| 摘要 |
PURPOSE:To make it possible to neglect a heat generation amount and to enhance the ratio of S/N, by applying a strong magnetic field component generated by a stepwise changing drive current and a magnetic field component weak in magnetic field intensity as compared to said strong magnetic field component. CONSTITUTION:A drive current value to be flowed to an electrostatic magnetic field generator is set to IM in order to achieve a strong magnetic field component HM and a region to be measured is strongly magnetized by the component HM. When the time interval of HM is set to DELTAT, a time required in magnetization of this time is about a spin-grid relaxation time and, threfore, the time interval DELTAT of HM also requires about T1. In this case, when a living body specimen is used as an object, T1 is about several hundreds ms-3sec and, even if the time of this extent is used as the time interval DELTAT of HM to perform the generation of a magnetic field of about several k Gauss in an air-core coil, a heat generation amount can be neglected. In the next step, the drive current is stepwise lowered to Io to generate a weak magnetic field component Ho. As magnetic field intensity capable of being generated by the air-core coil, about several hundreds Gauss is enabled and, as compared to the case for performing signal detection only under the magnetic field of this extent, the ratio of S/N is largely improved. |
