Wearable frequency-domain near-infrared spectroscopy (FD-NIRS) system.

Area of Science:

• Biomedical Optics
• Wearable Technology
• Spectroscopy

Background:

• Frequency-domain near-infrared spectroscopy (FD-NIRS) is a noninvasive technique for quantifying tissue composition and metabolism.
• Current FD-NIRS instrumentation is often large and complex, limiting its use to research settings.
• There is a need for portable FD-NIRS systems for continuous monitoring in naturalistic environments.

Purpose of the Study:

• To develop a novel, real-time, multi-frequency wearable FD-NIRS system.
• To miniaturize FD-NIRS technology for broader applications in health monitoring.
• To demonstrate the feasibility of quantitative FD-NIRS for wearable applications.

Main Methods:

• Developed a wearable FD-NIRS system using a custom application-specific integrated circuit (ASIC).
• Integrated 685 nm and 850 nm laser diodes and a silicon photomultiplier (SiPM) detector.
• Evaluated system accuracy using tissue-simulating phantoms and demonstrated proof-of-concept with forearm occlusion measurements.

Main Results:

• Achieved high accuracy for optical properties (absorption: 0.0007 mm⁻¹, reduced scattering: 0.08 mm⁻¹) at a 14.7 Hz measurement rate.
• The wearable device is compact (7x3x3 cm) and lightweight (37g without battery).
• Demonstrated real-time measurement capabilities up to 1 kHz at single frequencies.

Conclusions:

• The developed wearable FD-NIRS system is feasible for quantitative tissue optical spectroscopy.
• This technology can expand FD-NIRS applications into continuous monitoring and naturalistic environments.
• The system represents a significant advancement for wearable health monitoring.