Surgical Instrument Shape Sensor with Fiber Bragg Gratings
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Solution Overview
Problem
Current methods for determining the pose and shape of minimally invasive surgical instruments in surgery lack precision, accuracy, and sensitivity, often providing relative rather than absolute three-dimensional measurements, which limits their effectiveness in medical procedures.
Innovation Solution
An apparatus comprising a reference fixture with a joint and joint tracker, a torsionally stiff tether, and a shape sensor that extends through the joint and tether into the surgical instrument, providing absolute three-dimensional pose and shape data in a fixed world reference frame, using a shape-sensing optic fiber with Fiber Bragg Gratings to mitigate twist-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical fiber shape sensors operate via backscatter methods (Rayleigh, Raman, Brillouin scattering), then shape sensing capability is achieved, but the measurements are sensitive to twist and environmental conditions, reducing measurement precision
Solution Approach 1:
The patent extracts and eliminates the harmful sensitivity to twist and environmental conditions from the measurement system. By using a twist-insensitive Fiber Bragg Grating configuration and differential measurement techniques, the system removes the adverse effects of twist on shape sensing accuracy, allowing precise shape measurement independent of rotational disturbances.
Solution Approach 2:
The patent changes the measurement parameter from conventional backscatter methods sensitive to twist to Fiber Bragg Grating reflectometry that is inherently twist-insensitive. This parameter change transforms the measurement approach to one that remains stable under environmental variations and twist conditions, improving measurement precision.
2Measurement precision
If conventional shape sensors are used, then shape information can be obtained, but the distances measured are relative distances rather than absolute distances, limiting the ability to determine absolute three-dimensional pose
Solution Approach 1:
The patent introduces a tether as an intermediary element that provides a known reference length between the shape sensor and the surgical instrument. This tether acts as a mediator that transforms relative shape measurements into absolute three-dimensional pose information by providing a fixed reference distance, enabling determination of absolute position and orientation.
Solution Approach 2:
The patent transitions from two-dimensional relative shape measurements to three-dimensional absolute pose measurements by incorporating the tether length as an additional dimensional reference. This dimensionality change enables the system to determine absolute position and orientation in 3D space rather than only relative shape changes.
3Adaptability or versatility
If a shape sensor is twisted during surgical instrument manipulation, then the sensor can follow the instrument's movement, but the pose information obtained becomes incorrect due to twist-induced errors
Solution Approach 1:
The patent converts the harmful effect of twist into a beneficial feature by using a twist-insensitive Fiber Bragg Grating configuration. The sensor can now freely follow the surgical instrument's movements including twists, and the twist-insensitive measurement principle converts what would be erroneous twist signals into accurate shape information, making the twist freedom a blessing rather than a curse.
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 precise and accurate absolute three-dimensional shape and pose data for surgical instruments, enhancing surgical procedures by allowing for the registration and superimposition of images, thereby improving the surgical process.
Implementation Method 1
using a shape-sensing optic fiber with Fiber Bragg Gratings to mitigate twist-induced errors
Data Source
AI summary
A system comprises a manually operated instrument, a reference fixture positioned in a fixed world reference frame, and a shape sensor coupled to the manually operated instrument. The shape sensor extends from the manually operated instrument to the reference fixture. The system further comprises a controller configured to receive, from the shape sensor, shape information for the manually operated instrument. The controller is further configured to determine a pose of the manually operated instrument in the fixed world reference frame based on the shape information for the manually operated instrument.