Reliable attenuation correction methods in PET require accurate determination of the attenuation map (μmap), which represents the spatial distribution of linear attenuation coefficients (LACs) at 511 keV for the region under study. Since CT image pixel intensities are directly related to the LAC of the corresponding tissue calculated from the effective CT energy, the μmap at 511 keV can be dire...

We have theoretically studied the ultrasonic attenuation of heavily doped semiconductors with a single-valley or a many-valley in the weakly localized regime. The following has been found. A contribution from quantum correction terms to the attenuation coefficient Aa decreases with increasing temperature. In the many-valley case Aa decreases with increasing the strength of the intervalley scatt...

An attenuation-correction algorithm for the SeaWinds instrument uses the AMSR brightness temperature to find the attenuation experienced by the scatterometer signal. The algorithm uses the concept of excess temperature TeXto evaluate the attenuation. The excess temperature TeXis the difference between the measured brightness temperature and the temperature of the emitting surface. ~e algorithm ...

PURPOSE To explore the feasibility of improving cross-sectional reflection imaging of the breast using refractive and attenuation corrections derived from ultrasound tomography data. METHODS The authors have adapted the planar Kirchhoff migration method, commonly used in geophysics to reconstruct reflection images, for use in ultrasound tomography imaging of the breast. Furthermore, the autho...

Introduction: Scattered photon is one of the main defects that degrade the quality and quantitative accuracy of nuclear medicine images. Accurate estimation of scatter in projection data of SPECT is computationally extremely demanding for activity distribution in uniform and non-uniform dense media. Methods: The objective of this paper is to develop and validate a scatter correction technique ...

In this paper procedures for estimating the sound absorption coefficient when the specimen has inherently low absorption are discussed. Examples of this include the measurement of the absorption coefficient of pavements, closed cell foams and other barrier materials whose absorption coefficient is nevertheless required, and the measurement of sound absorption of muffler components such as perfo...

To evaluate the usefulness of a combination of linearization and scatter-attenuation correction on 99mTc-bicisate (ECD)-single photon emission tomographic (SPECT) images, both cerebral blood flow (CBF)-positron emission tomographic (PET) images and ECD-SPECT images from fifteen patients with chronic cerebral infarction were acquired. We measured radioactivity counts in regions of interest (ROIs...

The ‘Simultaneous Maximum-Likelihood Attenuation Correction Factors’ (sMLACF) algorithm presented here, is an iterative algorithm to calculate the maximum-likelihood (ML) estimate of the activity λ and the attenuation correction factors a in time-of-flight (TOF) positron emission tomography (PET), and this from emission data only. sMLACF is derived using the expectation-maximization (EM) princi...

Objective(s): The aim of this study was to determine the optimal reconstruction parameters for iterative reconstruction in different devices and collimators for dopamine transporter (DaT) single-photon emission computed tomography (SPECT). The results were compared between filtered back projection (FBP) and different attenuation correction (AC) methods.Methods: An anthropomorphic striatal phant...

A general purpose Gamma Box Counter is a large scale, high-resolution segmented gamma-ray nondestructive assay system for the assay of nuclear waste containers covering a wide range of composition, mass, and geometry. In order to accurately quantify the activity of the radionuclides in a waste container, a correction for the gamma-ray self-attenuation in the waste matrix must be estimated and a...