Lu J Y, Greenleaf J F
Dept. of Physiology and Biophys., Mayo Clinic and Found., Rochester, MN.
IEEE Trans Ultrason Ferroelectr Freq Control. 1993;40(6):735-46. doi: 10.1109/58.248218.
Conventional focused transducers have a sharp focal spot with low sidelobes, but they also have a short depth of field. Commercial medical scanners obtain increased depth of field by combining several images in a montage, each obtained at a different focal depth. Therefore, to get low sidelobes over a large depth of field several transmits must be used, which decrease the frame rate. Limited diffraction beams such as Bessel beams and X waves obtain good resolution over very large depth of field, but they have high sidelobes. A summation-subtraction method developed for decreasing the sidelobes is presented. The method requires three transmits, decreasing the frame rate to one third. The authors apply this technique to limited diffraction beams and obtain an analytic description.
传统的聚焦换能器具有旁瓣低的尖锐焦斑，但景深较短。商用医学扫描仪通过在蒙太奇中组合多个图像来增加景深，每个图像在不同的焦深处获取。因此，要在大景深上获得低旁瓣，必须使用多次发射，这会降低帧率。诸如贝塞尔光束和X波之类的有限衍射光束在非常大的景深上可获得良好的分辨率，但它们具有高旁瓣。本文提出了一种为降低旁瓣而开发的加减法。该方法需要三次发射，将帧率降低到三分之一。作者将此技术应用于有限衍射光束并获得了一个解析描述。
