Development of biomedical shape memory and superelastic alloys with low magnetic susceptibility for high static magnetic field MRI

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K18955
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Kyushu University
• Principal Investigator: Nishida Minoru 九州大学, 総合理工学研究院, 教授 (90183540)
• Co-Investigator(Kenkyū-buntansha): 田上 秀一 久留米大学, 医学部, 講師 (50398252)
• Project Period (FY): 2018-06-29 – 2021-03-31
• Keywords: 磁気共鳴画像（MRI)診断 / アーチファクト / 低磁性生体用形状記憶合金 / 低磁性生体用超弾性合金 / Hf基合金 / Ag基合金 / Au基合金 / Ag-Al合金

Outline of Final Research Achievements

When a metallic medical device is detained in the living body, the device is magnetized and then a new magnetic field occurs because of a strong magnetic field of MRI. Consequently, the image loss region which is called the artifact is produced around the device. Ti-based alloys have relatively low magnetic susceptibility, which are applied to various medical devices such as stent, artificial joint, bone plate etc. However, the demand of high magnetic field MRI is indispensable for an accurate diagnosis. From the above　background, we try to develop Hf, Ag and Au-based shape memory and superelastic alloys, since Hf and Ag have lower magnetic susceptibility in comparison to Ti and Au has diamagnetism. We have found that Ag-Al alloy system is promising for the reduction of artifact.

Free Research Field

材料組織学

Academic Significance and Societal Importance of the Research Achievements

MRI診断装置の高静磁場化に伴い問題となる体内に留置された金属製医療デバイスによるアーチファクトを低減する目的で，従来の医療材料の主流であるチタン(Ti)より低磁化率金属であるハフニウム(Hf)，銀(Ag)，反磁性金属である金(Au) に着目し，これらをベースとする形状記憶・超弾性合金を創製することを目的として，種々の合金を溶製し，機能発現の素過程である熱弾性マルテンサイト変態を確認するための組織観察，物性測定，MRI撮像を行った．その結果，Ag-Al合金系がアーチファクトの低減に有望な形状記憶・超弾性合金となり得ることを見出した．