title: In vivo quantification of chromophore concentration using fluorescence differential path length spectroscopy.
abstract: We present an optical method based on fluorescence spectroscopy for measuring chromophore concentrations in vivo. Fluorescence differential path length spectroscopy (FPDS) determines chromophore concentration based on the fluorescence intensity corrected for absorption. The concentration of the photosensitizer m-THPC (Foscan) was studied in vivo in normal rat liver, which is highly vascularized and therefore highly absorbing. Concentration estimates of m-THPC measured by FDPS on the liver are compared with chemical extraction. Twenty-five rats were injected with 0.3 mg kg m-THPC. In vivo optical concentration measurements were performed on tissue 3, 24, 48, and 96 h after m-THPC administration to yield a 10-fold variation in tissue concentration. After the optical measurements, the liver was harvested for chemical extraction. FDPS showed good correlation with chemical extraction. FDPS also showed a correlation between m-THPC fluorescence and blood volume fraction at the two shortest drug-light intervals. This suggests different compartmental localization of m-THPC for different drug-light intervals that can be resolved using fluorescence spectroscopy. Differences in measured m-THPC concentration between FDPS and chemical extraction are related to the interrogation volume of each technique; approximately 0.2 mm(3) and approximately 10(2) mm(3), respectively. This indicates intra-animal variation in m-THPC distribution in the liver on the scale of the FDPS sampling volume.
authors: Centre for Optical Diagnostics and Therapy, Department of Radiation Oncology, Erasmus MC Room Ee1675, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
authors: Bastiaan
authors: B
authors: Kruijt
authors: Slavka
authors: S
authors: Kascakova
authors: Henriette S
authors: HS
authors: de Bruijn
authors: Angelique
authors: A
authors: van der Ploeg-van den Heuvel
authors: Henricus J C M
authors: HJ
authors: Sterenborg
authors: Dominic J
authors: DJ
authors: Robinson
authors: Arjen
authors: A
authors: Amelink
mesh_terms: D000465:Algorithms; D000818:Animals; D006651:Histocytochemistry; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008652:Mesoporphyrins / Q000032:analysis* / Q000493:pharmacokinetics; D017319:Photosensitizing Agents / Q000032:analysis* / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D013050:Spectrometry, Fluorescence / Q000379:methods*; D018709:Statistics, Nonparametric
chemical_list: D008652:Mesoporphyrins; D017319:Photosensitizing Agents; C072269:temoporfin