C-arm Registration Accuracy via Phantom Feedback
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Solution Overview
Problem
Existing methods for calibrating imaging devices in image-guided surgery are limited as they cannot adjust registration mappings based on image data from a phantom in a known position and orientation, leading to potential inaccuracies in spatial representation and navigation.
Innovation Solution
A system and method that uses an accuracy assessment phantom with a reference marker array to determine the image coordinates of projected markers with sub-pixel accuracy, allowing for minimization of a distance measure to adjust the registration mapping by optimizing six parameters, thereby improving tracking information and registration accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a registration mapping is pre-calculated using standard calibration methods, then the imaging device can be initially configured, but the registration accuracy cannot be improved or adjusted based on actual imaging conditions
Solution Approach 1:
The system uses image data from a phantom with known marker positions to provide feedback on registration accuracy. The detected marker positions are compared with expected positions, and the registration mapping is adjusted accordingly. This closed-loop feedback mechanism enables continuous improvement of registration accuracy without requiring manual intervention or complex re-calibration procedures.
Solution Approach 2:
The registration mapping parameters are dynamically adjusted based on the detected deviations between actual and expected marker positions. The system modifies transformation parameters (translation, rotation, scaling) to optimize the alignment between the imaging coordinate system and the phantom's known geometry, thereby improving registration accuracy while maintaining adaptability.
2Measurement precision
If tracking devices are used to determine position and orientation, then spatial information can be obtained, but errors in tracking may lead to inaccuracies in the registration mapping
Solution Approach 1:
The system continuously monitors the relationship between tracked marker positions and expected positions from the phantom's known geometry. When discrepancies are detected, the registration mapping is adjusted to compensate for tracking errors, ensuring that the final spatial representation remains reliable despite imperfections in the tracking system.
Solution Approach 2:
The phantom with its precisely known marker positions serves as an intermediary reference object. It bridges the gap between the tracking system's measurements and the actual spatial coordinates, allowing for the detection and correction of tracking-induced registration errors through comparison and adjustment.
3Ease of manufacture
If standard calibration procedures are used, then the imaging device can be set up initially, but no verification or adjustment of registration accuracy is possible
Solution Approach 1:
The system performs self-verification and self-correction by automatically detecting marker positions in the phantom images and comparing them with expected positions. The registration mapping is automatically adjusted without requiring external intervention or complex manual calibration procedures, maintaining ease of setup while significantly improving accuracy.
Solution Approach 2:
The phantom with its precisely manufactured marker array is prepared in advance with known spatial relationships. This pre-configured reference enables the system to perform accurate registration verification and adjustment during actual use, eliminating the need for complex post-hoc calibration while ensuring high measurement precision.
Data Source
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AI summary
The above described invention relates to a method of determining a measure of accuracy of a registration mapping combining data indicative of spatial positions in a three-dimensional operating space and imaging data acquired with an imaging device located in a position and orientation in operating space referred to as imaging pose, the method comprising the steps: bringing a phantom into a first position and orientation in operating space, referred to as first pose, where the phantom is at least in partial view of the imaging device located in a second pose, the phantom comprising an assembly of markers that can be imaged by the imaging device; acquiring image data of the marker assembly of the phantom with the imaging device in the second pose; locating imaged markers in the acquired image data of the marker assembly; obtaining mapped markers by submitting spatial positions of the markers in the marker assembly of the phantom in the first pose to the registration mapping using the second pose as imaging pose; and determining a distance measure of the imaged markers and the mapped markers as the measure of accuracy of the registration mapping as well as System for determining a measure of accuracy of a registration mapping combining data indicative of spatial positions in a three-dimensional operating space and imaging data acquired with an imaging device located in a position and orientation in operating space referred to as imaging pose, the system comprising: a phantom that can be brought into a first position and orientation in operating space, referred to as first pose, where the phantom is at least in partial view of the imaging device located in a second pose, the phantom comprising an assembly of markers that can be imaged by the imaging device ; a first device for acquiring image data of the marker assembly of the phantom with the imaging device in the second pose; a second device for locating imaged markers in the acquired image data of the marker assembly; a third device for obtaining mapped markers by submitting spatial positions of the markers in the marker assembly of the phantom in the first pose to the registration mapping using the second pose as imaging pose; and a fourth device for determining a distance measure of the imaged markers and the mapped markers as the measure of accuracy of the registration mapping.