<title>Fluorescence photodetection of head and neck cancer following topical or systemic application of 5-aminolevulinic acid</title>

Autofluorescence imaging and spectroscopy of normal and malignant mucosa in patients with head and neck cancer

“…A most common theory is that the observed red fluorescence is a product of microbial porphyrin synthesis, and therefore its distribution is limited to the necrotic surface of exulcerated tumors [30,33]. Our own examinations have shown a bright red fluorescence due to endogenous porphyrins on the dorsums of tongues, on gingival plaques and on the bacterial coating of necrotic parts of some of the oral neoplasms we have investigated in our previous studies [26][27][28]. In this present investigation, we found only one third of the tumors examined (33.3%) to be mostly covered by strongly red fluorescing material.…”

“…Its highest intensities lie within the soret band for porphyrins, and it is appropriately used for the excitation of 5-ALA induced PPIX [26][27][28]. However, we have noticed a subjective decrease of autofluorescence intensities in the green spectral range and irregular red fluorescing spots on the tumorous surfaces we have examined even before 5-ALA was applied.…”

“…However, we have noticed a subjective decrease of autofluorescence intensities in the green spectral range and irregular red fluorescing spots on the tumorous surfaces we have examined even before 5-ALA was applied. As we believe, high subjective contrasts of cancerous tissue (red) to healthy mucosa (green) after 5-ALA application [26][27][28] may be due to both a higher accumulation of PPIX and a decrease of green autofluorescence within the tumor. Based on these observations, we have endeavored to objectify our findings.…”

“…Even for the experienced clinician, however, currently available diagnostic methods are fairly limited, as both inspection (macroscopic and endoscopic) and conventional imaging techniques sometimes lack to provide reliable results in the detection of these flat, early tumors within the oral mucosa. Therefore, new alternative diagnostic methods in the field of otorhino-laryngology are sought for by numerous international research groups [7,[11][12][13][14]19,20,[26][27][28]43]. In these investigations, dyes or fluorescent markers respectively have been employed in order to achieve a better demarcation of the tumor boundaries.…”

“…Kennedy et al were the first to propose 5-ALA induced PPIX for the detection of pre-malignant and malignant oral mucosa [25]. In previous publications [26][27][28], our group has reported on the successful use of topically applied 5-ALA for a fluorescence-aided staining of oral squamous cell carcinomas. To us, this method represents a very useful tool in demarcation and detection of both early and advanced oral cancer, and is at the same time reproducible and easily conductible without any side effects for the patients.…”