title: In vivo quantification of photosensitizer fluorescence in the skin-fold observation chamber using dual-wavelength excitation and NIR imaging.
abstract: A major challenge in biomedical optics is the accurate quantification of in vivo fluorescence images. Fluorescence imaging is often used to determine the pharmacokinetics of photosensitizers used for photodynamic therapy. Often, however, this type of imaging does not take into account differences in and changes to tissue volume and optical properties of the tissue under interrogation. To address this problem, a ratiometric quantification method was developed and applied to monitor photosensitizer meso-tetra(hydroxyphenyl) chlorin (mTHPC) pharmacokinetics in the rat skin-fold observation chamber. The method employs a combination of dual-wavelength excitation and dual-wavelength detection. Excitation and detection wavelengths were selected in the NIR region. One excitation wavelength was chosen to be at the Q band of mTHPC, whereas the second excitation wavelength was close to its absorption minimum. Two fluorescence emission bands were used; one at the secondary fluorescence maximum of mTHPC centered on 720 nm, and one in a region of tissue autofluorescence. The first excitation wavelength was used to excite the mTHPC and autofluorescence and the second to excite only autofluorescence, so that this could be subtracted. Subsequently, the autofluorescence-corrected mTHPC image was divided by the autofluorescence signal to correct for variations in tissue optical properties. This correction algorithm in principle results in a linear relation between the corrected fluorescence and photosensitizer concentration. The limitations of the presented method and comparison with previously published and validated techniques are discussed.
authors.affiliation: Center for Optical Diagnostics and Therapy, Department of Radiation Oncology, Erasmus Medical Center, Room Ee-1675, PO Box 2040, 3000 CA, Rotterdam, The Netherlands.
authors.forename: Slávka
authors.initials: S
authors.lastname: Kaščáková
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: de Visscher
authors.forename: Bastiaan
authors.initials: B
authors.lastname: Kruijt
authors.forename: Henriëtte S
authors.initials: HS
authors.lastname: de Bruijn
authors.forename: Angélique
authors.initials: A
authors.lastname: van der Ploeg-van den Heuvel
authors.forename: Henricus J C M
authors.initials: HJ
authors.lastname: Sterenborg
authors.forename: Max J H
authors.initials: MJ
authors.lastname: Witjes
authors.forename: Arjen
authors.initials: A
authors.lastname: Amelink
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Robinson
mesh_terms: D000465:Algorithms; D000818:Animals; D005260:Female; D005453:Fluorescence; D007259:Infrared Rays; D008652:Mesoporphyrins / Q000008:administration & dosage / Q000493:pharmacokinetics; D055620:Optical Phenomena; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D011874:Radiometry / Q000379:methods / Q000706:statistics & numerical data; D051381:Rats; D011916:Rats, Inbred F344; D012867:Skin / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism
chemical_list: D008652:Mesoporphyrins; D017319:Photosensitizing Agents; C072269:temoporfin