Methodological assessment of combined spiral CT angiography and CT arterial portography

Background: To assess an optimal methodology of combined spiral computed tomographic (CT) angiography (CTA) and CT arterial portography (CTAP) for detection and characterization of liver tumors. Methods: We performed spiral CTAP only in five patients with 30-32% contrast (subset A), CTAP combined with preceding spiral CTA using 30-32% contrast in 19 (subset B), and CTAP combined with preceding spiral CTA with 60-64% contrast in seven (subset C). The CT numbers of the aorta immediately before preceding CTA and subsequent CTAP and the CT numbers of malignant tumor and liver parenchyma with CTAP were measured. Results: The differences of the CT number between the malignant tumor and liver parenchyma on CTAP were 61.1-161.8 (mean +/- SD, 114.5 +/- 39.3) HU, 50.7-164.8 (104.2 +/- 31.2) HU, and 101.2-368.3 (219.5 +/- 90.5) HU in subsets A, B, and C, respectively. Two cavernous hemangiomas showed pathognomonic findings with preceding CTA. Conclusion: Combination of preceding spiral CTA and subsequent spiral CTAP using 30% contrast with a 5-min interval is an optimal method for detection and characterization of liver tumors.