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Enhancement of gas-filled microbubble R2* by iron oxide nanoparticles for MRI
April M Chow1, Kannie W Y Chan, Jerry S Cheung
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong.
Abstract:
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 T2 enhancement (DeltaR2*) 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. DeltaR2* and apparent transverse relaxivities (r2*) 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.
Insights
Researchers enhanced magnetic susceptibility in polymeric microbubbles by adding monocrystalline iron oxide nanoparticles (MIONs). This improves their potential as intravascular MRI contrast agents, allowing for higher sensitivity imaging.
Area of Science:
- Biomedical Engineering
- Magnetic Resonance Imaging (MRI)
- Nanotechnology
Background:
- Gas-filled microbubbles show promise as intravascular MRI contrast agents.
- Their magnetic susceptibility effect is currently limited compared to other agents.
- Enhancing this effect is crucial for improved MRI sensitivity.
Purpose of the Study:
- To investigate the enhancement of microbubble magnetic susceptibility by incorporating monocrystalline iron oxide nanoparticles (MIONs).
- To evaluate the potential of MION-entrapped microbubbles as superior intravascular MRI contrast agents.
Main Methods:
- Polymeric microbubbles were fabricated with and without entrapped MIONs.
- Magnetic susceptibility effects were measured in vitro at 7 Tesla (7 T).
- Apparent T2 enhancement (DeltaR2*) was quantified and compared between MION-free and MION-entrapped microbubbles.
Main Results:
- MION-entrapped microbubbles exhibited significantly higher apparent T2 enhancement (301.2+/-16.8 sec(-1)) compared to MION-free microbubbles (79.2+/-17.5 sec(-1)) at 5% volume fraction.
- A synergistic effect was observed between the gas core and MIONs in polymeric microbubbles.
- This study provides the first experimental demonstration of microbubble susceptibility enhancement for MRI.
Conclusions:
- Incorporating iron oxide nanoparticles into microbubble shells substantially increases their magnetic susceptibility effect.
- MION-entrapped microbubbles offer enhanced sensitivity and potential for lower concentration visualization in MRI.
- This approach advances the development of microbubbles as effective intravascular MRI contrast agents.
