The effects of acoustic attenuation in optoacoustic signals

Abstract

In this paper, it is demonstrated that the effects of acoustic attenuation may play a significant role in establishing the quality of tomographic optoacoustic reconstructions. Accordingly, spatially dependent reduction of signal amplitude leads to quantification errors in the reconstructed distribution of the optical absorption coefficient while signal broadening causes loss of image resolution. Here we propose a correction algorithm for accounting for attenuation effects, which is applicable in both the time and frequency domains. It is further investigated which part of the optoacoustic signal spectrum is practically affected by those effects in realistic imaging scenarios. The validity and benefits of the suggested modelling and correction approaches are experimentally validated in phantom measurements.

Photoacoustic computed tomography correcting for heterogeneity and attenuation

“…These results confirm that, for the object studied, the SOS and mass density heterogeneities can influence the reconstructed image more strongly than acoustic attenuation. 17 However, as expected, Fig. 3(d) reveals that compensation for both SOS and density heterogeneities along with acoustic attenuation yields the image that possesses the best spatial resolution.…”

“…However, relatively few tomographic reconstruction algorithms are available for such compensation for acoustic attenuation. [12][13][14][15][16][17] Moreover, all of the previously investigated methods have assumed that the acoustic attenuation properties of the object are homogeneous. An important biomedical application in which that assumption will be grossly violated is transcranial PCT, 18 in which the models of acoustic attenuation in soft-tissue and skull bone have distinct forms.…”

Acoustic attenuation compensation in photoacoustic tomography using time-variant filtering

“…A similar approach has recently been used for attenuation compensation when photoacoustic waves propagate through an absorbing layer of known thickness. 15,26,27 However, since d is fixed, this procedure is not suitable when the image features are positioned in an absorbing medium at varying distances from the receiver (as is most often the case in practice). In this case, signals arising from features shallower than the chosen d will be overcompensated, and signals from deeper features will be undercompensated.…”

“…These effects were first noted shortly after experimental photoacoustic systems began to appear in the late 1990s, 12 and they have since been studied by a number of authors. [13][14][15][16] For a given measurement sensitivity, the attenuation dictates the maximum frequency that can be detected from a broadband photoacoustic source located at a particular depth within the tissue. 6 This in turn dictates the maximum achievable resolution in the reconstructed image.…”

All-optical photoacoustic projection imaging

“…In contrast to imaging modalities relying on reflected or transmitted light, the image resolution in PAT is not affected by the scattering of light in biological tissue and, therefore, offers high spatial resolution in relatively large imaging depths. The achievable resolution is limited by acoustic attenuation [2][3][4] and depends on the imaging depth. By a rule of thumb, the minimal spatial resolution is in the order of 1/200 of the imaging depth [5].…”