September 21, 2024
Paper link: https://www.biorxiv.org/content/10.1101/2024.09.19.613950v1
In this study led by Matt Lowerison, we present high-frequency ULM, which generated some of the best ULM images we've ever seen. In mouse brains with MB enhancement, SNR is not an issue and high frequency is ideal for ULM imaging.

Higher imaging frequency leads to smaller MB PSFs, which facilitate better MB separation and subsequent localization and tracking pipeline. Higher imaging frequency also supports the use of higher MB concentrations in blood stream to speed up ULM vessel filling.

At standard MB concentrations, higher imaging frequencies produce ULM images with sharper and more clearly delineated microvessels. Also the thinner slice thickness of high-frequency probes minimizes blurring in the elevational direction, resulting in “crisper” ULM images.

At high MB concentrations, lower-frequency probes (L22 and L35) struggled with MB localization, leading to incomplete ULM images with many missing vessels. In contrast, the high-frequency probe (MS550S) produced a very high-quality ULM image with clear vessel delineation.

High-frequency ULM enabled us to observe intricate details of the cerebral microvasculature. In one instance, we were able to trace an MB traveling through a descending artery, making a U-turn in a capillary vessel, and moving back up through an ascending vein.

FRC analysis showed that high-frequency ULM (when combined with the new Verasonics NXT system that provides 125 MHz sampling frequency) achieved a spatial resolution of ~7.1 microns in mouse brain when using 2-sigma threshold.
We are incredibly proud of the flawless execution of this study by Matt Lowerison, with outstanding support from our lab members including Yike Wang, Bing-Ze Lin, Zhe Huang, YiRang Shin, and Dongliang Yan.