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Abstract

The present invention concerns a method for designing a ridge filter for a charged particle accelerator, for depositing with beams of accelerated particles (100.i) specific doses (Dij) into specific locations within a treatment volume (V) of tissue comprising tumoral cells (3t) by single layer pencil beam scanning (PBS), according to a predefined treatment plan (TP), the method comprising the following steps,

Defining an array of spots (Si) defining the bases of cylindrical subvolumes (Vi) defining the treatment volume (V); the subvolumes (Vi) are divided into N cells (Cij).The ridge filter is designed comprising the same number of energy degrading units (11.i) as there are spots (Si). Each energy degrading unit (11.i) is formed by N cylindrical degrading subunits (11.ij) of lengths (Lij) and area (Aij).The lengths (Lij) of each degrading subunit (11.ij) are calculated as Lij=Wij/Wu, and Wij=W0−dij, wherein Wij is the desired subunit water equivalent thickness (Wij),Wu is the subunit water equivalent thickness per unit length (Wu),W0 is the maximum beam range anddij is the desired position of the Bragg peak along the irradiation axis (X). The area (Aij) of each degrading subunit (11.ij) is obtained by determining the area boundary (Aij) of the integral at the numerator satisfying the following Equation (1).

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First Claim