Optimal scan timing for coronal enhancement of hypervascular hepatocellular carcinomas and correlation with tumor size: evaluation with four-phase CT hepatic arteriography.

PURPOSE: Our aim was to evaluate coronal enhancement of hypervascular hepatocellular carcinomas (HCCs) on four-phase CT hepatic arteriography (CTHA). MATERIALS AND METHODS: This study included a total of 86 hypervascular HCCs. Four-phase CTHA images were acquired at 10 sec, 35 sec, 60 sec, and 85 sec after the initiation of contrast medium injection. The rate of coronal enhancement on each phase of CTHA of HCCs was analyzed. The rate of coronal enhancement on each phase of CTHA of HCC was also compared with nodule size. RESULTS: All HCCs showed tumor enhancement on phase-one CTHA. The appearance rates of coronal enhancement on phases-two, -three, and -four CTHA were 87.2%, 67.4%, and 53.4%, respectively. The appearance rates of coronal enhancement of small HCCs on phases-two, -three, and -four CTHA were 91.1%, 53.6%, and 30.5%, respectively; those of non-small HCCs were 80.0%, 93.3%, and 96.7%, respectively. On phase-two CTHA, the presence of coronal enhancement was higher in small HCCs than in non-small HCCs. On phases-three and -four CTHA, the presence of coronal enhancement was significantly higher in non-small HCCs than in small HCCs. CONCLUSION: The optimal phase for achieving coronal enhancement depended on tumor size.