Simultaneous enhancement of B-mode axial and lateral resolution using axial deconvolution

Enhancement of image resolution in ultrasound images is key to help clinicians end early indicators of pathological lesions. Image resolution enhancement relies on deconvolving the point spread function (PSF) of the imaging system out of the raw ultrasound image prior to envelope detection and other postprocessing steps. Unfortunately, in most cases the PSF is spatially variant, complicating its estimation and subsequent use in deconvolution. The current work is driven by the realization that the PSF can be decomposed into spatially invariant and variant components, namely the electric and geometric responses of the transducer element(s). Since the electric response acts along the axial direction, depth-independent axial deconvolution can be performed along the entire image. Moreover, since axial deconvolution effectively shapes the frequency response of the transducer, lateral resolution can also be enhanced. Using simulated and experimental data from two single element transducers (of 20, 35 MHz nominal frequencies), it is shown frequency-weighted axial deconvolution can simultaneously improve resolution in both directions. The results demonstrate a framework for improving axial and lateral resolution for ultrasound images that is unaffected by depth-dependent effects and that can balance the need for axial and lateral resolution improvement based on their relative values.