Computed tomography
= Computed tomography
Transmission measurements determine line integrals of an absorption coefficient after taking the logarithm of incident intensity divided by transmitted intensity. Under the ideal straight-ray model, these measurements are a <Radon transform>; <filtered backprojection> reconstructs a planar slice. Angular coverage, calibration and noise control matter because differentiating measured projections amplifies high frequencies. In contrast, <single-photon emission computed tomography> reconstructs an emitting source through a possibly attenuating medium.