Microcirculation volumetric flow assessment using high-resolution, contrast-assisted images.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Ultrasound Technology

Background:

• High-frequency ultrasound systems offer improved spatial resolution for microvascular imaging.
• Previous work established a 25-MHz microbubble-destruction/replenishment system with 160x160 micrometer resolution.

Purpose of the Study:

• To develop a new functional evaluation method for microvascular volumetric blood flow using high-frequency ultrasound.
• To simultaneously locate perfusion areas and estimate blood flow velocity.

Main Methods:

• A correlated-based approach was used to detect blood perfusion areas by analyzing image correlations before and after microbubble destruction.
• A sigmoid-based model was developed to characterize microbubble replenishment, yielding rate constant and inflection time parameters for flow velocity estimation.
• Simulations and in vitro experiments validated the model for flow velocities from 1-10 mm/s, and B-mode imaging assessed volumetric flow (0.4-2.1 mm/s).

Main Results:

• The sigmoid-based model showed good agreement with simulated and measured microbubble replenishment curves.
• Actual flow velocity strongly correlated with the rate constant and reciprocal of inflection time.
• Volumetric flow rate correlated highly with the product of perfusion area and the derived flow velocity parameters.
• Microbubble destruction volume boundaries significantly impacted flow velocity estimations.

Conclusions:

• The developed approach enables simultaneous localization of perfusion areas and estimation of blood flow velocity in a single stage.
• This method makes real-time assessment of volumetric blood flow in the microcirculation feasible with high-frequency ultrasound.