Multi-band RF Pulse for Artifact-Free MR Slice Multiplexing
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Solution Overview
Problem
Current magnetic resonance (MR) slice multiplexing methods face challenges in combining the advantages of single-shot techniques like HASTE with slice multiplexing, leading to artifacts due to differences in scanning parameters and movement-induced issues during reference data acquisition.
Innovation Solution
A method that uses a multi-band RF excitation pulse to simultaneously manipulate magnetization in multiple slices, acquiring echo signals and reference data in a central region of k-space to create a complete data set, with reference data acquired close to slice scan data to minimize movement artifacts, and calibration data used to separate and reconstruct single-slice data sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference data is acquired separately from slice scan data, then calibration can be performed, but movement artifacts occur due to inconsistent scanning conditions
Solution Approach 1:
The patent combines the acquisition of slice scan data and reference data into a single integrated process. Multiple slices are simultaneously excited using multi-band RF pulses, and both slice scan data and reference data are acquired during the same scan event without separate acquisition phases, ensuring consistent scanning conditions and eliminating movement artifacts between calibration and imaging
Solution Approach 2:
Reference data is acquired in the same scan event as slice scan data, with the timing and conditions predetermined and synchronized. The reference data acquisition is embedded within the slice scan sequence, ensuring that calibration data is collected under identical physiological and scanning conditions as the diagnostic data
2Loss of time
If single-shot HASTE sequence is used for multiple slices, then scan time is reduced, but artifacts occur due to parameter differences across slices
Solution Approach 1:
The patent merges multiple slice acquisitions into a single simultaneous excitation event using multi-band RF pulses. All slices are excited and scanned together in one shot with identical parameters, eliminating the parameter differences that cause artifacts in conventional sequential multi-slice HASTE sequences
Solution Approach 2:
The patent changes the RF excitation parameter by using multi-band RF pulses that can simultaneously address multiple slices with the same excitation parameters. This allows all slices to be scanned with identical TE, TR, and other sequence parameters, eliminating artifacts caused by parameter variations across slices
3Quantity of substance
If slice multiplexing is implemented, then slice coverage is enhanced, but complexity of data acquisition increases
Solution Approach 1:
The patent uses identical scan parameters and sequence settings for all simultaneously acquired slices. The same RF excitation pulses, gradient schemes, and echo train parameters are copied and applied to multiple slices, simplifying the acquisition process despite enhanced slice coverage
Solution Approach 2:
The patent implements a universal acquisition sequence that simultaneously handles multiple slices with a single set of parameters. The multi-band RF pulse sequence and gradient echo acquisition are designed to work universally across all slices, eliminating the need for slice-specific parameter adjustments and reducing overall system 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
This approach reduces breath-hold time, enhances slice coverage, and minimizes artifacts by ensuring consistent scanning conditions for both slice and reference data acquisition, improving the robustness and quality of MR imaging.
Implementation Method 1
Radio-frequency excitation pulses (RF pulses) are radiated into the examination object in order to trigger nuclear spin resonances
Implementation Method 2
the examination object is positioned in a magnetic resonance scanner in a strong, static, homogeneous, basic magnetic field, also called a B0 field, having field strengths of 0.2 tesla to 7 tesla and more for this purpose, so nuclear spins in the object are oriented along the basic magnetic field
Implementation Method 3
For spatial encoding of the scan data, rapidly switched magnetic gradient fields are overlaid on the basic magnetic field
Implementation Method 4
The triggered nuclear spin resonances are detected as echo signals, which are stored in a memory in a form known as k-space data
Data Source
AI summary
In a method and apparatus for creating magnetic resonance data of at least two simultaneously manipulated, non-overlapping slices of an examination object by a parallel acquisition technique, reference data are acquired such that, between acquisition of slice scan data of a slice scan data set in which the scan data of all simultaneously manipulated slices are incorporated in an overlaid manner, and its associated reference data, no slice scan data of a different slice scan data set are acquired. A high level of robustness with respect to movements of the examination object is thereby achieved.