CT evaluation of suspected hepatic metastases: comparison of techniques for i.v. contrast enhancement

Although IV injection of contrast material is widely used for detection and follow-up of hepatic metastases on CT, the optimal method of contrast enhancement has not yet been defined. A prospective study was performed in 50 consecutive patients with suspected hepatic metastases. Lesion size and detectability were compared on unenhanced CT scans, scans obtained during a bolus injection of contrast material (early bolus phase), and scans obtained during a rapid infusion after the loading bolus. A total of 60 hepatic lesions were evaluated in 26 patients, 19 with histologic confirmation of metastases and seven with strong supportive evidence. The bolus phase allowed detection of 15% more lesions than did examination during the rapid-infusion phase. Lesion size varied, depending on the timing and method of contrast administration; the largest measurements were obtained during bolus injection of contrast material. In addition, bolus administration of contrast material subjectively resulted in the best lesion detection. Because the three techniques of IV contrast enhancement may produce different size measurements, sequential examinations must be tailored appropriately. Scanning during the bolus phase is technically possible with current CT equipment and is recommended as the primary CT screening examination for hepatic metastases.