Background: Ultrasound is the most common imaging modality used to guide electrode insertion and estimate the necrotic zone during radio frequency ablation (RFA) of hepatic tumors . However most investigators agree that ultrasound inaccurately predicts the necrotic zone after RFA despite the scarcity of experimental and clinical evidence .Objective: We aimed to compare the necrotic diameter estimated from ultrasound during RFA with the actual gross diameter in ex vivo porcine livers .Methods: An internally-cooled with a 3cm uninsulated tip (Cooltip Radiofrequency System, Valleylab) was used to perform RFA for 6 and 12 minutes in ex vivo porcine livers under ultrasound guidance . Maximum horizontal and longitudinal diameters of the gross ablation zones were compared with the diameters of the hyperechoic zone created on ultrasound during RFA.Results: There was a trend for increased horizontal diameter for both ultrasound (RFA 6 mins =3.8+/- 0.5 vs. RFA 12 mins =5.1+/- 1.0cm; p=0.079 ) and grossly (RFA 6 mins =2.7+/- 0.27 vs. RFA 12 mins =3.1+/- 0.24 cm; p=0.068 ) with increased RFA duration from 6 to 12 minutes , which was not observed for the longitudinal diameter . Ultrasound consistently overestimated the actual necrotic diameter by 1.3 + 0.8cm ( range= 0.4 to 3.6cm ) ( p=0.01) wether RFA was performed for 6 ( 1.0+/- 0.3cm) or 12 ( 1.+/-1.2cm) minutes Conclusion: Ultrasound led to overestimation of the true size of ablation zones regardless of the duration of the duration of ablation . The slight increae in the discrepancy with increased RFA duration suggests that an increased hyperechoic zone with prolonged ablation will not necessarily mean a proportionate increase in actual necrotic diameter.
Hepatocellular Carcinoma ; Radio Frequency Ablation (rfa) ; U Hepatoma ; Hcc