Monte Carlo simulation of bowtie filter scatter on a wide-cone low-dose CT system

Abstract

Knowledge of scatter generated by bowtie filter is crucial for providing artifact free images on the wide-cone low-dose CT scanners. We investigate and determine the scatter level and artifact generated by the widely used bowtie filter in a wide-cone low-dose CT system. Our approach is to use Monte Carlo simulation to estimate the scatter level generated by a bowtie filter made of a material with low atomic number. First, major components of CT systems, such as source, prepatient collimator, flat filter, bowtie filter, body phantom, and an optional post patient collimator (anti-scatter grid), are built into a 3D model. The scattered photon fluence and the primary transmitted photon fluence are simulated by MCNP5 - a Monte Carlo simulation toolkit. With the increased interests in the low dose and wide coverage CT technology, a tube potential of 80 kVp with more than 10 degree of cone angle is selected. The biased sinogram is created by superimposing scatter signal generated by the bowtie filter onto the primary x-ray beam signal. Finally, images with artifacts are reconstructed with the biased signal. Methods to reduce bowtie filter scatter are also discussed and demonstrated.