Validation of a non-invasive fluorescence imaging system to monitor dermatological PDT

• Published in: Photodiagnosis and photodynamic therapy Vol. 7; no. 2; pp. 86 - 97
• Main Authors: Tyrrell, Jessica, Campbell, Sandra, Curnow, Alison, PhD, BSc (Hons)
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-06-2010
• Subjects: Aged; Aminolevulinic Acid - analogs & derivatives; Aminolevulinic Acid - therapeutic use; Dermatology; Dose-Response Relationship, Drug; Fluorescence; Fluorescence diagnosis (FD); Hematology, Oncology and Palliative Medicine; Humans; Internal Medicine; Keratosis, Actinic - drug therapy; Keratosis, Actinic - pathology; Keratosis, Actinic - radiotherapy; Male; Methyl-aminolevulinate (MAL); Metvix; Non-invasive fluorescence imaging; Photochemotherapy - instrumentation; Photochemotherapy - methods; Photochemotherapy - standards; Photodynamic therapy (PDT); Photosensitizing Agents - therapeutic use; Protoporphyrins - therapeutic use; Reproducibility of Results; Skin; Skin Neoplasms - drug therapy; Skin Neoplasms - pathology; Skin Neoplasms - radiotherapy; methyl-aminolevulinate; BCC; protoporphyrin IX; Metvix; Dermatology; 5-aminolaevulinic acid; PpIX; AK; Fluorescence diagnosis (FD); actinic keratosis; Photodynamic therapy (PDT); ALA; Non-invasive fluorescence imaging; basal cell carcinoma; MAL; Methyl-aminolevulinate (MAL)
• ISSN: 1572-1000; 1873-1597
• DOI: 10.1016/j.pdpdt.2010.03.002

Summary Background Methyl-aminolevulinate (MAL) photodynamic therapy (PDT) involves selective accumulation of a photosensitiser, protoporphyrin IX (PpIX), primarily in tumour tissue, which in combination with visible light and tissue oxygen results in reactive oxygen species (ROS) production and thus cellular destruction. Methods A non-invasive fluorescence imaging system (Dyaderm, Biocam, Germany) has been employed to acquire colour (morphological) and fluorescent (physiological) images simultaneously during dermatological PDT. This system had been previously utilised for fluorescence diagnosis, however, here changes in PpIX concentration within the skin lesions and normal tissue were followed after MAL application. Measurements were also recorded from a synthetic PpIX standard. Results Results indicated that imaging distance, imaging angle, position of the region of interest and light conditions all altered the PpIX levels acquired from the synthetic PpIX standard. The imaging system was therefore adapted and a standard operating procedure developed allowing reproducible images of dermatological lesions to be acquired. Different concentrations of synthetic PpIX were analysed with the system and a linear relationship was observed between the PpIX concentration and the mean greyscale value calculated for the images acquired up to 10 μM. Conclusions The Dyaderm imaging system can now be used reproducibly with confidence to semi-quantify PpIX (within the range of 0–10 μM) within dermatological lesions using the standard operating procedure derived from this work.