Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy’s cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy’s condition was derived for an attenuation-free situation, we hypot...

One of the main components in a Calypso 4D localization and tracking system is an electromagnetic array placed above patients that is used for target monitoring during radiation treatment. The beam attenuation and beam spoiling properties of the Calypso electromagnetic array at various beam angles were investigated. Measurements were performed on a Varian Clinac iX linear accelerator with 6 MV ...

Several SeaWiFS products have been compared with shipboard data to assess the possibility of using remote sensing to estimate particulate organic carbon (POC) concentration in surface waters. Transmissometer data were collected during six South Atlantic Ventilation Experiment (SAVE) hydrographic expeditions conducted between November 1987 and March 1989 from R/V Knorr, and Melville. A total of ...

The relationships between beam attenuation spectra, chlorophyll and pheophytin pigment concentrations, and particle size distributions are examined for a coastal region (Monterey Bay area) believed to have negligible concentrations of terrestrially derived dissolved organic compounds (during May 1977) but large quantities of phytoplankton and resuspended sediments. It was found that the slope o...

The purpose of this study was to evaluate beam attenuation by treatment couch and build a treatment couch model in TPS to check for beam-couch intersection at the planning stage and deal with beam attenuation by treatment couch in dose calculation. In this study, a standard treatment couch, Siemens ZXT couch, has been incorporated into Pinnacle3 8.0 TPS, based on an existing TPS tool, model-bas...

Using three-dimensional Monte Carlo radiative transfer simulations, we examine the effect of beam transmissometer geometry on the relative error in the measurement of the beam-attenuation coefficient in an aquatic environment characterized by intense light scattering, especially within submerged bubble clouds entrained by surface-wave breaking. We discuss the forward-scattering error associated...

Introduction: The present study aimed to evaluate the impact of PbO nano and micro-sized fillers on ordinary and heavy concretes for different photon energies. Material and Methods: The MCNPX Monte Carlo code (version 2.6.0) was used for all simulations in the present study. A model of narrow-beam geometry was validated and utilized to calcul...

background: in this study, a method for linear attenuation coefficient calculation was introduced. methods: linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. the calculation was done for cerrobend as a common radiotherapy modifier and mercury. results: the valu...

The detection and prediction of changes in coastal ecosystems require a better understanding of the complex physical, chemical and biological interactions, which involves that observations should be performed continuously. For this reason, there is an increasing demand for small, simple and cost-effective in situ sensors to analyze complex coastal waters at a broad range of scales. In this cont...

Introduction: MRI-only treatment planning (TP) can be advantageous in paediatric radiotherapy. However, electron density extraction is necessary for dose calculation. Normally, after bone segmentation, a bulk density is assigned. However, the variation of bone bulk density in patients makes the creation of pseudo CTs challenging. This study aims to assess the effects of bone den...