A patient immobilization device for positioning a patient in the prone position for breast irradiation, includes a cephalic module for supporting the head and upper extremities of the patient, a thoracic module for supporting the patient thorax, and shaped to allow at least one breast to extend below the thoracic module, and a caudal module for supporting the pelvis and lower extremities of the patient, wherein the cephalic module is optionally detachable and securable to the thoracic module wherein the thoracic module is optionally detachable and securable to the caudal module and the device can be pivoted in an indexed way around a craniocaudal patient axis F.
