Evaluation of portal MR angiography using superparamagnetic iron oxide

Abstract

The purpose of our research was to determine the effects of superparamagnetic iron oxide on MR imaging of the portal venous system. Eight piglets were examined in deep anaesthesia and respiratory arrest using a time-of-flight magnetic resonance fast low angle shot, two-dimensional angiography sequence at 1.5T, MR angiograms were acquired precontrast and after intravenous administration of a cumulative dose of 10, 20 and 40 mumol/kg SHU 555A, a superparamagnetic iron oxide contrast agent for MR imaging with a particle size of 60 nm. For each dose, two subsequent sets of scans were obtained and reconstructed by a maximum-intensity-projection algorithm. Hepatic parenchymal and portal venous signal intensities were measured, and portal vein contrast calculated for each set of scans. All examinations were visually rated as to portal vein contrast and homogeneity by two blinded observers. Receiver operating characteristics of both observers were analyzed. The contrast agent reduced hepatic parenchymal signal in a dose-dependent way. After a cumulative dose of 10 mumol iron oxide, hepatic parenchymal signal intensity decreased to 63 +/- 6% (average of measurements at 4 and 14 minutes, mean +/- standard error of the mean), after 20 mumol to 24 +/- 3%, and after 40 mumol to 12 +/- 1% of control. Intravascular signal in the left main portal vein branch increased to 117 +/- 6%, 127 +/- 10%, and 133 +/- 9% of control, respectively. The contrast-to-noise ratio of the portal vein improved (521 +/- 90%, 891 +/- 178%, and 995 +/- 201% of control in the left portal vein main branch). Intravascular signal intensities increased slightly. The combined effect improved contrast of the portal vein stem and its branches. Receiver operating characteristics analysis documented dose-dependency of contrast medium effects on portal venous contrast and intravascular homogeneity. Visual rating also indicated a positive effect on portal venous contrast. The superparamagnetic iron oxide agent improved portal venous contrast with surrounding hepatic parenchyma in this normal animal model, and could potentially result in more accurate diagnosis of portal venous pathology.

Hepatic MRI with SPIO: detection and characterization of focal liver lesions

“…This contrast mechanism of iron oxides is likely to be valid for a large time window following extraction of particles from the intravascular space into the Reticuloendothelial system (RES). Contrast-enhanced MR angiography scans during or immediately following intravenous injection of iron oxides with a low R2/R1 ratio using rapid 2D-or 3D-techniques may rather demonstrate similar intravascular signal changes as gadolinium chelates [37]. Alternatively, iron oxide particles with a longer blood half-life such as USPIO or monocrystalline iron oxide nanopolymers (MION) may be combined with breathhold MR angiography techniques [38].…”

Superparamagnetic Iron Oxide Nanoparticles in Biomedicine: Applications and Developments in Diagnostics and Therapy

“…Numerous preclinical and several clinical studies describe their use both in MRA of individual vascular territories, such as pulmonary arteries [96], the aorta [80,97], coronary arteries [10,98,99], renal arteries [10], mesenterial and portal veins [100], hepatic veins [101], and the inferior vena cava [102], as well as in whole-body angiography of arteries and veins for assessing stenoses and thromboses [103]. Potential USPIO for clinical application are Supravist ® (SHU 555C, phase I, Bayer Healthcare Pharmaceuticals), AMI-227 (Sinerem ® , phase III), and VSOP-184 (phase I).…”

The utility of superparamagnetic contrast agents in MRI: theoretical consideration and applications in the cardiovascular system

“…This effect will induce both new possibilities as well as new problems compared with the CE-MRA using Gd chelates. The potential applications utilising this effect include imaging of the portal venous system 84,85 as well as imaging of deep venous thrombosis (DVT). [86][87][88] In addition, efforts have been made to image thrombi using both passive diffusion of USPIOs into nonendothelialized fresh thrombi 89 as well as active targeting of USPIOs via an RGD-peptide to the integrin IIB 3 , which is expressed when thrombi are formed.…”