Smart optical coherence tomography for ultra-deep imaging through highly scattering media

Abstract

Multiple scattering of waves in disordered media is a nightmare whether it be for detection or imaging purposes. The best approach so far to get rid of multiple scattering is optical coherence tomography. It basically combines confocal microscopy and coherence time-gating to discriminate ballistic photons from a predominant multiple scattering background. Nevertheless, the imaging depth range remains limited to 1 mm at best in human soft tissues. Here we propose a matrix approach of optical imaging to push back this fundamental limit. By combining a matrix discrimination of ballistic waves and iterative time-reversal, we show both theoretically and experimentally an extension of the imaging-depth limit by at least a factor two compared to optical coherence tomography. In particular, the reported experiment demonstrates imaging through a strongly scattering layer from which only one reflected photon over 1000 billion is ballistic. This approach opens a new route towards ultra-deep tissue imaging.

Development and Application of Optical Coherence Tomography (OCT)

“…Additionally, an important effort is being made to enable FF-OCT measurements in patients, with the recent development of two adaptive optics FF-OCT systems [169,170] for retinal imaging, a FF-OCT system coupled with an OCT system to dynamically compensate for eye motion for cornea and retina assessment, and a dark field FF-OCT system [171] to record internal fingerprints. Additionally, our group recently developed an en face matrix based approach of OCT, which allows to increase the penetration depth by a factor of two [172], and could be advantageous for in vivo experiments. Finally, we are now interested in the development of functional imaging in FF-OCT, in fresh tissues, or in living animals, either by measuring changes in the blood flow, similarly to what has been achieved in OCT [132,173], or by directly measuring changes in the tissue biomechanics, or cellular activity.…”

“…Using PS-OCT, dermal layers with different scattering and polarization properties can be observed, including stratum corneum, dermis, and epidermis ( Figure 7) [50,64,172,173]. Oral and laryngeal tissue have also been imaged by PS-OCT.…”

Full-Field Optical Coherence Tomography as a Diagnosis Tool: Recent Progress with Multimodal Imaging

“…Additionally, an important effort is being made to enable FF-OCT measurements in patients, with the recent development of two adaptive optics FF-OCT systems [169,170] for retinal imaging, a FF-OCT system coupled with an OCT system to dynamically compensate for eye motion for cornea and retina assessment, and a dark field FF-OCT system [171] to record internal fingerprints. Additionally, our group recently developed an en face matrix based approach of OCT, which allows to increase the penetration depth by a factor of two [172], and could be advantageous for in vivo experiments.…”

Collaborative effects of wavefront shaping and optical clearing agent in optical coherence tomography

“…The focusing of light into deep tissue was demonstrated using optical coherence microscopy 36 , and penetration depth enhancement was studied in a spectral domain OCT system [37][38][39] , the so-called wavefront shaping OCT (WS-OCT). The measurement of a time-resolved reflection matrix based on the principles of time-domain OCT enabled selective focusing inside tissues 40 and diffraction-limited imaging 41,42 . In a related field, wavefront shaping approaches have also been exploited for deep-tissue imaging with multi-photon microscopy 43,44 .…”