Design considerations for efficient binary megavoltage photon detector structures

In this work, Monte Carlo methods are used for the design of highly efficient detector structures for megavoltage X-ray imaging. The detector structures consist of a converter material and an active medium ("binary" detector systems). The novel approach is to impose a spatial structure on the converter material that intersperses the active medium and defines the size of a detector cell. The dimensions of these structures have to be optimized with respect to efficiency and spatial resolution. The results show that the quantum efficiency and detective quantum efficiency at zero frequency of such structures surpass the efficiency of conventional detector structures using the converter material as a buildup layer and depend on the dimensions of the converter structure and the active medium as well as the materials itself. In general, larger converter structures result in a higher efficiency. The detector signal is proportional to the size of the active medium in the cell. However, the size of the structures are limited by the specifications for the desired spatial resolution.