In vivo vascular wall tissue characterization using a strain tensor measuring (STM) technique for flow-mediated...

Area of Science:

• Cardiovascular Research
• Biomedical Engineering
• Medical Imaging

Background:

• Endothelial dysfunction is a key factor in atherosclerosis development.
• Flow-mediated vasodilation (FMD) is a common in vivo method to assess endothelial function.
• Current FMD measurements primarily rely on diameter changes, potentially missing subtle vascular mechanics.

Purpose of the Study:

• To introduce a novel, non-invasive ultrasound-based strain tensor measuring (STM) technique.
• To assess changes in vascular wall mechanics during post-occlusion reactive hyperemia and FMD.
• To evaluate STM's potential as a tool for assessing endothelial function and atherosclerosis.

Main Methods:

• Developed an ultrasound-based strain tensor measuring (STM) technique using B-mode ultrasound images.
• Employed a block matching technique based on speckle tracking for local velocity measurements.
• Calculated displacements, diameter change, local strain tensor, and strain rates from velocity components.
• Validated the STM algorithm in vitro using phantom studies and in vivo using human subjects.

Main Results:

• The in vitro phantom studies reported an average error of 7% for the STM algorithm.
• In vivo studies showed good correlations (|r| >0.5, P < 0.05) between diameter change and local wall strains during post-occlusion.
• Results demonstrated that parameters beyond diameter change are sensitive to reactive hyperemia.

Conclusions:

• The STM algorithm is a valid and versatile tool for assessing vascular mechanics.
• Local strains and strain rates are promising metrics for evaluating endothelial function and atherosclerosis.
• STM can potentially replace or augment traditional arterial diameter measurements in FMD studies for improved atherosclerosis assessment.