Experimental study on the vascular thermal response to visible laser pulses.

Port-wine stains (PWSs) are congenital vascular malformations that progressively darken and thicken with age, and laser therapy is the most effective in clinical practice. Using dorsal skin chamber (DSC), this study evaluated thermal response of blood vessel to a 595-nm pulsed dye laser (PDL) with controlled energy doses and pulse durations. Totally, 32 vessels (30∼300 µm in diameter) are selected from the dorsal skin of the mouse to match those in port-wine stain. The experimental results showed that the thermal response of the blood vessels to laser irradiation can be recognized as coagulation, constriction with diameter decrease, disappearance (complete constriction), hemorrhage, and collagen damage in the order of increasing laser radiant exposure. Blood vessels with small diameter would response poorly and survive from the laser heating because their thermal relaxation time is much shorter than the pulse duration. The optimalradiant exposure is from 10 to 12 J/cm(2) under 6 ms pulse duration without considering the epidermal light absorption. Numerical simulations were also conducted using a 1,000-µm deep Sprague-Dawley (SD) mouse skinfold. The light transportation and heat diffusion in dorsal skin were simulated with the Monte Carlo method and heat transfer equation, while the blood vessel photocoagulation was evaluated by Arrhenius-type kinetic integral. Both experimental observation and numerical simulation supported that hemorrhage is the dominant thermal response, which occurs due to preferential heating of the superior parts of large blood vessels. In clinical practice for 595 nm PDL, the consequent purpura caused by hemorrhage can be used as a treatment end point.

Serum trace metals in Blackfoot disease patients.

The purpose of this study was to investigate ultratrace levels of metals in serum of patients with Blackfoot disease (BFD). BFD is an endemic peripheral vascular disorder confined to a limited area along the southwest coast of Taiwan. In this study, graphite furnace atomic absorption spectrophotometry with stabilized temperature platform furnace conditions was used for the determination of selenium, manganese, cobalt, chromium and zinc. This technique includes a dilution of serum with 12 mM ultrapure nitric acid and 1% Triton X-100. The results showed that total manganese, cobalt, chromium and zinc levels in the BFD patients were significantly different from those in normal controls (P < 0.05). The total selenium level in the BFD patients was not different from the normal controls (P > 0.05). The possible connection of these elements with the etiology of the disease is discussed.