Triphasic Spiral CT of the liver: Enhancement patterns of noncystic focal lesions.

Purpose: The purpose of this study was to investigate if Triphasic Spiral CT (arterial, portal and equilibrium phases) can improve the characterization of noncystic focal lesions. Material and methods: Sixty-six patients with suspected focal liver disease underwent Triphasic Spiral CT. After the injection of 120-140 ml contrast material at 3 ml/s the liver was imaged in the arterial (scanning delay: 20-27 s), portal (scanning delay: 45-80 s) and equilibrium (scanning delay: 5-8 min) phases. The enhancement of each lesion was evaluated in each phase and the lesions were grouped by enhancement pattern (11 patterns in all). The reference standards in our 66 patients were surgery (12), biopsy (43), MRI (9), follow-up (9), somatostatin receptor scintigraphy (6). Results: One hundred and twenty-six liver lesions were detected in 66 patients, four of 11 enhancement patterns (hypo/hyper/hyper, hyper/iso/iso, hyper/hyper/iso, hyper/hyper/hyper) were always referrable to benign disease (hemangioma, focal nodular hyperplasia-FNH-adenoma). Four of 11 enhancement patterns (iso/hypo/hypo, iso/iso/hypo, hyper/hypo/hypo, hyper/hyper/hypo) were always referrable to malignant disease (hepatocellular carcinoma-HCC-metastases). The other two patterns (hypo/hypo/hypo, hypo/hypo/hyper) were seen in both benign and malignant diseases. Conclusions: Triphasic Spiral CT improves the characterization of HCC, FNH, adenoma and hemangioma. The arterial and the equilibrium phases add no information to the yield of the portal venous phase in metastases, except for those from pancreas neuroendocrine tumors in the arterial phase. In our experience, patients with unclassified lesions at US or conventional CT, suspected HCC and metastases from pancreas neuroendocrine tumors should be submitted to Triphasic CT of the liver. This technique however does not appear to be indicated in the study of liver metastases from hypovascular tumors, while it improves the detection of FNH and adenoma.