Photoacoustic tomography in absorbing acoustic media using time reversal

Abstract

The reconstruction of photoacoustic images typically neglects the effect of acoustic absorption on the measured time domain signals. Here, a method to compensate for acoustic absorption in photoacoustic tomography is described. The approach is based on time-reversal image reconstruction and an absorbing equation of state which separately accounts for acoustic absorption and dispersion following a frequency power law. Absorption compensation in the inverse problem is achieved by reversing the absorption proportionality coefficient in sign but leaving the equivalent dispersion parameter unchanged. The reconstruction is regularized by filtering the absorption and dispersion terms in the spatial frequency domain using a Tukey window. This maintains the correct frequency dependence of these parameters within the filter pass band. The method is valid in one, two and three dimensions, and for arbitrary power law absorption parameters. The approach is verified through several numerical experiments. The reconstruction of a carbon fibre phantom and the vasculature in the abdomen of a mouse are also presented. When absorption compensation is included, a general improvement in the image magnitude and resolution is seen, particularly for deeper features.

Unleashing Optics and Optoacoustics for Developmental Biology

“…By tracing the origin of the sound waves, tomographic methods [26,27] provide 3D images of optical absorption. Compared to light scattering of visible or NIR light, ultrasound is scattered several orders of magnitude less in tissue, resulting in depth penetration of several cm, while maintaining a resolution of $100 mm or less.…”

Compensation of Ultrasound Attenuation in Photoacoustic Imaging

“…They utilize the spatial Fourier transform to calculate the Laplacian and therefore allow for incorporating a damping of higher frequencies when calculating the time reversal. A similar algorithm to compensate acoustic attenuation step by step was proposed by (Treeby et al, 2010c) . In the second strategy, attenuation is compensated in one step where an approximation to the 'un-attenuated' measured signal is calculated from the attenuated measured signal by solving an appropriate integral equation (La Riviere et al, 2006); then an ordinary reconstruction algorithm for photoacoustic tomography is applied as in the absence of attenuation.…”

Spatial resolution and contrast enhancement in photoacoustic imaging with filter delay multiply and sum beamforming technique

“…This type of imaging is created by appling short laser pulse on biological tissues [1]. Endogenous chromophores such as oxyhaemoglobin and deoxy-haemoglobin will absorb this laser pulse [1].…”

“…Endogenous chromophores such as oxyhaemoglobin and deoxy-haemoglobin will absorb this laser pulse [1]. This leads to increasing a heat of the absorbent and generating ultrasound waves [1]. These ultrasound waves that are generated due to thermoelastic expansion of the absorbent will be detected by using ultrasound transducer.…”

“…These ultrasound waves that are generated due to thermoelastic expansion of the absorbent will be detected by using ultrasound transducer. These acoustic waves will be used to reconstruction photoacoustic image by using one of photoacoustic beamforming technique such as Time reversal, Fourier transform and Delay and sum (DAS) beamforming techniques [1]- [4]. However, DAS beamforming is the preferred method to reconstruct photoacoustic images.…”