A high-frequency ultrasound imaging system using limited angle spatial compounding and synthetic aperture focusing

Recently, we presented a high-frequency ultrasound system for small animals imaging, which utilizes limited angle spatial compounding, resulting in a significant improvement of image quality. As a single-element fixed-focus transducer is used, the image resolution and signal-to-noise-ratio (SNR) still varies with imaging depth due to the focused ultrasound beam. To overcome the resulting limitation of imaging depth, synthetic aperture focusing techniques (SAFT) can be used. In this contribution we present an enhanced spatial compound imaging system which uses synthetic aperture image reconstruction. The individual echo signal frames, recorded from different transducer tilting angles, are processed by correlation with the depth-dependent simulated point spread function (PSF) of the imaging system, which results in a high noise reduction and an almost constant spatial resolution over depth. Following that, frames of echo signal envelopes are superimposed to form a spatial compound image, with improved signal-to-noise-ratio (SNR) and spatial resolution superior compared to the unprocessed spatial compound image. Images of ultrasound phantoms and post mortem images of a rat pup are examples to show the potential of the presented imaging system.