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Peripheral washout: a sign of malignancy on dynamic gadolinium-enhanced MR images of focal liver lesions.

PURPOSE
To assess the value of peripheral washout of contrast medium in differentiating benign from malignant focal liver lesions.


MATERIALS AND METHODS
One hundred two patients, 49 with malignant liver tumors and 53 with benign lesions, underwent unenhanced T1- and T2-weighted and dynamic gadolinium-enhanced magnetic resonance (MR) imaging. Dynamic contrast material-enhanced MR imaging was performed before and up to 10 minutes after intravenous administration of a bolus of gadopentetate dimeglumine (0.1 mmol/kg).


RESULTS
On the dynamic contrast-enhanced images, 12 of the 49 malignant tumors had a rim that was hypo-intense to the center of the lesion ("peripheral washout" sign); this rim was best seen 10 minutes after administration of contrast material. This sign was absent in the remaining 37 malignant tumors as well as in all 53 benign lesions (P < .001). The peripheral washout sign had a sensitivity of 24.5% and a specificity of 100% in the diagnosis of malignancies of the liver. The malignant tumors with peripheral washout showed no difference in signal intensity between the periphery and the center on the unenhanced T1- and T2-weighted images.


CONCLUSION
Peripheral washout is a specific sign of malignancy in dynamic gadolinium-enhanced MR imaging of liver lesions.