MRI Fat Suppression via In-Phase and Out-of-Phase Echoes
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques face challenges in obtaining high-quality water tissue images efficiently, particularly due to chemical shift artifacts caused by inhomogeneous static and radio-frequency fields, which require longer scan times and complex processes.
Innovation Solution
A method involving the application of a fat suppression pulse before the imaging sequence, followed by multiple echoes where data is collected both when water and fat are in phase and out of phase, allowing for the generation of fat-suppressed image data within a shorter scan time by using gradient read pulses with opposite directions to reduce chemical shift artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two repetition times are used to obtain water and out-of-phase images, then image quality is improved, but scan time increases
Solution Approach 1:
A fat suppression pulse is applied before the start of any repetition time to pre-suppress fat signals. This preliminary action allows the subsequent imaging sequence to directly capture water-dominated signals without requiring multiple repetition times for phase separation, thereby reducing scan time while maintaining image quality
Solution Approach 2:
The harmful fat signals are extracted and suppressed separately using a dedicated fat suppression pulse before the main imaging sequence. By removing the fat signal component in advance, the remaining water tissue images are obtained without chemical shift artifacts, achieving high image quality in a single repetition time
2Object-generated harmful factors
If traditional fat suppression methods are used, then fat artifacts are reduced, but image homogeneity deteriorates due to field inhomogeneity
Solution Approach 1:
The imaging sequence utilizes changes in echo time (TE) to exploit the phase difference between water and fat signals. By acquiring images at different echo times where water and fat are in-phase and out-of-phase, and combining them through image processing, the method achieves fat suppression while maintaining image homogeneity even in the presence of field inhomogeneity
Solution Approach 2:
The final water tissue image is constructed as a composite from multiple image data sets acquired at different echo times. By mathematically combining the in-phase and out-of-phase images, the method creates a composite image that eliminates fat signals while preserving water tissue homogeneity, overcoming the limitations of traditional single-pulse fat suppression methods
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 effectively suppresses fat signals and reduces chemical shift artifacts, resulting in higher quality images with reduced brightness differences and improved homogeneity, achieved without increasing scan time.
Implementation Method 1
Due to different precession frequencies of protons in water and fat in human tissue, chemical shift artifacts are produced during magnetic resonance imaging
Implementation Method 2
nuclear spin associated with hydrogen nuclei in human tissue is polarized, so that the tissue of the to-be-imaged part generates a longitudinal magnetization vector at a macroscopic level. After a radio-frequency field B1 intersecting the direction of the static magnetic field B0 is applied, the direction of rotation of protons changes so that the tissue of the to-be-imaged part generates a transverse magnetization vector
Implementation Method 3
After the radio-frequency field B1 is removed, the transverse magnetization vector decays in a spiral manner until it is restored to zero. A free induction decay signal is generated during decay
Data Source
AI summary
Embodiments of the present invention provide a magnetic resonance imaging system and a method for obtaining magnetic resonance imaging data. The method comprises: applying a fat suppression pulse before the start of any repetition time of an imaging sequence; performing a plurality of echoes in the repetition time, wherein first image data when water and fat are in phase and second image data when water and fat are out of phase are obtained during each echo of the plurality of echoes; and obtaining fat-suppressed image data according to the first image data and the second image data.