Photon counting detector

A correction device for a photon counting detector, comprising:

• a first signal input configured to obtain a first count signal representing high-energy electromagnetic radiation impinging on a low-absorption direct conversion material of a first direct conversion layer;
• a second signal input configured to obtain a second count signal representing high-energy electromagnetic radiation impinging on a high-absorption direct conversion material of a second direct conversion layer, the high-absorption direct conversion material having a higher absorption than the low-absorption direct conversion material, wherein the first direct conversion layer and the second direct conversion layer are arranged such that the high-energy electromagnetic radiation transmits the first direct conversion layer before the second direct conversion layer;
• and
• processing circuitry configured to correct a drift of the second count signal from the high-absorption direct conversion material, by determining that there is a drift in the second count signal from the high-absorption direct conversion material:
• when there is a change in the second count signal from the high-absorption direct conversion material but no change in the first count signal from the low-absorption direct conversion material;
• or
• when a correlation between the first count signal from the low-absorption direct conversion material and the second count signal from the high-absorption direct conversion material deviates from a reference correlation.

A correction method for a photon counting detector, comprising:

• obtaining a first count signal representing high-energy electromagnetic radiation impinging on a low-absorption direct conversion material of a first direct conversion layer;
• obtaining a second count signal representing high-energy electromagnetic radiation impinging on a high-absorption direct conversion material of a second direct conversion layer, the high-absorption direct conversion material having a higher absorption than the low-absorption direct conversion material, wherein the first direct conversion layer and the second direct conversion layer are arranged such that the high-energy electromagnetic radiation transmits the first direct conversion layer before it hits the second direct conversion layer;
• and
• correcting a drift of the second count signal from the high-absorption direct conversion material, by that there is a drift in the second count signal from the high-absorption direct conversion material:
• when there is a change in the second count signal from the high-absorption direct conversion material but no change in the first count signal from the low-absorption direct conversion material;
• or
• when a correlation between the first count signal from the low-absorption direct conversion material and the second count signal from the high-absorption direct conversion material deviates from a reference correlation.