Title:
Viable residual tumor tissue after radiofrequency ablation treatment in hepatocellular carcinoma: evaluation with CT perfusion.

Abstract:
To assess the role of CT perfusion technique in detection of blood flow changes related to the therapeutic effects in HCC lesion treated with RFA.
14 cirrhotic patients with known HCC underwent a perfusion study about 4 months (range 1-13 months) after RFA on a 16-slice MDCT scanner (Brilliance, Philips). Dynamic CT was performed acquiring 8 dynamic slice/scan, after injection of 50 mL of contrast media. In treated lesion, surrounding parenchyma and hypervascular tissue suspicious for residual disease/recurrence, the following perfusion parameters were analyzed: perfusion (P, mL/100 g min); arterial perfusion (AP, mL/min); blood volume (BV, mL/100 mg); hepatic perfusion index (HPI, %), and time to peak (TTP, s). Univariate Wilcoxon signed rank test was used for statistical analysis.
In patients with residual disease (8/14) values of perfusion parameters measured within tumor were: P, median = 45.2; AP, median = 48.2; BV, median = 18.9; HPI, median = 35.8; and TTP, median = 19.4. The values calculated in ablated area were: P, median = 10.9; AP, median = 9.6; BV, median = 5.5; HPI, median = 14.6; TTP, median = 39.6. The parameters calculated in the surrounding parenchyma were: P, median = 15.8; AP, median = 14.2; BV, median = 12.0; HPI, median = 17.9; TTP, median = 43.2. A significant difference (P < 0.05) was observed in mean values of P, AP, and HPI, calculated between treated lesions with residual tumor and those successfully treated.
Perfusion CT enables assessment of HCC vascularity after RFA treatment, by adding quantitative information about the presence of residual arterial vessels within the viable residual neoplastic tissue.