Segmenting pulmonary arteries

A method of identifying at least part of a pulmonary artery tree (402) comprises receiving (102) a bronchial tree structure (500) and receiving (104) a pulmonary vessel structure (400). A pair of a first bronchial segment (602) and a first vessel segment (604) is identified (106), wherein the first bronchial segment and the first vessel segment are adjacent with respect to position and orientation. The first vessel segment is identified (108) as arterial segment of the pulmonary artery tree. A spatial transformation is applied (110) such that the first bronchial segment and the first vessel segment substantially coincide (602'). Respective further vessel segments (606, 608) are identified (112) adjacent to bronchial segments (610, 612), wherein the bronchial segments are comprised in the bronchial tree.