METHODS AND RESULTS: In a total of 35 canines, we applied a
laser directly to the epicardium of the beating heart during open-chest surgery at 15 min after administration of a
photosensitizer,
talaporfin sodium. We evaluated the lesion size (depth and width) using
hematoxylin-
eosin staining under varying conditions as follows:
laser output (5, 10, 20 W/cm(2)), irradiation time (0-60 s),
photosensitizer concentration (0, 2.5, 5 mg/kg), blood
oxygen concentration (103.5 ± 2.1 vs. 548.0 ± 18.4 torr), and contact force applied during irradiations (low: <20 g, high: >20 g). A
laser irradiation at 20 W/cm(2) for 60 s under 5 mg/kg (29 µg/mL) of
photosensitizer induced a lesion 8.7 ± 0.8 mm deep and 5.2 ± 0.2 mm wide. The lesion size was thus positively correlated to the
laser power, irradiation time, and
photosensitizer concentration, and was independent of the applied contact force and
oxygen concentration. In addition, the concentration of the
photosensitizer strongly correlated with the changes in the pulse oximetry data and fluorescence of the backscattering
laser, suggesting that a clinically appropriate condition could be estimated in real time.
CONCLUSION: