Evaluation of scatter suppression algorithm for X-ray exposure of soft tissue equivalent phantoms over nominal energy range using FLUKA code

Abstract

Soft tissue imaging is heavily impaired by streaks and cupping effects associated with X-ray scatter. Quality of images from projection imaging may be improved by the use of enhanced anti-scatter grids’ designs with potency to reject significant scatter. However, optimization of grid characteristics requires investigation to improve diagnostic image quality. Transmitted scatter spatially distributed degrades images engendering need for effective scatter correction protocols. This study investigated the pre-scan scatter suppression algorithm for X-ray exposure of soft tissue equivalent phantoms over nominal energy range. Adipose tissue and polymethyl methacrylate phantoms of cross-sectional area (30 x 30) cm² and of varying thickness from 2 to 8 cm in 1 cm increments were successively exposed using energy ranging between 20–50 kVp. Monte Carlo simulation based on FLUKA code and flair interface was used to generate an input file for execution. The source simulated five cycles of ten million photons each of annular X-ray photon beam of radius, r = 0.5 cm at fixed field of view (FOV) through anti-scatter grid on to gadolinium oxysulfide detector. The transmitted total, scatter and primary estimates were evaluated with and without grids over varying phantom thicknesses, energy and grid design features. The simulated and experimental results obtained were comparable and in agreement with previous literature. Pearson’s correlation coefficients for scatter fraction and scatter to primary ratio were 0.983 and 0.981, respectively. The strong correlation between simulation and experiment results indicated correctness in methodology and protocol. The algorithms and protocols in the simulation would be appropriate for designing grids with enhanced scatter rejection capabilities.

Keywords: FLUKA code, Monte Carlo simulation, Scatter suppression algorithm, Scatter correction, X-ray imaging systems.