Electromagnetic Sensor Array Calibration for Surgical Navigation Error Mapping
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Solution Overview
Problem
Electromagnetic tracking systems in clinical environments are sensitive to electromagnetic field distortions caused by ferromagnetic interventional apparatus and metallic medical equipment, leading to non-uniform and complex error distributions that compromise the accuracy and precision of surgical tool navigation.
Innovation Solution
A calibration tool with an electromagnetic sensor array of two or more sensors in a known geometrical configuration is used to map absolute and relative errors pre-procedurally, employing statistical methods to generate an error map that provides real-time feedback on measurement confidence and reliability, distinct from other calibration methods that rely on optical markers or other sensing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electromagnetic tracking systems are used in clinical environments, then real-time navigation of surgical tools is enabled, but electromagnetic field distortions from ferromagnetic apparatus and metallic equipment cause non-uniform error distributions that compromise accuracy and precision
Solution Approach 1:
The system performs pre-procedural calibration by moving the electromagnetic sensor array through numerous measurement positions in the specific clinical environment before the actual procedure. This preliminary mapping of absolute and relative errors creates an error map that compensates for environmental distortions during real-time navigation, resolving the contradiction between enabling real-time tracking and maintaining accuracy despite field distortions
Solution Approach 2:
The system continuously measures relative errors between electromagnetic sensor pairs during pre-procedural calibration and uses statistical mapping to generate an error map. This feedback mechanism allows the system to identify and compensate for non-uniform error distributions caused by ferromagnetic apparatus and metallic equipment, maintaining tracking precision while enabling real-time navigation
2Measurement precision
If pre-procedural calibration techniques are used to characterize and correct electromagnetic tracking errors, then error correction is achieved, but clinical environments dynamically change during procedures making pre-procedural calibration measurements difficult to apply intra-procedurally
Solution Approach 1:
The system transitions from static pre-procedural calibration to dynamic intra-procedural error characterization. By continuously measuring relative errors between electromagnetic sensor pairs during the actual procedure and updating the error map in real-time, the system adapts to dynamic environmental changes while maintaining error correction capability
Solution Approach 2:
The electromagnetic sensor array serves dual purposes: it performs both the navigation function and the self-calibration function. The same sensors used for tracking surgical tools also measure relative errors for error map generation, eliminating the need for separate calibration systems and enabling continuous adaptation to environmental changes during the procedure
3Measurement precision
If optical markers or other sensing techniques are used for calibration, then reference measurements are obtained, but the system complexity increases and the solution becomes less distinct from other calibration methods
Solution Approach 1:
The system extracts and eliminates the dependency on external optical markers or separate reference sensing techniques. By using only the electromagnetic sensor array to measure relative errors between sensor pairs, the system obtains reference measurements needed for calibration while reducing overall system complexity and maintaining distinctiveness from other calibration methods
Solution Approach 2:
The electromagnetic sensor array performs multiple functions: it serves as both the navigation sensor and the calibration reference. The same sensors used for tracking surgical tools also provide the reference measurements for error characterization by measuring relative errors between sensor pairs, eliminating the need for separate calibration hardware and reducing system complexity
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 approach allows for accurate characterization and visualization of electromagnetic tracking errors, enhancing the physician's ability to target treatment locations with confidence by providing clear visual feedback on reliable and unreliable zones within the electromagnetic field, thereby improving navigation accuracy.
Implementation Method 1
an electromagnetic sensor array of two or more electromagnetic sensors (e.g., coils) disposed within a calibration electromagnetic field, and a calibrated distance between one or more electromagnetic sensors pairs is measured from a sensing of the electromagnetic sensor array within the calibration electromagnetic field
Data Source
AI summary
A calibration/surgical tool includes an electromagnetic sensor array of two or more electromagnetic sensors in a known geometrical configuration. Electromagnetic tracking errors are characterized by a mapping of pre-operative absolute and relative errors based on a movement of a calibrated calibration/surgical tool through a pre-operative electromagnetic field. Using statistical mapping, a desired absolute error field is measured either in the clinic as the part of daily quality control checks, or before the patient comes in or in vivo. A resulting error field may be displayed to the physician to provide clear visual feedback about measurement confidence or reliability of localization estimates of the absolute errors in electromagnetic tracking.