B1+ Mapping Near Metallic Hardware Using Optimized Scaling Factors

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Solution Overview

Problem

Existing B1+ mapping techniques fail near metallic hardware due to inhomogeneity of the transmit B1+ field and susceptibility-induced phase distortions.

Innovation Solution

A method and system for B1+ mapping near metallic hardware using turbo-spin echo or Slice Encoding for Metal Artifact Correction (SEMAC) acquisitions, which includes obtaining a scaling factor by optimizing a function of an acquired dataset and a simulated dataset, incorporating apriori knowledge of signal evolution from simulated Bloch equations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional B1+ mapping techniques are used, then B1+ mapping can be performed in homogeneous regions, but the mapping fails near metallic hardware due to inhomogeneity of the transmit B1+ field and susceptibility-induced phase distortions

Engineering Contradiction:

ImproveB1+ mapping reliabilityVSAvoidsusceptibility artifacts

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful susceptibility-induced phase distortions and B1+ inhomogeneities near metallic hardware into beneficial information by using these distortions as contrast mechanisms. By acquiring images at multiple flip angles and using the distorted signal patterns to calculate B1+ maps, the method turns the previously unusable region into a valuable measurement area, enabling B1+ mapping even in the presence of metal implants.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the acquisition parameters by using multiple flip angles (e.g., 30°, 60°, 90°, 120°) instead of a single flip angle. This parameter variation allows the system to distinguish between signal changes caused by B1+ inhomogeneity and those caused by susceptibility artifacts. The optimized function compares signals at different flip angles to calculate the B1+ scaling factor, making the measurement robust against metallic hardware interference.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If B1+ mapping is performed near metallic objects, then spatial variation of flip angles can be measured, but the inhomogeneity of the transmit B1+ field causes mapping failure

Engineering Contradiction:

ImproveB1+ mapping precisionVSAvoidmapping success rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements a feedback mechanism through an optimized function that continuously compares the acquired signal data with simulated Bloch equation predictions. The function iteratively adjusts the B1+ scaling factor estimate until the difference between acquired and simulated signals is minimized. This feedback loop compensates for B1+ inhomogeneity by adapting the scaling factor to match the actual signal behavior, ensuring precise B1+ mapping even near metallic objects where the field is highly inhomogeneous.

Inventive Principle:

Principle #23Feedback

3Ease of manufacture

If conventional mapping methods are used, then simple acquisition protocols can be used, but they cannot resolve B1+ values in the presence of metal-induced artifacts

Engineering Contradiction:

Improveacquisition simplicityVSAvoidB1+ information loss

Core Design Contradiction:

Ease of manufactureVSLoss of information

Solution Approach 1:

The patent performs preliminary actions by acquiring multiple images at different flip angles before performing the B1+ mapping calculation. These preliminary acquisitions capture the signal behavior across a range of excitation strengths, providing the necessary data for the subsequent optimized function to extract accurate B1+ values. This preliminary multi-angle acquisition strategy ensures that sufficient information is gathered even before the complex analysis begins, preventing information loss in the presence of metal artifacts.

Inventive Principle:

Principle #10Preliminary action

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 method effectively decreases metal-related susceptibility artifacts and resolves B1+ values from signal variations, providing promising results especially near the metal surface, where other techniques fail.

Implementation Method 1

a magnetic resonance imaging system can include at least one processor. The magnetic resonance imaging system can include a memory with computer code instructions stored thereon

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The simulated dataset can include a first signal from a first pulse having a first excitation flip angle and a first refocusing flip angle. The simulated dataset can include a second signal from a second pulse having a second excitation flip angle and a second refocusing flip angle

Methodology Applied

Scientific EffectMagnetic resonance:

Data Source

PatentUS12313710B2B1+ mapping near metallic hardware

Publication Date: 2025.05.27 SIEMENS HEALTHINEERS AG

AI summary

A method can include obtaining a scaling factor for a location proximate a metallic object by optimizing a function of an acquired dataset and a simulated dataset. The simulated dataset can include a first signal from a first pulse having a first excitation flip angle and a first refocusing flip angle. The simulated dataset can include a second signal from a second pulse having a second excitation flip angle and a second refocusing flip angle.