Assessment of Neoplastic Angiogenesis Using Perfusion-Weighted MR Imaging: Experimental Study in VX2 Carcinoma in Rabbits

Yoon, Woong; Kang, Heoung Keun; Park, Jin Gyoon; Kim, Jae Kyu; Seo, Jeong Jin; Kim, Yun Hyun; Jeong, Yong Yeon; Chung, Tae Woong

Abstract

PURPOSE: To evaluate the perfusion-weighted MR imaging findings of hepatic VX2 carcinoma in rabbits and to explain the perfusion characteristics of this condition by correlation with the histopathological findings.
MATERIALS AND METHODS
Twelve New Zealand white rabbits, each weighing between 2.5 and 3.5 (mean) 3.1kg, were used in this study. Perfusion MRI using single-shot gradient-echo EPI was performed 7 -21 days after the injection of tumor cell suspension into the hepatic parenchyma by laparotomy. On the basis of the calculated enhancement ratio, the time-intensity perfusion curves for VX2 tumor and normal liver parenchyma were created, and the shapes of these curves, the time to maximum SI decrease, and the maximum enhancement ratio in each, were evaluated. To assess microvessel density in each VX2 carcinoma and in normal liver parenchyma, immunohistochenical study using factor VIII-related antigen was performed.
RESULTS
A total of 15 tumors 1 -3 cm in diameter were revealed by MR imaging. The perfusion curve showed rapid decrement and immediate recovery of the signal intensity of VX2 carcinoma during the early arterial perfusion phase and slower decrement and gradual recovery of that of normal liver parenchyma during the late portal perfusion phase. In all cases, these were constant findings. The time to maximum signal intensity decrease was 13 -16 (mean, 15) secs in VX2 carcinoma and 28 -36 (mean, 32) secs in normal liver parenchyma (p<0.01). The maximum enhancement ratio of VX2 carcinoma and normal liver ranged from 27 to 84% (mean 47%) and from 36 to 82% (mean, 56%), respectively. Immunohistochemical study showed that the MVD of VX2 carcinoma was significantly greater than that of normal liver parenchyma(75 vs 17, p<0.01).
CONCLUSION
Perfusion-weighted MR imaging appears to be a useful tool for the diagnosis of neoplastic angio-genesis, and thus holds promise differentiating liver tumors.