15 March 2011 Transmit filter design methods for magnetic particle imaging
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Magnetic particle imaging (MPI) has emerged as a new imaging modality that uses the nonlinear magnetization behavior of superparamagnetic particles. Due to the need to avoid contamination of particle signals with the simultaneous excitation signal, MPI transmit systems require different design considerations from those in MRI, where excitation and detection are temporally decoupled. Specifically, higher order harmonic distortion in the transmit spectrum can feed through to and contaminate the received signal spectrum. In a prototype MPI scanner, this distortion needs to be attenuated by 90 dB at all frequencies. In this paper, we describe two methods of filtering out harmonic distortion in the transmit spectrum. The first method uses a Butterworth topology while the second a cascaded Butterworth-elliptic topology. We show that whereas the Butterworth filter alone achieves around 16 and 32 dB attenuation at the second and third harmonics, the cascaded filter can achieve around 65 and 73 dB at these harmonics. Finally, we discuss how notch placement in the stopband can also be applied to design highpass filters for MPI detection systems.
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Bo Zheng, Bo Zheng, Patrick Goodwill, Patrick Goodwill, Steven Conolly, Steven Conolly, } "Transmit filter design methods for magnetic particle imaging", Proc. SPIE 7965, Medical Imaging 2011: Biomedical Applications in Molecular, Structural, and Functional Imaging, 79652H (15 March 2011); doi: 10.1117/12.878443; https://doi.org/10.1117/12.878443

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