Three-Dimensional Super-Resolution Imaging Using a Row–Column Array

A 3-D super-resolution (SR) pipeline based on data from a row–column (RC) array is presented. The 3-MHz RC array contains 62 rows and 62 columns with a half wavelength pitch. A synthetic aperture (SA) pulse inversion sequence with 32 positive and 32 negative row emissions is used for acquiring volumetric data using the SARUS research ultrasound scanner. Data received on the 62 columns are beamformed on a GPU for a maximum volume rate of 156 Hz when the pulse repetition frequency is 10 kHz. Simulated and 3-D printed point and flow microphantoms are used for investigating the approach. The flow microphantom contains a 100-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> radius tube injected with the contrast agent SonoVue. The 3-D processing pipeline uses the volumetric envelope data to find the bubble’s positions from their interpolated maximum signal and yields a high resolution in all three coordinates. For the point microphantom, the standard deviation on the position is (20.7, 19.8, 9.1) <inline-formula> <tex-math notation="LaTeX">${\mu }\text{m}~(x,y,z)$ </tex-math></inline-formula>. The precision estimated for the flow phantom is below <inline-formula> <tex-math notation="LaTeX">$23~\mu \text{m}$ </tex-math></inline-formula> in all three coordinates, making it possible to locate structures on the order of a capillary in all three dimensions. The RC imaging sequence’s point spread function has a size of 0.58 <inline-formula> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 1.05 <inline-formula> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 0.31 mm³ (<inline-formula> <tex-math notation="LaTeX">$1.17\lambda \times 2.12\lambda \times 0.63\lambda $ </tex-math></inline-formula>), so the possible volume resolution is 28900 times smaller than for SA RC B-mode imaging.