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Publication Number
US-11179134-B2
Publication Date
2021-11-23
Expiration Date
Abstract
A method of calibrating a positioning system in a radiation therapy system which includes a radiation therapy unit having a fixed radiation focus, includes irradiating a calibration tool having at least one reference object, capturing at least one two-dimensional image including cross-sectional representations of reference objects of the calibration tool and determining image coordinates of the representation of each reference object. Based on the reference objects' image coordinates, positions of the reference objects in the stereotactic coordinate system relative to an origin of the calibration tool and the position of the origin of the calibration tool relative to the imaging unit, a position difference between the position of the calibration tool in the stereotactic coordinate system and a position of the calibration tool in an imaging system coordinate system including a translational and rotational position difference is calculated.
Core Innovation
The invention relates to calibrating an imaging system that captures images of a patient in relation to a radiation therapy system. The radiation therapy unit includes a fixed radiation focus and a positioning system configured to position the patient relative to the fixed radiation focus. During an image scanning procedure, the imaging system irradiates a calibration tool comprising a plurality of reference objects with ionizing radiation, where the calibration tool and the reference objects have known positions in a stereotactic coordinate system.
The method captures at least one two-dimensional image including cross-sectional representations of the reference objects using a detector during the image scanning procedure. Image coordinates, dxy, of the cross-sectional representation of each reference object are determined in the captured two-dimensional images. Vectors are obtained, including a vector rso from an origin or center point o of the calibration tool to an imaging unit in the stereotactic coordinate system and a vector ro'b from an origin o’ of the calibration tool in an imaging system coordinate system to each reference object.
A transformation is calculated between a 3D position of the calibration tool in the stereotactic coordinate system and a 3D position of the calibration tool in the imaging system coordinate system. The calculation uses the image coordinates dxy, a known vector rob from each reference object to the origin o of the calibration tool in the stereotactic coordinate system, the vector rso, and a vector rsb from each reference object to the imaging unit, where rsb is calculated by rsb=rso+rob=rso+ro,o’+ro’b. A relation between coordinates or vectors in the stereotactic coordinate system and the imaging system coordinate system is determined using a Rodrigues rotation formula for vector rotation in space.
Claims Coverage
Two independent claims are provided: a method claim and a system claim. Each independent claim is organized around a calibration workflow that links irradiating a calibration tool with reference objects, extracting two-dimensional image coordinates, and computing a 3D transformation between a stereotactic coordinate system and an imaging-system coordinate system using vector relations and a Rodrigues rotation formula.
Method of calibrating an imaging system for patient imaging relative to a radiation therapy system using irradiated calibration-tool reference objects
Calibrating an imaging system by irradiating a calibration tool comprising a plurality of reference objects with ionizing radiation during an image scanning procedure using a radiation unit of the imaging system, capturing at least one two-dimensional image including cross-sectional representations of the reference objects, determining image coordinates dxy, and calculating a transformation between a 3D position of the calibration tool in the stereotactic coordinate system and a 3D position of the calibration tool in an imaging system coordinate system using vectors rso, ro'b, rob and rsb where rsb=rso+rob=rso+ro,o’+ro’ব, and determining a relation between coordinates or vectors using a Rodrigues rotation formula for vector rotation in space.
System for calibrating an imaging system using a radiation-irradiated calibration tool with known stereotactic reference-object positions and transformation computed with Rodrigues rotation
A system in which an imaging system irradiates a calibration tool comprising a plurality of reference objects with ionizing radiation during an image scanning procedure using a radiation unit, captures at least one two-dimensional image including cross-sectional representations of the reference objects, and a processor determines image coordinates dxy, obtains a vector rso from an origin or center point o of the calibration tool to an imaging unit in the stereotactic coordinate system and a vector ro'b from an origin o’ of the calibration tool in an imaging system coordinate system to each reference object, and calculates a transformation between a 3D position of the calibration tool in the stereotactic coordinate system and a 3D position of the calibration tool in the imaging system coordinate system using rob, rso and rsb where rsb=rso+rob=rso+ro,o’+ro’ব, and determines a relation between coordinates or vectors using a Rodrigues rotation formula for vector rotation in space.
Both independent claims require: (i) irradiating a calibration tool with ionizing radiation during an imaging scan, (ii) capturing cross-sectional two-dimensional images and determining image coordinates dxy, and (iii) using stereotactic and imaging-system vector definitions to compute a 3D transformation between coordinate systems, with rotation relation determined by a Rodrigues rotation formula. Dependent claims refine the transformation calculation with additional vector relations and/or detector-geometry constraints and can narrow the setup with stereotactic immobilization via a fixation arrangement.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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