Physical factors such as photon attenuation degrade image quality and quantitative accuracy in single-photon emission computed tomography (SPECT). It is often considered (especially in situations with non-uniform attenuation and distance-dependent spatial resolution (DDSR)) that adequate compensation for the effects of these physical factors requires data acquired over 2 . However, as the analy...

Context. The unified model of active galactic nuclei (AGN) claims that the properties of AGN depend on the viewing angle of the observer with respect to a toroidal distribution of dust surrounding the nucleus. Both the mid-infrared (MIR) attenuation and continuum luminosity are expected to be related to dust associated with the torus. Therefore, isolating the nuclear component is essential for ...

Many clinical and research studies in nuclear medicine require quantitation of iodine-123 (123I) distribution for the determination of kinetics or localization. The objective of this study was to implement several reconstruction methods designed for single-photon emission computed tomography (SPECT) using 123I and to evaluate their performance in terms of quantitative accuracy, image artifacts,...

The purpose of this study is to systematically evaluate the usefulness of Positron emission tomography/Magnetic resonance imaging (PET/MRI) images in a clinical setting by assessing the image quality of Positron emission tomography (PET) images using a three-segment MR attenuation correction (MRAC) versus the standard CT attenuation correction (CTAC). We prospectively studied 48 patients who ha...

The task of single photon emission CT (SPECT) is to visualize the physiological function of various organs with the help of radiopharmaceuticals. But the projection data used for image reconstruction are distorted by several factors, making the reconstruction of a quantitative SPECT image very difficult in most cases. These factors include the attenuation and scattering of gamma rays, collimato...

PET-CT misalignment has been reported as a source of artefacts in cardiac PET/CT due to a biased photon attenuation correction. Using the data from 28 cardiac PET/CT rest/stress examinations, PETCT misalignment was corrected using three different methods: manual registration, automatic mutual information based image registration and an emission-driven correction algorithm. The clinical effects ...

The aim of this study is to compare the effect of the two major classes of methods used to determine the attenuation map, i.e. non-uniform versus uniform, on 3D brain PET clinical studies based on qualitative assessment as well as absolute and relative quantitative volume of interest (VOI)based analysis. The results revealed statistically significant differences between the six attenuation corr...

The emission spectrum of mercury has a notable line at about 365 nm under both low and medium-high pressure conditions. A simple filter based on a solution of dysprosium ions, Dy(3+), is shown to be very useful for applications of Hg-light sources where this line is unwanted. The presented filter is cheap, robust, and stable towards degradation or bleaching - even under intense irradiation. The...

We discuss the dust attenuation and the star formation rates in the nearby universe obtained from a comparison of far-infrared (IRAS) and ultraviolet (GALEX) observations. The ratio of the dust to UV flux ratio is used to derive the dust attenuation: this dust attenuation is found to increase with the luminosity of the galaxies and from z=0 to z=1. The slope of the UV continuum is found to be a...

Signal processing includes a wide variety of signals, such as 2D and 3D images. New techniques of signal processing are widely accepted in medicine, where inter-modality techniques are today unquestionably required for its use in diagnosis. Tumor or Alzheimer detection requires the use of new radio-pharmaceutical tracers that should be tested in small animals, such as mice or rats. Medical tech...