Patent ID: 7369694

Claim:
A method for determining coordinates of images of marks in a volume dataset comprised of a plurality of consecutive computed tomography slice images of a subject in which image data in each slice image are described with Cartesian coordinates, and wherein the marks are disposed on a surface of the subject, and wherein the volume dataset represents images of the marks and an image of at least a part of the subject having a surface on which the marks are disposed, said method comprising the steps of: performing a coordinate transformation for each slice image from Cartesian coordinates to polar coordinates relative to a line extending through the image of the subject, said line being oriented substantially perpendicularly to the slice images, thereby obtaining transformed sliced images; determining contours in each of said transformed slice images allocated to the surface of the subject in that transformed slice image; generating an image dataset substantially comprising pixels of the image of the surface after transformation into a plane and pixels of the images of the marks; generating a two-dimensional image dataset by re-extracting image data representing the images of the marks in a region parallel to the imaged surface; determining coordinates of the images of the marks in the two-dimensional image dataset; and re-transforming the coordinates of the images of the marks back into the coordinates allocated to the volume dataset.