(a)
(b)
Figure 5: One-pixel-thick profiles drawn through the phantom. (a) Profiles at the level of a cylinder with a diameter of 20 mm. (b) Profiles at the level of cylinders with a diameter of 40 mm. Ideal OSEM: images reconstructed from noise-free projection images using ordered subset expectation maximisation reconstruction; AR-OSEM-AR: autoregressive filtering before and after ordered subset expectation maximisation reconstruction; BW-FBP: filtered back projection reconstruction method preceded by Butterworth filtering; OSEM-BW: ordered subset expectation maximisation reconstruction followed by Butterworth filtering. Intermediate count level. Profiles were rescaled so that they had the same amount of counts as the profile of the image reconstructed from noise-free projection images using ordered subset expectation maximisation reconstruction.