BME.08 A Mouse Earplug for Functional MRI at 9.4T

• Michelle Alice Chavez
• Steven Ha
• Nara Im
• Jeremy Lentz
• Will Stout

“Functional connectivity magnetic resonance imaging (fcMRI) is a powerful tool for investigating brain connectomes in animals. Echo planar imaging (EPI) is a widely used technique in fcMRI due to its speed, acquiring images in seconds instead of minutes by only using a single radio frequency (RF) excitation pulse. However, magnetic susceptibility artifacts can occur during imaging, especially in ultra-high-strength magnetic fields such as utilizing a 9.4 T MRI machine. These artifacts are caused by the presence of air in the ear canal and can negatively affect the quality of imaging. Mitigation of these artifacts would aid in the understanding of and diagnosis of a variety of neurological diseases, such as Alzheimer’s. In this study, a solution is proposed to mitigate susceptibility artifacts during high-strength magnetic field EPI imaging of the mouse brain. The proposed solution involved using 3D-printed resin earplugs and fluorocarbon oil in the ear canals of anesthetized mice. The earplug is designed to reduce the amount of air in the mouse ear canal, which in turn mitigates magnetic susceptibility artifacts due to the paramagnetic properties of air. This method aimed to demonstrate the efficacy of the solution by comparing the signal-to-noise ratio (SNR) of different regions of interest (ROIs) in both sides of brain images with and without the device across several MRI imaging trials. Although there were observed improvements in both qualitative and quantitative aspects of imaging quality with the use of the proposed device, the differences were not statistically significant, and more data are required to arrive at a conclusive outcome. Nonetheless, the study suggests that utilizing 3D- printed resin earplugs and fluorocarbon oil is a promising solution for mitigating susceptibility artifacts in ultra-high-strength magnetic field EPI imaging of mouse brain connectomes. Further trials are necessary to ascertain the benefits and limitations of this approach. The study highlights the importance of enhancing imaging techniques to better understand and diagnose neurological diseases in humans by making observations in mice using fcMRI.
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