<title>Effects of scattered x-rays on cone-beam CT images</title>

Abstract

Scatter to primary radiation ratios at detector positions were calculated for spherical water phantoms in the cone-beam xray 3-D CT scanner using the Monte Carlo simulation method. In the Monte Carlo simulation, 1x106 photons of conebeamed 120-ky polyenergetic x-rays with the filter of4mm Al have been traced individually as these photons interact within the phantoms with diameters 15cm and 20cm. The decrease in CT number due to scatter was found to be about 100. In the process of image reconstruction, the effect of scatter was isolated by applying our new calculation technique. 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.

Quantitative measurement of gas hold-up distribution in a stirred chemical reactor using X-ray cone-beam computed tomography

“…A known method to cope with scattered radiation is to obtain the intensity profile of scattered radiation and to correct the radiographic image or projection data by that amount. Suggested estimation techniques are Monte-Carlo simulations (Inoue [38]) and deconvolution calculations (Seibert [39]). Another approach is the indirect estimation of scatter by incorporation of an additional radiographic measurement, which should give an almost scatterfree radiograph of the examined object.…”

<title>Image restoration of cone-beam CT images using wavelet transform</title>

“…Suppose that p(r, £1) is the projection data at beam angle of 9, a cross sectional image is reconstructed by following equation f(x,y) = Lfp(r, 9)h(xcoso +ysinO -r)drdO (6) where h(r) is the response function of filter to reconstruct CT image. As following the multiresolution analysis of wavelet transform, the projection data is decomposed into several multiresolution levels and is written as p(r,O) = p(r,8)+pN)(r,O) (7) where, p and are the detailed and smoothed components, respectively, at level j of multiresolution analysis and given by (j) .1 r p1 (r, 9) …”