Non invasive assesment of vulnerable plaque using microwave radiometry

Abstract

Heat generation is one of the functional characteristics of vulnerable plaque,which is defined as the atherosclerotic plaque that is prone to rupture and cause a acute coronary syndrome.Intravascular thermography is the only method can be used in vivo to measure heat generation from atherosclerotic plaques.Microwave radiometry is a new non-invasive method for measuring temperature from internal tissues at microwave frequencies .We investigated whether thermal heterogeneity measured by Microwave Radiometry is correlated with Intravascular thermography and with histological findings in a experimental atheromatic model. Twenty four rabbits were randomized to normal (n=12) or cholesterol-rich diet (n=12) for 6 months. Thereafter, temperature measurements of the abdominal aortas were performed 1) invasively with IVT and 2) non-invasively with MR. All aortas were divided by optical coherence tomography in 5 segments. For both techniques temperature difference (ΔT) of each segment was assigned as the temperature of each segment minus the minimal temperature of the 5 segments. Both MR and IVT detected that ΔT of atherosclerotic aortas were significantly higher compared to controls (MR:1.02±0.23°C versus 0.21±0.09°C, p<0.001, IVT:0.19±0.03°C versus 0.01±0.01°C, p<0.001). ΔΤ detected by the two methods correlated positively (p<0.001). ΔΤ measured by MR correlated with inflammatory cell density CD3 and CD68 immunoreactivity (p<0.05). The results of the current study justify the clinical application of MR for the non-invasive detection of the inflammatory activation in atherosclerotic plaques