Coherent-array imaging using phased subarrays. Part I: basic principles

Abstract

Abstract-The front-end hardware complexity of a coherent array imaging system scales with the number of active array elements that are simultaneously used for transmission or reception of signals. Different imaging methods use different numbers of active channels and data collection strategies. Conventional full phased array (FPA) imaging produces the best image quality using all elements for both transmission and reception, and it has high front-end hardware complexity. In contrast, classical synthetic aperture (CSA) imaging only transmits on and receives from a single element at a time, minimizing the hardware complexity but achieving poor image quality. We propose a new coherent array imaging method-phased subarray (PSA) imaging-that performs partial transmit and receive beamforming using a subset of adjacent elements at each firing step. This method reduces the number of active channels to the number of subarray elements; these channels are multiplexed across the full array and a reduced number of beams are acquired from each subarray. The low-resolution subarray images are laterally upsampled, interpolated, weighted, and coherently summed to form the final high-resolution PSA image. The PSA imaging reduces the complexity of the front-end hardware while achieving image quality approaching that of FPA imaging.

CMUT-based volumetric ultrasonic imaging array design for forward looking ICE and IVUS applications

“…The image SNR of a single pixel reconstructed using synthetic phased array can be calculated by: (1) where N T is the number of transmit elements, N R is the number of receive elements, and SNR 0 is the SNR of the pulse echo obtained by single transmit-receive pair [6]. Using multiple defocused elements in transmit improves transmitted beam intensity on the order of √K where K is the number of defocused elements [7,8].…”

Ultrasonic Projection

“…The goal of beamformer is to create as narrow and uniform a beam with as low sidelobes over as long a depth as possible. Among already proposed imaging methods and techniques are elevation focusing (1.25-D, 1.5-D and 1.75-D arrays) (Wildes et al, 1997), beam steering, synthetic apertures, 2-D and sparse matrices, configurable matrices, parallel beamforming, microbeamformers, rectilinear scanning, coded excitation, phased subarray processing, phase aberration correction, and others (Drinkwater & Wilcox, 2006;Johnson et al, 2005;Karaman et al, 2009;Kim & Song, 2006;Lockwood & Foster, 1996;Nowicki et al, 2009). The most common complication introduced by these is a significant increase in channel count.…”

“…complex system of properly rotated prisms), focusing devices or electronic devices, which control the system of activating and powering individual matrix elements in a proper manner (Drinkwater & Wilcox, 2006;Ermert et al, 2000;Granz & Oppelt, 1987;Green et al, 1974;Nowicki, 1995;Opielinski et al, 2009;Opielinski & Gudra, 2010a, 2010cOpielinski et al 2010aOpielinski et al , 2010bRamm & Smith, 1983;Thomenius, 1996). Exciting individual transducers of the multi-element probe using pulses with various delay is a universal method of focusing and deflecting a beam (Johnson et al, 2005;Thomenius, 1996). Adequate delays between activations of each successive elementary transducer allow shaping of the wave front and the direction of its propagation.…”

Narrow Beam Ultrasonic Transducer Matrix Model for Projection Imaging of Biological Media

“…Exciting individual transducers of the multielement probe using pulses with various delay is a universal method of focusing and deflecting a beam (Johnson et al, 2005;Thomenius, 1996). Adequate delays between activations of each successive elementary transducer allow shaping of the wavefront and the direction of its propagation.…”