Recent technical and clinical advances in MR of the liver are reviewed with special reference to the role of MR as a primary screening technique for detection of space-occupying lesions, especially
metastases. The major current problem in upper abdominal MR imaging is physiologic motions, and this appears to have been effectively solved by newly introduced pulse-sequence and timing-parameter strategies. Short-TR/TE spin-echo sequences with extensive signal averaging and heavy T1-weighting produce images with exceptional anatomic detail and
liver-cancer contrast differences. With this sequence superior sensitivity for
liver-cancer detection has been shown in quantitative signal-difference to noise comparisons with other pulse sequences and in clinical comparisons with CT. MR discovered 14% more individual
metastases and 3% more patients with
liver cancer than CT in a blinded comparative study of 142 patients undergoing both exams. MR also showed greater specificity (98%) than CT (91%) in distinguishing patients without liver
metastases. Differentiation of
hemangioma from
metastases was possible with greater than 90% specificity by using heavily T2-weighted sequences. Use of a fast-scan, gradient-recalled echo technique can also produce good-quality, multislice, T1-weighted studies of the liver in 20 sec--a breath-hold. MR
contrast agents (such as
gadolinium-DTPA and reticuloendothelial-system-specific, superparamagnetic
ferrite-
iron-oxide particles) offer further promise for enhanced sensitivity for
liver-cancer detection. When optimal pulse sequences are employed, MR can now be appropriate as a primary screening method for detecting
liver neoplasms.