Method for characterizing a blood vessel by determining a blood vessel path (400, 401), the blood vessel represented by vascular image data from a DICOM-image, wherein said vascular image data comprises a plurality of voxels each having an image intensity, said method comprising the steps of: - identifying a set of voxels representing at least a portion of a boundary of the blood vessel; - determining a gradient vector of the image intensity for each voxel in said set of voxels representing the boundary of the blood vessel; - selecting, from said set of voxels representing the boundary of the blood vessel, a subset of voxels such that all voxels in said subset of voxels have a common intersection point (v isect) for their respective gradient vector extensions; and - determining a vector product based on said gradient vectors for said subset of voxels, wherein the common intersection point (v isect) indicates a point on the centre axis of said blood vessel and said vector product indicates a direction in which said blood vessel extends, and wherein a length of the gradient vector extension is determined by a predetermined end condition, the predetermined end condition being defined by at least one of that the gradient vector extension only extends until the opposite boundary of the blood vessel is reached, or that the gradient vector extension extends a predetermined length, wherein the method further comprises the steps of: - iteratively selecting an additional subset of voxels from said set of voxels representing the boundary of the blood vessel, wherein all voxels in said additional subset of voxels have a common intersection point for their respective gradient vector extensions and the common intersection point indicates a possible centre point of said blood vessel - finding a plurality of possible centre points of said blood vessel according to the iterative selection of an additional subset of voxels, - selecting a voxel that corresponds to one of the centre points as a starting point for the blood vessel; - tracing the blood vessel path by iteratively: - identifying a possible centre point that is located in a plane that is orthogonal to the direction of the blood vessel, wherein said plane extends through a voxel that is located within a predetermined range from the current centre point in a direction of the blood vessel; and - including the identified possible centre point in the blood vessel path, and wherein the method further comprises the step of: - selecting, when there is more than one possible centre point located in said plane, the centre point that has the most intersecting gradient vector extensions. - identifying a set of voxels representing at least a portion of a boundary of the blood vessel; - determining a gradient vector of the image intensity for each voxel in said set of voxels representing the boundary of the blood vessel; - selecting, from said set of voxels representing the boundary of the blood vessel, a subset of voxels such that all voxels in said subset of voxels have a common intersection point (v isect) for their respective gradient vector extensions; and - determining a vector product based on said gradient vectors for said subset of voxels, - iteratively selecting an additional subset of voxels from said set of voxels representing the boundary of the blood vessel, wherein all voxels in said additional subset of voxels have a common intersection point for their respective gradient vector extensions and the common intersection point indicates a possible centre point of said blood vessel - finding a plurality of possible centre points of said blood vessel according to the iterative selection of an additional subset of voxels, - selecting a voxel that corresponds to one of the centre points as a starting point for the blood vessel; - tracing the blood vessel path by iteratively: - identifying a possible centre point that is located in a plane that is orthogonal to the direction of the blood vessel, wherein said plane extends through a voxel that is located within a predetermined range from the current centre point in a direction of the blood vessel; and - including the identified possible centre point in the blood vessel path, and - selecting, when there is more than one possible centre point located in said plane, the centre point that has the most intersecting gradient vector extensions.