Photoactive dye-enhanced tissue ablation for endoscopic laser prostatectomy.

BACKGROUND AND OBJECTIVE: Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia (BPH) over 20 years. Recently, application of high laser power up to 200 W was often reported to swiftly remove a large amount of prostatic tissue. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue vaporization with low laser power. MATERIALS AND METHODS: Chicken breast tissue was selected as a target tissue due to minimal optical absorption at the visible wavelength. Four biocompatible photoactive dyes, including amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532 nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm(2) . Light absorbance and ablation threshold were measured with UV-Vis spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. RESULTS: Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with radiant exposure, dye concentration, and number of injection. Among the dyes, AR created the highest ablation rate of 44.2 ± 0.2 µm/pulse due to higher absorbance and lower ablation threshold. High aspect ratios up to 7.1 ± 0.4 entailed saturation behavior in the tissue ablation injected with AR and BD, possibly resulting from plume shielding and increased scattering due to coagulation. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33% reduced laser power with almost equivalent performance. CONCLUSION: Due to efficient coupling of optical energy, pre-injection of photoactive dyes promoted the degree of tissue removal during laser irradiation. Further studies will investigate spatial distribution of dyes and optimal injecting pressure to govern the extent of dye-assisted ablation in a predictable manner. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser vaporization for BPH with low power application.

Suppression of Cation Segregation in (La,Sr)CoO3-δ by Elastic Energy Minimization.

Strontium segregation at perovskite surfaces deteriorates the oxygen reduction reaction kinetics of cathodes and therefore the long-term stability of solid oxide fuel cells (SOFCs). For the systematic and quantitative assessment of the elastic energy in perovskite oxides, which is known to be one of the main origins for dopant segregation, we report the fractional free volume as a new descriptor for the elastic energy in the perovskite oxide system. To verify the fractional free volume model, three samples were prepared with different A-site dopants: La0.6Sr0.4CoO3-δ, La0.6Sr0.2Ca0.2CoO3-δ, and La0.6Ca0.4CoO3-δ. A combination of the theoretical calculations of the segregation energy and oxide formation energy and experimental measurements of the structural, chemical, and electrochemical degradation substantiated the validity of using the fractional free volume to predict the dopant segregation. Furthermore, the dopant segregation could be significantly suppressed by increasing the fractional free volume in the perovskite oxides with dopant substitution. Our results provide insight into dopant segregation from the elastic energy perspective and offer a design guideline for SOFC cathodes with enhanced stability at elevated temperatures.

Endoluminal application of glass-capped diffuser for ex vivo endovenous photocoagulation.

Endovenous laser ablation (EVLA) has frequently been used to treat varicose veins for 20 years. In spite of 90˜95% occlusion rates, clinical complications such as burn and ecchymosis still occur due to excessive thermal injury to perivenous tissue. In the current study, a glass-capped diffusing applicator is designed to validate the feasibility of EVLA as an effective therapeutic device by applying circumferential light distribution. The proposed device is evaluated with a flat fiber as a reference in terms of temperature elevation, fiber degradation, and degree of coagulative necrosis after 532 nm-assisted EVLA at 100 J/cm. The diffusing fiber generates a 40% lower maximum temperature with a 90% lower transient temperature change in blood, compared to the flat fiber. Due to low irradiance (13.5 kW/cm2 ) and wide light distribution, the diffuser tip experiences no significant thermal degradation while severe carbonization occurs at the flat fiber tip. Ex vivo tissue tests verify that the diffusing fiber induces circumferential and consistent tissue denaturation to the vein wall (107.8 ± 7.8 µm) along with 19% vessel shrinkage. The proposed glass-capped diffusing applicator can be a feasible therapeutic device for EVLA with minimal complications by entailing low maximum temperatures and uniform tissue denaturation in the venous tissue.

A subjective utilitarian theory of moral judgment.

Current theories hypothesize that moral judgments are difficult because rational and emotional decision processes compete. We present a fundamentally different theory of moral judgment: the Subjective Utilitarian Theory of moral judgment. The Subjective Utilitarian Theory posits that people try to identify and save the competing item with the greatest "personal value." Moral judgments become difficult only when the competing items have similar personal values. In Experiment 1, we estimate the personal values of 104 items. In Experiments 2-5, we show that the distributional overlaps of the estimated personal values account for over 90% of the variance in reaction times (RTs) and response choices in a moral judgment task. Our model fundamentally restructures our understanding of moral judgments from a competition between decision processes to a competition between similarly valued items. (PsycINFO Database Record