Comparing the heating rate of the proximal phalanx of the fingers in rheumatoid arthritis and healthy subjects

Thermography is a non-invasive imaging technique that has been used for the assessment of rheumatoid arthritis (RA). The purpose of this research was to compare the heating rate of the proximal phalanx of the fingers and the whole palms in RA and that of healthy subjects. The study was conducted on 48 patients with high disease activity, hospitalised for RA, and 45 healthy subjects. The thermograms were taken with the FLIR camera E60bx. Subjects were instructed to immerse both hands up to the wrist in water thermostatically controlled at 0°C for 30 s. Then, the hands were pulled out of the water; the warm-up period was 180 s. Image pre-processing included: segmentation, extraction and anatomy identification. The mean value of the heating rate for whole palms and the proximal phalanx of the fingers in the RA group was lower than that in the control group (p < 0.05). This coincides with the uneven flow of the heat-transfer blood caused by the disease. However, the difference between the heating rates of the proximal phalanx of the fingers was greater than that of the entire hand. In addition, the proximal phalanx heating rates of the second, third and fourth fingers were higher than those of the outermost two fingers. The study may be used to develop clinical tools in the detection of abnormal heat signatures in the phalanx proximal of the fingers.