Contrast-enhanced spiral CT of the liver: Effect of injection time on time to peak hepatic enhancement

Purpose: On contrast-enhanced hepatic CT, maximum tumor detection of liver metastases from colorectal cancer is achieved at peak hepatic enhancement. We investigated the relationship between injection time of contrast medium and time to peak hepatic enhancement (TPHE) after the end of injection. Method: One hundred nineteen patients without a cardiovascular disorder were enrolled in this study. Before the spiral CT was performed, a small amount of contrast medium was injected and a single level dynamic CT was performed to evaluate aortic enhancement and to determine the scan start time of the spiral examination. Patients were divided into three groups; contrast medium was injected over 30 s in 40 patients (Group A), 45 s in 39 patients (Group B), and 60 s in 40 patients (Group C). The TPHE after the end of injection was measured, and the difference among the groups was compared using one-way analysis of variance. A p value of <0.05 was considered a statistically significant difference. Results: The TPHEs of the groups were 25.3 +/- 4.6 s (Group A), 27.0 +/- 5.8 s (Group B), and 24.4 +/- 4.6 s (Group C) and were similar in value. No statistically significant difference was observed (p = 0.067). Conclusion: Hepatic enhancement reaches its peak at similar to 25 s after the end of contrast medium injection irrespective of injection time.