TITLE:
Analytical Calculation of the Compton Single Scatter Component of Pencil Beam Scatter Kernel for Scatter Correction in kV Cone Beam CT (kV-CBCT)
AUTHORS:
Jie Liu, J. Daniel Bourland
KEYWORDS:
Scatter Correction, Cone Beam CT, Beam Scatter Kernel, Compton Scatter, Single Scatter
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.7 No.2,
May
28,
2018
ABSTRACT: The accuracy of conventional superposition or
convolution methods for scatter correction in kV-CBCT is usually compromised by
the spatial variation of pencil-beam scatter kernel (PBSK) due to finite size,
irregular external contour and heterogeneity of the imaged object. This study
aims to propose an analytical method to quantify the Compton single scatter
(CSS) component of the PBSK, which dominates the spatial distribution of total
scatter assuming that multiple scatter can be estimated as a constant
background and Rayleigh scatter is the secondary source of scatter. The CSS
component of PBSK is the line integration of scatter production by incident
primary photons along the beam line followed by the post-scattering attenuation
as the scattered photons traverse the object. We propose to separate the
object-specific attenuation term from the line integration and equivalently
replace it with an average value such that the line integration of scatter
production is object independent but only beam specific. We derived a quartic
function formula as an approximate solution to the spatial distribution of the unattenuated
CSS component of PBSK. The “effective scattering center” is introduced to
calculate the average attenuation. The proposed analytical framework to
calculate the CSS was evaluated using parameter settings of the On-Board Imager
kV-CBCT system and was found to be in high agreement with the reference
results. The proposed method shows highly increased computational efficiency
compared to conventional analytical calculation methods based on point
scattering model. It is also potentially useful for correcting the spatial
variant PBSK in adaptive superposition method.