Magnetic Tracking Distortion Compensation for Surgical Accuracy

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Solution Overview

Problem

Magnetic tracking systems face inaccuracies due to the distortion of magnetic fields caused by metallic components of imaging devices like X-ray image intensifiers, which are not adequately accounted for by existing algorithms during surgical procedures.

Innovation Solution

A method and system for improving magnetic tracking accuracy by generating and sensing magnetic fields, collecting data with and without a movable magnetic-field distorter present, calculating the difference in field data, and using this information to correct the position and orientation of a magnetic-field sensor, thereby compensating for field distortions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetic tracking is used to guide surgical instruments, then real-time positioning accuracy is improved, but the presence of metallic imaging devices like C-arms causes magnetic field distortion that deteriorates measurement precision

Engineering Contradiction:

Improveposition and orientation determination accuracyVSAvoidmagnetic field distortion from metallic imaging devices

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary mapping of the magnetic field in the tracking volume before the actual surgical procedure. This pre-acquired magnetic field data serves as a reference to later compensate for distortions caused by metallic imaging devices during surgery, allowing the system to correct position and orientation measurements in real-time

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors the magnetic field during the surgical procedure and compares real-time measurements against the pre-acquired reference data. When distortions are detected from metallic devices, the system calculates correction factors and applies them to maintain accurate position and orientation determination throughout the procedure

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If a C-arm imaging device is used during surgery, then real-time imaging capability is improved, but the metallic components cause magnetic field distortion that worsens tracking accuracy

Engineering Contradiction:

Improvereal-time imaging capability during surgeryVSAvoidmagnetic tracking accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system introduces a computational intermediary layer that processes the relationship between the C-arm's position and the magnetic field distortions it causes. By mapping the C-arm's movement and correlating it with field distortions, the system calculates compensation transformations that allow both the C-arm imaging and magnetic tracking to coexist accurately

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system dynamically adjusts tracking parameters based on the C-arm's position and orientation. When the C-arm is present in the tracking volume, the system modifies the magnetic field interpretation parameters using the pre-acquired distortion maps, allowing accurate tracking to continue despite the presence of the imaging device

Inventive Principle:

Principle #35Parameter changes

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 approach enhances the accuracy of magnetic tracking systems by accounting for distortions caused by large, movable objects, such as C-arms, allowing for more precise localization of surgical instruments during procedures.

Implementation Method 1

generating a magnetic field capable of being sensed by a magnetic-field sensor

Methodology Applied

Scientific EffectElectromagnetic field generation: Electromagnetic Induction

Implementation Method 2

sensing magnetic fields, and computing the position and orientation (P&O) of a device using the sensed fields

Methodology Applied

Scientific EffectMagnetic field sensing: Magnetic Field

Implementation Method 3

the device causes significant inaccuracies in the determination of the P&O. This inaccuracy is caused by the distortion of the magnetic field due to the metallic components of the imaging device

Methodology Applied

Scientific EffectMagnetic field distortion: Magnetic Field

Data Source

PatentUS8228028B2Systems and methods for compensating for large moving objects in magnetic-tracking environments

Publication Date: 2012.07.24 ASCENSION TECHNOLOGY CORP

AI summary

Methods for accurately tracking position and orientation of a magnetic-field sensor in a tracking volume when a large magnetic-field distorter is present in the tracking volume. In some of the methods, magnetic field data is collected from within the tracking volume both with and without the large magnetic-field distorter present in the tracking volume. This data is used to obtain correction information that is subsequently used during real-time operation of the magnetic-field sensor to correct the position and orientation solutions for the sensor for magnetic-field distortions caused by the presence of the large magnetic-field distorter in the tracking volume. Others of the methods involve modeling the large magnetic-field distorter using dipole and multipole modeling. Magnetic tracking systems for implementing the methods include hardware and software for carrying out the methods.