating capacity which followed the objects. Because of poor spatial resolution of thermal infrared images in satellite sensor, shadow effects were usually ignored. This research focus on discussing the shadow effects of various features, which include metals and nonmetallic materials. An area-based thermal sensor, FLIR-T360 was selected to acquire thermal images. Various features with different emissivity were chosen as reflective surface to obtain thermal shadow in normal atmospheric temperature. Experiments found that the shadow effects depend on the distance between sensors and features, depression angle, object temperature and emissivity of reflective surface. The causes of shadow effects have been altered in the experiment for analyzing the variance in thermal infrared images. The result shows that there were quite different impacts by shadow effects between metals and nonmetallic materials. The further research would be produced a math model to describe the shadow effects of different features in the future work.

  19. ELLIPTICAL WEIGHTED HOLICs FOR WEAK LENSING SHEAR MEASUREMENT. III. THE EFFECT OF RANDOM COUNT NOISE ON IMAGE MOMENTS IN WEAK LENSING ANALYSIS

    International Nuclear Information System (INIS)

    Okura, Yuki; Futamase, Toshifumi

    2013-01-01

    This is the third paper on the improvement of systematic errors in weak lensing analysis using an elliptical weight function, referred to as E-HOLICs. In previous papers, we succeeded in avoiding errors that depend on the ellipticity of the background image. In this paper, we investigate the systematic error that depends on the signal-to-noise ratio of the background image. We find that the origin of this error is the random count noise that comes from the Poisson noise of sky counts. The random count noise makes additional moments and centroid shift error, and those first-order effects are canceled in averaging, but the second-order effects are not canceled. We derive the formulae that correct this systematic error due to the random count noise in measuring the moments and ellipticity of the background image. The correction formulae obtained are expressed as combinations of complex moments of the image, and thus can correct the systematic errors caused by each object. We test their validity using a simulated image and find that the systematic error becomes less than 1% in the measured ellipticity for objects with an IMCAT significance threshold of ν ∼ 11.7.

  20. Removal of jitter noise in 3D shape recovery from image focus by using Kalman filter.

    Science.gov (United States)

    Jang, Hoon-Seok; Muhammad, Mannan Saeed; Choi, Tae-Sun

    2018-02-01

    In regard to Shape from Focus, one critical factor impacting system application is mechanical vibration of the translational stage causing jitter noise along the optical axis. This noise is not detectable by simply observing the image. However, when focus measures are applied, inaccuracies in the depth occur. In this article, jitter noise and focus curves are modeled by Gaussian distribution and quadratic function, respectively. Then Kalman filter is designed and applied to eliminate this noise in the focus curves, as a post-processing step after the focus measure application. Experiments are implemented with simulated objects and real objects to show usefulness of proposed algorithm. © 2017 Wiley Periodicals, Inc.

  1. Thermal noise due to surface-charge effects within the Debye layer of endogenous structures in dendrites.

    Science.gov (United States)

    Poznanski, Roman R

    2010-02-01

    An assumption commonly used in cable theory is revised by taking into account electrical amplification due to intracellular capacitive effects in passive dendritic cables. A generalized cable equation for a cylindrical volume representation of a dendritic segment is derived from Maxwell's equations under assumptions: (i) the electric-field polarization is restricted longitudinally along the cable length; (ii) extracellular isopotentiality; (iii) quasielectrostatic conditions; and (iv) homogeneous medium with constant conductivity and permittivity. The generalized cable equation is identical to Barenblatt's equation arising in the theory of infiltration in fissured strata with a known analytical solution expressed in terms of a definite integral involving a modified Bessel function and the solution to a linear one-dimensional classical cable equation. Its solution is used to determine the impact of thermal noise on voltage attenuation with distance at any particular time. A regular perturbation expansion for the membrane potential about the linear one-dimensional classical cable equation solution is derived in terms of a Green's function in order to describe the dynamics of free charge within the Debye layer of endogenous structures in passive dendritic cables. The asymptotic value of the first perturbative term is explicitly evaluated for small values of time to predict how the slowly fluctuating (in submillisecond range) electric field attributed to intracellular capacitive effects alters the amplitude of the membrane potential. It was found that capacitive effects are almost negligible for cables with electrotonic lengths L>0.5 , contributes up to 10% of the signal for cables with electrotonic lengths in the range between 0.25thermal noise due to

  2. Device-independent quantum reading and noise-assisted quantum transmitters

    International Nuclear Information System (INIS)

    Roga, W; Buono, D; Illuminati, F

    2015-01-01

    In quantum reading, a quantum state of light (transmitter) is applied to read classical information. In the presence of noise or for sufficiently weak signals, quantum reading can outperform classical reading by reason of enhanced state distinguishability. Here we show that enhanced quantum efficiency depends on the presence in the transmitter of a particular type of quantum correlations, the discord of response. Different encodings and transmitters give rise to different levels of efficiency. Considering noisy quantum probes, we show that squeezed thermal transmitters with non-symmetrically distributed noise among the field modes yield higher quantum efficiency compared with coherent thermal quantum states. The noise-enhanced quantum advantage is a consequence of the discord of response being a non-decreasing function of increasing thermal noise under constant squeezing, a behavior that leads to increased state distinguishability. We finally show that, for non-symmetric squeezed thermal states, the probability of error, as measured by the quantum Chernoff bound, vanishes asymptotically with increasing local thermal noise with finite global squeezing. Therefore, with fixed finite squeezing, noisy but strongly discordant quantum states with a large noise imbalance between the field modes can outperform noisy classical resources as well as pure entangled transmitters with the same finite level of squeezing. (paper)

  3. Enhance wound healing monitoring through a thermal imaging based smartphone app

    Science.gov (United States)

    Yi, Steven; Lu, Minta; Yee, Adam; Harmon, John; Meng, Frank; Hinduja, Saurabh

    2018-03-01

    In this paper, we present a thermal imaging based app to augment traditional appearance based wound growth monitoring. Accurate diagnose and track of wound healing enables physicians to effectively assess, document, and individualize the treatment plan given to each wound patient. Currently, wounds are primarily examined by physicians through visual appearance and wound area. However, visual information alone cannot present a complete picture on a wound's condition. In this paper, we use a smartphone attached thermal imager and evaluate its effectiveness on augmenting visual appearance based wound diagnosis. Instead of only monitoring wound temperature changes on a wound, our app presents physicians a comprehensive measurements including relative temperature, wound healing thermal index, and wound blood flow. Through the rat wound experiments and by monitoring the integrated thermal measurements over 3 weeks of time frame, our app is able to show the underlying healing process through the blood flow. The implied significance of our app design and experiment includes: (a) It is possible to use a low cost smartphone attached thermal imager for added value on wound assessment, tracking, and treatment; and (b) Thermal mobile app can be used for remote wound healing assessment for mobile health based solution.

  4. Fourier-transform ghost imaging with pure far-field correlated thermal light

    International Nuclear Information System (INIS)

    Liu Honglin; Shen Xia; Han Shensheng; Zhu Daming

    2007-01-01

    Pure far-field correlated thermal light beams are created with phase grating, and Fourier-transform ghost imaging depending only on the far-field correlation is demonstrated experimentally. Theoretical analysis and the results of experimental investigation of this pure far-field correlated thermal light are presented. Applications which may be exploited with this imaging scheme are discussed

  5. Characterization of Noise Signatures of Involuntary Head Motion in the Autism Brain Imaging Data Exchange Repository

    Science.gov (United States)

    Caballero, Carla; Mistry, Sejal; Vero, Joe; Torres, Elizabeth B

    2018-01-01

    The variability inherently present in biophysical data is partly contributed by disparate sampling resolutions across instrumentations. This poses a potential problem for statistical inference using pooled data in open access repositories. Such repositories combine data collected from multiple research sites using variable sampling resolutions. One example is the Autism Brain Imaging Data Exchange repository containing thousands of imaging and demographic records from participants in the spectrum of autism and age-matched neurotypical controls. Further, statistical analyses of groups from different diagnoses and demographics may be challenging, owing to the disparate number of participants across different clinical subgroups. In this paper, we examine the noise signatures of head motion data extracted from resting state fMRI data harnessed under different sampling resolutions. We characterize the quality of the noise in the variability of the raw linear and angular speeds for different clinical phenotypes in relation to age-matched controls. Further, we use bootstrapping methods to ensure compatible group sizes for statistical comparison and report the ranges of physical involuntary head excursions of these groups. We conclude that different sampling rates do affect the quality of noise in the variability of head motion data and, consequently, the type of random process appropriate to characterize the time series data. Further, given a qualitative range of noise, from pink to brown noise, it is possible to characterize different clinical subtypes and distinguish them in relation to ranges of neurotypical controls. These results may be of relevance to the pre-processing stages of the pipeline of analyses of resting state fMRI data, whereby head motion enters the criteria to clean imaging data from motion artifacts. PMID:29556179

  6. Characterization of Noise Signatures of Involuntary Head Motion in the Autism Brain Imaging Data Exchange Repository

    Directory of Open Access Journals (Sweden)

    Carla Caballero

    2018-03-01

    Full Text Available The variability inherently present in biophysical data is partly contributed by disparate sampling resolutions across instrumentations. This poses a potential problem for statistical inference using pooled data in open access repositories. Such repositories combine data collected from multiple research sites using variable sampling resolutions. One example is the Autism Brain Imaging Data Exchange repository containing thousands of imaging and demographic records from participants in the spectrum of autism and age-matched neurotypical controls. Further, statistical analyses of groups from different diagnoses and demographics may be challenging, owing to the disparate number of participants across different clinical subgroups. In this paper, we examine the noise signatures of head motion data extracted from resting state fMRI data harnessed under different sampling resolutions. We characterize the quality of the noise in the variability of the raw linear and angular speeds for different clinical phenotypes in relation to age-matched controls. Further, we use bootstrapping methods to ensure compatible group sizes for statistical comparison and report the ranges of physical involuntary head excursions of these groups. We conclude that different sampling rates do affect the quality of noise in the variability of head motion data and, consequently, the type of random process appropriate to characterize the time series data. Further, given a qualitative range of noise, from pink to brown noise, it is possible to characterize different clinical subtypes and distinguish them in relation to ranges of neurotypical controls. These results may be of relevance to the pre-processing stages of the pipeline of analyses of resting state fMRI data, whereby head motion enters the criteria to clean imaging data from motion artifacts.

  7. A simplified method of estimating noise power spectra

    International Nuclear Information System (INIS)

    Hanson, K.M.

    1998-01-01

    A technique to estimate the radial dependence of the noise power spectrum of images is proposed in which the calculations are conducted solely in the spatial domain of the noise image. The noise power spectrum averaged over a radial spatial-frequency interval is obtained form the variance of a noise image that has been convolved with a small kernel that approximates a Laplacian operator. Recursive consolidation of the image by factors of two in each dimension yields estimates of the noise power spectrum over that full range of spatial frequencies

  8. Two-dimensional fruit ripeness estimation using thermal imaging

    Science.gov (United States)

    Sumriddetchkajorn, Sarun; Intaravanne, Yuttana

    2013-06-01

    Some green fruits do not change their color from green to yellow when being ripe. As a result, ripeness estimation via color and fluorescent analytical approaches cannot be applied. In this article, we propose and show for the first time how a thermal imaging camera can be used to two-dimensionally classify fruits into different ripeness levels. Our key idea relies on the fact that the mature fruits have higher heat capacity than the immature ones and therefore the change in surface temperature overtime is slower. Our experimental proof of concept using a thermal imaging camera shows a promising result in non-destructively identifying three different ripeness levels of mangoes Mangifera indica L.

  9. Design and development of a very high resolution thermal imager

    Science.gov (United States)

    Kuerbitz, Gunther; Duchateau, Ruediger

    1998-10-01

    The design goal of this project was to develop a thermal imaging system with ultimate geometrical resolution without sacrificing thermal sensitivity. It was necessary to fulfil the criteria for a future advanced video standard. This video standard is the so-called HDTV standard (HDTV High Definition TeleVision). The thermal imaging system is a parallel scanning system working in the 7...11 micrometer spectral region. The detector for that system has to have 576 X n (n number of TDI stages) detector elements taking into account a twofold interlace. It must be carefully optimized in terms of range performance and size of optics entrance pupil as well as producibility and yield. This was done in strong interaction with the detector manufacturer. The 16:9 aspect ratio of the HDTV standard together with the high number of 1920 pixels/line impose high demands on the scanner design in terms of scan efficiency and linearity. As an advanced second generation thermal imager the system has an internal thermal reference. The electronics is fully digitized and comprises circuits for Non Uniformity Correction (NUC), scan conversion, electronic zoom, auto gain and level, edge enhancement, up/down and left/right reversion etc. It can be completely remote-controlled via a serial interface.

  10. Utilizing Structure-from-Motion Photogrammetry with Airborne Visual and Thermal Images to Monitor Thermal Areas in Yellowstone National Park

    Science.gov (United States)

    Carr, B. B.; Vaughan, R. G.

    2017-12-01

    The thermal areas in Yellowstone National Park (Wyoming, USA) are constantly changing. Persistent monitoring of these areas is necessary to better understand the behavior and potential hazards of both the thermal features and the deeper hydrothermal system driving the observed surface activity. As part of the Park's monitoring program, thousands of visual and thermal infrared (TIR) images have been acquired from a variety of airborne platforms over the past decade. We have used structure-from-motion (SfM) photogrammetry techniques to generate a variety of data products from these images, including orthomosaics, temperature maps, and digital elevation models (DEMs). Temperature maps were generated for Upper Geyser Basin and Norris Geyser Basin for the years 2009-2015, by applying SfM to nighttime TIR images collected from an aircraft-mounted forward-looking infrared (FLIR) camera. Temperature data were preserved through the SfM processing by applying a uniform linear stretch over the entire image set to convert between temperature and a 16-bit digital number. Mosaicked temperature maps were compared to the original FLIR image frames and to ground-based temperature data to constrain the accuracy of the method. Due to pixel averaging and resampling, among other issues, the derived temperature values are typically within 5-10 ° of the values of the un-resampled image frame. We also created sub-meter resolution DEMs from airborne daytime visual images of individual thermal areas. These DEMs can be used for resource and hazard management, and in cases where multiple DEMs exist from different times, for measuring topographic change, including change due to thermal activity. For example, we examined the sensitivity of the DEMs to topographic change by comparing DEMs of the travertine terraces at Mammoth Hot Springs, which can grow at > 1 m per year. These methods are generally applicable to images from airborne platforms, including planes, helicopters, and unmanned aerial

  11. Design of CMOS Tunable Image-Rejection Low-Noise Amplifier with Active Inductor

    Directory of Open Access Journals (Sweden)

    Ler Chun Lee

    2008-01-01

    Full Text Available A fully integrated CMOS tunable image-rejection low-noise amplifier (IRLNA has been designed using Silterra's industry standard 0.18 μm RF CMOS process. The notch filter is designed using an active inductor. Measurement results show that the notch filter designed using active inductor contributes additional 1.19 dB to the noise figure of the low-noise amplifier (LNA. A better result is possible if the active inductor is optimized. Since active inductors require less die area, the die area occupied by the IRLNA is not significantly different from a conventional LNA, which was designed for comparison. The proposed IRLNA exhibits S21 of 11.8 dB, S11 of −17.8 dB, S22 of −10.7 dB, and input 1 dB compression point of −12 dBm at 3 GHz

  12. Thickness measurement by two-sided step-heating thermal imaging

    Science.gov (United States)

    Li, Xiaoli; Tao, Ning; Sun, J. G.; Zhang, Cunlin; Zhao, Yuejin

    2018-01-01

    Infrared thermal imaging is a promising nondestructive technique for thickness prediction. However, it is usually thought to be only appropriate for testing the thickness of thin objects or near-surface structures. In this study, we present a new two-sided step-heating thermal imaging method which employed a low-cost portable halogen lamp as the heating source and verified it with two stainless steel step wedges with thicknesses ranging from 5 mm to 24 mm. We first derived the one-dimensional step-heating thermography theory with the consideration of warm-up time of the lamp, and then applied the nonlinear regression method to fit the experimental data by the derived function to determine the thickness. After evaluating the reliability and accuracy of the experimental results, we concluded that this method is capable of testing thick objects. In addition, we provided the criterions for both the required data length and the applicable thickness range of the testing material. It is evident that this method will broaden the thermal imaging application for thickness measurement.

