Characterization of focal liver lesions with superparamagnetic iron oxide-enhanced MR imaging: value of distributional phase T1-weighted imaging

Abstract

Objective: To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

Materials and methods: Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas (HCC), 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

Results: During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p <.05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

Conclusion: T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.

Fig. 1

Liver hemangioma in a 67-year-old woman. A. Precontrast T1-weighted in-phase gradient-echo image depicts a round hypointense lesion (arrow) in the right lobe of the liver. B. Precontrast T2-weighted turbo spin-echo image shows a hyperintense lesion (arrow) in the liver. C. Ferumoxides-enhanced T1-weighted in-phase gradient-echo image obtained during the distributional phase demonstrates positive enhancement of the lesion (arrow), similar to that of the intrahepatic portal vein (open arrow). Note positive enhancement of the abdominal aorta (arrowhead). D. Ferumoxides-enhanced T2-weighted turbo-spin echo image shows reduced intensity of the lesion (arrow) compared to precontrast image (A).

Fig. 2

Liver metastasis in a 67-year-old woman with gastric cancer. A. Precontrast T2-weighted turbo spin-echo image shows a hyperintense nodule (arrow) in the right lobe of the liver. B. Postcontrast T1-weighted out-of-phase image demonstrates rim enhancement (arrow) of the peripheral portion of the lesion, which is hypointense to the liver. Note positive enhancement of the intrahepatic portal vein (small arrowheads) and aorta (arrowhead). C. Postcontrast T1-weighted in-phase image shows that the lesion (arrow) has become hyperintense to the liver. D. Postcontrast T2*-weighted gradient-echo image obtained during the accumulation phase demonstrates markedly improved lesion (arrow)-to-liver contrast compared to precontrast T2-weighted image.

Fig. 3

Surgically-proven cholangiocarcinoma in segment 5 of the liver. A. Precontrast T2-weighted turbo spin-echo image shows a heterogeneously hyperintense lesion (arrows) with mild capsular retraction in the right lobe of the liver (arrowhead). B. Precontrast T1-weighted in-phase gradient-echo image depicts a hypointense mass (arrow). C. On this T1-weighted out-of-phase gradient-echo image obtained after the administration of ferumoxides, the lesion shows peripheral rim enhancement (arrows). D. T1-weighted in-phase gradient-echo image obtained after the administration of ferumoxides shows that the lesion (arrows) has become slightly hyperintense to the liver. E. On this T2*-weighted gradient-echo image obtained after the administration of ferumoxides, the lesion (arrow) has become very hyperintense to the liver. Note that this accumulation phase image provides excellent contrast and lesion conspicuity.

Fig. 4

A 65-year-old man with biopsy-proven hepatocellular carcinoma in the right lobe of the liver. A. Precontrast T1-weighted out-of-phase gradient-echo image depicts a hyperintense tumor (arrow) with a hypointense capsule in the right lobe of the liver. B. Postcontrast T1-weighted out-of-phase gradient-echo image obtained during the distributional phase shows that the lesion (arrow) is hyperintense compared to the liver, but much less hyperintense than the branches of the intrahepatic portal vein (open arrows). C. Postcontrast T1 in-phase gradient-echo image obtained during the distributional phase shows that the lesion (arrow) has become more hyperintense than the liver but is still less hyperintense than the branches of the portal vein (open arrows). Note the presence of multiple hypointense regenerating nodules in the liver parenchyma. D. Postcontrast T2*-weighted gradient echo image shows markedly improved lesion (arrow)-to-liver contrast due to the substantially decreased liver parenchymal signal.

Fig. 5

Lesion-to-liver contrast-to-noise ratio of focal hepatic lesions seen on T1-weighted in-phase and out-of-phase gradient-echo images obtained during the distributional phase