Effects of scattered x-rays on monoenergetic cone-beam 3D CT images

Scatter to primary radiation ratios at detector positions were calculated for spherical water phantoms in the cone-beam x-ray 3D CT scanner using the Monte Carlo simulation method. In the Monte Carlo simulation, 1 approximately 4 X 106 photons of cone-beamed several monoenergetic x-rays have been traced individually as these photons interact within the phantoms with diameters 10 and 15 cm. In case of the incident photon energies are 72.86 and 68.79 keV, photon spectra at the center of the planar detector system are depicted. The decrease in CT number due to scatter was found to be about 100. The scatter reduces CT numbers in the whole region of images and the intensity of scattered rays is nearly uniform, so that rounded-off image is reconstructed.

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