QUANTITATION OF FINE DISPLACEMENT IN ECHOGRAPHY

A High-speed Digital Subtraction Echography was developed to visualize the fine displacement of human internal organs. This method indicates differences in position through time series images of high-frame-rate echography. Fine displacement less than ultrasonic wavelength can be observed. This method, however, lacks the ability to quantitatively me asure displacement length. The subtraction between two successive imag es was affected by displacement direction in spite of the displacement length being the same. To solve this problem, convolution of an echog ram with Gaussian distribution was used. To express displacement lengt h as brightness quantitatively, normalization using a brightness gradi ent was applied. The quantitation algorithm was applied to successive B-mode images. Compared to the simply subtracted images, quantitated i mages express more precisely the motion of organs. Expansion of the ca rotid artery and fine motion of ventricular walls can be visualized mo re easily. Displacement length can be quantitated with wavelength. Und er more static conditions, this system quantitates displacement length that is much less than wavelength.