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A novel microbubble construct for intracardiac or intravascular MR manometry: a theoretical study
Rohan Dharmakumar1, Donald B Plewes, Graham A Wright
1Department of Medical Biophysics, Sunnybrook & Women's College Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada. rohan@sten.sunnybrook.utoronto.ca
Physics in Medicine and Biology
|October 6, 2005
Summary
Gas-filled microbubbles can act as pressure probes using magnetic resonance (MR). Coating microbubbles with magnetic nanoparticles enhances their sensitivity for precise MR-based pressure measurements.
Area of Science:
- Biomedical Engineering
- Materials Science
- Magnetic Resonance Imaging
Background:
- Gas-filled microbubbles demonstrate volume changes responsive to magnetic resonance (MR) fields.
- Previous research indicates a need for a significant magnetic susceptibility difference (34 ppm) for MR-based pressure measurement at 1.5 T.
Purpose of the Study:
- To investigate methods for enhancing microbubble magnetic susceptibility for MR-based pressure sensing.
- To determine optimal microbubble formulations for MR sensitivity to pressure variations.
Main Methods:
- Analytical approximations and numerical simulations were employed.
- Finite-element simulations analyzed the magnetic susceptibility of coated microbubbles.
- Investigated the impact of particle coating, radius, and shell volume fraction.
Main Results:
- Coating lipid-shelled microbubbles with high dipole moment particles can achieve the required magnetic susceptibility.
- Effective volumetric magnetic susceptibility depends on microbubble radius, shell volume fraction, and particle properties.
- Optimal formulations involve 2-3 micrometer radius microbubbles coated with magnetite nanoparticles at <5% shell volume fraction.
Conclusions:
- Microbubble formulation with magnetic nanoparticle coatings is a viable strategy for MR-based pressure sensing.
- This approach enhances MR sensitivity to small pressure changes at 1.5 T.
- Optimized microbubbles offer a promising tool for non-invasive pressure monitoring.