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

We developed a method to determine the temperature distribution of swine ao rtas with simulated atheromatous plaques in order to measure the temperatur e of atherosclerotic lesions. The inflammation associated with temperature elevation is considered to be one of the aggravating mechanisms of atherosc lerosis resulting in fissuring or rupture of atheromatous plaques. The temp erature 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 coeffici ent of human atheromatous plaques. The temperature distribution was calcula ted from measured temperature changes of the aortic intima under pulsed las er irradiation. The aorta was heated from the adventitial side with a halog en lamp to simulate the temperature elevation derived from inflammation. Th e temperature distribution of the aorta was obtained by solving the heat tr ansfer equation using the surface layer thickness (corresponding to the fib rous cap thickness). The surface layer thickness can be calculated using th e following working formula: D(mum) = 1363-398 Delta T-s+35 Delta T-s(2), w here Delta T-s denotes intimal surface temperature change under pulsed lase r irradiation. The calculated temperature of the ICG layer (corresponding t o the atheromatous core) correlated well with the measured temperature (r = 0.97, p< 0.0001).