MRI Multi-Slice RF Pulse Duration for Artifact Reduction
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Solution Overview
Problem
Slice multiplexing methods in magnetic resonance imaging (MRI) often result in ghosting artifacts due to different phase shifts induced by gradient blips on spins in various tissue types, such as water and fat, leading to suboptimal image quality.
Innovation Solution
A method that determines a minimum RF pulse duration to maximize the amplitude of slice selection gradients, reducing displacements between tissue types and thereby minimizing artifacts, by considering specific recording parameters and system constraints within the MRI system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If slice multiplexing methods are used to record scan data from multiple slices simultaneously, then productivity is improved, but ghosting artifacts appear due to different phase shifts on spins in various tissue types
Solution Approach 1:
The patent changes the parameter of RF pulse duration to a specific minimum value that maximizes the amplitude of slice selection gradients. This parameter change ensures that the phase shifts induced by gradient blips are minimized and equalized across different tissue types (water, fat, etc.), thereby reducing ghosting artifacts while maintaining simultaneous multi-slice recording capability
Solution Approach 2:
The patent applies preliminary anti-action by pre-determining the minimum RF pulse duration before the actual scan. This preliminary setting ensures that the slice selection gradient amplitude is maximized from the outset, preventing the occurrence of differential phase shifts that would otherwise cause ghosting artifacts during the simultaneous recording of multiple slices
2Device complexity
If gradient blips are used for slice selection in multi-slice imaging, then device complexity is reduced, but manufacturing precision deteriorates due to chemical shift-induced phase shifts
Solution Approach 1:
The patent changes the RF pulse duration parameter to a minimum value that maximizes the slice selection gradient amplitude. This parameter change compensates for the chemical shift effects in gradient-blip-based slice selection, ensuring that spins from different tissue types experience equalized phase shifts and maintaining precise slice positioning without increasing device complexity
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 reduces artifacts in simultaneously recorded scan data from multiple slices, enhancing image quality by minimizing the impact of chemical shift-induced phase shifts.
Implementation Method 1
In order to trigger nuclear spin resonances that are measurable as signals, radio-frequency excitation pulses (RF pulses) are radiated into the examination object and the nuclear spin resonances produced are measured as so-called k-space data
Implementation Method 2
through irradiation of at least one RF refocusing pulse following the irradiation of the RF excitation pulse, the transverse magnetization is, so to speak, 'turned' so that the dephased magnetization is rephased again and thus, following a time TE denoted as the echo time following the RF excitation pulse, a so-called spin echo SE is generated
Data Source
AI summary
An improved technique for recording of scan data is provided, which includes recording scan data from at least two slices of an examination object simultaneously by means of a magnetic resonance system. The technique includes selecting a desired simultaneous recording of scan data from at least two slices (S1, . . . , Sn), determining an artifact-preventing minimum RF pulse duration (dRF) for a desired recording, considering desired recording parameters (PA), and performing the desired recording using the determined minimum RF pulse duration.