Au-Pt Alloy for Artifact-Free MRI Compatibility
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Solution Overview
Problem
Conventional medical alloys used in MRI environments suffer from high magnetic susceptibility, leading to artifacts that hinder accurate surgery and diagnostics due to their inability to match the magnetic susceptibility of biopsy tissue, which is approximately −9 ppm.
Innovation Solution
An Au—Pt alloy with a composition of 34 to 36 mass % Pt and a balance of Au, ensuring a single α-phase structure and minimal precipitates to achieve a magnetic susceptibility range of −13 to −5 ppm, closely matching that of water, thereby minimizing artifact occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional medical alloys (stainless steel, Co-Cr alloy, Pt-W alloy) are used, then biocompatibility, corrosion resistance, and workability are satisfied, but magnetic susceptibility is high causing artifacts in MRI images
Solution Approach 1:
The patent changes the chemical composition parameters of the alloy by selecting Au as the base metal (0.99 mass%) and Pt as the alloying element (0.01-0.05 mass%), specifically controlling the Pt content to achieve magnetic susceptibility within -13 to -5 ppm. This parameter optimization resolves the contradiction by achieving artifact-free MRI compatibility while maintaining medical alloy reliability through biocompatibility and corrosion resistance
Solution Approach 2:
The patent creates a composite alloy system combining Au and Pt metals with specific compositional ratios. The Au-Pt composite material achieves magnetic susceptibility matching biopsy tissue (-9 ppm) while maintaining the mechanical and chemical properties required for medical applications, thus resolving the contradiction between artifact suppression and material reliability
2Object-affected harmful factors
If Au-Pt alloy composition is adjusted to achieve target magnetic susceptibility, then artifact-free MRI compatibility is achieved, but manufacturing precision and phase structure control become critical
Solution Approach 1:
The patent precisely controls the Pt content parameter within 0.01-0.05 mass% range to achieve the target magnetic susceptibility. This narrow compositional window requires high manufacturing precision, which is resolved through optimized melting and casting processes that ensure homogeneous single-phase structure formation
Solution Approach 2:
The patent utilizes phase transition control during solidification to achieve a homogeneous single-phase structure. By controlling the cooling rate and solidification process, the alloy forms a uniform phase distribution without precipitates, ensuring both magnetic susceptibility control and manufacturing precision
3Quantity of substance
If Pt content in Au-Pt alloy is increased to adjust magnetic susceptibility, then magnetic susceptibility approaches target value, but alloy homogeneity and precipitate formation are affected
Solution Approach 1:
The patent optimizes the Pt content parameter to a specific range (0.01-0.05 mass%) that achieves the target magnetic susceptibility without causing phase separation or precipitate formation. This precise parameter control maintains alloy homogeneity while achieving the desired magnetic properties
Solution Approach 2:
The patent ensures uniform Pt distribution throughout the alloy matrix, avoiding local concentration variations that would cause precipitates. The homogeneous single-phase structure is achieved through controlled solidification and appropriate heat treatment, maintaining composition stability
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 Au—Pt alloy exhibits excellent biocompatibility, corrosion resistance, and workability, effectively suppressing artifacts in MRI environments, making it suitable for medical appliances like embolus treatment coils.
Implementation Method 1
Au is a diamagnetic metal having magnetic susceptibility of -34 ppm... the magnetic susceptibility of the artifact-free material is approximate to the magnetic susceptibility (-9 ppm) of the water... the magnetic susceptibility (-13 to -5 ppm) of ±4 ppm with respect to that of the water
Data Source
AI summary
The present invention is an alloy for medical use including an Au--Pt alloy, containing 34 to 36 mass % of Pt with the balance being Au, and having an .alpha.-phase single structure in which a ratio of a peak intensity (X) of a Pt (111) plane to a peak intensity (Y) of an Au (111) plane (X/Y) is 0.01 or less in an X-ray diffraction analysis. The alloy can be produced in such a manner that after the Au--Pt alloy ingot is molten and cast, cold working and a heat treatment for homogenization are performed at least two times on the molten and cast alloy. The alloy of the present invention is an artifact-free material that exhibits excellent compatibility with a magnetic field environment such as an MRI and has magnetic susceptibility of .+-.4 ppm with respect to that of water.