Development and Evaluation of Approaches for Quantitative Optical Molecular Imaging of Neoplasia
Rosbach, Kelsey Jane
Richards-Kortum, Rebecca Rae
Doctor of Philosophy
This thesis develops and evaluates three approaches for quantitative molecularly-targeted optical imaging of neoplasia. The first approach focuses on widefield imaging of biomarkers near the tissue surface for early detection applications; this approach is demonstrated in freshly resected oral tissue. Most oral cancers are not detected until the disease has spread, but topical application of targeted imaging agents allows rapid visualization of biomarker expression, giving real-time, objective information. Epidermal growth factor receptor (EGFR) expression was quantified in patient samples using fluorescent epidermal growth factor. Dysplasia (n=4) and cancer (n=13) had an average 2.3-fold and 3.8-fold increase in signal compared to normal tissue. EGFR expression was assessed along with metabolic activity using a fluorescent glucose analog, 2-NBDG, in 9 patient samples. A classification algorithm using quantitative image features resulted in an area under the curve (AUC) of 0.83, though the main advantage of this technique may be to understand spatial heterogeneity of biomarker expression and how this correlates with disease. The next approach focuses on high-resolution optical imaging through a needle to detect metastases in lymphoid tissue for clinical staging applications; this approach is demonstrated in resected lymph nodes from breast cancer patients. These patients often require removal of nodes, but an optical imaging strategy using topical application of imaging agents in vivo may classify nodes as normal or metastatic, thus reducing unnecessary removal of normal nodes and improving metastasis detection. Proflavine, a nuclear dye, was topically applied to 43 nodes. A classification algorithm developed from quantitative image features distinguished normal lymphoid tissue from metastases with an AUC of 0.84. Because optical imaging is depth limited, the final approach combines high-resolution optical imaging with magnetic resonance imaging (MRI) for multimodal evaluation of deep tissue. An imaging agent functional in both optical and MRI was developed by co-loading fluorescent EGFR antibodies and gadolinium-based contrast agents in silicon discs. These discs accumulate in tumors, resulting in localized delivery of imaging agents. The research presented here can be applied to understanding tumor biology and biomarker heterogeneity, with the future clinical goal of improving identification of disease and determination of appropriate therapy for cancer patients.