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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Georgy Shakirin Paulo Crespo Fine Fiedler Andreas Wagner Wolfgang Enghardt Institute of Radiation Physics Forschungszentrum Dresden-Rossendorf e.V. Dresden Germany LIP Physics Department University of Coimbra Coimbra Portugal

The size of image elements influences significantly the quality of the image. A small voxel size increases the resolution but produces high oscillations of a signal. Large voxels produce homogeneous images, however, with low spatial resolution. The size of the voxel is always a compromise between suppressing signal noise which requires larger voxel size, and covering small imaging details which requires smaller voxel size. For the in-beam PET scanner BASTEI the size of the voxel can be enlarged for typical irradiation fields from the standard (1.6875 mm) 3 to 2 × 2 × 3 mm 3 without compromising the image quality. The images reconstructed with larger voxel are less noisy and still contain enough information about activity in small cavities and range deviations. reconstruction is two times faster for the 2 × 2 × 3 mm 3 voxel, as compared to the standard (1.6875 mm) 3 .

关键词： Positron emission tomography image reconstruction Magnetic heads Medical treatment Statistics Geometry Monitoring Physics Imaging phantoms Nuclear and plasma sciences

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On the optimum strategy for subsets based reconstruction of in-beam PET data

On the optimum strategy for subsets based reconstruction of ...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Georgy Shakirin Paulo Crespo Wolfgang Enghardt Institute of Radiation Physics Forschungszentrum Dresden-Rossendorf e.V. Dresden Germany LIP Physics Department University of Coimbra Coimbra Portugal Center for Radiation Research in Oncology OncoRay Technische Universitat Dresden Germany

We proposed the reconstruction scheme for the subsets based RFS-EM algorithm. The scheme includes 4 iterations only, the number of subsets decreases from iteration to iteration and equals to 8, 6, 4, and 2 subsets, respectively. The images reconstructed with this scheme are of similar quality as those reconstructed with the reference 50 iterations of ML-EM. High quality of the system matrix is required for RFS-EM reconstructions of large fields.

关键词： Positron emission tomography image reconstruction Magnetic heads Medical treatment Geometry Monitoring Statistics Physics Frequency Nuclear and plasma sciences

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Simultaneous Super-Resolution and Feature Extraction for Recognition of Low-Resolution Faces

Simultaneous Super-Resolution and Feature Extraction for Rec...

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26th IEEE conference on Computer vision and Pattern Recognition (CvPR 2008), vol.12

作者： Pablo H. Hennings-Yeomans Simon Baker B. v. K. vijaya Kumar ECE Department Carnegie Mellon University USA Microsoft Research Microsoft Corporation USA

Face recognition degrades when faces are of very low resolution since many details about the difference between one person and another can only be captured in images of sufficient resolution. In this work, we propose a new procedure for recognition of low-resolution faces, when there is a high-resolution training set available. Most previous super-resolution approaches are aimed at reconstruction, with recognition only as an after-thought. In contrast, in the proposed method, face features, as they would be extracted for a face recognition algorithm (e.g., eigenfaces, Fisher-faces, etc.), are included in a super-resolution method as prior information. This approach simultaneously provides measures of fit of the super-resolution result, from both reconstruction and recognition perspectives. This is different from the conventional paradigms of matching in a low-resolution domain, or, alternatively, applying a super-resolution algorithm to a low-resolution face and then classifying the super-resolution result. We show, for example, that recognition of faces of as low as 6 × 6 pixel size is considerably improved compared to matching using a super-resolution reconstruction followed by classification, and to matching with a low-resolution training set.

关键词： Feature extraction Face recognition image reconstruction Probes image resolution Degradation vectors data mining Interpolation Surveillance

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Descriptive experiment design unified with worst-case performance optimization-adapted regularization for high-resolution radar/SAR imaging

Descriptive experiment design unified with worst-case perfor...

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IEEE National conference on Radar

作者： Yuriy v. Shkvarko CINVESTAV Guadalajara Mexico

This paper considers the problem of high-resolution imaging of the environment formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the wavefield scattered from an extended remotely sensed scene (referred to as the scene image) via processing the discrete measurements of a finite number of independent realizations of the observed degraded radar data signals (one realization of the trajectory signal in the case of SAR). The model-level uncertainties are associated with unknown statistics of perturbations of the signal formation operator (SFO) in turbulent environment. The system-level uncertainties are attributed to the imperfect array calibration, finite dimensionality of measurements, uncontrolled antenna vibrations and random carrier trajectory deviations in the case of SAR. An effective method for SSP reconstruction is therefore proposed by incorporating into the minimum risk (MR) nonparametric spectral estimation strategy the experiment design-motivated constraints of SSP observability/identifiability for the finite-dimensional range continuous-to-discrete SFO algorithmically coupled with descriptive experiment design regularization (DEDR) and unified with worst-case statistical performance optimization approach. The MR objective functional is constrained by this information, and the robust DEDR reconstruction operator applicable to the scenarios with the low-rank uncertain estimated data correlation matrices is found. We also show how this algorithm may be considered generalization of the robust MvDR and the regularized inverse spatial filtering techniques. The efficiency of the developed technique is illustrated via numerical simulations.

