Image reconstruction in thermoacoustic tomography with compensation for acoustic heterogeneities

Image reconstruction in a passive element enriched photoacoustic tomography setup

“…From this relation, we can see that given a speed of sound distribution, the relation between optical absorption A(r) and the measured pressure p(r, t) is linear. This relation has been used by the authors of other SOS compensated photoacoustic reconstruction [75,76,79,80] methods. Their approaches differ in the way that the TOF function is calculated.…”

“…Anastasio et al [75] demonstrated the reconstruction of photoacoustic measurements by assuming an a priori known speed of sound map. Using this speed of sound map, curved iso-time of flight (TOF) contours were calculated by assuming straight ray propagation of speed of sound.…”

“…Jin Zhang et al [79] use the same photoacoustic measurement function as Anastasio et al [75] to relate the optical absorption distribution and curved iso-TOF contours to the measured ultrasound signals. The speed of sound distribution was not assumed to be known a priori, however a low dimensional parametrization was used.…”

“…First we will look at the wave equation, in case of an inhomogeneous speed of sound distribution and use an approximate solution to this wave equation, exactly in accordance with [75]. The we propose a new way to calculate the time of flight values needed in the approximate solution.…”

“…Here linear ray paths are assumed so that a filtered back projection reconstruction can be used in the UTT step. Curved iso-TOF contours were then calculated using the same algorithm as Anastasio et al [75], i.e. by assuming straight ray sound propagation.…”