Towards next-generation time-domain diffuse optics for extreme depth penetration and sensitivity

Area of Science:

• Biomedical optics
• Medical imaging technologies
• Photonics

Background:

• Light-based non-invasive imaging is crucial for clinical applications like oncology and neurology, as well as molecular imaging and material quality assessment.
• Current diffuse optical imaging systems face limitations in depth penetration and contrast, hindering broader application.
• Continuous-wave (CW) systems are widely used but have inherent limitations in imaging depth and resolution.

Purpose of the Study:

• To demonstrate that time-domain (TD) diffuse optical imaging systems with picosecond time-gating can significantly outperform CW systems.
• To introduce a novel, compact source-detector module for parallelized dense coverage in optical imaging probes.
• To highlight the potential for enhanced performance, new applications, and cost-effective, miniaturized devices for widespread use.

Main Methods:

• Implementation of a time-domain system utilizing picosecond time-gating and a dense source-detector distribution.
• Development of an integrated source-detector pair featuring a pulsed Vertical-Cavity Surface-Emitting Laser (VCSEL) and a Silicon Photomultiplier (SiPM) with Single-Photon Avalanche Diode (SPAD) detection.
• Experimental validation of enhanced depth penetration and contrast compared to ideal continuous-wave systems.

Main Results:

• Achieved more than a 2-fold increase in depth penetration compared to continuous-wave systems.
• Demonstrated many decades higher contrast in diffuse optical imaging.
• Successfully integrated a pulsed VCSEL, SiPM, and SPAD into a compact probe building block.

Conclusions:

• Time-domain diffuse optical imaging with picosecond time-gating and dense arrays offers superior performance over continuous-wave systems.
• The developed integrated source-detector module enables parallelization and dense coverage, paving the way for advanced imaging devices.
• This technology promises significant advancements in medical diagnostics, molecular imaging, and wearable quantitative imaging solutions.