Fluorescence Lifetime Spectroscopy (FLS) enables label-free characterization of tissues using their spectral and temporal fluorescence signature. Time-domain FLS using pulse sampling is fast and not affected by external illumination and is, therefore, a great candidate for real-time surgical guidance and other inpatient applications. As currently implemented by our group, fluorescence lifetime data acquisition is performed by a single fast micro-channel plate (MCP) detector and digitizer, where the simultaneous recording of fluorescence decays in multiple spectral bands is achieved by temporal multiplexing of the different wavelength bands using increasing lengths of delay fibers. In this current form, instrumentation costs limit the use of the system for point of care applications and the ability to run multicenter studies. Furthermore, MCPs are prone to damage by excessive current or vibrations and require high voltage supplies. Here, we propose to interface fast, inexpensive Si photodetectors and amplifiers (60 dB) with each optical channel. Signal obtained from each spectral band is then sampled with a DRS4 switched capacitor array waveform digitizing chip (500 MHz bandwidth, 5 GS/s). In this compact, much lower cost instrument, the signal amplitude is matched to the A/D dynamic range for each individual channel using inexpensive RF digital step attenuators. Additionally, the signal intermodal dispersion in the delay fibers is eliminated. The influence of the decreased analog bandwidth and increased noise of this new instrument will be evaluated experimentally and compared with state-of-the-art pulse sampling FLS instrumentation.
Diego Yankelevich, Julien Bec, Jonathan D. Wapman, and Laura Marcu, "Multichannel solid state photodetection system for low-cost fluorescence lifetime spectroscopy
(Conference Presentation)," Proc. SPIE 10484, Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XVI, 104840H (Presented at SPIE BiOS: January 29, 2018; Published: 5 April 2018); https://doi.org/10.1117/12.2291180.5751458143001.
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