Self-Calibrating Parallel Multiecho MRI for Fat Suppression
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Solution Overview
Problem
Conventional fat suppression methods in MRI, such as STIR and spectral-spatial pulses, are inadequate in areas with magnetic field heterogeneities, leading to reduced signal-to-noise ratio and limited T1-weighted imaging applications, while existing parallel MRI techniques face calibration challenges, especially in abdominal imaging.
Innovation Solution
A self-calibrating parallel multiecho MRI method is developed, which involves acquiring echoes at different echo times and sampling patterns to generate images, using a controller with computer-readable media to apply magnetic resonance imaging excitations and process echoes for phase demodulation, thereby overcoming sensitivity calibration issues and achieving robust fat suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fat suppression methods (STIR, spectral-spatial pulses) are used in areas with magnetic field heterogeneities, then uniform fat suppression is achieved, but signal-to-noise ratio is reduced and T1-weighted imaging capability is limited
Solution Approach 1:
The patent changes the timing parameters by acquiring multiple echoes at different echo times (TE1, TE2, TE3) rather than using a single inversion time or spectral selection. This temporal sampling approach allows mathematical separation of water and fat signals while maintaining signal integrity and enabling T1-weighted imaging with uniform fat suppression in field-inhomogeneous regions
Solution Approach 2:
The patent performs preliminary calibration by acquiring echoes at different sampling patterns to determine coil sensitivity profiles and field map information before the actual imaging sequence. This preliminary characterization of the magnetic field environment enables subsequent images to achieve uniform fat suppression without sacrificing signal-to-noise ratio
2Productivity
If parallel MRI techniques are used to increase imaging speed, then productivity is improved, but calibration challenges arise especially in abdominal imaging
Solution Approach 1:
The patent merges the calibration process with the imaging acquisition by using the same coil array and sampling patterns for both purposes. The calibration data (coil sensitivities and field maps) are extracted from the imaging echoes themselves, eliminating the need for separate calibration scans and reducing overall system complexity despite using parallel imaging
Solution Approach 2:
The imaging sequence itself provides the calibration information needed for parallel imaging reconstruction. By acquiring multiple echoes at different sampling patterns, the system self-calibrates through the imaging data, making the calibration process automatic and integrated rather than requiring external calibration procedures
3Measurement precision
If multiple echoes are acquired at different echo times and sampling patterns, then accurate water-fat separation and fat suppression are achieved, but scan time increases
Solution Approach 1:
The patent segments the k-space sampling across multiple echoes at different sampling patterns rather than acquiring all data at a single sampling pattern. This segmentation allows parallel imaging reconstruction to accelerate the scan while the multi-echo multi-pattern approach maintains water-fat separation accuracy through temporal and spatial sampling diversity
Solution Approach 2:
The patent adds temporal dimension by acquiring echoes at different echo times (TE1, TE2, TE3) in addition to using different sampling patterns. This transforms the problem from a 2D spatial sampling issue to a 3D problem involving time, frequency, and spatial dimensions, enabling accurate water-fat separation while allowing parallel imaging to reduce the temporal dimension's contribution to scan time
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 scan time and enhances image quality by combining reduced sampling and parallel imaging, providing accurate fat suppression and water-fat separation with improved signal-to-noise ratio across various imaging applications, including challenging areas like the abdomen.
Implementation Method 1
A magnetic resonance imaging excitation is applied. A first echo at a first echo time is acquired
Implementation Method 2
A first echo at a first echo time in a first sampling pattern is acquired. An additional echo(s) at an additional echo time(s) different from the first echo
Implementation Method 3
acquiring a first echo at a first echo time in a first sampling pattern, acquiring a second echo at a second echo time different from the first echo in a second sampling pattern different from the first sampling pattern
Implementation Method 4
using the acquired first echo, the acquired second echo, and the acquired third echo to provide a phase demodulation
Implementation Method 5
Glover et al. further refined this approach, described in Glover G., 'Multipoint Dixon Technique for Water and Fat Proton and Susceptibility Imaging'
Data Source
AI summary
A method for generating a self-calibrating parallel multiecho magnetic resonance image is provided. A magnetic resonance imaging excitation is applied. A first echo at a first echo time in a first pattern is acquired. A second echo at a second echo time different from the first echo phase in a second pattern different from the first pattern is acquired. The acquired first echo and acquired second echo are used to generate an image in an image pattern, wherein none of the acquired echoes for generating the image have the same pattern as the image pattern.