Comparison of iron oxide particles (AMI 227) with a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) for both phantom and rat brain at 1.5 tesla

Abstract

The goal of the study was to compare, in phantom and normally perfused rat brain tissue, a superparamagnetic iron oxide particle‐based contrast agent (AMI 227) with a low‐molecular‐weight gadolinium chelate, gadolinium tetraazacyclododecanetetraacetic acid (Gd‐DOTA), in two susceptibility contrast magnetic resonance imaging (MRI) modes [fast low‐angle shot sequence (FLASH) and echoplanar imaging (EPI)]. A phantom consisting of dilution series of both contrast agents was manufactured. Dilutions were obtained with isotonic serum from the available agent solutions (0.5 mmol Gd/mL Gd‐DOTA; 350 μmol Fe/mL AMI 227). Eighteen rats were studied. Contrast agent (0.1 mL) was bolus injected in each rat, and dynamic MRI was performed (first pass of the contrast agent) in rat brain. The doses of AMI 227 injected were extrapolated from the phantom experiment: 0.2 mmol/kg body weight of Gd‐DOTA and 7, 14, and 28 μmol Fe/kg body weight of AMI 227 were injected. For both sequences, signal‐to‐noise ratios (S/N) were measured on each tube of the phantom and on rat brain from each image of the dynamic imaging. S/N was plotted versus contrast dilution (phantom) and versus time (rats). In the FLASH sequence, a well‐shaped curve (S/N decrease, S/N peak decrease, S/N increase) of the first pass of the contrast agent was demonstrated for Gd‐DOTA and for AMI 227 (7 μmol Fe/kg body weight ). In the EPI sequence, a well‐shaped curve was demonstrated for Gd‐DOTA, and a plateau effect was noted for both concentrations of AMI 227. With the FLASH technique, dynamic susceptibility contrast imaging of rat brain can be performed with very low concentrations of AMI 227 compared with the Gd‐DOTA concentration (0.2 mmol Gd/kg body weight) used in clinical practice. This could be of interest in perfusion imaging, because it may allow for first‐pass susceptibility imaging after administration of a small volume in a narrow bolus.J. Magn. Reson. Imaging 1999; 9:447–453. © 1999 Wiley‐Liss, Inc.

The Role of Preload and Leakage Correction in Gadolinium-Based Cerebral Blood Volume Estimation Determined by Comparison with MION as a Criterion Standard

“…Similar to previously investigated iron oxide contrast agents, 39,40 high-molecular-weight intravascular iron-containing agents with large susceptibility effects (eg, ferumoxytol) would eliminate the need for any leakage correction entirely. 41,42 However, they may introduce practical issues with regard to T1-weighted postcontrast imaging, given that extravasation accounts for most enhancement associated with conventional Gd-based agents.…”

High‐resolution in vivo CBV mapping with MRI in wild‐type mice

“…To obtain high‐resolution CBV mapping in this study, monocrystalline iron oxide nanoparticle (MION; MGH Center of Molecular Imaging Research, MA) was used because of its strong intravascular susceptibility perturbation in the crystalline state (8, 9, 17). MION has a long intravascular halflife, which enables a long postcontrast acquisition of high‐resolution T 2 ‐weighted images to be obtained.…”

“…The steady state method based on the T 1 ‐weighted images only relies on the blood signal increase due to intravascular T 1 shortening contrast agent (7), thus limiting the measurement sensitivity and spatial resolution. The recent development of ultrasmall superparamagnetic iron oxide (USPIO) CAs with a long halflife has made it possible to induce strong and sustained intravascular susceptibility perturbations in surrounding tissue, as reflected by an increase of transverse relaxation rates, i.e., Δ R 2 and Δ R (8, 9). These CAs have been employed by others to study brain functional activation based on local CBV increases in rats and mice (10–12).…”

Targeted dual-contrast T1- and T2-weighted magnetic resonance imaging of tumors using multifunctional gadolinium-labeled superparamagnetic iron oxide nanoparticles

“…5c). After Gd labeling, the r 2 relaxivity values of the NPs decreased obviously, indicating that the paramagnetic Gd chelates interfered with the T 2 relaxation processes of the neighboring magnetite NPs [37,38]. Even so, their T 2 contrast effect was sufficiently strong to generate negative contrast enhancement on the MR images in vivo.…”