关键词： Design optimization Radar imaging Radar polarimetry Radar remote sensing Radar scattering Layout Signal processing vibration measurement image reconstruction Algorithm design and analysis

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Development of CT and 3D‐CT Using Flat Panel Detector Based Real‐Time Digital Radiography System

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AIP conference Proceedings 2008年第1期1050卷 23-31页

作者： v. R. Ravindran C. Sreelakshmi vibin Rocket Propellant Plant Vikram Sarabhai Space Centre Thiruvananthapuram‐22

The application of Digital Radiography in the Nondestructive Evaluation (NDE) of space vehicle components is a recent development in India. A Real‐time DR system based on amorphous silicon Flat Panel Detector has been developed for the NDE of solid rocket motors at Rocket Propellant Plant of vSSC in a few years back. The technique has been successfully established for the nondestructive evaluation of solid rocket motors. The DR images recorded for a few solid rocket specimens are presented in the paper. The Real‐time DR system is capable of generating sufficient digital X‐ray image data with object rotation for the CT image reconstruction. In this paper the indigenous development of CT imaging based on the Realtime DR system for solid rocket motor is presented. Studies are also carried out to generate 3D‐CT image from a set of adjacent CT images of the rocket motor. The capability of revealing the spatial location and characterisation of defect is demonstrated by the CT and 3D‐CT images generated.

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A comparison of CT-based attenuation correction strategies for PET data of moving structures

A comparison of CT-based attenuation correction strategies f...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Christian Richter Cordelia Hoinkis Uwe Just Falk Ponisch Julia Woithe Wolfgang Enghardt OncoRay-Radiation Research in Oncology Technische Universität Dresden Germany Forschungszentrum Dresden-Rossendorf e.V. Dresden Germany

Respiratory motion can introduce image artefacts not only in 3D PET but also in 4D PET due to incorrect attenuation correction. In this work the influence of different attenuation correction strategies on 3D and 4D PET has been investigated. An extensive phantom study was carried out, using a normal 3D CT (pitch 1.5), a slow 3D CT (pitch 0.5), an ultraslow 3D CT (pitch 0.15), an average CT and a maximum intensity projection calculated from a 4D CT (pitch 0.1) for attenuation correction of both a 3D and 4D PET of a respiratory motion phantom. Additionally, the 4D PET was corrected phase-wise with a 4D CT (phase-correlated attenuation correction). The reconstructed PET images were analyzed concerning the reconstructed volume, motion amplitude (for 4D PET), activity concentration and activity distribution. Moreover a patient study was carried out investigating the influence of the different attenuation correction strategies for 4D PET to patient data. Therefore 4D PET data from six patients with non-small cell lung cancer (NSCLC) was alternatively attenuation corrected with a normal 3D CT, an average CT and with phase-correlated attenuation correction. The tumor volume was analyzed and the motion amplitude of the tumor was obtained from the 4D PET data sets. For the phantom data the attenuation correction with the slow CT results in the best agreement between expected and measured values of the examined quantities in 3D PET, whereas in 4D PET this was the case for the phase-correlated attenuation correction. In the patient study only small differences between the 4D PET attenuation correction methods were found. This can be explained by the relative small tumor motion in the patient population investigated (peak to peak amplitude below 5 mm except for one patient).

关键词： Attenuation Positron emission tomography Computed tomography Imaging phantoms Neoplasms image reconstruction Motion analysis image analysis image motion analysis Lungs

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Comparison of genetic-algorithm and emissivity-ratio analyses of image data from OMEGA implosion cores

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REvIEW OF SCIENTIFIC INSTRUMENTS 2008年第10期79卷 10E921页

作者： Nagayama, T. Mancini, R. C. Florido, R. Tommasini, R. Koch, J. A. Delettrez, J. A. Regan, S. P. Smalyuk, v. A. Welser-Sherrill, L. A. Golovkin, I. E. Univ Nevada Dept Phys Reno NV 89557 USA Lawrence Livermore Natl Lab Livermore CA 94550 USA Univ Rochester Laser Energet Lab Rochester NY 14623 USA Los Alamos Natl Lab Los Alamos NM 87545 USA Prism Computat Sci Madison WI 53711 USA

Detailed analysis of x-ray narrow-band images from argon-doped deuterium-filled inertial confinement fusion implosion experiments yields information about the temperature spatial structure in the core at the collapse of the implosion. We discuss the analysis of direct-drive implosion experiments at OMEGA, in which multiple narrow-band images were recorded with a multimonochromatic x-ray imaging instrument. The temperature spatial structure is investigated by using the sensitivity of the Ly beta/He beta line emissivity ratio to the temperature. Three analysis methods that consider the argon He beta and Ly beta image data are discussed and the results compared. The methods are based on a ratio of image intensities, ratio of Abel-inverted emissivities, and a search and reconstruction technique driven by a Pareto genetic algorithm.

