Filtered backprojection for thermoacoustic computed tomography in spherical geometry

Thermoacustic computed tomography (TCT) is a novel imaging technique for nondestructive evaluation and medical imaging. It uses electromagnetic energy as input and the induced thermoacoustic pressure field as measurement output. The determination of the unknown energy deposition function is based on the integral geometric problem of reconstructing a function from its integrals over certain spheres. We applay the method of approximate inverse to derive filtered backprojection type reconstruction algorithms in spherical scanning geometry. Numerical results are presented and show the validity of the resulting algorithms