Uniqueness of reconstruction and an inversion procedure for thermoacoustic and photoacoustic tomography with variable sound speed

The paper contains an analytic reconstruction formula in thermoacoustic and photoacoustic tomography. It works for any geometry of point detectors placement along a closed surface and for variable sound speed satisfying a non-trapping condition. It is shown how this formula leads in particular to eigenfunction expansion reconstructions, including those recently obtained for the case of a uniform background. A uniqueness of reconstruction result is also obtained.