[Differential diagnosis of focal liver lesions with MRI using the superparamagnetic contrast medium endorem]

In a phase III/III-B trial the specific contrast enhancement of benign liver tumors, especially FNH and adenoma, versus malignant liver tumors such as HCC and metastases (colorectal and endocrine tumors) was evaluated using the superparamagnetic iron oxide ENDOREM.

57 patients were prospectively investigated using T2-(TR/TE=2000/90) and T1-(550/15) weighted spinecho (SE), FLASH-2D-gradientecho (GE), and fat suppressed (FATSAT) sequences before and after administration of ENDOREM (concentration: 0.2 mmol Fe/ml, dose: 15 micromol/kg (b.w.) in transverse slice orientation on a 1.5 Tesla MAGNETOM (Siemens, 63 SP). In 8 patients an in vivo-in vitro correlation 30 minutes after resection was performed. In 12 patients benign primary liver tumors (FNH (n = 10), adenoma (n = 1), and hemangioma (n = 1) were histopathologically proved. Malignant liver tumors (HCC (n = 11, cholangiocarcinoma (n = 1), metastases from colorectal carcinoma (n = 13), and endocrine tumors (n = 4)) were found in 29 patients. 11 patients with liver cirrhosis due to Wilson's disease and 5 with cirrhosis due to other reasons were investigated.

Contrast-enhanced studies allowed detection of more lesions in 19 of 41 patients with liver tumors. Benign liver tumors showed significant loss of signal intensity of 43.0% +/- 17.9 for FNH, 32.4% for adenoma and 10.2% for hemangioma in proton density-weighted SE images. Malignant tumors showed only minimal signal loss: HCC: 5.3% +/- 17, cholangiocarcinoma: -1.6%, colorectal: -2.0% +/- 11.1, endocrine metastases: 4.2% +/-4.1. Normal liver parenchyma and spleen tissue demonstrated significant signal loss of 59.2% +/- 14.9 and 42.3 +/- 012.5. In ten patients and 13 lesions of FNH, a capsule was seen in 7.7% plain and 23.1% enhanced. Scar tissue was found in 30.8% plain, 84.6% enhanced. In the patient with adenoma, capsule with contrast enhancement was seen, but no scar was detected, whereas in patients with HCC a capsule was seen in three cases enhanced. Statistical analysis (Friedman-test, Wilcoxon-test) showed a statistically significant difference in signal loss between benign and malignant liver lesions (p < 0.05).

The use of superparamagnetic iron oxide ENDOREM) allows differentiation of benign and malignant liver tumors on the basis of contrast enhancement, existence and specific enhancement of capsule or scar. In vitro correlation show some limitations of in vivo MRI.