Journal of Ultrasound in Medicine, Vol 8, Issue 12 675-683, Copyright © 1989 by American Institute of Ultrasound in Medicine
Completely computer-focused ultrasound imaging. First clinical imaging results
J. Koivukangas, O. Tervonen, E. Alasaarela, J. Ylitalo and S. Nystrom
Department of Neurosurgery, University of Oulu, Finland.
Completely computer-focused ultrasound imaging has been achieved using the
UHB (ultrasound holographic B) method. This is a synthetic aperture method
that combines ultrasonic holography and the conventional B-scan method. A
wide-angle ultrasound burst (4 MHz) is transmitted into the object and the
reflected echoes are measured as a function of the propagation time, but
both the amplitude and phase angle are recorded, giving multiple
one-dimensional holograms in a cross-sectional plane. This UHB data is
rearranged to obtain one-dimensional wave fields, which represent the wave
fronts reflected from each depth. The image is then reconstructed by
propagating these wave fields backward to their original positions on the
image using Fourier transform, a spectrum shift theorem, and inverse
Fourier transform. The whole UHB image is obtained by calculating the
intensity lines from these wave fields and by scanning these lines one by
on the cathode ray tube (CRT) monitor. Following extensive laboratory
testing with single and multielement transducers, special 32- and
64-element linear array transducers were fabricated, as was computer
software capable of producing a UHB image in 40 seconds. Tissue imaging
tests followed by clinical imaging of 30 patients showed that images
obtained with this prototype compared favorably with those obtained by
state-of-the-art conventional ultrasound scanners. The potential advantages
of the new method are enhanced lateral resolution and the incorporation of
phase information in tissue characterization. This would be important in
diagnostic and intraoperative, especially neurosurgical, imaging.
