  An inverse problem of the determination of an initial condition in a
hyperbolic equation from the lateral Cauchy data is considered. This problem
has applications to the thermoacoustic tomography, as well as to linearized
coefficient inverse problems of acoustics and electromagnetics. A new version
of the quasi-reversibility method is described. This version requires a new
Lipschitz stability estimate, which is obtained via the Carleman estimate.
Numerical results are presented.
