Embodiments of the present invention provide a computer-based method for providing image data of a region of a target object (31), comprising the steps of estimating (706) a first intermediate object function indicating at least one characteristic of a first sub-region (501, 503) of said region of the target object, estimating (706) a second intermediate object function indicating at least one characteristic of a second sub-region (502, 504) of said region of the target object, and combining (707) the first and second intermediate object functions to form a combined object function indicating at least one characteristic of the region of the target object (31).
