住野 洋一¹, 神田 良一², 高見沢 欣也², 佐々木 博², C. Waag Robert³

Yoichi SUMINO¹, Ryoichi KANDA², Kinya TAKAMIZAWA², Hiroshi SASAKI², Robert C. WAAG³

¹(秩)東芝・那須工場・超音波技術部, ²(秩)東芝・那須工場・医用機器技術研究所, ³Departments of Electrical Engineering and Radiology, University of Rochester

¹Ultrasound Systems Engineering Department, Toshiba Corporation, ²Medical Engineering Lab., Toshiba Corporation, ³Departments of Electrical Engineering and Radiology, University of Rochester

キーワード : Wavefront Distortion, Human Abdominal Wall, 2D Measurement, Degradation in Focusing, Image Quality

Time delay differences have been measured for propagation through water and through the abdominal wall of five patients. The experiment employed a curved transducer to produce a hemispherical wave pulse and a linear array to measure the resulting field along a line in a plane. Translation of the array in the direction of elevation yielded data over a two-dimensional aperture. The time delay across the aperture was calculated by adding the delay differences obtained by cross-correlating signals on adjacent elements and noting the position of the peaks. Waveform plots and the time delay difference plots together with resulting histograms and statistical data were evaluated for propagation through water and through five human abdominal walls. The results indicate that arrival time fluctuations in the presence of human abdominal wall specimens are significantly greater than those for water. Calculations of beam patterns using simulated random arrival time fluctuations also indicate that images through human abdominal walls will be out of focus in systems that operate at a frequency of approximately 3 MHz.