Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - COHERENCE (Exploiting light coherence in photoacoustic imaging)

Teaser

Photoacoustic imaging is an emerging multi-wave imaging modality that couples light excitation to acoustic detection, via the photoacoustic effect (sound generation via light absorption). Photoacoustic imaging provides images of optical absorption (as opposed to optical...

Summary

Photoacoustic imaging is an emerging multi-wave imaging modality that couples light excitation to acoustic detection, via the photoacoustic effect (sound generation via light absorption). Photoacoustic imaging provides images of optical absorption (as opposed to optical scattering).

As photoacoustic imaging relies on detecting ultrasound waves that are very weakly scattered in biological tissue, it can provide acoustic-resolution images of optical absorption non-invasively at large depths (up to several cm), where purely optical techniques have a poor resolution because of multiple scattering. As for conventional purely optical approaches, optical-resolution photoacoustic microscopy can also be performed non-invasively for shallow depth (< 1 mm), or invasively at depth by endoscopic approaches. However, photoacoustic imaging suffers several limitations. For imaging at greater depths, non-invasive photoacoustic imaging in the acoustic-resolution regime is limited by a depth-to-resolution ratio of about 100, because ultrasound attenuation increases with frequency. Optical-resolution photoacoustic endoscopy has very recently been introduced as a complementary approach, but is currently limited in terms of resolution (> 6 μm) and footprint (diameter > 2 mm).

The overall objective of COHERENCE is to break the above limitations and reach diffraction-limited optical-resolution photoacoustic imaging at depth in tissue in vivo. To do so, the core concept of COHERENCE is to use and manipulate coherent light in photoacoustic imaging. Specifically, COHERENCE will develop novel methods based on speckle illumination, wavefront shaping and super-resolution imaging. COHERENCE will result in two prototypes for tissue imaging, an optical-resolution photoacoustic endoscope for minimally-invasive any-depth tissue imaging, and a non-invasive photoacoustic microscope with enhanced depth-to-resolution ratio, up to optical resolution in the multiply-scattered light regime.

In terms of impact for the society, COHERENCE leads to the design of innovative biomedical instrumentations aiming at seeing deeper and better through organs, and therefore participates to the development of new diagnostic tools.

Work performed

Developement of a 3D acoustic-resolution photoacoustic imaging device, allowing 3D hig-resolution imaging of blood vasculature at depth in biological tissue.

Developement of two laboratory setup to investigate optical-resolution photoacoustic microscopy through minimally invasive fibers.

Demonstration of hybrid fluorescence/photoacoustic endomicroscpy on test samples in vitro.

Final results

We expect to provide two novel prototypes for non-invasive super-acoustic-resolution photoacoustic imaging and for minimally invasive photoacoustic endomicroscopy