Berns+Lecture+4

Berns+Lecture+4 - Photodynamic Therapy (PDT ) and...

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Unformatted text preview: Photodynamic Therapy (PDT ) and Refractive Surgery (a double-whammy lecture) MOMENTUM TRANSFER Multi-photon Single photon Photodynamic Therapy (PDT) Photosensitizer Administration Light Irradiation Patient is administered a photosensitizing drug which accumulates selectively in targeted tissue. Drug is inert unless activated by specific wavelengths of light. Selective Accumulation Target Destruction tumor Photochemistry: Type II Reaction Ground State Singlet State Light h O 2 1 O 2 Molecular Oxygen Singlet Oxygen Intersystem Crossing Photosensitizer Cell Death Triplet State Has a nanosecond life-time: what is significance? (Photofrin) Photophysics in spot irradiance = power density = W/cm 2 [From: Berns, M.(1998) Sci. Am. 198:62-7] Jablonski Diagram (linear single photon absorption) Type II Reaction Vibrational heat Basic sensitizer is a porphyrin (originally extracted from hemoglobin) Tetrapyrrole ring Major component of hemoglobin (Fe) HPD = hematoporphyrin derivative (Photofrin = commercial drug) Mixture of several porphyrins Major active ingredient is Protoporphyrin IX lowest lying singlet state Absorption Spectrum of Protoporphyrin IX Treatment wavelength: why is this desirable? HPD peak @ 625 nm So does PDT work? Photodynamic Therapy (PDT) Photosensitizer Administration Light Irradiation Patient is administered a photosensitizing drug which accumulates selectively in targeted tissue. Drug is inert unless activated by specific wavelengths of light. Selective Accumulation Target Destruction Pre-Laser and pre HPD injection Patient with recurrent breast cancer to the chest wall 24 hours post laser exposure What is the nature of the tumor...
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Berns+Lecture+4 - Photodynamic Therapy (PDT ) and...

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