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. Author manuscript; available in PMC: 2017 Jan 7.
Published in final edited form as: Phys Med Biol. 2015 Dec 9;61(1):296–319. doi: 10.1088/0031-9155/61/1/296

Figure 1.

Figure 1

Model for the mean (bottom) and covariance (top) of quanta at various stages. 1) After x-ray photon generation, quanta are independent with a variance equal to the mean. 2) When x-ray photons are attenuated by the object, the spatial distribution of the mean and variance change, but remain equal and independent. An operator that includes source blur is also included. 3) In the scintillator, x-ray photons interact with a scintillating material creating many light photons which spread spatially, blurring the mean distribution and adding correlation to the noise. 4) Photodiodes detect the light photons with possible additive readout noise.