Coherent scatter computed tomography (CSCT) – a Monte Carlo simulation study

Abstract

The open-source Monte Carlo code system Electron Gamma Shower 5 (EGS5) was utilized to investigate coherent (Rayleigh) scatter computed tomography (CSCT). EGS5 was used to generate simulated scatter patterns from homogeneous and heterogeneous phantoms in both a pencil-beam and segmented fan-beam geometry. EGS5 was validated by using a polyen- ergetic molybdenum spectrum in a pencil-beam geometry to verify that simulated scatter profiles produced by water, beef fat, and beef match those produced in the laboratory; pro- files were found to be in good agreement based on statistical measures of the goodness-of-fit. EGS5 was then used to investigate coherent scatter computed tomography (CSCT) for a fan-beam geometry. Both mono- and polyenergetic x-ray spectrums were used to generate scatter photons from heterogeneous phantoms. Filtered back projection (FBP) was used to reconstruct CSCT and traditional attenuation based images from simulated data. It was demonstrated that by combining images reconstructed from selected scatter angles, images could be created that selectively suppressed and/or enhanced a specific component material. Through the use of CTDI100 measurements, simulation techniques were roughly equated to clinical CT scanner techniques. Additionally, a potentially new hypothetical reconstruction method was illustrated, termed single shot coherent scatter computed tomography, which permitted the reconstruction of a tomogram from scatted photon data obtained from a single acquisition view angle. This method was dependent upon an idealized detector that can record both position and direction of photon travel upon detection. Overall, it was concluded that EGS5 provides an accurate simulation of coherent scatter, and may be used to investigate the parameter space for CSCT.