Magnetic Resonance Mapping Correction Using Dixon B0 Field Maps
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Solution Overview
Problem
Inhomogeneities in the B0 field of magnetic resonance imaging systems lead to artifacts in reconstructed magnetic resonance mappings, which existing methods struggle to effectively correct.
Innovation Solution
Capture magnetic resonance signals at different phases of nuclear spin excitations of fat and water, determine a B0 field map, and use this map to correct the magnetic resonance mappings using a Dixon sequence and geometric distortion correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to correct B0 field inhomogeneities, then correction accuracy may be maintained, but acquisition time increases significantly
Solution Approach 1:
The patent applies preliminary action by capturing first and second magnetic resonance signals at specific time points (in-phase and opposed-phase) before the actual imaging sequence. These preliminary signals are used to determine the B0 field map in advance, which is then applied to correct the main imaging data. This preliminary determination of field inhomogeneities allows for efficient correction without extending the main acquisition time.
Solution Approach 2:
The patent utilizes periodic action by exploiting the periodic phase relationship between fat and water signals. By capturing signals at specific echo times where fat and water are in-phase and opposed-phase, the method periodically samples the field inhomogeneity information. This periodic sampling enables accurate B0 field mapping while maintaining efficient acquisition timing.
2Reliability
If B0 field map determination is performed using traditional sequences, then field inhomogeneity correction is achieved, but the process becomes time-consuming
Solution Approach 1:
The patent merges the B0 field map determination process with the fat-water separation process. By simultaneously determining both the B0 field map and the fat/water images from the same in-phase and opposed-phase signals, the method achieves reliable field correction without requiring separate dedicated sequences. This merging of functions maintains correction reliability while improving acquisition efficiency.
3Measurement precision
If multiple separate sequences are used for field mapping and imaging, then comprehensive correction is possible, but device complexity and scan time increase
Solution Approach 1:
The patent applies universality by designing a multi-functional sequence that simultaneously performs field mapping, fat-water separation, and imaging. The same in-phase and opposed-phase signal acquisitions used for Dixon fat-water imaging are also utilized to determine the B0 field map. This universal approach eliminates the need for separate dedicated field mapping sequences, reducing overall system complexity while maintaining comprehensive correction capabilities.
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 provides a time-efficient and accurate correction of magnetic resonance mappings by reducing B0 field inhomogeneity effects, improving image quality and enabling faster data acquisition.
Implementation Method 1
The first magnetic resonance signals are provoked by nuclear spin excitations of fat and water in an examination object. The second magnetic resonance signals are provoked by nuclear spin excitations of fat and water in the examination object.
Implementation Method 2
The resonant frequencies differ by approximately 3.4 ppm. When using spin-echo and/or gradient-echo sequences, for example, this results in modulation of the signal intensity as a function of the echo time TE.
Implementation Method 3
gradient pulses for the purpose of generating a magnetic field gradient are directed into an examination region in which an examination object is situated. This triggers spatially encoded echo signals, often referred to as magnetic resonance signals, in the examination object.
Implementation Method 4
radio frequency (RF) pulses for the purpose of generating an RF field (e.g., a B1 field) are directed into an examination region in which an examination object is situated. This triggers spatially encoded echo signals, often referred to as magnetic resonance signals, in the examination object.
Data Source
AI summary
According to a method, first magnetic resonance signals are captured at a first time point. Second magnetic resonance signals are captured at a second time point. The first magnetic resonance signals are provoked by nuclear spin excitations of fat and water in an examination object. The second magnetic resonance signals are provoked by nuclear spin excitations of fat and water in the examination object. The nuclear spin excitations of fat and water are in phase at the first time point. The nuclear spin excitations of fat and water are in opposed phase at the second time point. A B0 field map is determined based on the first magnetic resonance signals and the second magnetic resonance signals. Further magnetic resonance signals are captured. At least one magnetic resonance mapping is determined by reconstructing the further magnetic resonance signals. The at least one magnetic resonance mapping is corrected based on the B0 field map.