摘要OBJECTIVE CT scans have become a conventional examination for hepato cellular carcinoma. Computed tomography arteriography (CTA) and computed tomography arterial portography (CTAP) are more sensitive. In this investigation, we defined the optimal time of CTA and CTAP during a dynamic scan.METHODS CTAP: a 5-F Yashiro catheter was inserted to the superior mesentery artery under DSA, and the whole liver scanned 6 s after contrast medium injection. CTA: the 5-F Yashiro was insertedto the proper hepatic artery and a scan of the whole liver was performed 6-8 s after contrast medium injection.RESULTS In CTA, the contrast between enhancement of liver cancer and the normal liver tissue reached a peak after the contrast medium had been injected for 6～8 s. The focus was concealed by non-pathological enhancement in three cases. When the scan was delayed to 30 s after injection, the lesion could be detected clearly (P ＜0.05). The contrast of the image was not as good as 60～180 s after injection, and pathological enhancement also was not found (P ＞0.05). During CTAP, the frequency of an abnorminal non-perfusion area was 19.0% (4/21) at 6-8 s after injection; the contrast of low-perfusion focus and the normal liver was evident and the lesion could be detected clearly (P ＜0.01). The contrast was decreased at 120-180 s after injection and the image was not as clear (P ＞0.05).CONCLUSION CTA and CATP are effective techniques to detect small hepatocellular carcinoma, to define the position of lesions and to estimate the feasibility of resection.