MRI-Compatible FBG Sensor for Decoupled Torque and Force Measurement
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Solution Overview
Problem
Current MRI-compatible force and torque sensors are bulky, sensitive to temperature, and interfere with MRI imaging, lacking a compact, decoupled solution for accurate needle insertion and steering in prostate interventions.
Innovation Solution
A compact, MRI-compatible sensor system using Fiber Bragg Grating (FBG) technology with decoupled torque and linear-force detection, employing optical fibers and flexural beams to provide independent measurements, made from MRI-compatible materials and designed for sterilization and temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional strain gauges are used for force sensing, then force measurement capability is achieved, but MRI image quality is drastically degraded due to magnetic field and RF pulse distortion
Solution Approach 1:
The patent replaces conventional electrical strain gauges with an optical sensing system using Fiber Bragg Gratings (FBGs) embedded in flexural beams. This substitution eliminates ferromagnetic and conductive materials that interfere with MRI, while maintaining force measurement capability through optical wavelength detection of beam deflection.
Solution Approach 2:
The patent introduces optical fibers with FBGs as an intermediary between the mechanical force application and the detection system. The FBGs convert mechanical strain into optical wavelength shifts, which can be detected without introducing magnetic interference, thus mediating between force sensing and MRI compatibility.
2Object-affected harmful factors
If optical sensors with photo sensors are used for force measurement, then MRI compatibility is achieved, but device size becomes bulky
Solution Approach 1:
The patent uses thin flexural beams made of MRI-compatible materials (such as phosphor bronze or titanium) with embedded FBGs. These thin-film structures provide the necessary mechanical compliance for force sensing while maintaining a compact form factor, eliminating the bulky photo sensor assemblies of previous designs.
Solution Approach 2:
The patent combines the force sensing function and the MRI-compatible structural element into a single integrated component. The flexural beams serve both as mechanical elements for force transmission and as substrates for FBG embedding, eliminating the need for separate bulky optical sensor housings.
3Volume of moving object
If single-DOF optical torque sensor is used, then compactness is achieved, but measurement capability is insufficient for needle steering requiring both torque and force measurement
Solution Approach 1:
The patent segments the sensing function into two independent detection assemblies: a torque detector assembly with FBGs on flexural beams for rotational measurement, and a linear-force detector assembly with FBGs on different flexural beams for axial force measurement. This segmentation allows both 2-DOF measurement capabilities within a compact integrated structure.
Solution Approach 2:
The patent creates a multi-functional sensor that simultaneously measures both torque (for needle steering control) and axial force (for insertion force feedback) using a single integrated optical sensing platform. The shared optical fiber and FBG technology provide universal measurement capability for both rotational and linear forces.
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 offers a compact, sensitive, and noise-free 2-DOF sensor for axial torque and force measurement, facilitating precise needle steering with minimal interference, allowing for real-time feedback and simplified calibration, while maintaining MRI image quality.
Implementation Method 1
A compact, MRI-compatible sensor system using Fiber Bragg Grating (FBG) technology with decoupled torque and linear-force detection
Data Source
AI summary
A magnetic resonance imaging (MRI) compatible sensor for measuring torque with respect to an axis of rotation in conjunction with an applied linear force includes a shaft arranged in a longitudinal direction substantially along the axis of rotation, a base component arranged along the axis of rotation and displaced with respect to the shaft, a torque detector assembly configured to be coupled to rotational motion of the shaft about the axis of rotation relative to the base component, and a linear-force detector assembly configured to be coupled to linear motion of the shaft from a force applied in a direction substantially coincident with the axis of rotation relative to the base component. The torque detector assembly and the linear-force detector assembly are substantially de-coupled from each other such that torque measurements are substantially independent of linear force measurements. The MRI compatible sensor consists essentially of MRI compatible materials.