Calculation of dark-field-to-attenuation CNR ratios of in vivo porcine lung tissue.

, : effective linear attenuation coefficients of water for the dark-field setup at 60 kV and a setup without gratings at 125 kV. −∂(ln D)/∂dH2O: slopes from linear regression of −ln D w.r.t. dH2O, cf. Table 2. Normalized scatter values are calculated using Eq (18). Via Eq (23), we join them with the ratio of standard deviations for realistic signal levels (cf. Fig 5B) to determine ratios of dark-field and transmission CNR due to small differences in lung thickness.