MRI Coil Weighting for Respiratory Motion Tracking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing MRI techniques face challenges in accurately tracking respiratory motion during coronary magnetic resonance angiography due to artefacts caused by patient movement, particularly due to subcutaneous fat and low-pass filtering effects that degrade navigator image quality.

Innovation Solution

A method using a weighted combination of signals from multiple coils in an MRI apparatus, where coils closer to the region of interest are weighted higher, and those farther away or contributing less are weighted lower, to enhance signal quality and reduce unwanted signals, while also counteracting low-pass filtering effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a sum-of-squares combination of all coil signals is used to generate navigator images, then all available signal data is utilized, but signals from subcutaneous fat and other areas overlay the region of interest and degrade tracking results

Engineering Contradiction:

Improvesignal data utilizationVSAvoidmotion tracking accuracy

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent applies local quality by assigning different weights to different coils based on their spatial relationship to the region of interest. Coils closer to or overlapping with the ROI receive higher weights, while coils contributing primarily to subcutaneous fat signals receive lower weights. This selective weighting enhances the signal quality from the target area while suppressing unwanted signals from surrounding tissues.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the contribution of each coil to the navigator image by determining individual coil weights. Instead of treating all coils uniformly, the method separates and independently evaluates each coil's signal contribution, allowing selective enhancement or suppression of specific spatial regions through weighted combination.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If navigator images are obtained during the ramp-up stage of bSSFP sequence, then the preparation pulses can be utilized for motion tracking, but the low-pass filtering effect removes important high-frequency information from the navigator images

Engineering Contradiction:

Improvesequence integrationVSAvoidhigh-frequency signal information

Core Design Contradiction:

Ease of manufactureVSLoss of information

Solution Approach 1:

The patent applies preliminary action by determining coil weights during a prescan phase before the actual imaging sequence. This preliminary determination of spatial weighting factors allows the system to prepare for optimal signal combination in advance, enabling the main sequence to proceed without requiring additional time for weight calculation while still achieving enhanced signal quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of coil signal weighting from uniform to spatially-dependent. By introducing spatially-varying weights that reflect the geometric relationship between coils and the region of interest, the method transforms the signal combination process to preserve high-frequency information that would otherwise be lost in uniform averaging.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If coils farther from the region of interest are included in the navigator image generation, then more signal data is available, but the signal from subcutaneous fat and chest wall overlays and degrades the tracking result

Engineering Contradiction:

Improvesignal data availabilityVSAvoidsignal overlay from subcutaneous fat

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the potentially harmful effect of including distant coils (which introduce subcutaneous fat signals) into a benefit by using their spatial information. The prescan data from these coils is used to determine appropriate weighting factors, allowing the system to optimally combine signals while minimizing the harmful overlay effects through the weighted summation.

Inventive Principle:

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

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 improves motion tracking accuracy by enhancing the signal from the target object and reducing noise from outside sources, leading to clearer navigator images and better respiratory motion tracking.

Implementation Method 1

magnetic resonance imaging (MRI) apparatus

Methodology Applied

Scientific EffectMagnetic resonance:

Implementation Method 2

The preparation pulses of a balanced steady-state free precession (bSSFP) sequence may be used to acquire low resolution navigator images

Methodology Applied

Scientific EffectRadio frequency pulse excitation:

Data Source

PatentUS11253154B2Method and system for magnetic resonance imaging

Publication Date: 2022.02.22 SIEMENS HEALTHINEERS AG

AI summary

A method and system for imaging a body using a magnetic resonance imaging (MRI) apparatus, including motion tracking of a target object of the body using MRI by generating an MRI image of a region of interest of the body by performing a weighted combination of a signal received by each coil of an MRI apparatus during an MRI scan.