A novel microbubble construct for intracardiac or intravascular MR manometry: a theoretical study.
It has been demonstrated that gas-filled microbubble contrast agents, based on their volume changes, can serve as pressure probes in an MR field. It was recently reported that such an MR-based pressure measurement with microbubbles at 1.5 T must make use of microbubbles that have a volumetric magnetic susceptibility difference with the blood of at least 34 ppm in SI units. In this work, we show through analytical approximations and numerical simulations that such a microbubble formulation can be achieved by coating typical lipid-shelled microbubbles with particles of high dipole moment. Through finite-element simulations we demonstrate that the effective volumetric magnetic susceptibility of a coated microbubble is dependent on the radius, the shell volume fraction and the magnetic susceptibility of the particulates on the shell. Our calculations suggest that a suitable microbubble formulation which will be MR-sensitive to small pressure changes at 1.5 T must be 2-3 microm in radius and be uniformly coated with single-domain magnetic nanoparticles, such as magnetite, at shell volume fractions below 5%.
Dharmakumar
Rohan
R
Department of Medical Biophysics, Sunnybrook & Women's College Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada. rohan@sten.sunnybrook.utoronto.ca
Plewes
Donald B
DB
Wright
Graham A
GA
D001158:Arteries / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000379:methods*; D003198:Computer Simulation; D003287:Contrast Media; D015195:Drug Design; D006321:Heart / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008365:Manometry / Q000379:methods; D045423:Microbubbles; D008955:Models, Cardiovascular
D003287:Contrast Media