This study was carried out to investigate the effects of Nd:YAG laser-induced hyperthermia on murine F9 embryonal carcinoma cells in vitro using various power settings, temperatures, and exposure times. F9 cells were plated on gelatin-coated dishes, treated on the following day, and cultured overnight. The following day the killing efficiency of the treatments was estimated by staining the dishes or by labeling the cells with 3H-thymidine. A contact Nd:YAG laser with a frosted-end probe was used. After laser treatments at 39 degrees C, no significant changes were observed in the viability of the cells. Laser treatment at 43 degrees C killed F9 cells, and the effect was related to the power setting used. Using 6 W, the quantity of viable cells progressively decreased after 1-, 2-, and 5-min treatments, and no viable cells were found after a 10-min treatment. Using 10 W, approximately 10% of the cells survived a 1-min laser treatment, but all cells were killed after a 2-min treatment. In the control wells, heated in a water bath for up to 40 min, all cells regularly survived at 43 degrees C. There were much less viable cells in those laser-treated wells where the temperature exceeded 44 degrees C than in those where the temperature was kept at 44 degrees C. In conclusion, the tumoricidic effect of hyperthermia can be potentiated by the use of the contact Nd:YAG laser. At a set temperature the cell killing effect of laser treatment is dependent on the power used and the duration of the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
The effectiveness of two different techniques of laser-induced hyperthermia was analyzed in healthy piglet livers. Hyperthermia was produced using a continuous-wave Nd:YAG laser with both a contact sapphire probe and a bare quartz fibre. In both methods the tip was inserted into the liver, and the temperature 1 cm from the tip was raised and held between 42 degrees C and 44 degrees C for 600 seconds. Specimens were taken 0, 7 and 14 days after the treatment. The tissue effects of 36 treatment sites were analysed using standard van Gieson's method. In addition, a histochemical method for demonstrating lactate dehydrogenase activity was employed to show damage not observable by routine methods. No statistically significant difference in the extent of the treatment sites at d 0 and after 7 days was seen when comparing the two laser methods. After 2 weeks, the diameter of the lesion with the bare fibre was significantly larger (3,7 mm with both analysing methods) than by using the contact probe (2,6 with LDH demonstration; P < 0.01 and 2.1 mm with van Gieson's staining; P < 0.001). It can be concluded that the simple fibre tip seems more effective in causing tissue necrosis than the sapphire tip.
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