Pseudolesions at T1-weighted gradient-echo imaging after administration of superparamagnetic iron oxide: comparison with portal perfusion abnormalities at CT during arterial portography.

Purpose: To compare specific findings at T1-weighted gradient-echo (GRE) magnetic resonance (MR) imaging performed after administration of superparamagnetic iron oxide (SPIO) with nontumorous regional portal perfusion abnormalities seen at computed tomography (CT) during arterial portography (CTAP).

Materials And Methods: The results of CTAP, MR imaging, and surgery were compared in 19 patients with liver metastases and five with benign liver tumors. MR imaging was performed by using turbo spin-echo (SE) sequences and a GRE sequence before and after infusion of SPIO.

Results: At CTAP, 34 nontumorous portal perfusion defects ("straight line sign," pseudolesions) were seen. After intravenous administration of SPIO, 18 nontumorous signal intensity differences were seen on T1-weighted GRE images in corresponding locations. No corresponding nontumorous signal intensity differences were seen on unenhanced MR images. The mean signal-to-noise ratio on the SPIO-enhanced GRE images was reduced from 26.3 to 16.6 in the areas of nontumorous signal intensity differences, whereas that in areas of normal portal perfusion (normal CTAP findings) was reduced to 10.2.

Conclusion: Impaired portal perfusion decreased the uptake of SPIO in histopathologically normal regions of liver parenchyma. Resultant differences in signal intensity were better visualized on GRE than on turbo SE images.