Patent ID: 7936859
Filing Date: 2011-05-03
Classification: A61N

Abstract:
1. A method of determining a predetermined position of a positioning system relatively a fixed focus point in a radiation therapy system, the system comprising a radiation therapy unit having a fixed radiation focus point; a measurement tool for holding at least one diode element adapted to measure the radiation intensity in said focus point; a positioning system for positioning a treatment volume in a patient in relation to said fixed focus point in the radiation therapy unit, wherein said measurement tool can be arranged in fixed engagement with the positioning system and a control system adapted to control a movement of said positioning system to control a movement of said positioning system in order to determine said predetermined position, said method comprising the steps of: obtaining a measurement value at a position where said diode element is located substantially in said fixed focus point; determining a value corresponding to a radiation intensity at said position where said diode element is located substantially in said fixed focus point; obtaining measurement data, said data comprising coordinates and radiation intensity, at said predetermined number of measurement points in three substantially orthogonal motional axes at edges of said radiation intensity curve according to a predetermined measurement protocol, wherein said edges are identified by means of said value corresponding to a radiation intensity at said position where said diode element is located substantially in said fixed focus point; and determining a three-dimensional centre coordinate of said obtained coordinates using the measured positions at said measurement points.