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US 8,044,365 B2Granted
High-resolution ion chamber
AssigneeStandard Imaging, Inc.
InventorsLarry A. DeWerd, Brian D. Hooten, Edward W. Neumueller
Life of this patent
Estimating the term…
Abstract
Nested ionization chambers provide independent measurements of a radiation beam that does not fully irradiate the volume of one or both chambers. By mathematically combining these independent measurements, partial volume effects caused by a change in ionization detector calibrations when the full detector volume is not irradiated by the radiation beam, may be decreased, providing more accurate measurement of extremely small radiation beams.
Claims16
A ionization chamber system comprising:
- a radiation detector providing an ionization detector defining a first volume and providing for a detection of ionized gas in the first volume at a first collection electrode;
- a second radiation detector positioned within the first volume and defining a second volume within the first volume and providing for the detection of radiation in the form of an electrical signal at a second collection electrode, the first volume being electrically separated from the second volume;
- wherein radiation passing through the second volume also passes through the first volume providing current at the first and second collection electrodes;
- further including an computer executing a stored program and receiving radiation signals from the first and second radiation detectors to provide a correction for at least one of the radiation signals by evaluating the signals of the first and second radiation detector to correct for partial volume effects caused by radiation beams having an axial cross-section smaller than a corresponding cross-section of the first volume along the axis.
1 more element
A method of measuring radiation beams from a radiation therapy machine comprising the steps of:
- (a) exposing an ionization chamber system to a least one radiation beam having a beam cross-sectional area along a beam axis, the ionization system having:
- a first radiation detector providing an ionization detector defining a first volume having a first cross-sectional area along the beam axis larger than the beam cross-sectional area and providing for a detection of ionized gas in the first volume at a first collection electrode;
- a second radiation detector positioned within the first volume and defining a second volume smaller than the first volume and having a second cross-sectional area along the beam axis smaller than the first cross-sectional area and providing for the detection of radiation in the second volume at a second collection electrode, the first volume being isolated from the second volume;
- wherein radiation passing through the second volume also passes through the first volume providing current at the first and second collection electrodes from the ionization of gas in the first and second volumes;
- (b) analyzing the current at the first and second collection electrodes to reduce partial volume errors in a measurement of dose deduced from the first and second currents.
2 more elements
A method of measuring radiation beams from a radiation therapy machine comprising the steps of:
- (a) exposing an ionization chamber system to a least one radiation beam having a beam cross-sectional area along a beam axis, the ionization system having:
- a first radiation detector defining a first volume having a first cross-sectional area along the beam axis larger than the first cross-sectional area and providing for a detection of ionized gas in the first volume at a first collection electrode;
- a second radiation detector positioned within the first volume and defining a second volume smaller than the first volume and having a second cross-sectional area along the beam axis smaller than the first cross-sectional area and providing for the detection of ionized gas in the second volume at a second collection electrode, the first volume being isolated from the second volume;
- wherein radiation passing through the second volume also passes through the first volume providing current at the first and second collection electrodes from the ionization of gas in the first and second volumes;
- (b) analyzing the current at the first and second collection electrodes to determine misalignment of the radiation beam with respect to the second radiation detector.
2 more elements
Dependencies are inferred from the claim text.