Portal imaging during radiotherapy
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Publication Number
US-11033756-B2
Publication Date
2021-06-15
Expiration Date
Abstract
A radiotherapy apparatus comprises a source for producing a beam of ionising radiation along an axis, the beam covering a maximum aperture of the source, a collimator for collimating the beam to produce a collimated beam covering a sub-part of the maximum aperture, a patient support positioned in the path of the beam, a rotatable gantry, on which the source is mounted, for rotating the source around the patient support thereby to deliver the beam from a range of directions, an imaging device located opposite the source and with the patient support between the source and the imaging device, and mounted on the gantry via a drive member allowing translational motion of the imaging device in at least one direction perpendicular to the axis, and a control unit adapted to control the drive member to move the imaging device within the maximum aperture and maintain coincidence between the imaging device and the sub-part of the maximum aperture. Accordingly, the EPID can be moved during the treatment in order to maintain the collimated field of the radiation beam within the bounds of the EPID. This ensures that the image is valid and prevents damage to the EPID as a result of exposure of more sensitive (or less shielded) parts to the beam.
Core Innovation
The invention relates to a radiotherapy apparatus for treating a target portion of a patient using a rotatable gantry that rotates a source around a rotation axis. The source produces a beam of ionizing radiation having a central axis perpendicular to the rotation axis, where the central axis and the rotation axis intersect at an isocenter. A collimator collimates the beam to produce a collimated beam directed along a beam axis toward a tumor, and the beam axis is offset with respect to the isocenter so that the tumor is located in an offset position for at least one rotational position.
An imaging device is located opposite the source so that the patient support is located between the source and the imaging device. The imaging device is mounted on the rotatable gantry via a drive member adapted to allow translational motion of the imaging device in at least one direction perpendicular to the central axis. A control unit provides instructions to control the drive member to move the imaging device during rotation so that alignment is maintained between the tumor at the offset position, the imaging device, and the collimated beam that covers a sub-part of the maximum aperture.
In coordinated operation, the control unit maintains that the imaging device remains in the beam as the source rotates toward the tumor in the offset position from a plurality of rotational positions. The approach includes coordinating the rotation of the source and the movement of the imaging device so the imaging device remains in the beam at different rotational positions, and an output image may be used to check whether a distance between an image of the collimated beam and an edge of the output image is below a threshold to command movement of the drive member to keep alignment.
Claims Coverage
The partial content identifies three independent claims. Across these claims, the core coverage centers on maintaining imaging-device alignment within an offset beam delivered during gantry rotation, using translational imaging-device motion coordinated by a control unit, with an image-threshold feedback refinement and structural refinements for gantry geometry.
Translational imaging-device motion coordinated with gantry rotation for offset-beam alignment
A radiotherapy apparatus in which an imaging device opposite the source is mounted on a rotatable gantry via a drive member adapted to allow translational motion perpendicular to the central axis, while a control unit controls the drive member during rotation to maintain alignment between a tumor in an offset position, the imaging device, and a collimated beam covering a sub-part of the maximum aperture.
Off-isocenter tumor treatment with imaging-device staying in the beam
A radiotherapy apparatus where a rotatable gantry directs a beam along an offset beam axis toward a tumor located in an offset position for at least one rotational position, and a control unit coordinates movement of an imaging device relative to the source so that the imaging device remains in the beam as the source rotates and directs the beam to the tumor in the offset position.
Maintain imaging-device in an offset beam during source rotation
A radiotherapy apparatus comprising a rotatable gantry, a source producing a beam with a central axis perpendicular to the rotation axis and intersecting at an isocenter, the beam axis being offset with respect to the isocenter, and an imaging device mounted on the rotatable gantry via a drive member adapted to allow translational motion perpendicular to the central axis, wherein a control unit controls the drive member to maintain the imaging device in the beam as the source rotates to different rotational positions and directs the beam toward the tumor in the offset position.
The independent claims collectively cover an apparatus that intentionally uses an offset beam axis and an offset tumor position relative to an isocenter while maintaining the imaging device in the beam during gantry rotation by translational motion controlled by a control unit. The coverage further supports optional refinement for image-based threshold checking to command drive-member movement, along with structural refinements such as rotatable drum and arm-based mounting.
Stated Advantages
Maintains alignment between the tumor at the offset position, the imaging device, and the collimated beam covering a sub-part of the maximum aperture.
Ensures the imaging device remains in the beam as the source rotates to different rotational positions and directs the beam toward the tumor in the offset position.
Documented Applications
Using the radiotherapy apparatus to treat a target portion of a patient where the tumor is located in an offset position with respect to an isocenter during rotation.
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