Depth scanning for a conformal ion beam treatment of deep seated tumours

Only target-conformal treatment allows one to exploit the advantages of ion beams (the increased dose and high biological efficiency at the end of the particle range) to a maximum extent. Up to now, target-conformal treatment s such as spot scanning or intensity-controlled raster scanning have used f ast magnetic lateral deflection in one or two directions perpendicular to t he beam axis and a slow range variation in the longitudinal axis by active or passive energy variation. The present paper describes a new method for c onformal irradiation with a fast intensity-controlled longitudinal scan in the beam direction, called 'depth scanning'. Its advantages and disadvantag es will be discussed. First experimental results from depth scanning will b e presented.