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conference on image reconstruction from incomplete data vII

作者： Bhatnagar, S. Natl Radio Astron Observ Socorro NM 87801 USA

ISBN: (纸本)9780819492173

Modern high sensitivity radio interferometric telescopes use ultra wide-band receivers on a large number of antenna elements to achieve the capability of imaging dynamic ranges in excess of 1:1,000,000. In practice, the imaging performance is limited by instrumental and ionospheric/atmospheric effects that corrupt the recorded data. Many of these effects are directionally dependent and vary with time and frequency. Correcting for them is therefore fundamentally more difficult and these effects have been ignored in classical image reconstruction algorithms. Few attempts in the past to correct for these effects in the image-domain did not deliver the required accuracy. Recent developments in new algorithms that can account for such direction dependent effects show promising results. In this paper I give a general mathematical description of these techniques, show that the resulting algorithms are more optimal in terms of imaging performance and computing requirements and show some results.

关键词： Interferometric imaging image reconstruction Radio Astronomy Direction-dependent effects

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Single image Spatially variant Out-of-focus Blur Removal

Single Image Spatially Variant Out-of-focus Blur Removal

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conference on image reconstruction from incomplete data vII

作者： Chan, Stanley H. Nguyen, Truong Q. Harvard Univ SEAS 33 Oxford St Cambridge MA 02138 USA UCSD Dept ECE La Jolla CA 92093 USA

ISBN: (纸本)9780819492173

This paper addresses the problem of two-layer out-of-focus blur removal from a single image, in which either the foreground or the background is in focus while the other is out of focus. To recover details from the blurry parts, the existing blind deconvolution algorithms are insufficient as the problem is spatially variant. The proposed method exploits the invariant structure of the problem by first predicting the occluded background. Then a blind deconvolution algorithm is applied to estimate the blur kernel and a coarse estimate of the image is found as a side product. Finally, the blurred region is recovered using total variation minimization, and fused with the sharp region to produce the final deblurred image.

关键词： Blind deconvolution spatially variant total variation alpha-matting kernel estimation depth

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Determining wind fields in atmospheric mountain waves using sailplane flight data

Determining wind fields in atmospheric mountain waves using ...

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conference on image reconstruction from incomplete data vII

作者： Zhang, Ni Millane, Rick P. Enevoldson, Einar Murray, James E. Univ Canterbury Dept Elect & Comp Engn Computat Imaging Grp Christchurch 1 New Zealand NASA Dryden Flight Res Ctr Edwardsville IL 93523 USA

ISBN: (纸本)9780819492173

The problem of estimating wind velocities from limited flight data recordings is considered, with application to sailplane flights in high-altitude atmospheric mountain waves. Sailplane flight recorders routinely measure only GPS position and the problem is highly underdetermined. The nature of this problem is studied and a maximum a posteriori estimator is developed using prior information on the wind velocity and the sailplane airspeed and heading. The method is tested by simulation and by application to sailplane flight data.

关键词： Maximum a posteriori wind velocity aircraft sailplane mountain wave atmospheric wave

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SPECT Imaging With Resolution Recovery

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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2012年第4期59卷 1458-1464页

作者： Bronnikov, Andrei v. Bronnikov Algorithms NL-6800 AB Arnhem Netherlands

Single-photon emission computed tomography (SPECT) is a method of choice for imaging spatial distributions of radioisotopes. Applications of this method are found in medicine, biomedical research and nuclear industry. This paper deals with improving spatial resolution in SPECT by applying correction for the point-spread function (PSF) in the reconstruction algorithm and optimizing the collimator. Several approaches are considered: the use of a depth-dependent PSF model for a parallel-beam collimator derived from experimental data, the extension of this model to a fan-beam collimator, a triangular approximation of the PSF for reconstruction acceleration, and a method for optimal fan-beam collimator design. An unmatched projector/backprojector ordered subsets expectation maximization (OSEM) algorithm is used for image reconstruction. Experimental results with simulated and physical phantom data of a micro-SPECT system show a significant improvement of spatial resolution with the proposed methods.

