Pre-sampled MTF associated with PSI-1, PSI-2, and PSI-3. (a) Measured optical MTF for PSI-2 and PSI-3 obtained through illumination of the arrays with a light source. For each set of array results, a fit to the data, based on a sinc function, is indicated by a solid line. (b) Measured MTF for PSI-1, PSI-2, and PSI-3 obtained with a high-resolution phosphor screen, Lanex Fine, at 72 kVp. In order to allow direct comparisons with the results of the 90 μm pitch PSI-1 and PSI-2 arrays, the results for PSI-3 have been renormalized from a 147 μm aperture [corresponding to that inferred from the optical MTF of (a)] to a 90 μm aperture.