Simultaneous Multislice MRI Acquisition with Dynamic Slice Grouping
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Solution Overview
Problem
Current simultaneous multi-slice (SMS) magnetic resonance imaging techniques are limited in imaging thin layers and layer stacks, such as in prostate, spine, or orbital imaging, due to insufficient variation in sensitivity distribution of receiving coils, leading to suboptimal image quality and separation of signals from multiple layers.
Innovation Solution
A method that uses multi-band RF pulses and slice separation calibration data to record MR signals from multiple layers within a minimized repetition time, allowing for increased distance between slices and improved sensitivity distribution, enabling better separation of signals and enhanced image quality by incorporating additional layers and reducing flip angles for supernumerary layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If multiple slices are acquired simultaneously using SMS techniques, then the repetition time and total acquisition time are reduced, but the distance between slices must be sufficiently large to ensure sufficient variation in sensitivity distribution for signal separation
Solution Approach 1:
The patent dynamically adjusts the slice position assignment in each slice group based on the specific examination protocol and patient anatomy. The control device automatically optimizes which slices are included in each slice group and their spatial arrangement, allowing the system to adapt to different clinical scenarios while maintaining sufficient sensitivity variation for signal separation.
Solution Approach 2:
The patent changes the parameter of slice distance by forming multiple slice groups where slices within each group are spaced sufficiently apart in the slice direction. This spatial parameter adjustment ensures that the sensitivity distribution of receiving coils varies enough to enable effective signal separation, while still allowing multiple slices to be acquired simultaneously.
2Measurement precision
If slices are selected far apart from each other to increase sensitivity distribution variation, then signal separation improves, but the coverage of the slice stack is reduced
Solution Approach 1:
The patent segments the slice stack into multiple slice groups, where each group contains a subset of slices that are spaced apart from each other. This segmentation allows the system to maintain sufficient distance between slices within each group for effective signal separation, while the collection of all slice groups collectively covers the entire slice stack.
Solution Approach 2:
The patent creates a universal solution that works for both thin-layer applications (prostate, spine, orbital imaging) and thicker slice stacks. The control device automatically determines the optimal number and configuration of slice groups based on the total number of slices and examination protocol, making the system adaptable to various clinical scenarios.
3Area of stationary object
If the number of slice groups is increased to cover more slices, then the slice stack coverage improves, but the repetition time increases
Solution Approach 1:
The system dynamically determines the optimal number of slice groups based on the repetition time constraint and the total number of slices to be imaged. The control device calculates how many slice groups can be acquired within the available repetition time while still covering the required slice stack, automatically adjusting the configuration to balance coverage and time.
4Loss of time
If SMS techniques are used for thin slice stacks (less than 4 cm), then the acquisition time is reduced, but the sensitivity distribution variation is insufficient for effective signal separation
Solution Approach 1:
For thin slice stacks, the patent segments the limited number of slices into slice groups with carefully selected slice assignments. By ensuring that slices within each group are positioned to maximize sensitivity variation, the system achieves effective signal separation even with the limited spatial extent of thin slice stacks.
Solution Approach 2:
The patent applies local quality optimization by assigning specific slices to specific slice groups based on their local position and the sensitivity profile of the receiving coils. This localized optimization ensures that each slice group has sufficient sensitivity variation for effective signal separation, tailored to the specific geometry of the thin slice stack.
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 improved image quality and increased distance between slices, enabling effective separation of signals from multiple layers, particularly in thin layer applications like prostate or orbital imaging, by optimizing the repetition time and sensitivity distribution, thus enhancing diagnostic image data.
Implementation Method 1
Magnetic resonance imaging (MR) is a well-known technique for generating images of the interior of an object under examination. Simply put, the object under examination is positioned in a magnetic resonance scanner in a comparatively strong, static, homogeneous basic magnetic field, also known as the B0 field
Implementation Method 2
To trigger nuclear magnetic resonance imaging, high-frequency excitation pulses (RF pulses) are radiated into the object under examination. The resulting nuclear magnetic resonances are measured as k-space data
Implementation Method 3
To spatially encode the measurement data, rapidly switched magnetic gradient fields, or gradients for short, are superimposed on the basic magnetic field
Implementation Method 4
well-known SMS methods include methods from the aforementioned PPA imaging, in which knowledge of the sensitivity distribution of the receiving coils used to acquire the measurement data is used as additional information to fill in undersampled measurement data
Data Source
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AI summary
In an inventive method for improved acquisition of measurement data of a test object using a magnetic resonance imaging (MRI) system with the aid of a simultaneous multislice (SMS) method, a minimum repetition time (TR) is determined as a function of a quality criterion. This quality criterion extends the measurement time for the MR signals of the slice stack to be acquired, which is actually significantly reduced by the use of an SMS method, to the minimum repetition time (TR). The resulting "time reserve" (the difference between the determined minimum repetition time (TR) and the measurement time required for the slice stack using only the SMS method) is utilized according to the invention to include additional slices in the acquisition of the MR signals. This allows for the acquisition of further information and also improves the image quality of the acquired image data.