Parallel Imaging Weighting Matrix via Spin-Echo Reference Data
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MR systems with cylindrical geometry face issues of magnetic field inhomogeneity and gradient linearity, leading to artifacts in parallel imaging due to incorrect position encoding and faulty calibration data sets, especially at the edges of the field of view, which are exacerbated by segmented recording and physiological effects.
Innovation Solution
A method for generating MR image data using a spin-echo based reference data set recorded without segmentation and with lower resolution in the readout direction, allowing for the calculation of a weighting matrix to determine missing raw data points, thereby reducing artifacts and improving calibration for parallel imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If segmented recording is used to obtain calibration data, then recording time is reduced, but physiological effects cause inconsistencies and artifacts in the calibration data set
Solution Approach 1:
The patent applies preliminary action by recording the calibration data set in a temporally separated manner before the actual imaging data acquisition. This ensures that the calibration data is obtained under stable conditions without physiological interference, and the weighting matrix is calculated in advance, eliminating artifacts caused by segmented recording during imaging.
2Productivity
If parallel imaging is used to reduce measurement time, then productivity increases, but artifacts occur due to faulty calibration data and high signal intensity regions
Solution Approach 1:
The weighting matrix is calculated in advance from a separately recorded calibration data set, ensuring accurate coil sensitivity information is available before parallel imaging begins. This preliminary calculation of reconstruction parameters enables artifact-free parallel imaging with high acceleration factors.
Solution Approach 2:
The patent introduces an intermediary calibration data set recorded under optimized conditions (lower resolution, spin-echo sequence) that serves as a mediator between the magnetic field inhomogeneities and the final imaging data. This intermediary data enables accurate weighting matrix calculation without directly compromising the quality of the main imaging data.
3Measurement precision
If reference data is recorded with high resolution, then calibration accuracy improves, but recording time increases significantly
Solution Approach 1:
The patent changes the resolution parameter when recording the calibration data set, using lower resolution in the readout direction compared to the final imaging. This parameter change reduces the calibration recording time significantly while the weighting matrix calculation still provides sufficient accuracy for parallel imaging reconstruction.
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 artifacts in MR images by providing a more accurate calibration data set, allowing for better handling of high signal intensity regions and reducing recording time, while maintaining image quality and reducing radiation exposure.
Implementation Method 1
Magnetic resonance apparatus and method for parallel imaging with a reference data set for determining the weighting matrix
Data Source
AI summary
In a magnetic resonance apparatus and a method for generating MR image data of a subject with parallel imaging, a reference data set of the object is recorded, in which at least one partial section of the associated raw data space is completely filled with raw data according to the Nyquist condition, and an imaging data set is recorded for the generation of the MR image data on the basis of spin-echo-based signals, in which the associated raw data space is not completely recorded according to the Nyquist condition. A weighting matrix is calculated based on the reference data set, which is used to determine raw data points of the imaging data set not recorded during parallel imaging. The unrecorded raw data points of the imaging data set are calculated using the calculated weighting matrix. The reference data set is recorded with a spin-echo-based reference imaging sequence without segmentation within an imaging slice and without temporal overlap with the recording of the imaging data set, and a resolution is used in the readout direction which is lower by at least a factor of 4 than when the imaging data set is recorded.