Comment by lars_thomas

Pretty much. Normal x-ray sensors are like camera sensors and produce an estimate of total energy of the photons / pixel. Photon counting sensors are able to estimate how many photons of certain energy range hit the sensor. So instead of value ’1023’ you might get ’63’ of < 20kv, ’500’ of 20-50kv and ’50’ of > 50kv. So poor mans spectroscopy. Naive way to produce ’color images’ would be to put those buckets to red green and blue channel and now different materials along the beam path might yield equal values with normal x-ray sensors but slightly different colors with photon counting sensors. edit: clarified last sentence