Computerized Transmission Tomography

This chapter presents the introduction application of computerized transmission tomography. The use of computerized tomography methods in medical X-rays has had a tremendous impact on the field of radiology. The transmission acoustic tomography problem is formulated as a reconstruction problem for the case of energy traveling in a straight line. The aim is to derive relationships between measurable properties of acoustic energy received after transmission through biological tissue and basic acoustic properties within the tissue. The physical basis for applying the straight-line reconstruction methods to acoustic energy propagation is derived under a set of assumptions and conditions that, when applied to the acoustic wave equation; result in mathematical relationships for the real and imaginary parts of acoustic refractive index in terms of parameters measurable from the acoustic signal received from transmission scans. It is found that fluid-flow velocity within a measurement region may be determined by transmitting and receiving acoustic energy through the measurement region along a plurality of rays such that each volume element is traversed by a set of rays having nonzero direction cosines in each direction for which flow components are to be reconstructed.