To investigate whether measurements of hepatic metastases before contrast administration are different from measuments after contrast administration. And to gain more effective follow up method by analyzing the difference of contrast between pre- and postcontrast scans.

Thirty patients with herpatic metastases were underwent conventional CT. Continuous 10mm thick slices were obtained from liver dome to pelvic inlet, then the patients received IV injection of contrast material, and same method as precontrast CT scan was performed. Additional 5mm thin slice scan was obtained in case of need. Three radiologists performed independent bidimensional measurements of the randomly selected lesion on both pre- and postcontrast images at the same level and analyzed the difference of the size and contrast.

The size of hepatic metastases were measured as smaller on postcontrast images ; average 41.4±43.5cm² on precontrast scan & 35.2±37.5cm² on postcontrast scan. There was significant difference by paired t-test(p<0.02). 24 of 30 cases(80%) showed better conspicuity on postcontrast images, 5(16.7%), on precontrast images and 1(3.3%) showed similiar conspicuity on both pre- and postcontrast images. The contrast of hepatic metastases was significantly higher on postcontrast scan by chi-square test(p<0.01).

Hepatic metastases are significantly smaller on postcontrast images. The contrast between metastatic lesion & liver parenchyme was better on postcontrast scan. Therefore, serial assessment of hepatic metastases size by CT should not be compared mixed pre- and postcontrast image. And postcontrast scan is more effective method than precontrast for follow up of hepatic metastasis.