Abstract: The present invention is related to a method for treating or irradiating a target volume with a particle beam produced by an accelerator, comprising the steps of: deflecting said particle beam with the help of scanning means in two orthogonal (X, Y) directions, thereby constituting an irradiation plane perpendicular to the direction (Z) of the beam, defining in the irradiation plane a scanning field which circumscribes the area of intersection of target volume and irradiation plane and scanning said scanning field by drawing scan lines which form a scan pattern comprising interleaved frames of triangle waves. The scan pattern is preferably continuous and represents contiguous rhombi figures. The invention is equally related to a device and a software program or sequencer implementing the method.