A photonic radiation detection device includes a collimator, a detector, means for localization in the detection plane defining on the one hand the partitioning of the detection plane in physical or virtual pixels of transversal dimensions smaller than those of the collimator channels, and associating on the other hand one of said pixels to each photon interaction. The detection device has at least in one previously selected acquisition configuration, a degree of pixelation in the detection plane greater than 1 and a collimator-detector distance (c) greater than one tenth of the septal height (h) of the collimator. A method for dimensioning such a device includes, for at least one given spatial frequency, calculating and comparing merit indicator values for different acquisition configurations of a structural model of the detection device.