Laser-Induced Fluorescence (LIF) for rapid Cancer diagonosis
An optical diagnostic procedure based on laser‑induced fluorescence (LIF) has been developed for direct in‑vivo cancer diagnosis without requiring biopsy. Endogenous fluorescence of normal and malignant tissues were measured directly using a fiberoptic probe inserted through an endoscope. A nitrogen dye laser tuned to 410 nm was used as the excitation source. The fiberoptic probe was inserted into the biopsy channel of an endoscope and lightly touched the surface of the tissue being monitored. Each measurement was completed in approximately 0.6 second for each tissue site. We have developed a technique using the differential normalized fluorescence (DNF) to enhance small but consistent spectral differences between the normal and malignant tissues. This technique greatly improves the accuracy of diagnosis for malignant tissue. The LIF methodology has been applied in a clinical study involving over 200 patients in order to differentiate normal tissue from malignant tumors of the esophagus. The results of this DNF approach were compared with histopathology results of the biopsy samples and indicated excellent agreement in the classification of normal tissue and malignant tumors with 98% sensitivity. The effect of inflammation on the diagnosis was also investigated.
Advanced techniques such as synchronous fluorescence and time-resolved detection are currently being developed to further improve the optical diagnostic method. These techniques are aimed at developing an improved and novel system to diagnose esophageal cancer and high-grade dysplasia as well as low-grade dysplasia in Barrett’s esophagus. A technical innovation of this project is the development of a unique real-time synchronous luminescence (SL) monitor for detecting small differences in fluorescence profiles of tissues. Molecular fluorescence is a sensitive technique that can be used to measure endogenous fluorescence spectra of biological samples. However, fixed-excitation fluorescence spectra tend to be similar for normal and dysplastic tissues. A methodology that is capable of improving the specificity of the fluorescence technique is the synchronous scanning method, often referred to SL. The proposed SL monitor could lead to significant advances in rapid and effective detection of cancer and dysplasia of the esophagus.