Non-invasive, high resolution optical imaging is constantly opening exciting new possibilities for the study of cellular structure and function, both in-vivo and from excised tissue. Of the many imaging modalities available, perhaps optical coherence tomography (OCT) is finding the most applications, ranging from optical metrology and non-destructive testing to diverse biomedical applications such as cardiology, dermatology and ophthalmology. OCT is an interferometric technique with exquisite sensitivity and resolution that produces images with extremely fine structural detail. The next evolution of OCT is to combine this high spatial resolution with the ability to study dynamic processes. In this Biomedical Optics Express article by Apelian et al., a dynamic full field OCT technique (d-FFOCT) is applied to ex-vivo tissue (both murine and human) from several organs demonstrating the ability to observe subcellular metabolic processes. Moreover, this is achieved using endogenous scattering signals.
By examining the standard deviation of the CCD pixel intensities over time, decorrelation maps can be generated, and by rapid full frame acquisition (138 Hz) the dynamics of various cellular processes can be measured. To demonstrate their technique’s effectiveness, the authors describe three examples and find: (i) that glycolysis rather than aerobic respiration was the source of the decaying d-FFOCT signal measured from a liver sample over time, (ii) that various cell types (for example, liver, brain, intestine) can be differentiated based on their decorrelation spectra, and finally (iii) that cancerous and healthy tissues have different optical signatures. As discussed in the article, this last example may have significant importance in improving the surgical removal of cancerous tissue, as the surgeon could know in real time the boundaries between the healthy and cancerous regions.
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