A medical apparatus, particularly suitable for the treatment of a breast cancer, which apparatus has:a support for a patient, such as to expose a breast in a predetermined position of the support；an imaging unit, configured in such a way as to provide, in use, a 3D image of the breast；a treatment unit, having delivery means of a ionizing radiation beam and configured so as to provide, in use, the beam at the breast；a control unit of the imaging unit and/or treatment unit, configured to determine the delivery of a radiation beam with a shape dependent upon the image of the target body district supplied by the imaging unit.
