Looping-Star MRI Reconstruction for Overlapping Echo Artifacts
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Solution Overview
Problem
The looping star pulse sequence in MRI suffers from an overlapping echo effect due to simultaneous signals from multiple excitation pulses, leading to reduced image resolution or increased scan time in conventional gridding reconstruction methods.
Innovation Solution
A model-based reconstruction technique that models overlapping echoes using a system matrix, allowing for joint reconstruction of FID and GRE signals, and employs variable flip angles and shaped RF pulses to improve signal amplitude and uniformity, while maintaining resolution without increasing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional reconstruction methods are used for looping star pulse sequence, then image artifacts are reduced, but image resolution deteriorates or scan time increases
Solution Approach 1:
The patent applies parameter changes by modifying the reconstruction approach from conventional methods to model-based reconstruction. Specifically, it changes the mathematical model parameters to account for overlapping echoes by building separate echo-in and echo-out signal matrices and summing them to create a system matrix that accurately models the overlapping echo effects, thereby resolving artifacts while preserving image resolution
Solution Approach 2:
The patent segments the echo signals into two distinct components: echo-in signals and echo-out signals. By building separate signal matrices for each component and then summing them, the method systematically handles the overlapping echo problem without compromising image quality or requiring increased scan time
2Object-affected harmful factors
If conventional reconstruction methods are used for looping star pulse sequence, then artifacts are minimized, but scan time increases
Solution Approach 1:
The patent changes the reconstruction model parameters to efficiently handle overlapping echoes. By using model-based reconstruction with echo-in and echo-out signal matrices, the method achieves artifact reduction without the need to increase scan time, as the mathematical model efficiently processes the existing signal data
3Measurement precision
If model-based reconstruction with echo-in and echo-out matrices is used, then signal-to-noise ratio is enhanced, but computational complexity increases
Solution Approach 1:
The patent segments the complex reconstruction problem into manageable parts by creating separate echo-in and echo-out signal matrices. This segmentation allows for systematic processing of overlapping echoes while maintaining computational efficiency, as each matrix can be constructed and summed independently rather than requiring complex iterative optimization
Solution Approach 2:
The model-based reconstruction method uses the acquired signal data itself to build the system matrix through the echo-in and echo-out matrices, allowing the data to inform the reconstruction model without requiring additional calibration scans or external reference data, thereby enhancing SNR without proportionally increasing computational burden
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 proposed method reduces artifacts from overlapping echoes, enhances signal-to-noise ratio, and improves T2*-weighted image quality by jointly reconstructing proton density and relaxation maps, thereby increasing image resolution and SNR without extending scan time.
Implementation Method 1
loud acoustic noises are generated from Lorentz forces caused by rapidly changing currents in the magnetic field gradient coils
Implementation Method 2
applying a sequence of radio frequency (RF) pulses to the subject
Data Source
AI summary
The following relates generally to improved techniques for magnetic resonance imaging (MRI). In particular, the following relates to improving techniques of data acquisition and image reconstruction in relation to the “looping star” pulse sequence, which was developed to reduce acoustic noise. For example, techniques disclosed herein address the problem that looping star pulse sequence suffers from the overlapping echo effect. For instance, some implementations build echo-in and echo-out signal matrixes, and then sum the matrices to create a system matrix.