Wireless Inductive Markers for MRI Motion Tracking

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Solution Overview

Problem

Motion artifacts in magnetic resonance (MR) imaging remain a significant challenge, leading to prolonged or diagnostically inadequate studies, and existing motion tracking methods face difficulties in accurately determining the correspondence between wireless markers and their signals, which can result in incorrect diagnoses and increased patient and clinical risks.

Innovation Solution

The use of wireless markers with predetermined relative positions, where the correspondence between marker signals and markers is determined using knowledge of these positions, allowing for position and orientation tracking in MR imaging systems through navigator tracking pulses and inductive coupling to MR receive coils, enabling effective motion correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If wireless markers are used for motion tracking, then patient comfort and safety are improved by eliminating cables, but the correspondence problem between markers and signals becomes more difficult to solve

Engineering Contradiction:

Improvepatient comfortVSAvoidcorrespondence determination complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-determining the relative positions of markers on the object before the MR imaging procedure. This known geometric configuration is stored and used later to solve the correspondence problem by matching observed marker positions to the predetermined configuration, thereby resolving which signal corresponds to which marker without requiring complex real-time identification

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If multiple wireless markers are used to improve tracking accuracy, then measurement precision is improved, but the difficulty of determining signal correspondence increases

Engineering Contradiction:

Improvetracking accuracyVSAvoidsignal correspondence difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent uses predetermined relative positions of multiple markers as a reference configuration. By comparing the spatial relationships observed in the MR signals against this known configuration, the system can accurately identify which signal corresponds to which marker, even with multiple markers present. This approach maintains measurement precision while solving the correspondence problem through geometric matching

Inventive Principle:

Principle #10Preliminary action

3Reliability

If conventional motion tracking methods are used, then the correspondence problem can be addressed, but motion artifacts still result in prolonged studies and reduced diagnostic quality

Engineering Contradiction:

Improvediagnostic qualityVSAvoidstudy duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces mechanical cable-connected tracking systems with wireless MR-visible markers that are inductively coupled to receive coils. This substitution eliminates the need for physical connections while maintaining tracking capability, allowing for more natural patient positioning and reducing artifacts caused by cable-related restrictions, thereby improving diagnostic quality without prolonging study duration

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 provides accurate and reliable 3D motion tracking, improving diagnostic confidence, reducing patient discomfort and healthcare costs, and facilitating high-throughput clinical use by eliminating the need for cables and enhancing tracking accuracy.

Implementation Method 1

the resonant circuits of the markers are inductively coupled to one or more receive coils of the MR imaging system

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

Each marker includes an MR-visible sample coupled to a resonant circuit

Methodology Applied

Scientific EffectMagnetic resonance:

Data Source

PatentUS10591570B2Method for 3D motion tracking in an MRI scanner using inductively coupled microcoils

Publication Date: 2020.03.17 THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIV

AI summary

Wireless markers having predetermined relative positions with respect to each other are employed for motion tracking and/or correction in magnetic resonance (MR) imaging. The markers are inductively coupled to the MR receive coil(s). The correspondence between marker signals and markers can be determined by using knowledge of the marker relative positions in various ways. The marker relative positions can be known a priori, or can be obtained from a preliminary scan. This approach is applicable for imaging (both prospective and retrospective motion correction), spectroscopy, and/or intervention.