Application—Infrared Thermal Imaging Can Replace Ultrasound for Manual Wrist Inspection

Infrared Thermal Imaging Can Replace Ultrasound for Manual Wrist Inspection

   At present, arthritis detection by physical examination is the standard practice for monitoring arthritis in juvenile idiopathic arthritis (JIA) patients. However, arthritis assessments in children, including warmth, limitation of movement, swelling, and pain, are difficult and not entirely reliable when compared to adults. Recently, ultrasound (US), which can demonstrate structural abnormalities and synovial vascularity in joints, has been shown as an appropriate tool for monitoring joint inflammation. However, US is time consuming and operator-dependent in that it requires a physician with expertise. Currently, no validated US criteria exist for arthritis detection in children. The most useful parameters for arthritis detection between Gray scale ultrasound (GSUS) or Power Doppler ultrasound (PDUS) remain unclear. In general, US is indicated for clinically suspected arthritis with an uncertain physical examination; however, abnormal US may present in JIA patients with clinical remission as well.

   Infrared thermography (IRT), a non-invasive and radiation-free imaging method, has been used in research medicine to detect temperature changes in tissue abnormalities beneath the skin or on the skin’s surface in specific areas. Over the last decade, IRT has been developed from a large instrument to a small handheld unit, which is more practical for clinical use. In addition, IRT has been shown by many studies as a method of arthritis detection. Previous studies have shown that IRT is mostly used in rheumatoid arthritis (RA), but the role of IRT in detecting joint inflammation of JIA patients, especially wrist arthritis, is still unknown. Correlations between joint inflammation and parameters of the IRT, including thermographic index (TI), heat distribution index (HDI), mean and maximum temperature have also been reported. Some studies demonstrated changes in thermal patterns of skin temperature in the area of joint inflammation. Therefore, IRT is a promising tool for arthritis detection in the future, especially in patients with uncertain joint examination. However, IRT was shown to detect inflammation in large joints better than in small joints of the hand in RA patients. Both IRT and US could be useful in detecting arthritis in JIA. Therefore, this study focused on using IRT and US to detect varying degrees of wrist joint inflammation and comparison between IRT and US with physical examination in JIA patients.

Figure 1. Infrared thermography of the wrist.

   Of 46 JIA patients, 16 had previous wrist arthritis but currently inactive, 30 still had wrist arthritis, and the median ages (IQR) were 7.7 (4.3) and 10.2 (4.8) years respectively. Fifteen healthy participants were included, with a median age (IQR) of 9.2 (2.0) years. Using IRT, mean temperature (Tmean) and maximum temperature (Tmax) at skin surface in the region of interest (ROI) in the arthritis group were higher than in the inactive group and the healthy controls with p < 0.05. When patients with arthritis were subgroup analyzed by disease severity based on physical examination, the moderate to severe arthritis had Tmean and Tmax higher than the mild arthritis group with statistical significance. The Heat Distribution Index (HDI), two standard deviations of all pixel temperature values in the ROI, in the moderate to severe arthritis group was higher than in the healthy controls (p = 0.027). The receiver operating characteristic analysis in arthritis detection revealed diagnostic sensitivity of 85.7% and 71.4% and specificity of 80.0% and 93.3% at a cut-off points of Tmean ≥ 31.0 °C and Tmax ≥ 32.3 °C respectively. For US, GSUS and PDUS are useful in detecting arthritis, providing high sensitivity (83.3%) and specificity (81.3%). 

   IRT is a potential method for wrist arthritis assessment in JIA patients. IRT parameters, including Tmean and Tmax, could be used to differentiate arthritis from inactive. In moderate to severe artritis, a cut-off point of Tmean ≥ 31.0 °C and Tmax ≥ 32.3 °C for arthritis detection had sensitivity and specificity of 85.7%, 80.0% and 71.4%, 93.3% respectively. Our study demonstrated that both IRT and US were applicable tools for detecting wrist arthritis.

Reference

Butsabong Lerkvaleekul, Suphaneewan Jaovisidha, Witaya Sungkarat, et al. The Comparisons between Thermography and Ultrasonography with Physical Examination for Wrist Joint Assessment in Juvenile Idiopathic Arthritis. Institute of Physics and Engineering in Medicine. 2017.