MRI Slice-Multiplexing Phase Compensation for Ghosting Artifacts
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Solution Overview
Problem
Slice-multiplexing methods in magnetic resonance imaging (MRI) lead to ghosting artifacts due to varying effects of gradient blips on different tissue types, causing interference signals and reduced image quality.
Innovation Solution
A method that selects a compensation factor to correct interference signals by determining a compensation phase, which is applied during data recording or reconstruction to account for different spin types, thereby improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If slice-multiplexing methods are used to accelerate MR recordings, then productivity is improved, but interference signals and ghosting artifacts increase due to varying effects on different spin types
Solution Approach 1:
The patent applies parameter changes by introducing compensation phases that are specifically calculated to counteract the chemical shift-induced phase differences between water and fat spins. The compensation phase is determined as a function of the chemical shift and the gradient moment, effectively changing the phase parameter to eliminate interference signals while maintaining the accelerated slice-multiplexing recording capability
2Measurement precision
If gradient blips are applied to encode slice positions, then measurement precision is improved, but ghosting artifacts occur due to different phase shifts on water and fat spins
Solution Approach 1:
The patent introduces a compensation phase as an intermediary element that mediates between the gradient blip encoding and the chemical shift effects. This compensation phase acts as a corrective intermediary that preserves the slice position encoding precision while counteracting the harmful ghosting artifacts by equalizing the phase shifts between different spin types
3Loss of time
If simultaneous multi-slice recording is performed, then measurement time is reduced, but interference between different spin types increases
Solution Approach 1:
The patent changes the phase parameter dynamically based on the chemical shift and gradient moment to suppress interference signals during simultaneous multi-slice recording. By applying the compensation phase calculated from the chemical shift relationship, the method maintains reduced measurement time while eliminating the interference that would otherwise occur between different spin types
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
The method effectively reduces interference signals and enhances image quality by compensating for the phase shifts caused by different spin types, specifically water and fat tissues, resulting in clearer MRI images.
Implementation Method 1
Radio frequency excitation pulses (RF pulses) are irradiated into the examination object to trigger nuclear spin resonances that can be measured as signals
Implementation Method 2
For spatial encoding of the measured data, rapidly applied magnetic gradient fields, known as gradients for short, are superimposed on the main magnetic field
Implementation Method 3
the transverse magnetization being 'flipped' so to speak by irradiating at least one RF refocusing pulse after irradiation of the RF excitation pulse, as a result of which the de-phased magnetization is rephased again and therefore, after a time known as the echo time TE, what is known as a spin echo SE is generated
Implementation Method 4
Due to the difference in the resonance frequencies of spins present in different tissues, known as a chemical shift, in water and fat tissue for example, the spins in the different types of tissue are not excited in one and the same slice
Data Source
AI summary
The disclosure relates to techniques for acquiring measured data that has been recorded simultaneously via a magnetic resonance facility from at least two slices from an examination object comprising at least two different spin types. The techniques includes selecting a desired simultaneous recording of measured data from at least two slices in which during recording phases that generate field of view shifts have been imprinted, selecting a compensation factor to compensate for interference signals caused by the different spin types, determining a compensation phase for the phases to be imprinted in the desired recording as a function of the compensation factor, and carrying out the desired recording of measured data and/or reconstruction of image data from the measured data by applying the compensation phase that has been determined to the respective phases to be imprinted.