Analytical Calculation of the Compton Single Scatter Component of Pencil Beam Scatter Kernel for Scatter Correction in kV Cone Beam CT (kV-CBCT)

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.

Virtual Clinical Trials in 2D and 3D X-ray Breast Imaging and Dosimetry: Comparison of CPU-Based and GPU-Based Monte Carlo Codes

“…They are very efficient computationally, but they usually do not consider scattered photons, whose effect is often considered ex post as an image pattern that is superimposed on the primary transmitted 2D image [ 3 , 4 , 5 , 6 ], for example analytical models for the simulation of single scatter events in cone beam CT have been developed (e.g., ref. [ 7 ]). On the other hand, Monte Carlo (MC) simulation techniques intrinsically model both the primary and scattered photon beams.…”

“…They are increasingly adopted for breast imaging and dosimetry studies as they represent the solution of choice for imaging simulations in breast VCTs [ 1 ]. An example is the VICTRE project (Virtual Imaging Clinical Trials for Regulatory Evaluation) [ 7 ], a large VCT study comparing the performance of digital breast tomosynthesis (DBT) with respect to digital mammography (DM), for breasts with different anatomical characteristics.…”