Comparison of the local effects of a 600-μm bare fibre at high laser power on lung parenchyma: Nd:YAG laser 1320 vs. 1064 nm

Local Effects of a 1940 nm Thulium-Doped Fiber Laser and a 1470 nm Diode Laser on the Pulmonary Parenchyma: An Experimental Study in a Pig Model

The lungs are a common site of metastases from malignant tumors. Their removal with a minimal but safe tissue margin is essential for the long-term survival of patients. The aim of this study was to evaluate the usefulness of a 1940 nm thulium-doped fiber laser (TDFL) and a 1470 nm diode laser (DL) in a pig model of lung surgery that involved the incision and excision of lung tissue. Histopathological analysis was performed on days 0 and 7 after surgery. Neither TDFL nor DL caused significant perioperative or postoperative bleeding. Histological analysis revealed the presence of carbonized necrotic tissue, mixed fibrin-cellular exudate in the superficial zone of thermal damage and bands of deeper thermal changes. The mean total width of thermal damage on day 0 was 499.46 ± 61.44 and 937.39 ± 109.65 µm for TDFL and DL, respectively. On day 7, cell activation and repair processes were visible. The total width of thermal damage was 2615.74 ± 487.17 µm for TDFL vs. 6500.34 ±1118.02 µm for DL. The superficial zone of thermal damage was narrower for TDFL on both days 0 and 7. The results confirm the effectiveness of both types of laser in cutting and providing hemostasis in the lungs. TDFL caused less thermal damage to the lung parenchyma than DL.

Porcine skin damage thresholds and histological damage characteristics from 1319-nm laser radiation

There is an increasing use of near-infrared lasers in biomedical applications operating in the spectrum between 1300 and 1400 nm. To corroborate and expand the existing safety data for skin exposure to lasers in this wavelength region, the in-vivo ED50 damage thresholds were determined in Guizhou miniature pigs for 1319-nm laser radiation. Exposure durations of 0.4, 1.0, and 3.0 s and 1  /  e2 beam diameters of 0.98 and 1.96 cm were employed. Damage lesion determinations were performed at 1- and 24 h post exposure. The Bliss probit analysis was employed to establish the ED50 damage thresholds. Histopathological studies of skin damage were performed at 48 h after irradiation to reveal the damage characteristics. The skin damage thresholds at 1 h post exposure, given in peak radiant exposure, were 35.5, 36.1, and 37.1  J  /  cm2 at exposure durations of 0.4, 1.0, and 3.0 s with the spot diameter of 0.98 cm, and 28.6  J  /  cm2 at exposure duration of 3.0 s with the spot diameter of 1.96 cm. At 24 h post exposure, the ED50s increased slightly. Histologically, the thermal damage characteristics at the near-threshold level included gathering of the nuclear chromatin and cell vacuolation in the epidermis and deposition of blood cells in the capillary vessels. However, at the apparently above-threshold level, the damage characteristics included obvious stretching of the nuclear chromatin in the epidermis, closing of the capillary lumen, structural change of collagen fibers, and coagulative necrosis of the hair follicle cells. The damage induced by this laser could go deep into the fatty tissue. The obtained results may contribute to the knowledge base for the damage mechanisms and expand the database for the refinement of laser safety standards in the wavelength range of 1300 to 1400 nm.

Retinal damage thresholds from 100-millisecond laser radiation exposure at 1319 nm: a comparative study for rabbits with different ocular axial lengths

With the widespread use of high-power laser systems in the wavelength spectrum between 1300 and 1400 nm, the risk of ocular damage becomes more serious and concerning. Existing ocular bio-effects studies have revealed unique damage characteristics, the damage mechanisms involved, and the trends of damage thresholds in this wavelength range. However, the influence of ocular axial length on retinal damage thresholds has not been investigated quantitatively. In this paper, using a 1319 nm continuous-wave laser, the in-vivo retinal damage thresholds were determined for two groups of chinchilla grey rabbits with the ocular axial lengths of 15.97 and 17.25 mm, respectively. The incident corneal irradiance diameter was fixed at 5 mm and the exposure duration was 0.1 s. The determined ED₅₀ values at 24-h post-exposure for the axial lengths of 15.97 and 17.25 mm were 1.06 and 1.79 J, respectively. Detailed analysis revealed that a sufficient margin existed between the damage threshold and MPE for adult humans, but for the newborn eyes, the safety factor may be less than 2.3.