Tracking Bias Field Compensation for Surgical Navigation

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Solution Overview

Problem

Tracking systems face inaccuracies due to changing physical conditions, mechanical distortions, and inhomogeneous electromagnetic fields, which existing calibration methods struggle to address effectively, especially in real-time surgical navigation applications.

Innovation Solution

A data processing method generates correction or compensation information by estimating a bias field based on position and orientation-dependent measurements, using additional constraints such as motion constraints and sensor data from multiple sources to correct tracking errors, allowing for improved accuracy without requiring extensive recalibration by trained specialists.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If generic calibration procedures are used to minimize tracking inaccuracies, then calibration time is reduced and ease of operation is improved, but systematic errors remain and measurement precision deteriorates

Engineering Contradiction:
Improvecalibration easeVSAvoidtracking accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The system performs preliminary bias field estimation during an initial calibration phase, storing correction data that can be automatically applied during subsequent tracking operations. This preliminary action captures systematic errors under various conditions, allowing the system to maintain high precision without requiring specialists to perform complex recalibrations later.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system continuously estimates bias fields during tracking operations and uses this feedback to dynamically correct position measurements. By monitoring tracking data and updating bias compensation in real-time, the system maintains measurement precision automatically without requiring manual intervention or specialized calibration procedures.

Inventive Principle:
Principle #23Feedback

2Measurement precision

If individual calibration procedures are performed to improve measurement precision and reduce systematic errors, then tracking accuracy is improved, but calibration time increases and device complexity increases

Engineering Contradiction:
Improvetracking accuracyVSAvoidcalibration time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

Comprehensive bias field characterization is performed during an initial calibration phase, capturing systematic errors across the entire tracking volume. This preliminary action creates a lookup table of correction data that can be automatically applied during operations, eliminating the need for time-consuming individual calibrations while maintaining high precision.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system performs automatic bias field estimation and correction during tracking operations without requiring specialist intervention. The calibration process is self-service, using the tracking data itself to identify and correct systematic errors, thereby reducing calibration time and complexity while maintaining measurement precision.

Inventive Principle:
Principle #25Self-service

3Measurement precision

If multiple sensors are combined in hybrid tracking systems to improve measurement precision and reliability, then tracking accuracy is improved, but device complexity increases

Engineering Contradiction:
Improvelocalization accuracyVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The system combines data from multiple sensor types (electromagnetic tracking and optical camera tracking) into a unified bias field estimation model. By merging these data sources, the system achieves more accurate localization than either system alone, while the integrated approach manages complexity through a unified correction framework rather than separate processing systems.

Inventive Principle:
Principle #5Merging (Combining)

4Measurement precision

If bias field estimation is performed continuously to improve measurement precision in dynamic environments, then tracking accuracy is maintained under changing conditions, but use of energy and computational load increase

Engineering Contradiction:
Improvetracking accuracyVSAvoidcomputational energy
Core Design Contradiction:
Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system performs bias field estimation at selective intervals rather than continuously, using partial updates based on when significant environmental changes are detected. This approach maintains tracking accuracy under dynamic conditions by updating corrections when needed, while reducing computational energy consumption by avoiding unnecessary continuous estimation.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentEP3108266B1Estimation and compensation of tracking inaccuracies
Publication Date: 2020.03.18 BRAINLAB AG
  • EP3108266B1 patent drawingFigure 1
  • EP3108266B1 patent drawingFigure 2
  • EP3108266B1 patent drawingFigure 3A

AI summary

A data processing method for generating a compensation information for hacking or for determining the position and/or orientation of an object in space, the method comprising the following steps performed by a computer: a) acquiring a predetermined constraint information defining one or more relative or absolute positions and/or orientations of the object in space; b) acquiring position and/or orientation data of the object while the object is positioned or moved while fulfilling the predetermined constraint; and c) determining the compensation information based on the predetermined constraint information and the acquired position and/or orientation data of the object.