关键词： image quality nuclear medicine single photon emission computed tomography (SPECT)

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Study of optical micro-scanning reconstruction

Study of optical micro-scanning reconstruction

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conference on image reconstruction from incomplete data vII

作者： Zhao, Xunjie Li, Chengjin Soochow Univ Sch Phys Sci & Technol Suzhou 215006 Peoples R China Sci & Technol ElectOpt Secur Lab Sanhe 065201 Peoples R China

ISBN: (纸本)9780819492173

Infrared images provide valuable information for many applications. However, compared to a visible image, the image quality is poor and its spatial resolution is limited due to the focal plane arrays cannot be made dense enough to yield a sufficiently high spatial sampling frequency, which consequently leads to image blurring. Optical micro-scanning technique has been proven to be an effective method to increase the resolution of images. This technique is able to produce high resolution (HR) images from a set of optically shifted images of low-resolution (LR). Over the last decade, optical micro-scanning technique has become one of the active topics of research, among this, the super-resolution (SR) reconstruction algorithms are the focus. This paper starts with the basic principle of SR reconstruction. Then several methods of high-precision movement registration algorithm and SR reconstruction algorithms were introduced. This study particularly focuses on the more recent development in motion estimation methods. Furthermore, an algorithm based on sub-pixel image registration that estimates the displacements of the LR image is presented. The critical steps in image registration are collecting feature points and estimating a spatial transformation especially when outliers are present. In this paper, the Harris corner detector is used to find the feature points and then the point feature is described by the neighborhood difference in order to reduce the sensitivity to illumination variations. Moreover, the Random Sample Consensus(RANSAC) algorithm is employed to build a transformation model. Simulation results demonstrate that the method can estimate the displacements accurately.

关键词： super-resolution reconstruction optical micro-scanning sub-pixel registration Harris corner detector RANSAC image interpolation feature matching

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Maximum subarray algorithms for use in optical and radio astronomy

Maximum subarray algorithms for use in optical and radio ast...

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conference on image reconstruction from incomplete data vII

作者： Weddell, S. J. Takaoka, T. Read, T. Candy, R. Univ Canterbury Dept Elect & Comp Engn Christchurch 1 New Zealand Univ Canterbury Dept Comp Sci & Software Engn Christchurch 1 New Zealand

ISBN: (纸本)9780819492173

The maximum sub-array algorithm has been implemented within a field programmable gate array as an efficient centroiding method for wavefront slope estimation. However, a convenient platform for this work is a graphics processor unit (GPU). Translation of the maximum subarray algorithm to a GPU has been performed and shows significant performance gains compared to a single-core CPU. Recently, this algorithm has been applied to radio telescope images acquired for the Australian square kilometer array pathfinder project. This paper provides an overview of the maximum subarray algorithm and shows how this can be utilized for optical and radio telescope applications

关键词： graphics processing unit maximum subarray problem astronomical image processing

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Optical motion tracking to improve image quality in MRI of the brain

Optical motion tracking to improve image quality in MRI of t...

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conference on image reconstruction from incomplete data vII

作者： Maclaren, Julian Aksoy, Murat Ooi, Melvyn Bammer, Roland Stanford Univ Ctr Quantitat Neuroimaging Dept Radiol Stanford CA 94305 USA

ISBN: (纸本)9780819492173

Magnetic resonance imaging (MRI) of the brain is highly sensitivity to head motion. Prospective motion correction is a promising new method to prevent artifacts resulting from this effect. The image volume is continuously updated based on head tracking information, ensuring that the magnetic fields used for imaging maintain a constant geometric relationship relative to the object. This paper reviews current developments and methods of performing prospective correction. Optical tracking using cameras has major advantages over other methods used to obtain head pose information, as it does not affect the MR imaging process or interfere with the sequence timing. Results show that motion artifacts can be almost completely prevented for most imaging sequences. Despite this success, there are still engineering challenges to be solved before the technique becomes widely accepted in the clinic. These include improvements in miniaturization, marker fixation and MR compatibility.

关键词： MRI optical tracking prospective motion correction MR compatibility review

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Kepler mission exoplanet transit data analysis using fractal imaging

Kepler mission exoplanet transit data analysis using fractal...

