Optical Encoder for MRI-Safe Surgical Position Detection
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Solution Overview
Problem
Conventional electronic measuring techniques for determining the depth of surgical instruments in neurosurgery are hindered by MRI-generated magnetic fields, which cause safety hazards, accuracy issues, and risk of burns due to eddy currents, preventing remote position detection.
Innovation Solution
An optical position detection system using an encoder with a translucent substrate and light blocking indicia, illuminated by a light source via optical fibers, allowing for remote determination of the instrument's position without entering the magnetic field, utilizing optical signals transmitted through optical fibers to avoid magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electronic measuring apparatus are used to detect instrument position, then position information can be obtained, but the magnetic field causes safety hazards, accuracy degradation, and risk of burns due to eddy currents
Solution Approach 1:
The patent replaces electronic measuring apparatus with an optical measurement system. An encoder with light-blocking indicia is attached to the instrument, and optical fibers transmit light through the encoder to a detector. This optical system is immune to magnetic field interference, eliminating safety hazards and accuracy degradation while enabling remote position detection.
Solution Approach 2:
The patent introduces optical fibers as an intermediary medium to transmit measurement information from the magnetic field environment to the detector outside the field. The optical fibers carry light signals through the encoder, allowing position detection without direct electrical contact or electronic components in the magnetic field, thus avoiding eddy currents and magnetic interference.
2Loss of information
If the surgeon enters the magnetic field to manually read instrument depth, then position information can be obtained, but safety hazards and exposure to magnetic field risks increase
Solution Approach 1:
The patent replaces manual reading with an automated optical measurement system. The encoder attached to the instrument automatically tracks position, and optical fibers transmit this data to a remote detector. The surgeon remains outside the magnetic field, eliminating exposure risks while continuously obtaining instrument depth information.
Solution Approach 2:
The measurement system is self-contained and automatically provides position information without requiring surgeon intervention in the magnetic field. The encoder moves with the instrument and continuously generates optical signals that are detected and processed, enabling autonomous position monitoring.
3Ease of operation
If optical encoding system is used for position detection, then remote measurement without magnetic field exposure is achieved, but device complexity increases
Solution Approach 1:
The patent extracts the measurement function from complex electronic apparatus and implements it using a simple optical encoder with light-blocking indicia. The encoder is a straightforward mechanical component that moves with the instrument, and optical fibers provide simple light transmission. This extraction reduces overall system complexity while enabling remote operation.
Solution Approach 2:
The patent uses an optical copy principle where the encoder creates a light pattern that represents the instrument position. The light-blocking indicia on the encoder modulate light to encode position information, which is then detected and decoded. This optical copying approach simplifies the measurement system compared to direct electronic sensing.
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
Enables accurate, safe, and remote monitoring of surgical instrument depth with sub-micrometer resolution, avoiding the drawbacks of MRI-generated magnetic fields and providing both absolute and relative position information to the surgeon outside the magnetic field.
Implementation Method 1
At least one input optical fiber extends from an input fiber first end to an input fiber second end, with the input fiber first end coupled to the light source and the input fiber second end disposed at a point adjacent the encoder first side
Implementation Method 2
The encoder includes a translucent substrate and one or more light blocking indicia disposed thereon
Implementation Method 3
At least one output optical fiber extends from an output fiber first end to an output fiber second end, with the output fiber first end disposed at a point adjacent the encoder second side and the output fiber second end coupled to the light detector array
Data Source
AI summary
Assemblies and methods for remotely detecting a position of a surgical instrument (102) in the presence of a magnetic field. An encoder (126) is coupled to move in concert with the instrument (102). A translucent substrate and light blocking indicia (406) are disposed on the encoder (126). A light source (128) and a light detector array (130) are effectively disposed outside of the magnetic field. Light from the light source (128) is carried to the encoder first side using an input optical fiber (120). Light passing through the encoder (126) is received at an encoder second side by an output optical fiber (122), and thus transmitted to the light detector array (130), which converts the received light to position representative electrical signals. Such signals are subsequently transmitted to a control module (134) that formulates and conveys a position of the instrument (102).