Fast time-domain diffuse correlation spectroscopy with superconducting nanowire single-photon detector: system...

Area of Science:

• Biomedical Optics
• Photonics
• Medical Imaging

Background:

• Time-domain diffuse correlation spectroscopy (TD-DCS) offers depth-resolved blood flow index (BFI) and optical property measurements.
• TD-DCS is photon-starved, especially with late photons, limiting in vivo applications.
• Superconducting nanowire single-photon detectors (SNSPDs) offer high quantum efficiency and low noise.

Purpose of the Study:

• To present a TD-DCS system utilizing an SNSPD.
• To compare SNSPD performance against standard single-photon avalanche diode (SPAD) detectors.
• To demonstrate fast in vivo TD-DCS measurements.

Main Methods:

• Developed a TD-DCS system incorporating an SNSPD.
• Characterized SNSPD performance (quantum efficiency, timing response, dark counts).
• Compared SNSPD-based TD-DCS with SPAD-based systems.
• Performed in vivo measurements on the adult human forehead.

Main Results:

• The SNSPD-based TD-DCS system achieved high performance.
• Fast in vivo measurements were successfully conducted.
• Gated pulsatile BFI was obtained from the adult human forehead.
• SNSPD demonstrated advantages over SPAD in this application.

Conclusions:

• SNSPD-based TD-DCS is a viable and improved technique for in vivo blood flow monitoring.
• This system overcomes previous photon-starved limitations of TD-DCS.
• Enables rapid, depth-resolved BFI measurements in humans.