Room-Temperature Magnetoelectric Sensor System For Direct Detection of Organ Iron Profile
Open Access
- Author:
- Xi, Hao
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 24, 2019
- Committee Members:
- Qiming Zhang, Dissertation Advisor/Co-Advisor
Qiming Zhang, Committee Chair/Co-Chair
Mehdi Kiani, Committee Member
Xingjie Ni, Committee Member
Qing X Yang, Outside Member
Nanyin Zhang, Outside Member
Kultegin Aydin, Program Head/Chair - Keywords:
- Magnetoelectric
Sensor
piezoelectric
SQUID
Liver Iron
Tissue Iron
Biomagnetics
Biomedical Application - Abstract:
- The dissertation explores a highly interdisciplinary application of the Magnetoelectric (ME) Sensors. The ME sensors, integrated with piezoelectric phase and magnetostrictive phase, show extraordinary sensitivity for AC magnetic fields and are, therefore, very promising towards all sorts of small-magnetic-field-sensing applications, especially the biomedical devices. Iron plays a vital role in the human body. Absorbing and storing too much iron in the body organs can, however, cause damage or even destroy an organ. It has been established that liver iron concentration (LIC) is a direct indication of body iron level. For Liver Iron Concentration (LIC) measurements, the liver biopsy method is considered the “gold standard”, which is invasive with risks and cannot be used repetitively. Alternatively, MRI and Superconducting Quantum Interference Device (SQUID) based Biomagnetic Liver Susceptometry (BLS) are the current non-invasive options, which are expensive and not widely available. This dissertation focuses on the development of a low cost and room-temperature-operated ultra-sensitive biomagnetic sensor System based on the Magnetoelectric effects for BLS, which can also perform tissue iron profiling. A novel design of the liver susceptometer, utilizing the ME composite sensors, has been demonstrated to be able to detect the biomagnetic responses from tissues with varying iron concentrations. The signal-to-noise ratio (SNR) is a key parameter for any sensor design and development. A high SNR is always desired within the detection range of the sensor system. With the utilization of high-quality piezo-relaxors, for example, PIN-PMN-PT single crystals, a dramatic improvement on the ME coefficient is obtained, and hence the signal intensity. Besides, given the fact that biomagnetic signals are almost always weak by nature, one important method to raise the SNR of an ME sensor system is to achieve effective noise reduction. A gradiometer structure helps the system discriminate against background magnetic noises. The adoption of horizontal scanning with a “water bath” method enabled the automatic elimination of the diamagnetic contribution from surrounding (phantom) tissues. Improved sensor fabrication methods help the system reduce dielectric noises and reject common-mode noises. The ME sensor system utilizing PIN-PMN-PT single crystal as the piezo phase shows dramatic improvements in its performance and is demonstrated to measure magnetic signals from real animal liver tissues (mouser liver tissue) of very small volume (~ 3 cc). To better understand the magnetic response from the targeted tissue and the signals captured in the sensor system, a detailed computer simulation and calculation is carried out. The simulation model is implemented in a “two-step” method – the applied magnetic field, the magnetic field that excites the targeted tissue leading it to respond, is calculated using the COMSOL Multiphysics package via Finite Element Methods (FEM). The calculated magnetic field data will be then transferred to a 3-D numerical model coded with MATLAB to calculate the responding magnetic field. It is shown that, depending on the principle center position of the sensor, the amplitudes of the frequency components in the spectrum for the time-domain signals can vary. The peak value of the 1f signal is related to the boundary of the phantom and can be used to determine the location of the phantom underneath the over-layer tissues directly. The simulation model is studied and validated at each step for multiple experiment setups and calibrated with data obtained in practical experiments to ensure its validity and accuracy. The computer simulation will provide specific design and optimization of ME Sensor System, as well as fine-tuning of the design parameters for both signal channel and array prototypes. Sensor array enables more opportunities in terms of biomedical detection, mapping and image reconstruction. Through the combinations of signals from multiple channels, more information is sorted out, for example, the iron profile in the area being detected, which makes it feasible to reconstruct the tissue boundaries, field distributions and ultimately medical mapping and imaging. ME sensor array systems, exploiting the compact size and room temperature operation, are investigated. A vertical ME sensor array along the Z-direction is shown to be sensitive to the skin-liver distance change which can be leveraged to calibrate and eliminate the effects of various skin-liver distance. Horizontal 1-D ME sensor arrays for both X- and Y- directions are demonstrated to be able to measure phantoms with subsections of different iron concentrations, to map the one-dimensional profile of the iron concentration for the phantom and to determine the target (such as a phantom, or the liver) boundary without the aid of other additional methods, such as ultrasound imaging for liver localization. The results of the prototype sensor devices show the feasibility of an array ME-sensors for detecting iron profile and opens up many possibilities for direct imaging enabled by the ME sensor array system. Considering the wide presence of biomagnetic signals in human organs, the potential impact of such biomagnetic devices on medicine and health care cost could be enormous and far-reaching.