Handheld wide-field fluorescence lifetime imaging system based on a distally mounted SPAD array.

Area of Science:

• Biomedical Optics
• Instrumentation
• Microscopy

Background:

• Fluorescence Lifetime Imaging (FLIM) is a powerful technique for biological and biomedical analysis.
• Existing FLIM systems often rely on fiber optics to relay signals, limiting miniaturization and handheld capabilities.
• There is a need for compact, portable FLIM systems for ex vivo and potentially in vivo applications.

Purpose of the Study:

• To demonstrate a novel handheld FLIM system with a distally mounted single photon avalanche diode (SPAD) array.
• To assess the system's suitability for ex vivo applications in biological and biomedical contexts.
• To evaluate the potential for developing a miniaturized, chip-on-tip FLIM endoscopy system.

Main Methods:

• Development of a handheld FLIM system featuring a <2 mm² 128×120 SPAD array at the distal end.
• Operation of the system via a >1 m wired interface with a compact head (∼4.5cm³).
• Application of the system for imaging ovine kidney tissue and plant leaves, and recording FLIM videos.

Main Results:

• Successful demonstration of a handheld FLIM system with a distally mounted SPAD array.
• Achieved frame rates exceeding 1 Hz, enabling FLIM video acquisition.
• Demonstrated contrast imaging between different tissue compositions and between healthy and stressed plant leaves.

Conclusions:

• The developed handheld FLIM system represents a significant advancement, being the first of its kind with a distal SPAD array.
• The system shows promise for ex vivo analysis and is a crucial step towards miniaturized in vivo FLIM endoscopy.
• The compact design and high frame rates open new possibilities for handheld biomedical imaging.