1 May 2006 In vivo measurement of parameters of dosimetric importance during interstitial photodynamic therapy of thick skin tumors
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J. of Biomedical Optics, 11(3), 034029 (2006). doi:10.1117/1.2204027
Abstract
A system for interstitial photodynamic therapy is used in the treatment of thick skin tumors. The system allows simultaneous measurements of light fluence rate, sensitizer fluorescence, and tissue oxygen saturation by using the same fibers as for therapeutic light delivery. Results from ten tumor treatments using δ-aminolevulinic acid (ALA)-induced protoporphyrin IX show a significant, treatment-induced increase in tissue absorption at the therapeutic wavelength, and rapid sensitizer photobleaching. The changes in oxy- and deoxyhemoglobin content are monitored by means of near-infrared spectroscopy, revealing a varying tissue oxygenation and significant changes in blood volume during treatment. These changes are consistent with the temporal profiles of the light fluence rate at the therapeutic wavelength actually measured. We therefore propose the observed absorption increase to be due to treatment-induced deoxygenation in combination with changes in blood concentration within the treated volume. A higher rate of initial photobleaching is found to correlate with a less pronounced increase in tissue absorption. Based on the measured signals, we propose how real-time treatment supervision and feedback can be implemented. Simultaneous study of the fluence rate, sensitizer fluorescence, and local tissue oxygen saturation level may contribute to the understanding of the threshold dose for photodynamic therapy.
Ann Johansson, Thomas Johansson, Marcelo Soto Thompson, Niels Bendsøe, Katarina Svanberg, Sune Svanberg, Stefan Andersson-Engels, "In vivo measurement of parameters of dosimetric importance during interstitial photodynamic therapy of thick skin tumors," Journal of Biomedical Optics 11(3), 034029 (1 May 2006). http://dx.doi.org/10.1117/1.2204027
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KEYWORDS
Optical fibers

Tissue optics

Oxygen

Absorption

Tumors

Photodynamic therapy

Tissues

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