Detection of Liver Metastases: Usefulness of Dynamic Spiral CT during the Portal Phase with a Higher IV Injection Rate of Contrast Material

Jeong, Youn Sin; Cho, June Sik; Youn, Wan Gyu; Ahn, Young Jun; Choi, Chang Lak; Lee, Young Hwan

Abstract

PURPOSE
To evaluate the usefulness of dynamic spiral computed tomography(CT) during the portal phase with ahigher IV injection rate of contrast material in detecting hepatic metastases.
MATERIALS AND METHODS
We reviewed two-phase dynamic spiral CT in 44 patients with hepatic metastases of pathologically proven primary malignancy. One hundred and fifty ml. of non-ionic contrast material was administered with a power injector at a rate of 5ml/sec., and two-phase images at 55-80 sec.(portal phase) and 2-5 min.(equilibrium phase) were obtained after thestart of bolus injection. Two phase images were compared for detectability of hepatic metastases according tosize, number and enhancement pattern.
RESULTS
In cases of metastases less than 1cm, 113 lesions(100%) that showed clearly defined hypodense lesions were detected in the portal phase of dynamic CT. However, the equilibriumphase images showed hypodense lesions in 58 cases(51%) and isodense lesions in 55cases(49%). In cases of metastases 1-2cm in size, the portal phase images detected 70 hypodense lesions(92%) and six hyperdense lesions(8%). In the equilibrium phase, however, the lesions were hypodense in 54 cases(71%), hyperdense infour(5%), and isodense in 18(24%). In cases of metastases larger than 2 cm, portal phase images showed 29 hypodense lesions(97%) and one hyperdense lesion(3%). In the equilibrium phase, however, the lesions were hypodense in 25 cases(83%), hyperdense in two(7%), and mixed in three(10%). As compared with the portal phase, most metastatic lesions were detected as poorly defined hypodense or isodense lesions in the equilibrium phase and decrease in size due to peripheral enhancement.
CONCLUSION
Dynamic spiral CT during the portal phase with a higher IV injection rate(5 ml/sec) of contrast material is a useful method for detecting hepatic metastases, especially small lesions less than 1cm.