MAGNETIZATION-TRANSFER CONTRAST OF HEPATIC-LESIONS IN BREATH-HOLD GRADIENT-ECHO IMAGES OF DIFFERENT T1 WEIGHTING

Seventeen patients with hepatic lesions [six metastases from colon, br east, and gallbladder carcinoma; one gallbladder carcinoma; five hepat ocellular carcinoma: three focal nodular hyperplasia (FNH); one adenom a; and one cyst] were examined by MR breath-hold two-dimensional gradi ent-echo imaging to assess the potential of magnetization transfer con trast (MTC) for improved conspicuity and classification. Imaging seque nces were applied with and without irradiation of off-resonant radiofr equency (RF) prepulses, but other parameters were unchanged. Therefore , quantitative assessment of MTC could be performed. In contrast to fo rmer examinations of other researchers, no significant difference of M TC 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 be nign and malignant types of solid liver tumors. Effects of unchanged M TC prepulses on signal intensity of normal Liver tissue and most lesio ns were more pronounced for nearly proton density-weighted fast low-an gle shot (FLASH) images than for T1-weighted FLASH images, obtained by using higher excitation flip angles. Liver-to-lesion contrast could n ot be improved clearly by MTC prepulses. The contrast between liver an d lesions in the gradient-echo breath-hold images was compared with st andard 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 mar ked breathing motion (as in standard imaging) could be avoided.