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Figure 3
Whole-image metrics of image-reconstructed image quality as a function of fluence nph. (a) The SNR as calculated using equation (14[link]) for NFH, FFP and NFP, and using either the LSQ (solid squares) or Poisson cost function (open squares). The image correlation was calculated within the finite-support area of the object. At each photon fluence nph and for each cost function type, two separate instances of Poisson noise were generated and applied to the noise-free data set. The noisy data sets are then independently reconstructed and used for our correlation-based SNR calculation. The slope for the LSQ fitting curves is near 0.5 for all three techniques, indicating that the SNR increases roughly as (nph)1/2, as one might expect. (b) The within-support mean squared error (SMSE) of equation (15)[link], which shows improved performance at low fluences for FFP compared with NFH. NFP shows a larger SMSE for all photon fluences tested.

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