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Proceedings Paper

Double-excitation fluorescence spectral imaging: eliminating tissue auto-fluorescence from in vivo PPIX measurements
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Paper Abstract

An ultrasound coupled handheld-probe-based optical fluorescence molecular tomography (FMT) system has been in development for the purpose of quantifying the production of Protoporphyrin IX (PPIX) in aminolevulinic acid treated (ALA), Basal Cell Carcinoma (BCC) in vivo. The design couples fiber-based spectral sampling of PPIX fluorescence emission with a high frequency ultrasound imaging system, allowing regionally localized fluorescence intensities to be quantified [1]. The optical data are obtained by sequential excitation of the tissue with a 633nm laser, at four source locations and five parallel detections at each of the five interspersed detection locations. This method of acquisition permits fluorescence detection for both superficial and deep locations in ultrasound field. The optical boundary data, tissue layers segmented from ultrasound image and diffusion theory are used to estimate the fluorescence in tissue layers. To improve the recovery of the fluorescence signal of PPIX, eliminating tissue autofluorescence is of great importance. Here the approach was to utilize measurements which straddled the steep Qband excitation peak of PPIX, via the integration of an additional laser source, exciting at 637 nm; a wavelength with a 2 fold lower PPIX excitation value than 633nm.The auto-fluorescence spectrum acquired from the 637 nm laser is then used to spectrally decouple the fluorescence data and produce an accurate fluorescence emission signal, because the two wavelengths have very similar auto-fluorescence but substantially different PPIX excitation levels. The accuracy of this method, using a single source detector pair setup, is verified through animal tumor model experiments, and the result is compared to different methods of fluorescence signal recovery.

Paper Details

Date Published: 9 March 2012
PDF: 7 pages
Proc. SPIE 8210, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXI, 82100Z (9 March 2012); doi: 10.1117/12.909031
Show Author Affiliations
Sason Torosean, Thayer School of Engineering, Dartmouth College (United States)
Brendan Flynn, Thayer School of Engineering, Dartmouth College (United States)
Kimberley S. Samkoe, Dartmouth Medical School (United States)
Scott C. Davis, Thayer School of Engineering, Dartmouth College (United States)
Jason Gunn, Thayer School of Engineering, Dartmouth College (United States)
Johan Axelsson, Thayer School of Engineering, Dartmouth College (United States)
Brian W. Pogue, Thayer School of Engineering, Dartmouth College (United States)
Dartmouth Medical School (United States)


Published in SPIE Proceedings Vol. 8210:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXI
David H. Kessel; Tayyaba Hasan, Editor(s)

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