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Journal of Biomedical Optics

Determination of the modulation transfer function for a time-gated fluorescence imaging system
Author(s): Sarah L. Gundy; Wilhelm J.M. van der Putten; Andrew Shearer; Daniel J. Buckton; Alan G. Ryder
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Paper Abstract

The use of fluorescence for cancer detection is currently under investigation. Presently, steady-state fluorescence detection methods are in use, but have limitations due to poor contrast between the fluorescence of the tumor and background autofluorescence. Improved contrast can be obtained with time-resolved techniques because of the differing lifetimes between autofluorescence and exogenous photosensitizers that selectively accumulate within tumor tissue. An imaging system is constructed using a fast-gated (200-ps) charge-coupled device (CCD) camera and a pulsed 635-nm laser diode. To characterize the ability of the system to transfer object contrast to an image, the modulation transfer function (MTF) of the system is acquired by employing an extended knife-edge technique. A knife-edge target is assembled by drilling a rectangular well into a block of polymethyl methacrylate (PMMA). The imaging system records images of the photosensitizer, chloroaluminum phthalocyanine tetrasulfonate (AlPcTS), within the well. AlPcTS was chosen to test the system because of its strong absorption of 635-nm, high fluorescence yield, and relatively long fluorescence lifetime (~7.5 ns). The results show that the system is capable of resolving 10–4 M AlPcTS fluorescence as small as 1 mm. The findings of this study contribute to the development of a time-gated imaging system using fluorescence lifetimes.

Paper Details

Date Published: 1 November 2004
PDF: 8 pages
J. Biomed. Opt. 9(6) doi: 10.1117/1.1803550
Published in: Journal of Biomedical Optics Volume 9, Issue 6
Show Author Affiliations
Sarah L. Gundy, National Univ. of Ireland/Galway (Ireland)
Wilhelm J.M. van der Putten, Univ. College Hospital (Ireland)
Andrew Shearer, National Univ. of Ireland/Galway (Ireland)
Daniel J. Buckton, GE Medical Systems (Austria)
Alan G. Ryder, National Univ. of Ireland/Galway (Ireland)


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