Magnetic Resonance Pulse Sequence Fat Signal Suppression
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Solution Overview
Problem
Current magnetic resonance imaging techniques face challenges in completely suppressing certain nuclear spin types, such as fat signals, which can complicate anatomical orientation and require additional time and global excitation, limiting dynamic adjustment and image quality.
Innovation Solution
A method using a combined excitation pulse sequence with defined time intervals for selective excitation of one spin type and an additional pulse sequence for partial excitation of another spin type, allowing for synchronized or asynchronous superimposition to achieve partial suppression without additional suppression pulses, enabling dynamic adjustment and improved contrast homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complete suppression of fat signal components is achieved using traditional suppression techniques, then the fat signal is fully suppressed, but additional suppression pulse sequences are required which increase measurement time and prevent dynamic adjustment
Solution Approach 1:
The patent combines the excitation pulse sequence with a spectrally selective suppression pulse sequence into a single integrated sequence. The excitation pulses are designed to selectively excite water spins while the suppression pulses simultaneously suppress fat spins, eliminating the need for separate suppression steps and reducing total measurement time.
Solution Approach 2:
The patent implements dynamic adjustment capability by allowing the excitation parameters (such as flip angles and timing) to be optimized for each individual slice or recording volume. This dynamic optimization was previously impossible when using global suppression pulses, as the system can now adapt parameters locally to achieve both suppression and image quality enhancement.
2Object-affected harmful factors
If complete suppression of fat signal components is achieved using traditional suppression techniques, then the fat signal is fully suppressed, but anatomical orientation becomes complicated
Solution Approach 1:
Instead of complete fat signal suppression, the patent applies partial suppression that reduces fat signal interference while preserving enough fat signal to maintain anatomical context and orientation. This selective partial suppression achieves the beneficial effect of reduced fat interference while retaining the structural information needed for anatomical reference.
3Object-affected harmful factors
If additional suppression pulse sequences are used to suppress fat signals, then fat suppression is achieved, but the excitation period is extended
Solution Approach 1:
The patent merges the excitation and suppression functions into a single pulse sequence where excitation pulses and suppression pulses are interleaved or combined. This integration allows both water excitation and fat suppression to occur within the same time window, eliminating the need for separate suppression periods and maintaining a compact excitation cycle.
Solution Approach 2:
The patent employs periodic suppression pulses that are synchronized with the excitation pulse train. By applying suppression pulses at specific periodic intervals that coincide with the excitation rhythm, the system achieves continuous fat suppression without extending the overall excitation period, maintaining efficient temporal cycling.
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 allows for efficient partial suppression of unwanted spin types, enhancing anatomical orientation and image quality by reducing the excitation period and enabling adjustable fat signal reduction in turbo-spin-echo imaging, while maintaining optimal dynamic adjustment.
Implementation Method 1
nuclear spins in the object are excited by an excitation pulse. During relaxation of this excitation, magnetic resonance signals are emitted
Implementation Method 2
a dedicated, spectrally selective radio-frequency excitation pulse tips the longitudinal magnetization of the spin type to be suppressed into the transverse plane
Implementation Method 3
where it is dephased by spoiler gradients (dephasing gradients)
Implementation Method 4
a dedicated, spectrally selective radio-frequency inversion pulse inverts the longitudinal magnetization of the spin species to be suppressed
Data Source
AI summary
In a method and magnetic resonance (MR) apparatus for different degrees of excitation of two different nuclear spin types with Larmor frequencies that are shifted relative to one another during recording of MR data by execution of an MR sequence, an excitation pulse sequence with at least two consecutive excitation pulses with defined time intervals for the exclusive excitation of the first spin type, and an additional pulse sequence with at least one additional pulse that acts at least on the second spin type, are used. A total pulse sequence formed by superimposition of the two pulse sequences is emitted within an excitation period of the MR sequence.