Absorption characteristics evaluation from pulsed photo-thermal radiometry in the determination of lung air-leak integrity by vital staining

We evaluated the absorption characteristics of the lung surface with vital staining non-invasively by means of pulsed photo thermal radiometry (PPTR) to improve the success rate of laser air leak sealing from the lung. To seal the air leak after lung resection, we investigated laser treatment using diode laser irradiation (wavelength: 810nm) and vital staining with Indocyanine green (ICG, absorption peak wavelength: 805nm). We used μ_a√α and defined as A (μ_a: the absorption coefficient, α: the thermal diffusivity) in the approximate PPTR theory to analyze the PPTR signal as it was assumed the thermal diffusivity coefficient would be a constant when the lung collapsed during surgery. The accuracy of the constructed PPTR system with this assumption was A=±0.15s^-1/2. In ex vivo studies, the measured A variation due to vital staining was 3.7s^-1/2. This range was sufficiently large measured against the accuracy. We monitored the condition of the lung surface during continuous diode laser irradiation with our PPTR system. We successfully measured the absorption characteristic changes during laser irradiation. We believe this constructed PPTR system might be useful in improving the success rate of laser sealing with vital staining while arranging the laser energy by the value of A.