Akira Kaneda

The measurement of the absorption coefficient of ME2906 in tissue using a semiconductor laser

The light distribution in vivo during Photodynamic Therapy is dependent on a pre-administered photosensitizer in the target tissue. To discuss the light absorption of photosensitizer(ME2906) ,the light distribution in noinial muscle at 664 nm was measured with optical detector fiber. From this distribution , the absorption coefficient of ME2906 in tissue was calculated. As an optical source, a semiconductor laser is prepared. The incident laser beam diameter at the tissue surface is 10 mm, and the power density was 100 mW/cm2. In proportion as the concentration of ME2906 increases, absorption coefficient of ME2906 increases in the range from 0.06 to 0.16 mm-1. This coefficients are related to ME2906 concentrations in the plasma and tissue. Therefore, ME2906 concentrations of plasma were examined by high-performance liquid chromatography (HPLC).

Photodynamic therapy using a diode laser with mono-L-aspartyl chlorin e6 (NPe6)

The authors developed a new high-power red laser diode system (Matsushita Industrial Equipment Co., Ltd., Osaka) for photodynamic therapy (PDT) with mono-L-aspartyl chlorin e6 (NPe6, Meiji Seika Kaisha LTD.). The laser wavelength was adjusted to 664 nm and the power output could be varied in the range of 50-500 mW at the fiber tip in a continuous wave (cw) mode. The delivered energy could be adjusted from 50 - 1000 J. The system has a size of 49 by 20 by 40 cm, weighs 20 kg, and is readily portable. It runs on 100 V current. The laser power is easily controlled and the wavelength is stable (less than plus or minus 0.2 nm). The output beam is delivered via a quartz fiber. Furthermore, the full width at half-maximum power is less than 2 nm, which enables uniform, high-density photoirradiation. The power density distribution of the laser, analyzed by a CCD camera, was uniform throughout the photoirradiated field. In an animal study, tumor-bearing Balb/c mice were treated with the diode laser 5 hours after intravenous administration of NPe6 at a dose of 1.25 to 12.5 mg/kg i.v.. Total photoirradiation ranged from 3.13 to 250 J/cm2 which the energy density was adjusted to 100 mW/cm2. Percentages of cures were determined histopathologically from numbers of mice apparently disease-free 1 week after treatment. The results show that a laser energy of more than 12.5 J/cm2 was necessary to obtain 90% tumor cure rate at a maximum dose of NPe6 (12.5 mg/kg) and NPe6 dose of more than 2.5 mg/kg was necessary to obtain 90% cure rate at high laser energy of 200 J/cm2.