Research Papers

Determination of the modulation transfer function for a time-gated fluorescence imaging system

[+] Author Affiliations
Sarah Gundy

National University of Ireland, Galway, National Centre for Biomedical Engineering Science, Galway, Republic of Ireland E-mail: sarah.gundy@nuigalway.ie

Wil Van der Putten

University College Hospital Galway, Department of Medical Physics and Bioengineering, Galway, Republic of Ireland

Andy Shearer

National University of Ireland, Galway, Department of Information Technology, Galway, Republic of Ireland

Daniel Buckton

National University of Ireland, Galway, Galway, Republic of Ireland

Alan G. Ryder

National University of Ireland, Galway, National Centre for Biomedical Engineering Science, Galway, Republic of Ireland

J. Biomed. Opt. 9(6), 1206-1213 (Nov 01, 2004). doi:10.1117/1.1803550
History: Received Aug. 11, 2003; Revised Jan. 23, 2004; Revised Feb. 16, 2004; Accepted Mar. 16, 2004; Online November 22, 2004
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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 104M 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. © 2004 Society of Photo-Optical Instrumentation Engineers.

© 2004 Society of Photo-Optical Instrumentation Engineers

Citation

Sarah Gundy ; Wil Van der Putten ; Andy Shearer ; Daniel Buckton and Alan G. Ryder
"Determination of the modulation transfer function for a time-gated fluorescence imaging system", J. Biomed. Opt. 9(6), 1206-1213 (Nov 01, 2004). ; http://dx.doi.org/10.1117/1.1803550


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