Implantable Sensor Impedance Adjustment for MRI Safety
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Solution Overview
Problem
Implantable medical devices, such as cardiac pacemakers and defibrillators, face heating issues during MRI scans due to induced electrical currents in electrode lines, leading to tissue heating and safety concerns, with existing solutions requiring special electrodes or interrupting therapy functions.
Innovation Solution
A temperature sensor integrated with an impedance detection device is connected to the electrode line, allowing for temperature measurement and impedance evaluation to minimize heating by adjusting the input impedance of the implant, enabling safe MRI examinations without special electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard electrode lines are used in implantable medical devices, then the device can perform therapy functions and sensing, but the electrode conductors heat up during MRI scans due to induced electrical currents
Solution Approach 1:
The patent changes the electrical parameters (impedance, resistance) of the electrode line to minimize induced currents during MRI. By adjusting these parameters, the electrode heating problem is reduced while maintaining standard electrode functionality for therapy and sensing.
Solution Approach 2:
The patent employs feedback mechanisms where the implantable device monitors conditions and adjusts its electrical parameters in response to detected signals, enabling dynamic control of electrode heating during MRI procedures.
2Temperature
If bandpass filters are added to the electrode to reduce MRI-induced heating, then temperature control is improved, but the electrode line is interrupted with resistors, inductive and capacitive components impairing therapy function
Solution Approach 1:
The patent extracts the filtering function from the electrode conductor itself and places it in the implantable pulse generator. This removes the need for complex electrode construction with multiple components, maintaining simple electrode design while achieving temperature control.
Solution Approach 2:
The patent makes the implantable pulse generator perform multiple functions: it serves as both the therapy delivery device and the filtering/temperature control mechanism. This eliminates the need for separate filter components in the electrode line.
3Temperature
If bandpass filters are added to the electrode, then MRI-induced heating is reduced, but the reliability of the electrode line is reduced by additional joints and potential failure points
Solution Approach 1:
The patent removes filter components from the electrode line and relocates them to the implantable pulse generator. This extraction eliminates additional joints and connection points in the electrode, thereby maintaining electrode line reliability while achieving temperature control.
4Measurement precision
If special electrodes with temperature sensors are used, then temperature monitoring is improved, but the implantation complexity and cost increase
Solution Approach 1:
The patent enables the existing electrode line to serve dual purposes: maintaining its primary therapy and sensing functions while also acting as a temperature sensor during MRI. This is achieved by monitoring impedance changes in the existing electrode conductors, eliminating the need for separate temperature sensing electrodes.
Solution Approach 2:
The patent makes the electrode line self-diagnostic by using its own electrical properties (impedance, resistance) to detect temperature changes. The electrode monitors its own thermal state through electrical parameter measurements, eliminating the need for external temperature sensing components.
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 MRI-induced electrode heating, allowing for safe use of implantable medical devices during MRI scans by minimizing temperature-related impedance changes, and can be implemented using standard electrodes, reducing costs and improving implant safety.
Implementation Method 1
the evaluation is carried out with regard to a temperature-dependent characteristic of the electrode pole impedance
Implementation Method 2
the changing magnetic fields in the electrical conductor that prevail in the magnetic resonance tomograph are not inconsiderable induce electrical currents
Implementation Method 3
Such induced currents can also be emitted to the surrounding tissue via the electrode poles of the electrode line and thus lead to undesired tissue heating
Data Source
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AI summary
The sensor has an impedance detection unit for detecting an electrode pole impedance within a predetermined frequency range and an event-dependent time window such that the detected electrode pole impedance is evaluated with respect to a temperature-dependent characteristic of the electrode pole impedance. The impedance detection unit is electrically connected with an electrode pole (20) e.g. tip electrode (22) and ring electrode (24). The time window is controlled by a MRI sensor using a signal feature or event repeating within successive cardiac cycles. Independent claims are also included for the following: (1) an implantable medical device (2) a method for adjusting input impedance of an implantable medical device for connection of an electrode lead.