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SU‐E‐I‐116: Spatial Frequency Spectrum of the X‐Ray Scatter Distribution in CBCT
Author(s) -
Bootsma G,
Verhaegen F,
Jaffray D
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3611690
Subject(s) - spatial frequency , optics , monte carlo method , projection (relational algebra) , fourier transform , filter (signal processing) , physics , cone beam computed tomography , noise (video) , photon , image quality , spatial filter , mathematics , computer science , statistics , artificial intelligence , image (mathematics) , algorithm , computer vision , computed tomography , medicine , radiology , quantum mechanics
Purpose: X‐ray scatter causes significant diminishing effects to image quality in cone‐beam CT (CBCT) such as: image artifacts, loss in contrast‐ to‐noise ratio, and CT number inaccuracy. The purpose of this study is to examine the spatial frequency content of the scatter distribution in CBCT projection images using the Fourier transform. This work forms the basis for accelerated Monte Carlo scatter estimation. Methods and Materials: A previously validated CBCT MC system is used to generate the resulting scatter distribution for various imaging sites (head and neck, abdomen, and pelvis) and projection angles using a voxelized anthropomorphic phantoms. The spatial frequency is examined by taking the fast Fourier transform (FFT) of the simulated scatter distributions. The effects of using a bowtie filter on the spatial frequencies of the scatter distribution is also examined. Results: The spatial frequency of the scatter distribution, in the horizontal and vertical direction, is largely contained in the lower frequencies of the Fourier transform (<0.1 1/cm). The angular component of the spatial frequency of scatter distribution shows two strong periodic signals with a period of pi and pi/2. The use of the bowtie filter has an effect of decreasing the higher frequency content of the horizontal component of the spatial frequency. Conclusions: The computational time of estimating the scatter distribution using MC can be reduced by simulating fewer photons and using a low‐pass filter. Periodic signals in the projection angle component of the scatter distribution indicate that a significant reduction in number of projection angles simulated to accurately estimate the scatter distribution is also possible.