Fast Vascular Ultrasound Imaging with Enhanced Spatial Resolution and Background Rejection

摘要

Ultrasound super-localization microscopy techniques presented in the last fewyears enable non-invasive imaging of vascular structures at the capillary levelby tracking the flow of ultrasound contrast agents (gas microbubbles). However,these techniques are currently limited by low temporal resolution and longacquisition times. Super-resolution optical fluctuation imaging (SOFI) is afluorescence microscopy technique enabling sub-diffraction limit imaging withhigh temporal resolution by calculating high order statistics of thefluctuating optical signal. The aim of this work is to achieve fast acousticimaging with enhanced resolution by applying the tools used in SOFI tocontrast-enhance ultrasound (CEUS) plane-wave scans. The proposed method wastested using numerical simulations and evaluated using two in-vivo rabbitmodels: scans of healthy kidneys and VX-2 tumor xenografts. Improved spatialresolution was observed with a reduction of up to 50% in the full width halfmax of the point spread function. In addition, substantial reduction in thebackground level was achieved compared to standard mean amplitude persistenceimages, revealing small vascular structures within tumors. The scan duration ofthe proposed method is less than a second while current superlocalizationtechniques require acquisition duration of several minutes. As a result, theproposed technique may be used to obtain scans with enhanced spatial resolutionand high temporal resolution, facilitating flow-dynamics monitoring. Our methodcan also be applied during a breath-hold, reducing the sensitivity to motionartifacts.