Method for generating a 3D data set complete in the central layer for volume reconstruction and cone-beam C-arm X-ray apparatus for performing the method
Inventors
König, Thomas • Fleischmann, Christof • Ilg, Eva-Maria • Lochner, Lena
Assignees
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Publication Number
US-10660592-B2
Publication Date
2020-05-26
Expiration Date
Abstract
This disclosure generally relates to a method and an apparatus for recording a 3D data set of an ROI (50) complete in the central layer by using a cone-beam C-arm X-ray apparatus (1) having a cone beam (32) with a cone angle (35) in the plane of the C-arm and having a virtual scan center (51) in the center of the ROI (50), wherein the scan is performed with a trajectory pair situated in the virtual scan center (51) and composed of a focus trajectory and a detector trajectory and wherein the rotational portion (402) of the detector trajectory is formed from piece-wise defined superellipses.
Core Innovation
The invention relates to a mobile non-isocentric cone-beam C-arm X-ray apparatus and a method for generating a sequence of 2D X-ray projections for a 3D data set, complete in the central axis for a volume reconstruction, even when the C-arm has a limited orbital adjustment range of less than 180 degrees. The method uses a movement controller and a holder displaceable in at least two spatial directions by linear adjustment elements with a limited adjustment path, while the C-arm is displaceable along the periphery of the arm within that limited orbital adjustment range.
An organ program is used to determine a point of interest (POI) in a section plane of a patient body and to define an envelope curve of the patient cross-section and the cross-section of the tabletop of the section plane in coordinates of a coordinate system connected to the tabletop. A virtual scan center is defined from these inputs, and a detector trajectory and an associated focus trajectory are selected such that their rotational portions deterministically follow the trajectory of a reference point rigidly connected to the X-ray imaging system.
The rotational parts are formed piecewise from superellipses parameterized in polar coordinates so that the distance of the virtual scan center from the reference point depends on the orbital adjustment angle. The invention ensures that the envelope curve of the patient cross-section and the tabletop are arranged collision-free within a volume defined by the flat panel detector housing and the x-ray emitter housing during a virtual scan.
The method outputs a selected detector trajectory and focus trajectory to the movement controller along horizontal and vertical adjustment axes and adjusts a base position of the C-arm holder by motor-powered displacement, aligning the C-arm plane and the virtual scan center with the patient section plane and the POI. x-ray projections are then automatically recorded at predetermined or dynamically determined positions while traversing the selected trajectory pair, enabling central-axis completeness for Feldkamp-style central-layer reconstruction.
Claims Coverage
The partial content provides one explicitly independent method claim. It covers the core workflow of generating a complete central-axis sequence of 2D X-ray projections for 3D volume reconstruction using an organ program, a virtual scan center, and collision-free superellipse-based detector/focus trajectory pairs under a limited orbital adjustment range of less than 180 degrees.
Organ program defining POI, section plane, and collision-free envelope curve
A receiving input for determining an organ program for performing an imaging task, by which organ program a point of interest (POI) in a section plane of a patient body and an envelope curve of the patient cross-section and the cross-section of the tabletop of the section plane are defined in coordinates of a coordinate system connected to the tabletop of the patient table, for arranging the envelope collision-free within a volume defined by the FPD housing and the x-ray emitter housing during a virtual scan.
Superellipse parameterized virtual scan-center detector/focus trajectory pair with rotational portions
A receiving input for selecting a pair comprising a detector trajectory and an associated focus trajectory, each having a rotational portion and comprising two interconnected repeater sections at each end of the rotational parts, wherein the rotational part of the detector trajectory and the rotational part of the focus trajectory deterministically follow from the trajectory of the reference point rigidly connected thereto located on the X-ray imaging system and which is formed piecewise from superellipses parameterized in polar coordinates, with r(θ) representing the distance of the virtual scan center from the reference point depending on the orbital adjustment angle θ, and with the superellipse parameters a, b, θ0, and n defining the rotational position and shape.
Motor-powered multi-axis C-arm base-position adjustment aligning plane and virtual scan center
Outputting the detector trajectory and the focus trajectory of the selected trajectory pair to the movement controller in the coordinates of the horizontal x-adjustment axis and the vertical y-adjustment axis and outputting x and y coordinates of a base position of the C-arm holder, aligning the cone-beam C-arm X-ray apparatus in the base position by displacing the chassis along the floor relative to the tabletop so that both the plane of the C-arm and the virtual scan center coincide with the patient section plane and the POI coincides with the virtual scan center in the patient, using motor-powered displacement in the horizontal and vertical adjustment axes.
Traversal and automated recording of projections at predetermined or dynamically determined positions
Traversing the trajectory pair selected by motor-powered movement of the C-arm in the horizontal x-axis, the vertical y-axis and the orbital axis while automatically recording x-ray projections at positions predetermined and stored together with the trajectories, or determined dynamically during the scan, to generate the sequence of 2D projections complete in the central axis for a volume reconstruction.
Across the provided independent claim, the coverage centers on organ-program definition of POI and section-plane envelope curves, selection of detector/focus trajectory pairs whose rotational portions are formed piecewise from superellipses in polar coordinates with a virtual scan center dependent on orbital angle, motor-powered alignment of the C-arm plane and virtual scan center with the patient section plane and POI under collision-free constraints, and automated projection recording while traversing the multi-axis trajectory pair.
Stated Advantages
Generating a sequence of 2D X-ray projections for a 3D data set that is complete in the central axis for a volume reconstruction despite an orbital adjustment range of less than 180 degrees.
Documented Applications
Performing an imaging task using an organ program that determines a POI in a patient section plane and defines an envelope curve for collision-free virtual scanning with a cone-beam C-arm system.
Performing central-layer reconstruction and volume reconstruction using Feldkamp analytical reconstruction as indicated by central-axis completeness for a volume reconstruction.
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