Abstract
Abdominal ultrasound has been used in general screening in Japan for the past 20 years, during which medical ultrasound instrumentation has rarely benefited from advanced ultrasound technology: Moderate or low-priced systems have always been used. We now need to be more aware of the operational principles of our ultrasound equipment in order to improve diagnostic confidence. We discuss technologies that show promise for this purpose. 1) Acoustic velocity adjustment: All actual ultrasound systems reconstruct ultrasound images on the assumption that ultrasound propagates through the body at a fixed velocity of 1530 to 1540 m/sec, and the discordance between actual propagation velocity in tissue and the assumed propagation velocity makes ultrasound images ambiguous. An acoustic velocity adjustment system can present many images simultaneously in a variety of ways by changing the back-ground acoustic velocity. There are two types of systems: a) one using conventional line-by-line sonography, which is expected to improve distal resolution, and b) one employing zone sonography, which is designed to increase lateral resolution. 2) Trapezoid scanning: This system widens the scanning plane. The probe is operated by applying voltage pulses to all elements in the assembly as a complete group, but with small time differences. The same time differences are used in each scan and the process is repeated. Beam direction is adjusted by slight angulation from scan to scan. Advances in computer technology have expanded the possibilities for generating uniform beamforming. Trapezoid scanning provides certain advantages, especially the ability to facilitate anatomical orientation. 3) Small devices: Advances in computer technology will expand the possibilities for minimizing instrument size without degrading image quality or image display capabilities. 4) 3D: A series of 2D images are recorded rapidly while the conventional probe is manipulated over the area of interest. 2D ultrasound images are generated while the probe is moved, and are integrated at predefined positional intervals to avoid geometric distortion. 3D ultrasound offers definite benefits, and integrated views obtained with 3D ultrasound may permit better and faster understanding of the whole structure of the abdomen and thus facilitate a more accurate diagnosis. Navigating the abdominal vessels in three orthogonal planes of a section enables the operator to facilitate correct determination of multiple planes and standardize evaluation and measurement. Conclusion. These new technologies promise to further expand the dimension and confidence of abdominal ultrasound in mass-screening.
