Date(s) - 06/19/2014
Purpose: Compton backscatter imaging (CBI) has been successfully used for industrial applications for last four decades, and shows potential for use in medical applications. The purpose of this study was twofold. First, systematically analyze effects of system design parameters on image quality to facilitate design of a CBI system, which will yield better images for medical applications than current generation industrial systems. Secondly, design a simulated detector collimation system and filter algorithm, such that imaging data collected from a single view angle can be post-processed to provide sufficient 3D anatomical detail to be of use in medical applications.
Method: Segmented detectors and energies between 20 keV and 1.5 MeV were simulated using MCNPX, a Monte Carlo transport code. The effects of these parameters on noise, subject contrast, spatial resolution, penetrability, and dose were analyzed. A forward model, which is a mathematical model to predict the signal to the detectors based on radiation absorption and scatter principles, was developed in C++. To validate the model, results of the forward model were compared to MCNPX results. Finally, the forward model was utilized to simulate the collimator design and a C++ based post-processing algorithm.
Results: X-ray tubes with peak tube voltage between 160 to 180 kVp were recommended, with filtration to remove x-rays below 25 keV. The larger detectors were preferred as they provide better SNR and Penetrability, but the increase in SNR was marginal beyond 14 cm detector width. For energies above 35 keV, the forward model showed less than 1% difference to MCNPX results for all the phantoms tested. The simulated detector collimation system and iterative post-processing algorithm showed that CBI systems are capable of obtaining 3D information without rotating the machine.