A simulation framework for pre-clinical studies on dose and image quality: concept and first validation

Abstract

Purpose: The purposes of the study were to set-up and validate a simulation framework for dose and image quality optimization studies. In a first phase we have evaluated whether CDRAD images as obtained with computed radiography plates could be simulated. Material and Methods: The Monte Carlo method is a numerical method that can be used to simulate radiation transport. It is in diagnostic radiology often used in dosimetry, but in present study it is used to simulate X-ray images. With the Monte Carlo software, MCNPX, the successive steps in the imaging chain were simulated: the X-ray beam, the attenuation and scatter process in a test object and image generation by an ideal detector. Those simulated images were further modified for specific properties of CR imaging systems. The signal-transfer-properties were used to convert the simulated images into the proper grey scale. To account for resolution properties the simulated images were convolved with the point spread function of the CR systems. In a last phase, noise, based on noise power spectrum (NPS) measurements, was added to the image. In this study, we simulated X-ray images of the CDRAD contrast-detail phantom. Those simulated images, modified for the CR-system, were compared with real X-ray images of the CDRAD phantom. All images were scored by computer readings. Results: First results confirm that realistic CDRAD images can be simulated and that reading results of series of simulated and real images have the same tendency. The simulations also show that white noise has a large influence on image quality and CDRAD analyses.