Retroreflective Surgical Marker Element for Navigation Accuracy

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Solution Overview

Problem

Conventional passive marker elements coated with special films reflect only a small part of electromagnetic radiation back due to diffuse reflection, limiting the accuracy of position and orientation determination in navigation systems.

Innovation Solution

A marker element with a carrier material permeable to electromagnetic radiation and retroreflective elements having a refractive index between 1.5 and 3.4, allowing for complete retroreflection of incident light, and optionally coated with a reflective layer for enhanced performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If passive marker elements are coated with special films, then the marker elements can reflect electromagnetic radiation, but only a small portion of the radiation is reflected back due to diffuse reflection

Engineering Contradiction:
Improveelectromagnetic radiation reflection efficiencyVSAvoidposition and orientation determination accuracy
Core Design Contradiction:
Loss of energyVSMeasurement precision

Solution Approach 1:

The patent changes the optical parameters of the marker element by selecting specific refractive index values (1.5 to 2.5 or 2.5 to 3.4) for the retroreflective elements material and using a transparent carrier material, enabling complete retroreflection of electromagnetic radiation and resolving the contradiction between radiation reflection efficiency and measurement precision

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite structure consisting of a transparent carrier material and retroreflective elements with specific refractive indices, creating a multi-material system that achieves both high radiation reflection efficiency and accurate position determination by combining the advantages of different materials

Inventive Principle:
Principle #40Composite materials

2Reliability

If a reflective surface is used, then radiation can be reflected back to the source, but only when the surface is orthogonally aligned

Engineering Contradiction:
Improveradiation reflection reliabilityVSAvoidorientation independence
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent divides the reflective surface into multiple retroreflective elements (spheres or beads) distributed across the marker element surface, each capable of retroreflecting radiation independently, which maintains reliable reflection across various orientations and resolves the contradiction between reflection reliability and orientation adaptability

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent uses spherical or bead-shaped retroreflective elements instead of flat reflective surfaces, exploiting the geometric properties of spheres to achieve retroreflection from any incident angle, thereby maintaining both reflection reliability and orientation versatility

Inventive Principle:
Principle #14Spheroidality (Curvature)

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 solution enables improved visibility and precise determination of the marker element's position and orientation by reflecting electromagnetic radiation back in the direction of incidence, enhancing navigation system accuracy.

Implementation Method 1

the marker element is designed to reflect electromagnetic radiation, wherein the marker element comprises a layer comprising a plurality of retroreflective elements

Methodology Applied
Scientific EffectRetroreflection: Retroreflector

Implementation Method 2

the support is formed from a support material that is transparent to electromagnetic radiation

Methodology Applied
Scientific EffectTransparency:

Implementation Method 3

the material from which the retroreflective elements are formed has a refractive index with a value in the range of about 1.5 to about 2.5, or a refractive index with a value in the range of about 2.5 to about 3.4

Methodology Applied
Scientific EffectRefraction: Refraction

Data Source

PatentEP3359077B1Surgical marker element, surgical referencing unit, and surgical navigation system
Publication Date: 2023.12.06 AESCULAP AG
  • EP3359077B1 patent drawingFigure 1
  • EP3359077B1 patent drawingFigure 2
  • EP3359077B1 patent drawingFigure 3

AI summary

The invention relates to a marker element, particularly a medical or surgical marker element for a referencing unit of a navigation system, said marker element being designed to reflect electromagnetic radiation. In order to improve such a marker element such that the determination of position and/or orientation of the referencing unit in space is improved, the marker element should comprise a layer that has a plurality of retro-reflecting elements. The invention also relates to an improved referencing unit and to an improved navigation system.