  Photoacoustic imaging has shown great promise for medical imaging, where
optical energy absorption by blood haemoglobin is used as the contrast
mechanism. A numerical method was developed for the in-silico assessment of the
photoacoustic image reconstruction of the brain. Image segmentation techniques
were used to prepare a digital phantom from MR images. Light transport through
brain tissue was modelled using a Finite Element approach. The resulting
acoustic pressure was then estimated by pulsed photoacoustics considerations.
The forward acoustic wave propagation was modelled by the linearized coupled
first order wave equations and solved by an acoustic k-space method. Since
skull bone is an elastic solid and strongly attenuates ultrasound (due to both
scattering and absorption), a k-space method was developed for elastic media.
To model scattering effects, a new approach was applied based on propagation in
random media. In addition, absorption effects were incorporated using a power
law. Finally, the acoustic pressure was reconstructed using the k-space time
reversal technique. The simulations were ran in 3D to produce the photoacoustic
tomogram of a brain tumour. The results demonstrate the convergence of the
models, and their suitability for investigating the photoacoustic imaging
process.
