Rotatable filter for a pre-subject CT collimator having multiple filtering profiles
First Claim
Patent Images
1. A beam shaping filter for a CT imaging system, the filter comprising:
- a first end and a second end, each end having a circular cross-section;
a body formed of radiation beam filtering material and extending between the first end and the second end, the body designed to be positioned in a path of x-rays emitted by an x-ray tube during radiographic imaging of a subject; and
a pair of depressions formed in the body orthogonal from one another and defining a first body diameter and a second body diameter, wherein the first body diameter defines a minimum radiation beam filtering profile and the second body diameter defines a maximum radiation beam filtering profile and wherein the body further defines a number of radiation beam filtering profiles between the pair of depressions;
wherein the pair of depressions defines a pair of filtering profiles and wherein a slope between a maximum point and a minimum point of one filtering profile is larger than a slope between a maximum point and a minimum point of the other filtering profile.
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Abstract
The present invention is directed to a method and apparatus for CT data acquisition using a rotatable pre-subject filter having more than one filtering profile to control radiation exposure to a subject. The filter has one profile used to filter radiation when the radiation source is positioned above a subject and another profile that is used to filter radiation when the radiation source is positioned at a side of the subject.
88 Citations
16 Claims
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1. A beam shaping filter for a CT imaging system, the filter comprising:
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a first end and a second end, each end having a circular cross-section; a body formed of radiation beam filtering material and extending between the first end and the second end, the body designed to be positioned in a path of x-rays emitted by an x-ray tube during radiographic imaging of a subject; and a pair of depressions formed in the body orthogonal from one another and defining a first body diameter and a second body diameter, wherein the first body diameter defines a minimum radiation beam filtering profile and the second body diameter defines a maximum radiation beam filtering profile and wherein the body further defines a number of radiation beam filtering profiles between the pair of depressions; wherein the pair of depressions defines a pair of filtering profiles and wherein a slope between a maximum point and a minimum point of one filtering profile is larger than a slope between a maximum point and a minimum point of the other filtering profile. - View Dependent Claims (2, 3, 4)
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5. A CT system comprising:
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a rotatable gantry having an opening to receive a subject to be scanned and configured to rotate along a rotational path; a rotatable high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the subject at at least two view angles; a rotatable pre-subject filter having a static shape, wherein the filter is constructed to define at least two filtering profiles such that at a first view angle a first filtering profile filters the high frequency electromagnetic energy beam and at a second view angle rotated from the first view angle along the rotational path a second filtering profile different and rotated from the first filtering profile filters the high frequency electromagnetic energy beam without varying the shape of the filter between rotation between the first view angle and the second view angle, wherein the first filtering profile has a maximum point and a minimum point and the second filtering profile has a maximum point and a minimum point, and wherein a slope between the maximum point and the minimum point of the first filtering profile is larger than a slope between the maximum point and the minimum point of the second filtering profile; a scintillator array having a plurality of scintillator cells wherein each cell is configured to detect high frequency electromagnetic energy passing through the subject; a photodiode array optically coupled to the scintillator array and comprising a plurality of photodiodes configured to detect light output from a corresponding scintillator cell; a data acquisition system (DAS) connected to the photodiode array and configured to receive the photodiode outputs; and an image reconstructor connected to the DAS and configured to reconstruct an image of the subject from the photodiode outputs received by the DAS. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A method of reducing x-ray exposure during CT data acquisition comprising the steps of:
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positioning a subject to be scanned in a scanning bay, the scanning bay defined by a gantry having a bore therethrough and wherein the gantry includes an x-ray source and a multi-profile filter designed to rotate around the subject during an imaging session, the multi-profile filter having a first generally hour-glass cross-section and a second generally hour-glass cross-section different from the first cross-section and defined to be orthogonal from the first generally hour-glass cross-section; spinning the multi-profile filter to a first filtering profile position such that a first filtering profile defined by the first generally hour-glass cross-section is positioned between the x-ray source and the subject when the x-ray source is projecting x-rays at a first view angle; projecting x-rays toward the subject from the x-ray source at the first view angle; rotating the x-ray source to a second view angle; spinning the multi-profile filter to a second filtering profile position such that a second filtering profile defined by the second generally hour-glass cross-section is between the x-ray source and the subject when the x-ray source is projecting x-rays at the second view angle; and projecting x-rays toward the subject from the x-ray source at the second view angle. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification