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Interstitial Fluorescence Spectroscopy in the Human Prostate During Motexafin Lutetium‐Mediated Photodynamic Therapy
Author(s) -
Finlay Jarod C.,
Zhu Timothy C.,
Dimofte Andreea,
Stripp Diana,
Malkowicz S. Bruce,
Busch Theresa M.,
Hahn Stephen M.
Publication year - 2006
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2005-10-04-ra-711
Subject(s) - photodynamic therapy , photosensitizer , fluorescence , fluorescence spectroscopy , absorption (acoustics) , prostate , chemistry , in vivo , nuclear medicine , emission spectrum , materials science , analytical chemistry (journal) , optics , spectral line , medicine , chromatography , cancer , physics , photochemistry , microbiology and biotechnology , organic chemistry , astronomy , composite material , biology
The in vivo fluorescence emission from human prostates was measured before and after motexafin lutetium (MLu)‐mediated photodynamic therapy (PDT). A single side‐firing optical fiber was used for both the delivery of 465 nm light‐emitting diode excitation light and the collection of emitted fluorescence. It was placed interstitially within the prostate via a closed transparent plastic catheter. Fitting of the collected fluorescence emission spectra using the known fluorescence spectrum of 1 mg/kg MLu in an intralipid phantom yields a quantitative measure of the local MLu concentration. We found that an additional correction factor is needed to account for the reduction of the MLu fluorescence intensity measured in vivo due to strong optical absorption in the prostate. We have adopted an empirical correction formula given by C = (3.1 cm −1 /μ′ s ) exp (μ eff · 0.97 cm), which ranges from approximately 3 to 16, with a mean of 9.3 ± 4.8. Using a computer‐controlled step motor to move the probe incrementally along parallel tracks within the prostate we can determine one‐dimensional profiles of the MLu concentration. The absolute MLu concentration and the shape of its distribution are confirmed by ex vivo assay and by diffuse absorption measurements, respectively. We find significant heterogeneity in photosensitizer concentration within and among five patients. These variations occur over large enough spatial scales compared with the sampling volume of the fluorescence emission that mapping the distribution in three dimensions is possible.