Hybrid Optical-Inertial Bone Tracking for Vertebrae
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Solution Overview
Problem
Current surgical navigation systems face challenges in tracking individual vertebrae during minimally invasive spinal surgeries due to the small size and close proximity of vertebrae, making it difficult to attach conventional 6 DOF trackers.
Innovation Solution
A hybrid tracker system that includes two optical markers and a motion sensor, allowing for tracking in six degrees of freedom by optically detecting the markers and using the motion sensor to determine the angle of inclination with respect to gravity, thereby enhancing the accuracy of vertebrae tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional 6 DOF trackers are attached to vertebrae for surgical navigation, then tracking accuracy is improved, but the difficulty of attachment increases due to small size and close proximity of vertebrae
Solution Approach 1:
The conventional 6 DOF tracker is segmented into two separate components: (1) an optical tracker with optical markers for position and orientation tracking, and (2) a motion sensor (accelerometer) for measuring angle of inclination. This segmentation allows each component to be smaller and easier to attach to vertebrae while maintaining 6 DOF tracking capability through data fusion
Solution Approach 2:
The patent merges optical tracking data from the optical markers with inertial measurement data from the motion sensor through data fusion algorithms. This combination enables accurate 6 DOF tracking despite the reduced size and separation of individual components, resolving the contradiction between tracker size and tracking accuracy
2Reliability
If conventional 6 DOF trackers are used for vertebrae tracking, then complete six degrees of freedom tracking is achieved, but the tracker size becomes too large for minimally invasive procedures
Solution Approach 1:
The tracker is divided into separate optical and inertial components, each with smaller individual volumes. The optical tracker contains only optical markers while the motion sensor is a compact accelerometer, allowing both to fit on small vertebrae without interfering with minimally invasive surgical approaches
Solution Approach 2:
The patent replaces the mechanical structure of conventional 6 DOF trackers with a hybrid optical-inertial system. Instead of using a single mechanical tracker unit, the system uses optical fields for position detection and inertial sensors for orientation detection, significantly reducing the physical volume required while maintaining complete 6 DOF tracking capability
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
The hybrid tracker system enables precise tracking of vertebrae in six degrees of freedom, improving the accuracy and reliability of surgical navigation during minimally invasive spinal procedures.
Implementation Method 1
a motion sensor moveable with at least one of the two optical markers and configured to produce measurements indicative of an angle of inclination with respect to gravity
Implementation Method 2
tracking optically, with a localizer, positions of the optical markers in a known coordinate system
Data Source
AI summary
First and second tracker assemblies each having a single optical marker are secured to a bone, with the first tracker assembly also including a motion sensor. A localizer optically tracks the optical marker positions, and a pose of a tracker coordinate system (TCS) associated with the tracker assemblies according to three positional DOF and two rotational DOF is determined from the tracked marker positions. Measurements from the motion sensor are utilized to determine an angle of inclination with respect to gravity, and an orientation of the TCS according to a further rotational DOF defined about a virtual line extending between the optical markers is determined from the angle of inclination. A pose of the bone according to six DOF is then determined from the determined pose of the TCS according to three positional and two rotational DOF and the orientation of the TCS according to the further rotational DOF.