Despite significant advances in medical imaging technologies, there currently exist no tools to effectively assist healthcare professionals during surgical procedures. In turn, procedures remain subjective and dependent on experience, resulting in avoidable failure and significant quality of care disparities across hospitals. Optical techniques are gaining popularity in clinical research because they are low cost, non-invasive, portable, and can retrieve both fluorescence and endogenous contrast information, providing physiological information relative to perfusion, oxygenation, metabolism, hydration, and sub-cellular content. Near-infrared (NIR) light is especially well suited for biological tissue and does not cause tissue damage from ionizing radiation or heat. My dissertation has been focused on developing rapid imaging techniques for mapping endogenous tissue constituents to aid surgical guidance. These techniques allow, for the first time, video-rate quantitative acquisition over a large field of view (> 100 cm2) in widefield and endoscopic implementations. The optical system analysis has been focused on the spatial-frequency domain for its ease of quantitative measurements over large fields of view and for its recent development in real-time acquisition, single snapshot of optical properties (SSOP) imaging. Using these methods, this dissertation provides novel improvements and implementations to SSOP, including both widefield and endoscopic instrumentations capable of video-rate acquisition of optical properties and sample surface profile maps. In turn, these measures generate profile-corrected maps of hemoglobin concentration that are highly beneficial for perfusion and overall tissue viability. Also utilizing optical property maps, a novel technique for quantitative fluorescence imaging was also demonstrated, showing large improvement over standard and ratiometric methods. To enable real-time feedback, rapid processing algorithms were designed using lookup tables that provide a 100x improvement in processing speed. Finally, these techniques were demonstrated in vivo to investigate their ability for early detection of tissue failure due to ischemia. Both pre-clinical studies show endogenous contrast imaging can provide early measures of future tissue viability. The goal of this work has been to provide the foundation for real-time imaging systems that provide tissue constituent quantification for tissue viability assessments. / 2018-01-09T00:00:00Z

Once diagnosed, cancer is treated by surgical resection, chemotherapy, radiation therapy, or a combination of these therapies. It is intuitive that physically and completely removing a solid tumor would be an effective treatment. A complete resection of the tumor mass, defined by surgical margins that are clear of neoplasia, is prognostic for a decreased chance of cancer recurrence and an increased survival rate. In practice, complete resection is difficult. A surgeon primarily has only their senses of touch and sight to provide "real-time" guidance in the removal of a tumor while in the operating room. Preoperative imaging can guide a surgeon to a tumor but does not give a continuous update of surgical progress. Intraoperative pathology is limited to a few slides worth of samples: a product of its time-consuming nature and the limited time a patient can remain under general anesthesia. Technologies to guide a surgeon in effecting complete resection of a tumor mass during the surgical procedure would greatly increase cancer survival rates by lowering rates of cancer recurrence; such a technology would also reduce the need for follow-up chemotherapy or radiation therapy. Here, we describe a prototype instrumentation system that can provide intraoperative guidance with exogenous optical contrast agents. The instrumentation combines interactive point excitation, local spectroscopy, and widefield fluorescence imaging to enable low-cost surgical guidance using FDA-approved fluorescent dyes, semiconductor quantum dots (QDs), or surface-enhanced Raman scattering (SERS) nanoparticles. The utility of this surgical system is demonstrated in rodent tumor models using an FDA-approved fluorescent dye, indocyanine green (ICG), and is then more extensively demonstrated with a pre-clinical study of spontaneous tumors in companion canines. The pre-clinical studies show a high sensitivity in detecting a variety of canine tumors with a low false positive rate, as verified by pathology. We also present a fundamental study on the behavior of quantum dots. QDs are a promising fluorophore for biological applications, including as a surgical contrast agent. To use QDs for in vivo human imaging, toxicity concerns must be addressed first. Although it is suspected that QDs may be toxic to an organism based on the heavy-metal elemental composition of QDs, overt organism toxicity is not seen in long-term animal model studies. We have found that some reactive oxygen species (ROS) generated by the host inflammatory response can rapidly degrade QDs; in the case of hypochlorous acid, optical changes to the QDs are suggestive of degradation occurring within seconds. It is well-known that QDs are sequestered by the immune system when used in vivo---we therefore believe that QD degradation through an inflammatory response may represent a realizable in vivo mechanism for QD degradation. We demonstrate in an in vitro cell culture model that immune cells can degrade QDs through ROS exposure. Knowledge of the degradative processes that QDs would be subject to when used in vivo informs on adaptations that can be made to the QDs to resist degradation. Such adaptations will be important in developing QD-based contrast agents for image guided surgery.