PURPOSE: To investigate whether measurements of hepatic metastases from colorectal carcinoma before contrast material administration are significantly different statistically from measurements after contrast material administration.
MATERIALS AND METHODS: Twenty-four patients with hepatic metastases from colorectal carcinoma underwent spiral computed tomography (CT) with 7-mm collimation. The liver was imaged before and in the portal-dominant phase after intravenous contrast material administration. For each scan, one to three discrete liver lesions were selected for measurement (n = 49). Three experienced radiologists performed independent measurements of the selected lesions on both pre- and postcontrast images at a computer workstation. A three-way analysis of variance (ANOVA) was performed: subjects by raters (the three independent radiologists) by pre- or postcontrast status. The dependent variable was the product of bidimensional measurements.
RESULTS: Sixty-seven percent (33 of 49) of the lesions were measured as larger on precontrast images; 33% (16 of 49), as smaller. There was high interrater reliability, with an intraclass correlation coefficient greater than 0.9.ANOVA showed significant subject, rater, and contrast material effects (P< .001) for the largest lesions in each liver. Contrast material status was a significant factor for all lesion sizes (P < .003).
CONCLUSION: On average, hepatic metastases from colorectal carcinoma are significantly smaller after contrast material administration.