First In Vivo Application of Microwave Radiometry in Human Carotids: A New Noninvasive Method for Detection of Local Inflammatory Activation

Abstract

This study investigated whether temperature differences: 1) can be measured in vivo noninvasively by microwave radiometry (MR); and 2) are associated with ultrasound and histological findings. Studies of human carotid artery samples showed increased heat production. MR allows in vivo noninvasive measurement of internal temperature of tissues. Thirty-four patients undergoing carotid endarterectomy underwent screening of carotid atherosclerosis by ultrasound and MR. Healthy volunteers were enrolled as a control group. During ultrasound study, plaque texture, plaque surface, and plaque echogenicity were analyzed. Temperature difference (ΔT) was assigned as maximal minus minimum temperature. Association of thermographic with ultrasound and histological findings was performed. ΔT was higher in atherosclerotic carotid arteries compared with the carotid arteries of controls (p < 0.01). Fatty plaques had higher ΔT compared with mixed and calcified (p < 0.01) plaques. Plaques with ulcerated surface had higher ΔT compared with plaques with irregular and regular surface (p < 0.01). Heterogeneous plaques had higher ΔT compared with homogenous (p < 0.01). Specimens with thin fibrous cap and intense expression of CD3, CD68, and vascular endothelial growth factor (VEGF) had higher ΔT compared with specimens with thick cap and low expression of CD3, CD68, and VEGF (p < 0.01). MR provides in vivo noninvasive temperature measurements of carotid plaques, reflecting plaque inflammatory activation.