Shape Memory Alloy Biopsy Needle with Optical Fiber Steering
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Solution Overview
Problem
Existing biopsy needles face challenges in accuracy due to needle deflection during insertion, particularly in MR-compatible environments, and existing actuation technologies are not optimized for steering the needle tip during insertion, leading to issues with MR compatibility and mechanical interactions.
Innovation Solution
A steerable biopsy needle design featuring a removable stylet with an outer stylet part and an inner stylet part, utilizing shape memory alloy (SMA) for bi-directional bending and rotation, coupled with optical fibers for actuation and sensing, allowing precise guidance to biopsy sites while being MR-compatible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rigid needle body is used for biopsy, then the needle structure is simple and easy to manufacture, but the needle deflection during insertion reduces accuracy
Solution Approach 1:
The needle is divided into a rigid proximal section and a flexible distal section with slots. The rigid section maintains structural integrity and ease of manufacture, while the flexible section with slots enables controlled deflection for accurate trajectory following, resolving the contradiction between manufacturing simplicity and trajectory accuracy.
Solution Approach 2:
The needle transitions from a static rigid structure to a dynamic structure where the distal section can deflect actively. The slots in the flexible section allow controlled bending in response to tissue forces, enabling the needle to adapt its trajectory dynamically while maintaining overall structural simplicity.
2Ease of operation
If magnetic actuation is used for needle steering, then the needle can be steered actively, but the needle becomes incompatible with MR imaging
Solution Approach 1:
The patent replaces magnetic actuation with a mechanically actuated flexible section. The flexible distal section with slots is actuated by forces applied at the needle base or through tissue interaction, eliminating the need for magnetic materials that would interfere with MR imaging while maintaining active steerability.
Solution Approach 2:
The needle uses changes in mechanical parameters (flexibility, slot geometry) rather than magnetic properties to achieve steerability. The flexible section's mechanical response to applied forces enables active steering without introducing magnetic materials that would compromise MR compatibility.
3Manufacturing precision
If a thin needle tip is used for precise biopsy, then the needle can access small tumors, but the tip becomes susceptible to buckling
Solution Approach 1:
The needle is segmented into a rigid proximal section that provides buckling resistance and a flexible distal section with the actual thin tip for precise access. The rigid section's structural integrity prevents buckling during insertion, while the flexible tip maintains the ability to reach small tumors with high precision.
Solution Approach 2:
The distal section uses a flexible structure with slots that allows the thin tip to maintain its shape and resist buckling through controlled flexibility. The slot geometry and material properties are designed to prevent buckling while preserving the thin profile needed for accessing small tumors.
4Power
If pneumatic or hydraulic actuation is integrated in a small diameter needle, then powerful actuation is achieved, but the device complexity increases and patient safety risks arise
Solution Approach 1:
The complex pneumatic or hydraulic actuation systems are extracted from the needle structure. Instead, the patent uses a simplified mechanical actuation approach where forces are applied externally at the needle base or through tissue interaction, achieving sufficient actuation power without the complexity and safety risks of integrated fluid systems in a 1-2 mm diameter needle.
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 design enables precise steering and sensing of the needle trajectory, enhancing accuracy and compatibility with MR imaging, suitable for small tumors and other biopsy sites, using a compact 1.65 mm diameter needle.
Implementation Method 1
an SMA material secured to the first SMA attachment extent and second SMA attachment extent, thereby spanning the deflection extent
Implementation Method 2
when the SMA is thermally activated, the needle deflects in a direction which reduces the gaps of the slots
Implementation Method 3
the inner stylet having longitudinal actuation fibers for coupling photonic energy to the SMA
Implementation Method 4
the actuation optical fiber coupling optical energy to the SMA
Implementation Method 5
the inner stylet also having a temperature sensor and a deflection sensor
Data Source
AI summary
A biopsy needle has a cylindrical shell outer cannula and a stylet consisting of an inner stylet and outer stylet, both of which are inserted into the cylindrical cannula. The outer stylet has a series of strain relieved slits which provide bending over a deflection region in one direction, and the outer stylet is formed from a material such as a shape memory alloy (SMA) having a superelastic phase. The deflection is generated by an SMA wire spanning a deflection extent and attached to the outer stylet on either side of the deflection extent. The inner stylet, when positioned inside the outer stylet, has one or more actuation fibers which couple optical energy into the SMA wire or hollow SMA tube, causing a deflection of the outer stylet over the deflection extent, with the optical energy provided to the actuation fibers for control of the deflection. Additional fibers may be placed in the inner stylet to measure temperature and to measure deflection.