  13. TU-F-CAMPUS-I-04: Head-Only Asymmetric Gradient System Evaluation: ACR Image Quality and Acoustic Noise

    Energy Technology Data Exchange (ETDEWEB)

    Weavers, P; Shu, Y; Tao, S; Bernstein, M [Mayo Clinic, Rochester, Minnesota (United States); Lee, S; Piel, J; Foo, T [GE Global Research, Niskayuna, NY (United States); Mathieu, J-B [GE Healthcare, Florence, SC (Italy)

    2015-06-15

    Purpose: A high-performance head-only magnetic resonance imaging gradient system with an acquisition volume of 26 cm employing an asymmetric design for the transverse coils has been developed. It is able to reach a magnitude of 85 mT/m at a slew rate of 700 T/m/s, but operated at 80 mT/m and 500 T/m/s for this test. A challenge resulting from this asymmetric design is that the gradient nonlinearly exhibits both odd- and even-ordered terms, and as the full imaging field of view is often used, the nonlinearity is pronounced. The purpose of this work is to show the system can produce clinically useful images after an on-site gradient nonlinearity calibration and correction, and show that acoustic noise levels fall within non-significant risk (NSR) limits for standard clinical pulse sequences. Methods: The head-only gradient system was inserted into a standard 3T wide-bore scanner without acoustic damping. The ACR phantom was scanned in an 8-channel receive-only head coil and the standard American College of Radiology (ACR) MRI quality control (QC) test was performed. Acoustic noise levels were measured for several standard pulse sequences. Results: Images acquired with the head-only gradient system passed all ACR MR image quality tests; Both even and odd-order gradient distortion correction terms were required for the asymmetric gradients to pass. Acoustic noise measurements were within FDA NSR guidelines of 99 dBA (with assumed 20 dBA hearing protection) A-weighted and 140 dB for peak for all but one sequence. Note the gradient system was installed without any shroud or acoustic batting. We expect final system integration to greatly reduce noise experienced by the patient. Conclusion: A high-performance head-only asymmetric gradient system operating at 80 mT/m and 500 T/m/s conforms to FDA acoustic noise limits in all but one case, and passes all the ACR MR image quality control tests. This work was supported in part by the NIH grant 5R01EB010065.

  14. TU-F-CAMPUS-I-04: Head-Only Asymmetric Gradient System Evaluation: ACR Image Quality and Acoustic Noise

    International Nuclear Information System (INIS)

    Weavers, P; Shu, Y; Tao, S; Bernstein, M; Lee, S; Piel, J; Foo, T; Mathieu, J-B

    2015-01-01

    Purpose: A high-performance head-only magnetic resonance imaging gradient system with an acquisition volume of 26 cm employing an asymmetric design for the transverse coils has been developed. It is able to reach a magnitude of 85 mT/m at a slew rate of 700 T/m/s, but operated at 80 mT/m and 500 T/m/s for this test. A challenge resulting from this asymmetric design is that the gradient nonlinearly exhibits both odd- and even-ordered terms, and as the full imaging field of view is often used, the nonlinearity is pronounced. The purpose of this work is to show the system can produce clinically useful images after an on-site gradient nonlinearity calibration and correction, and show that acoustic noise levels fall within non-significant risk (NSR) limits for standard clinical pulse sequences. Methods: The head-only gradient system was inserted into a standard 3T wide-bore scanner without acoustic damping. The ACR phantom was scanned in an 8-channel receive-only head coil and the standard American College of Radiology (ACR) MRI quality control (QC) test was performed. Acoustic noise levels were measured for several standard pulse sequences. Results: Images acquired with the head-only gradient system passed all ACR MR image quality tests; Both even and odd-order gradient distortion correction terms were required for the asymmetric gradients to pass. Acoustic noise measurements were within FDA NSR guidelines of 99 dBA (with assumed 20 dBA hearing protection) A-weighted and 140 dB for peak for all but one sequence. Note the gradient system was installed without any shroud or acoustic batting. We expect final system integration to greatly reduce noise experienced by the patient. Conclusion: A high-performance head-only asymmetric gradient system operating at 80 mT/m and 500 T/m/s conforms to FDA acoustic noise limits in all but one case, and passes all the ACR MR image quality control tests. This work was supported in part by the NIH grant 5R01EB010065

  15. Assessment of noise reduction potential and image quality improvement of a new generation adaptive statistical iterative reconstruction (ASIR-V) in chest CT.

    Science.gov (United States)

    Tang, Hui; Yu, Nan; Jia, Yongjun; Yu, Yong; Duan, Haifeng; Han, Dong; Ma, Guangming; Ren, Chenglong; He, Taiping

    2018-01-01

    To evaluate the image quality improvement and noise reduction in routine dose, non-enhanced chest CT imaging by using a new generation adaptive statistical iterative reconstruction (ASIR-V) in comparison with ASIR algorithm. 30 patients who underwent routine dose, non-enhanced chest CT using GE Discovery CT750HU (GE Healthcare, Waukesha, WI) were included. The scan parameters included tube voltage of 120 kVp, automatic tube current modulation to obtain a noise index of 14HU, rotation speed of 0.6 s, pitch of 1.375:1 and slice thickness of 5 mm. After scanning, all scans were reconstructed with the recommended level of 40%ASIR for comparison purpose and different percentages of ASIR-V from 10% to 100% in a 10% increment. The CT attenuation values and SD of the subcutaneous fat, back muscle and descending aorta were measured at the level of tracheal carina of all reconstructed images. The signal-to-noise ratio (SNR) was calculated with SD representing image noise. The subjective image quality was independently evaluated by two experienced radiologists. For all ASIR-V images, the objective image noise (SD) of fat, muscle and aorta decreased and SNR increased along with increasing ASIR-V percentage. The SD of 30% ASIR-V to 100% ASIR-V was significantly lower than that of 40% ASIR (p ASIR-V reconstructions had good diagnostic acceptability. However, the 50% ASIR-V to 70% ASIR-V series showed significantly superior visibility of small structures when compared with the 40% ASIR and ASIR-V of other percentages (p ASIR-V was the best series of all ASIR-V images, with a highest subjective image quality. The image sharpness was significantly decreased in images reconstructed by 80% ASIR-V and higher. In routine dose, non-enhanced chest CT, ASIR-V shows greater potential in reducing image noise and artefacts and maintaining image sharpness when compared to the recommended level of 40%ASIR algorithm. Combining both the objective and subjective evaluation of images, non

  16. Evaluation of the Accuracy of the Dark Frame Subtraction Method in CCD Image Processing

    National Research Council Canada - National Science Library

    Levesque, Martin P; Lelievre, Mario

    2007-01-01

    .... This method is frequently used for removing the image background gradient (a thermal artefact) in CCD images. This report demonstrates that this method may not be suitable for the detection of objects with very low signal-to-noise ratio...

  17. Digital Image Forgery Detection Using JPEG Features and Local Noise Discrepancies

    Directory of Open Access Journals (Sweden)

    Bo Liu

    2014-01-01

    Full Text Available Wide availability of image processing software makes counterfeiting become an easy and low-cost way to distort or conceal facts. Driven by great needs for valid forensic technique, many methods have been proposed to expose such forgeries. In this paper, we proposed an integrated algorithm which was able to detect two commonly used fraud practices: copy-move and splicing forgery in digital picture. To achieve this target, a special descriptor for each block was created combining the feature from JPEG block artificial grid with that from noise estimation. And forehand image quality assessment procedure reconciled these different features by setting proper weights. Experimental results showed that, compared to existing algorithms, our proposed method is effective on detecting both copy-move and splicing forgery regardless of JPEG compression ratio of the input image.

  18. Amplifiers Exploiting Thermal Noise Canceling: A Review

    OpenAIRE

    Klumperink, Eric A.M.; Bruccoleri, Federico; Stroet, Peter; Nauta, Bram

    2004-01-01

    Wide-band LNAs suffer from a fundamental trade-off between noise figure NF and source impedance matching, which limits NF to values typically above 3dB. Recently, a feed-forward noise canceling technique has been proposed to break this trade-off. This paper reviews the principle of the technique and its key properties. Although the technique has been applied to wideband CMOS LNAs, it can just as well be implemented exploiting transconductance elements realized with oth...

  19. Achieving high signal-to-noise performance for a velocity-map imaging experiment

    International Nuclear Information System (INIS)

    Roberts, E.H.; Cavanagh, S.J.; Gibson, S.T.; Lewis, B.R.; Dedman, C.J.; Picker, G.J.

    2005-01-01

    Since the publication of the pioneering paper on velocity-map imaging in 1997, by Eppink and Parker [A.T.J.B. Eppink, D.H. Parker, Rev. Sci. Instrum. 68 (1997) 3477], numerous groups have applied this method in a variety of ways and to various targets. However, despite this interest, little attention has been given to the inherent difficulties and problems associated with this method. In implementing a velocity-map imaging system for photoelectron spectroscopy for the photo-detachment of anion radicals, we have developed a coaxial velocity-map imaging spectrometer. Examined are the advantages and disadvantages of such a system, in particular the sources of noise and the methods used to reduce it

  20. Theoretical scheme of thermal-light many-ghost imaging by Nth-order intensity correlation

    International Nuclear Information System (INIS)

    Liu Yingchuan; Kuang Leman

    2011-01-01

    In this paper, we propose a theoretical scheme of many-ghost imaging in terms of Nth-order correlated thermal light. We obtain the Gaussian thin lens equations in the many-ghost imaging protocol. We show that it is possible to produce N-1 ghost images of an object at different places in a nonlocal fashion by means of a higher order correlated imaging process with an Nth-order correlated thermal source and correlation measurements. We investigate the visibility of the ghost images in the scheme and obtain the upper bounds of the visibility for the Nth-order correlated thermal-light ghost imaging. It is found that the visibility of the ghost images can be dramatically enhanced when the order of correlation becomes larger. It is pointed out that the many-ghost imaging phenomenon is an observable physical effect induced by higher order coherence or higher order correlations of optical fields.

  1. Effect of cantilever geometry on the optical lever sensitivities and thermal noise method of the atomic force microscope.

    Science.gov (United States)

    Sader, John E; Lu, Jianing; Mulvaney, Paul

    2014-11-01

    Calibration of the optical lever sensitivities of atomic force microscope (AFM) cantilevers is especially important for determining the force in AFM measurements. These sensitivities depend critically on the cantilever mode used and are known to differ for static and dynamic measurements. Here, we calculate the ratio of the dynamic and static sensitivities for several common AFM cantilevers, whose shapes vary considerably, and experimentally verify these results. The dynamic-to-static optical lever sensitivity ratio is found to range from 1.09 to 1.41 for the cantilevers studied - in stark contrast to the constant value of 1.09 used widely in current calibration studies. This analysis shows that accuracy of the thermal noise method for the static spring constant is strongly dependent on cantilever geometry - neglect of these dynamic-to-static factors can induce errors exceeding 100%. We also discuss a simple experimental approach to non-invasively and simultaneously determine the dynamic and static spring constants and optical lever sensitivities of cantilevers of arbitrary shape, which is applicable to all AFM platforms that have the thermal noise method for spring constant calibration.

  2. Spin noise spectroscopy of ZnO

    Science.gov (United States)

    Horn, H.; Berski, F.; Balocchi, A.; Marie, X.; Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A.; Hübner, J.; Oestreich, M.

    2013-12-01

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  3. Spin noise spectroscopy of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Horn, H.; Berski, F.; Hübner, J.; Oestreich, M. [Institute for Solid State Physics, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany); Balocchi, A.; Marie, X. [INSA-CNRS-UPS, LPCNO, Université de Toulouse, 135 Av. de Rangueil, 31077 Toulouse (France); Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A. [Institute of Semiconductor Technology, Technische Universität Braunschweig, Hans-Sommer-Straße 66, 38106 Braunschweig (Germany)

    2013-12-04

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  4. A novel segmentation method for uneven lighting image with noise injection based on non-local spatial information and intuitionistic fuzzy entropy

    Science.gov (United States)

    Yu, Haiyan; Fan, Jiulun

    2017-12-01

    Local thresholding methods for uneven lighting image segmentation always have the limitations that they are very sensitive to noise injection and that the performance relies largely upon the choice of the initial window size. This paper proposes a novel algorithm for segmenting uneven lighting images with strong noise injection based on non-local spatial information and intuitionistic fuzzy theory. We regard an image as a gray wave in three-dimensional space, which is composed of many peaks and troughs, and these peaks and troughs can divide the image into many local sub-regions in different directions. Our algorithm computes the relative characteristic of each pixel located in the corresponding sub-region based on fuzzy membership function and uses it to replace its absolute characteristic (its gray level) to reduce the influence of uneven light on image segmentation. At the same time, the non-local adaptive spatial constraints of pixels are introduced to avoid noise interference with the search of local sub-regions and the computation of local characteristics. Moreover, edge information is also taken into account to avoid false peak and trough labeling. Finally, a global method based on intuitionistic fuzzy entropy is employed on the wave transformation image to obtain the segmented result. Experiments on several test images show that the proposed method has excellent capability of decreasing the influence of uneven illumination on images and noise injection and behaves more robustly than several classical global and local thresholding methods.

  5. PCA-based approach for subtracting thermal background emission in high-contrast imaging data

    Science.gov (United States)

    Hunziker, S.; Quanz, S. P.; Amara, A.; Meyer, M. R.

    2018-03-01

    Aims.Ground-based observations at thermal infrared wavelengths suffer from large background radiation due to the sky, telescope and warm surfaces in the instrument. This significantly limits the sensitivity of ground-based observations at wavelengths longer than 3 μm. The main purpose of this work is to analyse this background emission in infrared high-contrast imaging data as illustrative of the problem, show how it can be modelled and subtracted and demonstrate that it can improve the detection of faint sources, such as exoplanets. Methods: We used principal component analysis (PCA) to model and subtract the thermal background emission in three archival high-contrast angular differential imaging datasets in the M' and L' filter. We used an M' dataset of β Pic to describe in detail how the algorithm works and explain how it can be applied. The results of the background subtraction are compared to the results from a conventional mean background subtraction scheme applied to the same dataset. Finally, both methods for background subtraction are compared by performing complete data reductions. We analysed the results from the M' dataset of HD 100546 only qualitatively. For the M' band dataset of β Pic and the L' band dataset of HD 169142, which was obtained with an angular groove phase mask vortex vector coronagraph, we also calculated and analysed the achieved signal-to-noise ratio (S/N). Results: We show that applying PCA is an effective way to remove spatially and temporarily varying thermal background emission down to close to the background limit. The procedure also proves to be very successful at reconstructing the background that is hidden behind the point spread function. In the complete data reductions, we find at least qualitative improvements for HD 100546 and HD 169142, however, we fail to find a significant increase in S/N of β Pic b. We discuss these findings and argue that in particular datasets with strongly varying observing conditions or

  6. Influence of ASIR (Adaptative Statistical Iterative Reconstruction) variation in the image noise of computerized tomography for high voltage

    International Nuclear Information System (INIS)

    Mendes, L.M.M.; Pereira, W.B.R.; Vieira, J.G.; Lamounier, C.S.; Gonçalves, D.A.; Carvalho, G.N.P.; Santana, P.C.; Oliveira, P.M.C.; Reis, L.P.

