Optimizing coded aperture imaging techniques to allow for online tracking of fiducial markers using high energy scattered radiation from clinical treatment beam.*

Real time visualization of fiducial markers and their movement as surrogates for tumor motion during radiotherapy treatment allows for more accurate dose delivery. This project aims to optimize techniques for online tracking by detecting the scattered radiation from clinical treatment beams through a coded aperture (CA).

MCNP6 was used to model radiotherapy beams through phantoms containing gold fiducials. Orthogonal scatter radiographs were collected through a CA geometry. After decoding the simulated radiograph data, the centroid location and FWHM/SNR of the fiducial signals were analyzed. The method was able to accurately localize the markers to within <1mm. The effects of the CA/detector parameters (rank, pattern, and physical dimensions), and the incident beam energy were characterized. Fourier filtering was used to reduce the effects of phantom scatter and decoding artifacts.

Current results will present a proof of concept for a novel real-time imaging method which can be used to further optimize the CA imaging parameter space and guide design and testing of a clinical device.