title: Effect of iron oxide nanoparticles coating type on the relationship between nanoparticles concentration and signal intensity in inversion recovery T1-weighted MRI.
abstract: BACKGROUND
  Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are used as blood pool contrast agent for magnetic resonance angiography and perfusion imaging. Our aim in this study was to investigate the effect of the two coating types of iron oxide nanoparticles on the relationship between nanoparticles concentration and signal intensity (SI) in T1-weighted MR images.
  
  
  METHODS
  Different concentrations of the polyethylene glycol (PEG), and carboxydextran-coated iron oxide nanoparticles were imaged using inversion recovery Turbo-FLASH (Turbo fast low-angle shot) pulse sequence with inversion times (TIs) of 300-900 ms (interval of 100 ms). The maximum non-linear and linear relationship between the corrected SI (after non-uniformity correction) and the concentration of the two coated nanoparticles were calculated in T1-weighted images.
  
  
  RESULTS
  The maximum non-linear relationship between the corrected SI and the concentration of the PEG, and carboxydextran-coated nanoparticles were obtained at concentrations of 400 and 200 μmol Fe/L at a TI of 900 ms, respectively. In addition, the maximum linear relationship between the corrected SI and the concentration of the PEG, and carboxydextran-coated nanoparticles (R2=0.99) appeared at 228.184 and 205.654 μmolFe/L with a TI of 300 ms, respectively.
  
  
  CONCLUSIONS
  The maximum non-linear corrected SI of the carboxydextran-coated nanoparticles was slightly higher than that of the PEG-coated nanoparticles at similar TIs. However, the PEG-coated nanoparticles were better than the carboxydextran-coated nanoparticles as a T1 contrast agent for perfusion measurements.
authors.affiliation: Assistant Professor, Department of Radiology, Faculty of Paramedicine, Tabriz University of Medical Sciences, Tabriz, Iran. gharehaghaji@gmail.com ; gharehaghagi@yahoo.com.
authors.forename: Nahideh
authors.initials: N
authors.lastname: Gharehaghaji
authors.affiliation: Associate Professor, Department of Radiology, Faculty of Paramedicine, Tabriz University of Medical Sciences, Tabriz, Iran, and Faculty of Paramedicine, Tehran Medical Sciences Branch, Islamic Azad University, Tehran, Iran. mnazarpoor@yahoo.co.uk ; nazarpoorm@tbzmed.ac.ir.
authors.forename: Mahmood
authors.initials: M
authors.lastname: Nazarpoor
authors.affiliation: MSc of Medical Physics, Department of Medical Physics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Hodaiseh
authors.initials: H
authors.lastname: Saharkhiz
keywords: Coating; Inversion recovery; Iron oxide nanoparticles; MRI; T1-weighted image