MRI Motion Tracking via FID Frequency Shift
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Solution Overview
Problem
Current methods for tracking respiratory motion in MRI imaging are cumbersome, require additional devices, increase setup time, and risk saturation due to longer repetition times and low resolution motion detection.
Innovation Solution
A motion tracking method that excites an imaging volume, shifts the frequency of the FID signal relative to the center frequency as the position changes, and calculates the frequency shift over time to obtain the motion trajectory, allowing for simplified process, reduced saturation risk, and shorter navigation sequence repetition times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external monitoring device is used to monitor respiratory motion, then motion tracking capability is improved, but device complexity and setup time increase
Solution Approach 1:
The imaging system itself performs motion tracking by utilizing the FID signal frequency shifts, eliminating the need for external monitoring devices. The system monitors its own state changes through the frequency variations of the FID signal, achieving self-diagnosis and self-monitoring functionality.
Solution Approach 2:
The FID signal acquisition serves dual purposes: both for obtaining imaging data and for monitoring respiratory motion through frequency shift analysis. This multi-functional approach allows the same hardware and signal processing pipeline to perform multiple tasks, reducing overall system complexity.
2Measurement precision
If a navigation sequence with longer TR is used for motion tracking, then motion detection capability is improved, but saturation risk increases
Solution Approach 1:
The method changes the approach from using TR duration as the basis for motion detection to using frequency shift magnitude as the detection parameter. By monitoring the frequency shifts of the FID signal relative to the center frequency, the system achieves sensitive motion detection without requiring extended TR periods, thereby avoiding saturation.
Solution Approach 2:
The patent replaces the traditional time-based motion detection mechanism (relying on longer TR for better resolution) with a frequency-based detection mechanism. This substitution allows motion detection to occur within the same TR framework, eliminating the trade-off between detection resolution and saturation risk.
3Measurement precision
If user selection of tracking position is required, then tracking accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The system automatically identifies and tracks the frequency shifts of the FID signal without requiring user intervention to select tracking positions. The automated frequency analysis performs the tracking function independently, simplifying the user interface and operational workflow while maintaining accurate motion detection.
4Measurement precision
If multiple echoes are acquired for motion tracking, then motion trajectory accuracy is improved, but productivity deteriorates
Solution Approach 1:
The FID signal acquisition serves dual purposes: both for obtaining imaging data and for monitoring respiratory motion through frequency shift analysis. This multi-functional approach allows the same hardware and signal processing pipeline to perform multiple tasks, reducing overall system complexity.
Solution Approach 2:
The method continuously monitors the frequency of the FID signal throughout the acquisition process, extracting motion information from each signal measurement. This continuous extraction of useful information from the primary imaging signal eliminates the need for separate dedicated motion tracking acquisitions, thereby maintaining productivity.
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 method simplifies the tracking process, reduces the risk of saturation, and enhances motion detection resolution without additional hardware, enabling efficient respiratory motion monitoring for improved MRI imaging.
Implementation Method 1
When magnetic resonance (MR) technology is utilized to image organs of a human body
Implementation Method 2
shifting a frequency of a free induction decay (FID) signal generated by the imaging volume relative to a center frequency
Data Source
AI summary
Embodiments of the present invention provide a motion tracking method for MR imaging, comprising: exciting an imaging volume of a detected object; shifting a frequency of an FID signal generated by the imaging volume relative to a center frequency as a position of the imaging volume changes; acquiring the FID signal and calculating a frequency shift of the acquired FID signal relative to the center frequency for multiple times; and obtaining a motion trajectory of the detected object in accordance with a change of the frequency shift as a function of time.