3-D Transcranial Ultrasound Localization Microscopy Reveals Major Arteries in the Sheep Brain.

Cerebral circulation ensures the proper functioning of the entire human body, and its interruption, i.e., stroke, leads to irreversible damage. However, tools for observing cerebral circulation are still lacking. Although MRI and computed tomography (CT) scans serve as conventional methods, their accessibility remains a challenge, prompting exploration into alternative, portable, and nonionizing imaging solutions like ultrasound with reduced costs. While ultrasound localization microscopy (ULM) displays potential in high-resolution vessel imaging, its 2-D constraints limit its emergency utility. This study delves into the feasibility of 3-D ULM with multiplexed probe for transcranial vessel imaging in sheep brains, emulating human skull characteristics. Three sheep underwent 3-D ULM imaging, compared with angiographic MRI, while skull characterization was conducted in vivo using ultrashort bone MRI sequences and ex vivo via micro-CT. The study showcased 3-D ULM's ability to highlight vessels, down to the circle of Willis, yet within a confined 3-D field of view. Future enhancements in signal, aberration correction, and human trials hold promise for a portable, volumetric, transcranial ultrasound angiography system.