Image reconstruction in photoacoustic tomography with variable speed of sound using a higher-order geometrical acoustics approximation

Dimple Modgil, Mark A. Anastasio, Patrick J La Rivière

Research output: Contribution to journalArticle

Abstract

Previous research correcting for variable speed of sound in photoacoustic tomography (PAT) based on a generalized radon transform (GRT) model assumes first-order geometrical acoustics (GA) approximation. In the GRT model, the pressure is related to the optical absorption, in an acoustically inhomogeneous medium, through integration over nonspherical isochronous surfaces. Previous research based on the GRT model assumes that the path taken by acoustic rays is linear and neglects amplitude perturbations to the measured pressure. We have derived a higher-order GA expression that takes into account the first-order effect in the amplitude of the measured signal and higher-order perturbation to the travel times. The higher-order perturbation to travel time incorporates the effect of ray bending. Incorrect travel times can lead to image distortion and blurring. These corrections are expected to impact image quality and quantitative PAT. We have previously shown that travel-time corrections in 2-D suggest that perceivable differences in the isochronous surfaces can be seen when the second-order travel-time perturbations are taken into account with a 10% speed-of-sound variation. In this work, we develop iterative image reconstruction algorithms that incorporate this higher-order GA approximation assuming that the speed of sound map is known. We evaluate the effect of higher-order GA approximation on image quality and accuracy.

Original languageEnglish (US)
Article number021308
JournalJournal of biomedical optics
Volume15
Issue number2
DOIs
StatePublished - Dec 1 2010
Externally publishedYes

Keywords

  • Geometrical acoustics
  • Image reconstruction
  • Inhomogeneous
  • Optoacoustic tomography
  • Photoacoustic tomography
  • Thermoacoustic tomography
  • Travel times
  • Variable speed of sound

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Biomaterials
  • Biomedical Engineering

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