Gradient Echo MRI Iterative Reconstruction for Off-Resonance Signal Voids
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gradient echo magnetic resonance imaging is affected by inhomogeneities in the B0 field, leading to signal voids due to off-resonance effects.
Innovation Solution
The method involves upsampling an initial magnetization image and an off-resonance phase map, modulating the upsampled image with the phase map, and using an iterative scheme with data consistency and demodulation to calculate an updated image, thereby reducing signal voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gradient echo magnetic resonance imaging is performed rapidly, then imaging speed is improved, but signal voids due to off-resonance effects increase
Solution Approach 1:
The patent measures the off-resonance phase map and uses it to demodulate the k-space data, converting the harmful phase modulation into useful correction information. By applying the complex conjugate of the phase map to the k-space data, the method transforms the detrimental off-resonance effects into correctable phase variations, ultimately eliminating signal voids while maintaining rapid imaging speed.
Solution Approach 2:
The patent employs an iterative reconstruction process where the off-resonance phase map is measured, used to demodulate the data, and the result is refined through multiple iterations. This feedback loop continuously improves the image quality by reducing signal voids while maintaining the rapid imaging capability of gradient echo sequences.
2Device complexity
If standard reconstruction is used, then processing simplicity is maintained, but image quality deteriorates due to signal voids
Solution Approach 1:
The patent performs preliminary measurement of the off-resonance phase map before the main imaging sequence and uses this pre-acquired information to demodulate the k-space data. This preliminary action allows the main reconstruction to proceed with improved accuracy without requiring complex real-time processing during the imaging sequence itself.
Solution Approach 2:
The off-resonance phase map serves as an intermediary that mediates between the raw k-space data and the final image. By introducing this intermediate correction step that uses the phase map to demodulate the data, the patent improves image quality without fundamentally changing the overall reconstruction workflow.
3Object-affected harmful factors
If off-resonance phase map is applied for demodulation, then signal voids are reduced, but computational complexity increases
Solution Approach 1:
The patent extracts the off-resonance phase information from the k-space data into a separate phase map, then uses this extracted information to demodulate the data. By separating the phase correction step from the main reconstruction process, the method reduces computational complexity while effectively reducing signal voids.
Solution Approach 2:
The patent applies demodulation using the off-resonance phase map to the specific portions of k-space data affected by off-resonance effects, rather than performing full complex reconstruction. This partial action approach reduces computational complexity while still achieving the goal of reducing signal voids in the final image.
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 reduces the impact of phase modulation within voxels, improving image quality by minimizing signal voids and enhancing the quantitative accuracy of R2* maps.
Implementation Method 1
Gradient echo magnetic resonance imaging is a commonly used method commonly used for rapidly acquiring magnetic resonance imaging data
Implementation Method 2
In magnetic resonance imaging data is acquired in k-space and then later reconstructed using Fourier transforms into image space
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed herein is a medical system (100, 300). The execution of machine executable instructions (120) causes a processor (104) to: receive (200) measured gradient echo k-space data (122); receive (202) an off-resonance phase map (124); reconstruct (204) an initial image (126) from the measured gradient echo k-space data; calculate (206) an upsampled phase map (128) from the off-resonance phase map; calculate (208) an upsampled image (130) from the initial image; calculating (210) a modulated image (132) by modulating the upsampled image with the upsampled phase map; calculate (212) a corrected image (134) comprising iteratively. The iterative calculation comprises: calculating (214) updated k-space data by applying a data consistency algorithm (138) to a k-space representation of the modulated image and the measured gradient echo k-space data and calculating (216) an updated image (142) from the updated k-space data. Calculation of the updated image comprises demodulation by the upsampled phase map and applying a smoothing algorithm.