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Updated: Aug 22, 2026
A Methodological Approach to Non-invasive Assessments of Vascular Function and Morphology
Published on: February 7, 2015
Detection of retained microbubbles in carotid arteries with real-time low mechanical index imaging in the setting of
Jeane M Tsutsui1, Feng Xie, Martin Cano
1Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-1165, USA.
Objectives:
We sought to determine if intravenously injected microbubbles would be retained by the carotid arteries (CAs) in the setting of endothelial dysfunction (ED) using a linear transducer equipped with a low mechanical index pulse sequence scheme (PSS).
Background:
Microbubbles normally pass freely through large and small vessels but are retained in regions with ED. New high-frequency low mechanical index PSS can potentially be utilized to image these retained microbubbles.
Methods:
Intravenous albumin- and lipid-encapsulated microbubbles were administered in seven pigs while imaging the CAs before and after a 20% intralipid infusion to induce hypertriglyceridemia. The degree of microbubble retention was quantified by measuring endothelial acoustic intensity (AI) after clearance of free-flowing microbubbles. Microbubble adherence was also evaluated after selective balloon injury of the CAs. The CA diameter responses to acetylcholine were quantified.
Results:
After induction of hypertriglyceridemia, adherence of albumin-encapsulated microbubbles was visually evident in all CAs, and endothelial AI increased significantly (p < 0.001 compared with baseline). The CA responses to acetylcholine went from vasodilation at baseline to vasoconstriction during hypertriglyceridemia. Endothelial AI also increased in the balloon-stretched vessels (p < 0.01 compared with uninjured vessels) after albumin-encapsulated microbubble injection, with a ring of microbubbles selectively adhering to the injured segment. This retention was not observed with lipid-encapsulated microbubbles. Scanning electron microscopy confirmed that albumin-coated microbubbles adhered to endothelial cells.
Conclusions:
Retention of intravenously injected albumin microbubbles occurs in the setting of both global and regional ED in large vessels and can be noninvasively imaged with high-frequency low mechanical index PSS.
Insights
Albumin microbubbles, but not lipid microbubbles, are retained in carotid arteries with endothelial dysfunction. This retention, indicating disease, can be visualized noninvasively using advanced ultrasound imaging techniques.
Area of Science:
- Vascular biology
- Medical imaging
- Biomaterials
Background:
- Microbubbles typically flow freely through blood vessels.
- Endothelial dysfunction (ED) causes microbubble retention in affected areas.
- New ultrasound pulse sequence schemes (PSS) may image these retained microbubbles.
Purpose of the Study:
- To investigate microbubble retention in carotid arteries (CAs) with endothelial dysfunction (ED).
- To assess the utility of a low mechanical index pulse sequence scheme (PSS) for imaging microbubble retention.
- To evaluate the impact of hypertriglyceridemia-induced ED on microbubble adherence.
Main Methods:
- Administered albumin- and lipid-encapsulated microbubbles intravenously in pigs.
- Induced hypertriglyceridemia with intralipid infusion to model ED.
- Quantified microbubble retention via endothelial acoustic intensity (AI) and microbubble adherence after balloon injury.
- Assessed CA diameter response to acetylcholine.
Main Results:
- Albumin microbubbles adhered to CAs in hypertriglyceridemia, significantly increasing endothelial AI (p < 0.001).
- Carotid arteries shifted from vasodilation to vasoconstriction in response to acetylcholine.
- Albumin microbubbles adhered to balloon-injured CA segments, but not lipid microbubbles.
- Scanning electron microscopy confirmed albumin microbubble adherence to endothelial cells.
Conclusions:
- Intravenous albumin microbubbles are retained in large vessels with global and regional ED.
- High-frequency, low mechanical index PSS can noninvasively image this microbubble retention.
- Microbubble retention serves as a marker for endothelial dysfunction in large arteries.
