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Impressum
Treatment of experimental choroidal melanoma with a Nd:YLF laser at 1047 nm
1,2Krause M., 3Wachter E. A., 1Xiong J., 1Gragoudas E. S., 1Young L. H. Y.
1Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA; 2Department of Ophthalmology, University of Saarland, Homburg, Germany; 3Photogen Technologies, Inc., Knoxville, TN, USA
Objective: A new infrared laser system was tested in pigmented
choroidal melanoma.
Methods: B16F10 melanoma cells were implanted in the subchoroidal
space of 51 albino rabbits. Tumor heights were 1.3 to 3.9 mm. A mode-locked
(ML) Neodymium:Yttrium-Lanthanum-Fluoride laser (Nd:YLF laser) emitting
1047 nm focused femtosecond pulses (120 MHz) was used to investigate combined
thermal and photodynamic effects. The latter is based on multiphoton excitation
of endogenous melanin and conversion into phototoxic products. Continuous
wave (CW) light from the same laser served to remove the photodynamic
effect and study a new modality of thermotherapy. To study melanin heating,
1047 nm focused light (peak instantaneous irradiance (Iinst) 100kW/cm²)
was compared with 1047 nm unfocused light (Iinst 16W/cm²). Thermocouples
were implanted in 3 tumors for in vivo temperature measurements. Further
animals were used for control and histopathology.
Results: Twenty-six animals received a single treatment with 1047nm
focused ML or CW irradiation. At fluences >/= 125J/cm², tumors
regressed instantaneously in 19/20 animals (95%), while tumors regressed
in 7/16 animals (44%) at <125J/cm². Regrowth was found in 2/2 tumors
treated with 1047 nm unfocused CW irradiation. Temperature measurements
indicated faster tissue heating at 1047nm compared to 805nm.
Conclusion: A single treatment with focused Nd:YLF irradiation
at >125J/cm2 can destroy choroidal melanomas instantaneously. Focused
irradiation may provide more effective sub-millisecond heating of melanin
than unfocused irradiation. Further study may clarify the role of photodynamic
action.
Support: NIH EY 10975, Mass.Lions Eye Res. Fund, Photogen Technologies,
Inc., DFG Grant Kr 1918/1- 1,1918/1-2