MRI Sensor Node Clock Recovery for Phase-Coherent Read-Out
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Solution Overview
Problem
Maintaining phase coherent signal acquisition becomes increasingly difficult with the increase in the number of coil elements in MR systems, and conventional clock recovery methods relying on crystal oscillators are costly and unreliable.
Innovation Solution
A magnetic resonance imaging system with a digital serial communication network using a ring topology and clock and data recovery units that recover the clock directly from the incoming data stream without local or external references, compensating for variations in clock phase due to operational conditions by detecting propagation delays and adjusting local clock phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of coil elements is increased to improve signal detection capability, then the sensitivity and coverage of the MR system is improved, but maintaining phase coherent signal acquisition becomes increasingly difficult
Solution Approach 1:
Each sensor node recovers its own clock signal from the incoming data stream without requiring external clock references. The CDR unit at each node autonomously generates the recovered clock signal by processing the incoming serialized data, enabling self-synchronization across the network
Solution Approach 2:
The same network link that transmits data also carries the clock information embedded within the data stream itself. The data transmission channel serves dual purposes: conveying sensor data and providing the timing reference for synchronization
2Reliability
If traditional CDR circuits with clock references are used to ensure phase coherence, then phase coherent signal acquisition is achieved, but the cost and device complexity increase
Solution Approach 1:
The clock reference function is extracted from separate external clock sources and integrated directly into the data transmission stream. The clock signal is embedded within the serialized data itself, eliminating the need for separate clock distribution infrastructure
Solution Approach 2:
The data and clock signals are merged into a single serialized bit stream. The clock information is encoded within the data transmission protocol, allowing both data and timing information to be conveyed over the same physical medium
3Reliability
If crystal oscillators are used as local clock references in sensor nodes, then stable clock signals are provided, but the cost and reliability in MR environment deteriorate
Solution Approach 1:
The system replaces expensive and MR-environment-sensitive crystal oscillators with simpler, more robust clock recovery circuitry that derives timing from the data stream itself, reducing both cost and susceptibility to MR environment interference
Solution Approach 2:
The mechanical resonator-based crystal oscillators are replaced with electronic clock recovery mechanisms that use digital signal processing to extract timing information from the serialized data stream, eliminating the need for physical resonators
Data Source
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AI summary
The invention relates to phase-coherent read-out of sensor nodes (3) of a magnetic resonance imaging system (1) with a digital serial communication network (2). According to the invention, the network (2) comprises multiple sensor nodes (3) for detecting a radio frequency signal from a patient who is under examination by the magnetic resonance imaging system (1), and a host node (4) which is connected to the sensor nodes (3) via a network link (5) for merging and processing digital sensor data received from the sensor nodes (3), wherein the host node (4) comprises a receiver (6) connected to the network link (5) for receiving data over the network link (5), and a transmitter (7) connected to the network link (5) for transmitting data over the network link (5), the sensor nodes (3) each comprise an analog-to-digital converter (8) for converting the detected radio frequency signal to the digital sensor data, a receiver (9) connected to the network link (5) for receiving data over the network link (5), a transmitter (10) connected to the network link (5) for transmitting data over the network link (5), and a clock and data recovery unit (11) with a clock device which is configured for running on a preset free-running frequency, the frequency of the data transmission over the network link (5) is set to a fixed frequency relative to the preset free-running frequency of the clock devices, and the clock and data recovery units (11) are configured for generating a recovered clock signal for controlling the analog-to-digital converter (8) of their sensor node by regulating the frequency of the clock device of their sensor node (3) to lock to the frequency of the data transmission over the network link (5). In this way, the possibility of phase coherent sensory data acquisition with a magnetic resonance imaging system (1) is provided in a robust and cost-efficient way.