A high-speed multi-channel time -correlated system for fluorescence lifetime imaging

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" A high-speed multi-channel time -correlated system for fluorescence lifetime imaging "
Muhammad Z. Nazir J. G. White

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	53322
Doc. No	:	TL23276
Call number	:	‭3278945‬
Main Entry	:	Muhammad Z. Nazir
Title & Author	:	A high-speed multi-channel time -correlated system for fluorescence lifetime imaging\ Muhammad Z. Nazir
College	:	The University of Wisconsin - Madison
Date	:	2007
Degree	:	Ph.D.
student score	:	2007
Page No	:	119
Abstract	:	Laser-scanning microscopy (LSM) has become a standard technique for biomedical imaging at the cellular and sub-cellular level. LSM is not only widely used as a powerful biological imaging tool but also as a research platform for investigating new imaging modalities. However, emerging techniques and new functionality cannot be readily incorporated into a proprietary laser scanning microscope because of inaccessibility to proprietary source code and hardware. We present a system called WiscScan where the scanning engine, data acquisition system and associated software were all replaced with a flexible, extensible system that consisted of an off-the-shelf programmable DSP card, its peripherals, and modular interface software. The approach enabled us to incorporate emerging novel techniques such as fluorescence lifetime imaging and other functionality to the microscope when required. Time-Correlated Single Photon Counting is a time-domain technique for fluorescence lifetime measurements where the time between fluorophore excitation and photon arrival is directly measured. However, most commercial instruments use Time-to-Amplitude Converters for time measurements. These circuits exhibit a dead time of 100 nsec which limits the count rate of the system and hence its scan speed. We have used Time-to-Digital Converters in our fluorescence lifetime imaging system which exhibit twenty times less dead-time. Moreover, multiple parallel measurement channels were used to route photons of different color to different channels. This differentiation on the basis of color (spectra) makes it easier to apply curve fitting algorithms for accurate lifetime extraction. Hence, the combined use of short dead-times and multiple channels led to a high count rate system, which is essential for tracking the functional dynamics of the living organisms.
Subject	:	Applied sciences; Fluorescence lifetime imaging; Laser-scanning microscopy; Photon counting; Time-correlated; Biomedical research; Electrical engineering; 0541:Biomedical research; 0544:Electrical engineering
Added Entry	:	J. G. White
Added Entry	:	The University of Wisconsin - Madison