MRI Motion Signal Sign Correction via Coil Correlation
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Solution Overview
Problem
Current methods for characterizing motion in magnetic resonance imaging (MRI) using pilot tone navigation struggle to reliably determine the sign of motion signals without additional information sources, leading to potential misinterpretation of normal physiological variations or pathological changes.
Innovation Solution
The method correlates motion signals with individual receiver coil signals and uses a reference correlation coefficient to correct the sign, based on the location-specific correlation between the motion signal and receiver coil signals, eliminating the need for additional information sources like electrocardiograms or respiration belts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional information sources like electrocardiograms or respiration belts are used to determine motion signal signs, then the reliability of motion characterization is improved, but the device complexity and cost increase
Solution Approach 1:
The system uses the MR scanner's own receiver coil signals to determine motion signal signs, eliminating the need for external sensors. The pilot tone signals generated during MR imaging are reused for motion characterization, allowing the system to serve itself rather than requiring additional information sources.
Solution Approach 2:
The receiver coil signals serve dual purposes: both for MR image acquisition and for motion signal sign determination. The same hardware components are used for multiple functions, making the system more versatile and eliminating the need for dedicated motion sensing equipment.
2Measurement precision
If blind source separation algorithms are used to separate different motions from receiver coil signals, then the measurement precision of motion components is improved, but the reliability of motion signal signs deteriorates due to indeterminate signs
Solution Approach 1:
The system applies feedback by comparing the signs of correlation coefficients between motion signals and pilot tone signals. When a mismatch is detected, the motion signal is corrected by sign inversion, ensuring reliable motion characterization without compromising separation precision.
Solution Approach 2:
Pilot tone signals serve as an intermediary reference to resolve the sign ambiguity problem. These known reference signals mediate between the separated motion components and their correct physical interpretation, allowing accurate sign determination without sacrificing separation precision.
3Ease of operation
If reference patterns based on empirical knowledge are used to determine motion signal signs, then the ease of operation is improved, but the reliability deteriorates in irregular or pathologic cases
Solution Approach 1:
The system dynamically adjusts to actual signal characteristics by computing correlation coefficients from measured data rather than relying on fixed reference patterns. This allows the system to adapt to varying physiological conditions and pathologic cases while maintaining ease of operation through automated processing.
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 allows for accurate determination of motion signal signs, reducing the impact of inaccuracies and enabling reliable motion characterization in MRI, particularly during data acquisition scheduling, without relying on external information sources.
Implementation Method 1
an electromagnetic reference signal is emitted by a reference signal generator into a target region in which an object to be examined is at least partially located, two or more receiver coil signals are generated in response to the emitted reference signal by two or more receiver coils located in the target region
Implementation Method 2
the object to be imaged affects an electromagnetic field due to its electric conductivity and electric permittivity. Since motion of the object alters the spatial distribution of conductivity and permittivity, a response to an electromagnetic reference signal, also denoted as pilot tone, measured by receiver coils shows temporal modulations due to the motion
Implementation Method 3
A first motion signal characterizing a first motion of the object is determined by a computing unit depending on temporal modulations of the two or more receiver coil signals... The computed first correlation coefficient is compared to a first reference correlation coefficient...
Data Source
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AI summary
According to a method for characterizing a motion of an object (3), a reference signal is emitted into a target region (6) and two or more receiver coil signals are generated in response to the reference signal by two or more receiver coils (4a, 4b, 4c). A motion signal characterizing a motion of the object (3) is determined by a computing unit (7) depending on temporal modulations of the two or more receiver coil signals. A correlation coefficient of the motion signal and a receiver coil signal is computed by the computing unit (7). A reference correlation coefficient is determined by the computing unit (7) depending on a location of the receiver coil based on a predetermined reference correlation map (11). The motion signal is corrected by the computing unit (7) depending on a correlation coefficient and the reference correlation coefficient.