Methods And System Design For AC Susceptibility Measurement Of Magnetic Nanoparticles

Measuring and controlling temperature precisely is a difficult problem in the medical field applications of magnetic nanoparticles all the time. Magnetic nano-temperature measurement technique and temperature imaging technology is not yet mature due to the lake of in-depth study of ac susceptibility models and accurate measurement. It is critical to study ac susceptibility thoroughly that ac susceptibility acts as an important physical quantity of magnetic nanoparticles in the medical field applications. This thesis was proposed to use sine sweep excitation to realize the measurement of ac susceptibility, so as to improve the accuracy of the ac susceptibility measurement, thus achieving accurate temperature measurement and temperature control. In view that the RF field is high frequency magnetic field in hyperthermia application, the RF field is used in high frequency magnetic field, and the low-frequency excitation field can not achieve fast measurement speed in applications of magnetic nanoparticle concentrati on and temperature imaging. This thesis also presents a new method suitable for measuring highfrequency excitation of ac susceptibility. The study of the system has an important significance to promote the application of magnetic nanoparticles in the biomedical field.Firstly, this thesis describes the application of magnetic nanoparticles in the biomedical field, concluding that it is important to measure temperature and control temperature precisely, then proposes that increase the measurement accuracy of ac susceptibility which is intermediate physical will be a breakthrough to broaden the field of magnetic nanoparticles in medicine application. By using the sine sweep signal as the excitation signal can achieve to improve the measurement accuracy of ac susceptibility successfully.Then, this thesis introduces key theories and the measurement program of ac susceptibility. In view of the field of high-frequency magnetic excitation medical applications, this thesis proposes a new method suitable for measuring high-frequency excitation of ac susceptibility. Then the thesis describes the ac susceptibility measurement system from hardware and software design in detail. Determining to choose the solenoid coil as the excitation coils by ANSYS simulation to ensure the system can produce uniform and stable magnetic field, and choose a pair of differential coil as a sensor to transform the magnetic signals to electrical signals.Finally, using two different schemes to complete the ac susceptibility measurement experiment for different concentrations samples under the sweep excitation and comparing the experimental results to the simulation results of Debye theory. It was found that the experimental results are consistent with the theoretical results. It was further proved the feasibility of this ac susceptibility measurement method.