High-speed handheld multiphoton multifoci microscopy

Abstract

For the last decade, multiphoton excitation fluorescence microscopy has found numerous applications in biology. Multiphoton microscopy provides several advantages over conventional fluorescence microscopy, including increased penetration depth, improved signal-to-background ratio, and reduced photodamage. Despite its suitability for tissue imaging, multiphoton microscopy has not been used for in-vivo clinical applications due to its lack of portability and its slow imaging speed. Multiphoton microscopy has recently been improved with the development of high speed imaging systems and handheld devices. High speed imaging has been achieved by simultaneously exciting multiple foci in the specimen, known as multiphoton multifocal microscopy (MMM). Compact devices have been developed by combining fiber optic delivery and miniaturized scanning devices. We have developed a handheld device for high speed multiphoton microscopy based on optical fiber delivery, multifoci excitation/detection and a novel scanner. Our system is designed to be sufficiently compact such that it can be used for in vivo clinical imaging, or optical biopsy with potential applications in dermal, cervical and colorectal cancer diagnosis. The power available from a typical Ti:sapphire laser is fully utilized by using multifoci excitation; this results in reduced image acquisition time. Femto-second pulses from a Ti:sapphire laser are delivered to our system through conventional optical fiber. We realize multifoci excitation with a microlens array, and multifoci detection with a multi-anode PMT. A high bandwidth tip tilt mirror is further used as the scanning element for high speed imaging. The feasibility of this handheld MMM is demonstrated by measuring the performance of major components individually. This work is supported by NIH R33 CA091354.