Special Section on Photons Plus Ultrasound: Imaging and Sensing

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

[+] Author Affiliations
Dimple Modgil

The University of Chicago, Department of Radiology, 5841 South Maryland Avenue, Chicago, Illinois 60637

Mark A. Anastasio

Illinois Institute of Technology, Department of Biomedical Engineering, 3440 South Dearborn Street, Chicago, Illinois 60616

Patrick J. La Rivière

The University of Chicago, Department of Radiology, 5841 South Maryland Avenue, Chicago, Illinois 60637

J. Biomed. Opt. 15(2), 021308 (March 19, 2010). doi:10.1117/1.3333550
History: Received August 15, 2009; Revised December 16, 2009; Accepted December 17, 2009; Published March 19, 2010; Online March 19, 2010
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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.

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© 2010 Society of Photo-Optical Instrumentation Engineers

Citation

Dimple Modgil ; Mark A. Anastasio and Patrick J. La Rivière
"Image reconstruction in photoacoustic tomography with variable speed of sound using a higher-order geometrical acoustics approximation", J. Biomed. Opt. 15(2), 021308 (March 19, 2010). ; http://dx.doi.org/10.1117/1.3333550


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