Method for identifying possible changes in the range of a planned irradiation field before the patient is irradiated with charged particles

摘要

A method serves as a supplemental safety mechanism before the irradiation of a patient with charged particles. By this method, differences which occur from day to day in the density composition within the patient are found, and the influence on the range of the planned irradiation field is determined. For this purpose, two high-resolution x-ray detectors are required, which form an angle of 60-120° to each other.

主权项

1. 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.