Dynamic collimation in cone beam computed tomography to reduce patient exposure
AssigneeKoninklijke Philips Electronics N.V.
InventorsDominic J. Heuscher, Felix Godfried Peter Peeters
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Abstract
When performing a fly-by or helical CT scan of a subject, radiation dose is limited by positioning a dynamic collimator (142) between the subject and an X-ray source (112). The collimator moves axially with the X-ray source (112) along a volume of interest (VOI) (122) in the subject and gradually opens, such that a narrow portion of the cone beam of X-rays is permitted to pass through the collimator (142) at ends of the VOI (122) and a wider full cone beam is emitted at central portions of the VOI (122). In this manner, tissue surrounding the VOI (122) is not needlessly exposed to X-rays, as would be the case if a full-width cone beam were used for the entire scan of the VOI (122).
Claims21
A system for limiting radiation dose to a patient during a computed tomography scan, including:
- an X-ray source on a rotating gantry configured to move axially parallel to a volume of interest (VOI) on a stationary subject support as the X-ray source rotates around the VOI;
- a dynamic collimator positioned between the X-ray source and the VOI and moveable with the X-ray source;
- and
- an X-ray detector positioned opposite the X-ray source and collimator to receive X-rays that have passed through the VOI;
- wherein the X-ray source begins CT acquisition of the VOI at an X-ray initiation position, terminates CT acquisition of the VOI at an X-ray termination position;
- wherein the dynamic collimator begins to open at the X-ray initiation position to limit X-rays passing through the collimator to X-rays that will pass through the VOI, opens in coordination with axial movement to permit a full X-ray cone beam to pass through to scan the VOI, and closes in coordination with axial movement to reduce X-rays passing through the collimator as the collimator approaches the X-ray termination position.
A method of reducing radiation dose to a subject during a CT scan, including:
- starting axial movement of an X-ray source and a dynamic collimator at a start point;
- initiating CT acquisition by the X-ray source at an X-ray initiation position;
- opening shutter blades on the dynamic collimator at the X-ray initiation position to permit a portion of an X-ray cone beam that passes through a VOI, and to block a portion of the X-ray cone beam that does not pass through the VOI;
- increasing at least an axial width of the X-ray cone beam until the VOI is exposed to a full X-ray cone beam, as the X-ray source and dynamic collimator move axially toward a midpoint of the VOI;
- and
- reducing at least an axial width of the X-ray cone beam as the X-ray source and dynamic collimator move axially away from the midpoint of the VOI, toward an X-ray termination position, wherein the dynamic collimator blocks X-rays that will not pass through the VOI.
A method of scanning a VOI, comprising:
- moving a cone beam of radiation from a first end of the VOI to a second end along a substantially helical path;
- truncating a trailing portion of the cone beam adjacent the first end of the VOI;
- and
- truncating a leading portion of the cone beam adjacent the second end of the VOI.
A system for controlling radiation during a CT scan, including:
- a dynamic collimator, coupled to an X-ray source and positioned between the X-ray source and a VOI, and that moves axially along, and rotationally around, the VOI along a helical path;
- a first axially stationary collimator positioned between the an X-ray initiation position and a first end the VOI to limit a portion of a cone beam of radiation passing from the X-ray source through the dynamic collimator to X-rays that pass through the VOI;
- and
- a second axially stationary collimator positioned between an X-ray termination position and a second end the VOI to limit a portion of the cone beam passing from the X-ray source through the dynamic collimator to X-rays that pass through the VOI.
A system that facilitates limiting radiation dose received by a subject during a tilted axis CT scan, including:
- an X-ray source that rotates around a VOI while moving axially along the VOI;
- and
- a dynamic collimator coupled to the X-ray source and positioned between, and rotatable with, the X-ray source around the VOI;
- wherein the dynamic collimator opens to emit a tilted-axis X-ray cone beam while limiting X-ray emission through the dynamic collimator to only X-rays that pass through the VOI and are usable for image reconstruction of the VOI.
Dependencies are inferred from the claim text.