The method relates to analysis of a tubular structure 1 such as a rendition of the vascular system of a patient. Gradients g_1j to the surface of the tubular structure 1 are computed in a starting point (BP). Subsequently, a normal {circumflex over (n)} which extends essentially perpendicularly to the gradients is derived and a cross-section is taken along a cutting plane having {circumflex over (n)} as its normal. A subsequent position (VP) is taken by performing a small shift in the direction of {circumflex over (n)}. The axis of the vessel is tracked by repeating the procedure.