Search results for "Iterative reconstruction"
showing 10 items of 129 documents
Sensitivity recovery for the AX-PET prototype using inter-crystal scattering events
2014
The development of novel detection devices and systems such as the AX-positron emission tomography (PET) demonstrator often introduce or increase the measurement of atypical coincidence events such as inter-crystal scattering (ICS). In more standard systems, ICS events often go undetected and the small measured fraction may be ignored. As the measured quantity of such events in the data increases, so too does the importance of considering them during image reconstruction. Generally, treatment of ICS events will attempt to determine which of the possible candidate lines of response (LoRs) correctly determine the annihilation photon trajectory. However, methods of assessment often have low su…
On axis holography by random particles encoding
2012
A method for eliminating the unwanted terms in an on axis hologram is presented. In this method, free randomly distributed nanoparticles are in proximity to the object and their Brownian motion encodes the spatial features of the object in the recorded hologram. The nanoparticles are localized and a decoding pattern is calculated for each frame. This decoding pattern is then used to remove the reference beam and the conjugate beam in the reconstruction of the hologram.
3D imaging and visualization: An overview of recent advances
2013
This paper presents an overview of our published work on physical principles, applications, and advances in integral imaging and digital holography. Various approaches for image capture, image reconstruction, and 3D display methods are overviewed. Applications including 3D underwater imaging, 3D imaging in photon-starved environments, 3D tracking of occluded objects, 3D optical microscopy, and 3D polarimetric imaging are reviewed.
A Demonstrator for a new Axial PET Concept
2008
In PET imaging, improving sensitivity while maintaining very good spatial resolution is crucial. To achieve this goal, we propose a novel concept of PET scanner, with axially arranged crystals, providing a high sensitivity and a 3D reconstruction of the gamma interaction point. The trans-axial coordinate is given by the crystal hit, while the z coordinate is reconstructed by the weighted distribution of light escaping the crystal and entering into an array of Wave Length Shifting (WLS) strips interleaving the crystal layers. This novel configuration allows full identification of Compton interactions in the crystals that can be included in image reconstruction thus enhancing the sensitivity.…
UTSW Small Animal Positron Emission Imager
2006
A Small Animal Imager (SAI) for PET has been designed, built, tested in phantoms, and applied to investigations in mice and rats. The device uses principles based on gamma-ray induced scintillation in crossed fiber optic detectors connected to Position Sensitive Photomultiplier Tubes (PSPMT). Each detector consists of an epoxied stack of 28 layers of 135 round 1 mm BCF-10 scintillating plastic fibers. The overlap region forms a 13.5times13.5times2.8 cm3 detector volume. Scintillating light from the fibers is detected by two (X and Y directions) Hamamatsu R-2486 PSPMTs with 16 anode wires in each of two orthogonal directions. A centroid-finding algorithm gives the position of a light cluster…
The EM imaging reconstruction method in γ-ray astronomy
1998
Abstract The simpler imaging reconstruction methods used for γ-ray coded mask telescopes are based on correlation methods, very fast and simple-to-use but with limitations in the reconstructed image. To improve these results, other reconstruction methods have been developed, such as the maximum entropy methods or the Iterative Removal Of Sources (IROS). However, such kind of methods are slower and can be impracticable for very complex telescopes. In this paper we present an alternative image reconstruction method, based on an iterative maximum likelihood algorithm called the EM algorithm, easy to implement and that can be successfully used for not very complex coded mask systems, as is the …
Monte Carlo evaluation of the Filtered Back Projection method for image reconstruction in proton computed tomography
2011
Abstract In this paper the use of the Filtered Back Projection (FBP) Algorithm, in order to reconstruct tomographic images using the high energy (200–250 MeV) proton beams, is investigated. The algorithm has been studied in detail with a Monte Carlo approach and image quality has been analysed and compared with the total absorbed dose. A proton Computed Tomography (pCT) apparatus, developed by our group, has been fully simulated to exploit the power of the Geant4 Monte Carlo toolkit. From the simulation of the apparatus, a set of tomographic images of a test phantom has been reconstructed using the FBP at different absorbed dose values. The images have been evaluated in terms of homogeneity…
Surface Reconstruction of Transparent Objects by Polarization Imaging
2008
This paper focuses a method to acquire the surface of transparent objects for 3D measurement. The technique relies on the so called ?Shape from Polarization? technique. The principle of this polarization imaging technique is as follows: after being reflected, an unpolarized light becomes partially linearly polarized. The surface normals can be evaluated by analyzing their polarization parameters and by knowing the refractive index of the object to be controlled. Finally, the 3D shape is obtained by integrating the normals field. After an introduction to expose the problematic, section 2 exposes the principles of polarization technique. The third and the last section deal with the polarimetr…
The Ultra Fast Flash Observatory pathfinder – UFFO-p GRB imaging and location with its coded mask X-ray imager UBAT
2013
The UFFO pathfinder mission will attempt to locate the optical afterglow of a GRB within seconds of its detection and location by a wide field X-ray imager. It will be mounted on the Lomonosov spacecraft for launch in 2013 and consists of a coded mask X-ray imager UBAT to detect a GRB and estimate a direction vector which will be passed to the SMT optical system which will rotate a moveable mirror to lock onto the GRB and direct the optical afterglow to a camera with a ~17′ wide aperture. We present the design geometry of the UBAT instrument only, with results of simulations for a range of GRB types to show probable photon integration times to be expected to extract a significant FOV image…
A Pixelated Silicon Positron Sensitive Imaging Probe
2006
A pixelated silicon positron sensitive imaging probe is under development to precisely localize superficially located tumors accumulating 18F-FDG. 18F-FDG has been a radioisotope of interest mainly because of the high uptake in tumors and the relatively short positron range. Silicon detectors have generally low detection efficiency for high energy photons and can be used for positron detection. We present a pixelated silicon positron sensitive imaging probe that has the 1.4-by-1.4-by-1.0 mm pixel size with equivalent electronic noise of ~1.2 keV FWHM. The small pixel size leads to the high spatial resolution. Probe movement in conjunction with appropriate reconstruction will allow sub-pixel…