| In this dissertation, new inverse scattering algorithms are derived for the Helmholtz equation using the Extended Born field model (eikonal rescattered field), and the angular spectrum (parabolic) layered field model. These two field models performed the "best" of all the field models evaluated. Algorithms are solved with conjugate gradient methods. An advanced ultrasonic data acquisition system is also designed.;Many different field models for use in a reconstruction algorithm are investigated. "Layered" field models that mathematically partition the field calculation in layers in space possess the advantage that the field in layer n is calculated from the field in layer ;The Rescattered Extended Born (eikonal rescattered field) Transmission Mode (REBTM) algorithm with the AS field model and the Nonrescattered AS Reconstruction (NASR) algorithm are tested with several types of objects: a single-layer cylinder, double-layer cylinders, two double-layer cylinders and the breast model. Both algorithms, REBTM and NASR work well; however, the NASR algorithm is faster and more accurate than the REBTM algorithm. The NASR algorithm is matched well with the requirements of breast model reconstructions.;A major purpose of new scanner development is to collect both transmission and reflection data from multiple ultrasonic transducer arrays to test the next generation of reconstruction algorithms. The data acquisition system advanced features include parallel processing, automated testing strategies, and a data acquisition control language. The wave form generators provide ultrasonic beam steering/focusing and the receiver analog to digital converter channels include overall gain, time delay, and arbitrary time variable gain compensation. Overall, enough flexibility was included in the data acquisition system to compensate for transducer variations. |