    2017-01-01

    Computed tomography had great advances in the equipment used in the diagnostic practice, directly influencing the levels of radiation for the patient. It is essential to optimize techniques that must be employed to comply with the ALARA (As Low As Reasonably Achievable) principle of radioprotection. The relationship of ASIR (Adaptive Statistical Iterative Reconstruction) with image noise was studied. Central images of a homogeneous water simulator were obtained in a 20 mm scan using a 64-channel Lightspeed VCT tomograph of General Electric in helical acquisitions with a rotation time of 0.5 seconds, Pitch 0.984: 1, and thickness of cut 0.625 mm. All these constant parameters varying the voltage in two distinct values: 120 and 140 kV with use of the automatic current by the CAE (Automatic Exposure Control), ranging from 50 to 675 mA (120 kV) and from 50 to 610 mA (140kV), minimum and maximum values, respectively allowed for each voltage. Image noise was determined through ImageJ free software. The analysis of the obtained data compared the percentage variation of the noise in the image based on the ASIR value of 10%, concluding that there is a variation of approximately 50% when compared to the values of ASIR (100%) in both tensions. Dose evaluation is required in future studies to better utilize the relationship between dose and image quality

  7. Thermal Noise Canceling in LNAs: A Review

    OpenAIRE

    Nauta, Bram; Klumperink, Eric A.M.; Bruccoleri, Frederico

    2004-01-01

    Most wide-band amplifiers suffer from a fundamental trade-off between noise figure NF and source impedance matching, which limits NF to values typically above 3dB. Recently, a feed-forward noise canceling technique has been proposed to break this trade-off. This paper reviews the principle of the technique and its key properties. Although the technique has been applied to wideband CMOS LNAs, it can just as well be implemented exploiting transconductance elements realized with other types of t...

  8. Digital Enhancement of Night Vision and Thermal Images

    National Research Council Canada - National Science Library

    Teo, Chek

    2003-01-01

    .... This thesis explores the effect of the Contrast Limited Adaptive Histogram Equalization (CLAHE) process on night vision and thermal images With better contrast, target detection and discrimination can be improved...

  9. A machine learning approach to quantifying noise in medical images

    Science.gov (United States)

    Chowdhury, Aritra; Sevinsky, Christopher J.; Yener, Bülent; Aggour, Kareem S.; Gustafson, Steven M.

    2016-03-01

    As advances in medical imaging technology are resulting in significant growth of biomedical image data, new techniques are needed to automate the process of identifying images of low quality. Automation is needed because it is very time consuming for a domain expert such as a medical practitioner or a biologist to manually separate good images from bad ones. While there are plenty of de-noising algorithms in the literature, their focus is on designing filters which are necessary but not sufficient for determining how useful an image is to a domain expert. Thus a computational tool is needed to assign a score to each image based on its perceived quality. In this paper, we introduce a machine learning-based score and call it the Quality of Image (QoI) score. The QoI score is computed by combining the confidence values of two popular classification techniques—support vector machines (SVMs) and Naïve Bayes classifiers. We test our technique on clinical image data obtained from cancerous tissue samples. We used 747 tissue samples that are stained by four different markers (abbreviated as CK15, pck26, E_cad and Vimentin) leading to a total of 2,988 images. The results show that images can be classified as good (high QoI), bad (low QoI) or ugly (intermediate QoI) based on their QoI scores. Our automated labeling is in agreement with the domain experts with a bi-modal classification accuracy of 94%, on average. Furthermore, ugly images can be recovered and forwarded for further post-processing.

  10. Geant4 Analysis of a Thermal Neutron Real-Time Imaging System

    Science.gov (United States)

    Datta, Arka; Hawari, Ayman I.

    2017-07-01

    Thermal neutron imaging is a technique for nondestructive testing providing complementary information to X-ray imaging for a wide range of applications in science and engineering. Advancement of electronic imaging systems makes it possible to obtain neutron radiographs in real time. This method requires a scintillator to convert neutrons to optical photons and a charge-coupled device (CCD) camera to detect those photons. Alongside, a well collimated beam which reduces geometrical blurriness, the use of a thin scintillator can improve the spatial resolution significantly. A representative scintillator that has been applied widely for thermal neutron imaging is 6LiF:ZnS (Ag). In this paper, a multiphysics simulation approach for designing thermal neutron imaging system is investigated. The Geant4 code is used to investigate the performance of a thermal neutron imaging system starting with a neutron source and including the production of charged particles and optical photons in the scintillator and their transport for image formation in the detector. The simulation geometry includes the neutron beam collimator and sapphire filter. The 6LiF:ZnS (Ag) scintillator is modeled along with a pixelated detector for image recording. The spatial resolution of the system was obtained as the thickness of the scintillator screen was varied between 50 and 400 μm. The results of the simulation were compared to experimental results, including measurements performed using the PULSTAR nuclear reactor imaging beam, showing good agreement. Using the established model, further examination showed that the resolution contribution of the scintillator screen is correlated with its thickness and the range of the neutron absorption reaction products (i.e., the alpha and triton particles). Consequently, thinner screens exhibit improved spatial resolution. However, this will compromise detection efficiency due to the reduced probability of neutron absorption.

  11. In-flight thermal experiments for LISA Pathfinder: Simulating temperature noise at the Inertial Sensors

    International Nuclear Information System (INIS)

    Armano, M; Audley, H; Born, M; Danzmann, K; Diepholz, I; Auger, G; Binetruy, P; Baird, J; Bortoluzzi, D; Brandt, N; Fitzsimons, E; Bursi, A; Caleno, M; Cavalleri, A; Cesarini, A; Dolesi, R; Ferroni, V; Cruise, M; Dunbar, N; Ferraioli, L

    2015-01-01

    Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1 mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations. (paper)

  12. A Third-Generation Adaptive Statistical Iterative Reconstruction Technique: Phantom Study of Image Noise, Spatial Resolution, Lesion Detectability, and Dose Reduction Potential.

    Science.gov (United States)

    Euler, André; Solomon, Justin; Marin, Daniele; Nelson, Rendon C; Samei, Ehsan

    2018-06-01

    The purpose of this study was to assess image noise, spatial resolution, lesion detectability, and the dose reduction potential of a proprietary third-generation adaptive statistical iterative reconstruction (ASIR-V) technique. A phantom representing five different body sizes (12-37 cm) and a contrast-detail phantom containing lesions of five low-contrast levels (5-20 HU) and three sizes (2-6 mm) were deployed. Both phantoms were scanned on a 256-MDCT scanner at six different radiation doses (1.25-10 mGy). Images were reconstructed with filtered back projection (FBP), ASIR-V with 50% blending with FBP (ASIR-V 50%), and ASIR-V without blending (ASIR-V 100%). In the first phantom, noise properties were assessed by noise power spectrum analysis. Spatial resolution properties were measured by use of task transfer functions for objects of different contrasts. Noise magnitude, noise texture, and resolution were compared between the three groups. In the second phantom, low-contrast detectability was assessed by nine human readers independently for each condition. The dose reduction potential of ASIR-V was estimated on the basis of a generalized linear statistical regression model. On average, image noise was reduced 37.3% with ASIR-V 50% and 71.5% with ASIR-V 100% compared with FBP. ASIR-V shifted the noise power spectrum toward lower frequencies compared with FBP. The spatial resolution of ASIR-V was equivalent or slightly superior to that of FBP, except for the low-contrast object, which had lower resolution. Lesion detection significantly increased with both ASIR-V levels (p = 0.001), with an estimated radiation dose reduction potential of 15% ± 5% (SD) for ASIR-V 50% and 31% ± 9% for ASIR-V 100%. ASIR-V reduced image noise and improved lesion detection compared with FBP and had potential for radiation dose reduction while preserving low-contrast detectability.

  13. Object localization in handheld thermal images for fireground understanding

    Science.gov (United States)

    Vandecasteele, Florian; Merci, Bart; Jalalvand, Azarakhsh; Verstockt, Steven

    2017-05-01

    Despite the broad application of the handheld thermal imaging cameras in firefighting, its usage is mostly limited to subjective interpretation by the person carrying the device. As remedies to overcome this limitation, object localization and classification mechanisms could assist the fireground understanding and help with the automated localization, characterization and spatio-temporal (spreading) analysis of the fire. An automated understanding of thermal images can enrich the conventional knowledge-based firefighting techniques by providing the information from the data and sensing-driven approaches. In this work, transfer learning is applied on multi-labeling convolutional neural network architectures for object localization and recognition in monocular visual, infrared and multispectral dynamic images. Furthermore, the possibility of analyzing fire scene images is studied and their current limitations are discussed. Finally, the understanding of the room configuration (i.e., objects location) for indoor localization in reduced visibility environments and the linking with Building Information Models (BIM) are investigated.

  14. Wide-band CMOS low-noise amplifier exploiting thermal noise canceling

    NARCIS (Netherlands)

    Bruccoleri, F.; Klumperink, Eric A.M.; Nauta, Bram

    Known elementary wide-band amplifiers suffer from a fundamental tradeoff between noise figure (NF) and source impedance matching, which limits the NF to values typically above 3 dB. Global negative feedback can be used to break this tradeoff, however, at the price of potential instability. In

  15. Image fusion in dual energy computed tomography for detection of various anatomic structures - Effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Jijo, E-mail: jijopaul1980@gmail.com [Department of Diagnostic Radiology, Goethe University Hospital, Theodor-Stern-Kai 7, 60590 Frankfurt am Main (Germany); Department of Biophysics, Goethe University, Max von Laue-Str.1, 60438 Frankfurt am Main (Germany); Bauer, Ralf W. [Department of Diagnostic Radiology, Goethe University Hospital, Theodor-Stern-Kai 7, 60590 Frankfurt am Main (Germany); Maentele, Werner [Department of Biophysics, Goethe University, Max von Laue-Str.1, 60438 Frankfurt am Main (Germany); Vogl, Thomas J. [Department of Diagnostic Radiology, Goethe University Hospital, Theodor-Stern-Kai 7, 60590 Frankfurt am Main (Germany)

    2011-11-15

    Objective: The purpose of this study was to evaluate image fusion in dual energy computed tomography for detecting various anatomic structures based on the effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality. Material and methods: Forty patients underwent a CT neck with dual energy mode (DECT under a Somatom Definition flash Dual Source CT scanner (Siemens, Forchheim, Germany)). Tube voltage: 80-kV and Sn140-kV; tube current: 110 and 290 mA s; collimation-2 x 32 x 0.6 mm. Raw data were reconstructed using a soft convolution kernel (D30f). Fused images were calculated using a spectrum of weighting factors (0.0, 0.3, 0.6 0.8 and 1.0) generating different ratios between the 80- and Sn140-kV images (e.g. factor 0.6 corresponds to 60% of their information from the 80-kV image, and 40% from the Sn140-kV image). CT values and SNRs measured in the ascending aorta, thyroid gland, fat, muscle, CSF, spinal cord, bone marrow and brain. In addition, CNR values calculated for aorta, thyroid, muscle and brain. Subjective image quality evaluated using a 5-point grading scale. Results compared using paired t-tests and nonparametric-paired Wilcoxon-Wilcox-test. Results: Statistically significant increases in mean CT values noted in anatomic structures when increasing weighting factors used (all P {<=} 0.001). For example, mean CT values derived from the contrast enhanced aorta were 149.2 {+-} 12.8 Hounsfield Units (HU), 204.8 {+-} 14.4 HU, 267.5 {+-} 18.6 HU, 311.9 {+-} 22.3 HU, 347.3 {+-} 24.7 HU, when the weighting factors 0.0, 0.3, 0.6, 0.8 and 1.0 were used. The highest SNR and CNR values were found in materials when the weighting factor 0.6 used. The difference CNR between the weighting factors 0.6 and 0.3 was statistically significant in the contrast enhanced aorta and thyroid gland (P = 0.012 and P = 0.016, respectively). Visual image assessment for image quality showed the highest score for the data reconstructed using the

  16. Image fusion in dual energy computed tomography for detection of various anatomic structures - Effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality

    International Nuclear Information System (INIS)

    Paul, Jijo; Bauer, Ralf W.; Maentele, Werner; Vogl, Thomas J.

    2011-01-01

    Objective: The purpose of this study was to evaluate image fusion in dual energy computed tomography for detecting various anatomic structures based on the effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality. Material and methods: Forty patients underwent a CT neck with dual energy mode (DECT under a Somatom Definition flash Dual Source CT scanner (Siemens, Forchheim, Germany)). Tube voltage: 80-kV and Sn140-kV; tube current: 110 and 290 mA s; collimation-2 x 32 x 0.6 mm. Raw data were reconstructed using a soft convolution kernel (D30f). Fused images were calculated using a spectrum of weighting factors (0.0, 0.3, 0.6 0.8 and 1.0) generating different ratios between the 80- and Sn140-kV images (e.g. factor 0.6 corresponds to 60% of their information from the 80-kV image, and 40% from the Sn140-kV image). CT values and SNRs measured in the ascending aorta, thyroid gland, fat, muscle, CSF, spinal cord, bone marrow and brain. In addition, CNR values calculated for aorta, thyroid, muscle and brain. Subjective image quality evaluated using a 5-point grading scale. Results compared using paired t-tests and nonparametric-paired Wilcoxon-Wilcox-test. Results: Statistically significant increases in mean CT values noted in anatomic structures when increasing weighting factors used (all P ≤ 0.001). For example, mean CT values derived from the contrast enhanced aorta were 149.2 ± 12.8 Hounsfield Units (HU), 204.8 ± 14.4 HU, 267.5 ± 18.6 HU, 311.9 ± 22.3 HU, 347.3 ± 24.7 HU, when the weighting factors 0.0, 0.3, 0.6, 0.8 and 1.0 were used. The highest SNR and CNR values were found in materials when the weighting factor 0.6 used. The difference CNR between the weighting factors 0.6 and 0.3 was statistically significant in the contrast enhanced aorta and thyroid gland (P = 0.012 and P = 0.016, respectively). Visual image assessment for image quality showed the highest score for the data reconstructed using the weighting factor 0

  17. Imaging, manipulation and flux noise of single Abrikosov vortices in YBa2Cu3O7-δ dc SQUIDs

    International Nuclear Information System (INIS)

    Bailer, Matthias

    2013-01-01

    The thesis deals with the imaging and investigation of single Abrikosov vortices in grain boundary dc SQUIDs1 from the high-temperature superconductor YBa 2 Cu 3 O 7-δ . The low temperature scanning electron microscopy (LTSEM) was used for the measurements, which makes a local, spatially resolved investigation of the electrical properties of materials at low temperatures possible. The advantage over other flux quantum imaging methods is the facility to determine the low-frequency flux noise in the SQUID in the process. Special SQUID designs were created, which allow a reproducible cooling of single flux quanta. Electrical transport and noise measurements were carried out to precharacterise the SQUIDs. Within the scope of the thesis it was the first time that antivortices were imaged with the LTSEM. The possibilities of a manipulation of flux quanta (with the electron beam) were investigated and illustrated. By the averaged measurement of the waveform of a single vortex, linescans with unprecedented resolution could be obtained. This allowed the outstanding comparison of the measured, virtual vortex displacement with various theoretically determined waveforms. The experiments to flux noise provided new insights into the noise behaviour of single flux quanta, which exhibit the typical single fluctuators random telegraph signal, and enabled the analysis of the associated hopping processes. Thus concrete values of the spectral noise power density S r ∼ 196 nm 2 /root(Hz) - 0,28 μm 2 /root(Hz) radially to the SQUID hole could be determined by different, pinned vortices. An influence of the hopping behaviour and therefore of the flux noise succeeded by varying an applied magnetic field. Through tilting the potential course of a vortex, the course of the pinning potential by different hopping processes could be reconstructed using stochastic analysis of the time trace data. With the thesis could be shown convincingly that the vortex imaging method of the LTSEM in

  18. Image processing for drift compensation in fluorescence microscopy

    DEFF Research Database (Denmark)

    Petersen, Steffen; Thiagarajan, Viruthachalam; Coutinho, Isabel

    2013-01-01

    Fluorescence microscopy is characterized by low background noise, thus a fluorescent object appears as an area of high signal/noise. Thermal gradients may result in apparent motion of the object, leading to a blurred image. Here, we have developed an image processing methodology that may remove....../reduce blur significantly for any type of microscopy. A total of ~100 images were acquired with a pixel size of 30 nm. The acquisition time for each image was approximately 1second. We can quantity the drift in X and Y using the sub pixel accuracy computed centroid location of an image object in each frame....... We can measure drifts down to approximately 10 nm in size and a drift-compensated image can therefore be reconstructed on a grid of the same size using the “Shift and Add” approach leading to an image of identical size asthe individual image. We have also reconstructed the image using a 3 fold larger...

