Qun Zhao

Contrast-enhanced MRI (CEMRI) using paramagnetic nanoparticles has been the subject of extensive research since the early 1990s. Novel CE-MRI applications using biocompatible and biodegradable nanoparticles in bioimaging include cancer diagnosis, treatment evaluation, drug delivery, molecular and cellular imaging area etc.

The paramagnetic nanoparticles are used to magnetically label cells, providing researchers with the ability to monitor the migration and homing of the cells in living tissues with MRI. Intracellular nanoparticles placed in a magnetic field cause signal dephasing because of the inhomogeneities induced near the cells. The disruption of the magnetic field extends to a much larger distance than the actual size of the nanoparticles, making it possible to detect single cells in vivo. However, on - and - weighted MR images, paramagnetic nanoparticles appear as signal voids or hypointense regions with associated with blooming artifacts. Therefore differentiation between signal loss caused by the intracellular nanoparticles and native low signals in tissue is challenging.

Positive-contrast techniques produce images with hyperintensities in the vicinity of paramagnetic nanoparticles. Researchers have been investigating different methods to provide positive contrast, such as gradient-compensation techniques (White Marker), Off-resonance techniques (IRON), and Post-processing techniques (SGM), etc.

In this project, with availability of a top quality GE 3T magnet located at the BIRC, students will have an opportunity to learn fundamentals on contrast-enhanced MR imaging using paramagnetic nanoparticles, as well as post-processing techniques to generate positive contrast.