SPIO‐enhanced 2D‐TOF MR angiography of the portal venous system: Results of an intraindividual comparison

Abstract

The purpose of this study was to investigate whether MR angiography (MRA) of the portal venous system may be improved by means of superparamagnetic iron oxides (SPIOs) during accumulation phase imaging and to study the underlying contrast mechanisms. MRA of the portal venous system was performed on 48 patients before and after intravenous injection of a new SPIO (Resovist, Schering AG, Berlin, Germany). Resovist, as a predominantly liver parenchymal darkening agent on T2-weighted MR images with uptake into the reticuloendothelial cell system, was administered intravenously by bolus injection of 8 to 12 micromol Fe/kg body weight. Patients were scanned with breath-hold coronal and axial two-dimensional (2D) time of flight (TOF) MRA (TR = 31.0 msec, TE = 9.8 msec, flip angle (FA) = 50 degrees, and 6.9-second acquisition time per section) sequences. Signal intensity values of liver parenchyma, the portal venous system, and background were obtained for quantitative analysis. The clinical relevance of additional plain and contrast-enhanced MRA studies for surgical planning was assessed by independent reading of three readers. Liver signal-to-noise ratio (SNR) significantly decreased following iv injection of Resovist; however, SNR values of the portal veins or hepatic veins did not change significantly. Visibility of the portal venous system improved significantly (tertiary branches visible: pre in 15.2% versus post in 87.0% of patients). Resovist-enhanced 2D-TOF MRA may improve planning of liver resections by better demonstrating the relationship of central liver lesions and vessels on source images. The decrease in liver SNR at a constant vessel SNR after iv injection of Resovist improves MRA of the liver. SPIO-enhanced 2D-TOF MRA scans are superior to plain 2D-TOF MRA studies and may be added for the workup of preoperative patients.

Inflammation as a Cardiovascular Risk Factor

“…Superparamagnetic iron oxide (SPIO) techniques have also been used to improve MR angiography of the venous system. 27 SPIO improves contrast and provides a larger temporal window for image acquisition. Using this technique, Ruehm et al were able to show macrophage accumulation in the aorta of rabbits before atherosclerotic lesions were detected.…”

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

“…Previous studies assessing other SPIO or USPIO contrast agents did not report detailed information on clotting parameters. In phase 3, bolus injections (8±12 mmol Fe/kg body weight; 0.9±1.4 ml) were performed by preloading the contrast agent into a connecting intravenous line and flushing the line with 10 ml saline within 3 sec; no cardiovascular side effects were seen [17].…”

Contrast-enhanced 3D-MRA of the upper abdomen with a bolus-injectable SPIO (SH U 555 A)

“…The new bolus injectable SPIO SH U 555 A is characterized by a biexponential blood-half life of 3.9-5.8 minutes for the fast initial phase accounting for about 80% of the initial concentration and 2.4-3.6 hours for the second phase (14). The compound has been proved to improve the detection of focal liver lesions and to demonstrate T1 shortening effects during the perfusion phase and has shown no significant cardiovascular changes during or following rapid injection (14)(15)(16). The potentials of SH U 555 A for dynamic-contrast enhanced 3D-MRA have not yet been investigated.…”