Hall Effect Current Sensor for MRI Transmit Coil Measurement

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Solution Overview

Problem

In magnetic resonance imaging (MRI), direct measurement of current in transmit coils is challenging due to space constraints and electrical interference, leading to inaccurate indirect measurements.

Innovation Solution

The implementation of Hall effect current sensors with a planar portion oriented perpendicular to the magnetic field, which measures differential voltage to determine current, and includes amplifiers and voltage sensors for accurate current measurement and feedback control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If direct measurement methods are used, then measurement precision is improved, but device complexity and space requirements increase making it infeasible in MRI apparatus

Engineering Contradiction:

Improvecurrent measurement accuracyVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces a Hall effect sensor as an intermediary device that indirectly measures current by detecting the magnetic field generated by the current flow. This mediator approach allows accurate current measurement without direct electrical contact or complex wiring, resolving the contradiction between measurement precision and device complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces traditional electrical measurement methods with a magnetic field-based detection system. By substituting direct electrical measurement with Hall effect sensing, the system achieves accurate current measurement while avoiding the complexity and space requirements of traditional direct measurement apparatus.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If indirect measurement methods are used, then device complexity is reduced, but measurement precision deteriorates due to interference and coupling effects

Engineering Contradiction:

Improvemeasurement system complexityVSAvoidcurrent measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent extracts the measurement function from the main current path by using a separate Hall effect sensor that detects the magnetic field surrounding the conductor. This separation eliminates coupling effects and interference from adjacent coils, maintaining measurement precision while keeping the system simple.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The Hall effect sensor acts as an intermediary that measures current indirectly through magnetic field detection, avoiding direct electrical contact. This intermediary approach prevents interference and coupling effects while maintaining measurement accuracy, resolving the contradiction between simplicity and precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If traditional sensing methods are used, then ease of operation is maintained, but measurement reliability deteriorates due to electrical interference from MRI components

Engineering Contradiction:

Improvemeasurement operation simplicityVSAvoidmeasurement accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces electrical sensing methods with magnetic field-based Hall effect sensing. This substitution eliminates susceptibility to electrical interference from MRI components while maintaining ease of operation, as the Hall effect sensor requires no direct electrical connection to the current-carrying conductor.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The Hall effect sensor creates an electrically isolated measurement environment by detecting magnetic fields rather than making electrical contact. This inert measurement approach protects against electrical interference from surrounding MRI components, improving reliability while keeping operation simple.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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

Enables precise current measurement and feedback control in MRI transmit coils, reducing measurement errors from interference and load changes, and allows for accurate estimation of Specific Absorption Ratios (SARs).

Implementation Method 1

Due to the Hall effect, the magnetic field B0 will cause the current flowing in the perpendicular planar portion 120 to be distributed unevenly across the planar portion 120. This uneven current distribution generates a differential voltage, VH, across the planar portion 120

Methodology Applied

Scientific EffectHall effect: Hall Effect

Data Source

PatentUS8378683B2Hall effect current sensor

Publication Date: 2013.02.19 CASE WESTERN RESERVE UNIV

AI summary

Example systems, apparatus, circuits, and so on described herein concern a Hall effect current sensor that includes a planar portion of a conductor that is oriented perpendicular to a base magnetic field in which it is located. In the presence of the magnetic field, a differential voltage is produced across the planar portion that is proportional to a strength of the magnetic field and the amount of current flowing through the conductor.