Parallel Slice Excitation MRI System with Spectral Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MRI techniques are limited in acquiring multiple slices simultaneously due to overlapping echo signals in time and frequency, leading to aliasing issues and restricted slice acquisition numbers, especially in imaging the human heart where only 2-4 slices can be acquired at most.
Innovation Solution
The method involves simultaneous acquisition of multiple slices using one or more RF excitation pulses with a slice selection gradient, employing spatially separate RF reception antennas and spectral separation of measurement signals during readout, allowing for reduced slice intervals and improved sensitivity profiles, enabling up to 9 slices to be acquired in parallel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple slices are acquired simultaneously using spatially separated RF reception antennas, then the number of slices that can be acquired simultaneously increases, but the slice interval must be sufficiently large to ensure spatial separation
Solution Approach 1:
The patent transitions from purely spatial separation (one dimension) to combined spatial and spectral separation (two dimensions). By introducing frequency encoding along the slice direction and utilizing the spectral domain as an additional dimension for signal separation, the method overcomes the limitation of requiring large spatial intervals between slices.
Solution Approach 2:
The patent changes the separation criterion from spatial distance alone to a combination of spatial position and spectral frequency. By encoding slices with different frequencies in addition to their spatial positions, the system can distinguish between closely spaced slices that would otherwise be indistinguishable.
2Measurement precision
If RF reception antennas are downsized to improve spatial sensitivity, then sensitivity to nearby slices improves, but the acquisition volume is reduced and middle portions of slices cannot be sufficiently acquired
Solution Approach 1:
The patent adds the spectral dimension to the spatial sensitivity problem. Instead of relying solely on spatial proximity for signal detection, the system uses frequency encoding to extend the effective acquisition volume along the slice direction, allowing smaller antennas to capture signals from deeper within the slice stack.
3Productivity
If spectral separation is used to acquire multiple slices simultaneously, then the frequency interval between slices must be sufficiently large, but this limits the number of slices that can be acquired
Solution Approach 1:
The patent segments the frequency spectrum into distinct bands for different slices, with each slice assigned a specific frequency range. This systematic segmentation of the spectral domain allows for efficient utilization of available bandwidth and maximizes the number of simultaneously acquirable slices.
Solution Approach 2:
The patent combines spatial segmentation (multiple antennas at different positions) with spectral segmentation (frequency encoding), creating a two-dimensional separation scheme that multiplies the capacity for simultaneous slice acquisition compared to using either dimension alone.
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 reduces noise and enhances image quality by allowing more slices to be acquired simultaneously, particularly in the human heart, while maintaining an advantageous pixel sensitivity profile and minimizing radiation exposure.
Implementation Method 1
a frequency coding gradient Gx which codes the frequency in the slice direction perpendicular to the slice stack direction is switched simultaneously with the slice selection gradient Gz during the readout of the measurement signals from the multiple slices, whereby a partial spectral separation of the measurement signals from the different slices is achieved
Implementation Method 2
one or more RF excitation pulses that excite (Flip) nuclear spins in a subject... a single RF pulse is radiated along the direction of the slice stack in a predetermined of segment 24, whereby RF energy is applied simultaneously across multiple frequency bands in order to excite the spins in multiple parallel slices at the same time
Data Source
AI summary
In a method and a magnetic resonance (MR) system and method to generate MR image data of a predetermined volume segment within an examination subject, multiple slices of the volume segment are simultaneously excited by at least one RF excitation pulse, and during the excitation a slice selection gradient is switched. The measurement signals from the multiple slices are acquired with multiple RF reception antennas, at least some of which are spaced along the propagation direction of the slice selection gradient. During the acquisition of the measurement signals the slice selection gradient is switched in order to achieve a spectral separation of the measurement signals of different slices. The MR image data are generated from the measurement signals.