A single‐channel low‐frequency method for ultrasound imaging

Abstract

Transcranial ultrasound imaging of brain structures and pathologies have traditionally suffered from compromised signal‐to‐noise ratios due to the bone‐mediated increase in signal attenuation with increasing frequency. Yet, established modalities of image reconstruction with ultrasound measurements rely on higher frequencies for radial resolution and large temporal bandwidths for axial resolution. A new method that substantially reduces the dependency of image resolution on ultrasound frequency is proposed. Using an asymmetric transducer design, an unfocused, broadband, and frequency‐separated ultrasound field is created in a region‐of‐interest (ROI). In this fashion, a unique complex spectral label can be assigned to each point in the ROI with a spatial resolution independent of source frequency. Ultrasound scattering sites within the ROI are then spatially localized by identifying the unique frequency‐phase signature detected by either a point receiver or by the transmitting transducer. A cross‐correlation method is used to reconstruct the echogenic profile of the ROI using a priori measurements of the field. Since the method’s axial and radial resolutions are dependent on bandwidth rather than frequency, deeper penetration into tissues and application in highly attenuation tissues is feasible. Also, the prospect of multiple‐dimension imaging with a single channel will allow for reduced emitter and electronic complexity. [Work supported by NIH: R21EB004353 and U41RR019703.]