Method and apparatus for variable X-ray filtration
Inventors
Assignees
Publication Number
US-9439612-B2
Publication Date
2016-09-13
Expiration Date
2033-06-28
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Abstract
The present invention pertains to a system and method for adaptive X-ray filtration comprising a volume of X-ray attenuating material with a central less attenuating three-dimensional region. The volume of X-ray attenuating material can be positioned within 10 cm from an X-ray source and rotated around an internal axis of rotation. The volume of X-ray attenuating material can be symmetric around the internal axis while the central less attenuating region can be asymmetric around the internal axis. Rotating the volume by a predetermined angle around the internal axis can change the amount of attenuation of an X-ray beam through the filter. The volume can be rotated by the same predetermined angle as an imaging subject or X-ray source and detector are rotated during X-ray image acquisition.
Core Innovation
The invention provides a system and method for adaptive X-ray filtration utilizing a volume of X-ray attenuating material that includes a centrally located, less attenuating three-dimensional region. This volume can be positioned within 10 cm of an X-ray source and is rotatable around an internal axis of rotation. The attenuating volume may be symmetric around the axis, while the central less attenuating region can be asymmetric. By rotating the volume around its axis, the attenuation profile through the filter changes, allowing the system to adaptively modulate the amount and distribution of X-ray attenuation during imaging.
This invention addresses the problem of regional variations in detector exposure that affect image quality and dynamic range in X-ray and particularly computed tomography (CT) imaging. Prior solutions, such as static bowtie filters, lacked adaptability to individual subjects or acquisition angles, as patient anatomy can vary significantly based on projection. Existing adaptive filters were complex and limited in flexibility. The current invention introduces a simpler, rotationally driven adaptive filtration system that enhances flexibility relative to existing systems.
The adaptive filter can be implemented as a rotatable element, such as a cylinder with a central less attenuating region, which may be tailored to the attenuation profile of a specific imaging subject. The design may also include additional stationary filter elements that conform to the outer edges of the rotatable element, equalizing path lengths of the X-ray beam through the filter. The system rotates the filter by the same angle as the imaging subject or X-ray source and detector during acquisition, enabling dynamic adjustment of attenuation as projections change.
Claims Coverage
There are two independent claims providing inventive features for both a system and a method for adaptive X-ray filtration.
X-ray imaging system with rotatable adaptive filter element
An X-ray imaging system includes: - An X-ray source for generating an X-ray beam. - An X-ray detector. - A gantry for rotating the X-ray source and detector around an imaging subject. - An X-ray filter having a rotatable filter element positioned between the X-ray source and subject, configured to rotate around an internal axis during imaging. - Attenuation of the X-ray beam by the filter element is a function of the angular orientation of the rotatable filter element. - A stationary filter element conforming to the outer edges of the rotatable filter element. - A rotation controller that synchronizes rotation of the filter element with the rotation of the X-ray source.
Method of X-ray imaging using a rotatable filter element
A method of X-ray imaging comprising the steps of: 1. Positioning a rotatable filter element in the X-ray beam path between an X-ray source and detector. 2. Positioning an imaging subject in the beam path, between the rotatable filter element and detector. 3. Acquiring a first X-ray projection image with a first amount of attenuation from the rotatable filter element. 4. Rotating the X-ray source relative to the imaging subject. 5. Rotating the rotatable filter element around its internal axis of rotation. 6. Fixing a stationary filter element conforming to the outer edges of the rotatable filter element. 7. Synchronizing the rotation of the rotatable filter element with the relative rotation of the X-ray source and the imaging subject.
The independent claims cover both an adaptive X-ray imaging system and a method of X-ray imaging using a rotatable filter element with angularly-dependent attenuation, synchronized with the motion of the X-ray source and detector, and including stationary filter elements for consistent filtration.
Stated Advantages
The invention provides adaptive bowtie filtration with relatively simple and fast implementation methods and enhanced flexibility relative to existing systems.
Documented Applications
Computed tomography (CT) imaging, including imaging of a human head.
Dental computed tomography, with filter configurations suitable for imaging the dental structure of a human patient.
Metrology applications for CT scans of similar parts or workpieces, including customized filter elements for specific items.
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