A method of operating a radiation imaging system includes applying a bias voltage to a top electrode, receiving ionization radiation, wherein the ionization radiation penetrates an electrical insulation layer and generate a charge signal, storing the charge signal in a storage capacitor among a plurality of storage capacitors, changing a polarity of a gate line bias voltage of one row of transistors among a plurality of transistors, and integrating charges from storage capacitors connected to each other along orthogonal data lines. The imaging system includes an electrical insulation layer having a top surface and a bottom surface, a top electrode on the top surface of the electrical insulation layer, a plurality of pixel units electrically coupled to the electrical insulation layer, the plurality of pixel units including a plurality of storage capacitors, and a plurality of transistors connected to the plurality of pixel units such that a respective transistor is connected to each of the plurality of pixel units.