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Journal of Biomedical Optics • Open Access

White light-informed optical properties improve ultrasound-guided fluorescence tomography of photoactive protoporphyrin IX

Paper Abstract

Subsurface fluorescence imaging is desirable for medical applications, including protoporphyrin-IX (PpIX)-based skin tumor diagnosis, surgical guidance, and dosimetry in photodynamic therapy. While tissue optical properties and heterogeneities make true subsurface fluorescence mapping an ill-posed problem, ultrasound-guided fluorescence-tomography (USFT) provides regional fluorescence mapping. Here USFT is implemented with spectroscopic decoupling of fluorescence signals (auto-fluorescence, PpIX, photoproducts), and white light spectroscopy-determined bulk optical properties. Segmented US images provide a priori spatial information for fluorescence reconstruction using region-based, diffuse FT. The method was tested in simulations, tissue homogeneous and inclusion phantoms, and an injected-inclusion animal model. Reconstructed fluorescence yield was linear with PpIX concentration, including the lowest concentration used, 0.025  μg/ml . White light spectroscopy informed optical properties, which improved fluorescence reconstruction accuracy compared to the use of fixed, literature-based optical properties, reduced reconstruction error and reconstructed fluorescence standard deviation by factors of 8.9 and 2.0, respectively. Recovered contrast-to-background error was 25% and 74% for inclusion phantoms without and with a 2-mm skin-like layer, respectively. Preliminary mouse-model imaging demonstrated system feasibility for subsurface fluorescence measurement in vivo. These data suggest that this implementation of USFT is capable of regional PpIX mapping in human skin tumors during photodynamic therapy, to be used in dosimetric evaluations.

Paper Details

Date Published: 12 April 2013
PDF: 11 pages
J. Biomed. Opt. 18(4) 046008 doi: 10.1117/1.JBO.18.4.046008
Published in: Journal of Biomedical Optics Volume 18, Issue 4
Show Author Affiliations
Brendan P. Flynn, Thayer School of Engineering at Dartmouth (United States)
Alisha V. DSouza, Thayer School of Engineering at Dartmouth (United States)
Stephen C. Kanick, Thayer School of Engineering at Dartmouth (United States)
Scott C. Davis, Thayer School of Engineering at Dartmouth (United States)
Brian W. Pogue, Thayer School of Engineering at Dartmouth (United States)


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