Curvilinear 3-D Imaging Using Row-Column-Addressed 2-D Arrays With a Diverging Lens: Feasibility Study

Constructing a double-curved row-columnaddressed (RCA) 2-D array or applying a diverging lens over the flat RCA 2-D array can extend the imaging fieldof-view (FOV) to a curvilinear volume without increasing the aperture size, which is necessary for applications, such as abdominal and cardiac imaging. Extended FOV and low channel count of double-curved RCA 2-D arrays make 3-D imaging possible with equipment in the price range of conventional 2-D imaging. This paper proposes a delay-and-sum beamformation scheme specific to double-curved RCA 2-D arrays and validates its focusing ability based on simulations. A synthetic aperture imaging sequence with single element transmissions is designed for imaging down to 14 cm at a volume rate of 88 Hz. Using a diverging lens with an f-number of -1 circumscribing the underlying RCA array, the imaging quality of a double-curved λ/2-pitch 3-MHz 62 + 62 RCA 2-D array is investigated as a function of depth within a curvilinear FOV of 60° × 60°. The simulated double-curved 2-D array exhibits the same full-width-at-half-maximum values for a point scatterer within its curvilinear FOV at a fixed radial distance compared with a flat 2-D array within its rectilinear FOV. The results of this paper demonstrate that the proposed beamforming approach is accurate for achieving correct time-of-flight calculations, and hence avoids geometrical distortions.