Sensing ultrasound localization microscopy for the visualization of glomeruli in living rats and humans.

Background: Estimation of glomerular function is necessary to diagnose kidney diseases. However, the study of glomeruli in the clinic is currently done indirectly through urine and blood tests. A recent imaging technique called Ultrasound Localization Microscopy (ULM) has appeared. It is based on the ability to record continuous movements of individual microbubbles in the bloodstream. Although ULM improved the resolution of vascular imaging up to tenfold, the imaging of the smallest vessels had yet to be reported.
Methods: We acquired ultrasound sequences from living humans and rats and then applied filters to divide the data set into slow-moving and fast-moving microbubbles. We performed a double tracking to highlight and characterize populations of microbubbles with singular behaviors. We decided to call this technique "sensing ULM" (sULM). We used post-mortem micro-CT for side-by-side confirmation in rats.
Findings: In this study, we report the observation of microbubbles flowing in the glomeruli in living humans and rats. We present a set of analysis tools to extract quantitative information from individual microbubbles, such as remanence time or normalized distance.
Interpretation: As glomeruli play a key role in kidney function, it would be possible that their observation yields a deeper understanding of the kidney. It could also be a tool to diagnose kidney diseases in patients. More generally, it will bring imaging capabilities closer to the functional units of organs, which is a key to understand most diseases, such as cancer, diabetes, or kidney failures.
Funding: This study was funded by the European Research Council under the European Union Horizon H2020 program (ERC Consolidator grant agreement No 772786-ResolveStroke).
Competing Interests: Declaration of interests O.C. and V.H., hold patents in the field of ultrasound localization microscopy (EP4011299A1). O.C. and V.H. are founders and shareholders of the ResolveStroke startup. O.C. has received several grants: ERC Consolidator grant agreement no 772786-Resolve Stroke, ERC POC (2022–2023), Maturation SATT Lutech for ResolveStroke Startup, ANR FightClot, CNRS Prematuration for ResolveStroke Startup, RHU Quid NASH. O.C. gave a lecture at Bracco SAS and was an invited speaker at several conferences such as BMT Innsbruck. Other authors have no conflict of interest to disclose.
(Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)