[Delayed CT--a technique for the detection of hepatic metastases]

Plain CT and subsequent dynamic (or enhanced) CT demonstrated liver tumors in 43 patients: hepatocellular carcinoma in 24 patients, metastatic liver tumors in 15 patients and hemangioma of the liver in 4 patients. Delayed CT was furthermore performed 4 hours later to investigate its significance in the diagnosis of hepatic metastases by primarily comparing it with plain CT. The difference in CT numbers between the lesion and the normal hepatic parenchyma at delayed-type scanning 31.48 +/- 7.41 HU in metastatic liver tumors, which was significantly higher than 17.37 +/- 11.32 HU in hepatocellular carcinoma (p < 0.001). TDI after delayed CT was -0.43 +/- 0.13 in metastatic liver tumors and -0.26 +/- 0.15 in hepatocellular carcinoma, between which a significant difference was noted (p < 0.01). Delayed CT presented similar images to those obtained from plain CT in 14 of the 24 patients with hepatocellular carcinoma (58.3%) and a less clear tumor boundary in the remaining 10 patients (41.7%). On the other hand, the tumor boundary became clearer in 12 of the 15 patients with metastatic liver tumors (80.0%) at delayed-type scanning, than after plain CT, although the images remained almost unchanged in the remaining 3 patients (20.0%). The findings obtained from delayed CT in hemangioma of the liver were little different from those obtained from plain CT. This study suggested that delayed CT might better detect metastatic liver tumors than could plain CT. Delayed CT is recommended when metastases from other organs to the liver are suspected, and particularly when such metastatic liver tumors are small in size and multiple.