Patent ID: 7400700

Claim:
A non-diagnostic, stereoscopic x-ray tracking method for tracking moving objects in the context of radiotherapy and radiosurgery, wherein first and second x-ray devices are used to repeatedly record x-ray images of an object along two different point of views through a target area of an irradiating apparatus, said two different point of views intersecting at a known angle, comprising: controlling the first and second x-ray devices such that each x-ray device alternately obtains an image of the object as the object moves through the target area, and with the assistance of a computer determining a first surface that is spanned by a first viewing line from the first x-ray device to the object in an image recorded at an earlier point in time and a second viewing line from the first x-ray device to the object in an image recorded at a later point in time; determining a first intersecting point from a third viewing line from the second x-ray device to the object in an image recorded at a point in time between the earlier point in time and the later point in time, and the first spanned surface; determining a second surface, wherein the later point in time becomes a new earlier point in time, and wherein said second surface is spanned by the second viewing line from the first x-ray device to the object in an image recorded at the new earlier point in time and a fourth viewing line from the first x-ray device to the object in an image recorded at a new later point in time; determining a second intersecting point from a fifth viewing line from the second x-ray device to the object in an image recorded at a point in time between the new earlier point in time and the new later point in time, and the second spanned surface; calculating a spatial straight connecting line that connects the first and second intersecting points; calculating a minimum transversal between the spatial straight connecting line and the fourth viewing line of the object at the new later point in time; and approximating a three-dimensional position of the tracked object from an intersecting point of the minimum transversal and the fourth line of site at the new later point in time.