Study of the Monte-Carlo model based on the measurement of irradiance distribution in myocardium from interventional devices in photodynamic therapy

We studied the Monte-Carlo model based on the measurement of the irradiance distribution of 663 nm light in porcine myocardium emitted from interventional devices in photodynamic therapy to investigate the treatment region by a photosensitization reaction. The optical properties of myocardium tissue vary with portion of heart. Since blood content makes mainly this variation, extracted fresh myocardium with blood content was used for the measurement of the irradiance distribution. The irradiance distribution in the porcine left ventricle 3-4 hours passed after the extraction was measured at 1-5 mm in vertical direction, at 0-5 mm in horizontal direction through the thin optical fiber with high NA during the irradiation from the interventional devices in photodynamic therapy. The calculated irradiance distribution in Monte-Carlo model was matched with the measured irradiance distribution by changing the scattering coefficient and the anisotropic parameter under the constant absorption coefficient of the myocardium. The light powers in the measured and the calculated irradiance distribution were approximated with exponential function fitted by least-squares method, and both exponents were compared each other. The treatment region was estimated using the Monte-Carlo model and a published cell lethality measurement data. The estimated treatment region approximately matched to the previous result of a dog experiment.