MRI-Compatible Flexible Endoscope Using Triple Helical Low-Susceptibility Tubes
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Solution Overview
Problem
Existing flexible endoscopes are unsuitable for use with MRI apparatuses due to their metallic parts affecting magnetic fields, which compromises their strength and flexibility, making them inadequate for both observation and operation inside a living body.
Innovation Solution
A flexible endoscope design featuring an inner tube made of resin, triple helical tubes made of low magnetic susceptibility materials like phosphor bronze or copper-silver alloy, and a bending operation wire with a braided string and adhesive, allowing for flexibility and strength while minimizing magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low magnetic susceptibility metals such as brass are used for metallic parts of an endoscope, then the endoscope becomes suitable for use in the vicinity of a MRI apparatus, but the strengths of the endoscope (tensile strength, compressive strength, and torsional strength) are reduced, making the endoscope unsuitable for operation inside a living body
Solution Approach 1:
The invention uses composite materials consisting of multiple layers: an inner tube made of resin (polypropylene or polyethylene), triple helical tubes made of low magnetic susceptibility metal (phosphor bronze or copper-silver alloy), and an outer tube made of resin. This composite structure combines the magnetic compatibility of low-susceptibility metals with the strength and flexibility of resin materials, resolving the contradiction between MRI compatibility and mechanical strength.
Solution Approach 2:
The invention employs flexible resin tubes (inner tube and outer tube made of polypropylene or polyethylene) that provide both strength and flexibility. These flexible shells replace rigid metallic structures, allowing the endoscope to bend freely while maintaining structural integrity and cross-sectional shape, thus achieving both flexibility for navigation and strength for operation.
2Strength
If a rigid endoscope is used, then it can be made out of materials that satisfy strength requirements and do not affect magnetic fields, but flexibility is lost, making it difficult to navigate inside a living body
Solution Approach 1:
The invention uses flexible resin tubes (inner tube and outer tube made of polypropylene or polyethylene) that inherently provide both strength and flexibility. The flexible shells allow the endoscope to bend freely to navigate complex anatomical paths while the triple helical reinforcement maintains cross-sectional shape, achieving both flexibility for navigation and structural integrity.
Solution Approach 2:
The composite structure combines flexible resin materials with low-susceptibility metal helical bands. The resin provides baseline flexibility and strength, while the triple helical tubes add torsional reinforcement without compromising flexibility, enabling the endoscope to maintain its shape when curved to maximum degree while remaining freely bendable.
3Volume of moving object
If the endoscope diameter is reduced to minimize patient burden, then patient comfort is improved, but the structural strength and flexibility may be compromised
Solution Approach 1:
The flexible resin tubes allow for a compact, small-diameter design that minimizes patient burden. The resin material's inherent flexibility enables the tube to bend without requiring excessive wall thickness, maintaining strength while reducing overall diameter for patient comfort.
Solution Approach 2:
The triple helical reinforcement structure provides high strength-to-weight ratio and high strength-to-diameter ratio. By strategically placing the helical bands around the inner tube, the design achieves maximum structural efficiency with minimal material, allowing small diameter while maintaining sufficient strength and flexibility for operation.
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 endoscope maintains required strength and flexibility, allowing for safe use within an MRI environment with reduced diameter, enabling both observation and operation without deforming the cross-sectional shape, thus addressing the need for a flexible and MRI-compatible endoscope.
Implementation Method 1
the triple helical tubes include a first helical band made of a low magnetic susceptibility material and helically wound around an outer periphery of the inner tube, a second helical band made of a low magnetic susceptibility material and helically wound around an outer periphery of the first helical band in a direction opposite to the winding direction of the first helical band, and a third helical band made of a low magnetic susceptibility material and helically wound around an outer periphery of the second helical band in a direction opposite to the winding direction of the second helical band
Data Source
AI summary
The flexible endoscope 20 has a flexible insertion portion 22 to be inserted in an observation zone 11 of a MRI apparatus 10. The insertion portion 22 has an inner tube 71 made of resin, triple helical tubes 72 covering the inner tube 71 and an outer tube 73 made of resin and covering the triple helical tubes 72. The triple helical tubes 72 include a first helical band 721 helically wound around an outer peripheral surface of the inner tube 71, a second helical band 722 helically wound around an outer periphery of the first helical band 721 in a direction opposite to a winding direction of the first helical band 721 and a third helical band 723 helically wound around an outer periphery of the second helical band 722 in a direction opposite to the winding direction of the second helical band 722. The first to third helical bands 721, 722, 723 are made of phosphor bronze or copper-silver alloy, which are materials having low magnetic susceptibility.