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Proceedings Paper

Photobleaching behavior of protoporphyrin IX during 5-aminolevulinic acid marked glioblastoma detection
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Paper Abstract

The highly malignant brain tumor, glioblastoma multiforme (GBM), is difficult to fully delineate during surgical resection due to its infiltrative ingrowth and morphological similarities to surrounding functioning brain tissue. Selectiveness of GBM to 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) is reported by other researchers to visualize tumor margins under blue light microscopy. To allow objective detection of GBM, a compact and portable fiber optic based fluorescence spectroscopy system is developed. This system is able to deliver excitation laser light (405 nm) in both the continuous and pulsed mode. PpIX fluorescence peaks are detected at 635 and 704 nm, using a fiber-coupled spectrometer. It is necessary to optimize the detection efficiency of the system as the PpIX quickly photobleaches during the laser illumination. A light dose of 2.5 mJ (fluence rate = 9 mJ/mm2) is experimentally approved to excite an acceptable level of fluourescence signal arising from glioblastoma. In pulsed illumination mode, an excitation dose of 2.5 mJ, with a dark interval of 0.5 s (duty cycle 50%) shows a significantly shorter photobleaching time in comparison to the continuous illumination mode with the same laser power (p < 0.05). To avoid photobleaching (the remaining signal is more than 90% of its initial value) when measuring with 2.5 mJ delivered energy, the time for continuous and pulsed illumination should be restricted to 2.5 and 1.1 s, respectively.

Paper Details

Date Published: 23 February 2009
PDF: 8 pages
Proc. SPIE 7161, Photonic Therapeutics and Diagnostics V, 716131 (23 February 2009); doi: 10.1117/12.808156
Show Author Affiliations
Neda Haj-Hosseini, Linköping Univ. (Sweden)
Johan Richter, Linköping Univ. (Sweden)
Stefan Andersson-Engels, Lund Univ. (Sweden)
Karin Wårdell, Linköping Univ. (Sweden)

Published in SPIE Proceedings Vol. 7161:
Photonic Therapeutics and Diagnostics V
Henry Hirschberg M.D.; Brian Jet-Fei Wong M.D.; Kenton W. Gregory M.D.; Reza S. Malek; Nikiforos Kollias; Bernard Choi; Guillermo J. Tearney; Justus F. R. Ilgner; Steen J. Madsen; Laura Marcu; Haishan Zeng, Editor(s)

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