MRI Saturation Pulse Flip Angle Optimization for Background Suppression

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Solution Overview

Problem

Conventional MRI systems face challenges in effectively suppressing background signals in MRA images, leading to partial recovery of tissue and venous blood signals before data acquisition, increased specific absorption rate (SAR), and susceptibility to artifacts due to field inhomogeneities.

Innovation Solution

The use of optimized flip angle saturation pulses, applied in a sequence that includes a configurable delay to ensure arterial blood inflow and saturation of venous blood, with techniques such as double background saturation and single saturation pulses for both tissue and blood, to control longitudinal magnetization and minimize background signal during data acquisition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional saturation pulses are used in MRA imaging, then the imaging process can be completed, but background signals from tissue and venous blood partially recover before data acquisition, reducing image quality

Engineering Contradiction:

Improvebackground suppression effectivenessVSAvoidsignal suppression reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies parameter changes by optimizing the flip angle of saturation pulses. Instead of using conventional fixed flip angles (e.g., 90 degrees), the system calculates and applies optimized flip angles that account for T1 relaxation times of different tissues and blood types. This parameter optimization ensures complete saturation of background signals while maintaining arterial blood signal strength, directly resolving the contradiction between background suppression effectiveness and signal suppression reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamics by making the saturation pulse flip angle adjustable and adaptable rather than fixed. The system dynamically selects flip angles based on calculated T1 values for different tissue types and blood conditions. This dynamic adjustment allows the saturation pulses to adapt to varying physiological conditions, ensuring reliable background suppression across different patients and imaging scenarios.

Inventive Principle:

Principle #15Dynamics

2Productivity

If conventional saturation pulses are used, then imaging can proceed, but specific absorption rate (SAR) increases

Engineering Contradiction:

Improveimaging throughputVSAvoidspecific absorption rate

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent reduces SAR by changing the flip angle parameter of saturation pulses from conventional high values to optimized lower values. By calculating T1 relaxation times and determining optimal flip angles that achieve complete saturation with minimal energy input, the system maintains imaging productivity while significantly reducing the specific absorption rate, thus resolving the contradiction between imaging throughput and energy consumption.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If conventional saturation pulses are used, then data acquisition can be performed, but field inhomogeneities cause artifacts in the images

Engineering Contradiction:

Improvedata acquisition efficiencyVSAvoidartifacts from field inhomogeneities

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent mitigates field inhomogeneity artifacts by optimizing the flip angle parameter to account for varying T1 values across different tissue types and spatial locations. By adjusting flip angles based on calculated T1 values that reflect actual tissue conditions, the system compensates for field inhomogeneities and reduces artifact formation, maintaining data acquisition efficiency while improving image quality.

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 significantly improves background suppression in MRA images, reducing artifacts and SAR, while optimizing the inflow effect and enhancing diagnostic quality by ensuring minimal residual background and venous blood signals at the time of data acquisition.

Implementation Method 1

magnetic resonance imaging (MRI)... nuclear magnetic resonance (NMR) spins

Methodology Applied

Scientific EffectMagnetic resonance:

Implementation Method 2

RF pulses... radio frequency (RF) coil... transmit RF signals

Methodology Applied

Scientific EffectRadiofrequency excitation:

Implementation Method 3

longitudinal magnetization... T1 relaxation curves... magnetization recovery

Methodology Applied

Scientific EffectSpin-lattice relaxation:

Data Source

PatentUS9498139B2Background suppression by time dependent flip angle of saturation pulses

Publication Date: 2016.11.22 TOSHIBA MEDICAL SYST CORP

AI summary

A magnetic resonance imaging (MRI) system, method and/or computer readable storage medium is configured to effect QISS (quiescent interval single shot) MR imaging (e.g., MR angiography or MRA) where an optimized flip angle for one or more initial saturation pulses minimizes background signal from tissue and/or venous blood. Upon expiration of first configurable time interval from a start of a scan interval, at least one saturation pulse having a flip angle greater than ninety degrees is applied so that longitudinal magnetization of background tissue and venous blood in the selected area is approximately at a null value at the beginning of a readout time (occurring upon expiry of a second time interval) and/or when a lowest frequency of k-space data is acquired for the selected area.