Quantitative and Qualitative Evaluation of Supercontinuum Laser-Induced Cutaneous Thermal Injuries and Their Repair With OCT Images

Background and Objectives: Laser-induced thermal injuries are a heavily researched topic in laser medicine and biomedicine. To explore the quantitative biological effects of laser-induced injury repair, we propose an optical imaging-based in vivo evaluation method and discuss the injury effect and repair characteristics of skin tissue. Study Design/Materials and Methods: A supercontinumm laser (spectrum width ranged from 400 to 2400 nm) was used to irradiate live mice. The radiation doses were set as 32.85, 65.69, 98.4, and 197.08 J/cm². Laser-induced cutaneous thermal injuries were observed and measured after laser radiation. Optical coherence tomography (OCT) was used to image the injured spots. The optical attenuation coefficient (OAC) was computed using a Fourier-domain algorithm. Three-dimensional (3D) visualizations of the injured spots in the OCT images were constructed to qualitatively demonstrate the degree of the thermal injury at different times. The corresponding pathological changes of the skin injuries were observed dynamically. Results: Under increasing radiation doses, the injured spots, which ranged in degree from mild to severe, appeared accordingly. The mean OAC value of normal skin was 1.15 ± 0.01 mm⁻¹. The mean values of the OAC maps in the region of interests (ROIs) were 0.88 ± 0.05, 0.91 ± 0.02, 0.93 ± 0.04, and 0.98 ± 0.08 mm⁻¹ at each of the four radiation levels, respectively. Additionally, the 3D OCT visualization showed a directed view of the injured spots and the healing process and was used as a qualitative evaluation method. The OCT images and pathological results showed that the damage tended to vary across all groups, but this trend tended to weaken as the radiation dose increased. Conclusion: Optical imaging provides an in vivo noninvasive and real-time evaluation method to comprehensively quantify supercontinuum laser-induced thermal injuries and wound healing. The OACs and 3D visualizations of the OCT cubic data enable the areas of the direct injured spots to be measured and the inner structure to be viewed. The results obtained with these techniques indicate that the skin injuries are aggravated and tissue repair trends weaken as the radiation doses increase. This method would have a potential application for laser-medicine and laser-biological effects in the future. Lasers Surg. Med.