Determination of liver‐specific r2* of a highly monodisperse USPIO by 59Fe iron core‐labeling in mice at 3 T MRI
We present a reliable quantification method for local USPIO amount with the estimation of the liver specific relaxivity r2* using monodisperse 59Fe‐core‐labeled USPIO (59FeUSPIO). 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 59FeUSPIO 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 59Fe activity measurements of excised organs by a whole body radioactivity counter (HAMCO) to define the dependency of ∆R2* and 59FeUSPIO liver concentration and calculate the r2* of 59FeUSPIO 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 59FeUSPIO with a percentage uptake of 70–88% of the injection dose. Hepatic ∆R2* showed a dose‐dependent linear correlation to 59FeUSPIO 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 59FeUSPIO can be used to quantify the local amount of USPIO and to estimate the liver‐specific relaxivity r2*. Copyright © 2014 John Wiley & Sons, Ltd.
Source: Contrast Media and Molecular Imaging - Category: Radiology Authors: Nina Raabe, Evelyn Forberich, Barbara Freund, Oliver T. Bruns, Markus Heine, Michael G. Kaul, Ulrich Tromsdorf, Lena Herich, Peter Nielsen, Rudolph Reimer, Heinrich Hohenberg, Horst Weller, U. Schumacher, Gerhard Adam, Harald Ittrich Tags: Full Paper Source Type: research