Browsing by Subject "Magnetic Nanoparticles"
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Item Detection of Magnetic Nanoparticles for Bio-sensing Applications(2013-06) Tu, LiangSuperparamagnetic Nanoparticles (MNPs) are used as probes to detect biomarkers (protein, DNA, etc.) by using a search coil based scheme for volume detection and by using a Giant Magneto-Resistance (GMR) sensor for surface detection. In search coil detection scheme, a low frequency field is applied to saturate the MNPs and a high frequency field is applied to modulate the nonlinearity of the magnetization into the high frequency region where the noise floor is lower. Under an ac magnetic field, MNPs above certain hydrodynamic size (for Iron Oxide is around 20nm) will experience physical rotation called Brownian relaxation. By studying the phase information of the mixing frequencies, the Brownian relaxation time can be monitored in real time thus dynamic bio-molecular interaction can be recovered. The N�el and Brownian relaxation of MNPs with different magnetic and hydrodynamic properties has been investigated by using a different DC bias field and AC field frequency. The specific response from each MNP can be used as magnetic identification in nano-scale application. A Giant Magneto-Resistance (GMR) sensor array is also used for MNPs detection. Compared with the search coil, GMR sensor is more sensitive but requires surface modification for bio- molecular detection. A low-noise Printed Circuit Board is designed and assembled to implement Wheatstone bridge, multiplexing function, and signal amplification. An AC field is applied to the entire sensor array while an AC current is flowing through a specific sensor. The sensor response will generate mixing frequency terms as the multiplication of field frequency and current frequency. All the active sensors printed with specific capture antibodies are scanned sequentially, recorded in real time, and compared with the reference sensor which is covered by a thick protection layer. Signal to noise ratio for the integrated system is studied by considering the noise contribution from all components.Item Dosimetry and Application of Magnetic Nanoparticles as an Intraocular Shielding Method in Iodine-125 Eye Plaque Brachytherapy(2022-05) Oare, CourtneyUveal melanoma is a rare diagnosis but the most common intraocular malignancy. Eye plaque brachytherapy has been the standard of care since the introduction of the Collaborative Ocular Melanoma Study (COMS), which proved excellent tumor control and survival for uveal melanoma patients. Despite these successes, normal tissues of the eye receive excessive dose during treatment that is historically unavoidable. The purpose of this work is to implement a novel intraocular shielding technique to reduce normal tissue dose while maintaining tumor control, using a magnetic plaque and ferromagnetic nanoparticles. The ferromagnetic nanoparticles studied have previously been used intraocularly for retinal detachment. A new application of ferromagnetic nanoparticles is studied. Previously literature has extensively studied outcomes and incidence rates of normal tissue complications for plaque brachytherapy patients, however a gap exists addressing what normal tissue dose is acceptable to avoid such complications. To answer this question, a retrospective study was conducted with uveal melanoma patients treated with COMS plaques. The conclusions can not only help predict normal tissue complication in the future, but also justify the amount of shielding necessary with magnetite nanoparticles. A proof-of-concept magnetic plaque was designed to guide ferromagnetic nanoparticles around the tumor, creating a shield for normal tissues. The distribution of ferrofluid was fully characterized with film and Monte Carlo (MC) methods to determine dose distribution throughout the eye. Using a novel film calibration technique, radiochromic film was calibrated using low energy Iodine-125. In addition, the MC-simulated source and COMS plaque were benchmarked to validate the source code and the accuracy of the modeled sources and plaque. In this work the retrospective study is presented followed by film and MC measured dose distribution in the eye with ferromagnetic nanoparticle shielding. Lastly, the fluid flow and fluid distribution are simulated with multiphysics software. The results can be clinically applied to establish how much shielding is necessary to prevent normal tissue toxicity, and what magnitude of dose reduction is feasible based on the presented proof-of-concept design. A supplementary video file shows the fluid flowing against gravity, toward the custom magnetic plaque, distributing around a 5 mm tumor. The video enhances the content and figures introduced in Chapter 5.Item Dual-mode Ultrasound: Magnetoacoustics for Biological Tissue Imaging and Ultrasound Mediated Neuromodulation(2018-08) Yu, KaiUltrasound is a type of mechanical energies that have been widely employed in clinical diagnosis and therapeutic use. The overall goal of this dissertation is to further develop ultrasound-based imaging modality in assisting cancer diagnosis and explore the transcranial focused ultrasound (tFUS) in brain stimulation. In this dissertation, I firstly summarize my research on detecting cancer by harnessing a passive-mode ultrasound generated by magnetoacoustics. Probing the electrical conductivity of in vivo tissues, a high-frequency magnetoacoustic tomography with magnetic induction (hfMAT-MI) imaging system has been developed for cancer imaging with 1-mm spatial resolution. With the aid of magnetic nanoparticles (MNPs), the magnetoacoustic tomography is further enhanced in the imaging contrast and thus used to reconstruct the in vivo biodistribution of MNPs noninvasively. By reversing the imaging model, I secondly introduce my studies of transmitting active-mode pulsed ultrasound in a transcranial way and electrically sensing global and local brain responses to the deposited low-intensity ultrasound energy. In this second research topic, non-invasive electroencephalography (EEG)-based source imaging (ESI) is used to map the whole brain dynamics, which allows to better understand the effects of tFUS stimulation with high spatiotemporal resolutions. Furthermore, towards a mechanistic investigation, intracranial electrophysiological recordings from in vivo brains receiving low-intensity tFUS uncover an intrinsic cell-type specificity of neurons in responding to levels of ultrasound pulse repetition frequencies. Potential confounding factors, i.e. auditory side effects and somatosensation are also studied to thus identify the direct neuronal effects induced by the tFUS in vivo.