A novel concept of adjustable three-layer collimator in a pixelated photon-counting detector for gamma-ray imaging: Monte Carlo simulation study

Abstract

In gamma-ray imaging, a collimator plays a crucial role in determining the sensitivity of the system and the spatial resolution of the acquired image. Herein, we presented a novel concept for a variable collimator in a pixelated photon-counting detector. The gamma-ray imaging system was modeled using the Monte Carlo simulation tool Geant4 Application for Tomographic Emission program. A detector using cadmium telluride and a 99mTc point source was used. The collimators comprised three tungsten layers, and the septal height the beam finally penetrated from the incident gamma ray was adjusted differently. The first collimator layer constituted a hole with four times the pixel size, and the second and third layers comprised a hole with twice the pixel size, overlapping asymmetrically. Finally, the emitted gamma ray equaled the pixel. The spatial resolution showed different results depending on the source-to-collimator distance for each collimator configuration. Additionally, we determined that the sensitivity improved as the collimator height where gamma rays are incident and initially interact increased. We have proposed a novel collimator concept in a gamma-ray imaging system using a pixelated photon-counting detector, which may be applied in various fields in the future.