2019 Volume 32 Issue 3 Pages 217-221
Magnetic resonance imaging (MRI) is used in clinical sites as an imaging diagnostic technique for visualizing organ and blood vessel structures in a non-invasive manner. The method of visualizing blood vessels in MRI is called MR angiography. Recently, high-resolution MRA has been developed by increasing the magnetic strength and improving the cooled receiving coil. However, the MR signals from microblood vessels are extremely weak, and so it is essential not only to improve the hardware but also to develop contrast agents specific for the microvasculature in order to realize high-resolution imaging with a high S/N ratio.
In our previous work, we developed fluorescein and Gd-chelate conjugated 8-arm polyethylene glycol as a polymeric contrast agent for visualizing a microvasculature. The contrast agent forms a self-assembled structure in a high concentration condition, and the structure collapses when diluted. This property enables the blood circulation time of the contrast agent to be increased, and we succeeded in visualizing a microvessel structure of approximately 100 μm in diameter, which could not be visualized by non-contrast MR imaging. In this article, we introduce the structural and physical properties of F-8-arm PEG-Gd, and discuss the MRA imaging results with and without contrast agents. The metabolism and toxicity of the agents are also mentioned. Based on these results and discussion, we explore the possibility of a new diagnostic method in the dental area based on the techniques for visualizing the microvasculature using polymeric contrast agents.
