A control unit for a magnetic particle spectrometer

Abstract

Magnetic Particle Imaging (MPI) is a quite new imaging technique, based on the non-linear magnetization behavior of superparamagnetic iron oxide nanoparticles (SPIOs). These SPIOs are applied to a patient as tracer material. An important key aspect for successful and reliable imaging is tracer development and characterization. Hence, a Magnetic Particle Spectrometer (MPS) is needed to perform extensive studies about the SPIOs dynamic magnetization behavior. The MPS hardware build-up consists mainly of a drive coil, a receive coil, a cooling circuit, amplifiers and a control unit. This paper proposes a new self-contained control unit hardware system based on a System-On-Chip (SoC) Field-Programmable-Gate-Array (FPGA). The control unit controls, collects, and maintains data acquisition, coil excitations and the behavior of the cooling circuit in real-time. The SoC is also able to pre-process measurement data (i.e. filtering, averaging, up- and down-sampling etc.). The generation of the magnetic field in the drive coil is controlled by a 14 bit Digital/Analog Converter (DAC) coupled with an external amplifier. The receive coil signal is amplified and digitalized via a 14 bit Analog/Digital Converter (ADC). To prevent system overheating, also temperature is supervised and kept under certain limits. For that purpose four Resistive Thermal Devices (RTDs) in combination with a cooling unit are utilized. The transmission of measurement data is realized via USB 2.0 with up to 40 MByte/s. The USB link can also be used to setup the control unit and as power supply for the self-containing SoC.