Abstract
A high precision mechanical add-on module was realized to implement a transmission tomography system around a commercial analog ultrasound system. The modular nature of the add-on lets it be used, however, more universally. Without enormous effort the module could be programmed to be coupled to a fully digital high end commercial ultrasound system. A Siemens Antares was used for this work which allows the acquisition of RF data of high quality B-scans and tissue harmonic imaging (THI) over the Axius Direct Ultrasound Research Interface (URI). This possibility was exploited to explore some more intricate processing options for image compounding in addition to the conventional spatial compounding approach. Several compounding schemes were implemented. One of the two new strategies for compounding consists of calculation of a compound image from the THI data, as the latter is known to possess a better contrast and lateral resolution. While the RF data acquired from various transducer positions provides all the essential input for monostatic synthetic aperture focusing (SAFT), the other strategy was to implement SAFT imaging. The effect of inhomogeneous speed of sound was studies carefully and two different schemes were implemented to overcome the problems of image registration arising from it. The algorithms were tested on polypropylene fiber phantoms in water and ethylene glycol. While the monostatic synthetic aperture reconstruction technique was found to be best in enhancing signal to noise ratio, the speckle reduction was notably better for the THI compounding scheme than that of the conventional compounding strategy. The resulting spatial resolution of the compound images was comparable for the latter two cases and the former technique outperformed the other ones in this respect.