  19. A new and efficient transient noise analysis technique for simulation of CCD image sensors or particle detectors

    International Nuclear Information System (INIS)

    Bolcato, P.; Jarron, P.; Poujois, R.

    1993-01-01

    CCD image sensors or switched capacitor circuits used for particle detectors have a certain noise level affecting the resolution of the detector. A new noise simulation technique for these devices is presented that has been implemented in the circuit simulator ELDO. The approach is particularly useful for noise simulation in analog sampling circuits. Comparison between simulations and experimental results has been made and is shown for a 1.5 μ CMOS current mode amplifier designed for high-rate particle detectors. (R.P.) 5 refs., 7 figs

  20. Resolution and robustness to noise of the sensitivity-based method for microwave imaging with data acquired on cylindrical surfaces

    International Nuclear Information System (INIS)

    Zhang, Yifan; Tu, Sheng; Amineh, Reza K; Nikolova, Natalia K

    2012-01-01

    The spatial resolution limit of a Jacobian-based microwave imaging algorithm and its robustness to noise are evaluated. The focus here is on tomographic systems where the wideband data are acquired with a vertically scanned circular sensor array and at each scanning step a 2D image is reconstructed in the plane of the sensor array. The theoretical resolution is obtained as one-half of the maximum-frequency wavelength with far-zone data and about two-thirds of the array radius with near-zone data. Validation examples are given using analytical electromagnetic models. The algorithm is shown to be robust to noise when the response data are corrupted by Gaussian white noise. (paper)

  1. Visual quality analysis for images degraded by different types of noise

    Science.gov (United States)

    Ponomarenko, Nikolay N.; Lukin, Vladimir V.; Ieremeyev, Oleg I.; Egiazarian, Karen O.; Astola, Jaakko T.

    2013-02-01

    Modern visual quality metrics take into account different peculiarities of the Human Visual System (HVS). One of them is described by the Weber-Fechner law and deals with the different sensitivity to distortions in image fragments with different local mean values (intensity, brightness). We analyze how this property can be incorporated into a metric PSNRHVS- M. It is shown that some improvement of its performance can be provided. Then, visual quality of color images corrupted by three types of i.i.d. noise (pure additive, pure multiplicative, and signal dependent, Poisson) is analyzed. Experiments with a group of observers are carried out for distorted color images created on the basis of TID2008 database. Several modern HVS-metrics are considered. It is shown that even the best metrics are unable to assess visual quality of distorted images adequately enough. The reasons for this deal with the observer's attention to certain objects in the test images, i.e., with semantic aspects of vision, which are worth taking into account in design of HVS-metrics.

  2. Evaluation of the AN/SAY-1 Thermal Imaging Sensor System

    National Research Council Canada - National Science Library

    Smith, John G; Middlebrook, Christopher T

    2002-01-01

    The AN/SAY-1 Thermal Imaging Sensor System "TISS" was developed to provide surface ships with a day/night imaging capability to detect low radar reflective, small cross-sectional area targets such as floating mines...

  3. A study on optimal scan conditions of big bore multi-slice computed tomography based on radiation dose and image noise

    International Nuclear Information System (INIS)

    Lee, J. S.; Ye, S. J.; Kim, E. H.

    2011-01-01

    The newly introduced Big Bore computed tomography (CT) has a possibility to increase the tube current product scan time (mA s) for compensation of image degradation due to larger gentry opening without sound guideline. The objective of this paper is to derive optimal scan conditions for Big Bore CT scanner, mainly relating to the dose of diagnostic CT. The weighted CT dose index (CTDI w ) was estimated at five typical protocols, such as head and neck, brain, paediatric, chest and abdomen. Noises were analysed in a circle of 1 or 2 cm of diameter in CT image slice. The results showed that measured CTDI w values generally follow the theoretical rule at all scanning conditions of every protocol. Although image noises decrease with increment of mA s, analysed image noises do follow the theoretical rule, but only in specific protocols. This phenomenon is presumed to result from the photon energy spectra arriving at the detection system of the Big Bore scanner. (authors)

  4. High Temperature Fiberoptic Thermal Imaging System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase 1 program will fabricate and demonstrate a small diameter single fiber endoscope that can perform high temperature thermal imaging in a jet engine...

  5. Stream temperature estimated in situ from thermal-infrared images: best estimate and uncertainty

    International Nuclear Information System (INIS)

    Iezzi, F; Todisco, M T

    2015-01-01

    The paper aims to show a technique to estimate in situ the stream temperature from thermal-infrared images deepening its best estimate and uncertainty. Stream temperature is an important indicator of water quality and nowadays its assessment is important particularly for thermal pollution monitoring in water bodies. Stream temperature changes are especially due to the anthropogenic heat input from urban wastewater and from water used as a coolant by power plants and industrial manufacturers. The stream temperatures assessment using ordinary techniques (e.g. appropriate thermometers) is limited by sparse sampling in space due to a spatial discretization necessarily punctual. Latest and most advanced techniques assess the stream temperature using thermal-infrared remote sensing based on thermal imagers placed usually on aircrafts or using satellite images. These techniques assess only the surface water temperature and they are suitable to detect the temperature of vast water bodies but do not allow a detailed and precise surface water temperature assessment in limited areas of the water body. The technique shown in this research is based on the assessment of thermal-infrared images obtained in situ via portable thermal imager. As in all thermographic techniques, also in this technique, it is possible to estimate only the surface water temperature. A stream with the presence of a discharge of urban wastewater is proposed as case study to validate the technique and to show its application limits. Since the technique analyzes limited areas in extension of the water body, it allows a detailed and precise assessment of the water temperature. In general, the punctual and average stream temperatures are respectively uncorrected and corrected. An appropriate statistical method that minimizes the errors in the average stream temperature is proposed. The correct measurement of this temperature through the assessment of thermal- infrared images obtained in situ via portable

  6. Noise Reduction Techniques

    Science.gov (United States)

    Hallas, Tony

    There are two distinct kinds of noise - structural and color. Each requires a specific method of attack to minimize. The great challenge is to reduce the noise without reducing the faint and delicate detail in the image. My most-used and favorite noise suppression is found in Photoshop CS 5 Camera Raw. If I cannot get the desired results with the first choice, I will use Noise Ninja, which has certain advantages in some situations that we will cover.

  7. Exploring the use of thermal infrared imaging in human stress research.

    Directory of Open Access Journals (Sweden)

    Veronika Engert

    Full Text Available High resolution thermal infrared imaging is a pioneering method giving indices of sympathetic activity via the contact-free recording of facial tissues (thermal imprints. Compared to established stress markers, the great advantage of this method is its non-invasiveness. The goal of our study was to pilot the use of thermal infrared imaging in the classical setting of human stress research. Thermal imprints were compared to established stress markers (heart rate, heart rate variability, finger temperature, alpha-amylase and cortisol in 15 participants undergoing anticipation, stress and recovery phases of two laboratory stress tests, the Cold Pressor Test and the Trier Social Stress Test. The majority of the thermal imprints proved to be change-sensitive in both tests. While correlations between the thermal imprints and established stress markers were mostly non-significant, the thermal imprints (but not the established stress makers did correlate with stress-induced mood changes. Multivariate pattern analysis revealed that in contrast to the established stress markers the thermal imprints could not disambiguate anticipation, stress and recovery phases of both tests. Overall, these results suggest that thermal infrared imaging is a valuable method for the estimation of sympathetic activity in the stress laboratory setting. The use of this non-invasive method may be particularly beneficial for covert recordings, in the study of special populations showing difficulties in complying with the standard instruments of data collection and in the domain of psychophysiological covariance research. Meanwhile, the established stress markers seem to be superior when it comes to the characterization of complex physiological states during the different phases of the stress cycle.

  8. Signal-to-noise analysis of a birefringent spectral zooming imaging spectrometer

    Science.gov (United States)

    Li, Jie; Zhang, Xiaotong; Wu, Haiying; Qi, Chun

    2018-05-01

    Study of signal-to-noise ratio (SNR) of a novel spectral zooming imaging spectrometer (SZIS) based on two identical Wollaston prisms is conducted. According to the theory of radiometry and Fourier transform spectroscopy, we deduce the theoretical equations of SNR of SZIS in spectral domain with consideration of the incident wavelength and the adjustable spectral resolution. An example calculation of SNR of SZIS is performed over 400-1000 nm. The calculation results indicate that SNR with different spectral resolutions of SZIS can be optionally selected by changing the spacing between the two identical Wollaston prisms. This will provide theoretical basis for the design, development and engineering of the developed imaging spectrometer for broad spectrum and SNR requirements.

  9. Noise Simulation of Continuous-Time ΣΔ Modulators

    International Nuclear Information System (INIS)

    Arias, J.; Quintanilla, L.; Bisbal, D.; San Pablo, J.; Enriquez, L.; Vicente, J.; Barbolla, J.

    2005-01-01

    In this work, an approach for the simulation of the effect of noise sources in the performance of continuous-time ΔΣ modulators is presented. Electrical noise including thermal noise, 1/f noise and clock jitter are included in a simulation program and their impact on the system performance is analyzed

  10. Detection of Thermal Erosion Gullies from High-Resolution Images Using Deep Learning

    Science.gov (United States)

    Huang, L.; Liu, L.; Jiang, L.; Zhang, T.; Sun, Y.

    2017-12-01

    Thermal erosion gullies, one type of thermokarst landforms, develop due to thawing of ice-rich permafrost. Mapping the location and extent of thermal erosion gullies can help understand the spatial distribution of thermokarst landforms and their temporal evolution. Remote sensing images provide an effective way for mapping thermokarst landforms, especially thermokarst lakes. However, thermal erosion gullies are challenging to map from remote sensing images due to their small sizes and significant variations in geometric/radiometric properties. It is feasible to manually identify these features, as a few previous studies have carried out. However manual methods are labor-intensive, therefore, cannot be used for a large study area. In this work, we conduct automatic mapping of thermal erosion gullies from high-resolution images by using Deep Learning. Our study area is located in Eboling Mountain (Qinghai, China). Within a 6 km2 peatland area underlain by ice-rich permafrost, at least 20 thermal erosional gullies are well developed. The image used is a 15-cm-resolution Digital Orthophoto Map (DOM) generated in July 2016. First, we extracted 14 gully patches and ten non-gully patches as training data. And we performed image augmentation. Next, we fine-tuned the pre-trained model of DeepLab, a deep-learning algorithm for semantic image segmentation based on Deep Convolutional Neural Networks. Then, we performed inference on the whole DOM and obtained intermediate results in forms of polygons for all identified gullies. At last, we removed misidentified polygons based on a few pre-set criteria on the size and shape of each polygon. Our final results include 42 polygons. Validated against field measurements using GPS, most of the gullies are detected correctly. There are 20 false detections due to the small number and low quality of training images. We also found three new gullies that missed in the field observations. This study shows that (1) despite a challenging

  11. Design and Characterization of Low-noise Dewar for High-sensitivity SQUID Operation

    International Nuclear Information System (INIS)

    Yu, K. K.; Lee, Y. H.; Kim, K.; Kwon, H.; Kim, J. M.

    2010-01-01

    We have fabricated the low noise liquid helium(LHe) dewar with a different shape of thermal shield to apply the 64-channel SQUID(Superconducting Quantum Interference Device) gradiometer. The first shape of thermal shield was made of an aluminum plate with a wide width of 100 mm slit and the other shape was modified with a narrow width of 20 mm slit. The two types of dewars were estimated by comparing the thermal noise and the signal-to-noise ratio(SNR) of magnetocardiography(MCG) using the 1st order SQUID gradiometer system cooled each dewar. The white noise was different as a point of the dewar. The noise was increased as close as the edge of dewar, and also increased at the thermal shield with the more wide width slit. The white noise of the dewar with thermal shield of 100 mm slit was 6.5 fT/Hz 1/2 at the center of dewar and 25 fT/Hz 1/2 at the edge, and the white noise of the other one was 3.5 - 7 fT/Hz 1/2 . We measured the MCG using 64-channel SQUID gradiometer cooled at each LHe dewar and compared the SNR of MCG signal. The SNR was improved of 10 times at the LHe dewar with a modified thermal shield.

  12. Performance of a thermal neutron radiographic system using imaging plates

    International Nuclear Information System (INIS)

    Silvani, Maria Ines; Almeida, Gevaldo L. de; Furieri, Rosanne; Lopes, Ricardo T.

    2009-01-01

    A performance evaluation of a neutron radiographic system equipped with a thermal neutron sensitive imaging plate has been undertaken. It includes the assessment of spatial resolution, linearity, dynamic range and the response to exposure time, as well as a comparison of these parameters with the equivalent ones for neutron radiography employing conventional films and a gadolinium foil as converter. The evaluation and comparison between the radiographic systems have been performed at the Instituto de Engenharia Nuclear - CNEN, using the Argonauta Reactor as source of thermal neutrons and a commercially available imaging plate reader. (author)

  13. Diagnosis of the three-phase induction motor using thermal imaging

    Science.gov (United States)

    Glowacz, Adam; Glowacz, Zygfryd

    2017-03-01

    Three-phase induction motors are used in the industry commonly for example woodworking machines, blowers, pumps, conveyors, elevators, compressors, mining industry, automotive industry, chemical industry and railway applications. Diagnosis of faults is essential for proper maintenance. Faults may damage a motor and damaged motors generate economic losses caused by breakdowns in production lines. In this paper the authors develop fault diagnostic techniques of the three-phase induction motor. The described techniques are based on the analysis of thermal images of three-phase induction motor. The authors analyse thermal images of 3 states of the three-phase induction motor: healthy three-phase induction motor, three-phase induction motor with 2 broken bars, three-phase induction motor with faulty ring of squirrel-cage. In this paper the authors develop an original method of the feature extraction of thermal images MoASoID (Method of Areas Selection of Image Differences). This method compares many training sets together and it selects the areas with the biggest changes for the recognition process. Feature vectors are obtained with the use of mentioned MoASoID and image histogram. Next 3 methods of classification are used: NN (the Nearest Neighbour classifier), K-means, BNN (the back-propagation neural network). The described fault diagnostic techniques are useful for protection of three-phase induction motor and other types of rotating electrical motors such as: DC motors, generators, synchronous motors.

  14. Nuisance levels of noise effects radiologists' performance

    Science.gov (United States)

    McEntee, Mark F.; Coffey, Amina; Ryan, John; O'Beirne, Aaron; Toomey, Rachel; Evanoff, Micheal; Manning, David; Brennan, Patrick C.

    2010-02-01

    This study aimed to measure the sound levels in Irish x-ray departments. The study then established whether these levels of noise have an impact on radiologists performance Noise levels were recorded 10 times within each of 14 environments in 4 hospitals, 11 of which were locations where radiologic images are judged. Thirty chest images were then presented to 26 senior radiologists, who were asked to detect up to three nodular lesions within 30 posteroanterior chest x-ray images in the absence and presence of noise at amplitude demonstrated in the clinical environment. The results demonstrated that noise amplitudes rarely exceeded that encountered with normal conversation with the maximum mean value for an image-viewing environment being 56.1 dB. This level of noise had no impact on the ability of radiologists to identify chest lesions with figure of merits of 0.68, 0.69, and 0.68 with noise and 0.65, 0.68, and 0.67 without noise for chest radiologists, non-chest radiologists, and all radiologists, respectively. the difference in their performance using the DBM MRMC method was significantly better with noise than in the absence of noise at the 90% confidence interval (p=0.077). Further studies are required to establish whether other aspects of diagnosis are impaired such as recall and attention and the effects of more unexpected noise on performance.

