Two-dimensional phase aberration measurement and correction using a 1.75D 8 x 128 ultrasonic array.

摘要

This dissertation work examines the use of a 1.75D 8 x 128 array in improving ultrasound image quality. This array geometry is not used in current commercial ultrasound scanners and can be used to apply well-developed lateral ultrasound beamforming techniques to the elevation dimension. Results showing the application of synthetic elevation beamforming are presented in this dissertation.; In addition, this array provides the system with a larger array footprint over which to interrogate tissue. This is useful in adaptive imaging which consists of measuring and correcting for tissue aberrations for improved beamforming. After phase aberration correction, the system has improved detail and contrast resolution due to better focusing. This dissertation presents the issues involved in aberration measurement and correction. The ability to estimate two-dimensional aberrators with this array is demonstrated in simulation, experimental phantom, and clinical experiments. Receive-Only adaptive imaging is performed. The results for 2 mm-diameter spherical lesion phantoms imaged through aberrators with varying strengths show averaged improved contrasts of 54%. Receive-Only adaptive imaging was performed on thyroid, liver, and breast scans on volunteers and patients. The average aberration measurements in the breast scans were: 37.0 ± 14.7 ns RMS, 7.0 ± 1.2 mm FWHM (20–30 years-old women); 34.7 ± 8.6 ns RMS, 6.4 ± 1.0 mm FWHM (30–40 years-old women); 25.4 ± 8.0 ns RMS, 5.3 ± 1.7 mm FWHM (50–60 years-old women); and 27.5 ± 6.5 ns RMS, 6.4 ± 1.0 mm FWHM (60–70 years-old women). A case study is presented examining the issues in aberration measurement and correction in a breast scan with microcalcification clusters.; The necessity of two-dimensional aberration measurements for effective aberration measurement is demonstrated in this work. In addition, the challenges involved in aberration measurement and correction are identified. Improved clinical results are shown in the breast, liver, and thyroid tissues. Simulation results are also presented that show that Transmit-and-Receive correction will lead to further gains from adaptive imaging.