Chemical Shift Corrected Calibration Maps for Parallel MRI
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Solution Overview
Problem
Conventional fat suppression methods in MRI, such as STIR and spectral-spatial pulses, fail to provide reliable and uniform fat suppression in areas with magnetic field heterogeneities, leading to reduced signal-to-noise ratio and limited T1 weighted applications, especially in extremity and off-isocenter imaging.
Innovation Solution
A method involving the acquisition of multiple echoes at different echo times to create a chemical shift corrected calibration map, using IDEAL (Iterative Decomposition with Echo Asymmetry and Least Squares Estimation) to separate water and fat signals and correct for chemical shift artifacts, enabling improved sensitivity calibration and parallel imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fat suppression methods (STIR, spectral-spatial pulses) are used, then fat suppression is achieved, but signal-to-noise ratio is reduced and T1 weighted applications are limited
Solution Approach 1:
The patent segments the water and fat signals by acquiring multiple echoes at different echo times, allowing separate processing and combination of water and fat components. This segmentation enables reliable fat suppression while preserving the water signal quality, resolving the contradiction between fat suppression reliability and signal-to-noise ratio.
Solution Approach 2:
The patent adds the time dimension by acquiring multiple echoes at different echo times (TE). This temporal dimension allows the system to separate water and fat signals based on their different chemical shifts, achieving reliable fat suppression without degrading the signal-to-noise ratio of the water image.
2Productivity
If parallel imaging is used to increase scanning speed, then productivity is improved, but calibration map accuracy is degraded due to chemical shift artifacts
Solution Approach 1:
The patent performs preliminary water-fat separation and chemical shift correction on the calibration data before using it for parallel imaging reconstruction. By pre-processing the calibration maps to remove chemical shift artifacts, the system maintains high calibration accuracy while still benefiting from the speed improvements of parallel imaging.
Solution Approach 2:
The patent uses acquired echoes to generate calibration maps, which are then used to improve the accuracy of subsequent parallel imaging reconstructions. This feedback loop ensures that chemical shift artifacts are systematically corrected, maintaining calibration map accuracy while enabling fast parallel imaging.
3Measurement precision
If multiple echoes at different echo times are acquired to create chemical shift corrected calibration map, then calibration accuracy is improved, but scanning time is increased
Solution Approach 1:
The patent changes the echo time parameter across multiple acquisitions to exploit the different chemical shifts of water and fat. By strategically selecting echo times, the system achieves accurate water-fat separation and chemical shift correction. When combined with parallel imaging, this parameter variation achieves high calibration accuracy without excessive time penalty.
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 enhances the signal-to-noise ratio and allows for accurate fat suppression across various imaging applications, including T1 weighted imaging, by eliminating chemical shift artifacts and improving imaging efficiency at higher field strengths without increasing bandwidth.
Implementation Method 1
exploit the difference in chemical shifts between water and fat and in order to separate water and fat into separate images
Data Source
AI summary
A method for generating a calibrated parallel magnetic resonance image is provided in a manifestation of the invention. A magnetic resonance imaging excitation is applied. A plurality of echoes at different echo times (TE) is acquired. The acquired plurality of echoes from different echo times is used to create a chemical shift corrected calibration map.