MR imaging of focal nodular hyperplasia of the liver: value of contrast-enhanced dynamic study.

To clarify the role of MR imaging of hepatic focal nodular hyperplasia (FNH), MR images of 11 patients with 13 FNH were retrospectively reviewed. MR imaging with T1- and T2-weighted spin echo sequences was performed for all lesions. Dynamic studies using the SPGR technique followed by postcontrast delayed T1-weighted images were performed in four patients with five lesions. Gd-DTPA enhanced T1-weighted images were obtained in five patients with six lesions. Two patients with single lesions received no contrast agent. The signal intensity, morphologic appearance, and enhancement patterns were evaluated. Dynamic MR study revealed homogeneous early vigorous enhancement and prolonged enhancement in all five lesions. On T1-weighted images, three lesions were hypointense, six were isointense, and four were hyperintense to the surrounding hepatic parenchyma. On T2-weighted images, four lesions were isointense and nine were hyperintense. A central scar was identified in eight lesions and showed delayed enhancement. It is concluded that dynamic MR studies are mandatory for diagnosing FNH.