title: Monitoring blood volume and saturation using superficial fibre optic reflectance spectroscopy during PDT of actinic keratosis.
abstract: 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.
authors.affiliation: Department of Dermatology, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Tom A
authors.initials: TA
authors.lastname: Middelburg
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Kanick
authors.forename: Ellen R M
authors.initials: ER
authors.lastname: de Haas
authors.forename: Henricus J C M
authors.initials: HJ
authors.lastname: Sterenborg
authors.forename: Arjen
authors.initials: A
authors.lastname: Amelink
authors.forename: Martino H A M
authors.initials: MH
authors.lastname: Neumann
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Robinson
mesh_terms: D004058:Diffusion; D005336:Fiber Optic Technology / Q000379:methods*; D006801:Humans; D055623:Keratosis, Actinic / Q000097:blood* / Q000188:drug therapy / Q000473:pathology; D010778:Photochemotherapy / Q000379:methods*; D012031:Refractometry / Q000379:methods*; D012867:Skin / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology; D016896:Treatment Outcome