Diagnostic Accuracy of Spiral CT in Detecting Hepatic Tumors: Evaluation Using Portogenously Implanted Hepatic VX-2 Carcinoma in Rabbit

Kim, Yang Min; Jung, Jin Wook; Joh, Joon Hee; Cha, Sang Hoon; Park, Kil Sun

Abstract

PURPOSE: To assess, by means of CT-pathologic correlation, the ability of CT to detect hepatic VX-2 carcinomas in rabbits, and to determine the factors influencing the sensitivity of tumor detection.
MATERIALS AND METHODS
By means of direct portal inoculation, VX-2 carcinomas were implanted in the liver of eight rabbits after laparotomy. Two weeks later, dual-phase spiral CT scanning was performed using scan parameters of 3-mm collimation and reconstruction intervals of 1 mm and 3 mm. Radiologic-pathologic correlation involved the comparison of CT images and pathologic slices. The sensitivity and positive predictive value with which each technique detected the presence of tumors were calculated.
RESULTS
Using pathologic slices, 2-40 (mean, 9.1) mm in size, 65 tumor nodules were detected. Overall sensitivity and the positive predictive value were 63% and 73%, respectively. Sensitivities for tumors of 2-5 mm and 6-10 mm were 28% and 79%, respectively. For images reconstructed with a 1-mm interval, sensitivity was significantly higher than that where a 3-mm interval was used (79% vs. 46%), but sensitivities for arterial and portal-phase imaging were not significantly different. Among small tumors (< or = 10 mm), 63% (12/19) showed strong enhancement at arterial-phase imaging. Regarding tumor detection, inter-observer concordance between the three radiologists was excellent for portal-phase images (k=0.86 and 0.83 for 1 mm and 3 mm reconstruction intervals, respectively), and good for arterial-phase images (k=0.77 and 0.73 for 1 mm and 3 mm reconstruction intervals, respectively.
CONCLUSION
Even where dual-phase scanning with 3-mm collimation is used, spiral CT is limited in its ability to detect tumors 5 mm or less in diameter, though overlapping reconstruction improves the sensitivity with which those of 6-10 mm are detected. In the evaluation of arterial-phase images obtained at contrast-enhanced dual-phase imaging, special attention should be given to small hyper-attenuating nodules.