1. A method of producing an object data set describing a straightened reformat from an original object data set containing an elongate subject, from which an initial cross sectional slice is created transverse to the elongate subject and at least one further cross sectional slice is created transverse to the elongate subject, characterized in that, a reference direction is determined in each cross sectional slice, the object data set is created by concatenating the cross sectional slices, each cross sectional slice orientated so that the reference directions in the cross sectional slices are aligned.