Patent ID: 6736831
Filing Date: 2004-05-18
Classification: A61N,G21K

Abstract:
Method of operating a heavy ion beam therapy system with monitoring of the radiation dose distribution,wherein the heavy ion beam therapy system comprises at least one ion source (1) an accelerator device (2, 5) for the acceleration of the ions of the ion source (1) in the form of a heavy ion beam (11), a beam guidance system (6, 8), to guide the heavy ion 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 vertical deflection means (13) and horizontal deflection means (14) for the vertical and horizontal deflection of the heavy ion beam (11) perpendicular to its beam direction, with the result that the heavy ion 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) using a specific radiation dose, characterised in that the radiation dose distribution of the grid scanner device (13, 14) at various positions in the region of the isocentre (10) is measured and evaluated; and it is concluded that the radiation dose distribution is adequately homogeneous if the degree of variation in the radiation dose values measured at the individual positions does not exceed a specific tolerance limit value; and monitoring means are calibrated in accordance with a calibration factor K in respect of the particle count, ascertained by those means, per monitoring unit of the monitoring means, the calibration factor K being calculated, as a function of the irradiation energy E of the particles of the heavy ion beam (11) and the scanning step width Ax and Ay of the grid scanner device (13, 14), by means of: K(E, &Dgr;x, &Dgr;y)=(Dscan/Mi).&Dgr;x.&Dgr;y/(S(E)/&rgr;) in which the expression (S(E)/&rgr;) corresponds to the mass stopping power of the particles of the heavy ion beam (11) at an irradiation energy E,M corresponding to the number of monitoring units per coordinate point i of the monitoring means, and Dscan corresponding to the radiation dose value ascertained by the monitoring means and converted into an energy dose value related to water.