Patent ID: 8338783

Claim:
A method for verifying quantities of interest of a radiation beam in a radiation therapy apparatus comprising a multi-leaf collimator provided with leaves, comprising the steps of: providing a dosimetry device comprising an active area which includes individual detectors; the active area comprising a limited number of lines of radiation detectors and a number of extra radiation detectors dedicated to energy measurements of electrons or photons; the dosimetry device further comprising a build-up plate with a plurality of energy degraders, the energy degraders being located upstream from the extra radiation detectors in the path of the radiation beam; adapting the dosimetry device for determining positions of leaves of a multi-leaf collimator in an Intensity Modulated Radiation Therapy apparatus, wherein the limited number of lines of radiation detectors comprises at least one extra line of radiation detectors dedicated to measurement and determination of projection of the leaves position at isocenter of the Intensity Modulated Radiation Therapy apparatus, the at least one extra line of radiation detectors being located at about expected positions of the projection of the leaves; positioning the leaves of the multi-leaf collimator in a predetermined position; delivering a radiation dose to the dosimetry device through the multi-leaf collimator; measuring dose absorbed by a plurality of radiation detectors of a line of radiation detectors located in a penumbra region of one of the leaves; and determining the quantities of interest by fitting measured doses with a function, wherein the quantities of interest comprise: a position of one of the leaves; a position and width of the penumbra region; positions where a beam profile reaches a given percent of a value of the beam in the center of the beam; skewness of the beam; flatness of the beam; and position of the center of the radiation beam.