Kota Nomura

Magnetic Particle Imaging (MPI) is an imaging modality that directly detects the nonlinear responses of magnetic nanoparticles (MNPs). Spatial encoding is achieved by saturating the magnetic moment of MNPs almost everywhere except in a special point called the field-free region in which a magnetic field vanishes. Recently, MPI sensitivity was improved using a field-free line (FFL) in which a field-free region was formed as a line. An MPI with a FFL device was developed using a neodymium magnet and an iron yoke to image objects with a small amount of magnetic nanoparticles, such as in biological systems. We have been developing MPI equipment for detecting amyloid-β, a causative agent of Alzheimer's disease. We attached amyloid-β probes to nanoparticles. In our development, we discriminated between magnetic particles that are bound to biological tissue from those that are suspended in the brain. We focused on the differences in relaxation times due to the change in the hydrodynamic diameter between the bound and unbound particles. Because the bound particles have a larger apparent particle size and do not rotate when an AC magnetic field is applied, the relaxation time is different from the unbound particles. Since the differences in the responses to the AC magnetic field appear as relaxation times, we investigated a particle-discrimination method using these differences and studied the magnetization response of magnetic nanoparticles using our developed MPI device.

Decommissioning of aged nuclear reactors is planned, and cutting technologies for thick structure are necessary to reduce storage space of radioactive wastes. Though thermal cutting technology is suitable for cutting thick materials, radioactive fume is one of the problems due to increase the environmental dose. A water jet-guided laser cutting technology is one of the solutions for cutting irradiated materials, because radioactive fume is confined in the water and doze level won’t be increased. However, this technology was developed for precision machining like dicing and slotting of silicon wafers, cutting thick materials by using this process is very diffcult. In this study, cutting technology for thick material with a water jet-guided laser was discussed. Phenomenon during cutting thick stainless steel was observed by using high speed camera and optimum conditions for both water jet and laser cutting were derived. Finally, 50mm thick stainless steel plate was successfully cut by using this technology.