C-Arm Imaging Calibration for Surgical Navigation Accuracy
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Solution Overview
Problem
C-arms used in surgical navigation require cumbersome hardware and artificial fiducial objects for calibration, increasing system complexity and hindering clinical practice.
Innovation Solution
A method and system for calibrating C-arm imaging devices using an iterative calibration algorithm that generates a functional form model for 2D navigation, employing a calibration fixture with known geometry and an infrared tracking system to determine intrinsic and extrinsic parameters offline, allowing for periodic updates without extensive recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If C-arms are calibrated inter-operatively using hardware and artificial fiducial objects, then calibration accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts the calibration process from the operational C-arm system by using a separate tracking array mounted on the C-arm that can be independently calibrated. The fiducial objects are removed from the surgical field and replaced with a pre-calibrated tracking array, separating the calibration function from the imaging function.
Solution Approach 2:
The tracking array is pre-calibrated offline before surgery using a simplified procedure. This preliminary calibration establishes the transformation between the tracking array coordinate system and the C-arm detector coordinate system, eliminating the need for complex intraoperative calibration with fiducial objects.
2Measurement precision
If calibration is performed frequently to maintain accuracy, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The tracking array undergoes comprehensive calibration offline before surgery, storing the transformation parameters for later use. This preliminary action eliminates the need for repeated calibration during surgery, saving time while maintaining accuracy.
Solution Approach 2:
The system continuously monitors the position of the tracking array relative to the C-arm detector using the stored transformation parameters. This feedback mechanism ensures calibration accuracy is maintained without requiring frequent recalibration, as the pre-established transformation relationship remains valid throughout the procedure.
Data Source
AI summary
Examples of the disclosure include methods and systems for calibrating a C-arm imaging device for surgical navigation. Calibrating the C-arm imaging device may include, for a plurality of positions of the C-arm imaging device, determining the position of the C-arm imaging device, receiving an image of a calibration fixture from the C-arm imaging device, determining the position of the calibration fixture and a tracking array positioned on the C-arm imaging device, determining intrinsic parameters using the image and the position of the calibration fixture, and determining extrinsic parameters using the position of the tracking array relative to a detector of the C-arm imaging device. Calibrating the C-arm imaging device may include modeling parameters for the C-arm imaging device and iteratively tuning the model.