Accuracy of measurements of tissue lateral displacement and displacement vector using laterally wide wave transmission for high speed scanning over region of interest

摘要

For a rapid scanning over a region of interest (ROI) in human tissues, a non-steered plane wave transmission is used, particularly when using a 2-dimensoinal array transducer. In Sumi's case, such a wave is used with a steering for measuring a rapid target motion (ie, displacement, velocity, strain etc) including when using a 1-dimensional array transducer. In Sumi's approach, a beam angle is measured with a high spatial resolution for all beamformings including conventional focusing beamformings, and the displacement in the beam direction is accurately measured to obtain the displacement of an arbitrary direction of the target motion of which direction is known (eg, depth, lateral, radial etc). For instance, for the lateral displacement measurement, ASTA (A defined STeering Angle) beamforming is proposed. For a displacement vector measurement, plural waves are crossed and superposed by transmitting such waves simultaneously or successively to yield a lateral modulation (LM). Sumi's previously developed multidimensional autocorrelation method is used (MAM). Also when generating no plural transmissions, a displacement vector measurement can be achieved by using Sumi's developed spectra frequency division method (SFDM: Spectra Frequency Division Method) together with MAM. Also for all the measurements, an over-determined system can be used by performing more numbers of transmissions than theoretically required transmissions or applying SFDM extensively. In this report, the measurement accuracy is evaluated using agar phantoms for all the measurements using the focused beamformings or plane wave transmissions. For a non-flat aperture such as concave, convex transducers, such plane wave transmissions correspond to laterally wide wave transmissions. In this report, a spherical dynamic focusing is used for the transmission focus.