In positron emission tomography, transmission scans are used to correct the acquired data for the effect of photon attenuation. The noise present in the transmission measurement often has a significant effect on the signal to noise ratio of the final attenuation corrected image of the tracer distribution. This study evaluates the effect of different attenuation correction strategies on the perf...

Mass attenuation coefficients of the some elements were determined for two photon energies using different three detectors. The samples were irradiated using 10 mCi Cd-109 and 100 mCi Am-241 radioactive point sources. The photons were separately counted by Si(Li), NaI(Tl) and Cd(Tl) detectors. It was observed that the mass attenuation coefficient decreases with increasing energy and increases w...

This study is concerned with the use of the concrete samples produced by tincal concentrator waste as a gamma radiation shield. The values of mass attenuation coefficients for concrete samples measured at 59.54 (Am-241) and 80.99 (Ba-133) keV photon energies. Gamma rays were counted by a NaI(Tl) detector coupled to multi channel analyzer (MCA) using narrow beam transmission arrangement. Theoret...

The total mass attenuation coefficients (μ t ) (cm(2)/g) and atomic, molecular, and electronic effective cross sections have been calculated for nonessential amino acids that contain H, C, N, and O such as tyrosine, aspartate, glutamine, alanine, asparagine, aspartic acid, cysteine, and glycine in the wide energy region 0.015-15 MeV. The variations with energy of total mass attenuation coeffici...

osting by E Abstract The variation of photon attenuation coefficient on the chemical media has been investigated. For this purposes the linear attenuations of barite concrete have been measured at 662, 1773 and 1332 keV before leaving the chemical media and following a 6 month period. The linear attenuation coefficients have been measured using gamma spectrometer that contains a NaI(Tl) detecto...

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head-scatter factor) and off-axis position (primary off-axis ratio). These parameters are normally measured "in air" with a build-up cap thick enough to generate full dose build-up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it has been...

This work deals with the single photon emission computed tomography (SPECT) reconstruction process. As a SPECT measurement also depends on unknown attenuation properties of the tissue, such a process is challenging. Furthermore, the given attenuation may not be a good approximation to the true attenuation field. Reasons are repositioning or movement of the patient such as relaxation during scan...

Objective: In this study, we aimed to validate the accuracy of computed tomography-based attenuation correction (CTAC) using the bilinear scaling method.Methods: The measured attenuation coefficient (μm) was compared to a theoretical attenuation coefficient (μt ) using four different CT scanners and an RMI 467 phantom. The effective energy of the CT beam X-rays was calculated, using the aluminu...

An idealized model of an optical communication link in which identical sections of nonlinear attenuating 6ber alternate with identical amplifiers is considered. Signal-to-noise ratios of chains of these elements for input squeezed and coherent light have been numerically evaluated. It is found that input squeezed light and nonlinear attenuators improve the signal-to-noise ratios with respect to...