Microbubbles containing gadolinium as contrast agents for both phase contrast and magnetic resonance imaging

Abstract

Portal vein imaging is an important method for investigating portal venous disorders. However, the diagnostic requirements are not usually satisfied when using single imaging techniques. Diagnostic accuracy can be improved by combining different imaging techniques. Contrast agents that can be used for combined imaging modalities are needed. In this study, the feasibility of using microbubbles containing gadolinium (MCG) as contrast agents for both phase contrast imaging (PCI) and magnetic resonance imaging (MRI) are investigated. MCG were made by encapsulating sulfur hexafluoride (SF) gas with gadolinium and lyophilized powder. Absorption contrast imaging (ACI) and PCI of MCG were performed and compared in vitro. MCG were injected into the main portal trunk of living rats. PCI and MRI were performed at 2 min and 10 min after MCG injection, respectively. PCI exploited the differences in the refractive index and visibly showed the MCG, which were not detectable by ACI. PCI could facilitate clear revelation of the MCG-infused portal veins. The diameter of the portal veins could be determined by the largest MCG in the same portal vein. The minimum diameter of clearly detected portal veins was about 300 µm by MRI. These results indicate that MCG could enhance both PCI and MRI for imaging portal veins. The detection sensitivity of PCI and MRI could compensate for each other when using MCG contrast agents for animals.

Phase retrieval‐based phase‐contrast CT for vascular imaging with microbubble contrast agent

“…The hydrocarbon gas within Expancel microbubbles is considered to have a refractive index comparable to that of clinically used microbubbles 14 . Individual microbubbles have been used as PCI contrast agent using the capacity of focusing x rays 6–8 . However, this focusing capacity can only be used to show some micro‐vessels where microbubbles distribute individually.…”

“…Due to the spherical structure and the difference in the refractive index compared with the surrounding tissues, individual microbubbles function as a lens to focus the x rays. Based on this principle, microbubbles have been used as a synchrotron radiation in‐line PCI contrast agent to delineate micro‐vessels in rodents, presenting as bright dots on the phase‐contrast images 6–8 . Unlike individual microbubbles, a cluster of microbubbles acting as many lenses scatters the x rays after multiple refractions in various directions.…”

“…On the other hand, compact laboratory source‐based PCI is capable of utilizing polychromatic x rays to be more practical for medical imaging 9–12 . As a contrast agent, microbubbles have been mainly used in projection PCI 5–11,13,15 . Projection PCI is based on planar imaging, and the vessels cannot be fully revealed due to image superimposition.…”

From Micro- to Nano-Multifunctional Theranostic Platform: Effective Ultrasound Imaging Is Not Just a Matter of Scale

“…4 The MBs-containing Gadolinium (Gd) complexes can be exploited to obtain a dual imaging strategy, for example, phase contrast imaging and MRI. 53 Superparamagnetic iron oxide NP-modified MBs for US-MRI bimodality imaging have been proposed as well. 54…”

“…4 The MBs-containing Gadolinium (Gd) complexes can be exploited to obtain a dual imaging strategy, for example, phase contrast imaging and MRI. 53 Superparamagnetic iron oxide NP-modified MBs for US-MRI bimodality imaging have been proposed as well. 54 The Need for Smaller US-Monitorable Carriers MBs are not able to passively extravasate due to their micronscaled sizes, but they remain in the circulation until they are taken up by the spleen and the liver 55 or they dissolve in rather short times.…”