7. Roshanak Etemadpour, PhD

Multi-layer flat-panel detectors can provide a variety of improvements in clinical x-ray image-guided radiotherapy applications from visualizing soft tissue to reducing image artifacts. Each imager layer captures distinct energy spectra from the same source beam, with each layer acting as a filter, hardening the x-ray spectrum, for subsequent layers. The subsequent readouts of each layer can then be combined for multi-energy analysis to identify, enhance, or suppress specific materials in reconstructed images. This study focuses on optimizing a dual-layer kV imager (DLI) design to achieve effective energy separation. Here we use a single 140 kVp x-ray spectrum and simultaneously capture high- and low-energy images, on bottom and top imager layers, respectively. To optimize energy separation, the variation of the thickness of the scintillator layers and insertion of an inter-layer filter have been studied. The DLI model was simulated in GEANT4 Application for Tomographic Emission (GATE) Monte Carlo software. Our results show that by increasing the thickness of the top and bottom layers of the imager to 1 mm (initially 0.700 mm and 0.800 mm, respectively), energy separation improved by 20.7%. In addition, inserting a thin aluminum filter of 0.3 mm increases the separation more by 22.2%. On the other hand, the results demonstrate that by only adding the filter layer while keeping the layers’ thicknesses unchanged results in only a 12% improved energy separation. In summary, we have successfully built a Monte Carlo simulation tool to calculate energy separation in dual-layer flat-panel detectors. The results will be used in the design of a novel DLI with our industry partners.