MR imaging of the liver and spleen: a comparison of the effects on signal intensity of two superparamagnetic iron oxide agents

Abstract

We compared the effects of two superparamagnetic iron oxide (SPIO) contrast agents, ferumoxides and SHU-555A, in MR imaging of the liver and spleen. Thirty-six patients with known malignant lesions of the liver underwent T 2W turbo spin-echo (TSE) and T 1WGRE FLASH opposed-phase imaging before and after SPIO injection on a 1.0 T MR system. Post-ferumoxides images were obtained in 18 patients 90 min after infusion of 15 μmmol Fe/kg of the agent. In 18 other patients SHU-555A was administered as a rapid bolus at a dose of 7.0∼12.9 μmmol Fe/kg. T 1WGRE FLASH images were obtained immediately, 30 s and 480 s and T 2WTSE images 10 min after injection. Signal intensity of the liver, spleen, and malignant liver lesions before and after SPIO was measured with operator-defined regions of interest. The effects of ferumoxides and SHU-555A were measured as the percentage signal intensity change (PSIC) and in the malignant liver lesions additionally as changes in lesion-to-liver contrast-to-noise ratio (ΔDCNR). On T 2W TSE images, there was no significant difference between the two agents in signal loss of liver parenchyma ( p > 0.05). The signal loss in the spleen produced by ferumoxides was greater than with SHU-555A ( p < 0.05). Both SPIO agents produced a significant increase in the CNR of malignant liver lesions. Δ CNR was slightly greater with ferumoxides than with SHU-555A ( p < 0.05). On T 1WGRE FLASH images, a slight decrease of liver SI induced by both agents was found on late post-SPIO images. No significant difference of liver PSIC between the two SPIO agents was noted on T 1W images. The SI of spleen was significantly increased with both agents on T 1W images and no difference in PSIC of spleen was noted ( p > 0.05). The T 1 and T 2 effects produced by ferumoxides and SHU-555A were comparable in the liver although ferumoxides produced a stronger T 2 effect in the spleen.