MR DIAGNOSIS OF HEPATIC METASTASES FROM NEUROENDOCRINE TUMORS VERSUS HEMANGIOMAS - RELATIVE MERITS OF DYNAMIC GADOLINIUM CHELATE-ENHANCED GRADIENT-RECALLED ECHO AND UNENHANCED SPIN-ECHO IMAGES

OBJECTIVE. Hepatic metastases from neuroendocrine tumors are often mar kedly hyperintense on unenhanced T2-weighted MR images, making their a ppearance similar to that of cavernous hemangiomas. In contrast, caver nous hemangiomas show characteristic enhancement on dynamic gadolinium chelate-enhanced gradient-recalled echo MR images. The purpose of thi s study was to determine the relative merits of dynamic gadolinium che late-enhanced gradient-recalled echo MR imaging versus MR imaging with unenhanced spin-echo pulse sequences for distinguishing between hepat ic metastases from neuroendocrine tumors and cavernous hemangiomas. MA TERIALS AND METHODS. The unenhanced spin-echo and dynamic gradient-rec alled echo MR images obtained after IV administration of a gadolinium chelate in 28 patients (14 patients with pathologically proven hepatic metastases from neuroendocrine tumors and 14 patients with hepatic ca vernous hemangiomas) were reviewed blindly and independently by three interpreters. Unenhanced spin-echo and dynamic gadolinium chelate-enha nced gradient-recalled echo MR images were compared for accuracy in ch aracterizing liver lesions. RESULTS. The most intense enhancement of h epatic metastases from neuroendocrine tumors was observed on early dyn amic gadolinium chelate-enhanced gradient-recalled echo MR images; enh ancement was peripheral in four patients, global and heterogeneous in seven patients, and global and homogeneous in three patients. On late dynamic gadolinium chelate-enhanced gradient-recalled echo MR images, enhancement of hepatic metastases from neuroendocrine tumors was predo minantly peripheral in five patients, global and heterogeneous in five patients, and global and homogeneous in four patients. Differentiatio n between cavernous hemangiomas and hepatic metastases from neuroendoc rine tumors was impossible in five cases with unenhanced spin-echo MR imaging alone, in five cases with dynamic gadolinium chelate-enhanced gradient-recalled echo MR imaging alone, and in no case with the combi nation of unenhanced spin-echo MR imaging and dynamic gadolinium chela te-enhanced gradient-recalled echo MR imaging. In comparison with unen hanced spin-echo MR imaging alone or dynamic gadolinium chelate-enhanc ed gradient-recalled echo MR imaging alone, the combination of unenhan ced spin-echo MR imaging and dynamic gadolinium chelate-enhanced gradi ent-recalled echo MR imaging allowed significantly (p < .001) clearer differentiation between hepatic metastases from neuroendocrine tumors and cavernous hemangiomas. CONCLUSION. Early enhancement and heterogen eity on dynamic gadolinium chelate-enhanced gradient-recalled echo MR images are the most common features of hepatic metastases from neuroen docrine tumors. The combination of unenhanced spin-echo and dynamic ga dolinium chelate-enhanced gradient-recalled echo MR images allows more accurate characterization of hepatic metastases from neuroendocrine t umors and clearer differentiation from cavernous hemangiomas.