Doppler Slicing for Ultrasound Super-Resolution Without Contrast Agents

Much of the information needed for diagnosis and treatment monitoring of diseases like cancer and cardiovascular disease is found at scales below the resolution limit of classic ultrasound imaging. Recently introduced vascular super-localization methods provide more than a ten-fold improvement in spatial resolution by precisely estimating the positions of microbubble contrast agents. However, most vascular ultrasound scans are currently performed without contrast agents due to the associated cost, training, and post-scan monitoring. Here we show that super-resolution ultrasound imaging of dense vascular structures can be achieved using the natural contrast of flowing blood cells. Instead of relying on separable targets, we used Fourier-based decomposition to separate signals arising from the different scales of vascular structures while removing speckle noise using multi-ensemble processing. This approach enabled the use of compressed sensing for super-resolution imaging of the underlying vascular structures, improving resolution by a factor of four. Reconstruction of ultrafast mouse brain scans revealed details that could not be resolved in regular Doppler images, agreeing closely with bubble-based super-localization microscopy of the same fields of view. By combining multi-ensemble Doppler acquisitions with narrowband Fourier decomposition and computational super-resolution imaging, this approach opens new opportunities for affordable and scalable super-resolution ultrasound imaging.

Contrast-Enhanced Ultrasound in the Assessment of Carotid Atherosclerotic Disease: A Review

Contrast-enhanced sonography is a safe, radiation-free, and minimally invasive imaging technique. It takes advantage of the nonlinear behavior of microbubble contrast agents to produce microbubble-only images, which allows for the assessment of the extracranial carotid arteries, with a minuscule total dose of <1 mL. This review highlights the current status of extracranial carotid sonography imaging, including plaque characterization when using standard and contrast-enhanced sonography.Learning Objective: Describe risk factors associated with ischemic stroke and the associated imaging features and how contrast-enhanced sonography can provide direct evaluation for carotid artery stenosis as well as characterization of atherosclerotic plaque.

Miniaturized Ultrasound Transducer Composed of a Composite of Multiple Piezoelectric Stacks

This paper aims to develop a miniaturized ultrasound transducer for intravascular thrombolysis, which requires a transducer with high mechanical index (&gt; 0.3) and a long focal distance (&gt; 2.0 mm). To meet this need, a composite of a multi-pillar piezo stack (MPPS) transducer was designed and fabricated by using PZT-4, conductive epoxy, soft elastomer, and a metallic concave lens. The simulation results showed the predominant extensional mode at around 0.92 MHz. The −6 dB focal distance was elongated by 150% from that of the common single-pillar piezo stack (SPPS) transducer with the same aperture. The acoustic pressure was improved by 8.2 dB at the focal zone. Next, the experimental results showed the peak-to-negative pressure of 1.92 MPa under 120 Vpp input, which was sufficient to cause the inertial cavitation of microbubble contrast agents. The −6 dB focal distance reached up to 3.4 mm which was a significant improvement compared to the conventional SPPS transducer. The developed intravascular transducer will be employed for the microbubble-mediated ultrasound thrombolysis to reduce the treatment time.