Method and apparatus for presenting multiple pre-subject filtering profiles during CT data acquisition
First Claim
Patent Images
1. A pre-subject filter assembly for a CT imaging system having a detector assembly and a high frequency electromagnetic energy projection source configured to rotate about a subject during an imaging session, the filter assembly comprising:
- a beam shaping filter having a body defining multiple filtering profiles, the filter rotatable about an axis of rotation that extends through the body;
wherein the beam shaping filter includes a first end and a second end, wherein the body extends between the first end and the second end and comprises a plurality of depressions to define a plurality of body diameters defining the multiple filtering profiles; and
a controller to cause rotation of the beam shaping filter about the axis of rotation during an imaging session to dynamically filter high frequency electromagnetic energy projected toward the subject as a function of view angle and independent of voltage applied to the high frequency electromagnetic energy projection source.
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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 is caused to rotate by a motor and bearing assembly and 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.
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Citations
20 Claims
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1. A pre-subject filter assembly for a CT imaging system having a detector assembly and a high frequency electromagnetic energy projection source configured to rotate about a subject during an imaging session, the filter assembly comprising:
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a beam shaping filter having a body defining multiple filtering profiles, the filter rotatable about an axis of rotation that extends through the body; wherein the beam shaping filter includes a first end and a second end, wherein the body extends between the first end and the second end and comprises a plurality of depressions to define a plurality of body diameters defining the multiple filtering profiles; and a controller to cause rotation of the beam shaping filter about the axis of rotation during an imaging session to dynamically filter high frequency electromagnetic energy projected toward the subject as a function of view angle and independent of voltage applied to the high frequency electromagnetic energy projection source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A CT system comprising:
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a rotatable gantry having an opening to receive a subject to be scanned; a movable high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the subject at least two view angles; a movable pre-subject filter having a beam shaping filter that is rotatable about itself relative to an axis of rotation extending through the beam shaping filter during an imaging session, the beam shaping filter having a first end and a second end, the first end having a motor assembly connected thereto and the second end having a bearing assembly connected thereto, such that the motor assembly and bearing assembly, when commanded, cause the beam shaping filter, which has multiple filtering profiles, to rotate about the axis of rotation that is defined by a length of the beam shaping filter that is generally perpendicular to the energy beam that is projected toward the subject; wherein the beam shaping filter includes a body that extends between the first end and the second end and comprises a plurality of depressions to define a plurality of body diameters defining the multiple filtering profiles; 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; an image reconstructor connected to the DAS and configured to reconstruct an image of the subject from the photodiode outputs received by the DAS; and a computer programmed to rotate the beam shaping filter about the axis of rotation such that at a first view angle a first filtering profile filters the high frequency electromagnetic energy beam and at a second view angle a second filtering profile filters the high frequency electromagnetic energy beam. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. 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; positioning a first profile of a multi-profile, beam shaping filter between an x-ray source and the subject when the x-ray source is projecting x-rays at a first view angle, wherein the multi-profile, beam shaping filter includes a first end, a second end, and a body that extends between the first end and the second end and comprises a plurality of depressions to define a plurality of body diameters defining multiple filtering profiles that comprise the first profile and a second profile; projecting x-rays in an x-ray beam toward the subject from the x-ray source at the first view angle; rotating the x-ray source to a second view angle; positioning and rotating the multi-profile, beam shaping filter about an axis of rotation that extends through a length of the multi-profile, beam shaping filter and perpendicular to the x-ray beam such that the second profile of the multi-profile, beam shaping filter is positioned 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 in an x-ray beam toward the subject from the x-ray source at the second view angle. - View Dependent Claims (17, 18, 19, 20)
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Specification