Particle beams in radiological cancer treatment provide high accuracyin dose delivery. Thus approaches from image-guided radiotherapy(IGRT) are used to overcome accuracy limitations caused by the patientmisalignment in the treatment device. By comparing stereoscopic X-rayimages of the patient in treatment position to a reference ComputedTomography (CT) scan, a correction of the initial patient set-upcan be computed. Automatic registration of the X-ray images withdigital reconstructed radiographs (DRRs) from the CT and back-projectionof the transformations gives a pose correction in 5 degrees of freedom(DOF). To obtain a 6 DOF correction, DRRs have to be generated fora large amount of hypothetical alignments to find the optimal matchto the X-ray images. To accelerate this time consuming process andto reduce the disturbing influence of image contents that do notmatch correctly, we automatically exclude regions that may not improvethe resulting pose correction from the rendering as well as fromthe matching process. Therefore these regions are identified in theX-ray images and transferred into the plane of the respective DRR.We then perform the radon transform for DRR generation only for asubset of possible pixel values and exclude the missing informationfrom the registration process. As a result of this approach, thetime needed for a full automatic pose correction computation in 6DOF is decreased by means of 4 and more and additionally misregistrationscaused by unsuitable image contents can be avoided.     «

Particle beams in radiological cancer treatment provide high accuracyin dose delivery. Thus approaches from image-guided radiotherapy(IGRT) are used to overcome accuracy limitations caused by the patientmisalignment in the treatment device. By comparing stereoscopic X-rayimages of the patient in treatment position to a reference ComputedTomography (CT) scan, a correction of the initial patient set-upcan be computed. Automatic registration of the X-ray images withdigital reconstructed radiographs...     »