A Comparison between Argon‐dye and Excimer‐dye Laser for Photodynamic Effect in Transplanted Mouse Tumor

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Abstract
Photodynamic therapy (PDT) utilizing a hematoporphyrin derivative (HpD) as a sensitizer has become a viable option for the local treatment of neoplastic disease. The argon‐dye laser system is commonly used as a light source in this treatment modality. The excimer‐dye laser, on the other hand, delivers high‐energy red light in a pulsatile fashion. In this investigation, we treated BALB/c mice bearing mouse kidney sarcoma cell tumors with PDT using HpD at the dose of 5 mg/kg body weight as a photosensitizer and either a standard argon‐dye laser or the pulsatile excimer‐dye laser as the light source. At equal light energy doses (50 J/cm2), necrotic changes at depths averaging 4 mm from the tumor surface were obtained with the argon‐dye laser (200 mW power output) while tumor necrosis at depths exceeding 15 mm from the tumor surface was obtained using the excimer‐dye laser (6 mJ/pulse, 5 Hz). To determine the best conditions for photoirradiation with the excimer‐dye laser, tumor‐bearing mice were treated with different total light doses (10, 30 and 50 J/cm2), dose rates (1, 3 and 6 mJ/cm2), and frequencies (5,15 and 50 Hz) of light exposure. Our results indicate that the optimal effects obtained with the excimer‐dye laser are related to the total light dose used and the dose rate, but not to the frequency of light exposure.