Dosimetry study of photothermal ablation for the treatment of urethral stricture

Urethral stricture is a condition where the urethra narrows due to chronic inflammation or scarring, causing slow or weak urine flow and discomfort during urination. Treatments include dilation of the urethra with a thin rod or balloon catheter, incision of the scar with a cystoscope and scalpel, or anastomosis after incision. However, treatment has a high recurrence rate and requires incision or dilatation of a larger area than the stricture area during treatment. To minimize the recurrence rate and treatment area, the current study proposes a near-infrared laser-based cylindrical photothermal ablation method. The laser wavelength was selected at 1470nm, which has a high absorption rate in urinary tissue. The radial fiber was used to treat the cylinder-shaped urethra tissue. Numerical simulations were conducted in liver and urethra tissues under each 25–200 and 75–100 J conditions, respectively. Ex vivo liver and urethra experiments were conducted under 75–200J and 75J conditions, respectively. After the experiments, irradiated liver tissues were measured for coagulation area. And irradiated urethra tissues were stained with hematoxylin and eosin (H&E). In both the numerical simulation and ex vivo experiments in liver tissue, the coagulated areas were circumferentially increased depending on the irradiation power and time. Also, both in the numerical simulation and ex vivo experiments in urethra tissue, the ablated areas were symmetric and uniformly ring-shaped. The 15W for 5s condition ablated the urethral wall up to 705.5±63μm of depth and 2631.2±455μm of length. The laser-based urethra stricture treatment with a 1470nm laser under 15W for 5s effectively ablates the endoluminal urethra surface. The proposed laser treatment for urethral stricture can control ablation depth and area. To confirm safety and chronic inflammation, an in vivo study will be conducted to monitor stricture recurrence after laser treatment.