Magnetization transfer contrast of hepatic lesions in breath-hold gradient-echo images of different T1 weighting.

Abstract

Seventeen patients with hepatic lesions [six metastases from colon, breast, and gallbladder carcinoma; one gallbladder carcinoma; five hepatocellular carcinoma; three focal nodular hyperplasia (FNH); one adenoma; and one cyst] were examined by MR breath-hold two-dimensional gradient-echo imaging to assess the potential of magnetization transfer contrast (MTC) for improved conspicuity and classification. Imaging sequences were applied with and without irradiation of off-resonant radiofrequency (RF) prepulses, but other parameters were unchanged. Therefore, quantitative assessment of MTC could be performed. In contrast to former examinations of other researchers, no significant difference of MTC was found between malignant liver lesions and benign lesions as FNH or adenoma. MTC might provide differentiation between hemangioma and cysts versus solid tumors, but MTC is not capable of distinguishing benign and malignant types of solid liver tumors. Effects of unchanged MTC prepulses on signal intensity of normal liver tissue and most lesions were more pronounced for nearly proton density-weighted fast low-angle shot (FLASH) images than for T1-weighted FLASH images, obtained by using higher excitation flip angles. Liver-to-lesion contrast could not be improved clearly by MTC prepulses. The contrast between liver and lesions in the gradient-echo breath-hold images was compared with standard T1- and T2-weighted spin-echo images. Liver-to-lesion contrast in the breath-hold images was found to be inferior to T2-weighted spin-echo images in 14 of 17 cases. Lesion conspicuity in regions near the diaphragm was better in breath-hold images, because problems with marked breathing motion (as in standard imaging) could be avoided.