1993 Volume 14 Issue Supplement Pages 347-350
A diode laser system is commonly used as a light source in pain control, but normally it is impossible to use the diode laser for PDT using a common photosensitizer, because it has a too high wevelength and lower laser power. Recently, Matsushita Industrial Equipment Co has developed a new diode laser system which is considered to have potential for PDT with NPe6, due to it's lower wavelength (664nm) and greater laser power. 1×106(one times ten to the sixth) Meth-A fibrosarcoma cells were implanted subcutaneously in the back of four-week-old BALB/ c female mice. A week later, the diode laser was applied five hours after the intravenous administration of NPe6 to each tumor-bearing mouse. At that time implanted tumors generally reached 10mm in diameter and 5mm in thickness in size and the photoradiated field was adjusted 14mm in diameter. The diode laser was adjusted to 664nm wavelength to fit the absorption bands of NPe6. In the first study the rise of tumor temperature during PDT was measured. The different laser light doses were delivered: 0, 50, 100, 150 and 300mW/cm2. A 23-gauge thermocouple hypodermic needle was inserted at a depth 2mm from the tumor surface and intratumoral temperatures were documented chronologically.The average tumor temperature rise at 0, 50, 100, 150, and 300mW/cm2 was 0, 1.75, 3.80, 4.42 and 10.58°C rise during photoradiation. In this investigation our purpose was to examine the effectiveness of PDT alone excluding the effect of any hyperthermia, so in the second study the power of laser was fixed at 100mW/cm2, as this caused only a slight elevation in temperature, below the temperature range of hyperthermia. In the second study six groups of 10 tumor-bearing mice per group were treated with the diode laser 5 hours after the intravenous administration of NPe6 derivative at a dose 1.25, 2.5, 5.0, 7.5 mg/kg i. v. to each tomor-bearing mouse. Total photoradiation ranged from 0 to 150 J/cm2 and the dose rate of delivered light was adjusted to 100mW/cm2. Percentages of cures were determined from numbers of mice that were apparently disease-free 50 days following treatment. Conclusions run as follows: 1.PDT is effective in the treatment of implanted fibrosarcoma using a diode laser with NPe6. 2. We obtained tumor therapeutic effects by PDT unrelated to any hyperthermia effects. 3. The power of the diode laser beam was uniform in intensity throughout the photoradiated field.
