Algebraic reconstruction technique considering curved ray for sound-speed tomography with ring-array transducer

Our objective is to develop an ultrasound treatment and diagnosis integrated system for breast cancer. Ultrasound computed tomography (UCT) in imaging and high intensity focused ultrasound (HIFU) in therapy was integrated to achieve ideal treatment system. Profiles of sound speed and attenuation obtained by UCT has informative parameters to correct deformation of HIFU beam. We try to develop an imaging system using ring-array transducer with 1024-elements, multiplexer connecting 1024 to 256 and Verasonics programmable imaging system with 256 channels. First, an iterative Simultaneous Algebraic Reconstruction Technique (SART) reconstruction methods with an assumption of straight path was employed. SART was applied to projection data calculated by a FEM simulator treating actual curved ray caused by tissue inhomogeneity. In these results, estimated error in sound speed difference was 53%. Then we introduced Linear Travel-time Interpolation (LTI) to SART to implement effects of curved ray. LTI is a ray tracing method based on Fermat’s Principle. We evaluated the LTI and SART integrated method for sound-speed tomography. Travel-time for reconstruction was achieved from simulation based on finite difference method. The reconstruction image was highly corresponded with original image. Reconstructed image from experimental projection data will be reported in the presentation.