关键词： explosions genetic algorithms laser fusion plasma diagnostics plasma temperature

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Hybrid scene reconstruction by integrating scan data and stereo image pairs

Hybrid scene reconstruction by integrating scan data and ste...

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6th International conference on 3-D Digital Imaging and Modeling

作者： Ma, Xiangyin Zha, Hongbin Peking Univ State Key Lab Machine Percept Beijing 100871 Peoples R China

ISBN: (纸本)9780769529394

3D geometric models obtained by using laser scanners are often incomplete due to the equipment limitations. In this paper we propose a novel hybrid reconstruction algorithm, which integrates stereo image pairs to overcome these limitations. This work focuses on a category of scenes that can be approximated by planes (such as manmade scenes). The scan data are first segmented into planar patches, many of which may be incomplete. Stereo image pairs are then incorporated to retrieve the missing data. Specifically, we decide each plane's extension in the image domain via segment-based stereo matching with disparity layers extracted from scan data. Then, points in the missing area are interpolated by calculating ray-plane intersections. All procedures are automatic except for the range to image registration. The validity of our approach is demonstrated by experiments on real data.

关键词： Stereo image processing

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3D ROI-image reconstruction from cone-beam data

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2007年第2期580卷 866-875页

作者： Xia, Dan Cho, Seungryong Bian, Junguo Zou, Yu Sidky, Emil Y. Zuo, Niamning Pan, Xiaochuan Univ Chicago Dept Radiol Chicago IL 60637 USA Acad Sinica Inst Automat Med Imaging Lab Beijing Peoples R China

Helical and circular trajectories are expected to be adopted dominantly for data acquisition in X-ray cone-beam (CB) computed tomography (CT) imaging. However, non-conventional trajectories, such as tilted helical, saddle, circle-circle, and circle-line trajectories, may also find important applications. Therefore, accurate image reconstruction from data acquired with these non-conventional trajectories remains of practical significance. However, the non-conventional trajectories have been studied on a case-per-case basis and little effort has been made to investigate all of these trajectories on a single algorithm. Recently, there has been significant development on image reconstruction for general CB trajectories. In particular, chord-based algorithms have been developed for image reconstruction in CBCT. In this work, we investigate the chord-based algorithms, which can accommodate data containing both longitudinal and transverse truncations to a certain extent, for image reconstruction from data acquired with four different trajectories: the tilted helical, saddle, circle-circle, and circle-line trajectories. The first two represent smooth trajectories, whereas the last two are non-smooth trajectories containing kinks. The significance of the work lies not only in demonstrating the ability of the algorithm for image reconstruction from CB data but also in visualizing the reconstructible regions-of-interest (ROIs) for those general trajectories so that one can setup the scanning parameters with an appropriate guide. (c) 2007 Published by Elsevier B.v.

关键词： data acquisition

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Bayesian multiresolution method for local tomography in dental x-ray imaging

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PHYSICS IN MEDICINE AND BIOLOGY 2007年第22期52卷 6663-6678页

作者： Niinimaki, K. Siltanen, S. Kolehmainen, v. Univ Kuopio Dept Phys FIN-70211 Kuopio Finland Tampere Univ Technol Inst Math FIN-33101 Tampere Finland

Dental tomographic cone-beam x-ray imaging devices record truncated projections and reconstruct a region of interest (ROI) inside the head. image reconstruction from the resulting local tomography data is an ill-posed inverse problem. A new Bayesian multiresolution method is proposed for local tomography reconstruction. The inverse problem is formulated in a well-posed statistical form where a prior model of the target tissues compensates for the incomplete x-ray projection data. Tissues are represented in a wavelet basis, and prior information is modeled in terms of a Besov norm penalty. The number of unknowns in the reconstruction problem is reduced by abandoning fine-scale wavelets outside the ROI. Compared to traditional voxel-based models, this multiresolution approach allows significant reduction of degrees of freedom without loss of accuracy inside the ROI, as shown by 2D examples using simulated and in vitro local tomography data.

关键词： ELECTRICAL-IMPEDANCE TOMOGRAPHY COMPUTED-TOMOGRAPHY RADON-TRANSFORM STATISTICAL INvERSION ITERATIvE reconstruction ANGLE TOMOGRAPHY NOISE REMOvAL CONvERGENCE RADIOGRAPHS ALGORITHMS Converge Noise cancellation Tomography wavelet basis X-Ray Computed Tomography Bayesian inference algorithms tooth radiography X-Ray Film Radon transforms

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