Thermal transport simulation in healthy and arthritic fingers*

Infrared thermography can distinguish rheumatoid arthritic (RA) joints from healthy joints by measuring elevated skin surface temperature caused by the inflammation present in RA joints. However, infrared thermography is more sensitive for the assessment of small joints.
Thermal transport simulations of healthy and arthritic fingers were implemented by solving the bio-heat diffusion equation within joint models using finite elements method (FEM). FEM models were based on high resolution MR images. Arthritic joint models were simulated by increasing the metabolic heat generation of healthy joint models. Simulated thermographic images were compared to real images.
Our simulations confirmed that elevated internal joint temperature results in elevated surface temperature. Internal and surface temperature depended on internal heat generation, heat dissipation due to perfusion, joint geometry, and finger surface cooling. Patterns of finger surface temperature from simulation were similar to that in thermographic images.
Thermal transport simulations relate thermographic images of the finger, finger geometry, internal temperature distribution and internal heat sources or sinks. Understanding these relations facilitate better RA diagnostics with infrared thermography.