Multi-Dimensional Pilot Tone Signal for MRI Triggering
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Solution Overview
Problem
Current Pilot Tone methods for cardiac motion detection in MRI scans face challenges with trigger stability and limited trigger time points due to the cardiac signal's small modulation and lack of clear R-wave, particularly affecting MR acquisitions with magnetization preparation.
Innovation Solution
A method that extends the cardiac Pilot Tone signal from one-dimensional to multi-dimensional by using blind source separation algorithms to extract at least two non-parallel weighting vectors, allowing for improved trigger stability and detection of additional cardiac components, enabling earlier and more precise trigger points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If the Pilot Tone method is used for cardiac triggering during MRI acquisition, then motion detection capability is improved, but trigger stability deteriorates due to small cardiac signal modulation and interference from RF pulses
Solution Approach 1:
The patent extends the cardiac Pilot Tone signal from one-dimensional to multi-dimensional by extracting at least two non-parallel weighting vectors using blind source separation algorithms. This dimensional expansion allows the system to capture multiple cardiac components simultaneously, providing more information for reliable trigger detection while maintaining sensitivity to small cardiac motions.
Solution Approach 2:
The patent separates the cardiac signal into multiple independent components through blind source separation, extracting distinct weighting vectors that represent different cardiac motion patterns. This segmentation allows the system to identify multiple trigger points within the cardiac cycle, including earlier points before the R-wave, thereby improving trigger stability and enabling more precise control of image acquisition timing.
2Difficulty of detecting and measuring
If current Pilot Tone methods are used, then cardiac motion detection is possible, but available trigger time points are limited due to lack of clear R-wave and small signal modulation
Solution Approach 1:
By transitioning from one-dimensional to multi-dimensional signal representation through blind source separation, the patent enables detection of multiple cardiac components with distinct temporal characteristics. This provides versatile trigger time point options across different phases of the cardiac cycle, including early diastolic points that were previously undetectable.
Solution Approach 2:
The patent performs preliminary extraction of multiple weighting vectors and identification of multiple trigger points before the actual image acquisition sequence. This preliminary action allows the system to pre-determine optimal trigger time points, including points before the R-wave, ensuring that magnetization preparation can be properly timed and played out before contraction begins.
3Reliability
If trigger time points are delayed to 200 ms after R-wave for stability, then trigger reliability is improved, but timing precision for magnetization preparation deteriorates
Solution Approach 1:
The patent identifies and stores multiple trigger time points in advance, including early diastolic points occurring before the R-wave. This preliminary identification allows the system to select the most appropriate trigger point for each specific acquisition sequence, ensuring that magnetization preparation has sufficient time to play out before contraction begins, while maintaining trigger reliability through multi-point validation.
Solution Approach 2:
The patent implements dynamic selection of trigger time points based on the specific requirements of different MRI sequences. Rather than using a fixed delayed trigger point, the system can adaptively choose from multiple available trigger points, selecting earlier points when timing precision is critical for magnetization preparation and relying on the multi-dimensional signal structure to maintain reliability.
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
Enhances trigger stability and allows for multiple trigger points within the cardiac cycle, particularly before the R-wave, improving image acquisition in MRI scans by reducing noise interference and enhancing the robustness of dark blood imaging.
Implementation Method 1
The transmitted Pilot Tone signal interacts with the human body and is received via multiple antennas (e.g., the local RF coil(s))
Data Source
AI summary
A method for acquiring image data from a part of a human body subjected to a cardiac movement is provided. The method includes transmitting a radiofrequency Tx Pilot Tone signal, receiving a pilot tone signal including a number of channel signals, and carrying out a blind source separation algorithm on a training portion of the pilot tone signal and thereby determining weighting vectors. The method also includes selecting and storing at least two non-parallel weighting vectors that allow to extract signal components from the number of channel signals. The extracted signal components represent cardiac movement. The method includes applying the weighting vectors to the further portions of the pilot tone signal to obtain a multi-dimensional pilot tone signal representing the cardiac movement, and using the multi-dimensional pilot tone signal for triggering the acquisition of the image data.