Multi‐modal acousto‐optic/ultrasound imaging of ex vivo liver tumors at 790 nm using a Sn₂P₂S₆ wavefront adaptive holographic setup

Abstract

Biological tissues are very strong light‐scattering media. As a consequence, current medical imaging devices do not allow deep optical imaging unless invasive techniques are used. Acousto‐optic imaging is a light‐ultrasound coupling technique that takes advantage of the ballistic propagation of ultrasound in biological tissues to access optical contrast with a millimeter resolution. We have developed a photorefractive‐crystal‐based system that performs self‐adaptive wavefront holography and works within the optical therapeutic window. As it works at an appropriate wavelength range for biological tissues imaging, it was tested on ex vivo liver samples containing tumors as a pre‐clinical study. Optical contrast was obtained even if acoustical one was not significant.

Ultrafast acousto-optic imaging with ultrasonic plane waves

“…The goal of this section is to experimentally demonstrate the capability of this method in terms of contrast and framerate. The setup used in this section is the same setup as in [6]. The AO imaging setup is coupled with a commercial US scanner (Aixplorer, SuperSonic Imagine, Aix en Provence, France).…”

“…The ultrasound probe is a commercial US transducers array (SL10-2, 192 elements, 0.2 mm pitch, SuperSonic Imagine) with a central frequency of 6 MHz. The main difference from the setup described in [6] is that the illumination and the collection of scattered light are performed thanks to optical multimode fibers, see Fig. 4.…”

“…The sample studied here is an absorbing ink inclusion embedded within a scattering gel matrix. The gel was made according to the method described in [6]. The embedding gel is Fig.…”

“…Acoustooptic (AO) imaging [2,3] is a multi-wave imaging technique [4] that couples ultrasound (US) and light in order to recover an optical contrast deep inside biological tissues with an ultrasonic resolution of few millimeters or less. AO imaging can be coupled with a commercial US scanner [5] and recently showed the first promising results concerning potential medical applications such as ex vivo results on real pathologies [6], spectroscopy sensing of blood oxygenation [7] or attempts to beat speckle decorrelation in vivo [8,9]. However, all these experiments suffer from the low imaging rate of AO imaging due to two main limitations.…”

“…Though this theoretical limit is acceptable for video rate display and thus most of in vivo applications, it is dramatically reduced by the low amount of useful signal in AO imaging and the resulting high number of averaging. This second limitation implies that images obtained at few centimeters deep in the light beam direction (z-axis) require several thousands averaging pulses for each line [5,6] so that the US firing rate requires at least few tens of seconds in order to obtain an image.…”