Photodynamic therapy (PDT) for Actinic Kertoses (AK) using aminoluvelinic acid (ALA) is an FDA-approved treatment,
which is generally effective, yet response rates vary. The origin of the variability is not well characterized, but may be
related to inter-patient variability in the production of protoporphyrin IX (PpIX). While fiber-based point probe systems
provide a method for measuring PpIX production, these measurements have demonstrated large spatial and inter-operator
variability. Thus, in an effort to improve patient-specific dosimetry and treatment it is important to develop a robust system
that accounts for spatial variability and reduces the chance of operator errors. To address this need, a wide-field
multispectral imaging system was developed that is capable of quantifying maps of PpIX in both liquid phantoms and in
vivo experiments, focusing on high sensitivity light signals. The system uses both red and blue excitation to elicit a
fluorescent response at varying skin depths. A ten-position filter wheel with bandpass filters ranging from 635nm to 710nm
are used to capture images along the emission band. A linear least-square spectral fitting algorithm provides the ability to
decouple background autofluorescence from PpIX fluorescence, which has improved the system sensitivity by an order of
magnitude, detecting nanomolar PpIX concentrations in liquid phantoms in the presence of 2% whole blood and 2%
Ethan P. M. LaRochelle, Scott C. Davis, Ana Luiza Ribeiro de Souza, and Brian W. Pogue, "In vivo wide-field multispectral dosimeter for use in ALA-PpIX based photodynamic therapy of skin," Proc. SPIE 10047, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVI, 1004707 (Presented at SPIE BiOS: January 28, 2017; Published: 8 February 2017); https://doi.org/10.1117/12.2252402.
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