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4 March 2013Model-based tomographic optoacoustic reconstruction in media with small speed of sound variations
The majority of optoacoustic reconstruction algorithms are based on the assumption that the speed of sound
within the imaging sample is constant and equal to the speed of sound in the coupling medium, typically water.
However, small speed of sound changes between different organs and structures are common in actual samples.
The variations in the speed of sound within biological tissues are usually below 10% with respect to the speed
of sound in water. Under these circumstances, the acoustic wave propagation can be modeled as acoustic rays
and the main effect of the acoustic heterogeneities is the time-shifting of the optoacoustic signals. Herein, we
describe a model-based reconstruction algorithm capable of accounting for such small speed of sound variations.
It is based on modifying the integration curve in the forward optoacoustic model according to the time-shifting
produced by differences in the speed of sound. The forward model is then discretized and inverted algebraically
by means of the LSQR algorithm. The algorithm was tested experimentally with tissue-mimicking agar phantoms
containing glycerine to simulate a higher speed of sound than water. The improvement in the image quality as
compared to the results obtained by assuming a uniform speed of sound is discussed in this work.
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X. Lúis Deán-Ben, Vasilis Ntziachristos, Daniel Razansky, "Model-based tomographic optoacoustic reconstruction in media with small speed of sound variations," Proc. SPIE 8581, Photons Plus Ultrasound: Imaging and Sensing 2013, 85813U (4 March 2013); https://doi.org/10.1117/12.2004964