Abstract
Objective: To explore the indicative effects of indocyanine green-near-infrared fluorescence imaging (ICG-NIFI) in the thickness of necrotic dermal tissue in porcine burn wounds. Methods: This study was a medical-engineering interdisciplinary basic research. One 3-month-old male Bama miniature pig was selected, and circular burn wounds with a diameter of 2 cm were created by applying a scalding instrument with inflicting temperature of 75 ℃ to the skin on the dorsal side of the pig for 3, 7, and 11 seconds, respectively, with two wounds for each duration of injury. The fluorescence intensity of the regions of interest in the wounds and the surrounding normal skin was detected by ICG-NIFI technology within 700 seconds after injecting indocyanine green (hereinafter referred to as after administration). The trend of the normalized fluorescence intensity was observed, and the time when the fluorescence intensity of the regions of interest in the wounds and the surrounding normal skin reached the peak (hereinafter referred to as the peak time) was determined. Additional two 3-month-old male Bama miniature pigs were selected, and circular burn wounds with a diameter of 2 cm were created on the skin of bilateral thoracic walls by applying a scalding instrument with inflicting temperature of 75 ℃ for 5, 7, 9, 11, 13, 15, 17, and 19 seconds, respectively, with 4 wounds for each duration of injury. The blood flow intensity of the regions of interest in the wounds was detected by laser speckle contrast imaging technology; the relative fluorescence intensity of the regions of interest in the wounds was detected by ICG-NIFI technology at the peak time of the wounds and the surrounding normal skin. The full-thickness skin tissue of the wounds was taken for hematoxylin-eosin staining, and the thickness of necrotic dermal tissue was measured. The correlation between the blood flow intensity of the regions of interest in the wounds and the relative fluorescence intensity at the peak time of the regions of interest in the wounds and the surrounding normal skin and the thickness of necrotic dermal tissue in the wounds was analyzed. Results: The fluorescence intensity of the regions of interest in the surrounding normal skin showed a rapid increase followed by a slow decrease, with the peak time of approximately 60 seconds after administration. The fluorescence intensity of the regions of interest in the wounds showed a slow increase followed by a sustained stable trend, with the peak time of approximately 600 seconds after administration. The thickness of necrotic dermal tissue in the wounds caused by durations of injury of 5, 7, 9, 11, 13, 15, 17, and 19 seconds was (101±8), (130±6), (201±19), (197±30), (204±21), (280±39), (302±35), and (366±27) μm, respectively. The correlation between the blood flow intensity of the regions of interest in the wounds and the thickness of necrotic dermal tissue in the wounds was not significant (P>0.05). The relative fluorescence intensity of the regions of interest in the wounds at 60 seconds after administration was significantly negatively correlated with the thickness of necrotic dermal tissue in the wounds (R²=0.97, P<0.05), and the relative fluorescence intensity of the regions of interest in the wounds at 600 seconds after administration was significantly positively correlated with the thickness of necrotic dermal tissue in the wounds (R²=0.96, P<0.05). Conclusions: The relative fluorescence intensity of the regions of interest in porcine burn wounds detected by ICG-NIFI at 60 and 600 seconds after administration was significantly correlated with the thickness of necrotic dermal tissue in the wounds, indicating that ICG-NIFI has a significantly sensitive indicative effects for the thickness of necrotic dermal tissue in porcine burn wounds.