Determining the temperature distribution of swine aorta with simulated atheromatous plaque under pulsed laser irradiation: an experimental attempt to detect the vulnerability of atherosclerosis

Abstract

We developed a method to determine the temperature distribution of swine aortas with simulated atheromatous plaques in order to measure the temperature of atherosclerotic lesions. The inflammation associated with temperature elevation is considered to be one of the aggravating mechanisms of atherosclerosis resulting in fissuring or rupture of atheromatous plaques. The temperature distribution of plaques covered by fibrous caps cannot be measured by conventional thermistors. Indocyanine green (ICG) solution was injected into the subintima of swine aorta to simulate the light absorption coefficient of human atheromatous plaques. The temperature distribution was calculated from measured temperature changes of the aortic intima under pulsed laser irradiation. The aorta was heated from the adventitial side with a halogen lamp to simulate the temperature elevation derived from inflammation. The temperature distribution of the aorta was obtained by solving the heat transfer equation using the surface layer thickness (corresponding to the fibrous cap thickness). The surface layer thickness can be calculated using the following working formula: D( µm)=1363-398 &#150 T +35 &#150 T 2, where s s &#150 T s denotes intimal surface temperature change under pulsed laser irradiation. The calculated temperature of the ICG layer (corresponding to the atheromatous core) correlated well with the measured temperature (r=0.97, p<0.0001).