  15. Image noise-based dose adaptation in dynamic volume CT of the heart: dose and image quality optimisation in comparison with BMI-based dose adaptation

    Energy Technology Data Exchange (ETDEWEB)

    Odedra, Devang [Queen' s University, School of Medicine, Kingston, ON (Canada); Blobel, Joerg [Toshiba Medical Systems Europe BV, Zoetermeer (Netherlands); University of Toronto, Division of Cardiothoracic Imaging, Department of Medical Imaging, Toronto General Hospital, Toronto, ON (Canada); AlHumayyd, Saad; Durand, Miranda; Jimenez-Juan, Laura; Paul, Narinder [University of Toronto, Division of Cardiothoracic Imaging, Department of Medical Imaging, Toronto General Hospital, Toronto, ON (Canada)

    2014-01-15

    To compare the image quality and radiation dose using image-noise (IN)-based determination of X-ray tube settings compared with a body mass index (BMI)-based protocol during CT coronary angiography (CTCA). Two hundred consecutive patients referred for CTCA to our institution were divided into two groups: BMI-based, 100 patients had CTCA with the X-ray tube current adjusted to the patient's BMI while maintaining a fixed tube potential of 120 kV; IN-based, 100 patients underwent imaging with the X-ray tube current and voltage adjusted to the IN measured within the mid-left ventricle on a pre-acquisition trans-axial image. Two independent cardiac radiologists performed blinded image quality assessment with quantification of the IN and signal-to-noise ratio (SNR) from the mid-LV and qualitative assessment using a three-point score. Radiation dose (CTDI and DLP) was recorded from the console. Results showed: IN (HU): BMI-based, 30.1 ± 9.9; IN-based, 33.1 ± 6.7; 32 % variation reduction (P = 0.001); SNR: BMI-based, 18.6 ± 7.1; IN-based, 15.4 ± 3.7; 48 % variation reduction (P < 0.0001). Visual scores: BMI-based, 2.3 ± 0.6; IN-based, 2.2 ± 0.5 (P = 0.54). Radiation dose: CTDI (mGy), BMI-based, 22.68 ± 8.9; IN-based, 17.16 ± 7.6; 24.3 % reduction (P < 0.001); DLP (mGy.cm), BMI-based, 309.3 ± 127.5; IN-based, 230.6 ± 105.5; 25.4 % reduction (P < 0.001). Image-noise-based stratification of X-ray tube parameters for CTCA results in 32 % improvement in image quality and 25 % reduction in radiation dose compared with a BMI-based protocol. (orig.)

  16. Automatic detection of diseased tomato plants using thermal and stereo visible light images.

    Directory of Open Access Journals (Sweden)

    Shan-e-Ahmed Raza

    Full Text Available Accurate and timely detection of plant diseases can help mitigate the worldwide losses experienced by the horticulture and agriculture industries each year. Thermal imaging provides a fast and non-destructive way of scanning plants for diseased regions and has been used by various researchers to study the effect of disease on the thermal profile of a plant. However, thermal image of a plant affected by disease has been known to be affected by environmental conditions which include leaf angles and depth of the canopy areas accessible to the thermal imaging camera. In this paper, we combine thermal and visible light image data with depth information and develop a machine learning system to remotely detect plants infected with the tomato powdery mildew fungus Oidium neolycopersici. We extract a novel feature set from the image data using local and global statistics and show that by combining these with the depth information, we can considerably improve the accuracy of detection of the diseased plants. In addition, we show that our novel feature set is capable of identifying plants which were not originally inoculated with the fungus at the start of the experiment but which subsequently developed disease through natural transmission.

  17. Measurement of luminance noise and chromaticity noise of LCDs with a colorimeter and a color camera

    Science.gov (United States)

    Roehrig, H.; Dallas, W. J.; Krupinski, E. A.; Redford, Gary R.

    2007-09-01

    This communication focuses on physical evaluation of image quality of displays for applications in medical imaging. In particular we were interested in luminance noise as well as chromaticity noise of LCDs. Luminance noise has been encountered in the study of monochrome LCDs for some time, but chromaticity noise is a new type of noise which has been encountered first when monochrome and color LCDs were compared in an ROC study. In this present study one color and one monochrome 3 M-pixel LCDs were studied. Both were DICOM calibrated with equal dynamic range. We used a Konica Minolta Chroma Meter CS-200 as well as a Foveon color camera to estimate luminance and chrominance variations of the displays. We also used a simulation experiment to estimate luminance noise. The measurements with the colorimeter were consistent. The measurements with the Foveon color camera were very preliminary as color cameras had never been used for image quality measurements. However they were extremely promising. The measurements with the colorimeter and the simulation results showed that the luminance and chromaticity noise of the color LCD were larger than that of the monochrome LCD. Under the condition that an adequate calibration method and image QA/QC program for color displays are available, we expect color LCDs may be ready for radiology in very near future.

  18. Particle image velocimetry correlation signal-to-noise ratio metrics and measurement uncertainty quantification

    International Nuclear Information System (INIS)

    Xue, Zhenyu; Charonko, John J; Vlachos, Pavlos P

    2014-01-01

    In particle image velocimetry (PIV) the measurement signal is contained in the recorded intensity of the particle image pattern superimposed on a variety of noise sources. The signal-to-noise-ratio (SNR) strength governs the resulting PIV cross correlation and ultimately the accuracy and uncertainty of the resulting PIV measurement. Hence we posit that correlation SNR metrics calculated from the correlation plane can be used to quantify the quality of the correlation and the resulting uncertainty of an individual measurement. In this paper we extend the original work by Charonko and Vlachos and present a framework for evaluating the correlation SNR using a set of different metrics, which in turn are used to develop models for uncertainty estimation. Several corrections have been applied in this work. The SNR metrics and corresponding models presented herein are expanded to be applicable to both standard and filtered correlations by applying a subtraction of the minimum correlation value to remove the effect of the background image noise. In addition, the notion of a ‘valid’ measurement is redefined with respect to the correlation peak width in order to be consistent with uncertainty quantification principles and distinct from an ‘outlier’ measurement. Finally the type and significance of the error distribution function is investigated. These advancements lead to more robust and reliable uncertainty estimation models compared with the original work by Charonko and Vlachos. The models are tested against both synthetic benchmark data as well as experimental measurements. In this work, U 68.5 uncertainties are estimated at the 68.5% confidence level while U 95 uncertainties are estimated at 95% confidence level. For all cases the resulting calculated coverage factors approximate the expected theoretical confidence intervals, thus demonstrating the applicability of these new models for estimation of uncertainty for individual PIV measurements. (paper)

  19. Particle image velocimetry correlation signal-to-noise ratio metrics and measurement uncertainty quantification

    Science.gov (United States)

    Xue, Zhenyu; Charonko, John J.; Vlachos, Pavlos P.

    2014-11-01

    In particle image velocimetry (PIV) the measurement signal is contained in the recorded intensity of the particle image pattern superimposed on a variety of noise sources. The signal-to-noise-ratio (SNR) strength governs the resulting PIV cross correlation and ultimately the accuracy and uncertainty of the resulting PIV measurement. Hence we posit that correlation SNR metrics calculated from the correlation plane can be used to quantify the quality of the correlation and the resulting uncertainty of an individual measurement. In this paper we extend the original work by Charonko and Vlachos and present a framework for evaluating the correlation SNR using a set of different metrics, which in turn are used to develop models for uncertainty estimation. Several corrections have been applied in this work. The SNR metrics and corresponding models presented herein are expanded to be applicable to both standard and filtered correlations by applying a subtraction of the minimum correlation value to remove the effect of the background image noise. In addition, the notion of a ‘valid’ measurement is redefined with respect to the correlation peak width in order to be consistent with uncertainty quantification principles and distinct from an ‘outlier’ measurement. Finally the type and significance of the error distribution function is investigated. These advancements lead to more robust and reliable uncertainty estimation models compared with the original work by Charonko and Vlachos. The models are tested against both synthetic benchmark data as well as experimental measurements. In this work, {{U}68.5} uncertainties are estimated at the 68.5% confidence level while {{U}95} uncertainties are estimated at 95% confidence level. For all cases the resulting calculated coverage factors approximate the expected theoretical confidence intervals, thus demonstrating the applicability of these new models for estimation of uncertainty for individual PIV measurements.

  20. Dual-energy computed tomography in patients with cutaneous malignant melanoma: Comparison of noise-optimized and traditional virtual monoenergetic imaging.

    Science.gov (United States)

    Martin, Simon S; Wichmann, Julian L; Weyer, Hendrik; Albrecht, Moritz H; D'Angelo, Tommaso; Leithner, Doris; Lenga, Lukas; Booz, Christian; Scholtz, Jan-Erik; Bodelle, Boris; Vogl, Thomas J; Hammerstingl, Renate

    2017-10-01

    The aim of this study was to investigate the impact of noise-optimized virtual monoenergetic imaging (VMI+) reconstructions on quantitative and qualitative image parameters in patients with cutaneous malignant melanoma at thoracoabdominal dual-energy computed tomography (DECT). Seventy-six patients (48 men; 66.6±13.8years) with metastatic cutaneous malignant melanoma underwent DECT of the thorax and abdomen. Images were post-processed with standard linear blending (M_0.6), traditional virtual monoenergetic (VMI), and VMI+ technique. VMI and VMI+ images were reconstructed in 10-keV intervals from 40 to 100keV. Attenuation measurements were performed in cutaneous melanoma lesions, as well as in regional lymph node, subcutaneous and in-transit metastases to calculate objective signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Five-point scales were used to evaluate overall image quality and lesion delineation by three radiologists with different levels of experience. Objective indices SNR and CNR were highest at 40-keV VMI+ series (5.6±2.6 and 12.4±3.4), significantly superior to all other reconstructions (all Ptraditional VMI in patients with cutaneous malignant melanoma at thoracoabdominal DECT. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Detecting thermal phase transitions in corneal stroma by fluorescence micro-imaging analysis

    Science.gov (United States)

    Matteini, P.; Rossi, F.; Ratto, F.; Bruno, I.; Nesi, P.; Pini, R.

    2008-02-01

    Thermal modifications induced in corneal stroma were investigated by the use of fluorescence microscopy. Freshly extracted porcine corneas were immersed for 5 minutes in a water bath at temperatures in the 35-90°C range and stored in formalin. The samples were then sliced in 200-μm-thick transversal sections and analyzed under a stereomicroscope to assess corneal shrinkage. Fluorescence images of the thermally treated corneal samples were acquired using a slow-scan cooled CCD camera, after staining the slices with Indocyanine Green (ICG) fluorescent dye which allowed to detect fluorescence signal from the whole tissue. All measurements were performed using an inverted epifluorescence microscope equipped with a mercury lamp. The thermally-induced modifications to the corneal specimens were evaluated by studying the grey level distribution in the fluorescence images. For each acquired image, Discrete Fourier Transform (DFT) and entropy analyses were performed. The spatial distribution of DFT absolute value indicated the spatial orientation of the lamellar planes, while entropy was used to study the image texture, correlated to the stromal structural transitions. As a result, it was possible to indicate a temperature threshold value (62°C) for high thermal damage, resulting in a disorganization of the lamellar planes and in full agreement with the measured temperature for corneal shrinkage onset. Analysis of the image entropy evidenced five strong modifications in stromal architecture at temperatures of ~45°C, 53°C, 57°C, 66°C, 75°C. The proposed procedure proved to be an effective micro-imaging method capable of detecting subtle changes in corneal tissue subjected to thermal treatment.

  2. Circumvention of radiation-induced noise in CCD and CID imagers

    International Nuclear Information System (INIS)

    Yates, G.J.; Turko, B.T.

    1989-01-01

    Measurements of radiation sensitivity for interline transfer charge-injection devices (CIDs) from irradiation with high-energy photons ( 60 Co gammas and 3- to 5-MeV end-point Bremsstrahlung) and 14 MeV neutrons are presented to establish imager susceptibility in such environments. Results from electronic clearing techniques designed for quick (∼300μs for the CCDs and ∼10μs for CIDs) removal (or dumping) of radiation-induced charge from prompt sources are discussed. Application of the techniques coupled with long (microsecond to millisecond) persistence radiation-to-light converters for image retention are described. Typical data illustrating the effectiveness of charge clearing in removal of radiation noise are included for nanosecond duration pulsed x-ray/γ-ray doses (50 millirad to 5-rad range) and microsecond duration neutron fluences approaching 10 8 n/cm 2

  3. Electron dose dependence of signal-to-noise ratio, atom contrast and resolution in transmission electron microscope images

    International Nuclear Information System (INIS)

    Lee, Z.; Rose, H.; Lehtinen, O.; Biskupek, J.; Kaiser, U.

    2014-01-01

    In order to achieve the highest resolution in aberration-corrected (AC) high-resolution transmission electron microscopy (HRTEM) images, high electron doses are required which only a few samples can withstand. In this paper we perform dose-dependent AC-HRTEM image calculations, and study the dependence of the signal-to-noise ratio, atom contrast and resolution on electron dose and sampling. We introduce dose-dependent contrast, which can be used to evaluate the visibility of objects under different dose conditions. Based on our calculations, we determine optimum samplings for high and low electron dose imaging conditions. - Highlights: • The definition of dose-dependent atom contrast is introduced. • The dependence of the signal-to-noise ratio, atom contrast and specimen resolution on electron dose and sampling is explored. • The optimum sampling can be determined according to different dose conditions

  4. Noise and specific detectivity measurements on high-temperature superconducting transition-edge bolometers

    International Nuclear Information System (INIS)

    Black, R.D.; Mogro-campero, A.; Turner, L.G.

    1990-01-01

    The effects of thermal fluctuation noise in thermal detectors can be lessened by reducing heat capacity and thermal conductance. An attempt to accomplish this with the YBa2Cu3O(7-x) (YBCO) bolometer by making YBCO resistors on thermally isolated membranes is reported. The spectral power of the electrical noise of YBCO films on SrTiO3, bulk silicon with a buffer layer, and in thin dielectric membranes is measured. It is found that 1/f noise predominates in polycrystalline YBCO films on silicon-based substrates. Films on SrTiO3 with good electrical properties are dominated by thermal fluctuation noise, just as in the case of low-temperature superconductors. The implications of these findings for bolometer are addressed. The specific detectivity of a bolometric pixel made on bulk SrTiO3 is reported. 14 refs

  5. High-performance ferroelectric and magnetoresistive materials for next-generation thermal detector arrays

    Science.gov (United States)

    Todd, Michael A.; Donohue, Paul P.; Watton, Rex; Williams, Dennis J.; Anthony, Carl J.; Blamire, Mark G.

    2002-12-01

    This paper discusses the potential thermal imaging performance achievable from thermal detector arrays and concludes that the current generation of thin-film ferroelectric and resistance bolometer based detector arrays are limited by the detector materials used. It is proposed that the next generation of large uncooled focal plane arrays will need to look towards higher performance detector materials - particularly if they aim to approach the fundamental performance limits and compete with cooled photon detector arrays. Two examples of bolometer thin-film materials are described that achieve high performance from operating around phase transitions. The material Lead Scandium Tantalate (PST) has a paraelectric-to-ferroelectric phase transition around room temperature and is used with an applied field in the dielectric bolometer mode for thermal imaging. PST films grown by sputtering and liquid-source CVD have shown merit figures for thermal imaging a factor of 2 to 3 times higher than PZT-based pyroelectric thin films. The material Lanthanum Calcium Manganite (LCMO) has a paramagnetic to ferromagnetic phase transition around -20oC. This paper describes recent measurements of TCR and 1/f noise in pulsed laser-deposited LCMO films on Neodymium Gallate substrates. These results show that LCMO not only has high TCR's - up to 30%/K - but also low 1/f excess noise, with bolometer merit figures at least an order of magnitude higher than Vanadium Oxide, making it ideal for the next generation of microbolometer arrays. These high performance properties come at the expense of processing complexities and novel device designs will need to be introduced to realize the potential of these materials in the next generation of thermal detectors.

