Todd C. Soesbe1, Navin Bansal2, Ananth V. Annapragada3, Ketan B. Ghaghada3, Zoltan Kovacs1, A. Dean Sherry1,4
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States; 2Department of Radiology, Indiana University School of Medicine, Indianapolis, IN, United States; 3School of Health Information Sciences, The University of Texas at Houston, Houston, TX, United States; 4Department of Chemistry, The University of Texas at Dallas, Dallas, TX, United States
Liposomal delivery of MR contrast agents offers improved steady-state imaging and signal-to-noise due to their long blood circulation life-time. Also, the relative small size of the liposomes ( 100 nm in diameter) allows them to have direct uptake in certain tumor lines that exhibit "leaky" vasculature (e.g. MBA-MD-231 breast cancer cells). The 1H methyl group of TmDOTMA has a chemical shift that is about -100 ppm away from bulk water. This TmDOTMA peak can be imaged using chemical shift selective (CHESS) techniques in which the water signal is completely absent. By using this method we can obtain "waterless" MR images where the only signal is due to the TmDOTMA filled liposomes. This is analogous to images obtained in nuclear medicine where the only signal is from the radioactive isotope. Liposomal TmDOTMA imaging has the potential to produce high resolution MR angiograms and molecular targeted images that are not contaminated by the bulk water signal. We explored this hypothesis by injecting a 5.8 mM solution of TmDOTMA liposomes, both intravenously and intratumorally, into a tumor-bearing mouse.