MRI Motion Detection Using CDMA Pilot Tone Encoding
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Solution Overview
Problem
Existing pilot tone methods for detecting patient motion during MRI scans are limited in accuracy and spatial resolution due to the long wavelength of the pilot tone signal.
Innovation Solution
The method employs a multiple access technique using a plurality of RF transmit antennas and a receiver with multiple RF receive antennas, allowing for the separation and analysis of unique pilot tone signals from different transmit antennas, thereby improving spatial resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single RF transmit antenna is used in pilot tone methods, then the system complexity is reduced, but the spatial resolution and measurement precision are limited due to the long wavelength of the pilot tone signal
Solution Approach 1:
The patent segments the single RF transmit antenna into multiple RF transmit antennas (Tx1, Tx2, Tx3, Tx4), each transmitting pilot tone signals with different encoding. This segmentation allows the system to achieve better spatial resolution by analyzing phase differences from multiple transmit sources, while the overall system complexity remains manageable through structured encoding schemes.
Solution Approach 2:
The patent introduces a new dimension by adding multiple transmit antennas with different spatial positions and encoding schemes. This transforms the system from a single-source to a multi-source configuration, enabling spatial resolution improvement through phase comparison across multiple transmission paths without proportionally increasing system complexity.
2Measurement precision
If multiple RF transmit antennas are used without multiple access encoding, then the spatial resolution may be improved, but the receiver cannot determine from which RF transmit antenna a certain signal is coming from, causing signal separation problems
Solution Approach 1:
The patent applies preliminary action by encoding each RF transmit antenna's pilot tone signal with a unique scheme before transmission. This pre-encoding allows the receiver to easily separate and identify signals from different transmit antennas through correlation or decoding, avoiding complex signal separation problems while maintaining signal processing manageability.
Solution Approach 2:
The patent introduces encoding schemes as an intermediary mechanism between the multiple RF transmit antennas and the receiver. This intermediary enables the receiver to distinguish signals from different transmit antennas without requiring complex signal processing, as the encoding acts as a unique identifier for each transmit source.
3Reliability
If pilot tone signals are transmitted continuously, then the motion detection coverage is improved, but the bandwidth consumption and interference with MR data acquisition increase
Solution Approach 1:
The patent implements periodic action by transmitting pilot tone signals in periodic bursts rather than continuously. Each burst contains encoded information from multiple transmit antennas, allowing the system to maintain reliable motion detection coverage while reducing overall bandwidth consumption and minimizing interference with MR data acquisition through controlled transmission timing.
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 enables the extraction of significantly more information from the pilot tone signal, resulting in a more accurate detection of motion with improved spatial resolution, allowing for better correction of artefacts in MRI images.
Implementation Method 1
The basic principle of RF based methods, also termed 'pilot tone' methods, is to irradiate the body with an RF signal just outside the receive bandwidth of the MR data being acquired
Data Source
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AI summary
The invention is directed for performing a magnetic resonance scan using a motion detection system (8, 18, 6, 16, 10), wherein the method comprises transmitting Tx pilot tone signals (42) via a plurality of RF transmit antennas, and receiving at least one Rx pilot tone signal via at least one RF receive antenna (16). The Tx pilot tone signals (42) are encoded using a multiple access method, in particular a code division multiple access (CDMA) method, and the receiver (6) decodes the received at least one Rx pilot tone signal into Rx pilot tone signals originating from the different RF transmit antennas (18). The invention is also directed to an MRI system and a motion detection system.