Search results for "Iterative reconstruction"
showing 10 items of 129 documents
The AX-PET Concept: New Developments And Tomographic Imaging
2011
The Axial PET (AX-PET) concept proposes a novel detection geometry for PET, based on layers of long scintillating crystals axially aligned with the bore axis. Arrays of wavelength shifting (WLS) strips are placed orthogonally and underneath the crystal layers; both crystals and strips are individually readout by G-APDs. The axial coordinate is obtained from the WLS signals by means of a Center-of-Gravity method combined with a cluster algorithm. This design allows spatial resolution and sensitivity to be decoupled and thus simultaneously optimized. In this work we present the latest results obtained with the 2-module AX-PET scanner prototype, which consists of 6 radial layers of 8 LYSO crys…
Validation of the Monte Carlo Simulation of a Siemens Biograph mCT PET
2016
Geant4 Application for Tomography Emission (GATE) is a simulation platform based on GEANT4. It is designed to perform numerical simulations in medical imaging and radiotherapy. It is also used to simulate Emission Tomography (Positron Emission Tomography, PET and Single Photon Emission Computed Tomography, SPECT), Computed Tomography (CT) and Radiotherapy experiments. The purpose of this study is to validate a GATE model of the commercial PET/CT Siemens Biograph, the latest acquisition of the Clinical Hospital of Salamanca. The geometry of the system has been implemented in GATE, including the detector ring, the crystal blocks, the PMTs etc. Radionuclides for all measurements shall be \(^{1…
Synthesis of filters for specified axial irradiance by use of phase–space tomography
2001
A procedure for designing pupil filters for applications where specified axial responses are required is developed. The method is based on the mathematical relationship between the axial impulse response of a system and the Wigner distribution function (WDF) associated to its pupil function. The desired axial irradiance, which can also have a predefined behavior depending on spherical aberration, is used to obtain this WDF by tomographic reconstruction. The synthetic pupil is retrieved from this distribution.
Superresolved imaging in digital holography by superposition of tilted wavefronts
2006
A technique based on superresolution by digital holographic microscopic imaging is presented. We used a two dimensional (2-D) vertical-cavity self-emitting laser (VCSEL) array as spherical-wave illumination sources. The method is defined in terms of an incoherent superposition of tilted wavefronts. The tilted spherical wave originating from the 2-D VCSEL elements illuminates the target in transmission mode to obtain a hologram in a Mach-Zehnder interferometer configuration. Superresolved images of the input object above the common lens diffraction limit are generated by sequential recording of the individual holograms and numerical reconstruction of the image with the extended spatial frequ…
Holographically aided iterative phase retrieval
2012
Fourier transform holography (FTH) is a noise-resistant imaging technique which allows for nanometer spatial resolution x-ray imaging, where the inclusion of a small reference scattering object provides the otherwise missing phase information. With FTH, one normally requires a considerable distance between the sample and the reference to ensure spatial separation of the reconstruction and its autocorrelation. We demonstrate however that this requirement can be omitted at the small cost of iteratively separating the reconstruction and autocorrelation. In doing so, the photon efficiency of FTH can be increased due to a smaller illumination area, and we show how the presence of the reference p…
Optically-undistorted digital holographic microscopy for quantitative phase-contrast imaging
2011
We propose a telecentric architecture for circumventing, by a pure-optical method, the residual phase distortion inherent to standard configuration of digital holographic microscopy (DHM). With this proposal there is no need for computer compensation of the parabolic phase during the phase map recovering procedure. Futhermore, in off-axis configuration, the spatial frequency useful domain is enlarged. The validity of the method is demonstrated by performing quantitative measurements of depth differences
Based on Compton Camera
2016
Compton Cameras have been proposed as an alternative to SPECT imaging with Gamma Camera, mainly due to factors such as the electronic collimation, which allows a bigger field of view and provides further information from the acquired events if compared to devices with mechanical collimation. By contrast, this involves a higher amount of data to be processed. In medical devices this leads to waiting times that are generally higher than desirable by the health-care professionals. In this work we have assessed the reconstruction of Compton images by making use of iterative and non-iterative techniques, and also evaluated its performances as a SPECT imaging technique.
A mammographic phantom image reconstruction through Monte Carlo techniques
2005
Mammographic phantoms are employed during quality control test in breast screening locations and other health centres. These quality controls are performed to achieve the image quality required to detect breast abnormalities, ensuring the minimum risk to radiographied women. The aim of this study is the development of a methodology to reproduce the image of a mammogram during a routine exposure in a breast screening programme. In a first step, the CIRS 11A (MAMMO PHANTOM SP01) mammographic phantom has been simplified and modelled with the Monte Carlo transport code MCNP-4c2. Different tallies (F2 and F5) have been used to score the photon flux under the phantom, and a group of aluminium lay…
An FPGA-based design for real-time Super Resolution Reconstruction
2018
Since several decades, the camera spatial resolution is gradually increasing with the CMOS technology evolution. The image sensors provide more and more pixels, generating new constraints for the suitable optics. As an alternative, promising solutions propose Super Resolution (SR) image reconstruction to extend the image size without modifying the sensor architecture. Convincing state-of art studies demonstrate that these methods could even be implemented in real-time. Nevertheless, artifacts can be observed in highly textured areas of the image. In this paper, we propose a Local Adaptive Spatial Super Resolution (LASSR) method to fix this limitation. A real-time texture analysis is include…
Affine camera calibration from homographies of parallel planes
2010
This paper deals with the problem of retrieving the affine structure of a scene from two or more images of parallel planes. We propose a new approach that is solely based on plane homographies, calculated from point correspondences, and that does not require the recovery of the 3D structure of the scene. Neither vanishing points nor lines need to be extracted from the images. The case of a moving camera with constant intrinsic parameters and the one of cameras with possibly different parameters are both addressed. Extensive experiments with both synthetic and real images have validated our approach.