Method of and device for scanning objects by ultrasound echography

摘要

A method for the scanning of non-linearly dispersive objects whereby changes of the energy spectrum of echographic signals can be quantitatively related to parameters of the objects examined, that is to say the ultrasonic attenuation factor beta and the exponent r which characterizes the relationship between the non-linear variation of the attenuation and the frequency. To this end, the signals received are split into a number of (n) substantially equally wide, consecutive frequency bands which together cover approximately all frequencies of the signals received. The envelope of the signals in each frequency band is determined and each of the envelopes is multiplied by a correction signal in order to compensate for the diffraction effect. The logarithm of the envelopes thus corrected is determined, after which the following operations are performed by means of the n signals thus obtained: (a) the slope beta fir of each of these n signals is determined; (b) this signal beta fir is converted into logarithmic form; (c) in a table or a curve the relationship is laid down between the logarithmic value of the frequency for each channel log fi and the logarithmic value log beta fir is generated; and (d) the slope of the curve thus obtained and the value of log beta fr for log f=0 are determined.