Reliability of Microwave Radiometry for the Assessment of Charcot Foot

Applying infrared thermometry for temperature measurement is recommended for Charcot neuro-osteoarthropathy (CNO) diagnosis and monitoring of its course. Microwave radiometry (MWR) is used for the detection of temperature changes in human tissues. This study evaluates the agreement between these two methods in CNO assessment. Individuals with diabetes mellitus (DM) with and without active CNO were included. MWR measurements were performed by a microwave computer-based system that detects microwave radiation from the area under investigation and temperatures of the internal tissues. Sensors with diameters of 0.8 cm (MWR 0.8), 2 cm (MWR 2), and 5 cm (MWR 5) were used, with larger diameters enabling deeper tissue assessment. Nine individuals (mean age: 54.6 ± 15.7, 2 females) with active CNO and 5 people with DM without CNO were included in the study. The agreement between temperatures measured by infrared thermometry and by MWR 0.8 was high and the average temperature discrepancy between the two methods was 0.034 °C (P = .676). The average temperature discrepancy between infrared thermometry and MWR 2 was -0.323 °C (P < .001) and between infrared thermometry and MWR 5 was -0.315 °C (P = .002). Participants with active CNO were followed-up for a median period of 67 [39, 79] weeks. During follow up, the difference in skin temperature between the affected and the contralateral foot was lower than 2 °C in 7 (77.8%) participants. Three out of 5 individuals had re-activation of CNO in 21, 22 and 65 weeks after the removal of the offloading device, respectively. The decision to gradually start loading would be different only for one person if we had used MWR instead of infrared thermometry for the measurement of temperature difference between the affected and the contralateral foot. In conclusion, infrared thermometry showed high agreement with MWR 0.8 but not with MWR 2 or MWR 5.