Method for verifying the calculated radiation dose of an ion beam therapy system

Method for the verification of a calculated radiation dose of a heavy ion beam therapy system,

• wherein the heavy ion beam therapy system comprises:
• at least one ion source (1) for heavy ions,
• an accelerator device (2, 5) for the acceleration of the ions of the ion source (1) in the form of a treatment beam (11),
• a beam guidance system (6, 8) to guide the treatment beam (11) from the accelerator device (2, 5) to at least one irradiation site for treatment of a patient, the beam guidance system (6, 8) comprising at least one beam guidance channel (6), and
• a grid scanner device, arranged in the beam guidance system (6, 8), having a vertical deflection means (13) and horizontal deflection means (14) for the vertical and horizontal deflection of the treatment beam (11) perpendicular to its beam direction, with the result that the treatment beam (11) is deflected by the grid scanner device to an isocentre (10) of the irradiation site and scans a specific area surrounding the isocentre (10), and
• wherein irradiation is carried out on the basis of calculated radiation dose data and the accuracy of the calculation of the radiation dose data is verified by using a phantom with the aid of the following steps:
• a) the radiation dose data are calculated for a plurality of specific measurement points in the phantom,
• b) irradiation of the phantom is carried out using the calculated radiation dose, and at the measurement points the radiation dose brought about there is measured, values ascertained by ionization chambers being converted into energy does values for verification of the calculated dose values,
• c) the discrepancy between the radiation dose calculated for the measurement points and the radiation dose measured for the measurement points is determined, and
• d) it is concluded that the accuracy of the calculation of the radiation dose data is adequate if the average discrepancy, for al the measurement points, between the calculated and the measured radiation dose values does not exceed a predetermined first tolerance value of ±5% and, for each individual measurement point, the discrepancy between the radiation dose calculated and measured for that measurement point does not exceed a predetermined second tolerance value of ±7%.