RF-Safe Transmission Path Using Mechanical Switching
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Solution Overview
Problem
Existing RF safe transmission paths for MR imaging systems face challenges such as inadequate impedance, battery life limitations, and complexity due to the use of diodes, which can lead to disturbances, destruction, and heating risks in strong RF fields, especially for invasive devices and catheters.
Innovation Solution
A transmission path using electrical contacts that can be opened or interrupted to low conductance and capacitance for RF safety, allowing for low or zero impedance connection, utilizing pressure switches or thermal switches to manage RF exposure and power transmission across a wide frequency range without transformers or frequency-dependent elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diodes are used to subdivide the conductor into sections, then RF safety is improved by preventing standing waves, but device complexity increases and battery life is limited due to power consumption requirements
Solution Approach 1:
The patent replaces electronic diode-based RF switching with a mechanical switch that opens electrical contacts to create gaps in the conductor. This mechanical approach eliminates the need for powered electronic components, reducing complexity and power consumption while maintaining RF safety through physical interruption of current paths.
Solution Approach 2:
The invention extracts and removes the powered electronic switching elements (diodes) from the system, replacing them with passive mechanical switches. This extraction eliminates the power consumption and complexity associated with active electronic components while achieving the same RF safety function through mechanical contact separation.
2Reliability
If diodes are used to control impedance, then RF safety is improved, but battery life is reduced due to continuous power consumption for impedance control
Solution Approach 1:
The patent employs passive mechanical switches that require no power source, effectively making them 'disposable' in the sense that they have no power consumption lifecycle. Unlike active diodes that require continuous power to maintain controlled impedance states, the mechanical switches provide permanent impedance control through their open/closed contact state, eliminating battery drain.
Solution Approach 2:
The mechanical switches operate autonomously without requiring external power or control signals. The RF safety function is achieved through the inherent mechanical operation of opening contacts, which automatically creates high impedance states during RF transmission without consuming battery power, allowing the system to serve itself without active power management.
3Temperature
If electrical contacts are opened to low conductance for RF safety, then RF heating is reduced, but signal transmission capability is affected
Solution Approach 1:
The patent implements periodic switching of electrical contacts, opening them during RF transmission periods to prevent heating and closing them during signal transmission periods to enable communication. This time-division approach allows the system to alternate between safety mode (contacts open) and operation mode (contacts closed), achieving both RF heating reduction and reliable signal transmission.
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
The solution provides superior MR compatibility, reliable signal transmission, and extended battery life by minimizing electrical power consumption, ensuring safety from RF-induced heating and disturbances across various conditions, including high power and low-frequency applications.
Implementation Method 1
The transmission path comprises a plurality of switching units, each comprising electrical contacts which serially connected into the line and which each separate the line electrically into line segments if the contacts are open
Implementation Method 2
utilizing pressure switches or thermal switches to manage RF exposure and power transmission
Implementation Method 3
utilizing pressure switches or thermal switches to manage RF exposure and power transmission
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A transmission path (2) comprising an electrically conductive link or connection lead or line or cable (21) is disclosed, which path is or can be made RF safe (especially with respect to heating due to standing waves) when guided through RF electrical and/or magnetic fields especially of a MR imaging system and which is especially suitable for connecting a base or connection unit (1), like for example a power supply or a control or evaluation unit (first unit), with a distal or remote electrical unit (3) like a sensor or a detector, a transmit and/or receive unit, or an accessory device like for example an RF body or surface coil system, or an invasive or interventional device like for example a catheter or implantables (second unit), especially in a magnetic resonance (MR) imaging system. The transmission path may comprise pressure switches or optical switches.