Gradient-Balanced SSFP Sequences for Motion-Insensitive Cardiac T2 Imaging
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Solution Overview
Problem
Current magnetic resonance imaging methods for edema imaging in the heart are susceptible to movement artifacts and require high radio-frequency transmitter capacity and SAR exposure, limiting their application due to sensitivity to myocardial movement and inhomogeneities in the magnetic field.
Innovation Solution
A method using gradient-balanced SSFP sequences to generate spatially resolved, quasi-T2-weighted magnetic resonance signals by constructively superimposing signals from two SSFP sequences with opposite longitudinal magnetization directions, reducing movement artifacts and allowing for improved T2 contrast without significant T1 contributions, and utilizing the Trufi sequence for reduced SAR exposure and increased signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a turbo spin echo sequence (TSE sequence) with T2-weighted reordering is used for edema imaging, then T2-weighted contrast can be achieved, but the sequence becomes relatively susceptible to movement artifacts
Solution Approach 1:
The patent applies inversion by using two SSFP sequences with opposite longitudinal magnetization directions (positive and negative). By constructively superimposing these inverted sequences, the method achieves T2-weighted contrast while canceling out T1-weighted contrast and reducing movement susceptibility, thus resolving the contradiction between achieving T2 contrast and maintaining reliability against movement artifacts
2Measurement precision
If a hybrid method using Trufi sequence with T2 preparation module or 180° pulse series is used, then T2-weighted representation can be generated, but high SAR exposure and high demands on radio-frequency transmitter capacity occur
Solution Approach 1:
The patent changes the sequence parameters by using gradient-balanced SSFP sequences without requiring high-power T2 preparation pulses or 180° pulse series. This parameter change achieves T2-weighted contrast while significantly reducing SAR exposure and radio-frequency transmitter demands, resolving the contradiction between measurement precision and energy consumption
3Measurement precision
If Trufi signal acquisition is used after excitation with 180° pulse series, then T2-weighted contrast can be achieved, but transient contrast occurs where optimal edema contrast transitions to T1/T2-determined contrast
Solution Approach 1:
By using two SSFP sequences with inverted longitudinal magnetization directions and constructively superimposing them, the method eliminates transient contrast transitions and achieves stable T2-weighted contrast throughout the acquisition, resolving the contradiction between achieving T2 contrast and maintaining contrast stability
4Measurement precision
If T2 preparation pulse is used in hybrid method, then T2-weighted contrast can be achieved, but the preparation pulse becomes susceptible to inhomogeneities of the basic magnetic field
Solution Approach 1:
The patent changes the approach by using gradient-balanced SSFP sequences that do not require T2 preparation pulses. This eliminates susceptibility to magnetic field inhomogeneities while maintaining T2-weighted contrast capability, resolving the contradiction between measurement precision and reliability against field inhomogeneities
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 provides robust, motion-insensitive quasi-T2-weighted imaging with reduced artifacts and lower SAR exposure, enabling effective edema imaging with improved contrast and visibility of T2 relaxation constants, particularly suitable for cardiac imaging.
Implementation Method 1
generate spatially resolved, quasi-T2-weighted magnetic resonance signals from an examination region with a first gradient-balanced SSFP sequence (bSSFP sequence), wherein an initial magnetization is generated having a longitudinal direction component in a first direction, wherein spatially coded first magnetic resonance signals from the first gradient-balanced SSFP sequence are detected during the transient portion of the first SSFP sequence
Implementation Method 2
the first and second magnetic resonance signals are constructively superimposed into overlay signals. The overlay signals are additionally processed into image data with a predominant T2 weighting, or for spatially resolved estimation of the T2 relaxation time constant
Implementation Method 3
The subsequent signal acquisition takes place according to the Trufi method. In a first variant, the Trufi sequence is incorporated into a hybrid method and uses a T2 preparation module
Data Source
AI summary
In a magnetic resonance method and device to generate spatially resolved, quasi-T2-weighted magnetic resonance signals from an examination region, an initial magnetization is flipped in a first direction with a first gradient-balanced SSFP sequence. Spatially coded first magnetic resonance signals from the first gradient-balanced SSFP sequence are detected during the transient portion of the first SSFP sequence. An initial magnetization is flipped in a direction opposite the first direction with a second gradient-balanced SSFP sequence. Spatially coded second magnetic resonance signals from the second gradient-balanced SSFP sequence during the transient portion of the second gradient-balanced SSFP sequence. The first and second magnetic resonance signals are constructively superimposed into overlay signals. Image data with a predominant T2 weighting are reconstructed from the overlay signals, or are used for spatially resolved estimation of the T2 relaxation time constant.