超低磁場SQUID-NMR/MRI装置の異物検査への応用

摘要

近年，高磁場NMR/MRIよりも低コストで簡易的なシステムを構築できるという利点から，数10μTオーダーの超低磁場とSQUIDを用いたNMR7MRIが検討されている.現在，我々は異物検査応用のため，永久磁石と高温超伝導SQUID用いた超低磁場NMR/MRI装置を開発している.本研究では，初期検討として，試作した装置を用いて水サンプルに異物が混入した時のNMRスぺクトルおよび一方向に傾斜磁場を印加した1D-MRIを計測した.この結果，磁性体の異物の場合，NMRスペクトル全体の強度が減衰した.一方,非磁性異物に1D-MRIを適用した場合，異物の存在する箇所でスペクトルの減衰を確認することができた.このことから,本装置を用いた異物検査応用の可能性を示すことができた.%Nuclear magnetic resonance(NMR)and magnetic resonance imaging(MRI)in ultra-low field(ULF)using SQUIDs have attracted attention in recent years because the systems do not require complicated apparatus such as superconducting magnets. Thus it can be compact, easy to handle, and inexpensive. We have developed an ULF-NMR/MRI system utilizing an HTS-SQUID for an application of contaminant detection in foods. In this work, we measured NMR signals from water samples with or without various contaminants, such as stainless steel(SUS304), aluminum, and glass balls using the system. In the case of the magnetic contaminants, the whole NMR signal intensity was reduced compared to that from the sample without the contaminant due to the remnant field of the contaminant. One-dimensional(1D)MRIs of the samples with non-magnetic contaminants were also measured. In the 1D-MRIs， changes of the MRI spectra were measured at center frequency, which corresponded to positions of the contaminants in the sample. These results show that the feasibility of the system to detect various contaminants in foods.