The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Motion compensation in PET imaging has become more and more important for obtaining high-resolution images. PET emission image and patient motion can be estimated simultaneously from gated data through a joint estimation framework. The resulting optimization problem, however, is challenging to solve. We propose an efficient algorithm for joint estimation by using the optimization transfer with the...
Direct positron emission tomography (PET) reconstruction has been developed for acquiring accurate parametric imaging from raw measurement. Direct reconstruction estimates physiological kinetic parameters in iterative reconstruction process that contains two steps such as updating dynamic images and calculating nonlinear least square (NLS) parameter fitting. Although the quality of dynamic images...
We introduce the first ever ordered subset expectation maximization (OSEM) method for joint estimation of emission activity distribution and photon attenuation map from positron emission tomography (PET) emission data alone. It differs from standard OSEM in the use of distinct-, as opposed to identical subsets for emission activity distribution- and photon attenuation map update. The method accelerates...
Extracting prior knowledge from previous high quality normal-dose computed tomography (NdCT) data for Bayesian reconstruction of current low-dose CT (LdCT) images has attracted great research interests recently. While most efforts focused on registering the previous NdCT data to the current LdCT reconstruction, this work investigated an alternative strategy by extracting the local structure-specific...
PET reconstruction results in images with correlations between neighbouring image voxels. Alternative reconstruction algorithms, such as OSEM reconstruction incorporating resolution modelling (RM) can significantly alter this voxel covariance. While RM has been demonstrated to reduce voxel variance, it has been suggested that the increased covariance results in increased region-based ensemble variance...
Attenuation correction is critical to accurate PET quantitation. However, it is challenging to extract accurate attenuation from MR data because of distinct physics of MR and PET. The goal of this study is to achieve robust and accurate attenuation correction in PET/MR. We combine an MR-segmentation based approach and a joint estimation approach synergistically by using an MR-segmentation based attenuation...
Low count PET studies usually suffer from high image noise and quantitative bias in reconstructed image. This is particularly significant for short frames (temporal-ROI, or TROI) in dynamic PET studies, which in some cases may be as short as 30 seconds or less. In this paper, we proposed a method to improve the quality of the reconstructed short frame by utilizing information from a longer acquisition...
In order to detect the deformations and monitor inner structures during operation more effectively, an innovative CT system making use of the objects' self-rotation is designed by us. However, some parts remain static and they contaminate the reconstruction image with ring artifacts. In this paper, we put forward a method taking advantage of limited-angle scan to get the prior image, then using interactive...
Biomedical signal processing is important for biologists and physicians. Because of the speciality and complexity of biomedical signals, they bring about many substantial troubles for the mathematical methods to deal with. In this paper, we discuss the tracking and reconstructing of sharp spikes of biomedical signals by exploring the new possibility for the applications of tracking-differentiators...
This paper proposes a novel photometric stereo method for reliable reconstruction of non-Lambertian object surfaces based on color and noise analysis. Unlike previous techniques that treat highlight pixels as outliers, the proposed method utilizes the intrinsic shape cue in those pixels by robust reflection separation. Image noise is estimated from two photometric images instead of a single one, thus...
Urban reconstruction from a video captured by a surveying vehicle constitutes a core module of automated mapping. When computational power represents a limited resource and, a detailed map is not the primary goal, the reconstruction can be performed incrementally, from a monocular video, carving a 3D Delaunay triangulation of sparse points; this allows online incremental mapping for tasks such as...
Compact polarimetry is a hybrid polarity imaging mode. In this study, we propose a new algorithm based on least-squares (LS) error to estimate the quad-pol coherency elements. Different from the existing quad-pol reconstruction methods, the proposed method can be directly applied to the single look complex compact data, while all the other existing algorithms are based on the multi-look speckle reduced...
In urban areas, the reconstruction of gable-roof buildings from high-resolution synthetic aperture radar (SAR) images is more challenging compared to simple parallelepiped buildings. In this paper, an alternate iteration and matching technique is proposed for height and roof inclination angle estimation of gable-roof buildings. First, the different appearances of this building type in SAR images are...
Combined with digital beam forming (DBF), multichannel synthetic aperture radar (MC-SAR) in azimuth can achieve high-resolution and wide-swath (HRWS) SAR imaging. However, inevitable channel errors lead to a great degradation of DBF performance in practice. To address this problem, a novel channel phase error calibration algorithm is proposed in this letter. Theoretical analysis reveals that the signal...
Parallel MRI is a fast imaging technique that allows reconstruction of full Field-of-View (FoV) images based on under-sampled k-space data acquired using multiple receiver coils with complementary sensitivity profiles. It enables the acquisition of highly resolved images either in space or time, which is of particular interest in applications like functional neuroimaging. These features are counterbalanced...
The traditional CRT based algorithms have been proposed to solve the problem of range estimation with multi-frequency phase unwrapping, where the wavelengths of the multi-frequency signals should to be pair-wisely co-prime after they are divided by their greatest common divisor (GCD). To get a robust reconstruction result, the upper bound of the remainder errors should be smaller than a quarter of...
The so-called direct SLAM methods have shown an impressive performance in estimating a dense 3D reconstruction from RGB sequences in real-time [1], [2], [3]. They are based on the minimization of an error function composed of several terms that account for the photometric consistency of corresponding pixels and the smoothness and the planarity priors on the reconstructed surfaces. In this paper we...
This paper proposes a direct monocular SLAM algorithm that estimates a dense reconstruction of a scene in real-time on a CPU. Highly textured image areas are mapped using standard direct mapping techniques [1], that minimize the photometric error across different views. We make the assumption that homogeneous-color regions belong to approximately planar areas. Our contribution is a new algorithm for...
This paper proposed an improved threshold function and threshold estimation method for analyzing the characteristics of the wavelet threshold denoising. Because hard threshold denoising makes boundaries fuzzy and soft threshold denoising has Gibbs phenomenon, the new threshold function and estimation method have better adaptive. Results show that the improved method can effectively remove the white...
Autofocusing is one of the key steps in the high-resolution SAR imaging. In the paper several important improvements to the recently developed local-quadratic map-drift autofocus are proposed. Important SAR image preprocessing steps applied before the local Doppler rate errors estimation are described. The weighting scheme for the evaluation of residual cross-track acceleration components is developed...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.