Numerical modeling of photoacoustic imaging of brain tumors.

Abstract

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 has been 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. Then, light transport through brain tissue was modeled using the finite element approach. The resulting acoustic pressure was then estimated by pulsed photoacoustics considerations. The forward acoustic wave propagation was modeled by linearized coupled first order wave equations and solved by the acoustic k-space method. Since skull bone is an elastic solid and strongly attenuates ultrasound (due to scattering and absorption), a k-space method was developed for elastic media. To model scattering effects, a new approach was introduced 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 run in three dimensions to produce the photoacoustic tomogram of a brain tumor. The results show that relying on optical energy absorption by blood hemoglobin as the contrast mechanism, as is the current practice, leads to poor image quality.