Sensing ultrasound localization microscopy for ultrastructural and functional imaging of neonatal kidneys

Abstract Sensing ultrasound localization microscopy (sULM) enables radiation-free imaging of microvascular architecture and blood flow dynamics by tracking intravasal microbubble contrast agents. This technical development aims to enable the visualization of glomeruli in the renal cortex of neonates serving as a potential imaging biopsy. This technical report describes the first use of sULM in the human neonatal kidney. Neonatal subjects were examined by transabdominal contrast-enhanced ultrasound using a standard clinical ultrasound device. An image-based motion correction algorithm was implemented and the filtering, localization, and tracking of microbubbles during sULM analysis were refined. sULM algorithms were applied next to depict fast- and slow-moving microbubbles separately and to identify glomeruli by distance metric calculations. Five neonates were investigated. Slow-moving microbubbles were detected mainly in the cortical region, travelling a typical route through a glomerulus. By calculating the cumulative movement of every microbubble, the number of glomeruli could be counted over the entire organ. We report an effective sULM workflow within the human neonate and the first microvascular sULM maps of neonatal renal vascularity up to the scale of a single glomerulus. The assessment of glomeruli as smallest functional units over the whole kidney has high potential to serve as a non-invasive imaging biomarker in future studies.