Greenleaf J F, Gisvold J J, Bahn R C
Med Prog Technol. 1982;9(2-3):165-70.
Beginning with the wave equation, we have derived the classic reconstruction equations, which assume the ultrasonic energy travels in a straight line. The straight line reconstruction methods result in images that are not absolutely quantitative, although they may be useful in delineating speed and attenuation within two-dimensional cross sections, especially in organs such as the breast. Aberrations associated with straight-line reconstruction images are results of the effects of refraction and of diffraction. In addition, these methods assume that the acoustic wave travels within a plane and not in three dimensions; thus the assumed dimensionality of the problem also gives aberrations in the final image. The effects of diffraction are very complex and, given the current methods of measuring arrival time and amplitude, cause aberrations in the image, which result in errors both in geometry and in magnitude of the reconstructed values. Correction of diffraction effects with techniques termed 'diffraction tomography' are being investigated and have resulted in some preliminary data.
从波动方程出发，我们推导出了经典的重建方程，这些方程假设超声能量沿直线传播。直线重建方法得到的图像并非绝对定量，尽管它们在描绘二维横截面内的速度和衰减方面可能有用，尤其是在乳腺等器官中。与直线重建图像相关的像差是折射和衍射效应的结果。此外，这些方法假设声波在平面内传播而非三维传播；因此，问题的假设维度也会在最终图像中产生像差。衍射效应非常复杂，鉴于当前测量到达时间和幅度的方法，会导致图像出现像差，从而在重建值的几何形状和大小上都产生误差。正在研究用称为“衍射层析成像”的技术来校正衍射效应，并已得到了一些初步数据。
