Abstract
Recently we presented novel methods for acousto-optic (AO) imaging of biological tissues, taking (1) the mean square difference of speckle patterns (subtraction method) or (2) the contrast of the summation of speckle patterns (summation method) acquired from nanosecond pulses of coherent light, fired at different ultrasound phases. In this study we relate the two methods both analytically and experimentally. We experimentally show that these two methods are nearly identical provided that the maximum achievable speckle contrast is determined correctly. We show with simulations that after correction the outcome is independent of experimental detection parameters. This makes the AO methods in this study reliable, allowing quantifying speckle observations in terms of the ultrasonically tagged fractions of light. The use of tandem nanosecond pulses in one burst of ultrasound overcomes the challenge of tissue dynamics.
Highlights
Photoacoustics (PA) and acousto-optic tomography (AOT) (Resink et al 2012) combine the use of sound and light in turbid media
To illustrate the speckle patterns obtained from the simulation, in figure 3 we show the reference and realistic case as described above of 3 speckle patterns, the first speckle pattern is obtained by adding two instantaneous speckle patterns at two opposite ultrasound phases, the second by subtraction of these phases, and the third is obtained by integration of the speckle field over a complete US cycle
The data comes from the simulated speckle pattern for the ideal case that is used as reference, the second set comes from the simulation for the more realistic case
Summary
Photoacoustics (PA) and acousto-optic tomography (AOT) (Resink et al 2012) combine the use of sound and light in turbid media. It possible to perform fluence compensated photoacoustic imaging as shown by Daoudi et al (2012) and Hussain et al (2014). In this approach, the so called ultrasonically modulated or ‘tagged’ fraction of light plays an important role. The measurements are done with the same laser system, This reduces the costs, increases acquisition speed and gives more reliable results. We have shown the possibility to perform AO imaging with a laser system suitable for PA (Resink et al 2014b), in a manner that overcomes the problem of tissue dynamics (Resink et al 2014a)
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