Hepatic CT enhancement. Part I. Alterations in the volume of contrast material within the same patients.

PURPOSE

To evaluate the effects of alterations in the volume of contrast material on liver enhancement.

MATERIALS AND METHODS

Thirty patients underwent repeat computed tomographic (CT) examinations within 6 months, the first with either 100, 150, or 180 mL of nonionic contrast material (2 mL/sec). In the second, only volume was altered. Liver attenuation was measured before and after contrast material administration, and enhancement was calculated for each image. Comparisons were made only within the same patients.

RESULTS

Mean liver enhancement was greater with 150 mL compared with 100 mL beyond 55 seconds after injection. Mean peak enhancement was greater by 21 HU with 150 mL; mean time to peak enhancement was longer by 14 seconds. Mean liver enhancement was greater with 180 mL compared with 150 mL at all intervals beyond 80 seconds. Mean peak enhancement was greater by 22 HU; mean time to peak liver enhancement was longer by 24 seconds.

CONCLUSION

Alterations in contrast material volume have substantial impact on liver enhancement and potentially tumor conspicuity. The optimal window of time for liver imaging after contrast material injection varies with the volume administered.