DETERMINING LIGHT DOSE FOR PHOTODYNAMIC THERAPY OF ATHEROSCLEROTIC LESIONS IN THE YUCATAN MINISWINE

Purpose: To determine the light dose required for photodynamic therapy of atherosclerotic lesions in the miniswine. Methods: Aortic atherosc lerosis was created in seven Yucatan miniswine by a combination of bal loon endothelial injury and 2% cholesterol and 15% lard for 7 weeks. S ix animals received the photosensitizer Photofrin(R) 2.5 mg/kg, while an additional swine received no drug. After 24 hours, the abdominal ao rta was exposed and the aorta opened longitudinally in each animal. Th ree 1-cm spots were illuminated with energy densities of 60, 120, and 240 J/cm(2) from an argon-pumped dye laser tuned to 630 nm with a lase r output of 1 W. Four weeks later, the animals were killed, abdominal aortae removed, and intimal thickness determined by morphometry. Resul ts: The percentage intimal thickness (mean +/- SD) was 36.7 +/- 27.1, 9.1 +/- 5.0, and 6.4 +/- 8.1 for the three energy densities, respectiv ely. Although both 120 and 240 J/cm(2) energy densities produced signi ficant (p < 0.05) reduction in atheroma, considerable damage to the un derlying media was also observed in the 240 J/cm(2) group. Conclusions : A Photofrin dose of 2.5 mg/kg and 120 J/cm(2) light are necessary fo r adequate ablation of atheroma while avoiding extensive medial damage .