Adaptive MR K-Space Sampling for Motion Artifact Reduction
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Solution Overview
Problem
Current MR imaging techniques using radial or spiral acquisition schemes face challenges with motion artifacts, leading to potential clustering and gaps in angular sampling, which can reduce image quality.
Innovation Solution
An adaptive k-space sampling method that detects momentary motion-induced displacements and attributes them to specific motion states, allowing for individual incrementation of angular coordinates for each state to ensure improved distribution and sampling of k-space profiles, potentially using a golden angle scheme for uniform coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radial or spiral acquisition schemes are used in MR imaging, then imaging speed and coverage are improved, but motion artifacts increase and angular sampling distribution deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of angular coordinates based on detected object motion. The system continuously monitors motion and adapts the sampling trajectory in real-time, changing the angular positions of k-space profiles according to the current motion state. This dynamic adaptation prevents clustering and gaps in angular sampling that would occur with fixed trajectories during motion, thereby maintaining uniform distribution while preserving the speed advantages of radial/spiral acquisition.
Solution Approach 2:
The system incorporates a feedback mechanism where motion of the object is detected and used to control subsequent sampling parameters. The detected motion information feeds back into the selection of angular coordinates for the next k-space profile acquisition. This closed-loop control ensures that the sampling pattern automatically compensates for motion, maintaining uniform angular distribution without sacrificing imaging speed.
2Device complexity
If standard radial k-space sampling is used, then acquisition is simplified, but motion robustness deteriorates due to clustering and gaps in angular sampling
Solution Approach 1:
The patent transforms the static radial sampling pattern into a dynamic one that adapts to motion conditions. While the basic radial acquisition framework remains simple, the angular coordinates are dynamically adjusted based on detected motion. This maintains the simplicity of the overall acquisition scheme while significantly improving motion robustness through adaptive sampling distribution.
Solution Approach 2:
The system changes the angular coordinate parameter dynamically based on motion detection. Instead of using fixed angular intervals, the patent adjusts the angular positions of k-space profiles according to the current motion state. This parameter change ensures uniform angular sampling distribution during motion while keeping the acquisition method relatively simple and maintaining compatibility with standard radial sampling frameworks.
3Ease of operation
If angular coordinates are fixed during acquisition, then sampling procedure is simplified, but image quality deteriorates under motion conditions
Solution Approach 1:
The patent implements dynamic adjustment of angular coordinates based on detected object motion. The system continuously monitors motion and adapts the sampling trajectory in real-time, changing the angular positions of k-space profiles according to the current motion state. This dynamic adaptation prevents clustering and gaps in angular sampling that would occur with fixed trajectories during motion, thereby maintaining uniform distribution while preserving the speed advantages of radial/spiral acquisition.
Solution Approach 2:
The system changes the angular coordinate parameter dynamically based on motion detection. Instead of using fixed angular intervals, the patent adjusts the angular positions of k-space profiles according to the current motion state. This parameter change ensures uniform angular sampling distribution during motion while keeping the acquisition method relatively simple and maintaining compatibility with standard radial sampling frameworks.
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 quality of reconstructed MR images by ensuring quasi-uniform k-space coverage and efficient sampling, even in the presence of extreme motion states, and can be combined with existing techniques like PROPELLER or SENSE for improved image fidelity.
Implementation Method 1
Image-forming MR methods which utilize the interaction between magnetic fields and nuclear spins
Implementation Method 2
The signal data obtained via the receiving coils corresponds to the spatial frequency domain and is called k-space data
Implementation Method 3
constant magnetic field gradients extending along the three main axes are superposed on the uniform magnetic field, leading to a linear spatial dependency of the spin resonance frequency
Implementation Method 4
The variation of the magnetization can be detected by means of receiving RF coils which are arranged and oriented within an examination volume of the MR device
Data Source
AI summary
The invention relates to a method of MR imaging of an object (10) placed in an examination volume of a MR device (1). It is an object of the invention to enable MR imaging using a radial (or spiral) acquisition scheme with a reduced level of motion artefacts. The method of the invention comprises the following sequence of steps: —detecting a momentary motion—induced displacement (Δ) of the object (10); —attributing the detected displacement (A) to a motion state (M1-M5), each motion state (M1-M5) corresponding to one of a plurality of contiguous ranges of displacements (Δ); —determining angular coordinates of a radial or spiral k-space profile by incrementing the angular coordinates individually for each motion state (M1-M5) starting from initial angular coordinates; —acquiring the k-space profile; —repeating steps a-d a number of times; and —reconstructing an MR image from at least the k-space profiles attributed to one of the motion states (M1-M5). Moreover, the invention relates to a MR device (1) for carrying out this method as well as to a computer program to be run on a MR device (1).