Effect of scattered radiation on image noise in cone beam CT

Cone beam CT has a capability for the 3-dimensional imaging of large volumes with isotropic resolution, and has a potentiality for 4-dimensional imaging (dynamic volume imaging), because cone beam CT acquires data of a large volume with one rotation of an x-ray tube-detector pair. However, one of th...

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Bibliographic Details
Published in:Medical physics (Lancaster) 2001-04, Vol.28 (4), p.469-474
Main Authors: Endo, Masahiro, Tsunoo, Takanori, Nakamori, Nobuyuki, Yoshida, Katsuya
Format: Article
Language:English
Subjects:
Applications of Monte Carlo methods
Computed radiography
Computed tomography
computerised tomography
Cone beam computed tomography
Cone beam CT
flat‐panel imager
Head - diagnostic imaging
Humans
Image analysis
image noise
image reconstruction
Medical image noise
medical image processing
Medical image reconstruction
Medical imaging
Medical X‐ray imaging
Models, Statistical
Monte Carlo Method
Monte Carlo methods
noise
scattered radiation
Scattering, Radiation
Tomography, X-Ray Computed - instrumentation
Tomography, X-Ray Computed - methods
X-Rays
X‐ray effects
X‐ray imaging
X‐ray scattering
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Summary:Cone beam CT has a capability for the 3-dimensional imaging of large volumes with isotropic resolution, and has a potentiality for 4-dimensional imaging (dynamic volume imaging), because cone beam CT acquires data of a large volume with one rotation of an x-ray tube-detector pair. However, one of the potential drawbacks of cone beam CT is a larger amount of scattered x-rays, which may enhance the noise in reconstructed images, and thus affect the low-contrast detectablity. Our aim in this work was to estimate the scatter fractions and effects of scatter on image noise, and to seek methods of improving image quality in cone beam CT. First we derived a relationship between the noise in a reconstructed image and in an x-ray intensity measurement. Then we estimated the scatter to primary ratios in x-ray measurements using a Monte-Carlo simulation. From these we estimated the image noise under relevant clinical conditions. The results showed that the scattered radiation made a substantial contribution to the image noise. However, focused collimators could improve it by decreasing the scattered radiation drastically while keeping the primary radiation at nearly the same level. A conventional grid also improved the image noise, though the improvement was less than that of focused collimators.
ISSN:0094-2405
2473-4209
DOI:10.1118/1.1357457