Limited view thermoacoustic tomography

Truncated conjugate gradient method was applied to study the limited view problem in thermoacoustic tomography, and the results were compared with those of modified backprojection method, which is the backprojection of the first order time derivative of acoustic signals. Our numerical simulations showed that there is complete data for a stable and perfect reconstruction in a 2-D π-view problem, where the least angle acquired by the detection curve is π when viewed from the imaged region of interest. On the contrary, in a problem where the view is less than π, data is incomplete, and artifacts and quantitative errors were obvious in the reconstructed images. It was pointed out that the result after one iteration in truncated conjugate gradient method is equivalent to that of modified backprojection, which can restore the high frequency information of imaged objects. The low frequency information can be recovered significantly in the next ten iterations of truncated conjugate gradient method.