Ultrasound localization microscopy for transabdominal resolution of glomeruli in neonatal kidneys

Aim Ultrasound localization microscopy (ULM) has been introduced as a novel non-invasive imaging technique to assess microvascular architecture and blood flow dynamics. By localization and tracking of intravenously injected individual contrast agents (microbubbles), reconstruction of microvasculature becomes feasible up to the scale of a single renal glomerulus [1] [2]. Accurate ULM analysis is highly dependent on stable image acquisition which can be challenging in respiratory displaceable organs like the kidney or in pediatric patients. We aimed to translate ULM into the human neonatal kidney opening an unprecedentedly detailed approach to evaluating renal impairment in neonates. By implementing motion-correction algorithms [3] we further paved the way for the use of ULM in challenging clinical settings within kidney research and pediatric medicine.

Materials and Methods As part of an ongoing prospective clinical trial, we conducted transabdominal contrast-enhanced ultrasound (CEUS) acquisitions on human neonates suffering from asphyxia. Acquisitions were performed with a clinical ultrasound scanner, using a convex probe and a preset with low mechanical index of 0.15 (transducer frequency 3 MHz, framerate17.5fps). Contrast agents (SonoVue, Bracco) were administered in a dose of 0.03ml/kg intravenously. CEUS acquisitions were exported in DICOM format and computational post-processing including motion-correction was carried out using Matlab (version: 9.13.0) [1] [2] [3] [4]

Results Image based motion correction heavily improved the ULM workflow and enabled reconstruction of a microvascular map of the human neonatal kidney. Microbubble velocities within renal vasculature could be measured revealing fast and slow tracks within the organ. Velocities could be measured as perfusion parameters. Fast tracks were detected in bigger vessels, slow tracks were mainly found in the kidney cortex. Further filtering of slow tracks for their typical route through a glomerulus by calculating their distance metric [2], made glomeruli in the neonatal kidney cortex non-invasively detectable.

Conclusion We hereby present the first microvascular map of the human neonatal kidney with visualization of renal vasculature up to the scale of single glomeruli in the kidney cortex using a clinical ultrasound scanner. This successful translation of ULM opens the door to unprecedented insights into neonatal kidney function, paving the way for future advancements in pediatric nephrology and critical care.

Publication History

Article published online:
19 May 2025

• Literatur

• 1 Denis L.. et al. "Sensing ultrasound localization microscopy for the visualization of glomeruli in living rats and humans,". EBioMedicine 2023;
• 2 Bodard S.. et al. Visualization of Renal Glomeruli in Human Native Kidneys With Sensing Ultrasound Localization Microscopy. Invest Radiol 2024;
• 3 Yan J.. et al. Transthoracic ultrasound localization microscopy of myocardial vasculature in patients. Nat Biomed Eng 2024;
• 4 Bodard S.. et al. Ultrasound localization microscopy of the human kidney allograft on a clinical ultrasound scanner. Kidney Int 2023;