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conference on image reconstruction from incomplete data vII

作者： Dehipawala, S. Tremberger, G., Jr. Majid, Y. Holden, T. Lieberman, D. Cheung, T. CUNY Queensborough Community Coll New York NY 11364 USA

ISBN: (纸本)9780819492173

The Kepler mission is designed to survey a fist-sized patch of the sky within the Milky Way galaxy for the discovery of exoplanets, with emphasis on near Earth-size exoplanets in or near the habitable zone. The Kepler space telescope would detect the brightness fluctuation of a host star and extract periodic dimming in the lightcurve caused by exoplanets that cross in front of their host star. The photometric data of a host star could be interpreted as an image where fractal imaging would be applicable. Fractal analysis could elucidate the incomplete data limitation posed by the data integration window. The fractal dimension difference between the lower and upper halves of the image could be used to identify anomalies associated with transits and stellar activity as the buried signals are expected to be in the lower half of such an image. Using an image fractal dimension resolution of 0.04 and defining the whole image fractal dimension as the Chi-square expected value of the fractal dimension, a p-value can be computed and used to establish a numerical threshold for decision making that may be useful in further studies of lightcurves of stars with candidate exoplanets. Similar fractal dimension difference approaches would be applicable to the study of photometric time series data via the Higuchi method. The correlated randomness of the brightness data series could be used to support inferences based on image fractal dimension differences. Fractal compression techniques could be used to transform a lightcurve image, resulting in a new image with a new fractal dimension value, but this method has been found to be ineffective for images with high information capacity. The three studied criteria could be used together to further constrain the Kepler list of candidate lightcurves of stars with possible exoplanets that may be planned for ground-based telescope confirmation.

关键词： fractal imaging Kepler mission exoplanets time series

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COMPARING ASTRONOMICAL dataCUBES USING LEvEL-SET TOPOLOGY

COMPARING ASTRONOMICAL DATACUBES USING LEVEL-SET TOPOLOGY

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19th IEEE International conference on image Processing (ICIP)

作者： Rosolowsky, Erik MacDonald, Braden Loeppky, Jason ASC 354-3187 Univ Way Kelowna BC V1V 1V7 Canada

ISBN: (纸本)9781467325332;9781467325349

We describe position-position-velocity data cubes derived from the star-forming interstellar medium (SFISM). The physical characteristics and evolution of the SFISM must be deduced from the incomplete information present in the observed data. Astrophysicists can simulate the evolution of the SFISM from first principles but the standard comparisons of simulated data with observations do not completely describe the SFISM. Given the hierarchical structure present in the emission, we forward the use of Reeb graphs as a tool for comparing data cubes. We describe the computation of a Reeb graph and show that the properties encoded in the Reeb graph highlight the deficiencies of simulations at capturing the structure of the SFISM.

关键词： Reeb Graphs Radio Astronomy data cubes Dendrograms

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Development of a three layer Compton telescope prototype based on continuous LaBr3 crystals and Silicon Photomultipliers

Development of a three layer Compton telescope prototype bas...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： M. Trovato J. Barrio P. Botas J. Cabello J. E. Gillam C. Lacasta J. Oliver M. Rafecas C. Solaz P. Solevi v. Stankova I. Torres-Espallardo G. Llosá Instituto de Fisica Corpuscular CSIC Spain Departamento de Física Atómica Molecular y Nuclear Universitat de Valencia Kirchhoff-Institute for Physics Heidelberg Germany

A three layer Compton telescope for dose monitoring in hadron therapy is under development at IFIC - valencia. It will consist of three detector layers and each layer will be made of a continuous LaBr 3 crystal coupled to four Silicon Photomultiplier (SiPM) arrays. A prototype made of two detector layers has already been assembled and tested. The detector layers consist of a 32×36×5 mm 3 and 32×36×10 mm 3 LaBr 3 crystal, each coupled to four SiPM arrays. The front-end electronics of each detector is based on the vATA64HDR16 application specific integrated circuit (ASIC). The gamma rays coming from a 22 Na source have been detected with the two detector layers working in time coincidence, allowing energy and position estimation.

关键词： Detectors Telescopes Crystals image reconstruction data acquisition Prototypes Energy resolution

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