Device and method for positioning a target volume in radiation therapy apparatus

A method for positioning a target in a patient in a radiation therapy apparatus, comprising:

• determining a relative position between the target and a two-dimensional radiation detector;
• providing a fixation device configured to fix the relative position during the subsequent steps;
• determining an intended intersection point of the radiation beam with the two-dimensional radiation detector;
• directing a sub-therapeutic radiation beam towards the two-dimensional radiation detector and determining an actual intersection point of the beam with the two-dimensional radiation detector;
• computing a correction vector which is a difference between locations of the intended and the actual intersection points;
• and
• applying a correction to a relative position between the radiation beam and the two-dimensional radiation detector, whereby the actual intersection point coincides with the intended intersection point;
• wherein determining the relative position of the target and the two-dimensional radiation detector comprises:
• providing a two-dimensional radiation detector having three or more points for fixation to a target support, the points having a geometric relationship with the two-dimensional radiation detector;
• installing the target in a fixed way on a target support;
• providing markers on the target support at fixation points of the two-dimensional radiation detector, the markers being visible in an imaging modality;
• obtaining an image of the target using an imaging modality where both the target and the markers are visible;
• determining from the image the geometric relationship of the target and the markers;
• and
• inferring therefrom the geometric relationship between the target and the two-dimensional radiation detector.