To establish design parameters for a transesophageal ultrasonic probe to image the left ventricle (LV) in three dimensions, the geometrical relationship between the esophagus and the heart was studied in computed tomographic sections of ten humans. Points describing the esophageal centerpoint and the left-ventricular endocardium were digitized. Algorithms were developed to determine from any esophageal viewpoint the ranges of motion required to cover the LV with four modes of scanning; transverse oblique, longitudinal oblique, rotary and linear. Longitudinal oblique scanning was the only single-degree-of-freedom method that allowed complete imaging of the LV in all patients. However, for both conventional and three-dimensional LV imaging, the most promising probe design appears to be a rotary scanning probe with an added degree of freedom to tilt the axis of rotation +/- 29 degrees away from an axis perpendicular to the local esophageal axis.
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