Browsing by Subject "Ultrasound imaging"
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Item Biomedical photoacoustics beyond thermal expansion : photoacoustic nanoDroplets(2012-05) Wilson, Katheryne Elizabeth; Emelianov, Stanislav Y.; Fowlkes, Brian; Hamilton, Mark; Sokolov, Konstantin; Williams, RobertThe recent increase in survival rates of most cancers is due to early detection greatly aided by medical imaging modalities. Combined ultrasound and photoacoustic imaging provide both morphological and functional/molecular information which can help to detect and diagnose cancer in its earliest stages. However, both modalities can benefit from the use of contrast agents. The objective of this thesis was to design, synthesize, and test a nano-sized, dual contrast agent for combined ultrasound and photoacoustic imaging named Photoacoustic nanoDroplets. This agent consists of liquid perfluorocarbon nanodroplets with encapsulated plasmonic nanoparticles. These dual contrast agents utilize optically triggered vaporization for photoacoustic signal generation, providing significantly higher signal amplitude than that from the traditionally used mechanism, thermal expansion. Upon pulsed laser irradiation, liquid perfluorocarbon undergoes a liquid-to-gas phase transition generating giant photoacoustic transients from these dwarf nanoparticles. Once triggered, the gaseous phase provides ultrasound contrast enhancement. Demonstrated in this work are the design, synthesis, characterization, and testing of Photoacoustic nanoDroplets in phantom and animal studies, and preliminary work into adapting these agents into targeted, drug delivery vehicles for simultaneous detection, diagnosis, and treatment of diseases.Item Functional and molecular photoacoustic imaging for the detection of lymph node metastasis(2013-12) Luke, Geoffrey Patrick; Emelianov, Stanislav Y.Accurate detection of the spread of cancer is critical for planning the best treatment strategy for a patient. Currently, an invasive sentinel lymph node biopsy is commonly used to detect metastases after a primary tumor is detected. This procedure results in patient morbidity, requires weeks of waiting, and is prone to sampling error. This dissertation presents new developments in an emerging biomedical imaging modality – photoacoustic imaging – and their application to improving the detection of metastases in the lymphatic system in a metastatic mouse model of squamous cell carcinoma of the oral cavity. Label-free spectroscopic photoacoustic imaging is demonstrated to detect hypoxia that results from the development of sub-millimeter cancer foci in the lymph node. In order to improve the sensitivity to micrometastases, molecularly-activated plasmonic nanosensers which are targeted to the epidermal growth factor receptor are introduced. The nanosensors are demonstrated to detect metastases consisting of only a few tens of cells. Improvements to spectroscopic photoacoustic imaging are then demonstrated by selecting imaging wavelengths based on the spectral properties of the optical absorbers. Finally, a new contrast agent – silica-coated gold nanoplates – are used to map the sentinel lymph node with high contrast. The final result is a set of tools that can be used to noninvasively detect micrometastases and improve molecular photoacoustic imaging.Item Pulsed magneto-motive ultrasound imaging(2012-05) Mehrmohammadi, Mohammad; Emelianov, Stanislav Y.Nano-sized particles are widely regarded as a tool to study biological events at cellular and molecular levels. However, there are only a few imaging modalities that can visualize interactions between nanoparticles and living cells. A new technique -- pulsed magneto-motive ultrasound imaging, capable of in-vivo imaging of magnetic nanoparticles at improved depth and in real-time is introduced in this study. In pulsed magneto-motive ultrasound imaging, an external high-strength pulsed magnetic field is applied to induce motion within magnetically labeled tissue and ultrasound is used to detect the induced internal tissue motion. A laboratory prototype of a pulsed magneto- motive ultrasound imaging system was built, tested and optimized through modeling and experimental studies using tissue-mimicking phantoms, ex-vivo tissue samples and in- vivo mouse tumor model. The results demonstrated a sufficient contrast between normal and iron-laden tissue labeled with ultra-small magnetic nanoparticles. Finally, further modifications and research directions are discussed which can eventually lead to development of a clinically applicable pulsed magneto-motive ultrasound imaging system.Item Ultrasound and photoacoustic imaging to monitor stem cells for tissue regeneration(2014-05) Nam, Seung Yun; Emelianov, Stanislav Y.; Suggs, Laura J; Pearce, John A; Dunn, Andrew K; Hall, Neal ARegenerative medicine is an interdisciplinary field which has advanced with the use of biotechnologies related to biomaterials, growth factors, and stem cells to replace or restore damaged cells, tissues, and organs. Among various therapeutic approaches, cell-based therapy is most challenging and exciting for both scientists and clinicians pursuing regenerative medicine. Specifically, stem cells, including mesenchymal stem cells and adipose-derived stem cells, are promising candidate cell types for cell-based therapy because they can differentiate into multiple cell types for tissue regeneration and stimulate other cells through neovascularization or paracrine signaling. Also, for effective treatment using stem cells, the tissue engineered constructs, such as bioactive degradable scaffolds, that provide the physical and chemical cues to guide their differentiation are incorporated with stem cells before implantation. Also, it was previously demonstrated that tissue-engineered matrices can promote tubulogenesis and differentiation of stem cells to vascular cell phenotypes. Hence, during tissue regeneration after stem cell therapy, there are numerous factors that need to be monitored. As a result, imaging-based stem cell tracking is essential to evaluate the distribution of stem cells as well as to monitor proliferation, differentiation, and interaction with the microenvironment. Therefore, there is a need for a stem cell imaging technique that is not only noninvasive, sensitive, and easy to operate, but also capable of quantitatively assessing stem cell behaviors in the long term with high spatial resolution. Therefore, the overall goal of this research is to demonstrate a novel imaging method capable of continuous in vitro assessment of stem cells as prepared with tissue engineered constructs and noninvasive longitudinal in vivo monitoring of stem cell behaviors and tissue regeneration after stem cell implantation. In order to accomplish this, gold nanoparticles are demonstrated as photoacoustic imaging contrasts to label stem cells. In addition, ultrasound and photoacoustic imaging was utilized to monitor stem cells and neovascularization in the injured rat tissue. Therefore, using these methods, tissue regeneration can be promoted and noninvasively monitored, resulting in a better understanding of the tissue repair mechanisms following tissue injury.