Background and Objective: This study evaluated the use of low-output, non-contact irradiation by KTP laser (potassium-titanyl phosphate) (λ=532nm) for hemangiomas using a rabbit liver model, and calculated the tissue temperature distribution using the thermal conduction equation.
Study Design/Materials and Methods: Laser irradiation was applied to the liver of rabbits at various power densities(1.0 to 8.0 J/cm²). Paraffin sections of irradiated sections were prepared, and histology was correlated with the tissue temperature distribution calculated from the thermal conduction equation.
Results: When the measured depth of coagulation was introduced into the thermal conduction equation, laser irradiation of about 4.0 J/cm²was required to raise the tissue temperature to 60°C at a depth of 1mm with an irradiation distance of 2.5mm.
Conclusion: Coagulation therapy by non-contact irradiation with a KTP laser is appropriate for treating hemangiomas. However, as the depth of coagulation is limited to the surface of the irradiated site, multiple sessions may be required for complete eradication of the lesion.

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The efficiency of photodynamic therapy (PDT) is strongly related to light-induced singlet oxygen generation. We have built a direct detection system monitoring feeble luminescence, in the near IR region, from singlet oxygen. This system can measure emission spectra of singlet oxygen with a very high SN ratio even in a short integration time. Comparing ATX-S10, expected to be a good candidate for the second generation PDT photosensitizer, with Photofrin, we found ATX-S10 turned out to yield singlet oxygen over twenty times more than Photofrin in solution experiments with the same weight concentration. Absorption spectra of ATX-S10 showed a strong interaction with human serum proteins, and we were able to determine the optimum excitation wavelength for the highest singlet oxygen generation under such serum solubilized conditions.

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Lasers have been widely applied in the field of medicine and surgery. However laser applications are very rare in the field of cardiovascular surgery through out the world. It is now difficult to keep long-term patency after anastomosis of the conventional fashion with suture materials especially for small-caliber vessels.
First of all, the relationship between output and irradiation time of a CO₂ laser was analyzed as well as tissue reaction to the laser in a preliminary experiment. From these preliminary experiments it could be concluded that the optimal laser output was 20-40mW and irradiation time was 6-12sec/mm for vascular anastomosis. of small-caliber vessels in the extremities. Side-to-side, end-to-side, and end-to-end anastomosis at the site of the femoral arteries and veins or the carotid arteries and veins were carried out using a low energy CO₂ laser. Diameter of these vessels ranged from 2 to 10mm with a mean of 4mm and laser beam was moved slowly along the anastomic line. Pressure tolerance test and tensile strength test as well as histological examinations were also performed to evaluate the intensity of the laser anastomotic site of the vessels. Consequently, there were no hemorrhages from the sites of laser anastomosis which were effective enough for the site to tolerate high pressures (300mmHg) without bleeding.
On the other hand, the laser anastomotic sites were separated in weights 1,034.2±103.9g, and the sites of anastomosis sutured by 5-0 suture material were also separated into weight 1,103.7±144.8g.
The sites of laser vascular anastomosis were microscopically examined after several time of intervals. Subsequently, good healings of laser anastomotic sites were clearly observed histologically.
From the good experimental studies, laser vascular anastomosis was employed in 111 patients (136 anastomotic sites) with anginal attack, or chronic renal failure and peripheral vascular disorders. Finally, laser vascular anastomosis should be recommended to the reconstructions of small-caliber vessels less than 4mm in diameter.
Finally, current trends of vascular tissue welding were described.

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