Abstract: The present invention relates to a method for positioning an arrangement of at least one beam position relative to a patient's body when the patient is placed for treatment by means of a treatment device which can emit treatment radiation, wherein the at least one beam position describes at least one position of at least one treatment beam, wherein the arrangement is referred to as the treatment arrangement and the treatment beam comprises the treatment radiation, wherein the method is executed by a computer and comprises the following steps: providing treatment beam absorption data which describe the absorption properties of the at least part of the body with respect to absorbing the treatment radiation, and the relative position between the at least part of the body and the treatment arrangement; providing treatment beam data which describe radiation properties of the at least one treatment beam; providing condition data which describe a condition for treating the at least part of the body; determining an

Abstract: The present invention refers to a data processing method for use in the field of radiation therapy and for determining a relative position between the position of the bony structure and a reference position at a monitoring time, the relative position being referred to as monitoring bone position, wherein an anatomical structure of a patient includes the bony structure and a treatment body part to be treated by at least one treatment beam of a treatment device, the reference position having a defined relative position with respect to an actual arrangement of at least one position of the at least one treatment beam; the data processing method being constituted to be performed by a computer and comprising the following steps: •providing CBCT image data describing a three-dimensional CBCT image of the bony structure, the CBCT image representing the bony structure at a pre-alignment time; •providing x-ray image data describing at least one two-dimensional x-ray image of the anatomical structure, the at least one t