A novel use of combined thermal and ultrasound imaging in detecting joint inflammation in rheumatoid arthritis.

Purpose: To evaluate the use of combined thermal and ultrasound imaging to assess joint inflammation in rheumatoid arthritis (RA).

Method: 22-joint (bilateral hands) thermography and ultrasonography were performed. For each patient, the MAX, MIN and AVG represent the sum of the temperature differences with a control temperature, for the respective maximum (Tmax), minimum (Tmin) and average (Tavg) temperatures at the joints. MAX (PD), MIN (PD) and AVG (PD) represent the results of combined thermal imaging with a patient's total ultrasound power Doppler (PD) joint inflammation score (Total PD) (when Total PD > median score, MAX, MIN and AVG was multiplied by a factor of 2, otherwise MAX (PD), MIN (PD) and AVG (PD) remained the same as the MAX, MIN and AVG). Pearson correlation and linear regression were used to assess correlation and characterize relationships of imaging parameters with the 28-joint disease activity score (DAS28).

Results: In this cross-sectional study, 814 joints were examined in 37 adult RA patients (75.7 % female, 75.7 % Chinese; mean DAS28, 4.43). Among the imaging parameters, only MAX (PD) and AVG (PD) correlated significantly with DAS28 (correlation coefficient (95 % CI): MAX (PD), 0.393 (0.079, 0.636), P = 0.016; AVG (PD): 0.376 (0.060, 0.624), P = 0.022). Similarly, only MAX (PD) and AVG (PD) demonstrated a statistically significant relationship with DAS28 (regression coefficient (95 % CI): MAX (PD), 0.009 (0.002, 0.015), P = 0.016; AVG (PD), 0.011 (0.002, 0.020), P = 0.022).

Conclusions: Novel use of combined thermal and ultrasound imaging in RA shows superiority to either imaging alone in terms of correlation with DAS28.