A proof-of-concept real-time fluorescence-lifetime-guided surgery imaging system

Description

Introduction

Fluorescence has emerged as a safe and real-time surgical guidance tool being regularly used for imaging blood perfusion, with many more applications such as tumor imaging in various stages of research and clinical translation. The spectral fluorescence imaging employed in current (pre-) clinical guidance systems faces limitations such as limited specificity and multiplexing, and background fluorescence. Fluorescence-lifetime imaging offers a potential solution to many current issues but is challenging because of the near-infrared and (sub-)nanosecond lifetime nature of the typical dyes used.

Methods

We propose a system, optimized for fluorescent dyes in the “800nm-channel” such as ICG and IRDye 800, consisting of our fast-gated CAPS camera1,2 and pulsed illumination from a supercontinuum LASER (NKT Photonics SuperK Fianium) providing 25 mW of illumination power in a 20 nm bandwidth centered around 780 nm to a flexible "pointer-style" illuminator, diffusing the light under a 20° scatter angle. The pointer can be moved far (larger illumination field) or close (larger illumination power density) to the object of interest to enable adequate results under variable conditions. The camera has an excitation block filter (NF785-33) and emission pass filter (FF01-835/70-25) in front of the lens. A time-domain multi-gate scheme is employed to resolve lifetimes under variable pointer distances.

Results/Discussion

We demonstrate realtime fluorescence lifetime imaging, in vitro and in vivo, of fluorescent dyes ICG and IRDye 800CW in clinically relevant concentrations in an open setup, exposed to lab room lights.
In normal imaging mode, the fluorescence lifetime is mapped to a typical rainbow color gradient and we are able to clearly distinguish both dyes even though they have a lifetime difference of only 200 ps. In a “high-contrast” mode we map the expected lifetimes of the two dyes to two contrasting colors to demonstrate the dye multiplexing potential.

Conclusions

We show that by using our CAPS camera, realtime NIR fluorescence lifetime imaging becomes a possibility. A pointer style illumination in combination with real-time multi-window lifetime analysis can make the high-speed pulsed illumination power requirements feasible.

Period	26 Aug 2020
Event title	EMIM 2020 - 15th European Molecular Imaging Meeting
Event type	Conference
Degree of Recognition	International