Photodynamic therapy with topical aminolevulinic acid

Figure 1 Jablonski diagram showing the various modes of excitation and relaxation in a chromophore. A: Excitation; B: Fluorescence; C: Intersystem crossing; D: Phosphorescence; E: Non-radiative transfer of energy to singlet oxygen; F: Substrate oxidation by singlet oxygen; G: Internal conversion (adapted from Macdonald et al[1]).

Figure 2 Cellular damage mechanism. Type-I and Type-II photoreactions, where ¹P is a photosensitizer in a singlet ground state, ³P¹ is a photosensitizer in a triplet excited state, S is a substrate molecule, P^ÿ is reduced photosensitizer molecule, S is an oxidized substrate molecule, O₂ is molecular oxygen (triplet ground state), O^ÿ₂ is the superoxide anion, O₂ is the superoxide radical, P is the oxidized photosensitizer, ³O₂ is triplet ground-state oxygen, ¹O₂ is oxygen in a singlet excited state, and S (O) is an oxygen adduct of a substrate (adapted from Macdonald et al[1]).

Figure 3 Summary of the pathways and feedback loops involved in mitochondrially controlled apoptosis. Star bursts represent possible points at which photodynamic therapy initiates mitochondrially controlled apoptosis (adapted from Macdonald et al[1]).

Figure 4 Lesion is treated with a curette to selectively remove the corneal layer.

Figure 5 After curettage no bleeding might be present.

Figure 6 Cream is applied on the lesion and an occlusive dressing is then performed.

Figure 7 Patient affected by multiple actinic keratosis of the scalp treated with photodynamic therapy with aminolevulinic acid; result after 3 wk from the 1^st application.