Ultrasound velocity tomography, an imaging method

Analysis of the geometry of the beating heart may yield important information about its condition and function, and may reveal physiologically and clinically relevant information about the influence of regional malfunctioning on the integral heart performance. In this study, a method has been developed which will ultimately allow the determination of the three-dimensional geometry of an isolated working dog-heart throughout the cardiac cycle. The technique will be called 'ultrasound velocity tomography'. Ultrasound velocity tomograms are reconstructions of the spatial distribution of the ultrasound velocity in cross-sections of the object under study. This velocity is to a certain extent characteristic for a tissue, so that various tissues and structures can be identified in a tomogram. The velocities are mathematically reconstructed from thousands of measured times-of-flight of ultrasound pulses which have travelled along different path-ways through the object. By detecting the blood-heart muscle transitions in a tomogram and by combining tomograms from different cross-sections of the heart, a three-dimensional heart-geometry may be obtained. Preliminary results on a formalin-fixed heart are shown and discussed.