Super-Resolution Ultrasound Imaging Can Quantify Alterations in Microbubble Velocities in the Renal Vasculature of Rats

Abstract

Super-resolution ultrasound imaging, based on the localization and tracking of single intravascular microbubbles, makes it possible to map vessels below 100 µm. Microbubble velocities can be estimated as a surrogate for blood velocity, but their clinical potential is unclear. We investigated if a decrease in microbubble velocity in the arterial and venous beds of the renal cortex, outer medulla, and inner medulla was detectable after intravenous administration of the α1-adrenoceptor antagonist prazosin. The left kidneys of seven rats were scanned with super-resolution ultrasound for 10 min before, during, and after prazosin administration using a bk5000 ultrasound scanner and hockey-stick probe. The super-resolution images were manually segmented, separating cortex, outer medulla, and inner medulla. Microbubble tracks from arteries/arterioles were separated from vein/venule tracks using the arterial blood flow direction. The mean microbubble velocities from each scan were compared. This showed a significant prazosin-induced velocity decrease only in the cortical arteries/arterioles (from 1.59 ± 0.38 to 1.14 ± 0.31 to 1.18 ± 0.33 mm/s, p = 0.013) and outer medulla descending vasa recta (from 0.70 ± 0.05 to 0.66 ± 0.04 to 0.69 ± 0.06 mm/s, p = 0.026). Conclusively, super-resolution ultrasound imaging makes it possible to detect and differentiate microbubble velocity responses to prazosin simultaneously in the renal cortical and medullary vascular beds.

Renal Contrast-enhanced Ultrasound: Clinical Applications and Emerging Researc

“…This emerging technology provides a substantial advancement in hemodynamic quantification and evaluation of the microcirculation, demonstrating a 10fold improvement in spatial resolution using low imaging frequencies and without compromising the imaging depth of conventional CEUS [79,81,83,84]. Super-resolution ultrasound imaging is capable of mapping vessels less than 100 µm in size [85]. In an in vivo mouse model, Chen et al identified renal micro vessels with a spatial resolution of up to 32 μm using a frame rate of 15.6 MHz [86].…”

Super-Resolution Ultrasound Imaging of Renal Vascular Alterations in Zucker Diabetic Fatty Rats during the Development of Diabetic Kidney Disease

“…Recently, SRUS showed a superiority to ultrasound in the evaluation of human kidney allograft vascularization [19]. Additionally, SRUS has been used on rodent kidneys to detect decreased vascular density after acute kidney injury and flow-velocity changes [20][21][22][23]. However, altered renal vascular morphology as a consequence of DKD development has not previously been investigated using SRUS.…”

Microvascular Imaging with Super-Resolution Ultrasound

“…For example, unlike sham-operated mice, mice with unilateral ischemia-reperfusion-induced chronic kidney disease had decreased vascular density and increased tortuosity in the renal cortex [19]. In another study, a vasodilator-induced decrease in microbubble velocity was found in the cortex and the deeper-lying medulla of rat kidneys [20], and lastly, increased microbubble velocity was found in the cortical radial arteries of hypertensive rats [21]. The cortical vessels of a human kidney have also been visualized with SRUS [22].…”

“…So wiesen Mäuse mit einseitiger, durch Ischämie-Reperfusion induzierter, chronischer Nierenerkrankung im Gegensatz zu scheinoperierten Mäusen eine verringerte Gefäßdichte und erhöhte Tortuosität in der Nierenrinde auf [19]. In einer anderen Studie wurde eine durch Vasodilatatoren induzierte Abnahme der Geschwindigkeit von Mikrobläschen im Cortex und im tiefer liegenden Mark von Rattennieren festgestellt [20]. Schließlich wurde eine erhöhte Geschwindigkeit von Mikrobläschen in der kortikalen A. radialis hypertensiver Ratten gefunden [21].…”