Abstract #0229

In Vivo MR and PET Imaging of a Highly Sensitive Polymeric PARACEST Contrast Agent

Todd C. Soesbe¹, Yunkou Wu², Guiyang Hao³, Xiankai Sun¹, A. Dean Sherry^1,2

¹Advanced Imaging Research Center, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA; ²Department of Chemistry, The University of Texas at Dallas, Dallas, TX, USA; ³Department of Radiology, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA

Chemical exchange saturation transfer (CEST) agents create contrast in MR images by exchanging their saturated lanthanide bound protons with those of bulk water. These agents have great potential to further extend the functional and molecular imaging capabilities of MR. Polymeric paramagnetic CEST (PARACEST) agents have recently been prepared by our group. The polymeric agents increase the CEST effect by creating a higher concentration of lanthanide ions at the target site. These agents offer an order on magnitude improvement in sensitivity which greatly reduces in vivo dose levels. The improved sensitivity of the polymeric agents also helps overcome the magnetization transfer (MT) effect due to endogenous macromolecules in tissue, which can mask the CEST effect. We present the first in vivo images of a polymeric Eu3+ PARACEST agent using a simple fast spin echo pulse sequence. We also show that this agent could be used for simultaneous PET/MR imaging by labeling the polymer with Cu-64.