Spatial resolution in medical ultrasound images is a key component in image quality and an important factor for clinical diagnosis. In early systems, the lateral resolution was optimal in the focus but rapidly decreased outside the focal region. Improvements have been found in, e.g., dynamic-receive beamforming, in which the entire image is focused in receive, but this requires complex processing of element data and is not applicable for mechanical scanning of single-element images. This paper exploits the concept of two-stage beamforming based on virtual source-receivers, which reduces the front-end computational load while maintaining a similar data rate and frame rate compared to dynamic-receive beamforming. We introduce frequency-wavenumber domain data processing to obtain fast second-stage data processing while having similarly high lateral resolution as dynamic-receive beamforming and processing in time-space domain. The technique is very suitable in combination with emerging technologies such as application-specific integrated circuits (ASICs), hand-held devices, and wireless data transfer. The suggested method consists of three steps. In the first step, single-focused RF line data are shifted in time to relocate the focal point to a new origin t' = 0, z' = 0. This new origin is considered as an array of virtual source/receiver pairs, as has been suggested previously in literature. In the second step, the dataset is efficiently processed in the wavenumber-frequency domain to form an image that is in focus throughout its entire depth. In the third step, the data shift is undone to obtain a correct depth axis in the image. The method has been tested first with a single-element scanning system and second in a tissue-mimicking phantom using a linear array. In both setups, the method resulted in a -6-dB lateral point spread function (PSF) which was constant over the entire depth range, and similar to dynamic-receive beamforming and synthetic aperture sequential be@en

Superharmonic imaging (SHI) targets a combination of the third to fifth harmonics. It was proven to have certain advantages in comparison with the established imaging standards in medicalultrasound. SHI enhances the spatial resolution and improves the quality of echographic images, mainly by eliminating reverberation artifacts at the chest wall. However, SHI suffers from ripple artifacts, originating from the spectral gaps in between harmonics, and degrading the temporal resolution. To solve this a chirp‐based SHI protocol was employed and its characteristics investigated, i.e., point spread function (PSF). The protocol was implemented for an interleaved phased array probe (44+44 elements tuned at 1.0+3.7 MHz), connected to a fully programmable ultrasound system. A linear chirp (center frequency 1 MHz; bandwidth 40%) was used for excitation. To obtain the PSF, the rf traces were recorded at focus along the lateral axis and convolved with the decoding signal. This was computed using KZK simulations. A PSF comparison between a superharmonic chirp and the third harmonic of a 2.5‐cycle Gaussian apodized sinus burst at 1 MHz showed a decrease in axial pulse length of 46% at −6 dB and 32% at the −20 dB level in favor of SHI. Chirp based SHI is virtually free of ripple artifacts and therefore feasible@en