Abstract
Multimodal imaging probes a variety of tissue properties in a single image acquisition by merging complimentary imaging technologies. Exploiting synergies amongst the data, algorithms can be developed that lead to better tissue characterization than could be accomplished by the constituent imaging modalities taken alone. The combination of optical coherence tomography (OCT) with fluorescence lifetime imaging microscopy (FLIM) provides access to detailed tissue morphology and local biochemistry. The optical system described here merges 1310 nm swept-source OCT with time-domain FLIM having excitation at 355 and 532 nm. The pulses from 355 and 532 nm lasers have been interleaved to enable simultaneous acquisition of endogenous and exogenous fluorescence signals, respectively. The multimodal imaging system was validated using tissue phantoms. Nonspecific tagging with Alexa Flour 532 in a Watanbe rabbit aorta and active tagging of the LOX-1 receptor in human coronary artery, demonstrate the capacity of the system for simultaneous acquisition of OCT, endogenous FLIM, and exogenous FLIM in tissues.
Highlights
Pathological changes in a tissue are accompanied by alterations in morphology and biochemistry
In order to assess the performance of the Optical Coherence Tomography (OCT)/fluorescence lifetime imaging microscopy (FLIM) system, we imaged 3 parallel, coplanar quartz capillary tubes, each filled with a different fluorophore and submerged in diluted milk as a scattering medium. 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP) and Nicotinamide Adenine Dinucleotide (NADH) fluoresce efficiently at 400 nm and 500 nm, respectively, when excited at 355 nm
Judicious choices of the sampling in the image acquisition ensured that the FLIM images are coregistered with each other and the OCT volume image
Summary
Pathological changes in a tissue are accompanied by alterations in morphology and biochemistry. These alterations are accompanied by changes in the tissue optical properties, e.g. scattering coefficient, distribution of scatterers, absorption coefficient, and fluorescence. Taking advantage of such phenomena, optical imaging systems have been used to establish biomarkers of disease and characterize stages of disease for diagnosis. This “optical biopsy” is advantageous when it is not possible to biopsy the suspect tissue or when the area is so large that sampling error associated with traditional biopsy is unacceptable. The collective information generated with multi-modal systems has been shown to improve sensitivity and specificity in the analysis of diseased tissues [1,2,3,4]
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