Active pixel sensors for photon counting X-ray detectors

A computed tomography (CT) imaging system, comprising:

• a photon counting detector, comprising:
• at least one detector sub-module, wherein the at least one detector sub-module comprises:
• a semiconductor substrate;
• and
• a plurality of active pixels configured to act as detector elements disposed on the semiconductor substrate;
• and
• a plurality of traces extending from the plurality of active pixels to readout circuitry, wherein each active pixel of the plurality of active pixels is coupled to a respective trace of the plurality of traces, and each active pixel comprises an amplification stage configured to generate an output signal based on a current pulse output generated by the active pixel;
• and
• the readout circuitry configured to directly read out the output signals from the plurality of active pixels, wherein the readout circuitry is separate from the at least one detector sub-module in that the readout circuitry is not located on the semiconductor substrate.

A photon counting detector, comprising:

• at least one detector sub-module, wherein the at least one detector sub-module comprises:
• a semiconductor substrate;
• and
• a plurality of active pixels configured to act as detector elements disposed on the semiconductor substrate;
• and
• a plurality of traces extending from the plurality of active pixels to readout circuitry, wherein each active pixel of the plurality of active pixels is coupled to a respective trace of the plurality of traces, wherein each active pixel is configured to act as a passive integrator, and wherein each active pixel comprises a transconductance amplifier comprising a single transistor configured to generate an output signal based on a current pulse output generated by the active pixel;
• and
• the readout circuitry configured to directly read out the output signals from the plurality of active pixels, wherein the readout circuitry is separate from the at least one detector sub-module in that the readout circuitry is not located on the semiconductor substrate, and wherein the readout circuitry comprises a current source biased to the single transistor.