Pilot Tone Signal for MR Cardiac Synchronization
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Solution Overview
Problem
Magnetic Resonance (MR) imaging is hindered by the need for cardiac synchronization, which is challenging due to artifacts induced by ECG leads in strong magnetic fields and the variability of heart motion with respiratory states, making existing ECG-based methods unreliable, especially at higher field strengths and in arrhythmic patients.
Innovation Solution
The method employs the Pilot Tone signal for cardiac synchronization, using existing MR hardware and processing facilities, with multiple receiving channels to detect cardiac and respiratory motion, allowing synchronization at arbitrary cardiac phases without the need for ECG leads, and utilizes adaptive or model-based filters to automatically assign physiological phases for reliable triggering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ECG leads are used for cardiac synchronization, then cardiac motion can be detected and synchronization achieved, but artifacts are induced in the strong magnetic field that degrade signal quality
Solution Approach 1:
The patent extracts the cardiac motion detection function from ECG leads and transfers it to the MR receiver coil system. The Pilot Tone signal is processed through the existing MR hardware to detect cardiac and respiratory motion, eliminating the need for separate ECG leads and their associated artifacts in the magnetic field.
Solution Approach 2:
The patent introduces the Pilot Tone signal as an intermediary that mediates between the need for cardiac synchronization and the MR imaging process. This signal is modulated by cardiac and respiratory motion and can be detected through the MR receiver coils, serving as a bridge without requiring external ECG leads.
2Reliability
If multiple ECG electrodes are applied to increase detection reliability, then ECG signal reliability improves, but the preparation time and complexity increase
Solution Approach 1:
The patent makes the MR receiver coil system multi-functional by enabling it to detect both MR signals and Pilot Tone signals modulated by cardiac and respiratory motion. This eliminates the need for separate ECG electrodes and their preparation, as the existing MR hardware performs dual functions.
Solution Approach 2:
The MR system serves itself by using its own receiver coils to detect cardiac and respiratory motion through the Pilot Tone signal. This self-service capability eliminates the need for external ECG monitoring equipment and the time-consuming preparation of skin and electrode placement.
3Reliability
If ECG leads are used at higher magnetic field strengths, then cardiac synchronization is achieved, but the hydro-magneto-dynamic effect increases and degrades signal quality
Solution Approach 1:
The patent extracts the motion detection function from the ECG leads and implements it within the MR system itself using the Pilot Tone signal. This eliminates the source of hydro-magneto-dynamic artifacts (the ECG leads and blood flow in the leads) while preserving the ability to detect cardiac motion at any magnetic field strength.
4Adaptability or versatility
If the heart moves with respiratory motion, then the ECG time course varies with respiratory state, but this reduces ECG reliability during deep breathing
Solution Approach 1:
The patent dynamically tracks both cardiac and respiratory motion through the Pilot Tone signal. By continuously monitoring the modulation of this signal, the system adapts to changing respiratory states and heart positions, maintaining reliable motion detection even during deep breathing or variable respiratory patterns.
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 provides robust, cost-effective cardiac synchronization that is reliable across varying patient conditions and magnetic field strengths, reducing preparation time and improving image quality by eliminating ECG-related artifacts and accommodating arrhythmic hearts.
Implementation Method 1
measure the variation induced by physiological motion by a coherent and/or continuous external frequency signal received by the local coil elements
Implementation Method 2
utilizes adaptive or model-based filters to automatically assign physiological phases for reliable triggering
Data Source
AI summary
A method is provided for generating a medical data set of a moving part of the human or animal body undergoing a cyclical movement such as cardiac movement. A raw data signal acquired by a magnetic resonance receiver coil arrangement is received. A magnetic resonance signal and a movement signal are separated from the raw data signal. At least two physiological phases of the moving body part are automatically assigned to the movement signal. The automatic assignment does not introduce a delay between the movement signal and the magnetic resonance signal. Time points used for triggering an acquisition of the magnetic resonance signal and/or for data post-processing of the magnetic resonance signal are determined or set.