A method of a radiotherapy or radiosurgery treatment comprises steps of: (a) providing a converging x-ray beam source configured for emitting a converging X-ray beam propagating along an axis thereof; (b) emitting the converging x-ray beam towards a volume of treatment (VOT) having a length along the axis of the converging X-ray beam ranging between 2 mm and 5 cm within a patient's body such that a waist portion is within the VOT; (c) propagating the beam through tissues previously located relative to the VOT (PO); the VOT per se and tissues distally located to the VOT (DO). The converging X-ray beam characterized by a convergent angle ranging between 2 and 30 degrees providing 80% to 100% of a maximum dose is received by the VOT and less than 60% of the maximum dose is received by the PO and the DO.