Compact solid-state CMOS single-photon detector array for in vivo NIR fluorescence lifetime oncology measurements

Area of Science:

• Biomedical Optics
• Surgical Oncology
• Medical Imaging

Background:

• Distinguishing cancerous from healthy tissue in near-infrared fluorescence-guided surgery remains a challenge.
• Analyzing the lifetime of exogenous fluorophores, typically in the sub-nanosecond range, offers a promising solution.

Purpose of the Study:

• To develop and validate a compact, time-gated measurement system (FluoCam) for in vivo fluorescence lifetime imaging.
• To assess the feasibility of using FluoCam for distinguishing tissue types based on fluorophore lifetime differences.

Main Methods:

• Integration of a single-photon pixel array (CMOS SPADs) into a compact, time-gated system named FluoCam.
• In vivo measurements using indocyanine green (ICG)-modified derivatives targeting αvβ 3 integrin in mouse models (melanoma and glioblastoma xenografts).
• Measurements conducted on tumor, muscle, and tail tissues to evaluate system performance under realistic conditions.

Main Results:

• Demonstrated the feasibility of in vivo fluorescence lifetime measurements using the FluoCam system.
• Determined characteristic lifetimes of ICG-modified fluorophores (around 500 ps).
• Detected subtle lifetime differences (approximately 10%) between bound and unbound fluorophores, crucial for tissue differentiation.

Conclusions:

• The FluoCam system enables in vivo fluorescence lifetime measurements for surgical oncology.
• Fluorescence lifetime analysis provides a viable method for enhancing the discrimination between healthy and cancerous tissues.
• The system's ability to detect small lifetime variations holds significant potential for improving surgical guidance.