Experimental and clinical studies on balloon laserthermia using Nd: YAG laser for uterine endometrial cancer

Laser ablation of pancreatic cancer using a cylindrical light diffuser

Pancreatic cancer (PC) is a leading cause of cancer death and its incidence and mortality have shown an increasing trend. Despite improvements in outcomes, another treatment option is required for PC. Laser ablation (LA) has been evaluated for the treatment of various types of cancer. The aim of this study was to assess the safety and feasibility of a novel cylindrical light diffuser in a xenograft model of PC. This study was performed using a customized high-power laser system. PANC-1 cells and BALB/c mice were used for experiments at a laser power of 5 W for 40 to 200 s at five different energy levels (n = 30). There was no acute bleeding or major complication. Using the cylindrical light diffuser, tumors were irradiated with similar size in each energy group. A correlation between laser dose and tumor necrosis was observed. Pearson's correlation for the relation between the amount of necrosis area and laser ablation energy on day 3 was 0.78 (p < 0.01). No statistical difference of necrosis area was exhibited when the necrosis area of each harvested tumor analyzed by dividing into 5 specimens for each energy. The study demonstrates that LA treatment using a cylindrical light diffuser induced remarkable tumor necrosis at histopathologic examinations. Laser ablation dosage and tumor response were strongly correlated, and the ablation procedure resulted in homogeneous tissue necrosis. No adverse event was encountered. These findings suggest that the devised cylindrical light diffuser offers a safe and effective means of treating pancreatic cancer.

Optical feedback-induced light modulation for fiber-based laser ablation

Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30% in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation.

Computational analysis of endometrial photocoagulation with diffusing optical device

A balloon-catheter optical diffuser for endometrial treatment was evaluated with computational thermal analysis. Various catheter materials and dimensions were implemented to identify the optimal design for the device. Spatial and temporal development of temperature during 30-sec irradiation of 532-nm light demonstrated thermal insulation effects of polyurethane on temperature increase up to 384 K, facilitating the irreversible denaturation. The current model revealed the degree of thermal coagulation 13% thicker than experimental results possibly due to lack of tissue dynamics and light intensity distribution. In combination with photon distribution, the analytical simulation can be a feasible tool to optimize the new optical diffuser for efficient and safe endometrial treatment.