  6. Automatic Cloud and Shadow Detection in Optical Satellite Imagery Without Using Thermal Bands—Application to Suomi NPP VIIRS Images over Fennoscandia

    Directory of Open Access Journals (Sweden)

    Eija Parmes

    2017-08-01

    Full Text Available In land monitoring applications, clouds and shadows are considered noise that should be removed as automatically and quickly as possible, before further analysis. This paper presents a method to detect clouds and shadows in Suomi NPP satellite’s VIIRS (Visible Infrared Imaging Radiometer Suite satellite images. The proposed cloud and shadow detection method has two distinct features when compared to many other methods. First, the method does not use the thermal bands and can thus be applied to other sensors which do not contain thermal channels, such as Sentinel-2 data. Secondly, the method uses the ratio between blue and green reflectance to detect shadows. Seven hundred and forty-seven VIIRS images over Fennoscandia from August 2014 to April 2016 were processed to train and develop the method. Twenty four points from every tenth of the images were used in accuracy assessment. These 1752 points were interpreted visually to cloud, cloud shadow and clear classes, then compared to the output of the cloud and shadow detection. The comparison on VIIRS images showed 94.2% correct detection rates and 11.1% false alarms for clouds, and respectively 36.1% and 82.7% for shadows. The results on cloud detection were similar to state-of-the-art methods. Shadows showed correctly on the northern edge of the clouds, but many shadows were wrongly assigned to other classes in some cases (e.g., to water class on lake and forest boundary, or with shadows over cloud. This may be due to the low spatial resolution of VIIRS images, where shadows are only a few pixels wide and contain lots of mixed pixels.

  7. Human emotions detection based on a smart-thermal system of thermographic images

    Science.gov (United States)

    Cruz-Albarran, Irving A.; Benitez-Rangel, Juan P.; Osornio-Rios, Roque A.; Morales-Hernandez, Luis A.

    2017-03-01

    This work presents a noninvasive methodology to obtain biomedical thermal imaging which provide relevant information that may assist in the diagnosis of emotions. Biomedical thermal images of the facial expressions of 44 subjects were captured experiencing joy, disgust, anger, fear and sadness. The analysis of these thermograms was carried out through its thermal value not with its intensity value. Regions of interest were obtained through image processing techniques that allow to differentiate between the subject and the background, having only the subject, the centers of each region of interest were obtained in order to get the same region of the face for each subject. Through the thermal analysis a biomarker for each region of interest was obtained, these biomarkers can diagnose when an emotion takes place. Because each subject tends to react differently to the same stimuli, a self-calibration phase is proposed, its function is to have the same thermal trend for each subject in order to make a decision so that the five emotions can be correctly diagnosed through a top-down hierarchical classifier. As a final result, a smart-thermal system that diagnose emotions was obtained and it was tested on twenty-five subjects (625 thermograms). The results of this test were 89.9% successful.

  8. Segmentation techniques for extracting humans from thermal images

    CSIR Research Space (South Africa)

    Dickens, JS

    2011-11-01

    Full Text Available A pedestrian detection system for underground mine vehicles is being developed that requires the segmentation of people from thermal images in underground mine tunnels. A number of thresholding techniques are outlined and their performance on a...

  9. Infrared imaging systems: Design, analysis, modeling, and testing II; Proceedings of the Meeting, Orlando, FL, Apr. 3-5, 1991

    Science.gov (United States)

    Holst, Gerald C.

    Topics addressed include MTF characteristics of a Scophony scene projector, design of an athermalized three-field-of-view infrared sensor, a 3D analysis framework and measurement methodology for imaging system noise, effects of phasing on MRT target visibility, a multisensor analysis tool, a computer simulation of stairing-array thermal imagers, and a validated CCD camera model. Also discussed are an end-to-end model for detection performance evaluation against scenario-specific targets, Wiener-matrix image restoration beyond tha sampling passband, thermal signature training for military observers, reporting data for arrays with many elements, determination of FLIR LOS stabilization errors, fixed-pattern-noise cancellation in linear pyro arrays, a SPRITE detector characterization through impulse response testing, sine wave measurements of SPRITE detector MTF.

  10. The effects of noise over the complete space of diffusion tensor shape.

    Science.gov (United States)

    Gahm, Jin Kyu; Kindlmann, Gordon; Ennis, Daniel B

    2014-01-01

    Diffusion tensor magnetic resonance imaging (DT-MRI) is a technique used to quantify the microstructural organization of biological tissues. Multiple images are necessary to reconstruct the tensor data and each acquisition is subject to complex thermal noise. As such, measures of tensor invariants, which characterize components of tensor shape, derived from the tensor data will be biased from their true values. Previous work has examined this bias, but over a narrow range of tensor shape. Herein, we define the mathematics for constructing a tensor from tensor invariants, which permits an intuitive and principled means for building tensors with a complete range of tensor shape and salient microstructural properties. Thereafter, we use this development to evaluate by simulation the effects of noise on characterizing tensor shape over the complete space of tensor shape for three encoding schemes with different SNR and gradient directions. We also define a new framework for determining the distribution of the true values of tensor invariants given their measures, which provides guidance about the confidence the observer should have in the measures. Finally, we present the statistics of tensor invariant estimates over the complete space of tensor shape to demonstrate how the noise sensitivity of tensor invariants varies across the space of tensor shape as well as how the imaging protocol impacts measures of tensor invariants. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Coupled granular/continuous medium for thermally stable perpendicular magnetic recording

    International Nuclear Information System (INIS)

    Sonobe, Y.; Weller, D.; Ikeda, Y.; Takano, K.; Schabes, M.E.; Zeltzer, G.; Do, H.; Yen, B.K.; Best, M.E.

    2001-01-01

    We studied coupled granular/continuous (CGC) perpendicular media consisting of a continuous multilayer structure and a granular layer. The addition of Co/Pt multilayers decreased the nucleation field from 200 to -1800 Oe and increased the squareness from 0.9 to 1.0. The moment decay at room temperature was significantly reduced from -4.8% to -0.05% per decade. At elevated temperatures, strong exchange coupling between a granular layer and a continuous layer is needed for thermal stability. The exchange-coupled continuous layer reduces thermal demagnetization as it effectively increases the grain size, tightens the grain distribution, and prevents the reversal of individual grains. Magnetic Force Microscope image showed a larger magnetic cluster size for the CGC structure. Compared to the CoCr 18 Pt 12 medium, the CGC medium had 2.3 dB higher output. However, the noise for the CGC medium increased with the recording density, while the noise for the CoCr 18 Pt 12 medium remained constant from 4 to 15 kfc/mm. Further optimization and noise reduction are still required for future high density recording

  12. Coupled granular/continuous medium for thermally stable perpendicular magnetic recording

    Science.gov (United States)

    Sonobe, Y.; Weller, D.; Ikeda, Y.; Takano, K.; Schabes, M. E.; Zeltzer, G.; Do, H.; Yen, B. K.; Best, M. E.

    2001-10-01

    We studied coupled granular/continuous (CGC) perpendicular media consisting of a continuous multilayer structure and a granular layer. The addition of Co/Pt multilayers decreased the nucleation field from 200 to -1800 Oe and increased the squareness from 0.9 to 1.0. The moment decay at room temperature was significantly reduced from -4.8% to -0.05% per decade. At elevated temperatures, strong exchange coupling between a granular layer and a continuous layer is needed for thermal stability. The exchange-coupled continuous layer reduces thermal demagnetization as it effectively increases the grain size, tightens the grain distribution, and prevents the reversal of individual grains. Magnetic Force Microscope image showed a larger magnetic cluster size for the CGC structure. Compared to the CoCr 18Pt 12 medium, the CGC medium had 2.3 dB higher output. However, the noise for the CGC medium increased with the recording density, while the noise for the CoCr 18Pt 12 medium remained constant from 4 to 15 kfc/mm. Further optimization and noise reduction are still required for future high density recording.

  13. Infrared thermal imaging for automated detection of diabetic foot complications

    NARCIS (Netherlands)

    van Netten, Jaap J.; van Baal, Jeff G.; Liu, C.; van der Heijden, Ferdinand; Bus, Sicco A.

    Background: Although thermal imaging can be a valuable technology in the prevention and management of diabetic foot disease, it is not yet widely used in clinical practice. Technological advancement in infrared imaging increases its application range. The aim was to explore the first steps in the

  14. Infrared thermal imaging for automated detection of diabetic foot complications

    NARCIS (Netherlands)

    van Netten, Jaap J.; van Baal, Jeff G.; Liu, Chanjuan; van der Heijden, Ferdi; Bus, Sicco A.

    2013-01-01

    Although thermal imaging can be a valuable technology in the prevention and management of diabetic foot disease, it is not yet widely used in clinical practice. Technological advancement in infrared imaging increases its application range. The aim was to explore the first steps in the applicability

  15. A model for measurement of noise in CCD digital-video cameras

    International Nuclear Information System (INIS)

    Irie, K; Woodhead, I M; McKinnon, A E; Unsworth, K

    2008-01-01

    This study presents a comprehensive measurement of CCD digital-video camera noise. Knowledge of noise detail within images or video streams allows for the development of more sophisticated algorithms for separating true image content from the noise generated in an image sensor. The robustness and performance of an image-processing algorithm is fundamentally limited by sensor noise. The individual noise sources present in CCD sensors are well understood, but there has been little literature on the development of a complete noise model for CCD digital-video cameras, incorporating the effects of quantization and demosaicing

  16. Teaching physics and understanding infrared thermal imaging

    Science.gov (United States)

    Vollmer, Michael; Möllmann, Klaus-Peter

    2017-08-01

    Infrared thermal imaging is a very rapidly evolving field. The latest trends are small smartphone IR camera accessories, making infrared imaging a widespread and well-known consumer product. Applications range from medical diagnosis methods via building inspections and industrial predictive maintenance etc. also to visualization in the natural sciences. Infrared cameras do allow qualitative imaging and visualization but also quantitative measurements of the surface temperatures of objects. On the one hand, they are a particularly suitable tool to teach optics and radiation physics and many selected topics in different fields of physics, on the other hand there is an increasing need of engineers and physicists who understand these complex state of the art photonics systems. Therefore students must also learn and understand the physics underlying these systems.

  17. An Extension to a Filter Implementation of Local Quadratic Surface for Image Noise Estimation

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg

    1999-01-01

    Based on regression analysis this paper gives a description for simple image filter design. Specifically 3x3 filter implementations of a quadratic surface, residuals from this surface, gradients and the Laplacian are given. For the residual a 5x5 filter is given also. It is shown that the 3x3......) it is concluded that if striping is to be considered as a part of the noise, the residual from a 3x3 median filter seems best. If we are interested in a salt-and-pepper noise estimator the proposed extension to the 3x3 filter for the residual from a quadratic surface seems best. Simple statistics...

  18. Quality control in digital mammography: the noise components

    Energy Technology Data Exchange (ETDEWEB)

    Leyton, Fernando [Universidade de Tarapaca, Arica (Chile). Centro de Estudios en Ciencias Radiologicas; Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Nogueira, Maria do Socorro, E-mail: mnogue@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Duran, Maria Paz [Clinica Alemana, Santiago (Chile). Dept. de Radiologia; Dantas, Marcelino, E-mail: marcelino@inb.gov.b [Industrias Nucleares do Brasil (INB), Caldas, MG (Brazil). Unidade de Tratamento de Minerios; Ubeda, Carlos, E-mail: cubeda@uta.c [Universidade de Tarapaca, Arica (Chile). Fac. de Ciencias de la Salud

    2011-07-01

    To measure the linearity of the detector and determine the noise components (quantum, electronic and structural noise) that contributed to losing image quality and to determine the signal noise ratio (SNR) and contrast noise ratio (CNR). This paper describes the results of the implementation of a protocol for quality control in digital mammography performed in two direct digital mammography equipment (Hologic, Selenia) in Santiago of Chile. Shows the results of linearity and noise analysis of the images which establishes the main cause of noise in the image of the mammogram to ensure the quality and optimize procedures. The study evaluated two digital mammography's Selenia, Hologic (DR) from Santiago, Chile. We conducted the assessment of linearity of the detector, the signal noise ratio, contrast noise ratio and was determined the contribution of different noise components (quantum, electronics and structural noise). Used different thicknesses used in clinical practice according to the protocol for quality control in digital mammography of Spanish society of medical physics and NHSBSP Equipment Report 0604 Version 3. The Selenia mammography software was used for the analysis of images and Unfors Xi detector for measuring doses. The mammography detector has a linear performance, the CNR and SNR did not comply with the Protocol for the thicknesses of 60 and 70 mm. The main contribution of the noise corresponds to the quantum noise, therefore it is necessary to adjust and optimize the mammography system. (author)

  19. Quality control in digital mammography: the noise components

    International Nuclear Information System (INIS)

    Leyton, Fernando; Nogueira, Maria do Socorro; Duran, Maria Paz; Dantas, Marcelino; Ubeda, Carlos

    2011-01-01

    To measure the linearity of the detector and determine the noise components (quantum, electronic and structural noise) that contributed to losing image quality and to determine the signal noise ratio (SNR) and contrast noise ratio (CNR). This paper describes the results of the implementation of a protocol for quality control in digital mammography performed in two direct digital mammography equipment (Hologic, Selenia) in Santiago of Chile. Shows the results of linearity and noise analysis of the images which establishes the main cause of noise in the image of the mammogram to ensure the quality and optimize procedures. The study evaluated two digital mammography's Selenia, Hologic (DR) from Santiago, Chile. We conducted the assessment of linearity of the detector, the signal noise ratio, contrast noise ratio and was determined the contribution of different noise components (quantum, electronics and structural noise). Used different thicknesses used in clinical practice according to the protocol for quality control in digital mammography of Spanish society of medical physics and NHSBSP Equipment Report 0604 Version 3. The Selenia mammography software was used for the analysis of images and Unfors Xi detector for measuring doses. The mammography detector has a linear performance, the CNR and SNR did not comply with the Protocol for the thicknesses of 60 and 70 mm. The main contribution of the noise corresponds to the quantum noise, therefore it is necessary to adjust and optimize the mammography system. (author)

  20. Simultaneous measurement of thermal conductivity and heat capacity by flash thermal imaging methods

    Science.gov (United States)

    Tao, N.; Li, X. L.; Sun, J. G.

    2017-06-01

    Thermal properties are important for material applications involved with temperature. Although many measurement methods are available, they may not be convenient to use or have not been demonstrated suitable for testing of a wide range of materials. To address this issue, we developed a new method for the nondestructive measurement of the thermal effusivity of bulk materials with uniform property. This method is based on the pulsed thermal imaging-multilayer analysis (PTI-MLA) method that has been commonly used for testing of coating materials. Because the test sample for PTI-MLA has to be in a two-layer configuration, we have found a commonly used commercial tape to construct such test samples with the tape as the first-layer material and the bulk material as the substrate. This method was evaluated for testing of six selected solid materials with a wide range of thermal properties covering most engineering materials. To determine both thermal conductivity and heat capacity, we also measured the thermal diffusivity of these six materials by the well-established flash method using the same experimental instruments with a different system setup. This paper provides a description of these methods, presents detailed experimental tests and data analyses, and discusses measurement results and their comparison with literature values.

