Fan-beam collimators offer a good balance between resolution and noise. The
collimator response may be included in iterative reconstruction algorithms
in order to improve single-photon emission tomography (SPET) resolution. T
o this end, accurate determination of the focal region and characterisation
of the collimator response as a function of the source co-ordinates must b
e performed. In this paper, a method to characterise fanbeam collimators is
evaluated. First, we calculated the real focal region and the accuracy of
the collimator convergence. Then, we confirmed the hypothesis that Gaussian
distributions adequately fit the collimator responses, although no individ
ualised treatment was performed for the tails of detector response which ar
e associated with scattering and septal penetration. Finally, analytical fu
nctions were used to model the resolution and sensitivity. The parameter va
lues in these functions were obtained from experimental measures by non-lin
ear regression fitting. Our findings show differences of 1.43% between nomi
nal and real focal length and standard deviations of 2.5 mm in the x-direct
ion and 7.1 mm in the y-direction for the focal convergence. The correlatio
n coefficients between experimental and predicted values were 0.994 for res
olution and 0.991 for sensitivity. As a consequence, the proposed method ca
n be used to characterise the collimator response.