Magnetic Resonance Imaging Using a Magnetoresistive Sensor With a Flux Transformer

In this study, we developed a signal detection unit composed of a magnetoresistive sensor and magnetic flux transformer circuit for ultralow field magnetic resonance imaging (ULF-MRI). The equivalent noise level of the detection unit was reduced to approximately 1/20 using the flux transformer compared to the original magnetoresistive sensor. In addition, the flux transformer made of copper wires and plastic bobbins contributed to preventing the distortion of the magnetic field for MRI measurements. Spin-echo (SE) magnetic resonance signal measurements and ULF-MRI measurements were demonstrated using a phantom at a static magnetic field of 1 mT. The SE signal and the MR image were successfully obtained by the developed signal detection unit. These results show the effectiveness of using the flux transformer to realize the ULF-MRI measurement using magnetoresistive sensors.