  1. An intelligent approach for cooling radiator fault diagnosis based on infrared thermal image processing technique

    International Nuclear Information System (INIS)

    Taheri-Garavand, Amin; Ahmadi, Hojjat; Omid, Mahmoud; Mohtasebi, Seyed Saeid; Mollazade, Kaveh; Russell Smith, Alan John; Carlomagno, Giovanni Maria

    2015-01-01

    This research presents a new intelligent fault diagnosis and condition monitoring system for classification of different conditions of cooling radiator using infrared thermal images. The system was adopted to classify six types of cooling radiator faults; radiator tubes blockage, radiator fins blockage, loose connection between fins and tubes, radiator door failure, coolant leakage, and normal conditions. The proposed system consists of several distinct procedures including thermal image acquisition, image pre-processing, image processing, two-dimensional discrete wavelet transform (2D-DWT), feature extraction, feature selection using a genetic algorithm (GA), and finally classification by artificial neural networks (ANNs). The 2D-DWT is implemented to decompose the thermal images. Subsequently, statistical texture features are extracted from the original images and are decomposed into thermal images. The significant selected features are used to enhance the performance of the designed ANN classifier for the 6 types of cooling radiator conditions (output layer) in the next stage. For the tested system, the input layer consisted of 16 neurons based on the feature selection operation. The best performance of ANN was obtained with a 16-6-6 topology. The classification results demonstrated that this system can be employed satisfactorily as an intelligent condition monitoring and fault diagnosis for a class of cooling radiator. - Highlights: • Intelligent fault diagnosis of cooling radiator using thermal image processing. • Thermal image processing in a multiscale representation structure by 2D-DWT. • Selection features based on a hybrid system that uses both GA and ANN. • Application of ANN as classifier. • Classification accuracy of fault detection up to 93.83%

  2. WE-FG-207B-09: Experimental Assessment of Noise and Spatial Resolution in Virtual Non-Contrast Dual-Energy CT Images Across Multiple Patient Sizes and CT Systems

    International Nuclear Information System (INIS)

    Montoya, J; Ferrero, A; Yu, L; Leng, S; McCollough, C

    2016-01-01

    Purpose: To investigate the noise and spatial resolution properties of virtual non-contrast (VNC) dual-energy CT images compared to true non-contrast (TNC) images across multiple patient sizes and CT systems. Methods: Torso-shaped water phantoms with lateral widths of 25, 30, 35, 40 and 45 cm and a high resolution bar pattern phantom (Catphan CTP528) were scanned using 2nd and 3rd generation dual-source CT systems (Scanner A: Somatom Definition Flash, Scanner B: Somatom Force, Siemens Healthcare) in dual-energy scan mode with the same radiation dose for a given phantom size. Tube potentials of 80/Sn140 and 100/Sn140 on Scanner A and 80/Sn150, 90/Sn150 and 100/Sn150 on Scanner B were evaluated to examine the impact of spectral separation. Images were reconstructed using a medium sharp quantitative kernel (Qr40), 1.0-mm thickness, 1.0-mm interval and 20 cm field of view. Mixed images served as TNC images. VNC images were created using commercial software (Virtual Unenhanced, Syngo VIA Version VA30, Siemens Healthcare). The noise power spectrum (NPS), area under the NPS, peak frequency of the NPS and image noise were measured for every phantom size and tube potential combination in TNC and VNC images. Results were compared within and between CT systems. Results: Minimal shift in NPS peak frequencies was observed in VNC images compared to TNC for NPS having pronounced peaks. Image noise and area under the NPS were higher in VNC images compared to TNC images across all tube potentials and for scanner A compared to scanner B. Limiting spatial resolution was deemed to be identical between VNC and TNC images. Conclusion: Quantitative assessment of image quality in VNC images demonstrated higher noise but equivalent spatial resolution compared to TNC images. Decreased noise was observed in the 3rd generation dual-source CT system for tube potential pairs having greater spectral separation. Dr. McCollough receives research support from Siemens Healthcare

  3. WE-FG-207B-09: Experimental Assessment of Noise and Spatial Resolution in Virtual Non-Contrast Dual-Energy CT Images Across Multiple Patient Sizes and CT Systems

    Energy Technology Data Exchange (ETDEWEB)

    Montoya, J; Ferrero, A; Yu, L; Leng, S; McCollough, C [Mayo Clinic, Rochester, MN (United States)

    2016-06-15

    Purpose: To investigate the noise and spatial resolution properties of virtual non-contrast (VNC) dual-energy CT images compared to true non-contrast (TNC) images across multiple patient sizes and CT systems. Methods: Torso-shaped water phantoms with lateral widths of 25, 30, 35, 40 and 45 cm and a high resolution bar pattern phantom (Catphan CTP528) were scanned using 2nd and 3rd generation dual-source CT systems (Scanner A: Somatom Definition Flash, Scanner B: Somatom Force, Siemens Healthcare) in dual-energy scan mode with the same radiation dose for a given phantom size. Tube potentials of 80/Sn140 and 100/Sn140 on Scanner A and 80/Sn150, 90/Sn150 and 100/Sn150 on Scanner B were evaluated to examine the impact of spectral separation. Images were reconstructed using a medium sharp quantitative kernel (Qr40), 1.0-mm thickness, 1.0-mm interval and 20 cm field of view. Mixed images served as TNC images. VNC images were created using commercial software (Virtual Unenhanced, Syngo VIA Version VA30, Siemens Healthcare). The noise power spectrum (NPS), area under the NPS, peak frequency of the NPS and image noise were measured for every phantom size and tube potential combination in TNC and VNC images. Results were compared within and between CT systems. Results: Minimal shift in NPS peak frequencies was observed in VNC images compared to TNC for NPS having pronounced peaks. Image noise and area under the NPS were higher in VNC images compared to TNC images across all tube potentials and for scanner A compared to scanner B. Limiting spatial resolution was deemed to be identical between VNC and TNC images. Conclusion: Quantitative assessment of image quality in VNC images demonstrated higher noise but equivalent spatial resolution compared to TNC images. Decreased noise was observed in the 3rd generation dual-source CT system for tube potential pairs having greater spectral separation. Dr. McCollough receives research support from Siemens Healthcare.

  4. The propagation of stochastic pixel noise into magnitude and phase values in the Fourier analysis of digital images

    International Nuclear Information System (INIS)

    Holden, J.E.; Halama, J.R.; Hasegawa, B.H.

    1986-01-01

    The use of Fourier analysis in nuclear medicine gated blood ventriculography provides a useful example of the application of Fourier methods to digital medical imaging. In particular, the nuclear medicine experience demonstrates that there is diagnostic significance not only in the pixel averages of temporal Fourier magnitude and phase computed in various image regions, but also in the distributions of the individual pixel values about those averages. However, a region containing pixels that are perfectly synchronous on average would still yield a finite distribution of calculated Fourier coefficients due to the propagation of stochastic pixel noise into the calculated values. The authors have studied this noise component of both the magnitude and phase distributions using phantom studies and computer simulation. In both approaches, several thousand one-pixel 'ventriculograms' were generated, all identical to each other except for stochastic noise. Fourier magnitudes and phases at several frequencies were calculated and histograms generated. A theoretical prediction of the distributions was developed and shown to fit the experimental results well. The authors' formalism can be used to estimate study count requirements or, for fixed study counts, to assess the stochastic noise contribution in the interpretation of measured phase and magnitude distributions. (author)

  5. Confirmation of Thermal Images and Vibration Signals for Intelligent Machine Fault Diagnostics

    Directory of Open Access Journals (Sweden)

    Achmad Widodo

    2012-01-01

    Full Text Available This paper deals with the maintenance technique for industrial machinery using the artificial neural network so-called self-organizing map (SOM. The aim of this work is to develop intelligent maintenance system for machinery based on an alternative way, namely, thermal images instead of vibration signals. SOM is selected due to its simplicity and is categorized as an unsupervised algorithm. Following the SOM training, machine fault diagnostics is performed by using the pattern recognition technique of machine conditions. The data used in this work are thermal images and vibration signals, which were acquired from machine fault simulator (MFS. It is a reliable tool and is able to simulate several conditions of faulty machine such as unbalance, misalignment, looseness, and rolling element bearing faults (outer race, inner race, ball, and cage defects. Data acquisition were conducted simultaneously by infrared thermography camera and vibration sensors installed in the MFS. The experimental data are presented as thermal image and vibration signal in the time domain. Feature extraction was carried out to obtain salient features sensitive to machine conditions from thermal images and vibration signals. These features are then used to train the SOM for intelligent machine diagnostics process. The results show that SOM can perform intelligent fault diagnostics with plausible accuracies.

  6. Receive-Noise Analysis of Capacitive Micromachined Ultrasonic Transducers.

    Science.gov (United States)

    Bozkurt, Ayhan; Yaralioglu, G Goksenin

    2016-11-01

    This paper presents an analysis of thermal (Johnson) noise received from the radiation medium by otherwise noiseless capacitive micromachined ultrasonic transducer (CMUT) membranes operating in their fundamental resonance mode. Determination of thermal noise received by multiple numbers of transducers or a transducer array requires the assessment of cross-coupling through the radiation medium, as well as the self-radiation impedance of the individual transducer. We show that the total thermal noise received by the cells of a CMUT has insignificant correlation, and is independent of the radiation impedance, but is only determined by the mass of each membrane and the electromechanical transformer ratio. The proof is based on the analytical derivations for a simple transducer with two cells, and extended to transducers with numerous cells using circuit simulators. We used a first-order model, which incorporates the fundamental resonance of the CMUT. Noise power is calculated by integrating over the entire spectrum; hence, the presented figures are an upper bound for the noise. The presented analyses are valid for a transimpedance amplifier in the receive path. We use the analysis results to calculate the minimum detectable pressure of a CMUT. We also provide an analysis based on the experimental data to show that output noise power is limited by and comparable to the theoretical upper limit.

  7. The Impact of the Shallow-Trench Isolation Effect on Flicker Noise of Source Follower MOSFETs in a CMOS Image Sensor.

    Science.gov (United States)

    Fan, C C; Chiu, Y C; Liu, C; Lai, W W; Cheng, C H; Lin, D L; Li, G R; Lo, Y H; Chang, C W; Tsai, C C; Chang, C Y

    2018-06-01

    The flicker noise of source follower transistors is the dominant noise source in image sensors. This paper reports a systematic study of the shallow trench isolation effect in transistors with different sizes under high temperature conditions that correspond to the quantity of empty defect sites. The effects of shallow trench isolation sidewall defects on flicker noise characteristics are investigated. In addition, the low-frequency noise and subthreshold swing degrade simultaneously in accordance to the device gate width scaling. Both serious subthreshold leakage and considerable noise can be attributed to the high trap density near the STI edge. Consequently, we propose a coincidental relationship between the noise level and the subthreshold characteristic; its trend is identical to the experiments and simulation results.

  8. On the nature of data collection for soft-tissue image-to-physical organ registration: a noise characterization study

    Science.gov (United States)

    Collins, Jarrod A.; Heiselman, Jon S.; Weis, Jared A.; Clements, Logan W.; Simpson, Amber L.; Jarnagin, William R.; Miga, Michael I.

    2017-03-01

    In image-guided liver surgery (IGLS), sparse representations of the anterior organ surface may be collected intraoperatively to drive image-to-physical space registration. Soft tissue deformation represents a significant source of error for IGLS techniques. This work investigates the impact of surface data quality on current surface based IGLS registration methods. In this work, we characterize the robustness of our IGLS registration methods to noise in organ surface digitization. We study this within a novel human-to-phantom data framework that allows a rapid evaluation of clinically realistic data and noise patterns on a fully characterized hepatic deformation phantom. Additionally, we implement a surface data resampling strategy that is designed to decrease the impact of differences in surface acquisition. For this analysis, n=5 cases of clinical intraoperative data consisting of organ surface and salient feature digitizations from open liver resection were collected and analyzed within our human-to-phantom validation framework. As expected, results indicate that increasing levels of noise in surface acquisition cause registration fidelity to deteriorate. With respect to rigid registration using the raw and resampled data at clinically realistic levels of noise (i.e. a magnitude of 1.5 mm), resampling improved TRE by 21%. In terms of nonrigid registration, registrations using resampled data outperformed the raw data result by 14% at clinically realistic levels and were less susceptible to noise across the range of noise investigated. These results demonstrate the types of analyses our novel human-to-phantom validation framework can provide and indicate the considerable benefits of resampling strategies.

  9. Thermalization of squeezed states

    International Nuclear Information System (INIS)

    Solomon, Allan I

    2005-01-01

    Starting with a thermal squeezed state defined as a conventional thermal state based on an appropriate Hamiltonian, we show how an important physical property, the signal-to-noise ratio, is degraded, and propose a simple model of thermalization (Kraus thermalization)

  10. A fourth order PDE based fuzzy c- means approach for segmentation of microscopic biopsy images in presence of Poisson noise for cancer detection.

    Science.gov (United States)

    Kumar, Rajesh; Srivastava, Subodh; Srivastava, Rajeev

    2017-07-01

    For cancer detection from microscopic biopsy images, image segmentation step used for segmentation of cells and nuclei play an important role. Accuracy of segmentation approach dominate the final results. Also the microscopic biopsy images have intrinsic Poisson noise and if it is present in the image the segmentation results may not be accurate. The objective is to propose an efficient fuzzy c-means based segmentation approach which can also handle the noise present in the image during the segmentation process itself i.e. noise removal and segmentation is combined in one step. To address the above issues, in this paper a fourth order partial differential equation (FPDE) based nonlinear filter adapted to Poisson noise with fuzzy c-means segmentation method is proposed. This approach is capable of effectively handling the segmentation problem of blocky artifacts while achieving good tradeoff between Poisson noise removals and edge preservation of the microscopic biopsy images during segmentation process for cancer detection from cells. The proposed approach is tested on breast cancer microscopic biopsy data set with region of interest (ROI) segmented ground truth images. The microscopic biopsy data set contains 31 benign and 27 malignant images of size 896 × 768. The region of interest selected ground truth of all 58 images are also available for this data set. Finally, the result obtained from proposed approach is compared with the results of popular segmentation algorithms; fuzzy c-means, color k-means, texture based segmentation, and total variation fuzzy c-means approaches. The experimental results shows that proposed approach is providing better results in terms of various performance measures such as Jaccard coefficient, dice index, Tanimoto coefficient, area under curve, accuracy, true positive rate, true negative rate, false positive rate, false negative rate, random index, global consistency error, and variance of information as compared to other

  11. Feasibility of Johnson Noise Thermometry based on Digital Signal Processing Techniques

    International Nuclear Information System (INIS)

    Hwang, In Koo; Kim, Yang Mo

    2014-01-01

    This paper presents an implementation strategy of noise thermometry based on a digital signal processing technique and demonstrates its feasibilities. A key factor in its development is how to extract the small thermal noise signal from other noises, for example, random noise from amplifiers and continuous electromagnetic interference from the environment. The proposed system consists of two identical amplifiers and uses a cross correlation function to cancel the random noise of the amplifiers. Then, the external interference noises are eliminated by discriminating the difference in the peaks between the thermal signal and external noise. The gain of the amplifiers is estimated by injecting an already known pilot signal. The experimental simulation results of signal processing methods have demonstrated that the proposed approach is an effective method in eliminating an external noise signal and performing gain correction for development of the thermometry

  12. Comparison of radiation dose estimates, image noise, and scan duration in pediatric body imaging for volumetric and helical modes on 320-detector CT and helical mode on 64-detector CT

    International Nuclear Information System (INIS)

    Johnston, Jennifer H.; Podberesky, Daniel J.; Larson, David B.; Alsip, Christopher; Yoshizumi, Terry T.; Angel, Erin; Barelli, Alessandra; Toncheva, Greta; Egelhoff, John C.; Anderson-Evans, Colin; Nguyen, Giao B.; Frush, Donald P.; Salisbury, Shelia R.

    2013-01-01

    Advanced multidetector CT systems facilitate volumetric image acquisition, which offers theoretic dose savings over helical acquisition with shorter scan times. Compare effective dose (ED), scan duration and image noise using 320- and 64-detector CT scanners in various acquisition modes for clinical chest, abdomen and pelvis protocols. ED and scan durations were determined for 64-detector helical, 160-detector helical and volume modes under chest, abdomen and pelvis protocols on 320-detector CT with adaptive collimation and 64-detector helical mode on 64-detector CT without adaptive collimation in a phantom representing a 5-year-old child. Noise was measured as standard deviation of Hounsfield units. Compared to 64-detector helical CT, all acquisition modes on 320-detector CT resulted in lower ED and scan durations. Dose savings were greater for chest (27-46%) than abdomen/pelvis (18-28%) and chest/abdomen/pelvis imaging (8-14%). Noise was similar across scanning modes, although some protocols on 320-detector CT produced slightly higher noise. Dose savings can be achieved for chest, abdomen/pelvis and chest/abdomen/pelvis examinations on 320-detector CT compared to helical acquisition on 64-detector CT, with shorter scan durations. Although noise differences between some modes reached statistical significance, this is of doubtful diagnostic significance and will be studied further in a clinical setting. (orig.)

