Abstract
Autofluorescence spectroscopy has emerged in recent years as a powerful tool to report label-free contrast between normal and diseased tissues, both in vivo and ex vivo. We report the development of an instrument employing Single Photon Avalanche Diode (SPAD) arrays to realize real-time multispectral autofluorescence lifetime imaging at a macroscopic scale using handheld single-point fibre optic probes, under bright background conditions. At the detection end, the fluorescence signal is passed through a transmission grating and both spectral and temporal information are encoded in the SPAD array. This configuration allows interrogation in the spectral range of interest in real time. Spatial information is provided by an external camera together with a guiding beam that provides a visual reference that is tracked in real-time. Through fast image processing and data analysis, fluorescence lifetime maps are augmented on white light images to provide feedback of the measurements in real-time. We validate and demonstrate the practicality of this technique in the reference fluorophores and in articular cartilage samples mimicking the degradation that occurs in osteoarthritis. Our results demonstrate that SPADs together with fibre probes can offer means to report autofluorescence spectral and lifetime contrast in real-time and thus are suitable candidates for in situ tissue diagnostics.
Highlights
Optical spectroscopy techniques such as fluorescence, Raman or white light diffuse reflectance have been widely investigated and demonstrated potential for tissue interrogation and surgical guidance in many clinical applications[1,2,3,4,5,6,7,8,9,10]
Spectral resolution in fluorescence lifetime measurements is typically achieved using a set of dichroic mirrors and optical filters that separate the fluorescence signal in large discrete spectral bands
We extend the application of Single Photon Avalanche Diode (SPAD) arrays to single-point measurements, to realize multispectral fluorescence lifetime imaging using fibre optic probes
Summary
Optical spectroscopy techniques such as fluorescence, Raman or white light diffuse reflectance have been widely investigated and demonstrated potential for tissue interrogation and surgical guidance in many clinical applications[1,2,3,4,5,6,7,8,9,10]. This configuration determines that the spectral range and resolution of each channel are fixed and can only be modified by changing filters and/or dichroic mirrors in the detection system These instruments are typically configured to include large detection channels that overlap with spectral regions where common endogenous fluorophores emit most strongly. This strategy necessarily limits the specificity and versatility of the instrument: if additional spectral range or resolution is required, the entire detection system would have to be modified In this context, Single Photon Avalanche Diode (SPAD) arrays have emerged as attractive alternatives to common multispectral lifetime strategies, given that spectral and temporal resolution to the fluorescence measurement can be provided and adjusted at the sensor level using a fixed optical detection setup[40,41,42]. We believe this technique can provide rapid multidimensional information that could aid tissue diagnosis and could have significant impact in many clinical applications
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
