title: Fast low-angle positive contrast steady-state free precession imaging of USPIO-labeled macrophages: theory and in vitro experiment.
abstract: The feasibility of imaging macrophages labeled with ultrasmall superparamagnetic iron-oxide nanoparticles (USPIO) with fast low-angle positive contrast steady-state free precession (FLAPS) was investigated through theory and in vitro experiment. Human macrophage cells were labeled with USPIO and imaged at 1.5 T. The metric "visibility," which combines magnitude and spatial extent of positive contrast, was used to evaluate the images. Negative contrast steady-state free precession (SSFP) and gradient-echo (GRE) imaging were also evaluated. Positive contrast was observed for relatively high concentrations of labeled cells for flip angles less than alpha=25 degrees . Theoretical and experimental results indicate that positive visibility (VIS(POS)) was maximized at alpha=10 degrees and 15 degrees. Low flip angle SSFP also provided negative contrast comparable to standard SSFP and GRE imaging. Results suggest that USPIO-labeled macrophages are capable of producing the conditions necessary for positive contrast with FLAPS at clinical field strength (1.5 T) and resolution (0.8x0.8x3 mm(3)).
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA. nicolemascheri@gmail.com
authors.forename: Nicole
authors.initials: N
authors.lastname: Mascheri
authors.forename: Rohan
authors.initials: R
authors.lastname: Dharmakumar
authors.forename: Zhuoli
authors.initials: Z
authors.lastname: Zhang
authors.forename: Tatjana
authors.initials: T
authors.lastname: Paunesku
authors.forename: Gayle
authors.initials: G
authors.lastname: Woloschak
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
mesh_terms: D000465:Algorithms; D002478:Cells, Cultured; D003198:Computer Simulation; D003287:Contrast Media; D003911:Dextrans; D052203:Ferrosoferric Oxide; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008264:Macrophages / Q000166:cytology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling / Q000379:methods
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10; D052203:Ferrosoferric Oxide