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Enhancement of gas‐filled microbubble R 2 * by iron oxide nanoparticles for MRI
Author(s) -
Chow April M.,
Chan Kannie W. Y.,
Cheung Jerry S.,
Wu Ed X.
Publication year - 2010
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.22184
Subject(s) - microbubbles , iron oxide nanoparticles , nanoparticle , iron oxide , biocompatibility , chemistry , nuclear magnetic resonance , mri contrast agent , materials science , magnetic resonance imaging , ultrasound , nanotechnology , radiology , organic chemistry , medicine , physics
Gas‐filled microbubbles have the potential to become a unique intravascular MR contrast agent due to their magnetic susceptibility effect, biocompatibility, and localized manipulation via ultrasound cavitation. However, microbubble susceptibility effect is relatively weak when compared with other intravascular MR susceptibility contrast agents. In this study, enhancement of microbubble susceptibility effect by entrapping monocrystalline iron oxide nanoparticles (MIONs) into polymeric microbubbles was investigated at 7 T in vitro. Apparent T 2 enhancement (Δ R 2 *) induced by microbubbles was measured to be 79.2 ± 17.5 sec −1 and 301.2 ± 16.8 sec −1 for MION‐free and MION‐entrapped polymeric microbubbles at 5% volume fraction, respectively. Δ R 2 * and apparent transverse relaxivities ( r 2 *) for MION‐entrapped polymeric microbubbles and MION‐entrapped solid microspheres (without gas core) were also compared, showing the synergistic effect of the gas core with MIONs. This is the first experimental demonstration of microbubble susceptibility enhancement for MRI application. This study indicates that gas‐filled polymeric microbubble susceptibility effect can be substantially increased by incorporating iron oxide nanoparticles into microbubble shells. With such an approach, microbubbles can potentially be visualized with higher sensitivity and lower concentrations by MRI. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.