In order to improve the detection specificity of iron oxide nanoparticles (IONPs) delivered to tumors, we embedded saturation pulses into the sweep imaging using Fourier transformation (SWIFT) sequence to suppress long T2 tissues and fat. Simulation of the Bloch equation was first conducted to study behavior of the saturation pulses of various lengths under different T2 and off-resonance conditions. MR experiments were then conducted using in vivo mouse xenografts and a phantom consisting of IONPs, vegetable oil, and explanted tumor specimen, without and with long T2 suppression under a 7T magnetic field. For the in vivo study, arginine-glycine-aspartate (RGD) coated 10nm IONPs (RGD-IONPs) were delivered to tumors implanted in nude mice through both intra-tumor and intravenous injections. Histological studies confirmed that RGD-IONPs efficiently homed to tumors through RGD-integrin interaction. Compared to conventional SWIFT, the proposed method resulted in sufficient suppression on long T2 species but less influence on short T2 species. For both the in vivo and ex vivo studies, significantly improved contrast-to-noise ratio (CNR) was achieved between the IONPs and the long T2 species.
Bibliographical noteFunding Information:
We gratefully acknowledge support from the following grants: Faculty Research Grant from the University of Georgia (Zhao), S10RR023706 from the National Center for Research Resources, and 5R00CA153772 from NIH (J. X.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources. In addition we wish to thank Dr. Michael Garwood, Dr. Curtis Corum, and Dr. Djaudat Idiyatullin from the Center of Magnetic Resonance Research at the University of Minnesota, for providing their supports on the SWIFT sequence. We also thank Dr. Khan Hekmetyar for assisting MR scan at the BioImaging Research Center (BIRC) of the University of Georgia.
- Iron oxide nanoparticles
- Sweep imaging with Fourier transformation