Diagnostic and laser measurements in PDT

Abstract

The diagnosis of tissue alterations by fluorescence spectroscopy or different modalities of fluorescence imaging is widely used to detect precancerous or cancerous lesions. Demarcation of such lesions supports the efficient treatment either by photodynamic therapy (PDT) or conventional surgical intervention. Autofluorescence of tissue intrinsic chromophores like flavines, Nicotinamide-Adenine-Dinucleotide-Hydrogen (NADH), collagens or porphyrins excited by UV or blue light and change of the concentrations of the fluorescent compounds is an indication of tissue alterations. More specific is the use of fluorescent sensitizers enriched in target cells after local or systemic application. Meanwhile, sensitizers of the third generation are developed or coupled to nanoparticles as carriers. For application of the optimum light dose in PDT, dosimetry measurements must be performed with devices adapted to the geometry of the specific organ to be treated. The use of fluorescent sensitizers as diagnostic and therapeutic agents in dermatology goes back to Hermann von Tappeiner (1847–1927), director of the pharmacological institute at the university in Munich, in the late 19th century [1]. According to the findings of his student Raab (Z Biol 39:524–546, 1900) who discovered a light dependent phototoxicity in his cellular experiments [2], von Tappeiner introduced and published the term “photodynamic” in von Tappeiner and Jodlbauer (Dtsch Arch Klein Med 80:427–487, 1904). Since then, phototherapy continuously developed and Finsen Ackroyd et al. (Photochem Photobiol 74:656–669, 2001) were awarded the Nobel Prize 1903 after he had treated 800 patients suffering from Lupus vulgaris.