1970: Comparison of Optical Imaging with Musculoskeletal Ultrasound in Assessment of PIP Joints of Systemic Lupus Erythematosus Patients

Background/Purpose: Lupus arthritis has heterogeneous phenotypes and severity, complicating clinical management and trial endpoints. Advances in musculoskeletal ultrasound (MSK US) and optical imaging have been proposed as objective assessment tools. In a prior study of 20 systemic lupus erythematosus (SLE) patients, we demonstrated that frequency-domain optical imaging (FDOI) and a glove-like optical imaging system (GLOIS) can differentiate inflamed from normal joints by measuring transmitted and reflected lights to assess changes in tissue properties. Here we present extended data comparing FDOI with MSK US in evaluating lupus arthritis, and exploratory findings using GLOIS to monitor arthritis resolution.

Methods: We evaluated 31 SLE patients and 22 healthy controls via convenience sampling. For each subject, 8 proximal interphalangeal (PIP) joints (bilateral PIPs 2–5) were evaluated by FDOI and MSK US within two hours. MSK US used multiplanar grey-scale (GS) and power Doppler (PD) imaging, scored by OMERACT definitions to generate a composite PDGS score. FDOI employed a 670 nm, 8 mW laser modulated at 300 MHz, and scanned across each PIP to reconstruct three-dimensional (3D) maps of light absorption and scattering. Additionally, 2 SLE patients and 2 healthy controls underwent GLOIS evaluation (Fig 1), and 1 SLE patient was evaluated by GLOIS before and after therapy for an arthritis flare. GLOIS (Fig 1) used flexible bands with 8 optical modules (each with a photodiode and 3 LEDs at 530, 660, and 880 nm). LEDs were sequentially activated; photodiodes captured the transmitted signals. A sphygmomanometer was inflated to the subject’s diastolic blood pressure, inducing a complete venous occlusion and partial arterial occlusion, then released after 60 seconds accompanied by 60 more seconds of measurement. Subsequently, the measurements from all the source/detector pairs around the finger joint were used to tomographically reconstruct the distributions of total hemoglobin (HbT) concentrations in the joint.

Results: FDOI data (Fig 2) from 235 PIPs (SLE) and 136 PIPs (controls) produced an AUC of 0.87, with 89% sensitivity and 66% specificity (Fig 2A, 2B). Among 120 joints assessed by MSK US, PDGS scores were 0 (n=47), 1 (n=73), 2 (n=61), and 3 (n=54). Joints with moderate/severe arthritis (PDGS 2–3) had significantly higher scattering (8.8±1.4 vs. 8.3±0.6/cm, p< 0.01, Fig 2C) and absorption coefficients (0.25±0.18 vs. 0.18±0.1/cm, p< 0.01, Fig 2D) than those with minimal/no inflammation (PDGS 0–1).

3D tomographically reconstructed GLOIS imaging showed higher HbT concentration at pressure release (Fig 3A) and 30 seconds post-release (Fig 3B) in SLE joints (42 μM at both timepoints) with PDGS of 2 compared to controls (29 and 30 μM). In the SLE patient examined at the time of flare (T1) and after symptom resolution (T2), Fall Time AUC decreased in 4 of 6 fingers (Fig 3C), suggesting improvement.

Conclusion: These data support the use of FDOI and GLOIS to reliably detect MSK US-confirmed arthritis in SLE joints and to monitor disease activity. Optical imaging shows promise as a non-invasive, objective tool for lupus arthritis assessment in clinical care and trials. Further development is warranted and ongoing.