Distributed Reference Markers for Non-Rigid Anatomy Tracking
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Solution Overview
Problem
Current surgical navigation systems face challenges in accurately tracking non-rigid patient anatomy with multiple degrees of freedom, often resulting in bulky and unreliable reference markers, which can obstruct surgical sites and lead to inaccuracies due to line of sight issues.
Innovation Solution
A non-rigid anatomy reference system comprising two or more reference markers attached to separate bodies of rigid tissue connected by flexible tissue, with a tracking system and processor that acquires movement data to track the markers as a whole, providing a higher number of degrees of freedom and maintaining registration with prior images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple spherical markers are arranged in a non-colinear arrangement to track rotation, then more degrees of freedom are provided, but the patient reference becomes bulky
Solution Approach 1:
The reference system is divided into multiple separate reference markers (at least two) that are distributed across different anatomical landmarks rather than consolidating all markers into a single bulky assembly. Each marker can be independently tracked, and collectively they provide the necessary degrees of freedom for tracking non-rigid anatomy.
Solution Approach 2:
The system transitions from tracking a single rigid reference object to tracking multiple distributed markers in three-dimensional space. By utilizing the spatial distribution of multiple markers across non-colinear anatomical points, the system achieves six or more degrees of freedom without requiring a bulky single-reference structure.
2Reliability
If additional spherical markers are included for redundancy, then error reduction and line of sight coverage are improved, but the patient reference becomes more bulky
Solution Approach 1:
Instead of adding redundant markers to a single reference object, the system segments the reference into multiple distributed markers placed at different anatomical locations. This segmentation naturally provides redundancy because multiple markers can be tracked simultaneously, and if one marker experiences line of sight occlusion, others remain visible for continuous tracking.
Solution Approach 2:
Markers are placed at specific anatomical landmarks where they can be optimally positioned for tracking. Each marker is located at a distinct site (e.g., different vertebrae or anatomical features) to maximize visibility and minimize mutual occlusion, providing local optimization of tracking reliability without bulkiness.
3Adaptability or versatility
If a single complex reference marker is used to provide additional degrees of freedom, then tracking capability is improved, but the device becomes bulky, expensive and unreliable
Solution Approach 1:
The reference system is segmented into multiple simple, identical markers rather than using one complex marker. Each marker can be a simple spherical or geometric shape that is easy to manufacture and track. The complexity is distributed across multiple simple components rather than concentrated in a single complex structure.
Solution Approach 2:
Multiple simple markers are combined through their spatial distribution and collective tracking to achieve the functionality of a complex single marker. The system merges the tracking information from multiple markers to provide six or more degrees of freedom, achieving the same capability as a complex marker but with simpler individual components.
4Measurement precision
If reference markers are rigidly attached to separate bodies of rigid tissue, then tracking accuracy is improved, but the system cannot accommodate flexible tissue movement
Solution Approach 1:
The reference system is segmented into multiple markers attached to different anatomical structures (rigid and flexible tissues). This segmentation allows the system to independently track movement of each marker, thereby capturing both rigid bone movement and flexible soft tissue deformation. The distributed markers can be attached to vertebrae, skin, or other anatomical features depending on the tracking needs.
Solution Approach 2:
The reference system transitions from a static rigid reference to a dynamic distributed marker system that can adapt to tissue deformation. The markers are distributed across anatomical structures that may move independently, allowing the system to dynamically track both rigid and flexible tissue behavior during surgical procedures.
Data Source
AI summary
A non-rigid anatomy reference system can include reference markers that are rigidly attachable to separate bodies of rigid tissue connected through flexible tissue in a region of a patient forming a marker array. A tracking system can acquire movement data of the reference markers as a function of time and position. A processor can be configured to: receive the movement data, where an individual reference marker has a first number of degrees of freedom less than 6 and a second reference marker having a second number of degrees of freedom; track the marker array as a whole with a total number of degrees of freedom greater than the first and the second number; and produce an updated image of the region of the patient to maintain registration to a prior image of the region and the tracked movement of the reference markers via the function.