An active cancellation method to improve the sensitivity for amplitude modulation magnetic particle imaging

Abstract

Since the amplitude modulation magnetic particle imaging use the cancellation method to remove the direct feedthrough interference of the sinusoidal excitation field so that the sensitivity of MPI system depend on the amount of feedthrough interference of excitation field. The conventional cancellation method used single power to apply to two excitation coils, it will issue a difference about amplitude and phase of receive coil and cancellation coil. An active cancellation method uses two independent powers for two excitation coils, and controls two powers to reduce the difference of amplitude, phase between receive coil and cancellation coil so that the feedthrough interference of excitation field will reduce significant than conventional cancellation method. The works proposed an active cancelation method to suppress fundamental frequency from the excitation field but keep full dynamic range of harmonics from particles which contributes to both better image reconstruction and sensitivity of MPI system. The method included two excitation coils, one receive coil and one cancelation coil. After they are calibrated in mechanical by placing the coils, an electrical calibration is automatically controlled by two different power supplies in the sufficient accuracy. As a results, the total received signal after the active cancellation method is reduced nearly by 6dB / factor 2, from 50mV to 25mV comparing with the conventional cancellation method. Moreover, the phase difference about 71.645°between the excitation coils is adjusted for the cancellation.