Optically monitoring the vascular physiology during photodynamic therapy (PDT) may help understand patient-specific treatment outcome. However, diffuse optical techniques have failed to observe changes herein, probably by optically sampling too deep. Therefore, we investigated using differential path-length spectroscopy (DPS) to obtain superficial measurements of vascular physiology in actinic keratosis (AK) skin. The AK-specific DPS interrogation depth was chosen up to 400 microns in depth, based on the thickness of AK histology samples. During light fractionated aminolevulinic acid-PDT, reflectance spectra were analyzed to yield quantitative estimates of blood volume and saturation. Blood volume showed significant lesion-specific changes during PDT without a general trend for all lesions and saturation remained high during PDT. This study shows that DPS allows optically monitoring the superficial blood volume and saturation during skin PDT. The patient-specific variability supports the need for dosimetric measurements. In DPS, the lesion-specific optimal interrogation depth can be varied based on lesion thickness.

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doi.org/10.1002/jbio.201100053, hdl.handle.net/1765/34623
Journal of Biophotonics
Erasmus MC: University Medical Center Rotterdam

Middelburg, T., Kanick, S., de Haas, E., Sterenborg, D., Amelink, A., Neumann, M., & Robinson, D. (2011). Monitoring blood volume and saturation using superficial fibre optic reflectance spectroscopy during PDT of actinic keratosis. Journal of Biophotonics, 4(10), 721–730. doi:10.1002/jbio.201100053