| abstract |
An ultrasound imaging system employs acoustic impedance reconstruction to produce high-resolution images of anatomical structures, which are virtually free of speckle. Determination of the acoustic impedance profile involves prefiltering of the incident ultrasound signal and the ultrasound signal reflected from the specimen to be imaged. A time domain window function is applied to both the incident and reflected signals, and an N-point FFT is computed for both the digitized incident and reflected signals to obtain the incident and reflected spectrums. A complex division of the reflected spectrum by the incident spectrum is performed to obtain the transfer function. A window function having a sharp, low-frequency cutoff is applied to the transfer function prior to performing an inverse FFT to obtain the estimated impulse response. The acoustic impedance of individual A-scans is calculated from the impulse response using the plane wave Born approximation, involving integration and exponentiation of the estimated impulse response. By mechanically or electronically scanning the transducer along a line, a series of A-scan acoustic impedance profiles are calculated and used to produce a two-dimensional, grey-scale B-scan image. |