【Objective】 To evaluate the use of navigation and navigation assisted contrast-enhanced ultrasound (CEUS) in ablation of hepatocellular carcinoma (HCC) invisible in B-mode ultrasound. 【Methods】 Forty-two HCC lesions in 34 patients were enrolled

and all the lesions were diagnosed by CT/MR but invisible in B-mode ultrasound. Eight of the patients had elevated serum AFP. Under general anesthesia

after image fusion between the ultrasound and CT/MR

the navigation system could decide the location and boundary of the HCC in ultrasound image. Radiofrequency ablation (RFA) guided by navigation was applied. By fusing the CT/MR image before RFA with CEUS after RFA

navigation assisted CEUS was employed right after ablation to decide whether the area of ablative zone had covered the whole HCC. Additional puncture was applied if ablative zone had not completely covered the HCC. All the patients received CT/MR one month after ablation to decide whether the HCC had been completely ablated. 【Results】 The image fusion was successfully applied in all 42 HCCs

and on average

8.5 min (5~20 min) was spent in image fusion. Six HCCS (6/42

14.3%) received extra 1 to 2 punctures after navigation assisted CEUS. Haemothorax was found in one patient one day after RFA. Catheter was applied for drainage and was removed after ultrasound revealed no fluid in the chest cavity 4 days later. Twelve patients had asymptomatic pleural effusion or ascites after ablation which disappeared in 1 to 2 weeks. One month after RFA

CT/MR showed that all the HCCs had been completely ablated

and the elevated serum AFP in the 8 patients all fell into normal range. 【Conclusions】 Navigation and navigation assisted CEUS could successfully ablate HCC invisible in B-mode ultrasound.