? Fluorescence imaging offers excellent sensitivity that is unparalleled by any other optical imaging techniques. It has thus been one of the most powerful tools in biomedical applications. The drawback of fluorescence intensity imaging, however, is the low information content and a lack of chemical specificity. This project aims to develop a novel technique, spectrally-resolved fluorescence correlation spectroscopy (FCS), for biomedical imaging. In this new imaging method, fluorescence response to an external field is collected at a range of wavelengths. Time correlation function is evaluated between wavelengths to yield a two-dimensional fluorescence correlation spectrum for each spatial location in an image. By coupling spectral and time resolution, spectrally-resolved FCS greatly enhances the information content and thus provides (1) high contrast in diagnostic imaging and (2) detailed information on the physicochemical environments of the fluorescent probe. The high contrast of spectrally-resolved fluorescence correlation imaging is applied to a model system of cancer diagnosis. Cancers are the second leading cause of death in the United States, accounting for 25% of the total fatalities. The key to timely treatment of cancers and improved survival rate is early diagnosis. We plan to use the new method to examine tissue samples in various pathological conditions, from healthy, hyperplastic, adenomatous to adenocarcenomatous. Spectroscopic measurements of tissue samples collected in surgery and biopsy procedures are conducted in vitro. Spectral libraries are established for normal and cancerous tissue through fiber optical examination of tissue samples. Computer programs are written for data treatment and statistical analysis of the library spectra. Various decision parameters are explored to establish the best diagnostic criteria. Coupling both spectral and temporal resolution of fluorescence, the new method provides significantly improved contrast between the normal and cancerous tissues compared to the existing method of steady-state fluorescence spectroscopy. With the enhanced contrast, spectrally-resolved fluorescence correlation imaging holds excellent potential in noninvasive diagnosis of cancers. ? ?
