Position Dependent Interference Cancellation in Medical Probes
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Solution Overview
Problem
Existing medical position tracking systems face interference issues due to the pickup of external magnetic fields at the connector of invasive probes, leading to distorted position measurements, especially in the vicinity of the connector where continuous shielding is difficult to achieve.
Innovation Solution
Incorporating an auxiliary position transducer adjacent to the connector, which measures and calibrates interference signals, allowing the processor to cancel out interference and accurately determine the position of the distal end of the probe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If continuous shielding is implemented around the connector, then interference pickup is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The probe is divided into two functional parts: a disposable distal part containing the main position transducer and a reusable proximal part containing the connector and auxiliary transducer. This segmentation allows the auxiliary transducer to be positioned at the connector without requiring continuous shielding throughout the entire probe structure, reducing manufacturing complexity while maintaining interference rejection capability
Solution Approach 2:
An auxiliary position transducer is introduced as an intermediary element at the connector location. This auxiliary transducer specifically measures the interference signals at the vulnerable connector point, allowing the system to cancel interference without requiring physical shielding structures around the connector
2Measurement precision
If an auxiliary position transducer is added at the connector, then interference measurement capability is improved, but device complexity increases
Solution Approach 1:
The auxiliary position transducer serves multiple functions: it measures interference signals at the connector, provides position information for the proximal part of the probe, and enables calibration of the interference cancellation algorithm. This multi-functionality justifies the addition of the extra transducer by providing multiple benefits from a single component
Solution Approach 2:
The system changes from measuring only position parameters to measuring both position and interference signal parameters. The auxiliary transducer enables the system to capture interference signal characteristics (amplitude, phase, frequency) as additional measurable parameters, which are then used to cancel interference from the main transducer signals
3Measurement precision
If calibration data collection is performed at multiple positions, then interference cancellation accuracy is improved, but measurement time increases
Solution Approach 1:
The interference cancellation characteristics are determined in advance during a calibration phase before actual position measurements begin. The system collects calibration data at multiple positions beforehand and stores the interference cancellation characteristics, so that during normal operation only simple look-up and application of pre-computed cancellation parameters is needed, minimizing real-time measurement time
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 method enables precise location tracking of the distal end of the probe even in the presence of strong interference, improving measurement accuracy and relaxing shielding requirements for the probe's wiring.
Implementation Method 1
measuring a second position of an auxiliary position transducer at the proximal end of the probe
Implementation Method 2
magnetic field sensors within the distal end of a probe generate electrical signals in response to these magnetic fields
Data Source
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AI summary
A method for position tracking includes receiving signals from a main position transducer at a distal end of a medical probe via wiring traversing the probe to a connector at a proximal end of the probe, for connection to a processor, which processes the signals to find a first position of the distal end. Calibration data with respect to an interference introduced into the signals at the connector is collected as a function of a position of the proximal end. A second position of an auxiliary position transducer at the proximal end of the probe is measured. The interference in the signals is canceled responsively to the measured second position and the calibration data. The first position is calculated based on the signals, after canceling the interference.