Author ORCID Identifier:

https://orcid.org/0000-0003-2301-2090

Date of Graduation

8-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Biomedical Engineering

Advisor/Mentor

Rajaram, Narasimhan

Committee Member

Jensen, Hanna

Second Committee Member

Wolchok, Jeffery

Keywords

Diffuse Reflectance; Infection; Lookup Table; Monte Carlo; Optics; Synovial Fluid

Abstract

Septic arthritis is a severe joint infection that can rapidly destroy cartilage and cause lifelong disability if not diagnosed and treated promptly. Faster, bedside diagnostic tools are needed to reduce delays and support timely treatment decisions while preserving standard laboratory workflows. A syringe-mounted diffuse reflectance spectroscopy (DRS) system was developed for rapid, sterile, point-of-care measurement of synovial fluid optical properties. Broadband light (400–650 nm) was delivered and collected through the syringe barrel without contaminating the sample. An empirical lookup table (LUT) and a boundary-aware Monte Carlo (MC) model were implemented to extract absorption (μₐ) and reduced scattering (μs′) coefficients from the measured spectra. Optical phantom studies confirmed that the system retrieves optical properties within 5–15% of known reference values and achieves signal-to-noise ratios exceeding 50 dB. Prospective patient samples (n = 19) demonstrated that scattering amplitude and reflectance band ratios (e.g., R₄₉₀/R₆₀₀) distinguish infected from non-infected fluid with ≥85% sensitivity and ≥90% specificity in under five minutes. The non-contact design preserves fluid sterility for culture confirmation. This work demonstrates a practical path from proof-of-concept to deployable point-of-care optical screening for septic arthritis, supporting faster treatment decisions and improved patient outcomes.

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