Infrared thermography and dual-layer spectral CT for the detection of femoral vascular compromise: an experimental large animal study

BACKGROUND: Rapid identification of vascular compromise remains a clinical challenge in the acute trauma setting. Conventional diagnostic tools such as CT angiography (CTA) and Doppler-ultrasound might provide decent anatomical and functional assessment. However, they are limited by ionizing radiation, contrast exposure or time requirements. Although not validated, infrared thermography (IRT) might offer a non-invasive alternative capable of detecting surface temperature asymmetries that may reflect underlying perfusion deficits. This study aimed to evaluate the feasibility of thermographic imaging in detecting vascular lesions. METHODS: As part of a porcine polytrauma model (n = 28), vascular lesion of the right femoral artery was defined as a ≥ 50% diameter reduction on CTA. Temperature differences between both extremities were measured using infrared thermography. SDCT based iodine concentrations distal to the stenosis were quantified to assess perfusion changes. Correlation and regression analyses were performed between stenosis degree, temperature difference, and tissue iodine uptake. RESULTS: Six animals fulfilled the criteria for relevant vascular compromise. This resulted in a mean vessel diameter reduction behind the lesion of 68% ±18%. The vascular lesion group demonstrated a mean inter-limb temperature difference of 6.93 °C ± 1.78 °C compared to 0.71 °C ± 1.27 °C in the non-lesion group (p < 0.001). A strong positive correlation was found between diameter-based stenosis and temperature difference (r = 0.785, p < 0.001), as well as between diameter reduction and iodine uptake (r = 0.801, p < 0.001). ROC analysis of temperature difference for detecting vascular lesion yielded an AUC of 0.992 (95% CI 0.970-1.000, p < 0.001) with 100% sensitivity and 95.2% specificity at a 3 °C threshold. CONCLUSION: Thermographic temperature differences showed excellent diagnostic performance in detecting an acute vascular lesion in a large animal model. The strong correlation between SDCT iodine uptake and both anatomical stenosis and surface temperature suggests that iodine concentration is a valid quantitative surrogate for perfusion. In conclusion, infrared thermography might represent a viable alternative for detection of acute vascular occlusion.