Browsing by Subject "Phase aberration correction"

Now showing 1 - 3 of 3

Open Access
Digital beamforming techniques and VLSI circuits for medical ultrasound imaging
(1992) Karaman, Mustafa
For phased array medical ultrasound imaging, digital beamforming techniques and VLSI circuits are studied to form a fully digital receive front-end hardware. To increase the timing accuracy in beamforming, a computationally efficient upsampling schme is examined. A digital beamforming method based on receive focusing at the raster focal points is proposed. The sector images of the resolution phantom, reconstructed from the phased array experimental data by beamforming at the radial and raster focal points, are presented for comparison of the image resolution performance of the two beamforming schemes. For adaptive beamforming, a phase aberration correction technique with very low computational complexity is described. Image quality performance of the technique is examined by digitally processing the non-aberrated and aberrated phased array experimental data sets of an ultrasound resolution phantom. VLSI circuits and their implementations for the proposed techniques are presented.
Open Access
A phase aberration correction method for ultrasound imaging
(IEEE, 1993) Karaman, M.; Atalar, Abdullah; Köymen, Hayrettin; O'Donnell, M.
A computationally efficient method for phase aberration correction in ultrasound imaging is presented. The method is based on time delay estimation via minimization of the sum of absolute differences between radio frequency samples of adjacent array elements. Effects of averaging estimated aberration patterns over scan angles, and truncation to a single bit wordlength are examined. Phase distortions due to near-field inhomogeneities are simulated using silicone rubber aberrators. Performance of the method is tested using experimental data. Simulation studies addressing different factors affecting efficiency of the method, such as the number of iterations, window length, and the number of scan angles used for averaging, are presented. Images of a standard resolution phantom are reconstructed and used for qualitative testing.
Open Access
Reduction of effects of inactive array elements in phase aberration correction
(IEEE, 1993) Karaman, Mustafa; Köymen, Hayrettin; Atalar, Abdullah; O'Donnell, M.
Phase aberration correction based on time delay estimation via minimization of sum of absolute difference (SAD) between radio frequency (RF) signals of neighboring elements is studied in the presence of missing elements. To examine the influence of inactive elements, phase estimation error is measured for various combinations of different number of missing elements, aberration level, and SNR. The measurements are performed on an experimental RF data set. Aberration delays of missing elements are interpolated using the phase estimate between the nearest active elements. The B-scan images are reconstructed for qualitative examination.