Multi-Slice MRI Acquisition Order Optimization
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Solution Overview
Problem
Multi-slice magnetic resonance imaging (MRI) techniques like HASTE sequences face challenges with crosstalk and magnetization transfer effects, leading to signal attenuation and artefacts due to non-ideal slice shapes and RF pulse sequences, which are exacerbated in two-dimensional acquisitions and breath-hold imaging.
Innovation Solution
An iterative odd/even slice data acquisition method is implemented, determining an optimal slice acquisition order using specific general formulas to maximize the effective gap between slices and time intervals, reducing crosstalk and magnetization transfer effects while shortening repetition time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If multi-slice HASTE sequence is used for breath-hold abdominal imaging, then acquisition time is reduced, but crosstalk between slices causes artefacts and signal-to-noise ratio decrease
Solution Approach 1:
The patent segments the multi-slice acquisition into multiple fractional acquisitions (first fractional acquisition, second fractional acquisition, etc.) and applies different odd/even slice ordering patterns to each segment. This segmentation allows the system to maintain short total acquisition time while reducing intra-segment crosstalk between adjacent slices.
Solution Approach 2:
The patent inverts the conventional slice acquisition ordering by implementing odd/even ordering patterns where odd-numbered slices are acquired in one sequence and even-numbered slices in another. This inversion strategy maximizes the temporal separation between excitations of adjacent slices, reducing magnetization transfer effects and crosstalk while maintaining fast acquisition.
2Loss of time
If TSE sequence with short echo chains is used, then acquisition time is shortened, but magnetization transfer effect causes contrast alteration and signal attenuation
Solution Approach 1:
The patent implements periodic odd/even slice ordering across multiple fractional acquisitions, creating a periodic pattern in slice excitation timing. This periodic structure ensures that magnetization transfer effects are distributed uniformly and can be corrected through the iterative reconstruction process, while maintaining the short acquisition time required for breath-hold imaging.
Solution Approach 2:
The patent employs iterative reconstruction that incorporates feedback from the observed crosstalk and magnetization transfer effects to refine the final image. The reconstruction process uses the known odd/even ordering pattern and fractional acquisition structure to compensate for signal attenuation and contrast alterations, recovering accurate tissue contrast despite the accelerated acquisition.
3Productivity
If RF pulse sequence is applied to one slice, then that slice is excited, but neighboring slices experience off-resonance magnetization transfer leading to signal attenuation
Solution Approach 1:
The patent introduces a temporal dimension to the slice ordering problem by distributing odd and even slices across different fractional acquisitions in time. This temporal separation transforms the spatial proximity problem into a temporal sequencing solution, allowing all slices to be covered (high productivity) while minimizing magnetization transfer between neighboring slices through optimized timing.
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 method optimizes slice data acquisition, significantly reducing artefacts and signal attenuation, preserving signal-to-noise ratio and contrast, and allowing for shorter acquisition times and breath-hold durations in MRI systems.
Implementation Method 1
Magnetic resonance imaging (MRI) is a technology in which the phenomenon of magnetic resonance is utilized for the purpose of imaging
Implementation Method 2
the excited atomic nuclei emit an echo signal, gradually releasing the absorbed energy in the form of electromagnetic waves
Implementation Method 3
A radio frequency (RF) pulse of a specific frequency is used to excite the atomic nuclei in the external magnetic field such that their spin axes deviate from the positive longitudinal axis or negative longitudinal axis
Data Source
AI summary
In a multi-slice data acquisition method and device and a magnetic resonance imaging method and apparatus, a number NC of fractional acquisitions and a number NS of slice individual, complete data acquisition of the multi-slice data acquisition are determined. Using an iterative odd/even arranging method, a slice data acquisition order of each of the fractional acquisitions is arranged according to an ideal number of iterations. The ideal number of iterations is obtained from multiple undetermined numbers j of iterations of the iterative odd/even arranging method according to the number NS of slice data and the number NC of fractional acquisitions. This multi-slice data acquisition method optimizes the slice data acquisition order so as to significantly reduce the effect of magnetization transfer and crosstalk.