A Dual-Mode Near-Infrared Optical Probe and Monte Carlo Framework for Functional Monitoring of Rheumatoid Arthritis:...

Area of Science:

• Biomedical Optics
• Medical Imaging
• Rheumatology

Background:

• Current rheumatoid arthritis (RA) diagnostics like MRI and ultrasound are resource-intensive and focus on structural damage.
• There's a need for non-invasive, cost-effective methods for functional monitoring of joint inflammation in RA.

Purpose of the Study:

• To design and technically validate a low-cost, continuous-wave, near-infrared (NIR) dual-mode optical probe for RA functional monitoring.
• To assess the probe's ability to differentiate disease presence and severity by combining reflectance and transmission measurements.

Main Methods:

• Developed a dual-mode NIR optical probe utilizing reflectance and transmission geometries.
• Employed Monte Carlo (MC) simulations to model RA progression and optical signatures.
• Validated the system using physical phantoms and in vivo human volunteer measurements.

Main Results:

• Reflectance geometry effectively discriminates the onset of synovial turbidity (disease presence).
• Transmission flux serves as a quantitative measure of pannus volume (disease severity), consistent with the Beer-Lambert law.
• Identified 'metric inversion' in darker skin phenotypes, where epidermal absorption affects morphological metrics but not transmission flux.

Conclusions:

• The dual-mode NIR probe provides a potential pathway for longitudinal, quantitative monitoring of RA disease activity at the point of care.
• Transmission flux is a robust metric for grading RA severity across diverse skin tones.
• MC simulations are valuable for optimizing measurement geometry for specific clinical endpoints in RA diagnostics.