| 摘要 |
A method and system for ultrasonic imaging of bone tissue. A wide band scanning crystal transmits an ultrasonic signal of high frequency and multiple full waves into the bone tissue, and a second wide band scanning crystal receives the transmitted signal. The transmission frequency is progressively decreased until the number of full waves in the received signal equals that of the transmitted signal. At that frequency, the upper frequency limit, the number of full waves in the transmitted signal is gradually increased until the received signal contains at least two consecutive full waves of equal amplitude. The resultant transmission signal is then used to measure signal attenuation and velocity in bone tissue, in terms of standard bone imaging techniques. A lower frequency limit, below which the received signal undergoes distortion, is defined, and ultrasonic velocity depicted as a function of transmission frequency. Received ultrasonic wave frequency spectra, and the difference between the upper and lower frequency limits, are all used to image the bone tissue. Probe orientation is enhanced by a mechanism whereby a third wide band screening crystal receives the transmitted signal concomitantly with the second screening crystal. The signals received by the two wide band scanning crystals are correlated with each other to give a numerical indicator of the adequacy of probe orientation. |
