Correcting photoacoustic signals for fluence variations using acousto-optic modulation

Abstract

We propose a strategy for quantitative photoacoustic mapping of chromophore concentrations that can be performed purely experimentally. We exploit the possibility of acousto-optic modulation using focused ultrasound, and the principle that photons follow trajectories through a turbid medium in two directions with equal probability. A theory is presented that expresses the local absorption coefficient inside a medium in terms of noninvasively measured quantities and experimental parameters. Proof of the validity of the theory is given with Monte Carlo simulations.

Fast acousto-optic tissue sensing with tandem nanosecond pulses

“…This method we call Sound Light and combines photo acoustics with acousto-optics. Proof-ofconcept experiments of Sound Light have been given in transmission and reflection mode [7,8].…”

“…[17,104] Both methods can be combined to achieve fluence compensated PA imaging [7,8]. While PA already has in vivo applications, AO still suffers from so called speckle decorrelation when applied in vivo, which typically results in no or poor signals.…”

“…A major challenge towards quantification of optical absorption is to compensate the signal strength of photoacoustics for local fluence variations. Recently fluence compensation of PA signals was proposed by using acousto-optic (AO) imaging [17,104] in combination with PA [7]. This method relies on the principle that both PA and AO signal strength depend on the local fluence.…”

“…Daoudi et al [7] and Hussain et al [8] demonstrated that the combination of both techniques makes it possible to perform fluence compensated photoacoustic measurements, opening the possibility of quantitative measurements of the optical absorption coefficient. In the underlying algorithm, the detected amount of ultrasonically tagged light is an important quantity.…”

“…The combination of PA and AOT measurements makes it possible to perform fluence compensated photoacoustic imaging as shown by Daoudi et al [7] and Hussain et al [111]. In this approach, the so called ultrasonically modulated or 'tagged' fraction of light plays an important role.…”