Search results for "Iterative reconstruction"
showing 10 items of 129 documents
Influence of image reconstruction parameters on cardiovascular risk reclassification by Computed Tomography Coronary Artery Calcium Score
2018
Objective: To investigate the influence of different CT reconstruction parameters on coronary artery calcium scoring (CACS) values and reclassification of predicted cardiovascular (CV) risk. Methods: CACS was evaluated in 113 patients undergoing ECG-gated 64-slice CT. Reference CACS protocol included standard kernel filter (B35f) with slice thickness/increment of 3/1.5 mm, and field-of-view (FOV) of 150â180 mm. Influence of different image reconstruction algorithms (reconstructed slice thickness/increment 2.0/1.0â1.5/0.8â3.0/2.0â3.0/3.0 mm; slice kernel B30f-B45f; FOV 200â250 mm) on Agatston score was assessed by Bland-Altman plots and concordance correlation coefficient (CCC) ana…
Coronary CT angiography using iterative reconstruction vs. filtered back projection: evaluation of image quality.
2014
To compare image quality of iterative reconstruction algorithm(IRIS) vs. standard filtered back projection(FBP) reconstruction in CT Coronary Angiography (CTCA).Thirty-four consecutive patients underwent CTCA for suspected or known CAD with Dual-Source CT (DSCT-Flash, Siemens). All datasets were reconstructed with 0.75/0.4 and 0.6/0.4 mm slice thickness/increment, using three standard FBP kernels (B26-B30-B46) and three comparable IRIS algorithms (I26-I30-I46). Vascular attenuation and noise were measured. CT vascular attenuation values [HU] were measured in: ascending aorta (Ao), right (RCA) and left (LCA) coronary artery, respectively. Signal-to-noise (SNR) and contrast-to-noise (CNR) rat…
Quantitation of Microcomputed Tomography-Imaged Ocular Microvasculature
2010
To quantitatively assess microvascular dimensions in the eyes of neonatal wild-type and VEGF(120)-tg mice, using a novel combination of techniques which permit three-dimensional (3D) image reconstruction.A novel combination of techniques was developed for the accurate 3D imaging of the microvasculature and demonstrated on the hyaloid vasculature of the neonatal mouse eye. Vascular corrosion casting is used to create a stable replica of the vascular network and X-ray microcomputed tomography (muCT) to obtain the 3D images. In-house computer-aided image analysis techniques were then used to perform a quantitative morphological analysis of the images.With the use of these methods, differences …
Impact of Model Shape Mismatch on Reconstruction Quality in Electrical Impedance Tomography
2012
Electrical impedance tomography (EIT) is a low-cost, noninvasive and radiation free medical imaging modality for monitoring ventilation distribution in the lung. Although such information could be invaluable in preventing ventilator-induced lung injury in mechanically ventilated patients, clinical application of EIT is hindered by difficulties in interpreting the resulting images. One source of this difficulty is the frequent use of simple shapes which do not correspond to the anatomy to reconstruct EIT images. The mismatch between the true body shape and the one used for reconstruction is known to introduce errors, which to date have not been properly characterized. In the present study we…
Application of Genetic Algorithms to 3-D Shape Reconstruction in an Active Stereo Vision System
2001
In this paper, a new method for reconstructing 3-D shapes is proposed. It is based on an active stereo vision system composed of a camera and a light system which projects a set of structured laser rays on the scence to be analyzed. The depth information is provided by matching the laser rays and the corresponding spots appearing in the image. The matching task is performed by using Genetic Algorithms (GAs). The process converges towards the optimum solution which proves that GAs can effectively be used for this problem. An efficient 3-D reconstruction method is introduced. The experimental results demonstrate that the proposed approach is stable and provides high accuracy 3-D object recons…
Transillumination imaging through biological tissue by single-pixel detection
2015
One challenge that has long held the attention of scientists is that of clearly seeing objects hidden by turbid media, as smoke, fog or biological tissue, which has major implications in fields such as remote sensing or early diagnosis of diseases. Here, we combine structured incoherent illumination and bucket detection for imaging an absorbing object completely embedded in a scattering medium. A sequence of low-intensity microstructured light patterns is launched onto the object, whose image is accurately reconstructed through the light fluctuations measured by a single-pixel detector. Our technique is noninvasive, does not require coherent sources, raster scanning nor time-gated detection…
Long axial crystals for PET applications: The AX-PET demonstrator and beyond
2013
The usage of long, axially oriented scintillator crystals in a PET scanner has been shown by the AX-PET Demonstrator as a possible solution for a high resolution and high sensitivity PET detector. In the AX-PET implementation, arrays of wavelength shifting (WLS) strips, placed orthogonally behind every crystal layer, are used to define the axial coordinate. After extensive characterization measurements, the AX-PET Demonstrator has been successfully used for the reconstruction of several phantoms and a few rodents. Possible extensions of the AX-PET concept towards Time Of Flight capabilities have been investigated, using Philips digital SiPMs as alternative photodetector. Promising CRT value…
Iterative Reconstruction of Memory Kernels.
2017
In recent years, it has become increasingly popular to construct coarse-grained models with non-Markovian dynamics to account for an incomplete separation of time scales. One challenge of a systematic coarse-graining procedure is the extraction of the dynamical properties, namely, the memory kernel, from equilibrium all-atom simulations. In this article, we propose an iterative method for memory reconstruction from dynamical correlation functions. Compared to previously proposed noniterative techniques, it ensures by construction that the target correlation functions of the original fine-grained systems are reproduced accurately by the coarse-grained system, regardless of time step and disc…
Genetic algorithms for 3d reconstruction with supershapes
2009
Supershape model is a recent primitive that represents numerous 3D shapes with several symmetry axes. The main interest of this model is its capability to reconstruct more complex shape than superquadric model with only one implicit equation. In this paper we propose a genetic algorithms to re-construct a point cloud using those primitives. We used the pseudo-Euclidean distance to introduce a threshold to handle real data imperfection and speed up the process. Simulations using our proposed fitness functions and a fitness function based on inside-outside function show that our fitness function based on the pseudo-Euclidean distance performs better.
An Island Strategy for Memetic Discrete Tomography Reconstruction
2014
In this paper we present a parallel island model memetic algorithm for binary discrete tomography reconstruction that uses only four projections without any further a priori information. The underlying combination strategy consists in separated populations of agents that evolve by means of different processes. Agents progress towards a possible solution by using genetic operators, switch and a particular compactness operator. A guided migration scheme is applied to select suitable migrants by considering both their own and their sub-population fitness. That is, from time to time, we allow some individuals to transfer to different subpopulations. The benefits of this paradigm were tested in …