Multiband RF Excitation for MR Slice Multiplexing
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Solution Overview
Problem
Existing magnetic resonance (MR) slice multiplexing methods require additional reference measurements, increasing acquisition time and Specific Absorption Rate (SAR) exposure, while deviating measurement parameters can lead to artifacts in image data separation.
Innovation Solution
The method involves using a multiband RF excitation pulse to selectively excite non-overlapping slices, assigning additional phases to displace k-space points, and repeating data acquisition to completely sample the central k-space region, eliminating the need for additional calibration measurements and ensuring matched calibration and image data parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional reference measurements are performed for slice multiplexing calibration, then image data separation quality is improved, but acquisition time and SAR exposure increase
Solution Approach 1:
The patent combines the reference measurement calibration process with the actual image acquisition process by using the same multiband RF excitation pulses and measurement sequences. Instead of performing separate reference scans, the calibration data is extracted from the same data set used for image reconstruction, thereby merging two previously separate operations into one unified process that reduces total acquisition time without compromising separation quality
Solution Approach 2:
The measurement sequence is designed to serve dual purposes: it simultaneously acquires both calibration/reference data and image data using the same multiband RF excitation and k-space sampling trajectory. This multi-functional approach eliminates the need for dedicated calibration scans, reducing SAR exposure and acquisition time while maintaining the quality of slice separation
2Measurement precision
If additional reference measurements are performed for slice multiplexing calibration, then image data separation quality is improved, but SAR exposure increases
Solution Approach 1:
The patent combines the reference measurement calibration process with the actual image acquisition process by using the same multiband RF excitation pulses and measurement sequences. Instead of performing separate reference scans, the calibration data is extracted from the same data set used for image reconstruction, thereby merging two previously separate operations into one unified process that reduces total acquisition time without compromising separation quality
Solution Approach 2:
The measurement sequence is designed to serve dual purposes: it simultaneously acquires both calibration/reference data and image data using the same multiband RF excitation and k-space sampling trajectory. This multi-functional approach eliminates the need for dedicated calibration scans, reducing SAR exposure and acquisition time while maintaining the quality of slice separation
3Ease of manufacture
If measurement parameters differ between reference and image acquisition, then calibration can be performed, but artifacts appear in separated image data
Solution Approach 1:
The patent enforces homogeneous measurement conditions by using identical multiband RF excitation pulses, gradient sequences, and k-space sampling parameters for both calibration and image acquisition. The same measurement sequence is executed multiple times with consistent parameters, ensuring that the calibration data and image data are acquired under matching conditions, thereby eliminating artifacts caused by parameter mismatches while maintaining calibration effectiveness
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 acquisition time and SAR exposure by determining calibration data from the same measurement data used for image reconstruction, preventing artifacts and maintaining image quality without additional calibration measurements.
Implementation Method 1
Magnetic resonance (MR) technology is a known modality, used to generate images of the interior of an examination object. To trigger nuclear magnetic resonance, radio-frequency excitation pulses (RF pulses) are radiated into the examination object so as to trigger magnetic resonance signals
Implementation Method 2
To spatially encode the measurement data, the constant magnetic field is overlaid with rapidly switched magnetic gradient fields
Data Source
AI summary
In a magnetic resonance slice multiplexing method and apparatus, measurements are performed repeatedly subject to the assignment of additional phases to the respective slices, the additionally assigned phases being changed with reach repetition such that at least one central k-space region is sampled completely in each of the repeated acquisitions. A calibration dataset is determined from the measurement data acquired completely in the central k-space region. The calibration dataset is used when reconstructing image data for the simultaneously excited slices from the acquired measurement data.