Multi-center feasibility study of microwave radiometry thermometry for non-invasive differential diagnosis of arterial disease in diabetic patients with suspected critical limb ischemia.

Aims: Diagnosis of vascular involvement in diabetic foot ulceration (DFU) remains challenging. We conducted a proof of concept study to investigate the feasibility of microwave radiometry (MWR) thermometry for non-invasive differential diagnosis of critical limb ischemia (CLI) in subjects with DFU.

Methods: This prospective, multi-center, study included 80 participants, divided into four groups (group N: normal control subjects; group DN: participants with diabetes and verified neuropathic ulcers without vascular involvement; group DC: participants with diabetes and CLI and group NDC: participants with CLI without diabetes). Vascular disease was confirmed with angiography. All patients underwent MWR (RTM-01-RES:University of Bolton, UK) to record mean tissue temperatures at various pre-determined foot sites. Comparisons of temperature measurements between study groups were performed using one-way ANOVA and Dunn tests. ROC analysis was performed to determine sensitivity, specificity and cut-off value of MWR for CLI diagnosis.

Results: Temperatures recorded in vicinity to the foot ulcers of participants with diabetes and CLI were similar to those with CLI without diabetes, but significantly lower than in subjects with neuropathic ulcers without vascular involvement and normal controls (group DC:29.30°C±1.89 vs. group NDC:29.18°C±1.78vs. group N:33.01°C±0.45 vs. group DN:33.39°C±1.37;P<.0001). According to ROC analysis, cut-off temperature value to diagnose CLI was <31.8°C (area under the curve: 0.984; 95% CI: 0.965-1.005;P<.001), with a sensitivity of 100.0% (95%CI: 90.26-100.0) and specificity of 88.37% (95% CI: 74.92-96.11).

Conclusions: Tissue temperatures in vicinity to ulcers were significantly lower in participants with CLI, with or without diabetes, compared to non-ischemic controls. MWR could be used for differential diagnosis of arterial ischemia in subjects with DFU.