Application of β-NMR to spectroscopy and imaging

Nuclear magnetic resonance (NMR) using β-decay radioisotopes, known as “β-NMR,” is used for research in nuclear physics. Recently, nuclear magnetic moments of β-decay radioisotopes have been precisely measured by β-NMR. Therefore, β-decay radioisotopes can be used for NMR spectroscopy in material sciences. Nuclei, whose spin is zero, such as 12C and 16O, cannot be used in conventional NMR. However, nonzero-spin radioactive isotopes of carbon and oxygen can be used in β-NMR. This advantage is powerful for investigating organic materials that cannot be investigated using conventional NMR. A technique is being developed to extend β-NMR for imaging use in magnetic resonance imaging (MRI). In this study, the imaging function was realized by installing β-ray tracking detectors in a β-NMR device. Nuclear-spin-polarized radioisotopes were injected into a sample, and β-rays were emitted from their positions. Consequently, one could track back β-ray source positions on the sample. These detectors were installed into a dipole magnet to observe the magnetic resonances. A radio frequency coil was installed surrounding the sample. By combining information about the β-ray tracks and magnetic resonances, it was possible to obtain NMR spectra and images. This method is called “β-MRI.” The system was evaluated, and its performances were estimated.