Appearance: The headcheese sign on chest CT is characterized by the juxtaposition of lobular regions of low, normal, and high attenuation.1 This results in 3 (or more) different densities on CT that are sharply demarcated from each other. The abrupt density transitions reflect the margins of secondary pulmonary lobules. Low attenuation lobules almost always reflect air trapping, which can be co...

For PET/CT, fast CT acquisition time can lead to errors in attenuation correction, particularly at the lung/diaphragm interface. Gated 4D PET can reduce motion artifacts, though residual artifacts may persist depending on the CT dataset used for attenuation correction. We performed phantom studies to evaluate 4D PET images of targets near a density interface using three different methods for at...

The gamma-ray attenuation porosity evaluator (GRAPE) component of the multisensor track (MST) unit on board the JOIDES Resolution measures the saturated bulk density of sediments by relating the attenuation of gamma rays in a core sample to that of a standard with known density (aluminum). After reaching thermal equilibrium, unsplit core sections are routinely run through the MST system. The sa...

Introduction: The performance of computed tomography is routinely checked using phantoms, which are known as important diagnostic imaging tools. Depending upon the aim of the study, different phantoms are designed, while trying to satisfy certain levels of diversities in their application. Material and Methods: The present study describes the...

background: biological shielding of nuclear reactors has always been a great concern and decreasing the complexity and expense of these installations is of great interest. in this study, we used datolite and galena (daga) minerals for production of a high performance heavy concrete. materials and methods: datolite and galena minerals which can be found in many parts of iran were used in the con...

Two concepts of plane waves in anisotropic viscoelastic media are studied. One of these concepts allows for the use of methods based on the theory of complete Bernstein functions. This allows for a deeper study of frequency-domain asymptotics of the attenuation function and timedomain regularity at the wavefronts. A relation between the direction of the energy flux density and the attenuation v...

in this paper satellite wave propagation at ku and ka band is considered. the design and simulation of a typical satellite beacon receiver at ka band is designed and simulated for the future works. also rain attenuation prediction at ku band using satellite signal beacon measurement and simulations for iran telecommunication research center (itrc) are presented. the measurement setup consists o...

Background: Lead glass has a wide variety of applications in radiation protection. This study aims to investigate some characteristics of lead glass such as the γ-ray energy-dependent mass and linear attenuation coefficients, the half-value layer thickness, and the absorbed dose distribution for specific energy. Materials and Methods: The attenuation parameters of different lead glass types aga...

The performance of the energy density control algorithm for controlling a broadband noise is evaluated in a one-dimensional enclosure. To avoid the noncausality problem of the control filter, which often happens in a frequency domain optimization, analyses presented in this paper are undertaken in the time domain. This approach provides the form of the causally constrained optimal controller. N...