title: Determination of liver-specific r2 * of a highly monodisperse USPIO by (59) Fe iron core-labeling in mice at 3 T MRI.
abstract: Accurate determination of tissue concentration of ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) using T2 * MR relaxometry is still challenging. We present a reliable quantification method for local USPIO amount with the estimation of the liver specific relaxivity r2 * using monodisperse (59) Fe-core-labeled USPIO ((59) FeUSPIO). Dynamic and relaxometric in vivo characteristics of unlabeled monodisperse USPIO were determined in MRI at 3 T. The in vivo MR studies were performed for liver tissue with (59) FeUSPIO using iron dosages of 9 (n = 3), 18 (n = 2) and 27 (n = 3) µmol Fe kg(-1) body weight. The R2 * of the liver before and after USPIO injection (∆R2 *) was measured and correlated with (59) Fe activity measurements of excised organs by a whole body radioactivity counter (HAMCO) to define the dependency of ∆R2 * and (59) FeUSPIO liver concentration and calculate the r2 * of (59) FeUSPIO for the liver. Ultrastructural analysis of liver uptake was performed by histology and transmission electron microscopy. ∆R2 * of the liver revealed a dosage-dependent accumulation of (59) FeUSPIO with a percentage uptake of 70-88% of the injection dose. Hepatic ∆R2 * showed a dose-dependent linear correlation to (59) FeUSPIO activity measurements (r = 0.92) and an r2 * in the liver of 481 ± 74.9 mm(-1) s(-1) in comparison to an in vitro r2 * of 60.5 ± 3.3 mm(-1) s(-1) . Our results indicate that core-labeled (59) FeUSPIO can be used to quantify the local amount of USPIO and to estimate the liver-specific relaxivity r2 *.
authors: Department of Diagnostic and Interventional Radiology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany.
authors: Nina
authors: N
authors: Raabe
authors: Evelyn
authors: E
authors: Forberich
authors: Barbara
authors: B
authors: Freund
authors: Oliver T
authors: OT
authors: Bruns
authors: Markus
authors: M
authors: Heine
authors: Michael G
authors: MG
authors: Kaul
authors: Ulrich
authors: U
authors: Tromsdorf
authors: Lena
authors: L
authors: Herich
authors: Peter
authors: P
authors: Nielsen
authors: Rudolph
authors: R
authors: Reimer
authors: Heinrich
authors: H
authors: Hohenberg
authors: Horst
authors: H
authors: Weller
authors: U
authors: U
authors: Schumacher
authors: Gerhard
authors: G
authors: Adam
authors: Harald
authors: H
authors: Ittrich
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005290:Ferric Compounds / Q000737:chemistry / Q000494:pharmacology; D007503:Iron Isotopes / Q000737:chemistry / Q000494:pharmacology; D007553:Isotope Labeling / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D016513:Mice, SCID; D053758:Nanoparticles / Q000737:chemistry*; D011859:Radiography
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; D007503:Iron Isotopes; C000499:ferric oxide
keywords: 3T MRI; USPIO; animal study; quantification; relaxometry