Abstract: The invention relates to a device (10) and method for processing images (1) of the pulmonary circulation (2) of a living being in order to characterize the arterial blood flow, wherein a plurality of temporally successive images (1) are processed, said device having a selection interface (12) containing at least two defined locations (a, b, c) of an image (1), a unit (13) for assigning the at least two defined locations (a, b, c) to all images (1), a unit (14) for determining the density (D) at at least two defined locations (a, b, c) in all images (1), a unit (14) for calculating the density (D) for the defined locations (a, b, c) as a function (Fa, fa, fb, fc) of time (t), a unit (16) for analysing the at least one time difference (?b, ?c) between the maximum values (Ma, Mb, Mc) of the density (D) for the at least two defined locations (a, b, c) as a function of time (t), and a display (17) for the at least one time difference (?b, ?c).