Video-Rate Fluorescence Molecular Tomography for Hand-held and Multimodal Molecular Imaging

In the United States, cancer is the second leading cause of death following heart disease. Although, a variety of treatment regimens are available, cancer management is complicated by the complexity of the disease and the variability, between people, of disease progression and response to therapy. Therefore, advancements in the methods and technologies for cancer diagnosis, prognosis and therapeutic monitoring are critical to improving the treatment of cancer patients. The development of improved imaging methods for early diagnosis of cancer and of near real-time monitoring of tumor response to therapy may improve outcomes as well as the quality of life of cancer patients. In the last decade, imaging methods including ultrasound, computed tomography: CT), magnetic resonance imaging: MRI), single photon emission computed tomography: SPECT), and positron emission tomography: PET), have revolutionized oncology. More recently optical techniques, that have access to unique molecular reporting strategies and functional contrasts, show promise for oncologic imaging This dissertation focuses on the development and optimization of a fiber-based, video-rate fluorescence molecular tomography: FMT) instrument. Concurrent acquisition of fluorescence and reference signals allowed the efficient generation of ratio-metric data for 3D image reconstruction. Accurate depth localization and high sensitivity to fluorescent targets were established to depths of \u3e10 mm. In vivo accumulation of indocyanine green dye was imaged in the region of the sentinel lymph node: SLN) following intradermal injection into the forepaw of rats. These results suggest that video-rate FMT has potential as a clinical tool for noninvasive mapping of SLN. Spatial and temporal co-registration of nuclear and optical images can enable the fusion of the information from these complementary molecular imaging modalities. A critical challenge is in integrating the optical and nuclear imaging hardware. Flexible fiber-based FMT systems provide a viable solution. The various imaging bore sizes of small animal nuclear imaging systems can potentially accommodate the FMT fiber imaging arrays. In addition FMT imaging facilitates co-registering the nuclear and optical contrasts in time. In this dissertation, the feasibility of integrating the fiber-based, video-rate FMT system with a commercial preclinical NanoSPECT/CT platform was established. Feasibility of in vivo imaging is demonstrated by tracking a monomolecular multimodal-imaging agent: MOMIA) during transport from the forepaw to the axillary lymph nodes region of a rat. These co-registered FMT/SPECT/CT imaging results with MOMIAs may facilitate the development of the next generation preclinical and clinical multimodal optical-nuclear platforms for a broad array of imaging applications, and help elucidate the underlying biological processes relevant to cancer diagnosis and therapy monitoring. Finally, I demonstrated that video-rate FMT is sufficiently fast to enable imaging of cardiac, respiratory and pharmacokinetic induced dynamic fluorescent signals. From these measurements, the image-derived input function and the real-time uptake of injected agents can be deduced for pharmacokinetic analysis of fluorescing agents. In a study comparing normal mice against mice liver disease, we developed anatomically guided dynamic FMT in conjunction with tracer kinetic modeling to quantify uptake rates of fluorescing agents. This work establishes fiber-based, video-rate FMT system as a practical and powerful tool that is well suited to a broad array of potential imaging applications, ranging from early disease detection, quantifying physiology and monitoring progression of disease and therapies

Near-Infrared Quantum Dots For Bioimaging And Targeting Applications

<p>Luminescent semiconductor nanocrystals or quantum dots (QDs) offer attractive characteristics as a new class of fluorescent probes for molecular, cellular and in vivo imaging. While traditional cadmium-containing QDs have been widely used in biomedical research, diagnostics, and drug delivery, the cytotoxicity arising from the release of Cd2+ ions caused by the degradation of the surface coating is deemed to be a shortfall of cadmium-based QDs for long-term cellular and in vivo imaging. Here we report a direct synthesis of silver-doped zinc selenide QDs in water with near-infrared tunable fluorescence emissions, coinciding with the biological window of transmission to offer high signal-to-noise for fluorescence imaging of cells and small animals. Glutathione, which carries both carboxyl and amino groups, serves as a stabilizing ligand and offers the flexibility of decorating the surface of the QDs with moieties such as proteins, peptides and DNA. The cytotoxicity of the as-synthesized QDs was evaluated on macrophage (RAW 264.7) cells and human mesenschymal stem cells using MTS cell viability assay. The results indicated that the silver- doped ZnSe QDs possess low cytotoxicity. In vivo biodistribution study shows that these bare QDs are different from conventional QDs, it traversed through systemic route and could accumulate in the stomach of nude mice. These QDs were conjugated to monoclonal CD44v6 antibody and tested with human gastric adenocarcinoma cell line (AGS). The results indicated the feasibility of modifying the surface properties of these QDs for efficient targeting applications. The QDs were also conjugated to heparin and used to formulate nanocomplexes with chitosan to encapsulate tumor necrosis factor-alpha. Quantitative imaging analysis revealed in vivo trafficking kinetics of the nanocomplexes to the lymph nodes after subcutaneous administration into nude mice. This study demonstrates the potential of incorporation of near-infrared-emitting QDs in nanocarrier drug delivery that allows in vivo trafficking of the biodistriution events and will be of greatly improve the development new drug nanocarrier formulations.</p>Dissertatio