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Background. To optimize photodynamic therapy (PDT) and photodetection of cancer, two important variables that must be considered are the uptake of the dye and the dye contrast between normal and neoplastic tissue after injection. Methods. To study these variables in a clinical context, an apparatus based on a noninvasive optical fiber that detects the dye by light-induced fluorescence (LIF) was constructed. Results. Studies on the pharmacokinetics of the fluorescent fraction of Photofrin in patients with early squamous cell carcinoma in the oral cavity, esophagus or bronchi show a signal contrast ranging from 1.5 to 3.5 a short time after intravenous injection that rapidly decreases and tends to unity (one) about 12 hours later. The magnitude of this contrast appears to correlate with the staging of the cancer, the more invasive tumors showing the highest contrast. The more invasive tumors also show the highest uptake. The oral cavity pharmacokinetics are similar to those found in the esophagus and the bronchi. Conclusions. The oral cavity appears to be a good model, with easy access for optimizing photodetection and PDT in the esophagus and the bronchi. These pharmacokinetics can be used directly for optimizing photodetection. However, complementary information on the detailed localization of the drug by fluorescence microscopy and a correlation of these data with tumor necrosis efficacy are necessary to optimize PDT timing and therapeutic gain Cancer 1995; 75:2768-78.

A non-invasive probe has been devised and clinically used to perform in vivo measurements of the optical properties of the esophageal wall and oral cavity. The absorption and reduced scattering coefficients are determined from the observation of the spatial distribution of the diffuse reflectance at the tissue surface under a narrow beam illumination of the tissue. The determination of these two coefficients enables us to evaluate the value of the effective attenuation coefficient which is of major interest in the field of light dosimetry for photodynamic therapy (PDT). An invasive isotropic micro-probe has also been designed and clinically used to directly measure in vivo the value of the fluence rate in tissues. The principle of this probe is based on the fluorescence generated in a ruby sphere by the light which propagates in the tissue. This fluorescence which can be excited between 350 and 680 nm is isotropically emitted and in part collected by an optical fiber glued against the ruby sphere. Results, obtained with both probes at 514 and 630 nm, i.e., wavelengths of interest in photodynamic therapy, with actual clinically used photosensitizers are summarized and compared. The agreement obtained between these two techniques validates the principle of these measurements.