Eccentric Mass Synchronization for Stable MRE Excitation
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Solution Overview
Problem
Existing magnetic resonance elastography (MRE) systems using gravitational transducers face challenges in achieving stability and synchronization of mechanical excitations with MRI systems, leading to unreliable measurement results due to non-linearities and parasitic harmonics.
Innovation Solution
A method is introduced to synchronize the rotational eccentric mass of a gravitational transducer with a magnetic resonance elastography scan by using a stepper motor to adjust the rotational speed based on reference positions, ensuring that the vibration frequency matches the acquisition frequency, thereby stabilizing the transducer and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a gravitational transducer with rotational eccentric mass is used for MRE excitation, then linearity and reduced parasitic harmonics are achieved, but stability and synchronization with MRI system deteriorate
Solution Approach 1:
The patent implements a feedback control system where the actual angular position of the rotational eccentric mass is continuously measured and compared with the reference position. The control unit adjusts the rotational speed based on the position deviation, ensuring stable synchronization with the MRI acquisition. This closed-loop feedback mechanism resolves the contradiction by maintaining both linearity and stability simultaneously.
Solution Approach 2:
The system pre-calculates and stores reference positions for the rotational eccentric mass at each acquisition time point before the actual MRE measurement. This preliminary establishment of reference positions allows the system to anticipate and correct deviations, ensuring stable synchronization without compromising the linearity of mechanical excitation during the actual measurement.
2Productivity
If rotational speed of eccentric mass is increased to match acquisition frequency, then synchronization improves, but measurement precision deteriorates due to speed instability
Solution Approach 1:
The patent employs dynamic speed adjustment where the rotational speed of the eccentric mass is continuously adapted based on real-time position feedback. Rather than maintaining a fixed high speed, the system dynamically adjusts the speed to match the acquisition frequency while maintaining precise angular positioning, thus achieving both synchronization and measurement precision.
Solution Approach 2:
The control unit modifies the rotational speed parameter in real-time based on the measured angular position and the required acquisition frequency. This parameter adjustment ensures that the system achieves the necessary synchronization speed while maintaining measurement precision through continuous optimization of the speed parameter.
3Measurement precision
If reference positions are calculated for each acquisition period, then synchronization accuracy improves, but system complexity increases
Solution Approach 1:
The patent creates a virtual reference position model that is copied and stored for each acquisition period based on the predetermined vibration frequency. Instead of complex real-time calculations, the system uses pre-calculated reference position copies that are retrieved and compared during acquisition, thereby achieving high synchronization accuracy while minimizing control system complexity.
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 enhances the linearity and stability of mechanical excitations, reducing parasitic harmonics and ensuring reliable and stable measurement results by synchronizing the gravitational transducer with the MRI system, thereby improving the accuracy of biomechanical parameter estimation in tissues like the liver.
Implementation Method 1
a rotational eccentric mass (2) which is driven by a shaft (3), wherein the rotation of the eccentric mass causes the gravitational transducer (1) to vibrate
Data Source
AI summary
The present disclosure is directed to techniques for synchronizing a rotational eccentric mass of a gravitational transducer used for a magnetic resonance elastography acquisition with a corresponding magnetic resonance elastography scan carried out by a magnetic resonance imaging system, wherein the rotation of the eccentric mass is driven by a shaft. The method includes starting the rotation of the eccentric mass at a set vibration frequency and the magnetic resonance elastography scan at a set acquisition frequency; determining the rotational position of the shaft; defining the rotational position as first reference position; calculating further reference positions. At the start time of each subsequent acquisition period, determining the current rotational position of the shaft; comparing the determined current rotational position with the theoretically expected reference position and decreasing or increasing the rotational speed of the rotational eccentric mass based on the comparison.