MAGNETIZATION-TRANSFER IMAGING OF NORMAL AND ABNORMAL LIVER AT 0.1T

RATIONAL AND OBJECTIVES. Magnetization transfer (MT) contrast is a new technique that may improve contrast in magnetic resonance imaging. Hi gh-protein tissues have a greater MT effect, resulting in a decrease i n signal intensity. This study evaluates the MT technique on normal an d abnormal liver tissue on a low-field system. The magnitude of the ma gnetization transfer was studied to determine its effect on image visu alization and tissue characterization. METHODS. Ten volunteers and 25 patients with benign and malignant liver pathology, including left lat eral segment hepatectomy, were imaged on a 0.1 T system. Gradient-reca lled-echo T2-weighted sequence pairs were obtained with and without MT pulse saturation. Signal intensity measurements were made using regio n-of-interest tracings in liver, spleen, skeletal muscle, fat, and sel ected liver pathology. Liver-to-lesion contrast ratios and conspicuity changes were analyzed. RESULTS. The average signal intensity decrease for normal liver was .27. Skeletal muscle demonstrated the greatest M T effect (.48), while fat showed minimal (.01) MT change. Two hemangio mas and two liver cysts showed a small MT effect (.13 and .02, respect ively). Of the malignant lesions imaged, melanoma metastases showed a mean MT effect of .34, while hepatomas showed mean effect of .15. Edem atous liver tissue had an intermediate mean effect of .18. CONCLUSIONS . While T2 sequences are more versatile for standard liver imaging, an MT sequence may be helpful for tissue characterization in specific im aging situations. Melanoma metastases and hepatomas demonstrated signi ficant MT effect and increased conspicuity of the malignant lesions.