Patent ID: 8792615

Claim:
A method for identifying possible changes in a range of a planned irradiation field before a patient is irradiated with charged particles, comprising: conducting a computer tomography over at least a part of the patient to generate a 3-dimensional computer tomography data set; providing an x-ray system comprising two high-resolution x-ray detectors, which form an angle of 60-120° to each other, and two x-ray sources opposite the x-ray detectors, wherein each combination of an x-ray source and an x-ray detector defines one of two projection directions; preparing two actual x-ray images of at least a part of the patient in the two projection directions by means of the two x-ray detectors; calculating two digitally reconstructed nominal x-ray images from the computer tomography data set corresponding to the two projection directions of the x-ray system; conducting a difference analysis to determine differences between the actual x-ray image and the associated nominal x-ray image for the two projection directions; checking the relevance of the found differences with respect to spatial extent and with respect to localization in reference to the planned irradiation field and determining relevant 2-dimensional areas of variation; determining a 3-dimensional body of variation by back-projecting the two 2-dimensional areas of variation into the 3-dimensional computer tomography data set; calculating a mean electron density of the 3-dimensional body of variation on the basis of the found differences between the actual x-ray image and the associated nominal x-ray image for the two projection directions; identifying individual beams of the planned irradiation field which pass through the 3-dimensional body of variation; calculating, under consideration of the changed electron density value in the 3-dimensional body of variation, prospective changed ranges of the identified individual beams of the planned irradiation field; and displaying or making available information on the calculated changed ranges.