  13. SU-E-J-243: Possibility of Exposure Dose Reduction of Cone-Beam Computed Tomography in An Image Guided Patient Positioning System by Using Various Noise Suppression Filters

    International Nuclear Information System (INIS)

    Kamezawa, H; Arimura, H; Ohki, M; Shirieda, K; Kameda, N

    2014-01-01

    Purpose: To investigate the possibility of exposure dose reduction of the cone-beam computed tomography (CBCT) in an image guided patient positioning system by using 6 noise suppression filters. Methods: First, a reference dose (RD) and low-dose (LD)-CBCT (X-ray volume imaging system, Elekta Co.) images were acquired with a reference dose of 86.2 mGy (weighted CT dose index: CTDIw) and various low doses of 1.4 to 43.1 mGy, respectively. Second, an automated rigid registration for three axes was performed for estimating setup errors between a planning CT image and the LD-CBCT images, which were processed by 6 noise suppression filters, i.e., averaging filter (AF), median filter (MF), Gaussian filter (GF), bilateral filter (BF), edge preserving smoothing filter (EPF) and adaptive partial median filter (AMF). Third, residual errors representing the patient positioning accuracy were calculated as an Euclidean distance between the setup error vectors estimated using the LD-CBCT image and RD-CBCT image. Finally, the relationships between the residual error and CTDIw were obtained for 6 noise suppression filters, and then the CTDIw for LD-CBCT images processed by the noise suppression filters were measured at the same residual error, which was obtained with the RD-CBCT. This approach was applied to an anthropomorphic pelvic phantom and two cancer patients. Results: For the phantom, the exposure dose could be reduced from 61% (GF) to 78% (AMF) by applying the noise suppression filters to the CBCT images. The exposure dose in a prostate cancer case could be reduced from 8% (AF) to 61% (AMF), and the exposure dose in a lung cancer case could be reduced from 9% (AF) to 37% (AMF). Conclusion: Using noise suppression filters, particularly an adaptive partial median filter, could be feasible to decrease the additional exposure dose to patients in image guided patient positioning systems

  14. SU-E-J-243: Possibility of Exposure Dose Reduction of Cone-Beam Computed Tomography in An Image Guided Patient Positioning System by Using Various Noise Suppression Filters

    Energy Technology Data Exchange (ETDEWEB)

    Kamezawa, H [Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka (Japan); Fujimoto General Hospital, Miyakonojo, Miyazaki (Japan); Arimura, H; Ohki, M [Faculty of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka (Japan); Shirieda, K; Kameda, N [Fujimoto General Hospital, Miyakonojo, Miyazaki (Japan)

    2014-06-01

    Purpose: To investigate the possibility of exposure dose reduction of the cone-beam computed tomography (CBCT) in an image guided patient positioning system by using 6 noise suppression filters. Methods: First, a reference dose (RD) and low-dose (LD)-CBCT (X-ray volume imaging system, Elekta Co.) images were acquired with a reference dose of 86.2 mGy (weighted CT dose index: CTDIw) and various low doses of 1.4 to 43.1 mGy, respectively. Second, an automated rigid registration for three axes was performed for estimating setup errors between a planning CT image and the LD-CBCT images, which were processed by 6 noise suppression filters, i.e., averaging filter (AF), median filter (MF), Gaussian filter (GF), bilateral filter (BF), edge preserving smoothing filter (EPF) and adaptive partial median filter (AMF). Third, residual errors representing the patient positioning accuracy were calculated as an Euclidean distance between the setup error vectors estimated using the LD-CBCT image and RD-CBCT image. Finally, the relationships between the residual error and CTDIw were obtained for 6 noise suppression filters, and then the CTDIw for LD-CBCT images processed by the noise suppression filters were measured at the same residual error, which was obtained with the RD-CBCT. This approach was applied to an anthropomorphic pelvic phantom and two cancer patients. Results: For the phantom, the exposure dose could be reduced from 61% (GF) to 78% (AMF) by applying the noise suppression filters to the CBCT images. The exposure dose in a prostate cancer case could be reduced from 8% (AF) to 61% (AMF), and the exposure dose in a lung cancer case could be reduced from 9% (AF) to 37% (AMF). Conclusion: Using noise suppression filters, particularly an adaptive partial median filter, could be feasible to decrease the additional exposure dose to patients in image guided patient positioning systems.

  15. A Low-Noise Direct Incremental A/D Converter for FET-Based THz Imaging Detectors

    Directory of Open Access Journals (Sweden)

    Moustafa Khatib

    2018-06-01

    Full Text Available This paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and noise reduction stage based on a parametric chopper amplifier and a direct analog-to-digital conversion by means of an incremental ΣΔ converter, performing a lock-in operation with modulated sources. The FET detector is integrated with an on-chip antenna operating in the frequency range of 325–375 GHz and compliant with all process design rules. The cascade of the FET THz detector and readout chain is evaluated in terms of responsivity and Noise Equivalent Power (NEP measurements. The measured readout input-referred noise of 1.6 μ V r m s allows preserving the FET detector sensitivity by achieving a minimum NEP of 376 pW/ Hz in the optimum bias condition, while directly providing a digital output. The integrated readout chain features 65-dB peak-SNR and 80-μ W power consumption from a 1.8-V supply. The area of the antenna-coupled FET detector and the readout chain fits a pixel pitch of 455 μm, which is suitable for pixel array implementation. The proposed THz pixel has been successfully applied for imaging of concealed objects in a paper envelope under continuous-wave illumination.

  16. A framework for noise-power spectrum analysis of multidimensional images

    International Nuclear Information System (INIS)

    Siewerdsen, J.H.; Cunningham, I.A.; Jaffray, D.A.

    2002-01-01

    A methodological framework for experimental analysis of the noise-power spectrum (NPS) of multidimensional images is presented that employs well-known properties of the n-dimensional (nD) Fourier transform. The approach is generalized to n dimensions, reducing to familiar cases for n=1 (e.g., time series) and n=2 (e.g., projection radiography) and demonstrated experimentally for two cases in which n=3 (viz., using an active matrix flat-panel imager for x-ray fluoroscopy and cone-beam CT to form three-dimensional (3D) images in spatiotemporal and volumetric domains, respectively). The relationship between fully nD NPS analysis and various techniques for analyzing a 'central slice' of the NPS is formulated in a manner that is directly applicable to measured nD data, highlights the effects of correlation, and renders issues of NPS normalization transparent. The spatiotemporal NPS of fluoroscopic images is analyzed under varying conditions of temporal correlation (image lag) to investigate the degree to which the NPS is reduced by such correlation. For first-frame image lag of ∼5-8 %, the NPS is reduced by ∼20% compared to the lag-free case. A simple model is presented that results in an approximate rule of thumb for computing the effect of image lag on NPS under conditions of spatiotemporal separability. The volumetric NPS of cone-beam CT images is analyzed under varying conditions of spatial correlation, controlled by adjustment of the reconstruction filter. The volumetric NPS is found to be highly asymmetric, exhibiting a ramp characteristic in transverse planes (typical of filtered back-projection) and a band-limited characteristic in the longitudinal direction (resulting from low-pass characteristics of the imager). Such asymmetry could have implications regarding the detectability of structures visualized in transverse versus sagittal or coronal planes. In all cases, appreciation of the full dimensionality of the image data is essential to obtaining

  17. Lock-in thermal imaging for the early-stage detection of cutaneous melanoma: a feasibility study.

    Science.gov (United States)

    Bonmarin, Mathias; Le Gal, Frédérique-Anne

    2014-04-01

    This paper theoretically evaluates lock-in thermal imaging for the early-stage detection of cutaneous melanoma. Lock-in thermal imaging is based on the periodic thermal excitation of the specimen under test. Resulting surface temperature oscillations are recorded with an infrared camera and allow the detection of variations of the sample's thermophysical properties under the surface. In this paper, the steady-state and transient skin surface temperatures are numerically derived for a different stage of development of the melanoma lesion using a two-dimensional axisymmetric multilayer heat-transfer model. The transient skin surface temperature signals are demodulated according to the digital lock-in principle to compute both a phase and an amplitude image of the lesions. The phase image can be advantageously used to accurately detect cutaneous melanoma at an early stage of development while the maximal phase shift can give precious information about the lesion invasion depth. The ability of lock-in thermal imaging to suppress disturbing subcutaneous thermal signals is demonstrated. The method is compared with the previously proposed pulse-based approaches, and the influence of the modulation frequency is further discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Effect of noise in computed tomographic reconstructions on detectability

    International Nuclear Information System (INIS)

    Hanson, K.M.

    1982-01-01

    The detectability of features in an image is ultimately limited by the random fluctuations in density or noise present in that image. The noise in CT reconstructions arising from the statistical fluctuations in the one-dimensional input projection measurements has an unusual character owing to the reconstruction procedure. Such CT image noise differs from the white noise normally found in images in its lack of low-frequency components. The noise power spectrum of CT reconstructions can be related to the effective density of x-ray quanta detected in the projection measurements, designated as NEQ (noise-equivalent quanta). The detectability of objects that are somewhat larger than the spatial resolution is directly related to NEQ. Since contrast resolution may be defined in terms of the ability to detect large, low-contrast objects, the measurement of a CT scanner's NEQ may be used to characterize its contrast sensitivity

  19. THERMAL EFFECTS ON CAMERA FOCAL LENGTH IN MESSENGER STAR CALIBRATION AND ORBITAL IMAGING

    Directory of Open Access Journals (Sweden)

    S. Burmeister

    2018-04-01

    Full Text Available We analyse images taken by the MErcury Surface, Space ENviorment, GEochemistry, and Ranging (MESSENGER spacecraft for the camera’s thermal response in the harsh thermal environment near Mercury. Specifically, we study thermally induced variations in focal length of the Mercury Dual Imaging System (MDIS. Within the several hundreds of images of star fields, the Wide Angle Camera (WAC typically captures up to 250 stars in one frame of the panchromatic channel. We measure star positions and relate these to the known star coordinates taken from the Tycho-2 catalogue. We solve for camera pointing, the focal length parameter and two non-symmetrical distortion parameters for each image. Using data from the temperature sensors on the camera focal plane we model a linear focal length function in the form of f(T = A0 + A1 T. Next, we use images from MESSENGER’s orbital mapping mission. We deal with large image blocks, typically used for the production of a high-resolution digital terrain models (DTM. We analyzed images from the combined quadrangles H03 and H07, a selected region, covered by approx. 10,600 images, in which we identified about 83,900 tiepoints. Using bundle block adjustments, we solved for the unknown coordinates of the control points, the pointing of the camera – as well as the camera’s focal length. We then fit the above linear function with respect to the focal plane temperature. As a result, we find a complex response of the camera to thermal conditions of the spacecraft. To first order, we see a linear increase by approx. 0.0107 mm per degree temperature for the Narrow-Angle Camera (NAC. This is in agreement with the observed thermal response seen in images of the panchromatic channel of the WAC. Unfortunately, further comparisons of results from the two methods, both of which use different portions of the available image data, are limited. If leaving uncorrected, these effects may pose significant difficulties in

  20. The Impact of Optimal Respiratory Gating and Image Noise on Evaluation of Intratumor Heterogeneity on 18F-FDG PET Imaging of Lung Cancer

    NARCIS (Netherlands)

    Grootjans, W.; Tixier, F.; van der Vos, Charlotte Sophie; Vriens, D.; Le Rest, C.C.; Bussink, J.; Oyen, W.J.; de Geus-Oei, Lioe-Fee; Visvikis, D.; Visser, E.P.

    2016-01-01

    Accurate measurement of intratumor heterogeneity using parameters of texture on PET images is essential for precise characterization of cancer lesions. In this study, we investigated the influence of respiratory motion and varying noise levels on quantification of textural parameters in patients

  1. Noise canceling in-situ detection

    Science.gov (United States)

    Walsh, David O.

    2014-08-26

    Technologies applicable to noise canceling in-situ NMR detection and imaging are disclosed. An example noise canceling in-situ NMR detection apparatus may comprise one or more of a static magnetic field generator, an alternating magnetic field generator, an in-situ NMR detection device, an auxiliary noise detection device, and a computer.

  2. Radiation dose reduction using 100-kVp and a sinogram-affirmed iterative reconstruction algorithm in adolescent head CT: Impact on grey-white matter contrast and image noise.

    Science.gov (United States)

    Nagayama, Yasunori; Nakaura, Takeshi; Tsuji, Akinori; Urata, Joji; Furusawa, Mitsuhiro; Yuki, Hideaki; Hirarta, Kenichiro; Kidoh, Masafumi; Oda, Seitaro; Utsunomiya, Daisuke; Yamashita, Yasuyuki

    2017-07-01

    To retrospectively evaluate the image quality and radiation dose of 100-kVp scans with sinogram-affirmed iterative reconstruction (IR) for unenhanced head CT in adolescents. Sixty-nine patients aged 12-17 years underwent head CT under 120- (n = 34) or 100-kVp (n = 35) protocols. The 120-kVp images were reconstructed with filtered back-projection (FBP), 100-kVp images with FBP (100-kVp-F) and sinogram-affirmed IR (100-kVp-S). We compared the effective dose (ED), grey-white matter (GM-WM) contrast, image noise, and contrast-to-noise ratio (CNR) between protocols in supratentorial (ST) and posterior fossa (PS). We also assessed GM-WM contrast, image noise, sharpness, artifacts, and overall image quality on a four-point scale. ED was 46% lower with 100- than 120-kVp (p < 0.001). GM-WM contrast was higher, and image noise was lower, on 100-kVp-S than 120-kVp at ST (p < 0.001). CNR of 100-kVp-S was higher than of 120-kVp (p < 0.001). GM-WM contrast of 100-kVp-S was subjectively rated as better than of 120-kVp (p < 0.001). There were no significant differences in the other criteria between 100-kVp-S and 120-kVp (p = 0.072-0.966). The 100-kVp with sinogram-affirmed IR facilitated dramatic radiation reduction and better GM-WM contrast without increasing image noise in adolescent head CT. • 100-kVp head CT provides 46% radiation dose reduction compared with 120-kVp. • 100-kVp scanning improves subjective and objective GM-WM contrast. • Sinogram-affirmed IR decreases head CT image noise, especially in supratentorial region. • 100-kVp protocol with sinogram-affirmed IR is suited for adolescent head CT.

  3. REVIEW OF METHODS FOR THE SURVEILLANCE AND ACCESS CONTROL USING THE THERMAL IMAGING SYSTEM

    Directory of Open Access Journals (Sweden)

    Mate Krišto

    2016-12-01

    Full Text Available This paper presents methods for human detection for application in the field of national security in the context of state border surveillance. Except in the context of state border security, the presented methods can be applied to monitor other protected object and infrastructure such as ports and airports, power plants, water supply systems, oil pipelines, etc. Presented methods are based on use of thermal imaging systems for the human detection, recognition and identification. In addition to methods for the detection of persons, are presented and methods for face recognition and identification of the person. The use of such systems has special significance in the context of national security in the domain of timely detection of illegal crossing of state border or illegal movement near buildings, which are of special importance for national security such as traffic infrastructure facilities, power plants, military bases, especially in mountain or forests areas. In this context, thermal imaging has significant advantages over the optical camera surveillance systems because thermal imaging is robust to weather conditions and due to such an infrared thermal system can successfully applied in any weather conditions, or the periods of the day. Featured are procedures that has human detection results as well as a brief survey of specific implementation in terms of the use of infrared thermal imagers mounted on autonomous