High-Resistance Printed MR Temperature Probe
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Solution Overview
Problem
Current temperature monitoring devices for MR environments, such as fiber optic probes and standard thermistors, are expensive, mechanically delicate, and prone to errors due to magnetic fields, RF heating, and interference, posing burn hazards and providing inaccurate readings.
Innovation Solution
A temperature monitoring device using a printed conductor with a high resistance, non-ferromagnetic thermistor and conductive trace on a flexible substrate, integrated with a battery-powered control circuit and wireless communication, which includes a reference element to filter out RF-induced currents and prevent burn hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard thermistor with standard cable is used in MR environment, then temperature monitoring function is provided, but RF heating effects cause burn hazards and require expensive high-resistance cables
Solution Approach 1:
The patent changes the electrical resistance parameter of the cable from standard low resistance to high resistance (at least 100 ohms) to reduce RF current flow and eliminate burn hazards while maintaining temperature monitoring accuracy in the MR environment
Solution Approach 2:
The patent uses a disposable probe design with integrated high-resistance trace and thermistor that eliminates the need for expensive reusable high-resistance cables, reducing cost while maintaining safety and accuracy
2Object-affected harmful factors
If high-resistance cables are used to overcome RF heating, then burn hazard is reduced, but the cables are expensive, difficult to manufacture, and hyper sensitive to patient movement
Solution Approach 1:
The patent merges the high-resistance cable function directly into the probe by printing a high-resistance conductive trace on the probe substrate, eliminating the separate cable component and simplifying manufacturing while maintaining burn hazard reduction
Solution Approach 2:
The printed conductive trace acts as an intermediary that provides the necessary high resistance to block RF currents while being mechanically integrated into the probe structure, eliminating the need for separate sensitive cables
3Strength
If ferromagnetic content is used in temperature-monitoring device construction, then structural integrity is provided, but the cable may be drawn into the MRI scanner causing damage or acting as a projectile
Solution Approach 1:
The patent changes the magnetic properties of the probe materials by eliminating ferromagnetic content entirely and using non-ferromagnetic materials for all structural components, maintaining structural integrity while removing projectile hazards
Solution Approach 2:
The patent uses composite materials including non-ferromagnetic substrates, conductive inks, and encapsulation materials to construct the probe, achieving both structural integrity and MR safety without ferromagnetic components
4Reliability
If standard cable and thermistor are used, then temperature monitoring is provided, but MRI gradient interference induces currents producing false temperature readings
Solution Approach 1:
The printed conductive trace serves as an intermediary with high resistance that blocks gradient-induced currents from reaching the thermistor, eliminating interference waveforms and improving temperature measurement precision
Solution Approach 2:
The patent extracts and eliminates the standard low-resistance cable that allows gradient interference currents to flow, replacing it with an integrated high-resistance trace that blocks these interfering currents
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 effectively reduces patient burn risks, eliminates ferromagnetic content, and provides accurate temperature readings by inhibiting eddy currents and interference, enhancing patient safety and care in MR environments.
Implementation Method 1
a printed conductor 126 of high resistance... to inhibit the formation of eddy currents and reduce RF heating
Implementation Method 2
The radio frequency field produced by the MRI scanner may generate currents in a standard cable... The MRI gradient interference from the MR scanner can also induce currents
Implementation Method 3
a temperature sensor in the form of a non-ferromagnetic thermistor... the electrical resistance of the thermometer probe is measured
Data Source
Figure 1
Figure 2a~2c
Figure 2d
AI summary
A temperature measurement probe (130) for use in a magnetic resonance environment, includes an elongated substrate (202), at least one highly resistive, electrically conductive traces (200, 200a, 200b, 200a', 200b') one printed at least one thermistor (204) disposed on the substrate and electrically connected with the trace. The thermistor is configured to be placed in thermal communication with a patient in the magnetic resonance environment. In some embodiments, the printed trace may be carbon-based, silicone based, or may be a doped semiconductor material.