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Stress urinary incontinence (SUI) is the unintentional loss of urine. Currently, catheter and artificial urinary sphincters are applied for SUI treatment. However, these treatments are invasive and require continuous usage. While Er:YAG and CO2 lasers are used as a minimal or non-invasive method, their treatment effects are limited to the superficial vaginal tissue and can often cause severe burns, leading to tissue destruction. The purpose of this study to investigate the feasibility of non-ablative 980-nm laser treatment for SUI. Numerical simulations were performed to confirm thermal effects in urethral tissue by employing the Pennes bioheat transfer and partial differential equations. Rabbit urethral tissue was used for experimental validations. A non-compliant balloon was used to expand the urethral tissue, and the 980 nm laser light was irradiated on the tissue at 20 W for 15 s. After the laser irradiation, the treated samples were stained with hematoxylin and eosin (HE) to evaluate any physical changes in the overall urinary structure. Masson trichrome (MT) staining was performed to analyze the extent of thermal injury in the collagen of the urethral tissue. A uniform and symmetrical temperature distribution was observed around the balloon surface in the simulation. The numerical simulations and experiments indicated that mucosal and muscle layers in the urethral tissue reached the temperatures of 24 °C and 31 °C, respectively. Histology analysis presented the overall urinary structure with a total outer diameter of 10 mm from the mucosal layer to the muscle layer. The MT staining revealed that both control and treated groups had similar amounts of collagen components without thermal damage. The current study demonstrated that the non-ablative 980 nm laser could warrant an effective method of treating SUI with no or minimal thermal damage.
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