Radial MRI Trajectory Angular Increment for Eddy Current Reduction
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Solution Overview
Problem
Conventional MRI techniques using radial k-space trajectories with the golden angle suffer from image artifacts due to eddy currents, especially when the number of radial profiles is variable, limiting their application in dynamic imaging and T1/T2 contrast applications like temporomandibular joint imaging.
Innovation Solution
A method employing a radial k-space trajectory with a constant angular increment in the range of 5 to 55 degrees, calculated using a specific formula, to minimize eddy current-induced artifacts and maintain scanning efficiency, allowing for dynamic imaging with variable profile numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the golden angle (111.246°) is used for radial k-space trajectory, then a nearly uniform distribution of profiles can be achieved for any number of profiles, but large eddy currents are induced in the main magnet leading to strong image artifacts
Solution Approach 1:
The patent applies parameter changes by modifying the angular increment from the golden angle (111.246°) to a reduced value (5° to 55°). This parameter change maintains the uniform distribution property while reducing the magnitude of gradient switching, thereby minimizing eddy current induction and the resulting image artifacts.
Solution Approach 2:
The patent introduces dynamic adaptability by allowing the number of radial profiles to be variable during acquisition rather than fixed. The reduced angular increment enables the system to dynamically adjust to different numbers of profiles while maintaining uniform sampling distribution, which is particularly useful for dynamic imaging applications where the number of usable profiles may vary.
2Adaptability or versatility
If the number of radial profiles is made variable for dynamic imaging, then adaptability to different motion levels is improved, but image artifacts increase due to eddy currents from abrupt gradient changes
Solution Approach 1:
The patent changes the angular increment parameter to a reduced value that is compatible with variable profile numbers. This parameter modification allows the system to adapt dynamically to different acquisition conditions while maintaining uniform sampling and minimizing eddy current effects, thus resolving the contradiction between adaptability and artifact reduction.
3Productivity
If a constant angular increment is used for radial trajectories, then scanning efficiency is maintained, but image artifacts occur due to eddy currents from constant gradient changes
Solution Approach 1:
The patent optimizes the angular increment parameter to a reduced constant value (5° to 55°) that balances two competing requirements: maintaining regular sampling intervals for efficient scanning while reducing the abruptness of gradient transitions to minimize eddy current induction. This parameter optimization resolves the contradiction between scanning efficiency and artifact reduction.
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 image artifacts and maintains high scanning efficiency, enabling high-quality dynamic MRI with improved T1/T2 contrast, suitable for applications like the temporomandibular joint imaging without the limitations of the golden angle's abrupt gradient changes.
Implementation Method 1
This gradient scheme, in turn, induces large, abruptly changing eddy currents in the conductive parts of the main magnet, thereby leading to constantly changing inhomogeneities in the main magnetic field.
Data Source
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AI summary
The invention relates to method for generating an MRI image in which a radial or spiral k-chamber path with a constant angular increment Psi is used to take an MRI image, said angular increment Psi being in the angular range of between 5 - 55 degrees or being in the corresponding supplementary angle Psi' and is selected according to the formula PsiN,M = pi / (N+1/ (M + tau - 1)). Alternatively, for an angular increment Psi which deviates from the angle increment of the optimal distribution of n radial profiles Psiopt = 180°/n, the minimum scanning efficiency of the angular increment Psi for n > 21 profiles is greater than 0.95, the angular increment Psi is in an angular range of 5 to less than 68,7537°, in particular between 5 - 55 degrees or in the corresponding supplementary angle Psi'.