Abstract
In vivo monitoring of the microvasculature is relevant since diseases such as diabetes, ischemia, or cancer cause microvascular impairment. Super-resolution ultrasound imaging allows in vivo examination of the microvasculature by detecting and tracking sparsely distributed intravascular microbubbles over a minute-long period. The ability to create detailed images of the renal vasculature of Sprague-Dawley rats using a modified clinical ultrasound platform was investigated in this study. Additionally, we hypothesized that early ischemic damage to the renal microcirculation could be visualized. After a baseline scan of the exposed kidney, 10 rats underwent clamping of the renal vein (n = 5) or artery (n = 5) for 45 min. The kidneys were rescanned at the onset of clamp release and after 60 min of reperfusion. Using a processing pipeline for tissue motion compensation and microbubble tracking, super-resolution images with a very high level of detail were constructed. Image filtration allowed further characterization of the vasculature by isolating specific vessels such as the ascending vasa recta with a 15–20 μm diameter. Using the super-resolution images alone, it was only possible for six assessors to consistently distinguish the healthy renal microvasculature from the microvasculature at the onset of vein clamp release. Future studies will aim at attaining quantitative estimations of alterations in the renal microvascular blood flow using super-resolution ultrasound imaging.
Highlights
In vivo visualization of the microvasculature is an important clinical tool
In the healthy rat kidneys, a mean of 74 ± 27 MBs/frame was detected during the scans
We investigated the ability to create SR images of the renal vasculature of healthy Sprague-Dawley rats using a modified clinical ultrasound scanner and probe together with a customized processing pipeline for tissue motion compensation and MB tracking
Summary
In vivo visualization of the microvasculature is an important clinical tool. The microvascular networks are fundamental for tissue homeostasis and are altered by diseases such as diabetes, ischemic disease, or cancer as well as normal aging [1,2,3,4,5,6,7]. The architectural or functional alterations of the microvasculature can compromise organ function or facilitate tumor growth. Early and precise diagnosis and monitoring of the microvascular alterations are crucial to detect these unfavorable. Super-resolution (SR) ultrasound imaging can depict the vasculature, including the microvasculature, of both superficial and deeper-lying organs and tissues in vivo using sparsely distributed microbubbles (MBs) as intravascular tracers. The SR image is obtained over minutes and is an accumulation of thousands of successive image frames in which each MB centroid is detected [8,9]
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