Design of multiphoton microendoscope system for minimally invasive detection of cancer

Early detection of cancer is crucial for improving patient survival. High resolution optical imaging is ideal to image cellular abnormalities indicative of early cancer. For tissues located deep within the body, such as the pancreato-biliary ducts, high resolution imaging must be implemented endoscopically due to the limited penetration depth of light. We are developing a minimally invasive high numerical aperture (HNA) microendoscope system capable of simultaneous co-registered multiphoton imaging (two-photon excited fluorescence, second harmonic generation, three-photon excited fluorescence, and third harmonic generation) of small diameter ductal tissues, such as the pancreato-biliary ducts. Imaging of the epithelial layer is achieved via helical scanning of the 1.5 mm diameter endoscope with a fixed focus. The endoscope distal end optics act as both the illumination and collection mechanism, with the core of the dual clad fiber (DCF) carrying femtosecond laser excitation light, and the inner cladding of the DCF carrying multiphoton emission. Designing HNA optics at the 1 mm diameter size scale is challenging, time consuming, and may be expensive. To complete development of the proximal components of the system, we designed a low numerical aperture (LNA) reflectance & single photon fluorescence system using low cost off the shelf optical components to aid in the development of software and the testing of proximal system hardware components. Additionally, rapid, low-cost design and fabrication of HNA optics with 3D printing is presented.