Redundant Reciprocal Optical Tracking for Surgical Pose Accuracy
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Solution Overview
Problem
Existing optical tracking systems lack redundancy and reciprocity, which are critical for applications requiring high safety, such as computer-assisted surgery, where systems need to accurately track the pose of objects and instruments without recalibration or re-registration, especially when fiducials become dirty or batteries run low.
Innovation Solution
A redundant reciprocal tracking system where each tracker can sense the positional information of another tracker, allowing for over-determined pose calculation with more than 6 Degrees of Freedom, using optical sensing elements and light sources to triangulate the position and orientation, and incorporating reproducible fixations for easy replacement and recalibration-free operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional optical tracking systems use minimal fiducials (3-4 points) to compute pose, then device complexity is reduced, but measurement precision and reliability deteriorate due to lack of redundancy
Solution Approach 1:
The patent applies excessive action by using more fiducials than the minimum required for pose computation. Instead of using exactly 3-4 fiducials, the system uses 5 or more fiducials on each rigid body, creating an over-determined system that provides redundant measurements for improved precision and error detection
Solution Approach 2:
The patent changes the parameter of fiducial quantity from minimal (3-4) to excessive (5+), transforming the system from minimally determined to over-determined. This parameter change enables the computation of residual errors and improves measurement reliability without significantly increasing system complexity
2Measurement precision
If fiducials are added to improve pose calculation accuracy, then measurement precision improves, but device complexity increases due to additional components
Solution Approach 1:
The patent uses excessive fiducials (5 or more per rigid body) to create an over-determined system. This allows the computation of pose with improved precision through redundant measurements and enables error detection via residual analysis, with the complexity increase being manageable
3Adaptability or versatility
If tracker components are replaced during surgery, then adaptability improves, but time is lost due to recalibration requirements
Solution Approach 1:
The patent performs preliminary action by establishing a reproducible fixation system with known transformation matrices before surgery. The reproducible fixation allows trackers to be pre-calibrated and attached to instruments without requiring recalibration during surgery, saving critical time
Solution Approach 2:
The patent uses feedback through the over-determined system to automatically detect and compensate for tracker replacements. The redundant fiducial measurements provide feedback that allows the system to identify when a tracker has been replaced and automatically recalculate poses without manual recalibration
4Reliability
If reciprocal tracking with multiple trackers is implemented, then reliability improves through redundancy, but device complexity increases due to multiple sensing systems
Solution Approach 1:
The patent uses excessive trackers (at least two reciprocal trackers) to create a redundant measurement system. This provides reliability through multiple independent measurements of the same pose, enabling error detection and improved accuracy while maintaining manageable complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This system enhances measurement quality, reduces noise, and allows for seamless tracker replacement without recalibration, improving safety and efficiency in surgical and other tracking applications by providing redundant data for error detection and improved accuracy.
Implementation Method 1
triangulation is used to find the pose of a rigid body having three or more non-collinear identified fiducials
Data Source
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AI summary
The present invention relates to a redundant reciprocal tracking system composed of at least two trackers 10. A first tracker is able to sense partial or full pose data (orientation and position) of a second tracker in a first reference frame and the second tracker is able to sense partial or full pose data of the first tracker in a second reference frame. Pose data of first and second trackers are further transferred to a central processor 30, which is able to compute the transformation between first and second reference frame. Data generated by the trackers are such designed that they define an over-determined mathematical system (e.g. more than 6 degrees of freedom in a 3D setup). The over-determined information can be used to qualify and/or improve the transformation of the reference frame. In an embodiment of the invention, the tracking system is an optical one and the over-determined information defines an error metric used to check the validity of the transformation. Such setup could be used in surgical navigation system in order to reduce the risk of injury or death of the patient.