Frequency-Dependent F-Number Increases the Contrast and the Spatial Resolution in Fast Pulse-Echo Ultrasound Imaging

TL;DR

This paper introduces a frequency-dependent F-number in pulse-echo ultrasound imaging that enhances contrast and spatial resolution by adaptively adjusting receive subaperture sizes across frequencies.

Contribution

It proposes a novel frequency-dependent F-number approach that improves artifact suppression and resolution simultaneously in ultrasound imaging.

Findings

Improved contrast by up to 3.2%

Enhanced lateral resolution with up to 12.8% better wire target widths

Validated through experiments showing superior imaging performance

Abstract

Fixed $F$-numbers reduce grating lobe artifacts in fast pulse-echo ultrasound imaging. Such $F$-numbers result in dynamic receive subapertures whose widths vary with the focal position. These subapertures, however, ignore useful low-frequency components in the excluded radio frequency (RF) signals and, thus, reduce the lateral resolution. Here, we propose a frequency-dependent $F$-number to simultaneously suppress grating lobe artifacts and maintain the lateral resolution. This $F$-number, at high frequencies, reduces the receive subaperture to remove spatially undersampled components of the RF signals and suppress grating lobes. The $F$-number, at low frequencies, enlarges the receive subaperture to use the components of all RF signals and maintain the lateral resolution. Experiments validated the proposed $F$-number and demonstrated improvements in the contrast and the widths of wire targets of up to 3.2 % and 12.8 %, respectively.