Ionization chamber having off-passageway measuring electrodes
First Claim
1. An ionization chamber for monitoring a radiation beam comprising:
- a housing having a primary beam passageway through said housing and having a plurality of secondary beam cells adjacent to said primary beam passageway;
a plurality of first beam measuring electrodes within said housing and located along said primary beam passageway, said first beam measuring electrodes having outputs responsive to energy of a first portion of said radiation beam directed through said primary beam passageway; and
a plurality of second beam measuring electrodes located within said secondary beam cells, said second beam measuring electrodes having outputs responsive to energy of a second portion of said radiation beam.
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Accused Products
Abstract
An ionization chamber for monitoring a radiation beam includes a housing having a primary beam passageway and a number of secondary beam cells that are adjacent to the primary beam passageway. The primary beam passageway passes entirely through the housing. In the preferred embodiment, a large-area beam measuring electrode and an array of small-area beam measuring electrodes are each coaxial with the primary beam passageway. Also, in the preferred embodiment, each secondary beam cell includes a beam measuring electrode. Because the portions of the radiation beam that enter the secondary beam cells do not pass through the ionization chamber, these portions do not contaminate the treatment beam, allowing the beam measuring electrodes within the cells to be dimensioned and configured so as to maximize signal strength.
64 Citations
19 Claims
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1. An ionization chamber for monitoring a radiation beam comprising:
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a housing having a primary beam passageway through said housing and having a plurality of secondary beam cells adjacent to said primary beam passageway; a plurality of first beam measuring electrodes within said housing and located along said primary beam passageway, said first beam measuring electrodes having outputs responsive to energy of a first portion of said radiation beam directed through said primary beam passageway; and a plurality of second beam measuring electrodes located within said secondary beam cells, said second beam measuring electrodes having outputs responsive to energy of a second portion of said radiation beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A clinical radiation system comprising:
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a linear accelerator for generating a radiation beam having a beam axis; a large-area beam measuring electrode on said beam axis, said large-area beam measuring electrode having an electrode axis; an array of second beam measuring electrodes arranged parallel to said large-area beam measuring electrode and symmetrically relative to said electrode axis, said array including at least three second beam measuring electrodes disposed immediately adjacent to said electrode axis, said array having a total area less than an area of said large-area beam measuring electrode; and high voltage electrodes disposed relative to said array and said large-area beam measuring electrode to induce ionization current in said large-area and second beam measuring electrodes in response to characteristics of said radiation beam. - View Dependent Claims (12, 13, 14, 15)
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16. An ionization chamber for monitoring a radiation beam comprising:
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an assembly of generally annular members coaxially arranged to define a housing having a central beam passageway, said assembly having a plurality of cells extending parallel to said central beam passageway; parallel insulative films connected to said annular members perpendicular to said central beam passageway; a large-area electrode formed on a first insulative film and positioned within said central beam passageway; an array of small-area electrodes formed on a second insulative film and positioned within said central beam passageway; a plurality of off-axis electrodes positioned within said cells; and voltage means for inducing ionization current at each of said large-area, small-area and off-axis electrodes in response to propagation of a radiation beam. - View Dependent Claims (17, 18, 19)
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Specification